Robert Mayer and the Conservation of Energy 9781400872817

Table of contents :
Cover
Contents
Acknowledgments
Author's Note
Introduction
Part I : The Man and His Work
1 Mayer the Person
2 Mayer's Work
Part II: Establishing the Relevant Context
3 Physiology and Medicine
4 Physics and Chemistry
5 Science Circumscribed
Part III: Mayer's Work in Context
6 A Contextual Reconstruction of the Development of Mayer's Ideas
7 Mayer and Naturphilosophie
8 Assessment and Conclusions
Appendix 1 Timeline of Robert Mayer's Life and Work
Appendix 2 Courses Mayer Took at the University of Tübingen, 1832-37
Appendix 3 The German Text of the Longer Passages Quoted from Manuscript
Notes
Bibliography
Index

Citation preview

Robert M ayer and th e C onservation of Energy

Robert Mayer and the Conservation of Energy

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K E N N E T H L. CA N E V A

P R I N C E T O N

U N I V E R S I T Y

P R I N C E T O N ,

N E W

P R E S S

J E R S E Y

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C o p y rig h t © 1993 by P rin c e to n U niversity Press P u b lish ed by P rin c e to n U niversity Press, 41 W illiam S tre et, P rin c e to n , N ew Jersey 08540 In th e U n ite d K ingdom : P rin c e to n U niversity Press, C h ic h e ste r, W e s t Sussex All R ights R eserved

Library o f C ongress C a ta lo g in g -in -P u b lic a tio n D ata C a n ev a, K e n n e th L. R o b e rt M ayer a n d th e C o n serv atio n of E nergy / K e n n e th L. C an ev a. p.

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In clu d es b ib lio g rap h ica l references an d index. ISB N 0-69I-08758-X I Force a n d energy— H istory. 1 814-1878.

2. M ayer, Julius R o b e rt von,

3. P hysicists— G erm an y — B iography

Q C 7 3 .8 .C 6 C 3 6

1993

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I. T itle

92-25400

T h is b o o h has b e e n co m p o sed in BT T ran sitio n a l 521 P rin c eto n U niversity Press books are p rin te d on acid-free paper, a n d m e e t th e guidelines for p e rm a n e n c e a n d d u ra b ility of th e C o m m itte e on P ro d u c tio n G u id e lin e s for Book L ongevity o f th e C o u n c il on L ibrary R esources P rin te d in th e U n ite d S ta te s of A m erica 1

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A C K N O W LED G M E N TS

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A U TH O R’S NOTE

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IN TR O D U C TIO N

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P A R T I: T H E M A N A N D H IS W O R K

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CHAPTER ONE

M a y e r t h e P e rs o n 1 2 3 4 5

M ayer's M ayer’s M ayer’s M ayer's M ayer's

3 Upbringing and Education Voyage to the D utch E ast Indies Religiosity Circle o f Friends Character

3 7 8 14 16

CHAPTER T W O

M a y e r's W o r k

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1 M ayer’s Earliest Presentation o f His Ideas

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1.1 “O n th e Q u a n tita tiv e an d Q ualitative D eterm in atio n of Forces” 1.2 “Rem arks on th e FoTces of In an im ate N atu re” 2 T he Leading Ideas and Peculiarities o f M ayer’s Work

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2.1 Force 2.1.1 T h eA nalog yw ith M a tter

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2.1.2 The Centrality of Heat and Motion

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2.1.3 The Nature o f Heat (in Particular) and Force (in General) 2.1A The Status o f Imponderables; Forces as Objects

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2.2 N eu tralizatio n of D ifferences: T h e C o n tin u e d Im p o rtan ce of C hem ical A nalogs 2.3 C ausality and th e Laws of T h o u g h t 2.4 Q u an titativ e T hin k in g an d th e M easure of th e Equivalence

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of H eat and M o tio n 2.5 T h e M easure of Force

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2.5.1 Q uantity o f Motion vs. Vis Viva 2.5.2 The Parallelogram o f Forces and Central-Force Motions

2.6 M ayer’s R estriction of His Ideas to In an im ate N atu re an d His Allowance for th e C reation of Force O u t of N oth in g 2.7 Force as an A n tid o te to M aterialism 2.8 T h e Search for Valid Analogies

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P A R T II: E S T A B L IS H IN G T H E R E L E V A N T C O N T E X T

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CHAPTER THREE

P h y sio lo g y a n d M e d ic in e 1 Blood, Respiration, and A nim al H eat 2 Sources o f Organic A ctivity

49 49 68

2.1 Physical and C hem ical Processes: T h e O rganism ’s C o n n ectio n w ith th e E xternal W orld 2.2 Vital Forces and th e Soul: T he O rganism ’s Internal Sources of Activity 3 Leading Analogies

79 125

3.1 T h e R elationship betw een th e Im ponderables, Vital Force, and th e Soul 3.2 O rg a n ism sasM a ch in es 3.3 T h e Solar System as a Living O rganism 4 Physiology as an O pponent o f M aterialism

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5 H om eopathy 6 Sum m ary

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P h y s ic s a n d C h e m is try

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1 Force

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I . I T h e Parallelogram of Forces and C entral-Force M otion 1.2 Catalytic, C o n tact, and E lectrochem ical Forces 2 Imponderables and the Nature o f H eat

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2.1 T herm al Expansion of Gases and R elated P h enom ena 3 M atter 4 M etamorphosis, Neutralization, and Indifference: The Chem ical and Physical C ontexts 5 Sum m ary

192 194 198 202

CHAPTER FIVE

S c ie n c e C irc u m s c rib e d 1 The Nature and Scope o f Science 2 R elig io n a n d S p iritu a lism 3 Sum m ary P A R T I Ih M A Y E R ’S W O R K IN C O N T E X T

207 208 219 229 231

CHAPTER SIX

A C o n te x tu a l R e c o n s tr u c tio n o f th e D e v e lo p m e n t o f M a y e r ’s Id e a s 1 Through the Publication o f H is 1842 Paper 2 Later Developments and Changing Emphases

233 235 259

CHAPTER SEVEN

M ayer an d N atu rp h ilo so p h ie 1 The Leading Characteristics of Naturphilosophie 2 Force a nd Forces in Naturphilosophie 2.1 Vital Force 3 Respiration and A nim al H eat 4 Echoes o f NaturphiIosophie in M ayer's Work?

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CHAPTER EIGHT

A ssessm ent and C onclusions

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APPENDIX ONE

T im eline of R obert M ayer’s Life and W ork

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APPENDIX TW O

C ourses M ayer Took at th e University of T ub in g en , 1832-37

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APPENDIX THREE

T h e G erm an Text of th e Longer Passages Q u o ted from M anuscript

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N O TE S

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BIBLIOGRAPHY

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INDEX

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and w riting for this book would n o t have been possible w ith o u t th e generous su p p o rt of the N ational Science F oundation and th e University of N orth C arolina at G reensboro. A Research A ssignm ent from U N C G supported m e dur­ ing th e fall sem ester of 1986 while I lived and did research in th e Boston area; a first N SF grant (SES-8618404) funded my research there and for a m o n th in G erm any d uring th e first half of 1987.1 am especially grateful to my colleagues in the History of Science D e p artm en t at H arvard who arranged for m e to be a Visit­ ing Scholar th ere for a year; it was a pleasure to b e able to take part in som e of the d e p a rtm e n t’s active scholarly life, as it was a privilege to work in th e m any H arvard libraries. A second N S F grant (SES-8722018), reinforced by a second U N C G Re­ search A ssignm ent, allowed m e to devote the academ ic year 1988-89 to writing. I am also grateful to M ary Ellen Bowden and th e N ational F oundation for the History of C h em istry for a travel g rant th a t allowed m e to work in Philadelphia libraries for a few days in M arch 1990. W orking for a m o n th in G erm an archives and libraries was a joy n o t only b e ­ cause of th e sources m ade available to m e, b u t also because of th e unfailing com ­ petence and kindness of everyone I d ealt w ith. I owe a special d eb t of g ra titu d e to Dr. H elm u t Schm olz, director of the S tadtarchiv H eilbronn, w hich houses th e bulk of M ayer’s surviving m anuscripts, and to Dr. Volker Schafer, director of the U niversitatsarchiv T ubingen, who also m ade inquiries for m e concerning th e pri­ vately held G m elin Nachlass and who generously co n tin u ed to answ er a n u m b er of research qu estio ns for m e after f had retu rn ed to th e U nited S tates. Hans Gobbel, director of th e K ernerhaus m u seu m and archives in W einsberg, kindly searched th eir holdings for anything concerning Mayer. T he following in stitu tio n s generously m ade available and gave th e ir perm ission to q u o te from m anuscripts in th eir possession: S tadtarchiv H eilbronn, Universitatsarchiv T iibingen, Staatsarchiv Ludwigsburg, Royal In stitu tio n of G reat Britain (by courtesy of th e D irector), D eutsches Literaturarchiv/Schiller-N ationalm useum , Bayerische S taatsbibliothek, and S taatsbibliothek Preussischer K ulturbesitz. My thanks, too, to a n u m b er of in stitu tio n s th a t sen t copies of m anuscript m ateri­ als I did n o t u ltim ately use: S m ithsonian In stitu tio n (Special C ollections Branch), U niversitatsbibliothek H eidelberg, U niversitatsbibliothek T iibingen, G esellschaft L iebig-M useum , D eutsches M useum , an d G erm anisches N ationalm useum . Sev­ eral in stitu tio n s eith er answered inquiries or supplied o th er m aterials: Universitatsbibliothek Augsburg, U niversitatsbibliothek G iessen, R ijksuniversiteit U trecht (B ibliotheek), Koninklijke Bibliotheek (T he H ague), C olum bia U niver­ sity Libraries, M assachusetts In stitu te of Technology Libraries, C e n te r for History of Physics, an d Virginia H istorical Society. I am particularly grateful to th e S taats­ bibliothek Preussischer K ulturbesitz, H andschriftenabteilung, Z entralkartei der A utographen, for answ ering my inquiries concerning m anuscript holdings in GerT he research

m an libraries. A n u m b er of individuals were also kind enough to procure ph o to ­ copies for m e of hard-to-find item s: Jodi Bilinkoff, M ark Finlay, O tto-Joachim Griisser, Rich Kremer, John N eu, Richard W olfe, and Bill W oodw ard. Finally, my thanks to Gaylor C allahan, h ead of U N C G ’s interlibrary loan d ep artm en t, for helping m e to o btain a large num ber of books and articles essential to my re­ search. To Toni Fields of U N C G I am in d eb ted for th e m ap and diagrams. T hree colleagues— Larry Holm es, Kathy Olesko, and Steve Turner— gave gen­ erously of th eir tim e to read and com m ent upon an earlier version of this work, for w hich I am very grateful. Steve’s ten-page critique, in particular, was encouraging even while it m ade num erous general an d specific suggestions for revision. An anonym ous reviewer for P rinceton University Press was also b o th encouraging and helpfully critical. I ask their indulgence if th e present work does n o t answer all of th eir desiderata. I h ad hoped to supply b o th a critical bibliographical essay and a m ore extensive resum e of th e historiography concerning th e discovery of the prin­ ciple of th e conservation of energy, b u t in the end decided th a t I preferred not to postpone com pletion of th e m anuscript for th e n o t inconsiderable nu m b er of m o n th s th a t it would have taken to research and write them . I am grateful to my skillful an d conscientious editor at Princeton University Press, Alice Calaprice, for n u m erous stylistic im provem ents, for saving m e from a num ber of em barrassing errors, and for lettin g m e keep a few cherished peculiarities. Last— and no one will think least— I th an k Jane for love and undim inished faith du rin g th e Era of th e Book, now happily beh in d us.

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A FEW COMMENTS on conventions m ay be in order. In direct q u o tatio n s I have always kept th e original wording, spelling, p u n ctu atio n , an d italicizing, except th a t I have n o t italicized proper nam es w hich in th e G erm an original were as a m atter of typographical convention italicized or p rin ted in all capital letters, and I have usually silently o m itte d internal page or section references. Individual G er­ m an words q u o te d in isolation from th eir G erm an gram m atical context have usu­ ally b een reduced to a sim pler form , for exam ple nouns to th e nom inative case, adjectives to th eir uninflected form, and verbs to th e infinitive or to a m ore com ­ pact form (as “s c h r e ite t. . . fort” to [fortschreitet]). In d e n te d q u o tatio n s show (by in d en tin g or n o t in d en tin g th e first line) w hether or n o t th e passage began a paragraph. O m ission of tex t from th e beginning of th e first sentence is signaled by a lower-cased (or bracketed upper-cased) first word; om ission of text from th e end of th e last sen ten ce is n o t shown. S horter quo tatio n s incorporated in to my text n eith er preserve initial capitalization nor indicate initial or final om issions, al­ th o u g h internal om issions are always noted. If a period directly follows th e last word before an ellipsis, th e n th e previous sentence ended there; if there is a space b etw een th e last word and th e first period of th e ellipsis, th e n a portion of the previous sen ten ce has been om itted . If an in d en ted q u o te is treated as g ram m ati­ cally part of th e sentence of my tex t th a t introduces it, its en d n o te applies also to any q u o ted passages in th a t introductory sentence. I have used th e custom ary double q u o tatio n m arks to d en o te actual quo tatio n s, single marks (a.k.a. 'inverted co m m as’) to call a tte n tio n to words I have used in som e qualified sense. T ranslations are m y own except where otherw ise noted. I th an k Joachim Baer for conferring w ith m e over some especially difficult G erm an passages. Since I have italicized foreign-Ianguage words q u o ted w ithin brackets in a portion of translated text, words th a t were originally already in italics (or p rinted in Sperrdruck) have in addition also b een underlined. M y translations te n d tow ard the literal, th o u g h I have striven to m ake th em readable as English as well. T hus I have rendered "to d te N a tu r” as “dead n atu re ,” even th o u g h we m ight m ore usually say som eth ing like “th e inorganic w orld,” and th e translations have m ore so’s, thereby’s, and com plexities of style th a n is norm al in English. I have chosen not to lard th e q u o ted passages w ith a plethora of words in square brackets added to flesh o u t th e English translation— for exam ple, stylistic a n d ’s an d th e ’s, pro­ nouns replaced by th eir an teced en ts (where th e G erm an was clear and th e English would n o t b e), verbs w hich the G erm an construction clearly distributes across several phrases b u t which one w ould norm ally repeat in English, an d th e like. In th e notes and bibliography an equals sign (= ) connects sources th a t are identical except for possible insignificant variations in spelling and p unctuation; an ‘approxim ately equals' sign (~) m eans th a t there are som e differences in w ord­ ing of w hat is essentially still th e sam e text. Unless otherw ise specified, it can be

assum ed th at all letters cited in the notes are either to or from Mayer. Johannes M uller is cited in the notes simply as “Muller." T he annotation “in M ayer’s library” in the bibliograpahy refers to the “Verzeichnis der H andbticherei Robert M ayers” in Krusemarck 1942, 78-81; vol­ um es I personally saw on my visit in M arch 1987 to the Mayer archives in the Stadtarchiv H eilbronn (“RM-Archiv”) are so designated. Because of the im por­ tance of Johannes M uller’s Handbuch der Physiologie des Menschen and the com ­ plexity of its publishing history, I have provided detailed bibliographic informa­ tion on its separately published parts. W henever an issue (H eft, cahier, etc.) of a journal bears a date and not also a num ber, th at date (usually a m onth) is put in parentheses after the page num bers of the entry. W h en it bears both a date and a num ber, the date appears in paren­ theses after the issue num ber. T he parenthetic addition “(* M ay)” (for example) refers to the nom inal date of the issue as determ ined by its num erical sequence am ong the (usually twelve) annual num bers of the journal in question; it should not be assum ed th at the issue actually appeared in th at m onth. I have used the following standard G erm an abbreviations: A btfh]. (Abt[h]eilung = part), Bd. (Band = volume), Hft. (Heft — num ber or issue), Jg. (Jahrgang ~ the ‘how m an ieth ’ year), Nr. (Num mer = num ber), and St. (Stuck = num ber or issue). I have also used the handy G erm an abbreviation bzw. (beziehungsweise) , which m eans ‘or, as the case may be.’ N ote th a t periods mark ordinal num bers (e.g., “2. Halfte ” = second half). T he titles of four m ultivolum e reference works have been abbreviated as follows: ADB. Allgemeine deutsche Biographie. Ed. Historische Com m ission, Konigl. Akademie der W issenschaften. 56 vols. Leipzig: D uncker & H um blot, 1875-1912. DSB. Dictionary o f Scientific Biography. Ed. Charles C. Gillispie. 16 vols. New York: Charles Scribner’s Sons, 1970-80. GVDS. Gesamtverzeichnis des deutschsprachigen Schrifttum s (GV) 1700-1910. Ed. Hilm ar Schmuck and WiIIi Gorzny. 160 vols. plus a vol. of Nachtrage. M unich [etc.]: K. G. Saur, 1979-87. NDB. Neue deutsche Biographie. Ed. Historische Kommission, Bayerische Akademie der W issenschaften. Vols. 1-14. Berlin: Duncker & H um blot, 1953-85.

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R o b e r t M a y e r is well known as one of the several codiscoverers o f th e principle of th e conservation of energy, th e form ulation of w hich was arguably th e m ost im p o rtan t single developm ent in physics during th e n in e te e n th century, one which recast and unified th e entire subject. Equally well known, at least in a general way, are th e circum stances leading to his ostensibly sudden discovery: his voyage as ship’s d o ctor to th e D u tc h East Indies and his observation there, while lettin g blood, of th e lighter-than-expected color of th e venous blood of recently arrived E uropeans. A lthough M ayer’s im pact on th e developm ent of science was slight, his historiographical significance is considerable. H e is a chief figure in com parative studies— such as K uhn’s pioneering “Energy C onservation as an Ex­ am ple of S im ultaneous Discovery”— th a t exploit th e circum stance of m ultiple discovery in order to isolate factors of general explanatory im p o rtan ce.1 And his association w ith Naturphilosophie, now widely accepted, is regularly invoked as an exam ple of th e historical im portance of this long-discredited m ovem ent, and, at least by im plication, of th e general im portance of philosophical speculation to th e history of physics. A m ong these discoverers, however, M ayer occupies a peculiar position. Insofar as calculation of th e m echanical equivalent of h eat has, since M ayer’s day, b een regarded as an indispensable co m p o n en t of th a t discovery, M ayer’s claim to prior­ ity of p u b licatio n is solid. Yet because his work was ignored by his contem poraries u n til oth ers— notably Joule and H elm holtz— advanced sim ilar ideas, and because his co m m an d of physics otherw ise looks so tenuous, it can b e tem p tin g to dism iss his accom plishm ent as a fluke, especially since his own route to energy conserva­ tion has rem ained an enigm a. His sources are obscure, and co m m en tato rs have repeatedly n o ted , w ith frustration and even annoyance, th a t his own fragm entary accounts of his discovery do n o t seem adequately to explain th a t w hich centrally needs to be explained, th a t is, how he discovered th e conservation of energy. T h a t he in deed experienced som e kind of relatively sudden insight a tte n d a n t upon his bloodletting experience seem s certain; th a t this insight m ight have been som e­ thing like th e conservation of energy seem s w ith equal certainty to b e exceedingly unlikely. As this study will dem onstrate, M ayer’s roughly reconstructible process of discovery exhibited a com plex internal stru ctu re over a period of several years, a process guided m ore th a n anything else by his p en ch an t for analogies.2 K uhn recognized th a t to couch his problem in term s of “sim ultaneous discov­ ery” was m isleading, since “only in view of w hat hap p en ed later can we say th a t all these partial statem en ts even deal w ith th e sam e aspect of n a tu re .” A nd H eim ann insisted even m ore strongly th a t seeing Mayer simply as one of th e codiscoverers of energy conservation has co n tin u ed to d istort our u n d erstan d in g of his work and in ten tio n s.3 Yet this general appreciation has n o t led to a deeper u n d erstan d in g of M ayer’s work, in large part, I suspect, because no one has known q u ite how to exploit it in rendering intelligible th e particulars of M ayer’s process of discovery,

of whatever it was he discovered! T he comparative approach itself, however valu­ able it may be, has perhaps facilitated the unw arranted association of M ayer’s work with general factors valid perhaps for others b u t not especially relevant to him. For example, of Kuhn’s three “trigger-factors” responsible for sim ultaneous discovery— availability of conversion processes, concern w ith engines, and Naturphilosophie— only the second was particularly im portant to Mayer7 and even that one in a way quite different from its significance to others. A lthough H eim ann correctly underscored “the conceptual individuality of M ayer’s natural philoso­ phy,” he did not in fact succeed in going beyond his otherwise perceptive textual analysis to provide the context necessary for a full historical understanding. Buck’s praiseworthy attem p t to chart M ayer’s process of concept form ation w ent too far, it seems to m e, in denying Mayer any conception of the conservation of energy till 1845.4 Such a notion played a decisive role from very early on. Perhaps the m ost sustained and probing historically grounded attem p t to come to terms with the fine structure of M ayer’s thought is Richard Kremer’s. For Mayer, as well as for Liebig and H elm holtz, Kremer argued th at problems relating to anim al heat provided only the general context for reflections on energy conser­ vation: Kremer7like others before him , was not able to trace a plausible route from observations on the color of venous blood to energy conservation simply via the oxygen theory of anim al heat. He proposed instead th at Mayer was stim ulated by "sailors’ chatter about storms warming sea w ater” and by his familiarity with chemistry, in particular the principle of conservation of m atter.5 Although Kremer was on the right general track in sensing the insufficiency of th a t physiological context for the explanation of M ayer’s discovery, his specific proposals were weakly founded. For one, Mayer clearly reported th a t he asked the steersm an about the tem perature of storm -tossed waves, indicating he was already wonder­ ing about the relationship betw een heat and m otion. For another, one could not easily have derived from contem porary chemistry any clear notion of a principle of conservation of m atter. M ayer’s debt to chemistry was considerable, to be sure, b u t it worked itself out in more complex ways. M ost com m entators have tried to explain Mayer by analyzing his ideas— often ignoring those passages or papers they apparently did not know what to do with— w ithout adequate regard to their broad historical context, to M ayer’s possible sources, or to his im m ediate problem context. It is my goal to reconstruct as far as possible those three things and, on th a t basis, to render historically intelligible M ayer’s form ulation of w hat becam e in a wider context the principle of the con­ servation of energy. M any have drawn atten tio n to close parallels betw een M ayer’s language and L eibniz’s discussions of the equality of cause and effect, the inde­ structibility of force, the impossibility of perpetual m otion, and the principle of sufficient reason.6 T he parallels are indeed close, b u t in the com plete absence of plausible routes by which Mayer m ight have confronted such considerations, it seems idle to adduce them as historically relevant to understanding him. I place no explanatory weight on general and unm ediated intellectual affinities. On the other hand, I am well aware of the fragility of an historical reconstruction that necessarily depends to some extent on the chance survival of often unique refer-

ences— such as M ayer’s single m en tio n of Strauss in a le tte r to his parents— and on th e discovery or n o t of this or th a t source, and I have tried to avoid unw ar­ ranted explanatory closure around th e evidence I have assem bled. M y approach has been to try to identify sources in the first instance w ithin science th a t M ayer m ight reasonably b e expected to have know n and th a t can help m ake intelligible th e essential com ponents of his thinking and th e specific striking usages of his writings. In my view, significant theoretical reconceptualiza­ tions— conventionally b u t im properly included w ithin th e category of ‘dis­ coveries’— can only be understood w hen one has some n otion of th e specific is­ sues and problem s th e scientist in q u estio n was already preoccupied with. Such ‘discoveries’ represent solutions to problem s. O nly in th a t way can one appreciate th e attractiv e force, th e meaning, of new ideas for th eir originator. T h e two ques­ tions to pose sim ultaneously are: W h a t was th e new idea? and, W h a t kind of reconceptualization did it effect w ithin th e changing field of th e scien tist’s dear­ est concerns? Such a process of extended ‘discovery’ I have term e d th e (progres­ sive) crystallization of m eaning, and I hope to show abun d an tly and convincingly how M ayer’s route to som ething like energy conservation represented a pro­ tracted process in th e course of w hich what h e was discovering w ent h a n d in hand w ith its changing and increasingly clarified meaning. My decision in th e first instance to investigate sources w ithin science— as o p ­ posed to social situ ation, religious convictions, m ore straightforw ardly philosophi­ cal texts, and th e like— m u st be understood strategically a n d n o t dogmatically. T h a t is, I believe explanations in th e history of science m u st begin w ith a recon­ naissance of th e technical issues, n o t u n d er th e assum ption th a t such will be sufficient, b u t from th e conviction th a t, m ethodologically, one only th u s knows w hat needs to be explained an d only thus can judge how m u ch explanatory space rem ains to be filled through an appeal to extrascientific factors. In th e event, I have situ ated M ayer’s reflections w ithin a very broad range of in terco n n ected scientific, m etaphysical, and theological issues. In practice, m y procedure was first to read all of M ayer’s works, scrutinizing th em for clues ab o u t his sources an d wider intellectual context. I m ake it a general procedural rule to take a scien tist’s own account provisionally as valid unless and u n til I am forced for good reasons to question it. M y experience is th a t such accounts, properly u nderstood, provide som e of th e b est evidence th e historical d etective has. Indeed, it am azed m e w hen, after I h ad wrestled for several years w ith a som etim es opaque and intractable subject and h ad reached a p o in t where I th o u g h t I finally clearly com prehended th e problem and its solution, I discov­ ered th a t my hard-w on insights were little m ore th a n w hat M ayer h ad said all along! T h e trick, of course, was to b e able to recognize w hat was significant, and th en to have th e confidence to accept it as valid. I have been struck by how m any co m m en tato rs dism issed or otherw ise explained away th e significance of th e cen­ terpiece of M ayer’s own several accounts of his discovery, nam ely his observation of th e color of venous blood while off th e Java coast in 1840. N o fewer th a n five q u estio n ed its physiological validity.7 H eim an n speculated th a t, w hen M ayer re­ co u n ted his story in 1845, “his in terp retatio n of his observation m ade in 1840 may

well owe som ething to retrospective reconstruction” due to his subsequent read­ ing of Liebig's A nim al Chemistry. Breger was bothered that w hat he called the “Java anecdote” did not adequately explain M ayer’s discovery of energy conserva­ tion, and suggested it continued to be repeated because of our em barrassm ent at not being able to explain him otherwise. Likewise bothered th at “the Java story does not explain how Mayer came to form ulate his version of energy conserva­ tion,” Kremer adduced evidence (unfortunately for his argum ent, m isinterpreted) that “Mayer could not have been surprised by the bright venous blood he ob­ served in Java.”8 Kremer further speculated th a t Mayer m ight have chosen to accentuate the “Java anecdote” in order to legitim ate his, a physician’s, observa­ tions as having been properly physiological. This dismissal of M ayer’s own testi­ mony accorded with K rem er’s rejection of “the claim that physiological considera­ tions, per se, led Mayer to his discovery.”9 W here such com m entators went wrong was in rejecting M ayer’s account because they could not see how Mayer or anyone else could reasonably have inferred the conservation of energy from the reported observation.10 In fact, he didn’t— b u t I’m getting slightly ahead of the story. T he next stage of my investigation was to establish M ayer’s context: W h a t had he likely read or heard about? W h a t problems m ight he have been preoccupied with? By following up what few specific references there were and reading broadly through the contem porary literature in physiology and physics— especially Ger­ m an and French textbooks— I was able to get a grounded sense of what someone in M ayer’s position would likely have been confronted with, under the assum p­ tion that he was reading anything. It becam e clear th at there was appreciable consensus with respect to m ost of the relevant issues, so it becam e less of a prob­ lem not always to be able to say with confidence which of the likely works or editions Mayer actually saw. T he more this context unfolded, the less strange and idiosyncratic M ayer’s writings appeared. AU the same, several authors loomed as arguably of particular significance, namely Johannes Muller, Jacob Friedrich Fries, and Johann Heinrich Ferdinand A utenrieth, one of Mayer's medical professors at Tubingen. Expanding M ayer’s relevant context beyond the obvious dom ains of physiology and physics was m ore problem atic, since judgm ents of relevance becom e more subjective the farther one gets from the clearly pertinent. For example, I devote little space to issues such as the proliferation, in the decades before 1840, of examples of the interconnections betw een various forces, or to the protracted debate over theories of the pile, because in my estim ation they were not a signifi­ cant part of M ayer’s intellectual world, despite their obvious general relevance to the conservation of energy. On the other hand, I devote considerable space to topics never before considered in connection w ith Mayer, such as the importance of David Friedrich Strauss and theological issues, of Justinus Kerner and spiritual­ ism, of hom eopathy, and, especially, of the existence of a “com m on context” (to use Robert Young’s apt phrase) where m edicine, physiology, theology, and ontol­ ogy came together around problems of the soul, the vital force, and the body. T he organization of the book reflects in some ways my research strategy, since in my view the product cannot be wholly separated from the process of produc-

tion. T h e first ch a p te r introduces M ayer th e person by providing a focused b io ­ graphical sketch of his background, education, voyage, personality, an d career. A lthough this study is n o t a biography in the conventional sense, it atte m p ts a m eaningful in teg ration of M ayer’s life and work by d em o n stratin g how th e direc­ tion and quality of his work bore th e clear stam p of his circum stances, his person­ ality, and his circle of friends. T h e second chapter offers an analysis of his work aim ed at identifying th e leading ideas and peculiarities th a t require explanation. I pay m ost a tte n tio n to th e crucial first two years of his work, th o u g h w ith o u t ignoring later developm ents and th e insights th a t later writings provide w ith re­ spect to th e genesis of his ideas on force. From beginning to end, M ayer’s work was m arked by a few strongly held ideas and guiding m otifs. T h e th ird th ro u g h fifth chapters a tte m p t to establish th e relevant context w ithin w hich M ayer’s thinking developed and in term s of w hich alone it can be understood. C h ap ter 3 describes th e state of contem porary thin k in g on such physiological problem s as th e physiology of th e blood, respiration, and anim al heat; th e relationship betw een organism s and th e external world; the vital force and its relationship to th e soul on th e one h an d and to th e im ponderables (heat, light, an d electricity) on th e other; and hom eopathy. It briefly considers th e rele­ vance of con tem p o raneous technological change w ith respect b o th to th e actual m achines, steam engines, and railroads th e n increasingly visible, an d to th eir sym ­ bolic value. O n e of th e im p o rtan t d eterm inations in chapter 3 is th a t alm ost no au th o r of th e 1830s accepted w ith o u t significant reservation Lavoisier’s expla­ nation of th e g eneration of anim al h ea t in term s of oxidation. H ence M ayer’s unqualified accep tance of th a t theory should be seen n o t as a natural startin g point b u t as a crucial early conclusion th a t w ent h an d in han d w ith his evolving in terp retatio n of his observations. It also represented a crucial crystallization of m eaning w ith respect to th e prim ary fun ctio n of respiration: from th e rem oval of waste carbon from th e blood to th e prod u ctio n of anim al heat. C h a p te r 4 estab­ lishes a baseline in physics and chem istry w ith respect to issues such as the con­ ception of m atter, force, and th e im ponderables (which in this co n tex t also in­ cluded m agnetism ); th e handling of central forces; and th e absence of any explicit principle of conservation of m atter. As w ith his ‘creative’ in terp retatio n of La­ voisier’s theory of respiration, M ayer did n o t so m u ch draw upon an existing prin­ ciple of th e conservation of m a tte r as m ake explicit to him self th e uncreatability and in d estructibility of m a tte r as he forged a coherent conception of force. C h a p ­ ter 5 considers discussions of th e n atu re and scope of science an d notes th e trans­ form ation underw ay (beginning in earnest around 1840) in th e study of organic systems. In it I fu rth er explore th e thick web of religious and spiritualist issues woven in M ayer’s im m ediate surroundings by the likes of Strauss and Kerner, and weigh th e p o ten tial significance of th e literature on natural theology. T hese chapters, th en , provide a basis for an historically grounded u n d ersta n d ­ ing of M ayer’s vocabulary, conceptual framework, and problem context. W h a t force m ean t to M ayer can only be appreciated if one knows w hat th e ram ifications of th e term were in th e full range of th e literature h e likely knew. O ne can n o t u n d erstan d how M ayer could have com e to believe in som ething like th e conser-

vation of force unless one knows the locus of contem porary discussions relating to the creation and destruction of things like forces, the im ponderables, and the soul. One cannot understand M ayer’s creative exploitation of a host of rich analo­ gies unless one knows the meanings and connotations of the term s involved. One cannot appreciate the circum stances surrounding the creation and elaboration of his ideas w ithout knowing what his contem poraries were saying about, for exam­ ple, Stoffw echsd and Lebenskraft: Mayer stepped onto the stage during a crucial period in the developm ent of life-scientists’ self-consciousness about the nature of science and scientific explanation. Even if, given the state of the available evi­ dence, it may not be possible to identify with certainty all of M ayer’s specific sources, it is nevertheless possible to make his work well-nigh completely intelligi­ ble w ithin the contexts of historically constructed fields of m eaning. A close famil­ iarity with M ayer’s broad context is thus a necessary precondition for understand­ ing his words, ideas, analogies, and guiding motifs. After all, it was from th at context th at he derived the elem ents th at he reshaped and rearranged in forging his own ideas. O n the other hand, it would be foolish to think th at Mayer can somehow be rendered solely in term s of his general context. O f crucial impor­ tance was also his preoccupation w ith a num ber of specific problems·, th at was what chiefly stim ulated his creative drive and gave his reflections concrete form. They provided the conceptual nuclei around which his evolving thoughts contin­ ued to crystallize. If M ayer’s work was decisively shaped by his historical circum ­ stances, it was nevertheless the product of a unique creative individual seeking solutions to a particular set of problems. In elaborating the scientific context of the 1830s and 1840s I have m ade a special effort to tease o ut the many connections am ong the various members of the scientific com m unity— in letters, book reviews, and other published works. There was a real com m unity of researchers who read and com m ented on one another's work. Indeed, despite his relative obscurity, Mayer was himself an inter­ acting part of the com m unity of scientists struggling to come to term s with the concepts of force and the imponderables: he derived his problems, concepts, and data from it, and he chose to address his own work to them . Nor were many of the works th a t are little known today— such as A utenrieth’s books and various Latin dissertations— unknown to th at community. Believing th at the historian m ust pay primary attention to language and the field of m eaning of particular words, I have tried to render my subjects’ work in as unanachronistic term s as possible and have been generous in quoting from primary sources, since those sources are always richer in m eanings than the points we often wish to distill from them . I have also paid particular attention to the dating of primary sources, since it is necessary to know who m ight have known what when in order to be able even to speculate intelligently about the progress of ideas— especially since Mayer was away from Europe for m ost of a year, and since the published date of many works does not accurately represent the tim ing of their appearance. T he sixth chapter situates M ayer’s work w ithin the context so established. As far as the evidence and reasoned speculation will allow, I have attem p ted to recon­ struct the likely path of M ayer’s earliest thinking and to chart its subsequent

progress for th e period after June 1841, as m ore contem poraneous evidence b e­ com es available. M y goal has been historical intelligibility: th a t readers be able to make sense of all aspects of M ayer’s work in term s of a plausible, historically grounded reconstruction. In th is ch ap ter I argue th a t it is w ithin th e broad m e ta ­ physical-m edical co n tex t identified above th a t th e takeoff point of M ayer's think­ ing m u st be situ ated. R eflection on problem s of anim al h ea t and th e physiology of respiration, coupled w ith a guiding analogy betw een organism s and work-per­ form ing m achines, presented M ayer w ith th e logical conclusion th a t th ere m u st be a co n stan t relationship betw een h ea t and work (or “m o tio n ,” as he usually p u t it). It is crucial to realize, however, n o t only th a t M ayer did n o t thereby discover energy conservation, b u t th a t h e did n o t yet even have a concept of energy (or force— M ayer spoke consistently of Kraft). In concentrating th eir a tte n tio n upon the issue of th e conservation of energy, som e historians have n o t fully appreciated just how im p o rtan t, and difficult, M ayer’s creation o f a tractable concept of force was. O n th e basis of evidence adm ittedly circum stantial, I argue th a t th e idea of the in d estru ctib ility of force— again, n o t yet its conservation— derived from o n to ­ logical reflections on th e relationship betw een m atter, force, and spirit. M ayer believed th a t his co ncept of force was an an tid o te to m aterialism because it vindi­ cated th e existence of som ething nonm aterial in th e world. A t roughly th e sam e tim e— an d th e evidence does n o t perm it a fine-grained reconstruction— he sought clarification as to the n atu re of force from c o n tem p o ­ rary physics texts, an endeavor which, alas, initially created m ore confusion th an clarity and, ironically, even encouraged h im to believe for several years th a t force m ight in fact be created in b o th living systems and divinely ordered “organism s” such as th e solar system . It is ironic th a t M ayer’s calculation of th e m echanical equivalent of h eat in his 1842 paper is generally regarded as establishing his claim to th e discovery of th e conservation of energy, since at th a t tim e he did n o t in fact believe th a t force is conserved, only th a t it ca n n o t be destroyed. M ayer’s assim ila­ tion of living organism s and planetary systems is itself an exam ple of a m ajor th em e of this study: th e search for valid analogies was an essential co m p o n en t of th e elaboration an d circum scription of M ayer’s evolving problem context. T h e general picture, th en , is one of M ayer addressing a specific set of problem s w ithin a broad co n tex t of beliefs, assum ptions, and interests. A lthough I find no explanatory role for w hat one generally thinks of as social factors in this story— and it m u st be ap p reciated th a t I by no m eans reject such in principle— I w ould underscore th e im p o rtance of M ayer’s decision to pursue th e physical aspects of his new and m u ltifaceted ideas an d to appeal to th e physical sciences com m unity. G iven his background and position— h e was a practicing physician who until then h ad shown n o in terest in strictly scientific m atters— it was n o t an obvious choice for him to m ake. C onsidering his own interests and th e fact th a t “m etaphysical” q uestions were routinely discussed in the physiological literature, it is perhaps a testim o n y to th e tenacious c o n se q u e n tia lly of M ayer’s personality th a t, having becom e convinced of th e logical (and disciplinary) necessity of first grounding his theory of force in th e physical sciences before seeking its application to physiol­ ogy, he picked th e audience he did. Having chosen to step forward as a physical

scien tist, he shrank his field of active concern to th e m echanical theory of h eat, a n d in d eed to a single num ber, th e m echanical eq u iv alen t of heat. T h is transfor­ m a tio n is a n o th e r aspect of w hat I call th e crystallization of m eaning. T h e p resen t study, on th e o th er han d , began w ith a narrow er focus an d ex­ p a n d e d as it progressed. T h e ch aracter an d historical significance of Naturphilosophie has long b een a problem of special in terest to m e. My first p ap er as a g ra d u ate s tu d e n t in th e history of science (in T h o m as K uhn’s therm odynam ics sem inar) looked at K ant an d S chelling in order to try to u n d e rsta n d w here M ayer m ig h t have com e from . N o t having stu d ie d M ayer since th e n , I n o n eth eless re­ tain ed strong im pressions from th a t early e n c o u n te r and h a d co n tin u e d to th in k ab o u t Naturphilosophie w hen, a few years ago, I cam e across a casual reference to M ay er’s in d eb ted n ess to Naturphilosophie in a general work having n o th in g in p articu lar to do w ith Mayer, Naturphilosophie, or even n in e te e n th -c e n tu ry G er­ m a n science.11 It struck m e th a t th is co n n e ctio n was well on its way to b ecom ing o n e of th e u n p ro b lem atical, generally acknow ledged facts of th e discipline, yet I knew th a t I, at least, h ad never seen th e p o in t argued m ore th a n superficially. At th a t p o in t I d o u b te d it was tru e b u t still th o u g h t it was possible th a t m ore careful historical research m ig h t salvage so m eth in g from th e claim . (It has never b een my task to disparage Naturphilosophie, an d I have elsew here argued at great len g th th a t it played a m ajor role in shaping th e ch aracter of G e rm an electrodynam ics in th e 1840s.)12 In any event, I th o u g h t th e topic w ould b e a good one to investigate: I h ad already stu d ied Naturphilosophie, G erm an science of th e period, and M ay er’s works, and I th o u g h t I could exploit th e study b o th to clarify our u n d e r­ stan d in g of M ayer’s route to energy conservation and to p resen t som e of th e re­ flections I h a d b ee n n u rtu rin g ab o u t th e ch aracter and role of Naturphilosophie. M y conclusion, to b e argued at len g th in th e seventh chapter, is th a t th ere is no co m p ellin g evidence, a n d little likelihood, th a t Naturphilosophie played a signifi­ ca n t role in M ayer’s creatio n of his theory of force. N evertheless, th e fact th at th ere do exist a few term inological an d co n cep tu al resonances in M ayer’s work suggestive of aspects of S chelling’s philosophy of n atu re should re m in d us of the d istin c tio n b etw een w hat historians can justifiably argue an d w hat actually took place. N o r do existing w eaknesses in th e historiographical trad itio n connecting M ayer w ith Naturphilosophie necessarily m ean th a t a reasonable case m ig h t not be b u ilt on b e tte r evidence. As far as possible philosophical roots of M ayer’s ideas are con cern ed , a case can b e m ad e for th e influence of a d ilu te an d refracted K an tian ism (via Jacob F riedrich Fries a n d P hilipp L orenz G eiger). B ut th e im por­ tan ce of properly K antian ideas m u st n o t be overrated, an d I prefer to avoid iden­ tity labels a n d assig n m en t to trad itio n s and instead to em phasize specific ideas from specific works. It should b e n o ted , too, th a t th e m etaphysical-m edical con­ tex t m e n tio n e d above c a n n o t b e assigned to any particu lar n am ed philosophical m o v em en t, b u t rath er reflects widely diffused concerns ab o u t th e n a tu re of the soul a n d its relation to th e body, ab o u t w here th e vital force com es from in the g en eratio n of new beings, an d th e like. W h a te v e r th e conclusion w ith respect to Mayer, I believe this study will con­ trib u te to an en h an ced u n d e rsta n d in g of th e place of Naturphilosophie w ithin

early n in etee n th -cen tu ry G erm an science. Similarly, I believe its p lacem ent of M ayer w ithin a bro ad intellectual context will shed im p o rtan t light on th e general situ atio n in G erm an science at a tim e of m ajor disciplinary transform ation. M ore centrally, I hope to have m ade M ayer historically intelligible in a way th a t will co n trib u te to a general u n d erstan d in g of th e process of scientific discovery. Para­ doxically, th e m ore one u n d erstands Mayer, th e m ore one sees how an apprecia­ tion of his idiosyncratic uniqueness advances in step w ith an appreciation of th e m anifold in terco n n ections betw een h im an d his context.

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The Man and His Work

M ayer th e Person I M

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p b r in g in g a n d

E d u c a t io n

Julius R obert M ayer was born on 25 N ovem ber 1814 in the city of H eilbronn, a form er R eichsstadt situ ated on th e N eckar River in th e southw est G erm an king­ dom of W u rtte m b e rg .1 H eilbronn, a prosperous city and one of the quickest in th e state to industrialize during the n in e te e n th century, saw its p o p u latio n rise from aro u n d 7,100 in 1820 to 11,300 in 1840 and 14,300 in 1860; grow th in th e surrounding d istrict kept pace, and co n trib u ted an additional population about equal to th a t of th e central city.2 Its in h ab itan ts were overwhelm ingly Evangelical (i.e., L u th eran ), as was M ayer’s family. M ayer’s father ow ned an apothecary in w hich his th ree sons received early practical chem ical experience. T h e eldest brother, Fritz (born in 1805), first worked as an assistant to his father, th e n took over th e enterprise som etim e around 1832 or 1833; th e m iddle brother, G ustav (bom in 1810), worked as an apothecary in th e B aden towns of M esskirch and Sinsheim before em igrating to A m erica in 1849. G ustav R iim elin, one of R obert M ayer’s lifelong closest friends, reported th a t M ayer senior devoted his free tim e to scientific studies an d experim ents and th a t th e M ayers’ house was filled with physical and chem ical apparatus and in stru m en ts, botanical and m ineralogical collections, m edicinal plants, a n d m any books, especially travel accounts. H e re­ called th a t M ayer perform ed experim ents and exhibited curiosa to his friends, skillfully o perating an air p u m p and various electrical devices. 'Young M ayer was fam iliar w ith elem entary chem ical procedures, could identify th e co n ten ts of m ost of his fa th e r’s apothecary canisters and tell w hat they were used for, and could n am e p lants according to th e L innaean system .3 In several of his autobiographical sketches M ayer told th e story of his childhood fascination w ith m achines and his abortive a tte m p t to construct a p erp etu u m m obile. A lthough th e lasting significance of th e experience for M ayer has been called in to q u estio n ,4 I take M ayer’s ac co u n t seriously and will later argue th a t th e lesson h e thereby learned played a crucial role in th e developm ent of his theory of force. M ayer recounted his early endeavors in great detail (writing of him self in the th ird p erso n ): Already as a young boy, chem ical and physical experim ents and the construction of watermills in his hom etown were m uch more attractive to him than the prescribed study of Latin and Greek, which frequently drew down upon him the dissatisfaction of his teachers. Is is perhaps appropriate here to recall an in itself unimportant incident which, given the impressionable spirit of youth, made a lasting impression on our investiga­ tor. He m ust have been som ewhat more than ten years old. It was a com m on diversion

in the afternoon hours to place small waterwheels in a small brook (the Pfuhlbach) which flowed into the Neckar at Heilbronn, and by m eans of their rotation to m ove other small objects as well. N ow it was on this occasion that our small m an hit upon the great idea of constructing a perpetuum m obile. In his m ind he fastened to the axle of such a w heel an A rchim edes screw, whose operation he knew from Poppe’s Physikalischer Jugendfreund, which he had gotten from his father for Christmas. But since when such an endless screw runs over a large cogw heel what is gained in “force” is lost in speed, he accordingly restored this loss easily again by having the large cogwheel engage a small one. N ow on th e axle of this small cogw heel there is again a screw, which engages a large cogw heel, etc. In this way, by m eans of such a transference, the boy concluded, so m uch force m ust obviously b e gained that arbitrarily heavy m a­ chines could be driven by a tiny waterwheel. Set straight by other, older people— namely, that by m eans of th e transference [of m otion] from a large cogw heel to a small one as m uch “force” is again lost as one gains in speed— h e in turn quickly gave up his project, but through his error at such a young age attained the insight [that m echanical work cannot be created out of nothing].5

This disappointm ent, however, did not keep young Mayer from continuing to be fascinated by the m echanical devices th a t were becom ing increasingly com ­ m on in the area. Friend Riimelin, who had gone off to the Evangelical school in nearby Schontal in the fall of 1828 (where Mayer would join him the following spring), recalled th at Mayer wrote to him then “th at he now spent his free time in the num erous and diverse mills and factories which lay next to each other along the Neckar, studying their m echanism and assisting the people in their work.”6 Mayer apparently continued to be fascinated by m achines' ability to do work and by the operators’ ability to control their effect by m eans of relatively small causes. After noting, in a late essay, that people are by nature so constituted th at they like to obtain the greatest possible results by expending the least m eans, he went on to reminisce about his boyhood fascination with m achines: “From the years of my youth I still rem em ber very well how on free afternoons I spent m any an hour in a sawmill, where by pressing on a lever and withdrawing the sluice gate the m ech­ anism was set in m otion.”7 A fter attending the Evangelical school in Schontal for two and a half years and then assisting in his father’s apothecary for eight m onths, M ayer enrolled at the Eberhard-Karls-Universitat in T ubingen in May 1832 to study m edicine.8 W ith the exception of a physics course during his first semester, his five-year program of study was devoted entirely to his m edical training.9 T he m edical faculty at the tim e seems to have consisted largely of relatively unprogressive and unphilosophical teachers of a practically oriented m edicine, and the claim th a t the ideal­ istic philosophy of Hegel “wholly determ ined” the intellectual clim ate at T ubin­ gen while M ayer was there is w ithout foundation.10 T he dean of the faculty and chancellor of the university, Johann Heinrich Ferdinand A utenrieth, had a solid reputation as a defender of an empirical approach to m edicine allied with anat­ omy and physiology and thus as an opponent of the various currents of Roman­ tic m edicine th a t were, in the early decades of the century, gaining widespread

allegiance at m any other G erm an universities." C ontem porary reviewers of Auten rie th 's Handbook o f Empirical H um an Physiology repeatedly em phasized his devotion to em pirical observation, in contrast to th e speculations of those influenced by N aturphilosophie.12 O f M ayer’s teachers, I find only one to have shown any significant a tta c h m e n t to one o f th e th en -co m p etin g m ajor philosoph­ ical m o vem ents— Ferdinand G o ttlo b G m elin, who in his General Pathology o f the H um an Body (a book M ayer owned) explicitly em braced K ant’s notio n of purposefulness.13 W ilhelm Griesinger, a close friend of M ayer’s who studied m edicine at T u b in ­ gen from 1834 to 1837, praised only one of his teachers as good, the an ato m ist (and praeses of M ayer’s dissertation) W ilhelm Ludwig Rapp, of w hom we are told by an anonym ous contem porary: “In accordance w ith his m axim only to believe w hat h e can convince h im self of through personal observation, he m u st direct his efforts to such fields as offer him n o obstacle in this connection, and he thus accords alm ost no room to speculation. He does n o t directly adm it his generally assum ed a tta c h m e n t to m aterialism ; however, in his lectures h e concedes th e hig h est significance to m a tte r and (in particular) to th e blood.”14 A nother m em ­ b er of M ayer's circle of m ed ical-stu d en t friends, W ilhelm Roser, recalled th a t “th e physiologist W. R app ta u g h t th e propulsive force of th e blood and th e p a­ thologist F G m elin th e polarization of th e vital force. T h e o th er pathologist, A u ten rieth (junior), ta u g h t according to his ow n system , in w hich th e scabious and m iliary sequelae, etc., played a p ro m in en t role.” U n stim u la te d b y th e instruc­ tio n offered by th e m edical faculty, Roser an d his cohort read Johannes M uller, Frangois M agendie, and th e four u n au th o rized volum es of Jo hann Lucas S chonlein’s clinical lectures. B ut good books were hard to identify and o b tain .15 T h e only m em b er of th e T u b in g en m edical faculty to inspire m em bers of the younger g eneration was A lbert Friedrich Schill, Privatdozent from 1835 u n til his u n tim ely d ea th from typhus in 1839. Schill was a m ajor force in introducing his en th u siastic stu d en ts to th e new French and English clinical m edicine, n o t least by len d in g stu d en ts books from his own library.16 T h ese stu d en ts did n o t, how ­ ever, include M ayer.17 In ad d itio n to G riesinger an d Roser, M ayer was close to one o th er reform m in d ed and dynam ic young m edical stu d en t, Carl A ugust W underlich. G riesin­ ger, Roser, an d W underlich, who were to becom e three of th e m ost active voices in th e reform of G erm an m edicine after 1840, had atte n d e d th e S tu ttg art G ym na­ sium to g eth er and actively shared an interest in natural history, botany, and chem istry.18 W u n d erlich an d Griesinger, like Roser, tu rn ed to th e th e n b ran d new tex t of Johannes M uller to m ake u p for th e deficiencies of th e classroom , in w hich a n tiq u ated lore was d ictated from old lecture n o te s.19 T h e quality of M ayer’s association w ith these young m en is difficult to d eter­ m ine. Griesinger, W underlich, an d M ayer were am ong th e cofounders in 1836 of th e forbidden stu d e n t corps G uestphalia, having all previously been m em bers of th e corps G iovania.20 Yet th ere is no evidence th a t M ayer shared th e ir d isen ch an t­ m e n t w ith th e ed u cation being offered or th eir enthusiasm for Schill, and n eith er W u n d erlich ’s necrologue on G riesinger nor R oser’s and H e u b n e r’s on W under-

lich n or any o th e r rem iniscences of his three m e d ica l-stu d e n t friends m e n tio n M ayer as having shared th eir reform ist dynam ism .21 H is self-professed conception of m edicine reinforces this im pression: W ith regard to the principles which guided and guide me at the sickbed, I belong to those who understand m edicine, the ars medendi, as an art and not as a science. Here one m ust not follow the principles of som e logically thought-out system , but each individual case is to be apprehended by itself and treated according to the rules of an eclectic em piricism , whereby the [doctrine of] “ex juvantibus et nocentibus” is decisive [i.e., according to w hether the treatm ent helps or harms]. . . . As my es­ teem ed teacher, th e ingenious [geistvoll} chancellor Autenrieth in Tiibingen, nicely put it in his introduction to nosology, the system is like a tangent drawn to a circle, to nature; in order not to distance itself too far from the circle, the tangent m ust often be broken, and this inconsequentiality in the world of our thoughts is the necessary consequence of our insufficient knowledge of the objective world; otherwise the rigid system b ecom es a Procrustean b ed .22

A u ten rie th was th e only teach er of w hom M ayer ever spoke highly, calling him geistreich in a n o th er reco u n tin g of his com parison of an explanatory system “w ith a ta n g e n t draw n to th e great circle of tr u th .”23 It is possible, too, th a t M ayer m ig h t have b ee n alien ated by th e m aterialistic and re d u ctio n ist approach to m edicine to w hich his friends subscribed. In February 1837 M ayer a n d a n u m b e r of Corpsbruder were arrested for w earing th e colors of a forb idden organization. M ayer an d G riesinger w ere expelled for a year, and W u n d erlich received three weeks’ in carceration.24 D uring th e sum m er an d fall of 1837 M ayer traveled to Sw itzerland an d visited clinics in M u n ich and Vienna, th o u g h w ith o u t no tab le effect. R iim elin could n o t recall any significant details of th o se visits, and D iep g e n ’s later investigations failed to tu rn u p any traces of M ayer’s presence in e ith e r city.25 N or are there any d etec tab le traces of his later a tte n d a n c e a t m edical lectures a n d d em o n stratio n s in M u n ich in N ovem ­ b er a n d D ecem b er 1838. D u rin g his enforced absence from T u b in g en , however, M ayer apparently solid­ ified his desire to travel to th e E ast Indies, a region of th e world th a t h a d fasci­ n a te d h im since ch ild h o o d .26 H aving passed his m edical exam s a n d co m p leted his dissertatio n (on san to n in , an an th elm in tic ) in 1838, h e traveled to A m sterdam in June 1839 to take th e exam in atio n to b ecom e a sh ip ’s d o cto r in D u tc h service. H aving b e e n a d m itte d to th a t service late in S eptem ber, M ayer sp en t th e next four and a h alf m o n th s in Paris. T h ere h e h u n g o u t w ith his form er university friends Griesinger, W u n d erlich , an d Roser, a n d m ad e th e a c q u ain tan ce of Carl Baur, a stu d e n t of m ath em atics an d m echanics w ho lived w ith M ayer and Roser in th e L atin Q uarter. (Baur w ould later b ec o m e an ad m in istrato r an d teac h er at a n u m b e r of W iirtte m b u rg secondary schools before o b tain in g a professorship in m a th em atics and practical geom etry at th e P olytechnic School in S tu ttg a rt.)27 D raw ing apparently from in fo rm atio n supplied to h im by Baur, W eyrauch re­ corded th a t M ayer principally visited d em o n stratio n s at b ed sid e and in th e oper­ atin g room , w ith o u t show ing any particu lar in tere st in purely scientific m a tte rs.28

2 M

a y e r 's

V oyage

to the

D

utch

E a s t In d i e s

O n 23 February 1840 M ayer left R o tterd am aboard the ship Java to sail to th e D u tch E ast Indies. For m o st of th e voyage his duties as ship’s doctor took up little of his tim e, and h e settled in to a routine th a t included periods of “scientific activ­ ity” once or twice a day.29 Several letters w ritten after th e voyage allow a sharper specification of w hat those scientific activites were. In recounting th e circum ­ stances surrounding his discovery, he portrayed him self as “taking as my starting p oint physiological and pathological investigations” and as “occupying m yself . . . alm ost exclusively w ith th e study of physiology”; h e said he m ade his discovery “th ro u g h th e u n rem ittin g study of a specialized area of physiology,” from “having occupied m yself zealously and unrem ittingly w ith th e physiology of th e blood."30 This study and M ayer’s reflections th ereo n set th e stage for his observation of th e lig h ter-than-expected color of th e venous blood of E uropeans recently arrived in th e tropics. M ayer’s first recorded account of this episode dates from 1845: "D u r­ ing a 100-day sea voyage there h ad occurred no appreciable incidence of disease am ong th e 28-m an crew; however, a few days after our arrival at th e Batavian roads there spread in epidem ic fashion an acu te (catarrhal-inflam m atory) affection of th e lungs. In th e copious bloodlettings I perform ed, the blood let from the vein in the arm had an uncom m on redness, so th a t from the color I could believe I had struck an artery.”31 From th e entries in M ayer’s m edical log it appears th a t those venesec­ tions took place on or shortly after 20 June 1840. S ubsequent accounts confirm th e im portance of these observations in setting off M ayer’s chain of reasoning.32 T here is, unfortunately, little evidence as to w hat books M ayer h ad w ith him . It would seem safe to assum e he took along Johannes M uller’s th e n new and universally acclaim ed Handbook o f H um an Physiology, of w hich h e ow ned th e second edition of th e first volum e (1835) and th e first (and only) edition of the second (1837-40). T h e third part of th e second volum e, although d ated 1840, cam e o u t at th e en d of 1839, h ence M ayer could have had th e com plete work on board.33 Also in his library and reasonable candidates for inclusion am ong the books h e h ad w ith h im are A u ten rie th ’s Handbook o f Empirical H um an Physiology (1801-2) an d B urdach’s Anthropology for the Educated Public (1837), which, d e­ spite its title, covered roughly th e sam e ground as contem porary physiology texts. He m ig h t have h ad one of th e several French or G erm an editions of M agendie’s Elementary Sketch o f Physiology, th e third edition of w hich was translated into G erm an by one of M ayer’s professors and published in T ubingen in 1834-36. A m ong o th er m ajor contem porary works w ith which he was surely fam iliar one should add th e first volum e of Friedrich T ied em an n ’s H um an Physiology (1830) and Berzelius’s Textbook o f Chem istry, m ost of th e second edition of w hich was in his library. M ayer cited th e fourth edition of th e first volum e of G eiger’s H and­ book o f Pharmacy (1833) in his 1838 dissertation and u ndoubtedly owned a copy th a t m ig h t have accom panied him to Java. O n th e basis of evidence to be dis­ cussed in ch ap ter 4, one can conclude th a t M ayer m u st have had at least one physics tex t w ith him , probably Jacob Friedrich Fries’s Textbook o f Physics (1826).

Given the book’s title and its discussion of problems of anim al h eat and respira­ tion, it is tem pting to imagine Mayer having tucked away a copy of H um phry Davy’s Consolations in Travel— G erm an editions of which appreared in 1 8 3 3 and 1 8 3 9 — b u t no evidence supports such an inference. O ne of th e m ost eventful early m om ents of M ayer’s journey cam e when he retrieved the chest of books he brought with him . As he described the event in a letter to his parents: O n the ninth [of March] I was able to obtain m y chest of books from steerage . . . . Trium phantly I held up the Bible and the hymnal w hich I had m ost longed for and w hich give m e pleasant hours every day. R em oved from the tum ult of the world the heart is m ightily disposed to devotion, and living [amidst] the m agnificent natural world one knows nothing finer than to exalt on eself to the Creator. T h e little work by Dr. Strauss that m y dear brother put in and the star chart from my dear father also pleased m e greatly; the latter is put to use every evening, and Straussian principles find such w onderful accord in a soul attuned to true p iou sn ess.34

Given the interest indicated here in astronom y— confirmed by num erous entries in his diary— and his ownership and later citation of a G erm an editon of Herschel’s Treatise on Astronomy ( 1 8 3 8 ) , it is possible he had this book with him , too.35 But what is m ost striking about this passage is th at the three works it m en­ tions— the only three works we can positively identify as having accom panied Mayer on his voyage— are the Bible, a hym nal, and a “Schriftchen von Dr. Strauss,” which can only have been (as W eyrauch suggested in a footnote to the above passage) David Friedrich Strauss’s Two Irenic Essays (i.e., Zwei friedliche Blatter) of 1 8 3 9 . 36 Even if one were inclined to discount the significance of M ayer’s account because it was intended for his parents’ ears, its spirit is corrobo­ rated by a passage in his diary for th at date: “W ith delight I held up the sacred scriptures which I found here; a sea journey disposes one mightily to devotion and directs o ne’s thoughts toward heaven, to the director of the universe [zum Leiter der We/fen].”37 Nor is this the only evidence of M ayer’s deep religiosity. But how can th at be rhymed with his enthusiasm for Strauss, whose L ife o f Jesus ( 1 8 3 5 —3 6 ) had recently brought its author into disrepute as an enem y of C hristianity and had cost Strauss his position as Repetent at the theological sem inar (Stift) in Tiibingen? 3 M

a y e r 's

R eligiosity

N either th e precise quality of M ayer’s religiosity nor its relevance to his scientific work is easy to determ ine, b u t there do seem to be essential connections betw een the two. Although he was fond of quoting verses from the Bible, Mayer seems never to have been attached to its literal historical veracity, nor did his faith de­ pend on revelation. In the opinion of one who knew M ayer in later years, “the Bible was for him an ingenious [geistreich] book of which he knew how to make ingenious use, th at was all.”38 He had, however, a well-nigh unswerving belief, requiring occasional reconfirm ation at tim es of great personal stress, in God as the

providential creator of a harm onious world and in th e im m ortality of th e soul. As he expressed it in a later work, w ith reference to th e presum ed cosm ic d u st which, illu m in ated by th e sun, produces th e zodiacal light, “this dust, too, form s an im p o rtan t link in a creation where n o th in g [happens] by chance, b u t where every­ th in g has been ordered w ith divine purposefulness.”59 G o d ’s benevolence and providence were co n stan t them es in M ayer’s m ore per­ sonal writings. From on board ship in th e S unda straits he w rote to his parents: “T h e infinitely good G od be thanked, who so allotted everything to m e— includ­ ing m inor vexations, which are a necessary part of life— th a t I never becom e tired of praising his w isdom .” A few days later, as th e ship h ad entered th e Batavian roads, h e added: “G od, thy world is b eau tifu l!” Ten days later he w rote th em th a t “since a firm tru st in G od and a cheerful spirit always accom pany m e, you can well im agine th a t it is w ith a calm soul th a t I look forward to th e future, which, like the past, will see its dark and bright hours pass by quickly.” A nd from th e last le tte r he wrote hom e from th e Indies: “I will e n tru st m yself w ith confidence still fu rth er to G o d ’s all-wise providence, w hich has b een so visible in th e vicissitudes of my fate, and if he grants m e b u t one request, th e n I will bear everything w ith a smile; only here am I n o t yet able to pray sincerely ‘Thy will [be d o n e ],’ for th e ho p e is to press all m y loved ones to m y h e a rt again.”40 N o t surprisingly, M ayer frequently gave expression to his religious sentim ents in response to d ea th or illness. To his longtim e friend, th e pastor Paul Friedrich Lang, M ayer wrote: “T h e firm conviction, based on scientific awareness and p u ri­ fied of any belief based on revelation, [both] of th e co n tin u ed personal existence of th e soul an d of a higher direction of h u m a n fortunes, was th e m o st powerful consolation to m e as I h eld th e cold h an d of m y dying m o th er in m in e.” Four years later, having lost one d au g h ter less th a n a week earlier, M ayer w rote to his m otherin-law ab o u t th e im pending d eath of an o th er child, adding th a t “only firm belief in th e divine direction of all th e vicissitudes of h u m an life can give us self-com po­ sure [Fassung].” And to his ailing father-in-law h e wrote: “M ay G od give his bless­ ing th a t th e outcom e [of th e bloodletting] be a really good one! Look w ith cour­ age in to th e future, dear father, for Providence surely directs everything to our b en efit.”41 D u rin g th e period of M ayer’s m ost severe m en tal illness, during th e early 1850s, he found him self possessed by a feeling of “fanatical pietistic sentim entality.”42 A fter M ayer’s long convalescence following a jum p from his third-floor window in 1850, R um elin reported: “A fter these storm s there set in a beneficial calm , he was in a religiously b u o y an t m ood, since he saw in his experiences a higher dispensa­ tion, a penance for his passionateness and a deliverance.”45 M ayer saw his problem in m oral term s, as stem m in g from his lack of hum ility, w hich h e described as his “favorite sin” and his “Achilles’ h eel”; nevertheless, “m y faith is firm th a t I have been fully gran ted th e forgiveness of sins prom ised to m e at th e altar.”44 As he confessed in autobiographical notes w ritten in 1865 for John Tyndall, It is possible that the absence of any recognition, on which I had hastily counted, contributed its part to somewhat cooling my zeal for science for a while; it is certain that at that tim e the interest in transcendental, religious truths began to com e to the

fore with irresistible force . . . . W ith the passionate haste, with the exclusivity, which is a lamentable defect in my temperament, I immediately threw myself into this area as well. I have now grown older and gladly let myself again be counted among the disciples of science, but the zeal for the truths of the Christian religion is nevertheless in no way becoming cooler with me. But what I then silently forbad myself to think, I am now ready to confess without restraint. There lived in me a longing for recognition, and however much I might endeavor to fight back such a feeling as sinful pride, it nevertheless was beyond my powers to suppress in me my scientific consciousness.45 R eflecting on th e recognition his work h ad begun to receive during th e late 1850s, following painful periods of m en tal illness and b ru tal tre a tm e n t during th e early 1850s, he w rote fu rth er to Tyndall th a t “I regarded it as a special dispensation of G od th a t, in order still to experience joy at th e success of my intellectual children, I was able to overcom e suffering th a t m u ch stronger people w ould easily have su ccu m b ed to .”46 Religion th u s provided M ayer w ith faith in th e providential direction of worldly affairs, w ith a belief in th e im m ortality of th e soul, and w ith a strong moral sense of sin and red em p tio n .47 T h e presence in his library of Johann Peter Siissm ilch’s The D ivine Order in the Fluctuations o f H um ankind, Proved from Its Birth, Death, and Propagation (1765)— a work th a t sought to d em o n strate th e workings of di­ vine providence from b irth an d d ea th statistics— suggests th a t M ayer m ay also have h ad an ear for th e argum ents of natural theology com m on in th e 1830s. As will be discussed in ch ap ter 5, M ayer w ould later oppose D arw inian evolution on essentially religious grounds. In n o tin g th a t M ayer's religious views were n o t co n stan t over tim e, W eyrauch observed th a t “only th e opposition to m aterialism an d ath eism rem ained firm w ith h im .”48 And in registering M ayer’s tu rn to religion in th e 1850s, R um elin ad ded th a t “h e h ad earlier already been averse to th e m aterialistic worldview wide­ spread am ong young m edical stu d e n ts.”49 Indeed it was M ayer’s opposition to m aterialism th a t provides th e key to th e co n n ectio n betw een his religious views and his co n cep tio n of force. As will be laid ou t in th e next chapter, one of the things his co nception of force accom plished for h im was to cu t th e ground out from u n d e r th e m aterialistic worldview as h e u n d ersto o d it. A lthough one com ­ m en ta to r w ho exam ined M ayer’s p ro n o u n cem en ts on religion was of th e opinion th a t M ayer d ed u ced th e existence and indestru ctib ility of souls from his energy principle, I will argue for a relationship in th e o ther direction.50 For th e m ost part, however, M ayer did n o t try explicitly to link his religious views to his science. He never, for exam ple, d efen d ed th e conservation of energy in C artesian fashion in term s of th e constancy of G o d ’s action or th e like. In a startlingly friendly le tte r of 1867 to archm aterialist Jacob M oleschott acknowledg­ ing w ith g ra titu d e his election as corresponding m em b er of th e T urin A cadem y of Sciences, M ayer wrote: To you before all others is due the great and lasting service of having successfully defended the principle that scientific matters and researches must not be mixed up

w ith religious dogm as or even ecclesiastical q u estio n s, and even if w e perhaps . . . do not agree on all p oin ts in th e area o f th e supernatural, th en I am all th e less surprised by th at, sin ce in this regard I have n o t even b een able to settle things entirely w ith m yself, d esp ite th e fifty-three years I n ow have b eh in d m e , and thus for th is reason alone agreem ent w ith a third party d oes n o t b elo n g to th e realm of th e p o ssib le .51

M ayer was am bivalent w ith regard to w hether religion and science are in close and harm onious co n n ection or belong to totally different realm s. O ne of his favorite m ottos, w hich h e appears to have m ore or less m ass produced for d istrib u tio n in 1868, held th a t “N ature, science, and religion form an eternal u n io n .’’52 A nd dur­ ing his crisis years he h ad w ritten to Lang th a t “m y earlier in tim atio n , th a t scien­ tific tru th s are to th e C hristian religion as stream s and rivers are to th e ocean, has now b eco m e for m e a living aw areness.”55 Yet w hen Friedrich Durr, who cam e to know M ayer in 1874, asked him how he reconciled (vereinige) his religious faith with th e results of n atural science, M ayer replied: “I d o n ’t reconcile anything; for m e th e physicist stops right here and th e believing C hristian begins.”54 In an address late in life, M ayer urged his audience n o t to confuse th e brain with th e m ind (der G eist), adding: “But th e m ind, w hich no longer belongs to th e realm of th e sensibly perceptible, is n o object of investigation for th e physicist and anatom ist. W h a t is subjectively correctly th o u g h t is also objectively tru e. W ith ­ out this etern al harm ony preestablished by G od betw een th e subjective and o b ­ jective worlds, all our thin k in g w ould be fruitless. . . . L et m e close here. W ith all my h ea rt I proclaim : a correct philosophy ought to and can be n o th in g b u t a pro padeutic for th e C h ristian religion.”55 In a work published eig h teen years ear­ lier— his last m ajor scientific publication— h e h ad w ritten w ith regard to th e p rin ­ ciple of th e equivalence betw een h e a t and m otion th a t “th e experim ental test of this principle, its verification in all particulars, th e proof of the com plete harm ony betw een th e laws of th o u g h t and th e objective world, is th e m ost interesting b u t also th e m o st com prehensive task one can find.”56 A lthough this belief in th e correspondence betw een th e conclusions of reason and em pirically discovered tru th s of th e physical world agrees com pletely w ith th e conviction w ith w hich M ayer som etim es th o u g h t he could estabish his new theory by appealing to w hat he regarded to be th e laws of th o u g h t (such as “n o th in g can be created from n o th in g ”), it is q u ite at odds w ith an o th er of M ayer’s m ottos: “N atu re in its sim ple tru th is grander and m ore m agnificent th a n any creation [Gebild] of h u m a n h ands an d th a n all illusions of th e created m in d [erschaffener G eist].”'57 N or does it rhym e very well w ith a n o th e r of his reflections: W h a t is insanity? T h e reason o f an individual. W h a t is reason? T h e insanity o f m any.’8

A lthough, given th e fragm entary character of th e evidence, it is difficult to chart changes in M ayer’s religious and related philosophical views over tim e, it seem s th a t his earliest and d eepest conviction was in a divinely preordained corre­ spondence betw een th e tru th s of sound reason and th e n atu re of th e external

world, and th at his reservations about th e ability of th e divinely created hum an m ind to discover tru th s about th e likewise divinely created world belong primarily to his later years, and may have been a cautionary reaction against a rationalistic scientific juggernaut seen as threatening to religious faith. M ayer’s opposition in later years to Darwinism , which he called “th e m odern heresy [Irrlehre],” represented a com plex com bination of religious, philosophical, and scientific m otives.59 T h a t the subject touched him deeply is suggested by the fact th a t w hen G ustav Hiifner, the professor of chem istry at T ubingen, visited him in 1873, his nephew asked him n o t to speak w ith him about th a t subject or ab o u t politics: “H e could no t tolerate Darwin’s theory, and as for politics, he was a resolute conservative [Ultramontaner].”ω M ayer’s fullest surviving statem en t of his views on th e m atter came in a letter to the theologian Rudolf Schm id in 1874, in which it is clear th a t for him , as for m any critics then as now, Darwinism stood primarily for th e doctrine of th e spontaneous creation of life: From my standpoint, w hat I m ost object to in D arwin's system is th e following: in n u ­ m erably m any new plant and anim al individuals com e in to existence continuously before ou r eyes through generation and fertilization. How this takes place, however, is for the physiologist a com pletely incom prehensible riddle an d u n fath o m ab le mys­ tery, where the fam ous saying of H aller’s so rightly finds its application: “ [No created spirit penetrates] into th e interior of n atu re .” Seeing how we are obliged to confess our com plete ignorance in these m atters so near and present, all of a sudden th e good Darw in, like a second Lord G od, w ants to give us perfectly solid inform ation about how organism s arose on our planet in th e first place! In my view, however, this goes so ridiculously far beyond th e hum anly possible th a t I would apply the Pauline text: “Professing them selves to be wise, [they becam e fools].” But the Darw inians are cer­ tainly zealous cham pions, and th e m a tte r doubtless has so many followers in G erm any only because one can make capital o u t of it for ath eism .61

T h e relationship betw een M ayer’s antim aterialism and the changing character of th e life sciences after the late 1830s will be gone into in m ore detail in chapter 5. Perhaps Strauss’s early appeal to M ayer was due to th e way in which he sought a C hristianity not based on miracles, one which accepted the law bound causality of natural events b u t was nonetheless opposed to the m aterialism characteristic of the post-R eform ation world and which could bring inner peace to the believer— in o th er words, a C hristianity th a t had room for b o th faith (in the existence of G od and in th e im m an en t divinity of hum ankind) and scientific knowledge (of an orderly world). Strauss’s early opposition to m aterialism was an im p o rtan t them e of his Two Irenic Essays, th e book Mayer had w ith him on board ship. Part of its argum ent was to counter th e denial (by unnam ed opponents) th a t an idea alone— nur eine Idee— could be capable of m ajor historical effect, as if an idea were (causally) nothing.62 Strauss h ad in m ind here the central notion of his theol­ ogy, th e identity of the hu m an and the divine, G od’s im m anence in th e world. Some people denied th at such an abstract idea could have any effective moral force, preferring rather to base religion on faith in the historical facts of th e virgin b irth, miracles, th e resurrection, and the like.63 Here, as in his book on Jesus,

Strauss denied the reality of miracles and rejected the traditional attem pt to tie Christian faith to them. He seconded H um e’s argument against them , and in­ sisted that events be understood as due solely to natural causes.64 AU the forces of nature are equally “natural”: “T he animal-magnetic force, like the galvanic and electrical forces, even the force of imagination and will, insofar as it affects the corporeal organism, are just as much natural powers [Naturpotenzen] as the m e­ chanical forces of collision and pressure by means of which the surgeon operates, or the chem ical forces of salts and oils by means of which the physician works.”65 In Strauss’s historical analysis, the gods mingled freely with people in the oldest tim es but gradually becam e more remote, the interaction between the two realms becom ing less frequent and more oblique. Then Jesus appeared, as God but at the same tim e a man of this world: “But the union had been achieved in an absolute fashion at only a single point; not the truly human as such in general, but this human exclusively had the dignity of the really divine; and likewise the divine had not entered com pletely into worldly reality, but had preserved its otherworldliness for all other points. T he unity of the divine with the human in the person of Jesus was therefore an exception to the rule, a miracle.”66 But miracles are no longer acceptable, and God must be knowable in other ways. According to Strauss, the Reformation did not reject miracles outright but relegated them to the distant past, thereby opening up the possibility of discovering the divine not only through history but also in the order of nature— with portentous consequences: But th e territories of n atu re and history expanded in an ever m ore m anifold and m agnificent fashion before th e eyes of aw akened investigation; order and rule, rational c o n te n t in general, disclosed itself increasingly in b o th ; link co n n ected w ith link ever m ore securely in th e chain of causal con n ectio n in b o th . If from here one glanced over tow ard th e oth er world [das fe m e its] th a t th e old ecclesiastical co n cep tio n offered, th e n it appeared all th e m ore superfluous th e m ore th e [hum an] spirit was satisfied by th e co n tem p la tio n o f natural and historical connections; its intrusion in to th is world [das Diesseifs ] appeared all the m ore inadm issible th e clearer th e recognition of th a t co n n ectio n becam e. If on th e one h an d th e a n tiq u ated system of tran scen d en ce ex­ erted itself as external ecclesiastical power, an d if on th e o th e r h an d th e new principle of im m anence was still strongly realistically tinged th ro u g h th e study of th e n atu ral sciences, w hich h ad first called it into being; th e n th e re resulted in th e first instance w hat we find: a naturalism h ostile to th e ch u rc h an d to C h ristian ity w hich, after it (as deism ) had reduced the vital and richly p o p u la ted o th er world of ecclesiastical belief to th e em pty and dead co nception of a h ighest being, finally (as m aterialism ) d e­ stroyed th e ecclesiastical two-worlds system by sim ply denying one of th e two, nam ely th e ideal world. B ut th e o th e r side to this was th a t conversely idealism , prepared by logical an d m etaphysical investigations, later sacrificed th e corporeal world to th e do m ain of consciousness. In b o th only th e antithesis of spirit an d m a tte r was im m ed i­ ately destroyed; m ediately, however, th a t of th e absolute an d th e finite was also preju­ diced insofar as G od on th e one side was reduced to an ab stractio n [Abstrucfimi] of m atter, on th e o th e r to th e pure ego or to the m oral order of th e world. T h e tru th of th e old dualism is m isperceived in b o th systems: its real overcom ing can n o t com e

about through annihilation o f on e or the other of its sides, b u t only by so recognizing the equal legitim acy o f b oth that their separation is nullified [aufgehoben] .67

Strauss’s picture, then, was of an ordered and lawful natural world subject to rigid causality. In his historical view, naturalism gave rise n o t only directly to m aterial­ ism , b u t also, by way of reaction, to the idealism of the day which denied the reality of the m aterial world. Both extrem es were to be rejected in favor of a revindicated dualism th at accepted bo th Geist and Materie. Such a worldview would sanction th e kind of science M ayer pursued at th e sam e tim e it vindicated th e existence of a nonm aterial realm. M any years later, however, Strauss cam e to defend a num ber of positions th at M ayer vehem ently rejected. In his O ld and New Faith of 1872 Strauss agreed with arch scientific m aterialist Carl Vogt th a t th e assum ption of a particular Seelensubstanz or Seelenwesen is a m ere hypothesis unsupported by any facts and does no t explain anything. R ejecting th e duality of m ind and body, he now proposed th at there is only a single substance (Wesen) , “w hich on one of its ends is extended, on th e other thinking.”68 M ayer would have opposed any such m onistic elim ination of sou] (as of force). Strauss even appealed to the law of conservation of energy (still Kraft for him ) to justify this elim ination of the sensitive soul: “If under certain conditions m otion is transform ed into heat, why should there no t also be conditions u n d er which it is transform ed into sensation?” H e said he did no t object if people found in these views a “crass m aterialism ,” though it is no t clear precisely w hat sort of ontology he stood for. He praised Darwin for having elim i­ n ated purposefulness from nature, im plicitly rejected th e whole natural-theologi­ cal view of nature, and expressed his opinion th a t m odern science has found the sure p ath th a t w ould allow it in short order to make good th e K antian challenge of creating a caterpillar ou t of inorganic m atter.69 An acquaintance called Strauss’s book to M ayer’s attention. A fter reading it, M ayer rem arked to him th at, if Strauss wasn’t a b etter theologian th an he was a scientist, th en h e wasn’t w orth m uch.70 In a brief note apparently in ten d ed as a review of Strauss’s book, M ayer wrote: “In this his new est work Dr. Strauss de­ scribes C hristianity as a ‘belief in m iracles,’ as a standpoint vanquished by D ar­ winism. ‘T h e resurrection is th e greatest lie in th e history of th e world, etc.’ Tim e will tell w hether th e books w ritten by Strauss and his ilk will be able to replace the holy scripture of h u m an k in d .”71 Mayer rem ained unwilling to give up his theistic Christianity, even when his beliefs m ade him som ething of an em barrassm ent to th e m ore generally antireligious and m aterialistic scientific establishm ent in G er­ many.72

4 M

a y e r 's

C

ir c l e o f

F r ie n d s

For som eone whose profession was m edicine and whose som etim e passion was science, M ayer had a striking num ber of close friends w ith strong connections to theology.73 Lifelong friend and future clergyman G ustav R um elin was M ayer’s

com panion b o th at th e Evangelical school in Schontal and then, as a stu d en t of theology, at th e University of T ubingen.74 W hile at Schontal, Mayer becam e fast friends with th e prelate’s son, Paul Friedrich Lang, who also w ent on to study theology at T tibingen and who later delivered M ayer’s funeral serm on.75 At T iibingen o ther close friends included th e theology stu d en t and future poet Karl Gerok— also an in tim ate of Lang’s— and “other of our present-day highest church w orthies.”76 Friend and future novelist H erm ann Kurz was a stu d e n t a t the T ubinger S t i ft , th e renow ned Evangelical theological school.77 Friend Eduard Zeller, a future professor of theology (and later of philosophy), had also atten d ed th e Stift before entering the university, and reported th a t th e m ost im p o rtan t circle of his friends at th e university was a group th a t had graduated from Schontal in 1832, th e year after Mayer.78 A lthough prim arily interested in m athem atics and natural science, friend G ustav Reuschle and later friend Carl Baur were b o th formally stu d en ts of theology at T ubingen since the school as yet had no natural sciences faculty.79 To be sure, Mayer was also closely associated w ith the m edical students W il­ helm Griesinger, Carl August W underlich, and W ilhelm Roser, yet as already no ted there is no evidence he was caught up in th eir enthusiasm for th e reform of m edical science. In general, M ayer gives th e im pression of having been a funloving friend who cherished socializing and card playing b u t showed little inter­ est in strictly intellectual pursuits.80 Alongside his cam eraderie, however, one of his university friends rem em bered “the uncom m unicativeness [Versch lossenheit] of his n atu re” and recalled th a t “his m ore distant acquaintances thought he had a good head, b u t still regarded him as som ething of an oddball [Sonderling],”Si To judge from th e surviving evidence, M ayer seems to have rem ained rather unconnected with a num ber of significant people in his environm ent who were part of his larger circle of friends and acquaintances. Strauss, for exam ple, knew Riim elin and Reuschle at least by 1837 and 1841, respectively.82 Strauss was also close to th e celebrated W einsberg physician and spiritualist au th o r Justinus Kerner, and he reported th a t every fall (for an unspecified period of years) he walked to W einsberg and to nearby H eilbronn.83 Yet no t th en nor even after Strauss m oved to H eilbronn in th e fall of 1843 is there any evidence th a t M ayer had any personal contact w ith him .84 M ayer was friends with Justinus K erner’s son Theobald: they were students of m edicine together at T iibingen (Theobald was there from 1835 to 1840), and the fact th a t Theobald later called M ayer by his schoolboy nicknam e— addressing a le tte r “M ein lieber G eist!”— suggests they were reasonably close.85 And a le tte r from Justinus addressing M ayer w ith the fam iliar “D u ” im plies th a t they, too, were close.86 Even M ayer’s physics instructor at T iibingen in 1832, Ludwig Felix Ofterdinger, rem inisced to T heobald about having visited th e Kerner household in W einsberg often in th e years 1827 and 1833.87 Yet there are no traces th a t Mayer had any significant interaction with any of these people. It has been possible to piece together a network of intercon­ n ecting relationships all around Mayer, b u t he him self largely escapes th e eviden­ tiary net.

5 M

a y e r 's

C

haracter

R em iniscences of M ayer’s closest friends afford precious insights into som e of his outstanding personality traits. According to Riim elin, From his disposition one would call him an a n im a Candida. But everything he said and did bore th e stam p of originality. His train of th o u g h t, w hich was entirely logical— b u t in w hich he skipped or left unspoken th e connecting m iddle term s— was always aston­ ishing and often d um bfounding; by th e tim e one had found th e thread, he h ad already landed som ew here else. And since he never lacked for wit and good hum or, his conver­ sation was always delightful; he had an inexhaustible supply of q u o tatio n s and m ax­ im s from Bible and hym nal, from sayings, poets, and an cien t authors, and he knew how to em ploy them where no one else would have th o u g h t of them . H e possessed th e m ost pronounced sense of play and had the liveliest interest in every kind of gam e; n o t at all for th e sake of w inning, b u t because he eagerly w ent after th e theory of th e different games and im m ediately searched for law and rule. H e becam e an excellent player of chess, w hist, omber, and taroc; billiards and bowling occupied him actively, too; one could com pete w ith him only because he liked to push all rules to th e extrem e and easily becam e a stickler for principle. He was so engrossed in th e changing com binations and problem s of th e m ore pre­ cise gam es as if there were nothing else in th e world, and weeks afterward he could still reconstruct in detail th e state of a chess gam e or a tu rn at omber. T h e m ost prom inent of his intellectual gifts were always th e sense for m echanical causality and th e unrelenting, p enetrating exam ination of a th o u g h t o u t to its farthest ram ifications.88

After noting that Mayer had revealed no predilection for m athem atics or natural science during the tim e he knew him in Paris in 1839, Baur reported that “on the other hand he gave free rein to his com binatorial acum en in his passion for tricks with cards and figures, in the solution of riddles and rebuses, in striking w itticism s and elegant jokes. His predilection for precise and cutting satire w ent hand in hand w ithout contradiction with the warm heart w hich he, as a reliable and selfsacrificing friend, proffered to his friends.”89 And Karl Gerok recalled that Mayer "taught us om ber and entertained us with ingenious paradoxes and witty quota­ tions out of b oth secular and religious literature.”90 From these rem iniscences one obtains a con sistent and convincing picture of Mayer as an original, endow ed with a deep sense of hum or and delight in games of all sorts, with a doggedly logical m ind fascinated by both rules and paradoxes, possesed of a prodigious m em ory and inordinately fond of citing passages from Scripture and secular literature. Even in later years Miilberger reported he had “an alm ost pathological m ania for q uotin g poetry” and biblical texts, a trait also com ­ m ented on by Diirr.91 M ayer’s writings, in particular his letters, are peppered with

biblical and o ther quotations, and he left behind num erous scraps of paper in­ scribed with favorite aphorism s. As will be shown in the next chapter, his exposi­ tion of his ideas on force was strongly shaped by his attach m en t to such Latin dicta as causa aequat effectum , nil fit a nihilo, and nil fit ad nihilum . It has not been possible to trace these to any specific source in M ayer’s am bit, though the traditional status aphorism s enjoyed in the m edical literature since the tim e of H ippocrates may have reinforced M ayer’s attach m en t to them . In one letter he wrote th at “C essante causa cessat effectus is a well-known medical principle.”92 M ayer’s m ental breakdown after 1850, and the suggestive signs of a disposing instability of m ind long before then, are well known and for the m ost part of no obvious relevance to th e story to be told here. T he m ost perceptive analyst of M ayer’s psychological condition— and one of the m ost perceptive readers of M ayer’s writings uherhaupt— H einrich Tim erding, has, however, insisted on the im portance of M ayer’s stubborn attach m en t to simplistic ideas and even apparent absurdities and inconsistencies as lying at the root of b o th his scientific creativity and his m ental pathology.

•

C H A P T E R

T W O

M ayer’s W ork

In FEBRUARY 1841 Mayer returned to H eilbronn to resum e the practice of m edi­ cine, his lifelong profession. His passion, however, was now the further clarifica­ tion and publication of th e ideas on force h e had b een incubating since June of th e previous year. O n 16 June 1841 he sent a m anuscript, “O n the Q uantitative and Q ualitative D eterm ination of Forces,” to Johann C hristian Poggendorff, edi­ tor of th e Annalen der Physik und Chemie, G erm any’s leading physical sciences journal. Poggendorff never replied to M ayer’s three letters to him , and th e m anu­ script rem ained unpublished until retrieved from Poggendorff’s ΝαοΜαβ by Fried­ rich Z ollner in 1881. A lthough confused and q u ite unpublishable, this (appar­ ently) first extended elaboration of M ayer’s ideas is our earliest surviving source of inform ation and provides indispensable clues for the reconstruction of M ayer’s th o u g h t processes. N o less im p o rtan t is th e correspondence M ayer initiated on 24 July 1841 w ith Carl Baur, th e stu d en t of m athem atics and m echanics w hom he had g o tten to know in Paris and who was th en continuing his studies in Tiibingen. As will be shown more fully in chapter 6, the direction of M ayer’s deliberations was influenced profoundly no t only through his interchange w ith Baur, b u t also in response to his m eetings w ith th e T ubingen and H eidelberg professors of physics and, in particular, through his reading of Justus Liebig’s “T h e Vital Process in the Animal, and th e A tm osphere,” published in Liebig’s Annalen der Chemie und Pharmacie in D ecem ber 1841. O n 31 M arch 1842 M ayer sent L iebighis “Remarks on the Forces of Inanim ate N atu re,” which Liebig prom ptly published in th e May issue of his Annalen, thereby establishing th e basis for M ayer’s claim to priority in announcing th e m echanical equivalent of heat, and for others’ inclusion of him as one of th e codiscoverers of the principle of th e conservation of energy. T his ch ap ter will offer an analysis of M ayer’s early work in order to identify the leading ideas and peculiarities in need of historical explanation. I will concentrate on th e two papers m entioned above since they co n stitu te th e earliest expressions of M ayer’s ideas in th e form he wished to make public. If one understands them , there are no m ajor ou tstan d in g problem s with understanding everything th a t cam e afterward. I will also draw upon his later writings to clarify and illustrate som e of his abiding concerns and occasional shifts of m eaning. Since the best in troduction to M ayer’s thinking is via his own u n reconstituted words, I will begin by quoting at length from his first two papers, and th en tease out and com m ent u p o n individual significant points.

I M a y e r 's E a r l i e s t P r e s e n t a t i o n o f H is I d e a s

1.1 “O n the Q u an tita tive and Q ualitative Determination o f Forces” Mayer began w hat he had h oped w ould be his scientific debut with general con ­ siderations about causality, force(s), and an analogy b etw een chem istry and phys­ ics as dealing w ith conceptually com parable objects (i.e., material substances and forces): It is th e task of natural science to explicate th e phen o m en a of b o th th e inanim ate and th e living world in term s of th e ir causes and effects. AU phen o m en a or events depend upon th e fact th a t m aterial substances, bodies, change th e relationship in w hich they stand to each other. According to th e law of sufficient reason [das G esetz des logischen G rundes] we assum e th a t this does not take place w ith o u t cause, and such a cause we call force. Following the causal connection upwards, if we com e to p henom ena whose causes are no longer sensibly perceived, b u t can only be abstracted from their effects, we th en call these forces in th e narrow sense abstract forces.— W e can derive all phenom ena from a prim itive force th a t tends to an n ih ilate th e existing differences, to u n ite everything th a t exists in to a hom ogeneous mass in a m a th em ati­ cal point.— If two bodies find them selves in a given difference, th e n they could re­ m ain in a state of rest after the annihilation of [that] difference if th e forces th a t were co m m unicated to th em as a result of th e leveling of th e difference [behufs der D ifferenzausgleichung] could cease to exist; b u t if they are assum ed to b e indestructible, th en the still-persisting forces, as causes of changes in relationship, will again re­ establish the originally present difference. T hus th e principle th a t forces once given, like m aterial substances, are quantitatively invariable, assures us conceptually of the co n tinued existence of differences and thereby th a t of th e m aterial world. T h u s we assum e th a t b o th th e science w hich deals w ith th e m an n er of being of m aterial su b ­ stances (chem istry) as well as th a t w hich deals w ith th e m an n er of being of forces (physics) have to consider th e q u an tity of their objects as th a t w hich is invariable and only th e ir quality as th a t w hich is variable.1

A lthough m ost of this introductory paragraph is relatively straightforward, it is not im m ediately obvious w hat Mayer m eant by our being able to derive all phe­ n om ena from an Urkraft w hose tendency is to annihilate or neutralize existing differences. C onsidering that forces can alter the relationship o f bodies either spatially sep ­ arated or in contact, Mayer assigned the latter class to chem ical and electrical forces and lim ited his attention in th e first instance to the former, in w hich case the change in the b od ies’ relationship is sim ply m otion: “Supposing we have two isolated bodies in the universe at a given difference from each other, b oth will th en m ove in a straight line toward each other; the ultim ate cause of the forces, or the cause that makes itself known via the leveling of the existing difference, com m un icates m otive force to both bodies, as w hose conseq u en ce or p h en om e­ n on w e see m otion arise.”2 Here it looks like the aforem entioned Urkraft m ight be

gravity, w hich ten ds to elim inate the spatial separation or “difference” b etw een bodies, though it is not clear how “all p h en o m en a” m ight be derivable therefrom. Pursuing his goal of defining forces b oth quantitatively and qualitatively, Mayer m easured the quantity of m otion (and also the m otive force— M ayer’s distinc­ tions ten d ed not to be very precise) as M C , the product of m ass and velocity. T he next task was to determ ine how this q u a n tu m of m otion m anifests itself, or how this m o tio n takes place, and this we com prehend u n d er th e nam e quality of m otion. T his com prehends in itself first th e energy [Energie] of th e m otion, or th e ratio of its intensity to its extensity. D eter­ m inative for it is n in th e expression -^nC , in w hich n can express any whole n u m b er and any fraction, and second th e direction of th e m o tio n ; insofar as it is only a q uestio n of diam etrically opposed directions, these can b e com pletely expressed simply in term s of th e symbols + and - . 3

C onsidering now the direction o f m otion , Mayer im agined bodies A and B (now in the absence of gravity) m oving w ith speeds c and c . If the bodies are equal (in m ass— Mayer tend ed to be careless about such specifications) and have equal speeds, th en “the total quantity o f m otive force Q = 2Ac.”4 “To determ ine the quality of ZAc w e suppose the sim plest case, that A and B m ove toward each other in a straight line; + A c is th en equal to —Be; the sym bol for the un ited body A and B is then neither + nor —, b ut 0, since A and B taken together will possess m otion neither toward th e one nor toward th e other sid e.”5 M ayer’s expression for the com bined m otion of A and B is accordingly “0 2Ac,” in w hich the zero is to be taken as a qualitative symbol (qualitatives Zeichen). A lthough confusing and idio­ syncratic, the in ten t of M ayer’s usage is clear; to recognize that even when two bodies have equal and opposite “quantities of m o tio n ” they still possess a net “m otive force.” As far as th e fu rther qualitative determ in atio n is concerned, th a t of th e energy of th e m o tion, this lies as indicated in th e determ ination of n in 0 ψηΰ; th e m agnitude of n, however, depends on th e physical co n stitu tio n [Beschaffenheit] of th e bodies involved and of th eir surroundings, especially on th e conductibility of th e substances for th e m otive force, i.e., on th e elasticity. In th e case of perfect elasticity of A an d B, n becom es = I, +A c is simply reversed into -A c, -B e in to +Be; to the degree to which th e perfection of the elasticity decreases, we see less m o tio n arise, and w ith com plete inelasticity we see th e m otion cease entirely; u n d er such circum stances a portion of th e m otive force 2Ac or the whole of it is actually w ithdraw n as m o tio n from observa­ tion; this q u an tu m , [considered] as consisting of + and —, we call neutralized. In accordance w ith th e presupposition of th e invariability of th e q u an tity of forces, th e n eutralized m otion [die Neutralisierte] is equal to th e originally present m o tio n less th a t w hich rem ains; w ith th e perfect inelasticity of A and B th e n eutralized [m otion] is = 2Ac.6

T h e m idp oint of the straight lin e representing graphically the two equal and op­ posite m otio n s— that is, the point at w hich one can im agine the neutralization of their m otion s to take place— Mayer called the Nullpunkt. If one has only a single

mass in m otion, th en one can im agine (in som e unspecified fashion) its being b rought to rest by a fixed point (durch einen festen Punkt, to paraphrase M ayer’s usage). T his fixed “zero p o in t” is capable of neutralizing th e body’s entire m otion. But two m otions can only fully neutralize each o th er if they occur along the sam e line. If they do not, their direction and m agnitude can be represented by m eans of a parallelogram of forces in which th e neutralization is given by the difference betw een the sum of th e com ponents m inus the resultant— with one qualification: “It goes w ithout saying th a t the form ation of a neutralization pre­ supposes th e existence of real m otion; accordingly, there is no neutralized com po­ n e n t of m otion [keine Neutralisierte] in statics.”7 T h a t is, applied to static forces, forces in th e m odern sense of th e word, the parallelogram of forces gives the correct result; b u t applied to dynam ics, M ayer’s inchoate science of force, the graphical resultant will be either too small or too large except for “when, as the case requires, one allows opposing m otions to becom e nought [Null] or th e requi­ site opposing m otions to arise out of n o u g h t.”8 In this passage M ayer im plied th at there are cases, as yet unspecified, in which opposite m otions can arise from nought. He w ent on: “Now since in our physical apparatus forces do withdraw them selves from our observations, b u t can never b e produced ou t of nought, the cases which are suitable for experim entation will be those in which a neutralized [m otion] is left out, never those which presuppose th e form ation of such a [m o­ tion] o u t of n o u g h t.”9 T his qualification w ith respect to experim ents th at we are capable of perform ing w ith th e usual physical apparatus again left open th e possi­ bility th at there m ight be o th er physical systems in which the restriction against th e origination of force ou t of nothing does n o t apply. M ayer closed his paper with some wide-ranging and perplexing applications of his ideas to heat, light, and th e origin of the sun’s heat and light out of th e neutral­ ization of som e fraction of th e gravitationally controlled orbital m otion of the circum am bient bodies: W e m ay be perm itted n o w to d erive from th e foregoing a few con clu sion s for physics.— Insofar as th e m o tio n does n o t actually take place in op p osite directions, th e neutralized m otion [die N eu tra lisierte] 0 2M C is the expression for heat. M otion , h eat, and, as we in ten d later to develop, electricity are phen om en a that can be re­ duced to one force, m easure each other, and pass over into each other [ineinander iibergehen) according to d efin ite laws. M otion passes over in to heat by b ein g neutral­ ized by an opposing m o tio n or by a fixed point; th e heat that arises is proportional to th e m otion that disappears. H eat, on the other hand, passes over in to m o tio n by expanding bodies; in accordance w ith its form ula 0 2M C or +JVfC-M C it produces opposin g b u t radial m otion s in all directions; th e h eated body itself remains at rest, thus the qualitative sym bol 0 pertains to it. W avelike and oscillatin g m otion s c o n sti­ tu te a special class, the transition [ Uebergang] from sim p le m o tio n to heat; insofar as they are radial, th e sym bol 0 applies to th em ; they are distin gu ish ed from h ea t, h o w ­ ever, in that w ith th em th e m otion retains all along its form as m otion; th e quantity o f th ese m otion s is likewise determ in ed by 2M C; they produce different phen om en a according to the difference in energy. In th e form ula ^ n C , as indicated above,

22

•

C Il Λ P T E R

TWO

·

expresses the energy of th e m otion; if n = ° ° {at least nearly = °o; we may be p erm itted this expression for the sake of brevity), we th u s obtain th e kind of m o tio n η

th a t makes itself known to us as light or as radiant heat. T h u s light obtains the form ula 0 2 ^ ° ° C . Light becom es heat w hen th e m otion passes over into rest, h eat becom es light w hen th e stored-up neutralized [m otion] again assumes the form of m otion. If we connect a body P w ith a fixed point c by m eans of an artificial radius vector, and if we produce a central m otion by m eans of th e m otion M C co m m unicated to P, th en M C decom poses into two m otions, of w hich one has th e direction of the periph­ ery, th e other the direction -P c; th e la tte r is continuously annihilated, neutralized, by m eans of th e fixed point c, from which one can see th a t th e [m otion] M C com m uni­ cated to P gradually becom es 0 M C in c, and th a t the m o tio n of P is th u s a decreasing m otion. In th e systems of heavenly bodies, gravitation takes the place of th e artificial radius vector; instead of there being subtracted from th e m otion M C a m otion in the direction —Pc, a like m otion is com m unicated to it from th e direction + Pc, and, by m eans of the m otive forces com bined according to th e laws of statics and dynam ics, there is obtained n o t only th e enduring revolution of th e heavenly body P, b u t there is also neutralized in c a q uan tity of m otion determ inable for each rotation. Expressed in o th e r t e r m s , t h i s m eans th a t i n th e sam e m easure as th e peripheral parts behave as falling toward the center, the latter falls toward the periphery. Accordingly, th e for us insoluble task of a continuous production of force— i.e., th e differentiation of 0 into + M C -M C — is solved by nature in the solar systems; th e fruit of which is th e m ost m agnificent [phenom enon] of th e m aterial world, th e eternal source of lig h t.10

N ote that Mayer did not specify just what happens w hen heat is produced by the neutralization of m otion. N ote, too, that his paradigm for the transform ation of heat into m otion is expansion (of a material body) conceived as m ade up o f equal and opposite (i.e., “radial”) m otions. W ith respect to his treatm ent of light, one sees in M ayer’s formula— w ith n = °° expressing ligh t’s infinite “energy” and the zero to be understood qualitatively— the use of m athem atical notation more as a sym bolic representation of his still-developing “quantitative and qualitative d e­ term ination of forces” than as a conventionally understood expression of quanti­ tative relationships. His treatm ent of planetary m otion and the attendant produc­ tion of sunlight is not only hard to make intelligible, but its clear im plication is quite at odds with the conservation of energy. Two m onths after subm itting this essay to Poggendorff, Mayer wrote to Baur that “m y first paper will contain nothing but the m ost succinct summary of the theory of th e invariable quantity of forces, the relationship betw een m otion and heat, application to the doctrine of the parallelogram [of forces], and a suggestion about the nature of light and the cause of the solar h ea t.”11 This is not a bad summary of what his paper was about, except that he in fact said very little about the “invariable quantity of forces,” lim itin g him self to the unelaborated and rather passing invocation of “the principle that forces once given, like material substances, are quantitatively invariable.” In light of M ayer’s continuing accep­ tance of the creation, under certain circum stances, of force out of nothing, the restriction of that principle to forces once given was surely not casual.

1.2 “Remarks on the Forces o f Inanimate N ature” If one next turns to M ayer’s first published paper, one encounters not only a similar constellation of issues— n ote the title ’s restriction to inanim ate nature— but also a markedly transform ed presentation, with different goals and a different argum entative strategy. Mayer began: T h e purpose of th e following lines is to a tte m p t to answer th e question of w hat we are to u n derstand by “forces,” and of how such are related to each other. W hereas w ith the designation m a tte r very definite properties are a ttrib u te d to an object, like those of w eight and of filling space, th e designation force is associated principally with th e concept of the unknow n, th e inscrutable, th e hypothetical. C onsidering th e con­ sequences flowing from it, an a tte m p t to u n derstand th e concept of force as precisely as th a t of m atter, and to designate thereby only objects o f actual investigation, should n o t be unw elcom e to friends of a clear, hypothesis-free view of nature. Forces are causes, thus the principle causa aequat effectum applies fully to th em . If th e cause c has th e effect e, th e n c = e; if e is in tu rn th e cause of an o th er effect f, th en e = f, etc. [and] c = e = f . . . — c. As is clear from th e n atu re of an eq u atio n , in a chain of causes and effects a link or a part of a link can never becom e nought. T his first property of all causes we call their indestructibility.12

O nce again at th e center we find th e attem p t to elaborate a doctrine of force as ontologically coequal to matter. Here, however, Mayer tied his con cep tion of force m ore explicitly to a general principle of causality: the indestructibility of forces was a logical necessity. If m atter and force— or, more precisely, material substances and forces— were before once referred to as the “objects” studied by chem istry and physics, here the repeated reference to forces as “objects” lent that word a more substantive quality. Mayer w ent on: Since therefore c passes over into e, e into f etc., we m u st thus regard these m agni­ tu d es as different m anifestations [Erscheinungsformen] of one and th e same object. T h e ability to be able to assum e different forms is th e second essential property of all causes. S um m arizing b o th properties, we say th a t causes are (quantitatively) inde­ structible and (qualitatively) transformable [or m utable (wandelbar)] objects. Two classes of causes are found in nature, betw een which experience shows no transitions to take place. O ne class com prises causes possessing th e property of p o n ­ derability and im penetrability— i.e., m aterial substances [M aterien]; th e other, causes lacking th e la tte r property— i.e., forces, also called im ponderables after th eir charac­ teristic negative property. Forces are thus indestructible, transformable, imponderable objects .13

C onsidering first m aterial substances, Mayer reasoned that "explosive gas [Knallgas], H + 0 , and water H O are related to each other as cause and effect, thus H + O = H O .”14 H e insisted at length on the force o f the analogy betw een material substances and forces as quantitatively indestructible and qualitatively variable objects, each to be understood in term s of the cause-and-effect relation-

ships a m o n g th e ir various m a n ife sta tio n s. H e was now ready to specify w h a t som e of th o se forces were: A cause that brings about the raising of a weight is a force; its effect, the raised weight, is thus likewise a force; expressed more generally this means th a t the spatial difference o f ponderable objects is a force; since this force brings about the fall of the body, we thus call it fallforce. Fallforce and fall, and more generally still fallforce and motion, are forces related to each other as cause and effect, forces that pass over into each other, two different manifestations of one and the same object.15 In arg u in g ag ain st th e g en eral p ra c tic e of calling gravity a force, M ayer m ad e an essen tial d is tin c tio n b e tw e e n forces a n d p ro p erties: W hen one regards gravity [Schwere] as the cause of fall, one speaks of a force of gravity [Schwerkraft] and thereby confuses the concepts of force and property; pre­ cisely that which belongs essentially to every force, the union of indestructibility and transformability [Wandelbarkeit], is foreign to every property; between a property and a force, between gravity and m otion, one can therefore also not set up the equation necessary for a correctly conceived causal relationship. If one calls gravity a force, one thereby imagines a cause which, w ithout itself diminishing, produces effect, and one thereby thus entertains incorrect notions [Vorstellungen] about the causal connection of things.16 In calc u la tin g th e m a th e m a tic a l re la tio n sh ip b e tw e e n fallforce a n d m o tio n , M ayer m ad e o n e o f his usual m istak es w ith even th e sim p le st c o n c ep ts of m a th e m a tic a l physics, w ritin g “v = m d = m e2” for th e force v of a b o d y of m ass m falling th ro u g h h e ig h t d to acquire velocity c. H is co n clu sio n was th a t “w e find th e law of th e co n serv a tio n of vis viva to b e g ro u n d e d in th e general law of th e in d e stru c tib ility o f c a u se s.”17 H ow ever, M ayer o th erw ise a lm o st never u se d th e w ord E rhaltung, an d h e d id n o t regularly invoke th e analogy b e tw e e n his principle of force a n d th e co n serv a tio n of vis viva— in p a rt, it w o u ld seem , in order to em p h asiz e th e origi­ nality of his th eo ry of force. T h e h e a rt of M ay er’s p a p e r follow ed: th e e s ta b lish m e n t of th e eq u iv alen ce, as forces u n d e rsto o d as causes, of h e a t a n d m o tio n . H e argued th a t we regularly observe h e a t to be p ro d u c e d as m o tio n disap p ears, an d are th u s forced to recog­ n ize a causal c o n n e c tio n b e tw e e n th e two. N o n eth ele ss, M ayer was careful to d ista n c e h im se lf from th e m o d e -o f-m o tio n th e o ry o f h e a t— die therm ische Vibrationshypothese, as h e te rm e d it— b e c a u se it places th e em p h asis on “d isco m fo rt­ ing v ib ra tio n s” (unbehagliche Schw ingungen) .18 H e a tte m p te d to illu stra te th e re­ la tio n s h ip b e tw e e n fallforce, m o tio n , a n d h e a t b y m ea n s of a curious analogy: We can make clear to ourselves the natural connection existing between fallforce, motion, and heat in the following way. W e know that heat appears when the individ­ ual massy particles of a body move closer to each other; compression [or densification (Verdichtung)] produces heat; now, what holds for the smallest massy particles and the smallest spaces between them m ust well also apply to large masses and measur­ able spaces. The descent of a weight is a real reduction in the volume of the earth, and

thus m u st certainly also stand in co n n ectio n w ith th e heat that thereby appears; this heat m u st be exactly proportional to th e size of th e w eigh t and its (original) distance. From this consideration on e is led q u ite easily to th e above-discussed equation of fallforce, m otion , and heat. N evertheless, as little as can be d educed from th e co n n ectio n existing b etw een fallforce and m otion that th e essen ce o f fallforce is m o tio n , so little does this co n clu ­ sion hold for heat. W e w ould rather con clu d e the op p osite, that in order to be able to b eco m e h eat, m otio n — be it a sim ple or a vibratory m o tio n like ligh t, radiant heat, etc.— m ust cease to b e m o tio n .19

In order for the equation between fallforce, motion, and heat to be valid, we m ust also be able to transform heat into motion and fallforce: “Just as heat arises as an effect in cases of reduction in volume and of motion coming to an end, so heat disappears as a cause with the appearance of its effects: motion, increase in vol­ ume, raising of a weight.”20 It was the relationship between the change in volume of a compressed gas and the heat thereby produced that provided Mayer with both the mechanism and the data necessary to calculate the all-important num er­ ical equivalence between fallforce and heat: “T hat such an equation is really grounded in nature can be regarded as the resume of the foregoing.”2* W ithout indicating his m ethod of derivation in the published paper, Mayer asserted “that the fall of a given weight from a height of around 365 meters corresponds to the heating of an equal weight of water from 0° to I 0.”22 It is primarily upon the publication of this num ber that Mayer’s claim to discovery of the conservation of energy has been based.

2 T

he

L e a d in g Id e a s

and

P e c u l ia r it ie s

of

M

a y e r 's

W

ork

2.1 Force 2.1.1 T H E ANALOGY W ITH MATTER

As Heimann rightly emphasized, “the kernel of Mayer’s thought is his concept of force and his theory of the relations between forces, and its understanding is essential to our comprehension of Mayer’s fundam ental intentions. It is this kernel th at is obscured or distorted by the search for correspondences and con­ nections between Mayer’s ideas and those of other ‘pioneers’ of energy conserva­ tion.”23 As abundantly demonstrated in the passages quoted above, the most es­ sential properties of force for Mayer were its indestructibility, its transformability or mutability (Wandelbarkeit), and its immateriality. Although in both his unpub­ lished essay and in contemporaneous letters to Baur he occasionally spoke in gen­ eral terms of, for example, “the principle of the invariable quantity of forces,”24 Mayer for the most part stressed only the indestructibility, not also the uncreatability of force, since he continued for several years to accept the production of force in certain nonmechanical systems. The first decisive assertion of the uncreatability of force came in the the unpublished version of what became his second publication, Organic Motion in Its Connection with the Exchange o f Matter

(1845). In th e m anuscript, which probably dates from late 1844 or early 1845, Mayer introduced th e principle by m eans of a chem ical analogy: “Sulfur and m er­ cury stand in such a genetic relationship to cinnabar; w ater is transform ed into steam or ice, etc.; all and sundry chem ical processes consist of changes in the form of given objects, whereby som ething expended always stands in th e closest ge­ netic relationship to som ething newly form ed.”25 He th en followed th e categorical statem en t “Ex nihilo nil fit”— its first appearance in his writings— w ith the asser­ tion, “T here is no reason to restrict this axiom to ponderable m atter.”26 T h e anal­ ogy betw een m aterial substances and forces was now com plete: b o th were rigor­ ously invariable in quantity. M ayer’s conception of the m utability and im m ateriality of force illustrates the degree to w hich he evolved his very concept of force by contem plating its relation­ ship to ponderable m atter and th e so-called im ponderables. T he likelihood of such an evolution in M ayer’s thinking will be gone into at length in chapter 6; here I simply call atten tio n (with H erm ann)27 to th e consistency w ith which Mayer expounded his conception of force in term s of an explicit analogy w ith m atter, w hich is similar to force in its q uantitative constancy and qualitative m utability, b u t unlike it in its materiality. Such was th e case no t only in the writings he published or in ten d ed to publish, b u t also in his correspondence. In his first letter to Baur h e wrote: T h e ch em ist holds firmly to th e principle th at substance [Substanz] is in d e­ structible, and th at th e com p osin g elem en ts and th e com p ou n d form ed stand in the m ost necessary con n ection ; w hen H and O disappear (b eco m e q ualitatively 0 [i.e., Null]) and H O appears, th e ch em ist may n o t thereby assum e that H and O really b eco m e 0, and that th e form ation of H O is so m eth in g accidental or nonessential; m odern chem istry dep en d s on th e strict carrying ou t o f this principle, w hich clearly alone could lead to w ell-rounded results. W e m u st apply exactly the sam e principles to forces; they, like substance, are also indestructible; they, too, com b in e w ith on e another, disappear accordingly in their old form (b ecom e qualitatively 0), and appear instead in a new form , [hence] th e co n n ec­ tion b etw een the first and th e secon d form is every b it as essential as that b etw een H and O and HO. . . . A m otion + M C neutralized by an equally great directly opposing m o tio n -M C yields, becau se b o th m otion s (like substance) are quantitatively invariable, 2M C , but w ith the sym bol (qualitative d eterm in ation ) O.28

Drawing upon a term M ayer’s concept of force reading of M ayer’s words, overall system was rather

used in one of M ayer’s letters, H eim ann has called “the ‘axis’ of a new science of physics.”29 T h a t is a fair b u t they can also be read as m eaning th a t the axis of his the m atter-force analogy:

I will attem p t first of all to exhibit to you th e axis of m y system ; w ith it stand in co n n ection upwards speculations on th e nature of m atter and force, downwards the explanation of th e p h en o m en a of nature; this axis was im plied “in th e ,” as you write,

“com parison betw een th e chem ical neutralization o f the elem en ts and th e m ech an i­ cal annihilation o f th e opposing forces.” It is th e sam e w ith the theory of forces (physics) as w ith th e theory o f material substances (chem istry); b oth m u st be based on the sam e principles. . . . M y first en ­ deavor is now to secure the axis about w hich rotates th e theory o f material substances for th e theory o f forces as well; from th en ce is dated [daher d a tiert sich\ the axiom of th e invariable quantity of forces.30

In ways to be elaborated in chapter 6, I fully agree with H eim an n ’s assessm ent th a t “th e analogy he had drawn betw een chem istry and physics— the form er as th e science of m atter, the latter as th e science of force— was not merely a heuristic m etaphor, b u t expressed a fundam ental feature of his conception of nature: n a ­ ture co n stitu ted a duality of m atter and force.”31 T h a t M ayer’s exploitation of this analogy was a creative act in its own right is underscored by the fact th a t one side of it— th e indestructibility, uncreatability, or conservation of m atter— was no t a principle explicitly stated in either th e chem istry or physics texts of M ayer’s day; hence Mayer had to do m ore th an simply apply to forces som ething he obviously ‘knew ’ about m aterial substances. 2 I 2 T H E CENTRALITY OF HEAT AND M OTION

Som eone who approached M ayer’s work after having studied the o th er nom inal codiscoverers of th e principle of the conservation of energy and their context would probably be struck by how u n im p o rtan t virtually all the m any examples of th e interconvertability of the different forms of energy were to Mayer. H e drew on a few for illustrative examples here and there, b u t for th e m ost part his em phasis was on heat, m otion, and th e spatial separation of m atter (the last, his “fallforce,” primarily as a source of m otion), with lim ited and undetailed (though conceptu­ ally im portant) inclusion of light and sound (regarded as vibratory m otions), elec­ tricity and (still less often) m agnetism , and (occasionally) the “chem ical differ­ ence of m atter.”32 His in ten tio n of applying his conception of the quantitative and qualitative definition of force to electricity did not bear significant fruit, and he had virtually nothing to say on th e topic.33 Only in 1845 did M ayer elaborate a reasonably inclusive catalog of forces and their interconnections.34 T he voltaic battery, O ersted ’s and Faraday’s experim ents on electrom agnetism and electro­ m agnetic induction, therm oelectricity, photography— none of these seem to have had any appreciable significance for h im .3S Nor was there ever talk in M ayer’s writings of any grand unity of the forces of nature, although th at is w hat his work clearly im plied. At th e cen ter of M ayer’s thinking, then, was no t a broad notion of the intercon­ nections am ong various forces b u t a conception of the equivalence of h eat and m otion. It was n o t for nothing th a t he chose to call his collected works The M e­ chanics o f Heat. W riting to the Paris Academ y in 1848, w hat he claim ed to have discovered in 1840 was “the law of the equivalence of m echanical work and

h e a t”— though, to be sure, in 1840 he would no t have spoken of “work” b u t of “m o tio n .”36 In one of his autobiographical sketches he wrote of his return to Heilbronn from Java, “filled w ith the idea th a t had becom e clear to him on this voyage th a t m otion and h ea t are only different m anifestations of one an d th e same force, and th a t consequently m otion or m echanical work and heat, which had hitherto m ostly been regarded as entirely disparate things, m u st also be able to be con­ verted and transform ed into one another.”37 W henever M ayer specified just what it was he had discovered, it was the interconvertibility or eqivalence of h eat and m o tio n — in o th er words, the m echanical theory of h e a t.38 2.1 3 TH E NATURE O F HEAT (IN PARTICULAR) AND FORCE (IN GENERAL)

D espite th e fact th a t central to M ayer’s entire thinking was th e equivalence of h ea t and m otion, he nevertheless explicitly opposed reducing h ea t to m otion. H eat and m o tio n were causally connected via a q uantitative m easure of their equivalence, b u t, aside from their bo th being forces, they were no t to be assum ed identical in essence. T his reluctance to em brace th e m ode-of-m otion theory of h eat was apparently fueled by several reinforcing considerations. In th e first place, M ayer was deeply opposed to m aterialism , and since classical m aterialism recog­ nized th e existence of only m atter in m otion, his doctrine of force and his refusal to em brace th e m ode-of-m otion theory of h eat can be seen as a denial of one of th e central com ponents of the m aterialist worldview.39 Second, in M ayer’s day forces were regularly defined as properties of m atter, whereas he was concerned to vindicate for his forces an existence independent of m atter.40 Perhaps he reasoned th a t taking h ea t to be nothing m ore than th e m otion of th e sm allest parts of m a tte r w ould risk m aking it no m ore th an a property of m atter, dep en d en t on the latter for its existence. Finally, M ayer consistently declined to speculate about the essence of force in general, preferring instead to rest w ith having identified it conceptually vis-a-vis m atter, having used it to explain the connections betw een previously uncon­ n ected phenom ena, and having determ ined the equivalence of heat and m otion. For th e rest, he professed him self to be ontologically agnostic: I d o n ’t know w hat h ea t, w hat electricity, etc., is as regards its internal essen ce, as little as I also know th e in tern al essence of a m aterial su bstance or of anything at all; b u t I do know that I see th e co n n ectio n betw een m any phen om en a m uch m ore clearly than one has before, and that I can give clear and good con cep ts for w hat a force is. If one stops speaking o f gravitational force and chem ical affinity as causes o f p h en o m ­ ena— i.e., if on e wrests th e n am e force from such things that are n ot forces— one thereby com es to th e study o f anim ate nature w ith healthfully purified concepts; one knows, am ong other things, w hat can and m u st b e charged to th e accou n t o f the forces o f in anim ate nature, and th e vital force, the nervous force, thereby again loses considerable ground, and the babblings of th e N aturphilosophen stand pilloried in pitiful nakedness. *

*

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How heat arises out of th e disappearing m otion, or as I p u t it, how m otion passes over into heat— to d em and clarification on those m atters would be to dem and too m uch of the h um an m ind. How th e disappearing O and H yield water, why a sub­ stance with other properties doesn’t perhaps arise— no chem ist will likely break his head over such m a tte rs.·11

It seems th a t Mayer tended to think of h ea t phenomenologically, in term s of its sensible m anifestations— in particular, th e m acroscopic expansion of heated b o d ­ ies— and not in term s of the im aginable m otion of unseeable particles. As in the above-quoted passage, w hen Mayer m entioned th e com bustion of oxygen and hydrogen to form water he seems to have been thinking of th e transform ation of m acroscopic quantities of th e reactants, n o t of an im agined m olecular reaction, although he otherwise accepted chem ical atom ism . In his published works M ayer liked to invoke an im age of positive science to justify his refusal to identify heat w ith m otion: If a transform ation [Verwandlung] of h ea t into m echanical effect has here been posited [sta tu irt], th en it is only to express a fact, b u t n o t in any way to explain the transform ation itself. A given q u an tu m of ice can be transform ed in to a corresponding am o u n t of water; this fact stands firm and indep en d en t of fruitless questions over How and W hy and of em pty speculations over the u ltim ate cause of the states of aggregation. G enuine science is satisfied w ith positive knowledge and willingly leaves it to th e p oet and th e Naturphtlosoph to a tte m p t th e solution of eternal riddles with th e help of fantasy. #

Ψ

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In th e exact sciences one deals w ith th e phenom ena them selves, w ith m easurable quantities; b u t th e original cause fOrgrund] of things is an entity [Wesen] eternally inscrutable to h u m an understanding— th e divinity [or G odhead (G o tth eit)]—-while “higher causes,” “supersensible forces,” and th e like belong w ith all their conse­ quences to th e illusory m iddle kingdom of Naturphilosophie and m ysticism .42

Typically, as here, M ayer’s declam ations against Naturphilosopkie cam e when he w ished to defend his own refusal to speculate about essences. Similarly defensive

of his stance on th e nature of h ea t was his assertion th a t there are natural limits to h u m an knowledge in the direction of b o th th e infinitely small and th e infinitely large.43 W h atev er th e reasons for M ayer’s disinclination to accept the m echanical th e ­ ory of h eat, despite his fixation on the equivalence of heat and m otion, this nonacceptance h ad profound im plications: it was only M ayer’s rejection of both contem porary conceptions of heat, w hether im ponderable fluid or the m otion of th e ponderable particles of m atter, th at in a sense drove him to seek a new con­ ceptualization of the n ature of force. His aim was to dem onstrate the legitimacy of a new and ontologically distinct entity, no t— like H elm holtz— to validate a m ore traditional reductionist explanation based on m atter and Newtonian-style forces.

M ayer’s trea tm e n t of light was curious, though entirely in keeping with his conception of heat. As he wrote to Baur in 1841: As regards light, from th e internal necessity of my system I have to ad o p t th e vibrations theory. . . . Voyez-vous, the essence of light is m otion, its particular species wave m otion; light is thus a p h enom enon entirely analogous to sound. L ight th u s does n o t consist in th e m ysterious vibrations of a m ysterious fluid, an d its relationship to h ea t is n o t m ysterious. . . . [OJnly m otion w hich is lost th ro u g h resistance will becom e h eat. . . . As is well known, optics is able to base all th e laws of th e m otions of light on th e vibrations theory, whereas chem istry was all the m ore unsatisfied w ith th e theory since it left in the dark th e relationships th a t had to be th e m ost im p o rtan t for it— light w ith h ea t, light w ithout h ea t, radiant h ea t— and for this reason I myself was also very m uch disposed against it until th e point in tim e where my theory needs in­ structed m e th a t light could not be anything at all b u t m o tio n , whereby th e latter questions also solved them selves for m e with com plete clarity.44

M ayer th u s insisted th at light was a rapid vibratory m otion while he denied the existence of a substance, an im ponderable fluid or some kind of lum iniferous aether, th e vibrations of which m ade such a theory conceivable, at least according to the u n derstanding of contem porary physicists: if light is a wave phenom enon, it has to be a wave o f something. Mayer kept th e waves b u t rejected the som e­ thing. T h en , too, his notion th at chem ists opposed th e vibrational theory of light because it cannot account for radiant heat strangely m isrepresented w hat was for m any th e m ost com pelling evidence for vibrational theories of both light and heat. In his book of 1845 M ayer did n o t even include light in his table of forces except im plicitly u n der “II. M otion. A. simple. B. undulatory, vibratory.”45 Am ong th e exam ples illustrating th e twenty-five types of "m etam orphoses” possible am ong his five basic forces— whereby electricity and m agnetism (considered as one species of force) and heat were labeled “im ponderables”— was th a t “th e ab­ sorption of light consists in a transform ation of vibratory m otion into h e a t.”46 O nce again, however, he never even h in ted at w hat light m ight be the m otion of. Perhaps he co n ten ted him self w ith th e same kind of ontological agnosticism th at characterized his u nderstanding of heat. 2.1.4 T H E STATUS O F IMPONDERABLES, FORCES AS OBJECTS

T h e th ru st of M ayer’s innovation can b e seen as a reinterpretation of th e nature of th e entities th a t physicists of his day com m only called “im ponderables,” the weightless substances (often called fluids) responsible for the p henom ena of heat, light, electricity, and m agnetism .47 To th a t class of substances (or phenom ena) M ayer applied th e reinterpreted word “force,” which, he urged, should n o t be used for th e properties of m atter (such as gravity), b u t which should be reserved for th e class of things (including, crucially, m otion and th e spatial separation or “difference” of heavy bodies) th a t act as causes (of m otion or o th er changes in th e physical world). He insisted th a t th e n otion of im ponderable fluids, which m ight appear to make sense in the case of heat or electricity, was obviously inapplicable

to either m otion or th e raising of a weight and thus th a t this notion was generally inadm issible for the new class of objects he term ed forces.48 T h at, at least, is a sim plified version of M ayer’s intentions. In fact, however, despite th e suprem e im portance he (usually!) attached to his new conception of force, he con tin u ed to use the word “im ponderables” for his new class of objects. In his first published paper, as we have seen, he defined forces as th e class of causes which (unlike m atter) lack th e properties of ponderability and im penetra­ bility, and th en added as a gloss on th e term : “from their characteristic negative property also called im ponderables.”49 W e may, he argued, reasonably apply the word im ponderables to “indestructible, transform able, im ponderable objects . . . whose objectivity is likewise [as with ponderable objects] verified through experi­ ence (at least as well as w ith ponderable).”50 Indeed, in his letters of 1842 he spoke of im ponderables m uch m ore often than of forces.51 For example, in M ayer’s nine-page letter of 5/6 D ecem ber 1842 to Griesinger, in which his aim was to convince his still-skeptical friend of the justice of his new theory, the word “force” appears only once, in a direct quote from Liebig’s letter accepting his paper for publication, whereas he spoke of “im ponderables” no fewer than nine tim es. Part of M ayer’s difficulty with Griesinger was in getting him to see the crucial distinc­ tion betw een th e im ponderables, now including also m otion, and th e properties of m aterial substances. He concluded an extended discussion of th a t distinction with th e following words: If, on the other hand, on e wants a practically correct mark o f d istin ction b etw een im ponderables and (other) properties [of material su bstances], I would set th e task of transplanting th e w eight, yellow color, or shape of a gold coin to a piece of silver . . . , as in general its m otion , etc., can b e transplanted to another material substance. I have treated the last subject som ew hat extensively here because it is of special im portance to m e that we co m e as m uch as possible to an understanding w ith respect to the con cep t of “im p on d erab les.”52

Mayer was largely unsuccessful in countering G riesinger’s objections to th e inclu­ sion of m otion am ong the im ponderables, which Griesinger persisted in seeing as subtle fluids, or in getting him to appreciate the distinction betw een im ponder­ ables and th e properties of m atter.53 He responded to G riesinger’s intransigence in th e following terms: You write further: “To b e sure, you do not say that m otion and im ponderables are the sam e, b u t you le t th e latter arise out of th e former.” But this is just th e fundam en­ tal and cardinal idea: m o tio n is an im ponderable, every bit as well as is heat. Cf. p. 234 [of m y paper in Liebig’s Annalen], where in the defin ition I declare forces and im p on ­ derables to be one and the sam e, and p. 235, lin e 21, where I say: “Fallforce and m otion are forces,” etc. My assertion is indeed precisely that fallforce, m otion , heat, light, electricity, and the chem ical difference of th e ponderables are one and the sam e object in different m anifestations. T h u s w ith ou t disputing over words, w hen I call one o f these things an im ponderable it is thereby clear that I ascribe th e nam e to the others as well.

W hy [do] I also call this class of things “forces”? T h a t is in deference to linguis­ tic usage; as far as I am acquainted w ith th e m , th e G erm an, French, and English writers on science all agree w ith one an o th er th a t causes w hich produce a m o tio n are forces.,+

It appears, th en, that for a w hile Mayer wavered as to w hether he should em ploy the term “force” or "im ponderables” for his new class o f objects. In 1842, at least, he leaned decidedly toward the latter. Perhaps it was G riesinger’s objections that induced h im ultim ately to elaborate a theory of forces. A lthough in his published writings he largely settled on force, after ten years he was still occasionally refer­ ring to his subject as a “theory of th e im ponderables,”55 and in 1862, after the conservation of energy had been recognized and accepted, he could still write: Physics has recently acquired a substantial en rich m en t th ro u g h th e discovery of the law “of the indestructibility of force.” .. . T his law says in essence th a t h eat, m otion (i.e., th e so-called living force or “work” o f th e m echanicians), as well as light and electricity are different m anifestations [Erscheinungsform en] of one an d th e same indestructible, m easurable object, so th a t, for exam ple, m o tio n can b e transform ed in to h eat and th e la tte r in tu rn into the former, whereby in every case th e quantitas vis in play rem ains constant. As an im ponderable, h eat is accordingly at th e sam e tim e also a force; as a (living) force, m otion is an im ponderable; or in general: forces and im ponderables are synonym ous co ncepts.56

M ayer’s term inological attachm ent to im ponderables may have som eth in g to do with another of his characteristic usages, nam ely his repeated reference to forces as ob jects.57 As suggested in o n e of the passages qu oted above, Mayer may have thou gh t that using this term was equivalent to asserting the objectivity, the reality, of force. It is probably also significant that his use of this term stood in close co n n ection w ith the way in w hich h e forged his concept o f forces/im ponder­ ables by reflecting on their sim ilarities and differences w ith respect to ponderable matter: Aside from th e ponderables, however, there are still o th e r objects (im ponderables) w hich are likewise subject to th e above law [i.e., th a t no given m aterial substance ever becom es n o th in g (zu N u ll wird) and none com es into existence o u t of nothing]; . . . such an object w hich is n o t m a tte r (an im ponderable) is m otion; it does n o t com e in to existence out of nothing, insofar as it m u st always have its cause, b u t, having once com e into existence, it no longer becom es n o th in g because no cause can be conceived to have n o th in g as its effect [mit der W irkung Null], T h u s we know th a t m o tion is one m anifestation of an object th a t is n o t m atter; it com es in to existence o u t of an o th er m anifestation and, insofar as it ceases to be m otion, becom es an ­ o th er m anifestation of th e sam e im ponderable object. In o th e r words, th e cause of m otion, th e m otion itself, and its effect are no th in g b u t different m anifestations of one and th e sam e object, just as th e sam e can be said of ice, liq u id water, and steam . But just as steam can again becom e water, w ater again ice, so, too, w ith m o tio n and its causes and effects; cause and effect designate nothing a t all b ut different m anifesta­ tions o f one and the same object. . . . A kilogram ’s having been raised five m eters and

the motion of such a weight with the speed of ten meters a second are one and the same object.58 In his boolc of 1851 he w rote th a t b o th m o tio n an d h e a t arise as a result of th e “ex p e n d itu re of a m easu rab le o b je c t,” a n d th a t his th eo ry regarding th e tran sfo r­ m a tio n of m o tio n in to h e a t req u ired an invariable q u a n tita tiv e p ro p o rtio n a lity b e tw e e n th e se tw o “o b je c ts.” In th e sam e vein he referred to a raised w eight and a m o v in g b o d y as “o b je c ts.”59 R a th e r th a n calling forces objects, M ayer la te r so m etim es spoke of th e "su b ­ sta n tia lity ” of force, by w hich he seem s to have m e a n t little m ore th a n th a t th ey exist, w ith th e a ssu m p tio n th a t w h atev er o n ce exists c a n n o t cease to exist.60 T h u s h e w rote th a t, w hen a given m ass has b e e n raised to a given h e ig h t, “one has th u s a force w hich, like m o tio n , has su b stan tiality , or th e pro p erty of existing, or w hich can never b eco m e n o u g h t.”61 H ere, too, M ayer characteristically ap p ea led to th e favored analogy w ith m a tte r; in th e sh o rt b io g rap h ical n o te h e co m p o sed on h im ­ self for th e B rockhaus encyclopedia, h e w rote th a t h e was th e first person “w ho e n u n c ia te d an d ela b o ra te d th e principle th a t n o t only m atter, b u t also living force in its d iffe re n t form s— th a t is, m o tio n , h e a t, lig h t, a n d electricity— possess th e su b sta n tia l p ro p erty of q u a n tita tiv e in d e stru c tib ility .”62 W h ile in sisting on th e su b sta n tia lity of m o tio n , M ayer a t least occasionally recognized th a t it was m is­ lea d in g a n d in a p p ro p ria te to call m o tio n an im p o n d erab le: W hile we loudly vindicate for motion the right to exist, [i.e.] substantiality, we m ust absolutely deny any materiality to heat and electricity. For would it not be really absurd to seek the essence of motion and of the spatial separation of masses in a fluid, or to wish to posit an alternately now-material, now-immaterial existence for one and the same object? Let us proclaim the great truth: “There is no immaterial m atter!” We sense indeed that we have gone into battle against the most deeply rooted hypotheses, canonized by great authorities, and that we wish to banish with the im­ ponderables the last remnants of the Greek gods from science.63 O f course, M ay er’s brave rh e to ric belies th e stre n g th of his ow n a tta c h m e n t to th a t o u tm o d e d co n c e p t. In d e e d , it is highly possible th a t M ayer c o n s titu te d his co n c e p tio n of force— in p a rtic u la r its in clu sio n n o t only of h e a t, b u t also of light, electricity, a n d m a g n e tism — in th e first in sta n c e via a n o tio n of th e su b sta n tia lity it shared w ith th e erstw hile im p o n d erab les. A fter all, in M ayer’s day th e la tte r were only rarely spoken of as forces. 2.2 N eu tra liza tio n o f Differences; The C o n tin u ed im portance o f C hem ical Analogs O n e of th e striking usages of M ay er’s first (u n p u b lish e d ) paper of 1841 is th e langu ag e of th e “n e u tra liz a tio n of d ifferen ces,” w hich h e applied to th e cancelingo u t of o p posing m o tio n s, to th e e lim in a tio n of th e spatial sep aratio n (raum liche D ifferenz) b e tw e e n b odies, an d to th e q u a lita tiv e ch an g e w hich tw o reacting

chem icals undergo in form ing a new substance. A lthough the first and (especially) th e second application of the phrase are som ew hat idiosyncratic, the third has close parallels in chem ical terminology, m ost obviously to th e neutralization of acids and bases. Yet it was no t until 1844, in his correspondence, th a t Mayer referred explicitly to the neutralization of acids and bases as an analog to the neutralization of opposing m otions.64 His first public reference cam e the next year: “Just as m aterial substances of opposite quality, an electropositive base and an electronegative acid, neutralize each other, so do m otions of opposite (positive and negative) direction together annihilate each other. T he given th a t continues to exist in changed quality b u t in unchanged quantity is there th e neutral salt, here h e a t.”65 In M ayer’s earliest writings his favored exam ple was consistently the co m bination of oxygen and hydrogen to form water.66 H e also occasionally re­ ferred to th e “sacrificing of th e chem ical difference of C and O ” whereby m otion is produced in a steam engine 67 A powerful analogy for him was th a t betw een th e chem ical doctrine of equiva­ lents and com bining weights and his developing conception of force. Indeed in 1863, in a letter to John Tyndall, he glossed th e “theory of the conservation of force” as th e theory of “physical stoichiom etry,” and in an encyclopedia entry he com posed ab o u t him self ten years later he wrote th a t his first task had been to d eterm in e th e constant relationship betw een work and h eat— the m echanical equivalent of h eat— “and thereby to lay the foundation for a kind of physical stoichiom etry.”68 T he image probably first suggested itself to him as he pondered th e sim ilarities and differences betw een chem ical and physical “neutralization.” In a letter to Baur in 1842 he noted th a t different weights of different substances are required to neutralize th e sam e weight of a given substance. For exam ple, it requires eight parts of oxygen or thirty-five parts of chlorine to neutralize one part of hydrogen: “If we ponder this it will no t appear strange th at, for diverse m otions, likewise different m asses are required for neutralization, or th a t to annihilate, to neutralize, a given m otion by m eans of an o th er m otion of different energy no t the sam e q u an tity of th e second should be required as of th e first.”69 T h u s th e m otion of a body of mass m and speed c can be neutralized by a body of mass ψ and speed xc, yet th e q uantity of m otion of th e first body is given by me2, th a t of the second by ψ(χο)2 = xmc2. In o th er words, chem ical and physical substances (or bodies) th a t neutralize each other are n o t necessarily equal in th eir quantity of mass or m otion. As he p u t it, “I believe I have m ade clear by m eans of the analogy w ith th e com bining weights of m atter th a t from th e fact th a t opposite m otions of m, speed c and of ψ, speed xc are capable of annihilating, of neutralizing each other, the conclusion is in no way p erm itted th a t such m otions are equal in quantity.”70 Part of w hat M ayer was involved w ith here was trying to reconcile his doctrine of th e neutralization of m otion w ith a m easure of th e quan­ tity of m o tio n equal to mv2 instead of th e mv he used initially, and which he co n tin u ed to use now and th e n for at least another two years. Perhaps one of the reasons he never elaborated this stoichiom etrical analogy in any detail in his p u b ­ lished works was th a t h e could never m ake consistent sense of the proper m easure of th e q u an tity of m otion. In responding to criticism s th a t Baur had m ade on a

long m an u sc rip t he h a d sen t h im in 1844, M ayer w rote: “O n page 45 I said: T o r th e n e u tra liz a tio n of m o tio n s th e velocity plays th e role of th e co m bining w eig h t.’ In stead of velocity you w ant to p u t me. I have calculated here as follows: W h e n an acid an d a base n eu tralize each other, th e ir m ag n itu d es (weights) are p roportional to th e ir co m b in in g w eights; w hen tw o o p posing m o tio n s neu tralize each other, th e ir m ag n itu d es (w hich I, like L eibniz, m easure by m e2) are proportional to th eir velocities.”71 T h e u ltim ately p u b lish ed work, his book of 1845, o m itte d all m e n ­ tio n of such an analogy. As has b e e n ab u n d a n tly clear, M ayer’s th o u g h ts on forces owed a great deal to chem ical analogies. Significantly, m ost of th e chem ical topics of greatest im por­ tan ce to M ayer— th e oxygen theory of respiration, th e q u a n tita tiv e d e te rm in a tio n of m ass an d th e assertion of its conservation, and th e co m position of w ater from oxygen and hydrogen— were associated w ith th e work of Lavoisier, and it is n o t a t all far-fetched to im agine th a t M ayer fancied he w ould do for physics w hat h e supposed Lavoisier h ad d one for chem istry: T h e chem ist is perm itted to determ ine his objects of investigation directly by m eans of the balance. However, chem istry only becam e a science a hundred years ago w hen Lavoisier succeeded in discovering the invariable quantitative relations existing betw een the different elem ents, w hich one calls com bining w eights and th e knowl­ edge of w hich one calls stoichiometry. As is well known, Lavoisier got there by discov­ ering the com position of water, which consists of one part by weight of hydrogen and eight parts by w eight of oxygen, or one part by volum e of hydrogen and sixteen parts by volum e of oxygen [sic]. Such invariable quantitative relations as here for water— thus, for exam ple, here th e ratio 1:8— exist, however, for all other substances both sim ple and com pound, and it was the knowledge o f th ese invariable numerical ratios that first raised chemistry to the rank of a science.72

M ayer h a d b e g u n this m an u scrip t frag m en t by citin g his calculation, tw enty-eight years before, of th e m ech an ical eq u iv alen t of heat. 2.3 C ausality and the Law s o f Thought A lthough th e p articu lar form o f his arg u m en t changed, co n sta n t in M ayer's pre­ sen tatio n of his ideas was his id en tificatio n of forces as causes a n d his appeal to th e law of sufficient reason, to w hat he te rm e d “das G esetz des logischen G ru n d es” or words to th a t effect, as proof of th e in d estru ctib ility of force.75 As we will see in c h a p te r 4, th e id en tificatio n of forces as causes was com m o n p lace in th e physics of th e day. However, his in te rp re ta tio n of th e law o f sufficient reason, a law of thought, as applying n o t to th e logical process of draw ing correct inferences b u t to th e necessary existence of a physical cause for every event, represented a m isu n d e rsta n d in g of logic th a t reflected M ay er’s lack of grounding in form al p h i­ losophy a n d his m isco n stru al of th e am biguous G erm an word G rund, w hich m eans b o th “reason” an d “cause.”7'1W h e th e r or n o t h e was confused, M ayer was convinced his conclusions were san ctio n ed by th e laws of th o u g h t, or at least h e argued th a t way. As h e explained to Baur, his d em o n stra tio n of his conclusions

about force presupposed “as an axiom — and by all thousand devils— no t as an hypothesis, th a t a force is no less indestructible th a n a substance [Substanz] . This general principle adm its of direct proofs as little for ‘force’ as for ‘substance’: b u t why th e principle is to be assum ed as an axiom , and how it derives from the sim plest concepts of our cognitive faculty, of th a t one can well give an acco u n t.”75 Sixteen m o n th s later he was still arguing th e sam e line: A side from th e ponderables, however, there are still otheT objects (im ponderables) which are likewise subject to th e above law [i.e., that no given m aterial su bstance ever b ecom es n oth in g and n on e com es into ex isten ce ou t o f n o th in g ]; th e proof for this can be derived from th e general laws of hum an th ou gh t, from th e principle o f suffi­ cien t reason [der S a tz vom logischen G runde]; in m y paper in th e May issue o f the Annalen I derived it w ith, as I b elieve, perfect precision from th e axiom atically as­ sum ed principle causa aequ at effectu m .76

It is im p o rtan t to see M ayer’s appeal to th e laws of th o u g h t as a strategy — not th a t he was insincere, b u t th a t his m ode of argum entation represented a lcind of creative negotiation betw een his evolving perception of the tru th and w hat he th o u g h t would convince his audience. For exam ple, in his earliest papers he did n o t invoke th e logical principle th a t nothing is created ou t of nothing despite the fact th a t at th e tim e (according to R um elin) he was quite attached to the slogan ex nihilo nil fit, and despite th e fact th a t in 1845 he did no t hesitate to place th at slogan at th e center of his exposition.77 By th en , however, he had pretty m uch resolved his lingering doubts ab o u t w hether or n o t force m ight n o t be creatable o u t of n o th in g in certain nonm echanical systems (including living organism s). He did not resolve those doubts by repeating to him self ex nihilo nil fit; it was rather th e case th a t th at ‘principle’ acquired its probative force only after Mayer had convinced him self for o ther reasons th a t there are no systems in which one is required to assum e th e creation of force ou t of nothing. O nce convinced, h e pro­ ceeded argum entatively as i f his factual conclusion followed unproblem atically from th e stated ‘principle.’ In those early papers he could fall back on th e dictum causa aequat effectum because he lim ited him self to systems where force is no t created and because he never en tertain ed th e possibility th a t forces (or m aterial substances) m ight simply pass ou t of existence. Even here, however, his under­ standing of w hat should be regarded as causes itself underw ent significant evolu­ tion, and w hether or no t an effect is equal to its cause depends, in ways M ayer only gradually m ade clear to him self, on w hat one calls a cause. T h e general point is th a t it would be a m isleading oversim plification to see M ayer’s conclusions as having followed straightforwardly from the principles to which h e professed at­ tach m en t: logically they may, b u t in reality these principles acquired th eir high status only after M ayer saw how he could exploit them to force acceptance of conclusions otherw ise arrived at. In discussing M ayer’s religiosity, I have already called a tte n tio n to his belief in th e necessary correspondence betw een th e conclusions of reason and empirically discovered tru th s of the physical world, as well as to th e reservations he occasion­ ally expressed with respect to reason’s ability to fathom reality. Sim ilar uncertain-

ties m arked his a ttitu d e tow ard th e grounds for accepting his theory. H aving in his earliest w ritings given u n am b ig u o u s precedence to th e logical u n im p u g n ab ility of his conclusions, by 1845 h e was insisting th a t th e ir validity rested "on th e laws of th o u g h t and on experience,” even if he still th o u g h t th e uncreatability of m a tte r was m ore convincing as an a priori tru th th a n as an experim ental d e te rm in a tio n .78 Six years later h e even fleetingly considered th e possibility th a t experience m ight disprove an axiom of th o u g h t: In the paper m en tion ed [of 1842], the pertinent natural law was traced back to a few fundam ental conceptions o f the human m ind. T he principle that a quantity that does not arise out of nothing can also n ot be destroyed is so sim ple and clear that against its correctness there is probably as little of any foundation to object as against an axiom of geometry, and we may assum e it to be true as long as the opposite has not b een proven, as for exam ple by m eans of an indubitably established fact.79

In th is M ayer m ay have b een a d a p tin g h im self to a scientific c o m m u n ity th a t was m ore co m fo rtab le w ith em pirical th a n w ith rational grounds for accep tin g scien­ tific tru th s. 2.4 Q u a n tita tive T h in kin g a nd the M easure o f the Equivalence o f H eat and M otion “Truly I say to you, a single n u m b e r has m ore genuine and p e rm a n e n t value th a n an expensive library full of h y p o th eses.”80 T h ese o ft-q u o ted words of M ayer to G riesinger are ju st th e kind of rhetorical flourish historians are used to d isc o u n t­ ing, often w ith good reason. Yet in fact from a very early period M ayer atta c h e d great significance n o t only to w hat he te rm e d th e q u a n tita tiv e d e term in a tio n of force, b u t also to th e calculation of th e n um erical equivalence of h e a t a n d m o ­ tio n — th e “re su m e ,” as h e te rm e d it, of his ideas. A m ong o th er things, his a ttitu d e tow ard q u an tific a tio n an d em pirical confirm ation reveals his a tta c h m e n t to a par­ ticu lar ideal of science: h e saw h im self vis-a-vis his chosen public as m aking a c o n trib u tio n to physical science, n o t to speculative n a tu ra l philosophy, despite his personal conviction th a t his theory h ad p ro fo u n d m etaphysical im plications. W h e n M ayer first p u b lish ed a value for th e n um erical equivalence of h e a t and m o tio n in 1842 he failed to in d ic a te his m e th o d o f derivation. H e m ad e good th a t om ission in 1845 by rep ro d u cin g his original calculation: L et th e h e a t absorbed by a volum e of gas in raising its te m p e ra tu re one degree at c o n stan t volum e be x, th e h e a t abso rb ed in raising its te m p e ra tu re by th a t a m o u n t a t c o n sta n t pressure be y. T h e la tte r case is eq u iv alen t to th e raising of a w eight P th ro u g h a h e ig h t h, thus y = P x k A cubic c e n tim e n te r of air a t 0° an d an atm o sp h eric pressure equal to 76 cen tim eters of m ercury weighs 0.0013 gram . U nder co n sta n t pressure a onedegree rise in te m p e ra tu re increases its volum e by 1/274, w hich u n d er standard co nd itio n s corresponds to th e raising o f a co lu m n of m ercury o f h eig h t 76 c e n ti­ m ete rs an d cross sectio n of o n e square c e n tim e te r (and th u s of w eight 1033 gram s) by 1/274 cen tim eters. Since th e specific h e at of air a t c o n sta n t pressure is 0.267— M ayer did n o t worry a b o u t u n its— th e h e a t absorbed by a cubic centi-

m eter of air is 0.0013 X 0.267 = 0.000347. To com plete the derivation h e needed one more piece of inform ation: According to D u lo n g . . . th e quan tity of h e a t th a t air absorbs at co n stan t volum e is to th a t at constant pressm e as 1:1.421; calculated from this, th e q u an tity of h e a t th a t raises [the tem p eratu re of] our cubic cen tim eter of air at co n stan t volume by 1° is = 0.000347/1.421 = 0.000244 degree. It follows th a t th e difference y = 0.000347 - 0.000244 = 0.000103 degree of heat, by m eans of whose expenditure the w eight P = 1033 gram s was raised by h — 1/274 centim eter. T hrough reduction of these num bers one th e n finds th at ., , 367 m eters I of heat = I gram at a height of I , . r 5 a I 1130 Parisian feet.81

In ch apter 6 I will consider m ore closely how M ayer was led to make th e only calculation th e n possible of th a t nu m b er from published data, th a t is, from those relative to th e therm al expansion and specific heats of gases. In 1851, after his priority dispute with Joule had th ru st into new prom inence th e significance of the num erical determ in ation of the m echanical equivalent of heat, he was even more insistent th at num bers and num erical relationships— Zahlenverhdltnisse and Grossenbestimmungen— were th e very foundation of the exact sciences.82 2.5 The Measure o f Force 2.5.1 Q U A N T IT Y O F M O T IO N VS. VIS VIVA

M ayer’s earliest attem p ts to com e to term s w ith force as a physical concept were frustrated by th e inconsistencies h e encountered in contem porary textbooks re­ lating to th e definition and m easure of force. F inding “qu an tity of m o tio n ” m eas­ ured by th e p ro d u ct of mass and velocity, M ayer involved him self in a labyrinth of confusions trying to reconcile his inchoate notio n of the conservation of force w ith th e principle th a t equal and opposite quantities of m otion cancel each other out. N or were his problem s m ade easier by the fact th a t he ten d ed to ignore the distinction betw een mass and weight. Reading th e published paper of 1842, one would be tem p ted to conclude th a t by then he had at least taken vis viva— i.e., την2— as th e m easure of force, b u t in fact as late as 1844 Baur was writing to him in exasperation “th a t you can’t be convinced to ad o p t from m echanics q u ite sim ­ ply th e statem en t th a t the m echanical work is equal to the vis viva.”88 In the m anuscript M ayer h ad sent him for com m ents h e not only still m easured force by the product of m ass and velocity, b u t atte m p te d to extricate him self from some of th e ensuing paradoxes by proving th a t 2 = O.84 In th e published version of th at work, and indeed still in 1851, M ayer did no t m ake those m istakes, b u t he per­ sisted in ignoring (for the m ost part) the factor of one-half by which th e vis viva m ust be m ultiplied in order to have a coherent physics of force.85 D espite M ayer’s abiding confusion as to th e m easure of force, he did ultim ately appreciate “th a t it leads to a com plete absurdity (or to a p erpetuum m obile) if one assum es th a t th e quantity of m otion is expressed by me.”86 It appears, in fact, th at M ayer’s rejection of rav as the m easure of force was prom pted by his confron-

ta tio n (presum ably in one of th e texts he h ad been reading, or in th e course of B aur’s tu to rin g ) w ith th e u n a ccep tab le co n seq u en ce of m echanical perp etu al m o ­ tion if one accep ted th a t defin itio n . For a sh o rt while, a t least, h e was inclined to a tta c h considerable d em o n strativ e im p o rta n c e to th e im possibility of a p erpetual m o tio n m ach in e. As h e w rote to G riesinger in 1842: But you will now say, w ith justice: “Prove the truths of your assertions.” I cite in this regard: I. T he necessary con seq u en ce of sim ple, undeniable principles. 2. O ne proof which dem onstrates (for m e subjectively) the absolute truth o f my propositions is a negative one: it is, namely, a proposition generally assum ed in science that the con­ struction of a perpetuum m obile is a theoretical im possibility . . . , but my assertions can all be regarded as pure consequences of this principle of im possibility; deny m e one proposition, and I will im m ediately build a perpetuum m obile. 3. A third proof can be exhibited to science from the lessons of experim ental physics.87

W e glim pse M ayer h ere in th e process, w hich ex tended over a period of roughly te n years, of searching for th e m o st effective way of establishing less th e tru th (w hich h e never d o u b ted ) th a n th e scope an d acceptability of his conclusions. 2 >2 TH E PARALLELOGRAM OF FORCES A N D CENTRAL-FORCE M O T IO N S

Perhaps th e m o st baffling aspect of M ayer’s 1841 p ap er was his application of th e d o ctrin e of th e parallelogram of forces to cen tral-force m o tions, w hereby h e b e ­ lieved he could explain th e origin of light in th e sun. As he p u t it to Baur: A ccording to the foregoing, the parallelogram o f forces requires in dynamics (not in statics) an essential correction: the theory of the neutralized com p on en t of m otion [die Lehre von der Neutralisierten], w hich has been overlooked in the com position of m otion and erroneously presupposed in the decom position of the diagonal into the (taken together larger) enclosing sides. T his has im portant consequences for the laws of central m otion; briefly put, the central body behaves falling toward the periphery like the peripheral bodies behave as falling toward th e center; this is the cause of the production of light.88

Since M ay er’s ideas h ere are q u ite wrong, it is im possible to m ake complete sense of th em ; th a t is, th e parallelogram of forces c a n n o t b e applied to planetary m o ­ tions so as to yield th e p ro d u ctio n of lig h t in th e sun. (M ayer knew n o th in g of th e conservation of angular m o m e n tu m .) N evertheless, one can m ake at least rough sense of w h at h e th o u g h t he was doing w ith th e (relative!) clarification provided by tw o key passages from la te r le tte rs to Baur. T h e key is to recognize th a t M ayer was tre a tin g b o th (N ew tonian) force an d “m o tio n ” (roughly m o m e n tu m , th o u g h he did n o t have a sure grasp of th e physical m ag n itu d es involved) as forces in th e sense of his new and still thoro u g h ly confu sed theory. T h e crucial d istin ctio n for M ayer was b etw een th e case in w hich a single force is decom posed in to two smaller, m u tu ally p erp en d icu lar forces (e.g., a body con strain ed to m ove in a cir­ cle by m eans o f a string— M ayer’s “dead radius v ector”— fastened to a central p o in t), an d th e case in w hich tw o forces supposedly co m b in e to yield a resu ltan t larger th a n th a t given by th e conventionally u n d e rsto o d parallelogram of forces

(e.g., o n e b o d y m o v in g u n d e r g rav itatio n al a ttra c tio n a ro u n d a n o th e r). T h e first case is easier to render, since M ayer was m ore explicit a b o u t it. As h e w ro te to Baur tw o m o n th s a fte r h e h a d s e n t his first literary e n d eav o r to Poggendorff: It results from my theory of th e parallelogram of forces th a t a body th a t is attach ed to a center by m eans of an artificial radius vector and w hich receives an im pulse m ust move w ith decreasing speed— ignoring, of course, friction. The path th a t the body would take w ithout the radius vector is the tangent; this represents the diagonal in the parallelogram. T h e decom position of th e com m unicated m o tio n in to a centrifugal and a peripheral is effected by m eans of the radius vector; by m eans of th e fixed m iddlepoint th e form er [com ponent of m otion] is continuously an nihilated, or rather becom es heat. A ccording to the fundam ental law of th e invariable q u an tity of forces it is at once evident th a t, since a portion of th e formerly present stock of m o tio n is continuously annihilated, this stock itself m u st be decreasing. T h a t is, th e tw o sides th a t enclose th e diagonal are, taken together, equal to th e diagonal, th u s n o t as large as th e figure of a parallelogram indicates, as one has q u ite falsely assum ed up to now. Nor, therefore, can one in th e case of planetary m otions take away th e gravitational force [Schwerkraft] and replace it with cords; a cord is never a force!89

E leven m o n th s later, d e sp ite th e a p p a re n t c o n c e p tu a l clarificatio n h e h a d ach iev ed in his p u b lish e d p ap er o f 1842, M ayer was still trying to salvage his original, hopelessly co n fu sed ideas. T h e only d ifference is th a t now he in sisted o n e has to co n sid e r th e square of th e le n g th s of th e d iag o n al a n d of th e (now necessar­ ily p erp en d icu lar) sides of th e parallelo g ram of forces in order to b e able to apply th e la tte r to dynam ics: In this way of representing m otions by lines, th e q u an ta of m otion are proportional to th e squares of these lines. O ne m ust proceed from this proposition if one wishes to apply th e parallelogram of forces to m otions. .. . In general, th e parallelogram , applied to m otions, m ust always be a rectangle. C om pare all th e cases in w hich m otions are com posed or decom posed. A decom position of m otions takes place w hen a q u an tu m of m otion is com m unicated to a mass connected to a fixed po in t by m eans of a radius vector. As a result o f the com m unicated quantum o f m otion, in a u n it o f tim e the mass would cover a certain distance in the direction o f the tangent. T his m o tio n is decom ­ posed in to two others, one of w hich, having a centrifugal direction, is annihilated, while th e other continues on in th e direction of th e periphery. The com m unicated motion is the diagonal, the two other motions are the enclosing sides; each of these la tte r is, since th e parallelogram is rectangular, sm aller th an th e diagonal. In every m o m en t th e rem aining peripheral m otion again becom es th e diagonal m o tio n and again as such is decom posed, in every m o m e n t the square of the centrifugal m otion is su b tracted from the square of the diagonal. T h e root of the rem aining square thus becom es smaller and smaller every m om en t, i.e., th e m o tio n in the periphery takes place w ith decreasing speed; w hat becom es of th e m o tio n annihilated in th e cen ter we [already] know. In th e centrifugal m achine there is only one force: th e first im pulse. T h e fixed point, the mass, and th e radius vector are n o t forces. T herefore it can never be a qu estion here of th e com position, b u t only of th e decom position of a m o tio n .90

If one (finally) pays due atten tio n to a phrase from M ayer’s 1841 paper, quoted above, in which he applied his reasoning to planetary systems— “instead of there being subtracted from the m otion M C a m otion in the direction -P c, a like m o­ tion is com m unicated to it from the direction + P c ”— th en one can interpret M ayer’s ideas quite well in term s of the following two figures: P MC

P MC

F ig . 2.1

Figure 2.1 represents th e situation of a body P constrained to move in a circle around a fixed m iddlepoint c by m eans of a “dead” (or “artificial”) radius vector; in figure 2.2 th e body moves about the center constrained by the force of gravity. In bo th figures, M C represents th e body’s initial m otion, p and z the “peripheral” and “centrifugal” com ponents of th at m otion (regarded by M ayer as a force). In figure 2.1 the centrifugal com ponent z is understood to be continuously neutral­ ized by th e fixed m iddlepoint c, hence removing th at portion of the m otion from th e body so th at it gradually slows down. In figure 2.2 the centrifugal com ponent is understood to represent the gravitational force exerted on P; com bined w ith the body’s original m otion, it yields a resultant large enough to com pensate for the m otion otherwise neutralized (presumably after the m anner of the other exam ­ ple), with th e result th at the body’s revolutionary m otion rem ains unchanged while the neutralized portion of the m otion appears as light em anating from the central gravitational mass. O f course, these diagrams do no t quite work— in partic­ ular, the centrifugal com ponent of the m otion in figure 2.1 is no t applied to the actual body P— b u t I think they faithfully convey the sense of w hat Mayer had in m ind. 2.6 M ayer’s Restriction o f His Ideas to Inanimate Nature and His Allowance for the Creation o f Force O ut o f Nothing Several considerations led Mayer to announce, in the title of his 1842 paper, th at he was dealing solely w ith the forces of “inanim ate” nature. For one, he had been of th e opinion from th e very beginning of his reflections th at he would have to secure his theory of force first in th e m ore fundam ental science of physics before seeking to apply it to physiology.91 M ore im portantly, the restriction to inanim ate nature reflected a m ajor continuing uncertainty in M ayer’s thinking, an uncer-

tainty revealed in his understanding of central-force m otions. His trea tm e n t of th em is thus im p o rtan t no t only as an illustration of the m orass of confusions he had to work him self through, b u t also because it was precisely those considera­ tions which, it seems, induced him to entertain the possibility th a t force m ight be created out of n o th ing in certain physical systems. In a continuation th e following day of th e second of the letters to Baur quoted from just above, M ayer w ent on to explain th e difference, as he perceived it, betw een w hat one m ight term m echan­ ical and organic systems: “T h e m otion of th e heavenly bodies is no counterproof; it has to do here n o t with a dead radius vector b u t w ith the fallforce. T he planetary system , stellar systems in general, are com positions ordered with divine wisdom (organisms) in which ‘force’ is really produced, and they thereby differ essentially and vastly [him m elw eit] from our m achines. However, my presentation will ex­ ten d only up to organisms (exclusively).”92 C h ap ter 6 will include an extended exposition of a late, unpublished work of M ayer's th at reveals the profound extent to which he had had to resolve extensive d o ubts as to th e possibility th a t force m ight be created in certain physical systems before he could confidently extend his theory to include organic systems. Here I would only call a tte n tio n to th e fact th at one of the m ost im portant general as­ pects of th e evolution of M ayer’s theory of force was his having to decide w hat entities his theory was a theory o f and (concom itantly) what its scope was. Accord­ ing to R um elin’s late recollections, at a very early period Mayer wrestled w ith the problem of th e ex tent to which his ‘principles’— for example, th a t noth in g can be created o u t of nothing— apply to organic and psychical phenom ena.93 O ne can freely reconstruct th e kinds of questions at issue: W h a t ab o u t generation, the m ind, and th e soul? W liat kinds of entities are involved? Is the soul a force? If it is, and if a new soul appears at th e generation of each new born individual, where does it com e from? U ncertainty ab o u t these sorts of questions, com bined w ith M ayer’s belief th a t the solar system, as a divinely ordered organism , is itself capa­ ble of generating force ou t of nothing, led him to restrict his earliest claims to inanim ate nature. To be sure, M ayer did no t d o u b t th a t b o th souls and forces are im perishable once they are in existence; the question was w hether forces are like chem ical substances and hence to be regarded as (in the norm al course of nature) uncreatable, or like souls and capable of com ing into existence u n d er certain com ­ m on circum stances. Finessing the question of th e creatability of force, M ayer in his early work spoke only of its indestructibility. In those few instances where he seems to imply otherw ise, by speaking of its q uantitative invariability, one can supply from the context his restriction of his ideas to inanim ate nature. M ayer was for th e m ost part an individual of few thoughts long and tenaciously held, and despite th e transform ation his ideas underw ent, issues th at preoccupied him at an early period ten d ed to reappear surprisingly unchanged years later. In a talk in 1869, “O n Necessary C onsequences and Inconsistencies [Inconsequenzen] of th e M echanics of H eat,” Mayer reflected on som e of th e differences betw een th e inanim ate and anim ate realm s of nature in a way strongly rem iniscent of his reported conversations w ith R um elin tw enty-eight years earlier:

L e t us now m ove from th e d o m a in of in a n im a te n a tu re over in to th e living w orld. If necessity and th e law ’s ev er-sy n ch ro n ized clock ru le th e re , so d o we n o w e n te r a realm of p u rp o sefu ln ess a n d beauty, a realm of progress a n d freed o m . N u m b e r m arks th e b oundary. In physics n u m b e r is ev ery th in g , in physiology it is little , in m etap h y sics it is n o th in g . S atu rn , th e all-d ev o u rin g , h as ceased to rule; tim e is p ro d u c tiv e in o u r p re se n t d o m a in . G o d spoke: L e t it b e , a n d it was! T h e living w orld is n o t only p re ­ served, i t grows an d it b eco m e s m o re b ea u tifu l. L e t us take th e ste p from d ea d to living n a tu re w ith calm d elib e ra te n ess. W e m u s t g u ard ourselves ag ain st tw o m is­ takes. First, we m u s t n o t o n c e m o re im m e d ia te ly a b a n d o n th a t w hich has b e e n a c ­ q u ire d in th e physical d o m a in w h en we e n te r o th e r fields; ra th e r we m u s t re ta in it as m u c h as possible, even in physiology an d philosophy. . . . S eco n d , we m u s t n o t, h o w ­ ever, be all to o stric t [consequent] in th e re te n tio n of physical p ro p o sitio n s, for w hile w e th e re have h ad to d eal w ith laws, we now have only rules. T h e p rin cip le o f th e c o n serv atio n of m a tte r a n d of force is d o u b tle ss also valid in physiology. T h e living o rg an ism can n e ith e r cre ate n o r d estroy m a tte r or force, n o r can it tra n sfo rm th e given e le m e n ts in to on e a n o th e r; on th e o th e r h a n d , tern a ry a n d q u a te rn a ry c o m b in a tio n s, w hich as a rule c a n n o t b e p ro d u c e d artificially, are c re a te d in th e m o s t rem arkable fashion by th e p la n t w orld. F u rth e rm o re , p ro c rea tio n a n d g e n e ra tio n tru ly d o take place in living n a tu re — an activity for w h ich o n e in vain seeks an an alo g in th e purely physical d o m ain . T h e physically c o rrect p rin cip le “E x n ih ilo nil fit” can th erefo re n o lo n g er b e m a in ta in e d an d su sta in e d w ith full stric tn e ss even in physiology, m u c h less still in th e psychic \geistig\ d o m ain . I am h e re re m in d e d o f a rem ark ab le passage in L u c ia n ’s D em onax. A sked w h e th e r h e h e ld th e soul to b e im m o rta l, th e p h ilo so p h e r answ ered: “Yes, im m o rta l like ev ery th in g e lse .” T h e c o n serv atio n prin cip le, o r th e seco n d p rin cip le, “N il fit ad n ih ilu m ,” is tru e to still g rea te r deg ree in G o d ’s living c re a tio n , insofar as it is no lo n g er lim ite d , as in th e in a n im a te w orld [todte N a tu r], by th e sterile prin cip le “E x m h ilo nil fit.”94

2.7 Force as an Antidote to Materialism From th e earliest period for which we have contem poraneously recorded evi­ dence— the sum m er of 1841— it is clear that M ayer’s ideas on force m eant m uch more to him than simply a revolution in the conceptual foundations of physical science. Briefly sketching th e progress of his thinking from physiology and pathol­ ogy to chem istry and physics, Mayer wrote in his first letter to Baur that he had formed for him self a view of nature (Naturanschauung) “which com pletely clari­ fied for m e a vast and really infinite series of heretofore inexplicable phenom ena, and which, aside from the field of science and specific m edical questions, solves for m e in addition the m ost im portant questions o f m etaphysics.”95 Ten years later he allowed h im self the shortest of public allusions to this other realm: “Force and m atter are indestructible objects. This law . . . is a natural foundation for physics, chemistry, physiology, and— philosophy.”96 Unfortunately, in none of his earliest writings, either public or private, did Mayer specify just what those m etaphysical considerations were, but there seem s little doubt that they had to do with things like the m ind, the soul, and the latter’s

imperishability. It is my contention th at, from close to the very beginning, an essential part of th e meaning of M ayer’s developing theory of force concerned its antim aterialistic im plications.97 T h a t is, M ayer’s concept of force as an im perish­ able and active nonm aterial thing was part of a larger ontological picture th at included similarly im perishable b u t iirert m a tte r on the one side and an im perish­ able and self-active soul on th e other. As has been shown, Mayer believed for a nu m b er of years th a t force, unlike m atter b u t thus in some ways like the soul, m ight n o t be wholly uncreatable. M ulberger has, I think, correctly analyzed the connection betw een M ayer’s understanding of force and his opposition to m ateri­ alism: As is well known, for vulgar materialism force is a mere property, a mere product of matter, of material substance. The principle of all being resides exclusively in matter. Now the law of the conservation of force, as formulated by Mayer, has proven deci­ sively that the same properties that allow m a tter to appear in the eyes of its true believers as the highest principle— namely indestructibility and transformability— belong no less also to force. “Forces,” says Mayer, “are indestructible, transformable, imponderable objects.” As little as an atom of matter in the universe can becom e nothing, just as little can a quantum of m otion, heat, electricity, magnetism, etc., becom e nothing. Thus force, far from being a mere property, a mere product of mat­ ter, is raised by Mayer’s discovery to the status of matter. Vulgar materialism is thus decisively shattered, it no longer makes any sense.98

A lthough these observations date from late in M ayer’s life— M ulberger, a doctor at th e sanatorium in K ennenburg (near Esslingen), got to know him only in 1871— I suspect sim ilar considerations were operative m uch earlier. C ertainly Mayer was not alone in perceiving the issue in these term s. As physiologist Alfred W ilhelm Volkmann wrote three years before M ayer’s voyage: Materialists conflate force and matter in that for them forces are nothing but proper­ ties of matter itself. The properties of matter depend on [its] form and composition, and the vital activities of organisms on [their] organic form and com position. Spiritu­ alists proceed in the opposite fashion: either they allow matter itself to be produced out of force, or they at least regard force as in any case independent of matter, and assume an actual existence even without the filling of space. According to them the vital force is earlier than the organism and is related to it as cause is to effect. The spiritualist therefore also distinguishes the soul from the body, and regards it indeed as the cause of all vital phenom ena, and as the architect of its body, as Stahl taught.99

Only late in life did M ayer publicly assert th a t his doctrines had m etaphysical im plications. In the preface to th e first edition of his collected papers in 1867 he no ted briefly, w ith reference to the scope of his 1851 work, Remarks on the M e­ chanical Equivalent o f Heat: “T h e m etaphysical side of th e new subject has at the sam e tim e thereby been touched upon, one w hich is diam etrically opposed to the principles and consequences of the m aterialistic viewpoint. W e owe an extensive treatm en t of this them e to the excellent French physicist A. H im in his ‘E le­ m entary sketch of th e m echanical theory of heat and of its philosophical conse-

quences,’ Bulletin de la Societe d ’histoire naturelle de Colmar, 1864.”100 Two years later, in an address before th e Naturforscherversammlung in Innsbruck, he spelled out more explicitly what it was about H irn he liked: The French physicist Adolph Hirn . . . posits— in my view in a fashion as elegant as it is true— three categories of existences [Exisfenzen]: (I) matter, (2) force, and (3) the soul or spiritual principle. If one has once arrived at the insight that there are not only material objects, but that there are also forces, forces in the narrower sense of modern science, just as indestructible as the elem ents of the chemist, then for the assumption and recognition of spiritual existences one has only to take one further logically necessary step. In the inanimate world one speaks of atoms, in the living world we find individuals. But, as we know, the living body consists not only of m ate­ rial parts, it consists essentially also of force. But neither matter nor force is capable of thinking, feeling, and willing. Human beings think,101

Hirn intended his work to constitute “the refutation of m aterialism and p an th e­ ism, a justification of th e m ost absolute spiritualism .”102 In an unpublished autobiographical fragm ent, Mayer cited his address of 1869 and three others as having throw n down the antim aterialistic gauntlet to an u n ­ appreciative scientific audience. His words confirm M iilberger's understanding of the connection betw een his conception of force and his rejection of m aterial­ ism: “It goes w ithout saying th a t a m an who was the first to enunciate and elabo­ rate the principle th a t no t only m atter b u t also vis viva in its different form s— such as m otion, heat, light, and electricity— possess the property of substantia] quantitative indestructibility, cannot em brace a m aterialism th at would restrict this property to ponderable objects alone, and to th at extent these addresses may not have tu rn ed out according to the taste of exclusive m aterialists.”105 In a letter of 1871 to th e pastor Rudolf Schm id accom panying a copy of his just-pub­ lished collection of addresses— which included his Innsbruck address of 1869— Mayer reaffirmed his com m itm ent to the “antim aterialist standpoint” it defended and which he would "never disavow,” whereby he invoked Jesus’ words from M at­ thew 10:32: “W hoever then will acknowledge m e before m en, I will acknowledge him before my father in heaven.”104 M ayer’s rejection of the m aterialistic turn of science th at, ironically, his and others’ work on th e conservation of energy had only strengthened, reinvigorated the theistic strain always present in his belief system. A lthough in his published works M ayer rem ained reluctant to elaborate on w hat he saw as th e m etaphysical and theological im plications of his scientific work— and th e distinction m ust have been a real one for him — in a late and orig­ inally long unpublished m anuscript he argued at great length th at em pirical sci­ ence justifies belief in the existence and im m ortality of the soul.105 A lthough one cannot assum e th at M ayer’s concerns of the late 1860s were identical to those of the early 1840s, one can reasonably conclude th at a significant aspect of his early conception of force involved its ontological im plications for the existence of m ind and soul. T h at was one of the reasons Mayer was so excited by the new worldview he saw opening up in front of him .

2.8 The Search for Valid Analogies To a great e x te n t th e en tire course of M ayer’s theorizing can be characterized as a search for valid analogies: In w hat ways is w hat like w hat? A bsolutely central to his th in k in g was th e rich analogy b etw een force a n d m atter. T h ese tw o e n tities, w hich to g e th e r m ake u p th e physical world, share th e prim e characteristics of q u an tita tiv e invariabililty (or a t least in d estru ctib ility) and qualitative variability; they differ w ith respect to th e ir (im )p o n derability/(im )m ateriality. T h e n eu trali­ zation of opposing m o tio n s is like th e n e u tra liz a tio n of different chem ical species, b o th processes exhib itin g th e stip u lated q u a n tita tiv e constancy and qualitative transform ability. Physics and chem istry were accordingly seen as th e parallel sci­ ences of force an d m atter. In a sim ilar fashion, M ayer pondered th e n atu re of m atter, force, spirit, an d soul: H ow are they similar, how different? M ayer likened th e fall of a body tow ard th e e a rth to th e com pression of a gas: b o th processes are accom panied by th e p ro d u ctio n of h ea t, a n d b o th can b e re­ garded as representing a decrease in volum e. H e was strongly influenced by the im plied analogy b etw een living organism s and divinely ordered system s like the solar system : if, as it seem ed, force could be created o u t of n o th in g in th e latter, m aybe th e form er were also capable of som e sort of creation ex nihilo. H e m u st have p ondered, too, th e ex te n t to w hich anim al organism s are like m achines. A nd he was m u c h taken by graphic m etap h o rs, such as A u te n rie th ’s analogy betw een scientific system s of th o u g h t as im p erfect rep resen tations of reality, and a ta n g e n t capable of to u c h in g a circle at only one p o in t; or th e analogy betw een such a system and a m ap projection. R iim elin reco u n ted still an o th e r favorite: “Just as little as a positive m ag n itu d e could b eco m e n o u g h t [zu N u ll werden] in th e course of a calculation— th is was an im age an d exam ple h e often liked to repeat— so little could a force disappear in th e effect an d vanish in to n o th in g .”105 O th e r exam ples of th e im p o rtan ce of analogies to M ay er’s th o u g h t processes will present th e m ­ selves in la te r chapters. T h e difficult issue he constantly had to co n fro n t was: W h ic h are th e valid analogies? M ayer seem s to have believed th a t his theory of force was n o t so m u c h illu strated by his favored analogies as proven by them .

P

A

R

T

I I

•

Establishing the Relevant Context

•

C H A P T E R

T H R E E ·

Physiology an d M edicine

I t i s i m p o s s i b l e to u n d erstan d M ayer’s thinking on physiological and other issues w ithout knowing w hat general ideas he was exposed to from the com m on litera­ ture of th e period. G uided by the topics identified in th e last chapter as character­ istic and significant in M ayer’s work, in Part Two (chapters 3-5) I will seek to establish a baseline of com m on contem porary views in selected areas of physiol­ ogy and m edicine, physics and chemistry, and religion and spiritualism . I will also consider discussions of th e n ature and scope of science— especially th e self-con­ scious transform ation of G erm an physiology and m edicine beginning in th e late 1830s— and th e possible significance of railroads and the m echanization of indus­ try to a transform ed conception of th e n ature of organic systems. It turns ou t not to m atter a great deal th a t one cannot always identify M ayer’s precise sources, since th e m ajor issues were widely discussed in the m ost prom inent (and typical) writings of th e period, usually w ith th e sam e conclusions. I will, however, pay particular a tte n tio n to three works of special im portance: Johannes M uller’s Handbook o f H um an Physiology (1833-44), Johann H einrich Ferdinand A utenrieth ’s Views on the World o f N ature and the L ife o f the Soul (1836), and Jacob Friedrich Fries’s Textbook o f Physics (1826). A lthough M ayer’s sources have been obscure to historians, I hope to show th a t he drew overwhelmingly— if, to be sure, idiosyncratically and som etim es obscurely— from the com m on and highly visible writings and issues of his day. Significantly, th e m etaphysical questions th a t con­ cerned him , such as th e nature of the soul and its relationship to the other agen­ cies of nature, were th en regularly treated either in th e physiological literature itself or in o ther works w ritten by physicians. H ence Mayer as a physician was confronted by a m uch broader range of issues th a n would have been th e case even ten years later, after th e above-m entioned transform ation and disciplinary con­ traction of physiology and m edicine.

I B l o o d , R e s p ir a t io n ,

and

A

n im a l

H eat

O f p aten t indispensability to life, and subject to m anifold readily observable vari­ ations, th e blood has, since ancient tim es, b een of central concern to b o th healers and natural philosophers. In addition to the prom inence regularly accorded the blood in texts, th e 1830s also saw th e publication of a burgeoning specialized literature on th e subject.1 It m u st be rem em bered, too, th a t bloodletting was then considered to be, in th e words of one author, “th e m ost im p o rtan t remedy in m edicine, w ith o u t w hich it is difficult, indeed alm ost im possible, to b e a physi­ cian.”2 H ence a stu d en t of m edicine such as Mayer w ould have had to acquire a

close fam iliarity w ith th e properties and physiological functions (as th en sup­ posed) of th e blood. In M ayer’s case, furtherm ore, two of his professors seem to have been especially interested in th e topic: Rapp, his thesis adviser, was reported to have assigned prim e im portance to th e blood, and A utenrieth had w ritten his dissertation on venous blood and directed (if n o t w ritten) another on fetal blood and heat.3 A u ten rieth ’s H andbook o f Empirical H um an Physiology (1801-2), which M ayer owned, dealt at len g th w ith the differences betw een arterial and venous blood and the transform ation of th e form er in to th e latter.4 In his view it is the disappear­ ance of vital air (Lebensluft) from th e bright-red arterial blood— th a t is, its w ith­ drawal by the organs th e blood flowed th ro u g h — which, u n d er norm al circum ­ stances, transform s it into th e dark-red venous blood. A u tenrieth observed th at the venous blood of those suffering from p u trid fevers (i.e., typhus) is often bright red, as is th a t of healthy people during th e sum m er. Taking, however, th e blood’s coagulability as an im plicit m easure of its oxygen c o n te n t— th e m ore oxygen, the readier th e coagulation— h e n o te d th a t in b o th those cases th e brighter-thannorm al venous blood nevertheless coagulates less readily, and hence contains less oxygen, th an th e arterial blood it superficially resembles. T hus A uten rieth ’s wellknow n5 observation of th e brig h ter red of venous blood in a warm er environm ent was not directly connected w ith any putative increase in its oxygen c o n ten t com ­ pared w ith norm al venous blood; his point was rather th a t even when th a t co n ten t varies in som ething like th e norm al manner, as shown by th e process of coagula­ tion, venous blood may still n o t take on its norm al dark hue. Nor did he explicitly connect th e variations in color change w ith th e production of anim al heat. A utenrieth attrib u ted th e dark color of venous blood to th e production of w hat he called semi-acidified carbon in it, and th u s th e darker color of venous blood in w inter to (first) th e greater am o u n t of vital (or dephlogisticated) air absorbed into the blood due to its higher co n centration in colder air, and (then) to its enhanced phlogistication as th e blood passes through th e organs of the body.6 In his wide-ranging discussion of anim al heat, A utenrieth assigned its origin to the absorption and subsequent decom position of gaseous oxygen by th e body— to processes whereby h eat is released as oxygen leaves its gaseous state and to the lesser h e a t capacity of th e substances th u s form ed.7 A lthough his sum m ary did not m en tio n th e color of th e blood, he clearly saw the blood’s increased oxygena­ tion in w inter and its dim inished oxygenation in sum m er— due primarily to the greater or lesser co n centration of oxygen in a volum e of colder or warm er air— as the primary m eans by which an anim al m aintains a co n stan t body tem perature in a changing environm ent.8 In a later work A utenrieth m ade only passing m ention of anim al heat, b u t clearly assigned its production to a com bustion process de­ p en d en t u p o n respiration.9 Treatises devoted to th e blood typically discussed th e effect observed on its color of such factors as am b ien t tem p eratu re, disease, state of th e nervous system, and life-style: venous blood is lighter in th e tropics, darker in polar regions and after a cold b ath ; high fevers and th e severing of th e nerves to a part of the body ten d to be accom panied by lighter venous blood; and th e redness of the blood is

enhanced by bodily m ovem ents and a m oderate life-style, while a sedentary way of life makes it darker.10 English physician C harles T urner T hackrah’s report of th e brighter venous blood of a m an subjected to venesection just after a warm b a th was a m inor locus classicus, though only its context reveals th e point Thackrah wished to make: T h e tem perature of th e b od y is subject to such slight variation, that we can expect from this cause little change in th e character o f blood. In cold regions, however, the b lood is stated to be darker than in tem perate ones; and w ithin th e tropics, I believe, to be som ew hat brighter. In this country, a horse in a straw-fold will have dark blood; and rem oved to a stable, he presents it considerably lighter. Such effects m ay he attributed less to th e few degrees of variation in th e tem perature of the body, than to the reduced or excited state of the circulation. C old is well know n to reduce th e action o f th e lungs and heart, h ea t to increase them : and to this change in th e rapidity with w hich th e blood is transm itted through th e system , I should ascribe its variations of colour. O n b leed in g a m an im m ed iately after subm ersion in a warm b ath , I found the blood of the basilic vein scarlet.11

T h e p h en om enon, as conceived by Thackrah, has nothing to do w ith any change in th e rate of oxidation, nor did h e discuss it in term s of the econom y of anim al heat: “T h e ph en o m enon is no t difficult of solution, if we believe the dark colour of venous blood to depend on th e addition of carbonaceous m atter. Blood hurried by disease through th e circulation, has less tim e to take up this m atter, and hence remains nearly of the colour it h ad w hen ejected from the left ventricle of the h ea rt.”12 But th e whole issue of th e cause of th e difference in color of arterial and venous blood was q u ite unsettled: th e editor of T hackrah’s posthum ously p u b ­ lished book cited two authorities as arguing “th a t the florid colour of the arterial blood is not due to oxygen, b u t . . . to th e saline m atter of th e serum .”13 In review­ ing th e evidence on this issue, H erm ann Nasse tentatively concluded th at the presence of b o th oxygen and salts is necessary to produce the bright red arterial h u e .14 O ne of th e very few to consider in the same context (albeit briefly) the dependence of th e blood’s color on tem perature, th e degree of its oxygenation, and th e production of anim al h eat was Ferdinand G ottlob G m elin, one of M ayer’s m ajor professors at Tubingen: A ccording to th e experiences of Lavoisier and Seguin, recently confirm ed by Dr. Prout, an anim al con su m es m ore oxygen gas in th e cold than in the heat; th e arterial b lood o f an anim al is brighter red in the cold, th e venous b lood darker black. T here thus occurs in th e cold n ot only a preponderance of oxygen, or the w eightless agency that acts w ith or by m eans of it in th e vital process, b u t the vital process is in general m ore en ergetic, m ore co m p lete, b ecau se the difference b etw een arterial and venous b lood is greater on b o th sides. For just that reason, and b ecau se th e principal source o f anim al h eat is th e transform ation o f arterial b lood in to venous blood, th e internal source o f h ea t is au gm en ted in winter.15

A u ten rie th ’s lectures on nosology, which Mayer atten d e d in 1834-35, presum ­ ably dealt w ith o th er instances of pathological change in th e color of th e blood.

T he u nauthorized published text of his lectures discussed one such exam ple in th e case of bilious fevers, which are caused by exposure to a h o t clim ate. (Batavia, th e capital of th e D u tch East Indies, was specifically m entioned.) A utenrieth noted th e disappearance of “the sharp difference betw een arterial and venous blood,” th o u g h w ithout specifying w hether th at was because th e venous blood becom es brighter or th e arterial blood darker. As for therapy, he advised th a t “bloodletting before the outbreak of putrid fever is of som e effect, to the extent th a t th e dim inished quantity of blood is m ore readily oxidized.” 16 A utenrieth h ad given a som ew hat am plified account of th e physiological pro­ cesses th o u g h t to underlie this condition in th e second volum e of his Handbook— th a t is, apart from his discussion of respiration. D uring the first three or four decades of th e n in etee n th century, physiologists regularly assigned to th e liver the function of rem oving excess carbon from the blood via th e secretion of bile.17 A utenrieth cited experim ents involving th e ligation of the portal vein as dem o n ­ strating th a t th e carbon excreted in the bile com es from th e venous blood. In accordance w ith th e then com m on view th a t warm er air contains less oxygen— resulting in a decreased excretion of carbon through th e lungs as carbon diox­ ide— he recorded th a t diseases involving an excess of bile predom inate in very hot regions, and th a t in Europe during h o t sum m ers the blood often exhibits a darker yellow, som etim es even greenish serum (and an unnaturally soft crassam entum ), o ften in association w ith bilious diseases.18 A lthough he did no t explicitly say so here, one could reasonably surm ise from this line of reasoning th a t venous blood m ight be darker in a h o tte r environm ent, no t lighter, as earlier considerations im plied. O n th e o ther hand, one m ight conclude th a t such blood should not necessarily show any color change vis-a-vis th e norm since the excretion of bile makes u p for th e decreased excretion of carbon as carbon dioxide. T h e whole topic was one of considerable confusion. A m uch fuller and clearer understanding of th e physiological and m edical issues relating to th e blood, its color, th e am bient tem perature, and th e production of bile can be derived from another contem porary work in M ayer’s library, Leipzig physician M oritz H asper’s O n the Nature and Treatment o f Tropical Diseases. In th e section on diseases of the liver th e au th o r reasoned as follows: From experim ents and observations perform ed by Crawford, Lavoisier, Seguin, Prout, C opland, Pierson in A m erica, etc., it follows in particular that th e quantity of carbonic acid form ed through respiration [Respiration] in a given tim e appears d im in ­ ished at a higher tem perature and w ith a declin e in th e vital forces. It results from th ese experim ents and observations that less carbon is disengaged from th e blood via respiration [das A th m en ] in a given tim e in hot clim ates than in a colder one, whereas th e quantity o f carbonacious material brought in to the circulation of th e b lood is equally great, and that this substance w ould soon be present in excess in th e blood o f persons living in hot clim ates unless another organ su b stitu ted [vikariirte] for the lungs. A principal com p o n en t of bile is, however, carbon and hydrogen. Therefore w hen the secretion o f bile is increased, a greater quantity o f carbon is rem oved from the

blood, thereby preventing th e accum ulation of this substance in th e blood th a t would take place in case of dim inished excretion of it thro u g h the lungs. Since, then, as a result of th e increased tem p eratu re th e function of th e lungs with respect to the expulsion of carbon is dim inished, b u t th e sam e am o u n t of carbon is conveyed to th e blood through food and m ode of life, disease would thus have to result if natu re did n o t know how to find a way to resolve this im b alan ce.19

In R asper’s view, the purpose o f th e oxygenation o f blood in the lungs is to rid the body of the carbon— derived largely, it seem s, from food— that accum ulates in the blood. T he body com pensates for the reduced oxygenation in hot clim ates by increasing the secretion of carbon-rich bile. Hasper said n oth in g about the color of the blood in th ese circum stances, and sim ply ignored the otherwise widely discussed changes in the color o f the blood of a person subjected to ele­ vated tem peratures. His later discussion of th e cause of the reduced oxygenation in h ot clim ates did contain, however, a faint clue as to what one m ight expect to observe: It is a law for all of physical nature that heat expands all bodies and cold contracts them. T h e atm osphere is accordingly in a m ore or less rarefied state th e higher or lower th e prevailing tem p eratu re in a country. As a consequence, a certain q u an tity of in­ spired air contains less oxygen th e higher its degree of heat. O ne therefore breathes easier and m ore freely in a cold atm osphere and, insofar as m ore oxygen enters th e lungs or blood, th e oxidation process takes place th ere m ore vigorously, as direct experim ents perform ed in this regard by Seguin and Lavoisier have also shown. Now, since a portion of th e oxygen of th e atm osph eric air com bines during respira­ tio n w ith th e carbon of the blood, less carbon is thu s disengaged from th e blood in a given tim e in a h o tte r clim ate th a n in a colder one, and this principle predom inates in th e blood of m ost sick people . . . . T h e force of n atu re [N aturkraft], w hich so often acts in a n am azing m a n n er in cases of disease, a ttem p ts . . . to correct even this im balance of th e blood arising in h o t clim ates by stim ulating an increased secretion of bile, perhaps also by m eans of in­ creased evaporation through th e skin.20

Thus it appears that an individual arriving in the tropics should show darker than normal venous blood. (N ote that for Hasper only p a rt of the inspired oxygen com bines w ith the carbon of the blood to form carbon dioxide; nor did he ever talk about anim al heat or its relationship to am bient tem perature.) As for the treatm ent of liver disease, Hasper, too, recom m ended b lood lettin g and the appli­ cation of up to thirty leeches, notin g that in th e East Indies often as m uch as three to four pounds of blood is withdrawn.21 A lthough his treatm ent was m u ch briefer than H asper’s, Johannes M uller also remarked on the liver’s function in ridding the body of excess carbonaceous m at-

ter via the secretion of bile. C om paring the liver explicitly to the lungs, he noted th at A utenrieth, T iedem ann, and Gm elin had, in particular, called atten tio n to th e “reciprocal relationship betw een lungs and liver."22 He n oted th e increased incidence of diseases of the liver and intestines in hot, hum id clim ates, and in­ voked th e sam e reasoning as Hasper with respect to the physiological function of bile secretion and the reduced oxygen co n ten t of h o t air: “T iedem ann and G m eIin assert th at the increased secretion of bile in tropical clim ates com pensates for th e reduced purification of the blood in the lungs, which m any derive from the atten u atio n of th e air as a result of the h ea t.”23 M uller said nothing further about th e m edical aspects of this condition, and nothing explicit about changes in the color of the blood, though the im plication seems to be th at such blood should be darker th an normal. On the basis of the contem porary prim ary literature alone it would be im possi­ ble to say just w hat M ayer’s beliefs and expectations were as he began to let blood off the Batavian coast in June 1840, especially since it would be unwise to con­ clude from his later published references to A utenrieth’s and T hackrah’s state­ m ents ab out the dependency of th e blood’s color on am bient tem perature th a t he was aware of th em in 1840. O n the basis of M ayer’s surviving medical exams, however, we can be quite sure th at he had well learned from Hasper and Miiller w hat to expect. By a stroke of am azing luck for later historians, the fourth ques­ tion p u t to Mayer on 16 August 1838 was, “W h a t influence does continued dam p and warm w eather exert on a person’s state of health?” His answer closely followed his presum ed sources: H c a t ex p an d s th e air, it th e re b y b e c o m e s p o o re r p e r v o lu m e in oxygen (as well as n itro g e n ); a t th e sam e tim e th e te n sio n o f th e fluid is in creased . As a resu lt, th erefo re, of th e d im in ish e d oxygen c o n te n t, th e re sp iratio n process is less e n e rg e tic in th e h ea t, a n d th e air is m u ch less d e c o m p o se d d u rin g resp ira tio n , th e b lo o d b eco m e s rich er in carb o n , darker, a n d th e d ifferen ce b e tw e e n red a n d black b lo o d is less. In re tu rn th e liver m u s t e n te r in to vicarious activity; it secretes m o re bile, w hich is a very c a rb o n rich su b stan ce. As a resu lt of th e in creased te n s io n of th e fluids a c co m p a n y in g th e h e a t, th e im p e rc e p tib le gaseo u s ev ap o ratio n th ro u g h th e skin a n d th e lungs is in ­ creased, w hereby h e a t b e co m e s la te n t an d th e body th u s again b ec o m e s coo led . B ut w hen th e air is nearly sa tu ra te d w ith w ater vapor, th e n th e gaseo u s ev ap o ra tio n is very re stric te d , n a tu r e ’s rem ed y falls away, a n d th e re arises th e oppressive feeling of su ltry h e a t; th e in te stin e s a c t vicariously for th e ev ap o ra tio n th ro u g h th e skin a n d th e lungs. T h e re th u s arises in d a m p h e a t an influx of h u m o rs to th e liver a n d in te stin e s. As a result of th e d e fic ie n t o x id atio n o f th e blo o d , p eo p le b e co m e sluggish, pale; th e d ig es­ tio n is w eakened, th e in te stin e s d isp o sed to d iarrh ea. T h e liver is very d isp o sed to in flam m atio n s, w hich are so m e tim e s a c u te , so m e tim e s e x trem ely ch ro n ic; th e fo rm er o fte n befalls th e le ft lobe. S tru c tu ra l ch an g es in th e liver are th e c o m m o n resu lt, particularly su p p u ra tio n . T h e in te stin e s are d isp o sed to dysentery, w hich o fte n b e ­ co m es very v iru len t a n d generally e p id e m ic , a n d w hich, fro m th e sen sib ility o f th e skin d u e to th e h e a t, o fte n arises a t th e slig h te st chill. As a resu lt of th e d im in ish e d o x id a­ tio n of th e b lo o d , th e vital process is m u c h less e n erg etic, th e h u m o ra l m ass d isp o sed to sepsis, all diseases easily assu m e th is ch ara cte r.24

Thus Mayer clearly expected to find the venous blood he let In the tropics to be d a rker than normal, hence his surprise was all the greater when he in fact found it to be bright red. In a letter to Lang a year before the start of the voyage, Mayer m entioned inflammation of the liver as one of the dangers of his contem plated trip to Java: he was mentally preparing himself fo r the altered physiological condi­ tions he expected to encounter.25 Note, too, that the evidence cited shows that Mayer regarded respiration as a means of ridding the blood of excess carbon, without any explicit consideration of the issue of animal heat. T he chief physiological function assigned to the blood was inextricably con­ nected with respiration: the blood is the vehicle by which oxygen and nutrients are distributed throughout the body and by which waste products—some, like carbonic acid, perhaps produced in the blood itself— are conveyed to the appro­ priate organ for removal. Johannes Muller, for one, assigned clear physiological priority to respiration and the processes of material exchange associated with it. Repeatedly invoking an image of the body as a complex machine, Muller asserted that it was respiration that set the machine in m otion.26 He concluded from a discussion of nutrition, excretion, and general processes of material exchange th a t life in and of itself is connected with a contin u o u s decom position of already organized substances. Nor is this possible in any other way if it is tru e, as was previ­ ously proven, th a t th e organic force in an anim al only m anifests itself [sich aussert} as long as certain vital stim uli continuously bring ab o u t m aterial transform ations in th e living parts, of which th e vital p h en o m en a are only th e p h en o m en a, as fire is th e p h en o m en o n of th e m aterial transform ation accom panying com bustion. T h e im pul­ sion [Antrieb] for these m aterial transform ations occurs th ro u g h respiration; the blood th a t is continuously changed through respiration in turn brings ab o u t co n tin u ­ ous m aterial transform ations in th e organs.27

Respiration, in turn, stood in some close, if not entirely unproblem atic, rela­ tionship with the generation of animal heat. Since its proposal in the 1780s, the dom inant theory of animal heat was Lavoisier’s, which attributed the heat gener­ ated by an animal to the combination of the inspired oxygen with nutrients in the body.28 The prime chemical measure of this low-intensity combustion process was the exhaled carbon dioxide. Considerable uncertainty attended the question of whether the supposed combustion takes place in the lungs, blood, or tissues, and attem pts to dem onstrate experimentally the presence of oxygen and carbon diox­ ide in the blood gave conflicting and inconclusive results until the issue was largely settled by Gustav Magnus’s work of 18 37.29 From the standpoint of the 1830s and early 1840s, however, Lavoisier’s theory had two other principal weak­ nesses. First, experiments reported by Benjamin Brodie in 1811 and 1812 were widely used to argue th at the nervous system contributes significantly to the gen­ eration of animal heat. (Brodie kept the heart of decapitated animals beating by forcing air into their lungs with a bellows, and noted that although the blood underwent the usual color change in the lungs, the animals’ bodies cooled rap­ idly.)50 Second, and more serious, precise experiments by Dulong and Despretz in the early 1820s failed to account for all the heat generated in terms of the combus­ tion of oxygen (as measured by the exhaled carbon dioxide).51 As Holmes ob-

served, “one could either treat the difference as a small one to be explained away by secondary factors as Despretz did, or decide with Dulong that the theory had been proven inadequate.”32 Until the appearance on the scene of Dumas and Liebig in 1841 and 1842, most contemporaries concluded that there m ust be other appreciable sources of animal heat than simply combustion. Thus Muller the physiologist regarded as inadequate what he termed the “chemists’” theory of animal heat.33 He concluded from Dulong’s and Despretz’s experiments “‘that there must be other sources of animal heat than respiration, even if one subscribes to the chemical theory of respiration.”34 He explicitly re­ jected the auxiliary hypothesis— “one of the boldest [g ew a g test]”—whereby some of the inspired oxygen is consumed in the production of water in the lungs, an hypothesis, he said, “which could be assumed for so long only by chemists, not by physiologists."35 Like many of his contemporaries, Muller considered the nervous system to be a major source of animal heat. In addition to the contributions of the respiratory and nervous systems, most German physiologists conceded some importance to general processes of material exchange such as digestion, nutrition, and secretion.36 Although more concerned than most to trace all bodily functions ultimately to underlying physicochemical processes, the views of the LIeidelberg professor of anatomy and Physiologyi, Friedrich Tiedem ann, were typical not only in their inclusiveness, but also with regard to his failure even to attem pt a quantitative assessment of the relative importance of the numerous factors considered: As regards the cause of the generation of heat m animals, few phenomena of life have had so many diverse theories advanced about them as precisely these. . . . The physiologists who embrace the modern chemical doctrines think to find the cause of animal heat in the circumstances of respiration, which they likened to a combustion process taking place between the constituents of the venous blood and the oxygen of the inspired air, and whereby the heat liberated combines with the arterial blood and is distributed throughout the body. O ther physiologists seek its source in digestion, nutrition, secretion, even the nervous system. W ithout here entering into the exami­ nation of those theories . . . so much is certain, that all of them afford no satisfactory explanation. Even Crawford’s and Lavoisier’s theory that the heat is the product of respiration— which had enjoyed the approval of most scientists—was found to be insufficient for the explanation of the heat production on the basis of Dulong’s and Despretz’s experiments, which sought to find out to what extent the quantity of oxygen gas consumed in respiration was sufficient for the production of all the heat that animals continuously lose, and they acknowledged still other as yet unknown sources of heat than respiration. The only thing that can be regarded as settled is that the disengagement of heat is an act of life based in the first instance upon the circumstances of the process of nutrition that determine and sustain life. The intake of food and its assimilation through digestion and respiration, the circulation of humors, nutrition and secretion, the exchange of m atter accompanying life, and the persistent changes in composition of the solid and liquid parts that in animals are under the influence of the nerves, all have their share in the generation of heat, and it is erroneous to seek the source of heat

m on e of th e s e processes alo n e. T h e in te n sity of th e d ise n g a g e m e n t o f h e a t a n d th e p ro p erty of m a in ta in in g th e m se lv e s in th e ir ow n te m p e ra tu re re la tio n sh ip s sta n d for a n im als as a w hole in d ire c t p ro p o rtio n to th e g re a ter co m p lex ity of th e ir o rg a n iz atio n , to th e su m of th e m a n ife sta tio n s of force [K ra ft-A eu sseru n g en] th a t th e y ex ert, a n d to th e la t te r ’s in ten sity .’7

Arnold Adolph Berthold, professor of m edicine at G ottingen, likewise assigned th e production of anim al h eat to a variety of sources— th e nervous system, circula­ tion, respiration, m otion, n utrition, secretion, and m ental activity— w ithout ask­ ing further after their causes.38 M any such as Volkmann, H unefeld7 and Lotze, granted prim e im portance to processes of respiration and com bustion while in­ voking th e need for one or m ore of the other suggested causes.39 Volkmann was of th e opinion th a t we can becom e warmer through bodily m ovem ent even w ithout accelerated breathing, again declining to pursue the chain of causes and effects to some u ltim ate source. W hile Volkmann elsewhere paid appreciable atten tio n to general questions of causality, in another particular case— w hether or no t the nervous system (or nervous force) is the “u ltim ate cause” of th e h e a rt’s m otion— he was inclined to let the issue be decided entirely by experim ent, w ithout invok­ ing any energetic or other theoretical considerations.40 Karl A sm und Rudolphi, professor of anatom y and physiology in Berlin, was one of the few explicitly to deny— on th e basis of a com parison betw een different species— any direct role to th e nervois system, preferring (in 1821) to trace the source of anim al heat to changes in com position of the substance of the anim al body, nam ely respiration, nu tritio n , digestion, and (in 1828) two additional processes accom panied by a heat-producing electrical process: m uscular m otion and nervous activity.41 Indicative of the changes in physiological thinking th at followed Liebig’s forays in to th e field (to be exam ined below), in 1842 organic chem ist Franz Sim on ex­ plained anim al h eat in term s of the respiration of oxygen, th e activity of the nerves— b o th considered to be aspects of “the general transform ation of sub­ stance IStoffw andel)”— and the vigorous m otion of the m uscles,42 whereas in 1843, after reviewing Liebig’s epoch-m aking book, Organic Chemistry in Its Appli­ cation to Physiology and Pathology (1842), h e concluded th a t the sole source of anim al h eat is the com bustion of carbon and hydrogen: “To consider th e heat generated as th e effect of the nervous system, whereby an exchange of m atter [Stoffwechsel] is wholly excluded, m eans to call forth an activity ou t of nothing. To consider the contraction of the m uscles as a source of heat is equally inadm is­ sible, for th e m otion cannot take place w ithout a certain expenditure of force, and th e organs of m otion obtain this force only as a result of the exchange of m at­ ter.”45 T h e m atter-of-faetness of Sim on’s reasoning in 1843 contrasts dramatically with th e universal weakness of rigorously pursued causal and energetic considera­ tions through th e 1830s. A m inority of scientists, of whom th e m ost im portant was Berzelius, took Brodie’s line of reasoning a step further and sought to trace the source of animal heat to electrical activity. For Berzelius, at least, this was surely a reflection of his prior preoccupation w ith electrochem ical theories of reaction and com bination. Although it is difficult to extract a clear positive theory of anim al h eat from

Berzelius’s influential Textbook o f Chemistry, he was decisive in his rejection of the then m ost favored explanation in terms of com bustion. His extensive treat­ m en t of the subject reveals just how com plicated and uncertain the experim ental situation was in th e 1830s.44 Given that, his failure adequately to m otivate his unusually unqualified rejection of Lavoisier’s theory is as noteworthy as it is puz­ zling. C iting the inability o f D espretz’s experim ents to account for more than 70 to 90 percent o f the heat in terms of respiration, he concluded in 1831 as follows: N evertheless it is certain th a t b o th his and D ulong’s experim ents indicate th a t the developm ent of h e a t in th e body m ust have still oth er sources, and th a t, if th ere is such another source, the entire anim al heat is certainly to be derived from it. Respira­ tion th e n has no other part in it th an th a t it, like th e rem aining processes in th e body, prepares th e conditions w ithout w hich th e developm ent of h eat could n ot take place; b u t an im m ediate developm ent of heat through transform ation of th e air in th e lungs appears n o t to take place. Accordingly, th e idea first proposed by Brodie th a t th e developm ent of h eat, like all vital phenom ena, is determ ined by th e nervous system appears at present m ost in agreem ent with th e result of the experim ents perform ed; and if th e effects of the nervous system th e n depend on a m eth o d peculiar to itself of em ploying th e influence of th e opposing electricities, it th u s appears to follow th a t th e developm ent of h eat could here depend on their recom bination everywhere nerves go and th u s could have th e sam e cause as w ith com bustion, b u t w ith th e difference th a t entering in to a chem ical com bination is n o t necessary here for th e liberation of th e opposing electric­ ities.45

In 1840 he replaced the first paragraph w ith the following: It is clear, now, from w hat was earlier set forth th a t such an oxidation process does n o t take place in th e lungs, and th a t th e cause of anim al h e a t m ust lie in another process o f h eat developm ent as y e t still wholly unknow n to us. T h ese calculations are m eanw hile of great value because they show th a t we also can n o t derive th e animal h e a t from th e com bination of absorbed oxygen w ith organic m a tte r during th e circu­ lation of th e blood, for even u nder th e presupposition th a t as m uch h eat was devel­ oped through this com bination as w ith the . . . transform ation of carbon to carbonic acid and of hydrogen to water, this would still n o t be sufficient. T here m u st therefore b e still another source for th e h e a t.46

Berzelius’s reasoning is scarcely cogent: D u lo n g ’s and D esp retz’s experim ents dem onstrate that there m ust be another source of anim al heat than com bustion; if there is, it m ust be the source of all th e heat produced. In 1831 he seem ed to imply that acceptance of the com bustion theory of animal heat necessitated ac­ ceptance of th e lungs as the site of com bustion; since he (quite rightly) rejected the latter, he also (illogically) rejected th e former. In 1840 he reasoned that even if the com b u stion took place in th e circulating blood, it still w ould not cover all the heat produced, h ence one still needs to invoke another source. H e had the nerves m ediate th e action o f electricity in producing animal heat, yet som ehow he

dissociated th e production of electricity from any an teced en t chem ical change.47 R esponding to Liebig’s 1841 paper, “T h e Vital Process in the Anim al, and the A tm osphere,” which regarded th e com bination of atm ospheric oxygen with the com ponents of th e blood as th e sole source of anim al heat, Berzelius replied th at h ea t is produced at m any places in th e body— and by processes other than chem ­ ical com binations, such as electric currents and friction; thus “it is m ore th an a m ere probability th a t th e principal source of h eat in the anim al body is o th er than th rough chem ical com bination, although th a t co n trib u tes.”48 In his published review of Liebig’s A nim al Chem istry he continued to oppose Liebig’s view, citing th e influence o f m ood on the tem perature of parts of th e body and again appeal­ ing to Brodie’s and others’ results “which are irreconcilable w ith it and which show th at th e developm ent of h eat in th e anim al body appears to b e a function governed by th e eighth pair of nerves.”49 His a ttac h m e n t to the electrical explana­ tio n of anim al h ea t becam e firmer even as he took refuge beh in d an agnostic w hat-m akes-you-think-w e-even-know -all-the-possible-sources-of-heat, in p articu ­ lar w ith respect to the source of th e powerful electric currents generated in the nervous system of certain fish.50 C iting experim ents of Becquerel and Breschet, Berzelius h ad argued in 1840 th a t m uscular contraction could be regarded as an o ther source of anim al h e a t.51 In 1835 the two French scientists had explicitly co n n ected this experim ental finding with speculation as to the possible electrical origins of anim al h ea t.52 A uthors of physics texts of the period regularly addressed th e issue of anim al h ea t in a few sentences in th e section on heat. At one end of th e spectrum of opinions was H eidelberg professor of physics, Georg W ilhelm M uncke, whose w holehearted early support for Lavoisier’s theory was unusual: The cause of animal heat does not lie in an inheritance, nor in a friction of the blood in the blood vessels, nor in a fermentation, nor in the motion of the muscles, nor even in the immediate activity of the brain, as Brodie wished to conclude from his experi­ ments but as refuted by Emmert, even though respiration is a consequence of the activity of the nerves. It is, rather, mainly to be derived from the chemism of the vital process, whereby the consumption of oxygen gas and formation of carbonic acid through respiration is to be regarded as the chief means. . . . The vital process of animals can thus be regarded as a slow combustion process, although the oxygen gas is not decomposed exclusively in the lungs, but in the whole body.53 Twelve years later, however, in his long article on heat for G ehler’s Physical D ic­ tionary, M uncke qualified his conclusion by recognizing (unspecified) processes of assim ilation as a further source of anim al h e a t.54 Halle professor of physics Ludwig Friedrich Kam tz accepted the apparent lim i­ tatio n im posed on Lavoisier’s theory by D ulong’s and D espretz’s experim ents, and speculated th a t “electrical processes" also play a role, “since h eat is produced by th e decom position of the n u trien ts and the other hum ors of th e body”— tacitly im plying his acceptance of an electrochem ical u nderstanding of chem ical change.55 At th e o ther end of the spectrum was Andreas Baum gartner, professor of m athem atics and physics in Vienna, who, while conceding som ething to gener-

ally recognized causes, d enied that organic processes can b e fully understood in physical term s.56 By the 1830s, very few scientists of any stature were so categorical in their denial of the applicability of the laws o f chem istry and physics to the explanation of physiological processes— leaving aside m ore difficult problem s of generation and em bryological developm ent. A prom inent instance of such a denial was Humphry Davy’s discussion of respiration and the problem of anim al heat in his p osthu­ m ously published philosophical reflections, C onsolations in Travel. T he book ap­ peared tw ice in Germ an translation during the 1830s (in 1833 and 1839), and m ight w ell have caught M ayer’s atten tion . O n e of the interlocutors of the dialog, Eubathes, d efended the com bustion theory, w hich he assigned w ith nationalistic pride to Joseph Black: First, then, in all known chem ical changes in w hich oxygen gas is absorbed and car­ bonic acid gas form ed, heat is produced . . . . A nother circum stance in favour of it is, th a t those anim als w hich possess th e highest tem peratu re consum e th e greatest q u an ­ tity of air; and, u n d er different circum stances of action and repose, th e heat is in great m easure proportional to th e q u an tity of oxygen consum ed. T h en , those anim als w hich absorb th e sm allest quan tity of air are cold blooded. A nother argum ent in favour of Dr. Black’s opinion is, th e change of colour of blood from black to red; which seems to show th a t it loses carbon.’7

But D avy’s spokesperson, the U nknow n, w ould have n one o f these standard argu­ ments: I will not allow any facts or laws from th e action of dead m a tte r to apply to living structures; th e blood is a living fluid, and of this we are sure, th a t it does n o t b u rn in respiration. . . . [T]hose anim als th e life of w hich is m ost active, possess m ost heat, w hich may be th e result of general actions, and n o t a particular effect of respiration. Besides, a distinguished physiologist [Mr. Brodie] has rendered it probable, th a t th e anim al h ea t depends m ore upon th e functions of th e nerves th an upon any result of respiration. T h e argum ent, derived from change of colour is perfectly delusive . . . . [T ]he m o m en t inorganic m a tte r enters into th e com position of living organs it obeys new laws. . . . Respiration is no m ore a chem ical process th an the absorption of chyle; and th e changes th a t take place in the lungs though th ey appear so sim ple may b e very com plicated; it is as little philosophical to consider th em as a m ere co m bustion of carbon, as to consider th e form ation of m uscle from th e arterial blood as crystalliza­ tion. T here can be no d o u b t th a t all th e powers and agencies of m a tte r are em ployed in th e purposes of organization, b u t th e phenom ena of organization can no m ore be referred to chem istry th an those of chem istry to m echanics.58

Such views w ould have seem ed increasingly out of place to Germ an scientists during th e course of the 1830s. AU the more rhetorically m isleading, then, was Mayer’s im putation in 1845 that the “vitalist" views of the seventy-three-year-old professor of m edicine at Erlangen, G ottfried Christian Reich, were som ehow typ­ ical of the conceptual confusion he had to con ten d with:

W h a t bizarre ideas th e so-called vitalists can even today com e u p w ith can b e seen for exam ple in R eich’s Textbook o f Practical M edicine According to Chem ical-Rational (?) Principles (Berlin, 1842). Reich considers anim al h e a t to be an inh eritan ce given to th e new born to take with it along th e way!’9

Q uite th e contrary; indeed, com pared to th e situation during the previous decade, by th e early 1840s th e scientific consensus had shifted dram atically in the direc­ tion of a self-conscious determ ination to em ploy only chem ical and physical prin­ ciples in th e explanation of physiological processes.60 O ne of the leaders in this m o v e m e n t was Frangois M agendie, whose influential Elementary Sketch o f Physi­ ology was published in num erous editions and translations (including two into G erm an in th e years 1834-36). T hus it is n o t surprising th at, am ong pre-1840 authors, M agendie was one of th e m ost enthusiastic supporters of Lavoisier’s chem ical theory of anim al heat, to the detailed exposition of which he devoted ten pages of his S ketch.61 However, he, too, was m oved by D espretz’s experim ents to regard respiration as only th e principal cause of anim al heat: o th er sources of h eat in th e anim al econom y were (probably) th e friction of diverse parts of the body, th e m ovem ent of th e blood and the rolling of its particles against one an ­ other, an d th e p henom ena of n u tritio n .62 It was n o t until 1841 th a t a prom inent investigator of organic processes came o u t decisively for the unqualified sufficiency of the com bustion theory of anim al heat. In August of th a t year, in a widely published lecture given at the end of his course in organic chem istry at the Ecole de M edecine in Paris, Jean-Baptiste D um as asserted th a t th e explanation of the physiological process of respiration was falling m ore and m ore u n d er the general laws of inorganic nature.63 To make th a t claim good, he had to explain away th e apparent discrepancy in the results of D ulong’s and D espretz’s experim ents: If anim als do n o t possess any particular power for producing organic substances [matieres], do they at least have this special and singular power of producing heat w ithout the expenditure of substance th a t has been attrib u ted to them ? You have seen, in discussing the experim ents of D ulong and D espretz, you have positively seen th e contrary to b e th e case. T hese able physicists have assum ed th a t an anim al placed in a cold-w ater calorim eter em erges from it w ith exactly th e same tem p eratu re it possessed on entering; a th in g absolutely impossible, one knows today. It is this chilling of th e anim al, w hich they did n o t take into account, th a t in their tables expresses th e excess of h ea t attrib u ted by th em and by all physiologists to a calorific power particular to th e anim al and in d ep en d en t of respiration. It has been d em onstrated to m e th a t all anim al h eat com es from respiration; th a t it is m easured by th e carbon and hydrogen burned. It has been d em o n strated to me, in a word, th a t th e poetic assim ilation of the railroad locom otive to an anim al rests on m ore serious foundations th a n one perhaps thought. In b o th , co m bustion, h eat, and m otion, three connected and proportional phenom en a.64

P rom pted in p art by D um as’s challenge to w hat he regarded as his intellectual property, Liebig soon entered th e lists in defense of a m odified version of La-

voisier’s oxygen theory of respiration and anim al heat. Liebig took steps to assure th a t his som ew hat idiosyncratic views on the relationship betw een nutrition, res­ piration, and anim al heat would reach a large audience, publishing th em in pro­ gressively expanded versions first in D ecem ber 1841 in two “C hem ical L etters” in the widely read Allgemeine Zeitung and then in an im portant paper on “T h e Vital Process in th e Anim al, and the A tm osphere” in his Annalen, followed three m o n th s later by a second paper in th e A nnalen on “N u tritio n and th e Form ation of Blood and Fat in th e Animal Body.” T hese two papers form ed the first part of his epoch-m aking book, Organic Chem istry in Its Application to Physiology and Pathology— b e tte r known after the title of th e second and subsequent editions as Liebig’s A nim al Chemistry— published in July 1842. After 1842 the conceptual terrain surrounding this issue had been com pletely relandscaped. To be sure, Liebig h ad been investigating this constellation of issues before being challenged by D um as. Kremer has argued th a t Liebig’s Agricultural Chemis­ try o f 1840 treated respiration as a kind of Verwesung— th a t is, dry decay in the presence of oxygen— both being thus regarded as slow processes of com bustion at relatively low tem peratures.65 C iting data on the proportion of carbon, hydrogen, and oxygen in wood, Liebig reasoned th at if atm ospheric oxygen reacts directly w ith carbon in th e wood during the decay process, th en th e proportion of carbon should steadily decrease, whereas it actually increases,66 Such, he concluded, is th e general nature of th e slow com bustion of hydrogen-rich substances: “It is evidently th e hydrogen w hich is oxidized at the expense of th e oxygen of th e air, [while] th e carbonic acid com es from the elem ents of the wood; never and under no circum stances does carbon com bine at norm al tem peratures directly w ith oxy­ gen to form carbonic acid.”67 He later explicitly referred to the Verwesungsprocefh th a t takes place in the lungs: w ater is form ed there, no t carbon dioxide, though a portion of th e uncom bined oxygen is absorbed into th e blood.68 This work did n o t, however, purport to provide an adequate account of either respiration or anim al h eat, and Liebig addressed those topics only in passing. Strictly speaking, too, Liebig never claim ed th a t respiration overall was a kind of decay process, only th a t such a process takes place in the lungs. At th e end of a paper on nitrogenous n u trien ts published in the same m o n th as D u m as’s lecture, Liebig addressed m ore directly th e question of the sources and functions of oxygen in th e anim al economy. T h e discrepancy others had n oted betw een th e am o u nt of oxygen inspired and th e greater oxygen co n ten t of the carbon dioxide exhaled, a discrepancy th a t bedeviled Lavoisier’s theory of anim al h eat, Liebig solved by arguing th a t oxygen m ust be rem oved from the nonnitrogenous food anim als consum e before it can be stored as fat.69 T h e purpose of this stored fat is to pro tect the body against th e ever-present destructive force of a t­ m ospheric oxygen through th e production of carbon dioxide. He closed his paper w ith a brief m en tio n of anim al heat: “In a second paper I will attem p t to show th a t th e carbon of nonnitrogenous foods such as starch and sugars is em ployed in respiration and in the production of anim al heat, th at th e latter stands in the closest connection w ith the carbon of foods.”70 M uch of his work during the next year was an elaboration of th e connections here briefly sketched.

Liebig’s views on anim al h eat were only one aspect of a broad picture of the chem ical changes taking place w ithin the anim al organism and betw een it and its environm ent. N or were those views as sim ple or unam biguous as they m ight a p ­ pear from his sum m ary p ronouncem ent th a t “all vital activities derive from the reciprocal action of the oxygen of th e air and the co nstituents of th e food.”71 Especially since he had just been talking ab o u t the relationship betw een th e car­ bon ingested as food and th a t exhaled as carbon dioxide, his first explicit pro­ n o u n cem en t w ith respect to the cause of anim al h ea t seems to b e a clear endorse­ m e n t of Lavoisier’s theory: T h e interaction betw een th e c o n stitu e n ts of th e food and th e oxygen dissem inated in the body thro u g h th e circulation of th e blood is the source o f anim al heat. T his higher tem p eratu re of th e anim al body— or, if on e will, disengagem ent of h ea t— is everywhere and u nder all circum stances th e result of th e co m b in atio n of a com bustible substance w ith oxygen. In w hatever form carbon m ay com bine w ith oxygen, th e act o f co m b in a tio n can n o t take place w ith o u t being accom panied by th e developm ent of h eat; regardless of w hether it occurs slowly or rapidly, th e am o u n t of h ea t liberated rem ains an invariable q u anti ty.72

W hile it rem ains true that Liebig assigned the entire production o f animal heat to chem ical processes involving oxygen, those processes were m ore com plex than simply th e absorption of oxygen through th e lungs. H ence it is n o t surprising th at Liebig felt confident in discounting as valueless scientists’ previous a ttem p ts to correlate th e am o u nt of oxygen consum ed w ith th e h eat produced by an anim al in a given tim e .73 T hose additional processes— th e absorption of oxygen through th e skin and th e release of oxygen in th e production of fat from starches and sugars— were dealt w ith at any length only in th e second of Liebig’s two related p apers.74 Before we tu rn to it, however, it will be useful to review w hat Liebig believed th e fu n ctio n of respiration to be. F undam ental to Liebig’s understanding of th e anim al econom y was his concep­ tion of oxygen n o t as th e sustainer of life b u t as an agent against whose destructive tendencies th e vital processes are in co n stan t struggle. T h u s the carbonaceous m aterials oxidized in the body serve n o t only to generate h eat, b u t also to ward off th e potentially harm ful effects of oxygen on th e body as a whole. T h u s Liebig’s otherw ise strange references to “th e carbon indispensable for respiration” and to “th e carbon, which protects our organs from th e influence of oxygen and which generates in th e organism th e h eat indispensable to life.”75 In accordance w ith these views, th e increased oxygen taken in by people living in the polar regions— Liebig ad o p ted th e generally accepted explanation in term s of th e greater oxygen c o n ten t per volum e of colder and th u s denser air— is com pensated by th e greater carbon c o n te n t of their fatty foods. A t the sam e tim e, th e oxidation of this fat supplies th e extra h eat needed to keep th em warm in a colder environm ent. This fo rtu n ate accom m odation of food to clim ate is, in Liebig’s words, th e provision of “an infinite w isdom .”76

If an anim al consum es m ore carbonaceous m atter th a n can be g o tten rid of through oxidation, th e excess is stored in the body as fat. O n th e basis of a com ­ parison of th e chem ical com position of fats on th e one hand and starch, sugars, gluten, album in, and legum in on the other, Liebig argued th at anim als produce fat by rem oving some of the oxygen from th e latter group of foodstuffs.77 T h e p r o d u ctio n o f fat d e p e n d s on a lack o f oxygen ; on ly in it, in th e very fo rm a tio n o f fat, th ere is m a d e availab le to th e org a n ism a so u rce o f ox y g en , a n e w c a u se o f h e a t p ro d u ctio n . T h e o x y g e n lib er a ted as a resu lt o f th e fo r m a tio n o f fat lea v e s th e b o d y as a c o m ­ p o u n d o f carb on or hyd rogen; w h e th e r or n o t th is carb on o r h yd rogen w as taken from th e very su b sta n c e w h ic h also c o n v e y e d th e o x y g en or from a n o th er c o m p o u n d , just as m u c h h e a t m u s t b e d e v e lo p e d th ro u g h th is fo r m a tio n o f ca rb o n ic acid or w ater as if w e h a d b u rn ed an eq u a l q u a n tity o f carb on or h y d ro g en in th e air or in o x y g e n g a s .78

In support of this last claim Liebig adduced ferm entation and putrefaction as examples of chem ical processes in w hich the release of carbonic acid and w ater is accom panied by th e production of heat, “exactly as when carbon and hydrogen com bine directly with oxygen.”79 T he oxygen from fat does not, it seems, pass into th e anim al’s body as elem ental oxygen. T hus, he concluded, T h e fo r m a tio n o f fat, co m p a red w ith w e ll-k n o w n an a lo g o u s p h e n o m e n a o f th e se p ­ aration o f o x y g e n , is accord in gly a c c o m p a n ie d b y a d e v e lo p m e n t o f h eat; it restores to th e an im al b o d y a certa in q u a n tity o f th e a tm o sp h e r ic o x y g en in d isp e n sa b le for th e v ital p r o c esses, an d it d o e s so in all th o s e cases w h ere th e o x y g en in sp ired th r o u g h skin an d lu n gs is n o t su ffic ie n t to tran sform in to carb on ic a cid th e carb on p resen t and su ita b le th ereto . In th e fo r m a tio n o f fat th e v ital force cre a tes for its e lf a m e a n s to c o n fr o n t th e lack o f [b o th ] o x y g e n an d th e h e a t n ecessary for th e vital p r o c e s se s.80

T h u s when Liebig asserted (som ew hat oddly) th a t “an oxidation process is the sole and chief source of anim al h e a t,” he had in m ind a m ore com plex process than m any readers, bo th his and our contem poraries, seem to have understood.81 For exam ple, Valentin’s recapitulation of Liebig’s ideas m ade no m ention of the role of fat production; “Liebig, in particular, has em phasized the combustion pro­ cess taking place in the capillaries o f the body as the cause o f anim al heat.” S im on’s review o f Liebig’s book presented it as rightly asserting th a t the sole source of anim al h eat is th e com bustion of carbon and hydrogen. And W underlich associ­ ated Liebig with those who wrongly held th a t oxidation is th e only source of anim al heat. Nor have m ore recent com m entators n o ted this qualification in Liebig’s acceptance of Lavoisier’s theory of anim al h ea t.82 In 1844 Gabriel G ustav Valentin, professor of physiology at Bern, asserted th at “th e principal— indeed, probably the sole— cause of h u m an beings’ proper h ea t is th e com bustion process taking place in our body.”83 Two years later he was m ore cautious: th e com bustion hypothesis seems sufficient only as long as one looks at th e m ost general phenom ena, b u t it runs into trouble as soon as one exam ines the

details. H e believed th a t th e h ea t produced by th e com bustion of th e elem ents in a com pound is usually less th an th a t of the elem ents burned separately— im plic­ itly calling into question the significance of D ulong’s and D espretz’s experi­ m en ts— and he n o ted an experim ental anom aly w ith respect to the carbon diox­ ide produced by starving and healthy doves versus the h ea t they produced. H e also allowed th e nervous system to play some role in th e production of anim al heat. N evertheless, h e regarded an appeal to “still wholly unknow n influences of the nervous system ,” as opposed to unknow n phenom ena of n u tritio n , as a “confes­ sion of ignorance,” and th e com bustion hypothesis rem ained “the only certain guide capable in th e future of leading to th e solution of the riddle.”84 Reservations such as W underlich’s and V alentin’s soon becam e increasingly less com m on, and by 1845 Karl Vierordt— th e n a physician in Karlsruhe, later professor of anatom y and physiology at T iibingen— could confidently assert th at “th e chem ical theory of anim al h eat [is] com pletely tru e .”83 But w hatever the rem aining differences of opinion m ight have been, by 1845 the range of debate over anim al h ea t had becom e circum scribed by a general and explicit acceptance of th e need to consider all organic processes w ithin th e context of Stoffwechsel— an issue to which I will shortly return. It is notew orthy th a t th e dram atically in­ creased acceptance of Lavoisier’s theory of anim al h ea t by m id-decade was no t the result of any significant new data since th e tim e of D ulong and D espretz, b u t rather reflected a new way of thinking. Vierordt asserted th a t th e idea th a t anim al h eat m ight derive from other than physical causes, causes belonging exclusively to anim al life, no longer had any force: th e new physiology had cleansed itself of all progress-im peding m ysticism and rom anticism .86 H e p u t the issue in term s of a self-conscious appeal to physics an d chem istry as providing th e only valid m odels for a scientific physiology: W h ile som e derived th e source o f anim al heat from m an ifold causes utterly peculiar to th e organism , such as th e vital force or the nervous force, and even b elieved thereby to give an explanation of th e problem at hand, others rightly transferred from physics and chem istry th e facts derived through precise observation concern in g th e origin and distribution of heat to the circum stances of our body, w ith o u t, however, having b een in a p osition to com p letely overcom e th e extraordinary difficulties w hich op p ose the precise solution o f this com p licated and difficult q u estion on th e (naturally alone true) basis of experim en t. O ne th u s finds repeated here, too, the struggle w hich we en cou n ter in every individual branch of physiology, w hereby n o th in g less is at stake than th e qu estion of w hether the p h en om en a and processes in the organism are to be explained in term s of abstract causes existing only ideally but n o t in reality, or in term s o f facts w hose validity has b een proven; in a word, w h eth er o n e w ishes to investigate in the spirit of th e old sterile scholastic study of nature or according to th e m eth o d of the exact, vital natural scien ces.87

T h e issues were fundam entally ideological. Carl Vogt, too, explicitly condem ned th e alleged use of a vital force to explain anim al heat. It was, he said, a “refuge” invoked to explain th e incom prehensible, an “unknow n X" lurking in th e back­ ground th a t receded as science progressed: reliance on such a m ode of explanation

“no longer has any scientific value, it is only another word for ignorance [eine Umschreibung der U nwissenheit].” In a paper of 1845, Leibig rather overplayed his hand in creatively reinterpreting various experim ental findings in order to explain away th e discrepancy in D ulong’s and D espretz’s results. A sserting correctly that, on th e basis of this discrepancy, “physiologists and m any chem ists have assum ed an additional source of h eat in th e anim al’s organism th a t, alongside th e inspired oxygen, m aintains th e anim al’s tem p eratu re,” he announced his goal to be the d em onstration th a t “th e assum ption of the existence of a cause of h eat form ation in th e anim al body inexplicable according to known physical laws contradicts the positive facts,” incorrectly im plying th a t deficiencies in Lavoisier’s theory were generally being answered in a scientifically unacceptable fashion— by which his readers probably understood th e {here unnam ed) vital force.88 A lthough th e physiological functions com m only attrib u ted to a vital force will be the topic of a later section, it should be em phasized here th at, in the decades before 1840, virtually no G erm an scientist invoked a vital force in th e explanation of anim al heat: only the opponents of th e vital force m ade th a t connection. As Kremer rightly insisted, H elm holtz’s co n ten tio n “th a t it was S tahl’s concept of vitalism , which would have m ade th e anim al a perpetuum mobile, th a t h e was assailing” rings hollow, since “in 1845, no physiological writer of note was defend­ ing Stahl. If H elm holtz had th e Lebenskraft of M uller or Berzelius in m ind, he could have chosen a b e tte r arena th an anim al heat to m ake his criticism , [since] . . . neith er of these m en explained anim al heat in stridently vital term s.”89 T he same judgm ent applies m ore generally to other writers of th e preceding decades. In pretending th a t th e vital force had been used to explain anim al heat, and th at thus th e explanation of th a t heat solely in term s of chem ical processes repre­ sented a defeat for the vital force— indeed the defeat o f the vital force— reduc­ tionist-m inded physiologists also tacitly pretended th a t the agency of a vital force or soul was everywhere disproven or (better yet) rendered scientifically illegiti­ m ate. D espite th e increasingly taken-for-granted assum ption th a t organic processes m ust be explained in term s of specific chem ical transform ations, only gradually does one begin to encounter a principled appeal to energetic considerations. T he long section on anim al heat in th e second edition of Valentin’s Textbook o f Physi­ ology of 1847 reported quantities of experim ental data b u t en tertain ed no conservation-of-energy considerations, despite th e fact th a t Valentin knew and cited M ayer’s Organic M otion of 1845.90 Indeed, in a report w ritten th e previous year he had spoken very favorably of M ayer’s work, though h e apparently quite m issed the significance of M ayer’s theory of force: J. R. Mayer, in a small work w ritten w ith great perspicacity an d profound physical knowledge, has developed a series of views concerning general physical and physiolog­ ical relationships. In it he seeks to dem onstrate generally how every perform ance [of work] is connected w ith a proportional conversion of agency or substance, and how this principle can also be applied to organic m otions. Accordingly, th e h eat form ation d eterm ined by th e conversion of substance is expended partly on th e [production of]

m echanical effect, partly on th e production of [organism s’] proper h eat. In th e con­ text of these considerations M ayer declares h im self opposed to th e existence o f a special vital force, and he seeks to d em onstrate th a t th e principal scat of th e co m b u s­ tion process of anim als is in th e b lood itself, and th a t a m uscle achieves m ore m ech an ­ ical effect th e m ore copiously and quickly it is suffused w ith b lo o d .91

Valentin m aintained that proof of the com bu stion theory o f anim al heat depends on a strict quantitative experim ental dem onstration o f the equivalence b etw een the production and loss of heat in the organism .92 His insensitivity to energetic considerations is seen dramatically in his response to M ayer’s criticism of his ex­ planation— in term s o f posture— of why m ou n tain clim bers, runners, jumpers, and dancers breathe harder.93 H e replied to Mayer in th e con text o f a criticism of teleological explanations in physiology: Daily experience teaches, for exam ple, th a t w hen clim bing m o u n tain s we easily break o u t in sweat and experience throbbing of th e h eart an d difficulty in breathing. If one says th a t this happens because n atu re intensifies th e com bustion process for th e sake of greater m echanical action, one thereby gives n o t an explanation b u t m erely a description [Umschreibung] appropriate for th e individual case of th e reck­ oned m ode of action of th e organism . If one succeeded, however, in d em onstrating why th e h eart and th e breathing m uscles m u st just th e n increase th eir activity, th en th e way would be open to true understanding. AU these an d sim ilar teleological con­ ceptions do n o t solve th e tasks w hich scientific investigation m u st set itself.94

Valentin bad clearly m issed th e energetic thrust of M ayer’s argument. T h e physical and chem ical changes in the blood in health and disease; the nature and fu n ction o f respiration; the sources of animal heat: those were the m ost im portant of an in terconnected nexus of issues against w hich on e m ust situate M ayer’s earliest physiological observations and reflections. However, there were still other issues o f som e contem porary visibility relating to the blood which could conceivably have played a role in stim ulating M ayer’s sensitivity to the cen­ tral issue of causality as it related to physiological explanations. O n into the 1820s and 1830s there con tinu ed to b e discussion in Germ any over w hether blood cor­ puscles or the entire b lood itself possesses th e power of self-m otion.95 In 1828 Rudolphi protested that he could form no con cep tion of the supposed m otive force proper to th e blood, and rejected the idea as an unnecessary deus ex m a­ c h i n a l Critics of the late 1830s typically rejected such a possibility by appealing to the unacceptability of the self-caused m otion of such a fluid. W rote Volkmann in 1837: Several respected physiologists have a ttrib u te d to th e blood a life of its own and, as a consequence, m otive force. A ccording to them th e blood is supposed to be con­ strained by an internal principle into circulation even w ithout th e participation of the heart. T he experim ental grounds on w hich this view was based have already been discussed above, w here we show ed th a t circulation does n o t take place w ith o u t th e participation of the heart. M oreover we are unable to co n n ect any clear concept with th e view just m entioned. As will be shown below, th e blood consists of serum an d of

corpuscles suspended in it. T o attribute so highly d eveloped a life to such a m ixture that au ton om ou s lo co m o tio n could take place is against every analogy.9'

M ay er’s u niversity frien d an d la te r p rofessor of surgery at M arburg, W ilh e lm Roser, fo u n d o ccasion th e follow ing year in his d isse rta tio n to criticize th e alleged propulsive force of th e b lo o d as (in essence) inconceivable: “D esp air of being able to explain th e e n tire c ircu latio n acco rd in g to physical laws led to K ielm ey er’s p o sitin g of a propulsive force. H ow ever little th e a u to n o m o u s m o tio n of a liq u id agrees w ith o u r [general] n o tio n s, th is h y p o th e sis was n ev erth eless widely ac­ c e p te d .”98 A nd to illu strate p e o p le ’s a c c u sto m e d in clin atio n to m ysticism a n d th e n eg lect of th e logical tra in in g o f m ed ical sc ie n tists, S ch leid en q u o te d an anony­ m ous passage th a t spoke approvingly of th e a u to n o m o u s m o tio n of th e blood corpuscles.99 In c o n tra st to th e se p rin c ip le d o b je c tio n s to th e idea of th e b lo o d ’s self-m o tio n , Jo h an n es M u lle r’s re je c tio n of K ielm eyer’s Propulsionskraft was b ased for th e m o st p a rt o n h is in te rp re ta tio n of n eg ativ e e x p e rim e n tal fin d in g s.100 B ut it was still an issue th a t w a rra n te d discu ssio n in th e 1830s. W h ile n o t exactly ad v o catin g th e self-m o tio n of th e b lood, B urdach searched for a n o th e r p ropulsive force to supply w h a t h e th o u g h t was an extra p u sh to m ove venous b lo o d from th e p erip h ery of th e body to th e h e a rt. S peaking of th e ob­ served b e h a v io r of b lo o d corpuscles o u tsid e th e body, h e w rote: D uring the normal con d ition s of life they do n o t m an ifest their ten d en cy to act a d h e­ sively and repulsively toward each other: there m u st therefore be so m eth in g external to th em w hich suppresses this ten d en cy and com pels th em to m ove in a determ inate, uniform direction; this im pulse lies in the heart, as th e central p oin t o f th e blood system ; b u t since this cannot alone b e active, a second and still m ore essential im pulse m ust thus proceed from the opposite poin t, from the periphery of th e b lood system or from th e organic structures external to it .101

T h is passage rem in d s us, too, th a t th e lan g u ag e of c e n te r an d periphery, of ce n ­ trifugal an d c e n trip e te l m o tio n s, was a c o m m o n p la ce in discussions n o t only of c irc u la tio n , b u t also o f th e nerv o u s sy ste m .102 T h e fam iliarity w ith su ch te rm in o l­ ogy from a physiological a n d a n a to m ic a l c o n te x t m ay have b e e n a fa c to r in its appeal to M ayer as h e trie d to co m e to te rm s (literally!) w ith central-force m o tio n s.

2 Sources

of

O

r g a n ic

A c t iv i t y

T h e in te rc o n n e c te d processes of re sp ira tio n a n d th e g e n e ra tio n of a n im al h e a t are only tw o a m o n g th e o rg an ism ’s m an ifo ld life-su stain in g activities. In d e e d , in th e 1830s an im al h e a t was typically assigned to a co llectio n of diverse organic activi­ ties: n o t only re sp ira tio n a n d o x id a tio n , th e c h ie f agency, b u t also th e a c tio n of th e nervou s system , d ig estio n a n d n u tritio n , m u sc u la r c o n tra c tio n , a n d th e m o tio n of bodily fluids. O th e r organic activ ities— typically th e m ore strongly teleological, su ch as g e n e ra tio n , em bryological d e v e lo p m e n t, th e p reservation of th e b o d y ’s

integrity m th e face of external challenges, and th e direction of com plex chem ical transform ations— were routinely attrib u ted to the operation of som e kind of vital force. Som e regarded a distinct will or soul or m ental force as capable of produc­ ing certain organic m otions and activities, though w hether this producing m eant just initiating or also sustaining was a question not usually explicitly addressed. In general, physiologists of the period only gradually becam e sensitive to questions of w hat m ight be called energetic causality: if an organism produces some kind of m aterial change in th e world— for example, when it moves som e part of itself or does work— th e n there m u st have taken place a physical change elsewhere in the system corresponding in som e m easure to th e achieved effect. O lder writers typi­ cally regarded certain organic activities, such as the production of m otion, as due to causes largely ungrounded in either energetic or m aterial transform ations— a way of thinking th at was to becom e increasingly unacceptable during th e 1830s. T h u s A u ten rieth ’s highly regarded Handbook o f Empirical H um an Physiology (1801-1802) characterized th e distinction betw een a living and a dead body in term s of th e form er’s ability to produce m otion “w ithout this m otion having been caused by visible dissociation and separation of its parts”; we thus conclude th a t “an originally active, m otion-causing force is present w ithin th e body,” a force we call th e soul.103 A u tenrieth was m ore concerned w ith classifying the active forces as either internal or external, belonging either to th e soul or to extrinsic stim uli, th an w ith tracing th eir energetic or m aterial conditions. Twenty years later, in 1821, Ferdinand G ottlob G m elin, professor of m edicine and natural history at T ubingen and likewise one of M ayer’s m ajor professors-tobe, could still m aintain th a t som e organic m otions are ind ep en d en t of m aterial changes in the body: “A large n u m b er of anim al p henom ena— indeed precisely those through which life reveals itself to th e outside— consist in m otions which result from an internal force and [which take place] w ithout lasting change in the m aterial m oved.”104 Following A lbrecht von H aller’s eighteenth-century lead, G m elin analyzed organic m otions into contractions and expansions due, respec­ tively, to th e action of two basic organic forces, irritability and what h e term ed the “turgor vitalis.”105 T hose, however, were “forces” in the classical sense of being properties of (here organic) m atter. Such views died hard. D espite th e fact th a t Friedrich T iedem ann was the first and m ost im p o rtan t G erm an physiologist of the 1830s to m ake processes of m ate­ rial exchange th e centerpiece of his work, he nevertheless failed to bring any ener­ getic considerations to bear on his treatm en t of m otion in anim als, which he was thus prepared to regard as capable of generating m otion via th e action solely of th eir will, h ence “every living body is to be likened to a p erpetuum m obile.”106 W h e th e r or n o t th e anim al organism is a true perpetuum m obile was indeed a relatively com m on th em e in th e G erm an literature. In a talk delivered before th e H ufeland M edical-Surgical Society in Berlin in 1836 on th e ex ten t to which vital processes can be explained in physical term s, physician August V etter exem plified some of th e changes taking place in the basic a ttitu d e of G erm an physiologists w ith respect to th e kinds of explanations one is en titled to dem and:

If we proceed to th e consideration of th e chem ical relations of organic beings, we find first of all th a t they develop if n o t all, th en nevertheless a portion of th eir charac­ teristic heat through a process of chem ism by w hich h eat is also liberated in the gasom eter, etc. If, alongside th e form ation of carbonic acid w ith th e help of th e in ­ spired oxygen, one ascribes the cause of anim al h ea t w ith some justice to an interac­ tion betw een the nerves and certain of th e body’s tissues (or general fluids), we never­ theless lack a physical explanation for th e la tte r phen o m en o n , unless we wish to look for one in a recently proposed hypothesis of liquefied nerve-m edulla. But we see nowhere in th e organism th a t there, where according to th e experiences of chem istry one expects a developm ent of h ea t from an existing process, such a one does n o t take place.107

Nor, when considering th e m otion of the blood and the heart, did Vetter shy away from im plying that such vital phenom en a m ight be explicable on purely m ech an ­ ical grounds: “W e are thus dealing here w ith a purely physical p h enom enon, and if we do n ot know the source o f the m otive force, it nevertheless does not appear more m ysterious than the fall of the water or the expansivity of the steam by which wheel and piston drive a p u m p .”108 U sing as an exam ple the once hotly contested issue of w hether an organism is capable of producing substances (such as certain com pounds of phosphorus and calcium ) containing elem ents not d e­ rived from its environm ent, Vetter reiterated his plea for the physical explanation of all vital processes by denying any powers of creation to the still-popular vital force: Now, w hether there lies in th e organic com position a force of chem ism capable of com posing o u t of their elem ents substances w hich we were n o t as yet able to decom ­ pose, can surely only be decided w ith certainty if it should nevertheless prove possible in at least a few cases to bring about this heretofore u n a tta in c d decom position by purely chem ical m eans. But little would be gained if we, anxious to refute th e n o tion of a living spontaneous generation, in tu rn w ished to propose an hypothesis of ele­ m entary spontaneous generation for th e sake of a few as yet unexplained facts, and to ascribe to th e vital force a property of w hich we otherw ise have no conception: that, namely, of m aking som ething out of n o th in g .109

T h e increasingly ‘obvious’ character of these kinds of explanatory dem ands was as im portant and fundam ental a change in physiologists’ thinking during the 1830s as were new techniques and experim ental findings.

2 .1 Physical and C hem ical Processes: The O rganism ’s C onnection w ith the External W orld Forem ost am ong Germ an physiologists o f the 1830s to em phasize the necessity of studying an organism in term s o f its interrelationship— in our terms both material and energetic— w ith th e physical world was unquestionably Friedrich T iedem an n .110 To be sure, T iedem ann did not ignore internal and apparently non-

m aterial causes o f organic activity— w itness his above-cited explanation of m otion in term s of the action o f th e will— but in the event he paid overw helm ingly m ore atten tion to processes of identifiable material change and exchange. As he wrote in the introduction to his influential H uman Physiology: T hrough th e investigation of the causes lying w ithin living bodies them selves on w hich depend their phenom ena and m anifestations of activity [Thatigkeits-Aeusserungen], or through th e discovery of their properties and forces and th e estab lish m en t o f the laws according to which they act, life is nevertheless n o t yet known. T h a t is to say, living bodies are n o t isolated creatures th a t have th e causes of th eir existence only w ithin them selves; rather they stand in reciprocal in teractio n w ith all of nature, they are co m p o n en t parts [Glieder] of all of nature. AU th eir m anifestations of activity and all their properties are also d ep e n d en t upon external influences. T h e co n tin u ed exis­ tence of organic bodies and of their m anifestations of life require a certain degree of h eat, th e influence of th e air, and th e presence of w ater an d food. . . . W e m u st th e re­ fore subject th e dependence of living bodies on external influences to closer investiga­ tion, search after th e causes of this dependence, and establish th e laws th a t prevail regarding th e contingency of living bodies on these external influences.111

T h e vivid im age of vital processes T iedem ann repeatedly portrayed was that of a com plex o f chem ical transform ations: “C onsidered from th e standpoint o f ch em ­ istry, living bodies appear to us as laboratories [ W erkstdtte] o f chem ical processes, for they undergo perpetual changes in their m aterial substrate. T hey draw m ateri­ als from th e outsid e world and com b ine th em with the m ass o f their liquid and solid parts.” 112 It w ould be difficult to overem phasize the exten t to w hich T ied em ann dwelt on the centrality of m aterial exchange. Significantly, he also explicitly con n ected these m aterial changes w ith the bod y’s exertion of force: “W ith the con tin u ed existence of anim als and with th e exercising of their m anifestations of force— w hich we call life— there is sim ultaneously connected a perpetual change in the m aterial substrate of their solid parts.” 115 T iedem ann discussed processes o f Stoffwechsel— a term he more consistently used in the second half o f the book— as they related to respiration, and he n oted their d ependence on such external factors as heat, air, water, food, and m echanical con tact.114 In this part of his work h e expressed m ore explicitly than elsewhere the close connection b etw een respi­ ratory Stoffwechsel and th e production of anim al heat: T h e physiologists of the m odern iatrochem ical school assum e th a t a kind of fer­ m entative or com bustive process takes place in living organs whereby th e co m b u ren t principle (the oxygen) from th e arterial blood conveyed to th e m com bines w ith th e organic com pounds of th e anim als and transposes th em in to a kind of com bustion. T h e co n stitu tio n of th e excreta appears indeed to indicate a process taking place in th e organs through w hich th e organic com pounds of th e higher or m ore com plex kind are transform ed in to lower or less com plex, even into inorganic com pounds. . . . T his course of events appears to consist in a distinctive [eigenthumlich] process similar to com bustion. And as one of its results m u st also be regarded th e p roduction of anim al h eat, w hich in anim als is precisely proportional to th e rapidity of th e exchange of

m atter. I t is n o t im possible, finally, th a t an agency created in th e nervous system has a great share in th is process.115

T ied em an n later gave extensive consideration to organism s’ d ep en d en ce on “external ag en cies,” or “stim u li,” by w hich he m eant circum stances such as tem ­ perature, atm ospheric pressure, clim ate, and geographical zone; such agencies act either m echanically or chem ically in so licitin g the organism ’s “m o tio n s” and “m anifestations of activity” (or “m an ifestation s o f force”) .116 T he latter are th e m ­ selves expressions o f th e organism ’s intrinsic “organic activity,” and are thus entirely unlike the sim ple com m u n ication of m o tio n characteristic o f inorganic bodies: T h e m anifestations of life and th e organic m otions th a t occur as a result of external influences are th u s essentially d istin ct from th e co m m u n ic ate d m otions of lifeless bodies in th a t they stand in no merely m echanical or chem ical relation to th e occa­ sioning causes, th e stim uli. W h e n we speak of organic m otions as occasioned by stim uli, we do n o t thereby assum e th a t they are th e im m ed iate effects of th e m e ch an ­ ical or chem ical im pression, b u t th a t they are always effects of th e forces of th e organ­ ism w hich were m erely called in to activity by th e external im pression. T h e m otions occasioned in living bodies by external objects are th u s n o t co m m u n ic ate d b u t rather absolute and au to n o m o u s m o tio n s for w hich tho se exterm al objects only provide th e occasion. T h a t th e excitations produced in organic bodies by external objects are pro ducts of organic activity [Wirksamkeit], or th e forces of th e organism s, is clear finally from th e fact th a t they do n o t occur in dead b o d ies.117

Crucially n ew with T ied em an n , however, was his explicit rejection of th e long tradition, exem plified above by Ferdinand G ottlob G m elin , of regarding irritabil­ ity as an otherw ise irreducible property of certain living tissues. H e consistently sough t to id entify a material basis— typically som e form o f m aterial exchange— for each o f th e organism ’s vital activities; o f irritability (Reizbarkeit) he wrote: W e m u st n o t, however, conceive of it as an in dep en d en tly existing force th a t only adheres to th e organism s an d is objectively d istin ct from th e su b strate of th eir organic m atter, one w hich were susceptible to a change— an increase or decrease— w ith o u t a t th e same tim e a change thereby taking place in th a t su b strate. W e m u st rath er regard it as a property grounded in th e distinctive c o n stitu tio n [Beschaffenheit] of th e or­ ganic m a tte r an d th e organization, and entirely d e p e n d e n t on th e m , a property th a t m anifests itself in th e species of living beings in ju st as m any d ifferen t ways as th eir organic co n stitu tio n is d iffe ren t.118

A lthough T ied em a n n did n ot explicity invoke considerations o f causality— in par­ ticular, th e requirem ent that th e physiologist identify a physicochem ical cause com m en surate w ith every expression of vital activity or force— th e tendency o f his work was clearly in th at direction. Johannes Muller, w hose universally acclaim ed Handbook o f Human Physiology began appearing in 1833, expressed views sim ilar to T ied em an n ’s, though not as forcefully or unam biguously, d esp ite the fact that the overall thrust o f his work

was toward th e physicochem ical investigation of vital processes. M uller did not, for exam ple, employ th e term Stoffwechsel in a consistent or program m atic fash­ ion, nor did he clearly assert th e underlying concept as a fundam ental principle of physiological explanation. Significantly, he posed at th e outset as the first ques­ tion physiology has to answer: “Are the bodies th at exhibit th e phenom ena of life different in their m aterial com position from th e inorganic bodies whose proper­ ties are investigated by physics and chemistry? And since th e phenom ena in b o th dom ains are so different, are the fundam ental forces th at produce th em also dif­ ferent, or are th e fundam ental forces of organic life only m odifications of the physical and chem ical forces?”119 W ith o u t anywhere giving a sim ple answer to this difficult question, M iiller nevertheless w ent on to stress th e differences betw een inorganic and organic com pounds and the role of the organism in protecting the latter from decom position. A nd as we will see in section 2.2 of this chapter, he was unwilling to give up a special “organic force” as the cause of typically vital pro­ cesses, even as he believed th a t the working o u t of the effects of th a t cause could be understood in strictly physicochem ical term s. Here, however, we are concerned with w hat M uller had to say about the rela­ tionship of th e organism 's vital processes to externally derived physical and chem ­ ical agencies. W ith in that context, one can find any num ber of striking passages that place him squarely am ong those who took their m odel o f physiological expla­ nation from th e experim ental physical sciences. For example, on th e role of exter­ nal stim uli he wrote: In m a in ta in in g life , th e extern al c o n d itio n s n ecessary for life — h e a t, w ater, a tm o ­ sp h eric air, an d food-—-con tin u ally b rin g a b ou t m aterial c h a n g e s in th e organic b o d ie s in su ch a w ay th a t th e y c o m b in e w ith th e organ ic b o d ie s, w h ile c o n s titu e n ts o f th e organic b o d ie s are in turn d e c o m p o s e d an d e x p e lle d . T h e s e in flu e n c e s h ave b e e n called s t i m u li or v it a l stim u li; th e y m u s t n e v e rth eless b e d istin g u ish e d from m an y o th er a c cid e n ta l stim u li th a t are n o t n ecessary for life , a n d th e a b id in g im a g e o n e sh o u ld h ave is th a t th e se vital stim u li p r o d u ce th e p h e n o m e n a o f life th rou gh m aterial c h a n g e s, th e ex ch a n g e o f p on d erab le an d im p o n d er a b le su b sta n c es, in th a t th ey stead ily m a in ta in th e m ix tu re o f h u m o rs (e.g., b lo o d ) n ecessary for lif e .120

In elaborating on the action of those stim uli on the body, M uller invoked power­ ful m echanical and chem ical analogies for the nature of the ensuing bodily pro­ cesses: T h e se stim u li are, as it w ere, th e extern al im p u lse for th e m o tio n [G an g] o f th e gearw orks of th e w h o le m a c h in e ; h o w ev er in ap p rop riate th e c o m p a riso n w ith a m e c h ­ a n ism m ay b e , th e organ ic force, w h ic h c re a tes in th e organ ic b o d ie s th e m e c h a n ism n ecessary for life , is n e v e rth eless c a p a b le o f n o a c tio n w ith o u t this extern al im p u lse and w ith o u t c o n tin u a l m aterial tra n sfo rm a tio n s w ith th e h e lp o f th e extern al so-called vital stim u li. R ic h e ra n d h a s th erefore n o t u n ju stly co m p a red th e m a n ife sta tio n s o f life to th e p h e n o m e n a o f c o m b u s tio n and th e flam e. T h e p h e n o m e n o n o f fire lasts only as lo n g as th e c o m b in a tio n s and sep aration s n ecessary for c o m b u s tio n take place; o x y g e n c o m b in e s w ith th e b u rn in g body, h e a t is d e v e lo p e d , an d as lo n g as o x y g en and

com bustible materials are supplied, the phenom ena of fire continue. Far be it from m e to make life dependent as on a com bustion; I would only say that here, as there, certain continual com binations and decom positions of matter produce there the phe­ nom ena of com bustion and the appearance of light, here the phenom ena of the or­ ganic force; that vital stim uli are for organic bodies what the oxygen of the atm o­ sphere and com bustible material are for the phenom enon of fire, where one does not after all call oxygen the stim ulus of the flame; and that, without at the same time considering the material changes thereby produced, w ithout the continual new for­ m ation and expulsion of ponderable and imponderable substances, the nam e stim u­ lus, or vital stim ulus, is an empty, indeed a false concept.121

In contrasting plants, w hich are com posed to a great ex ten t of sim ilar and inde­ p endently fu n ctio n in g parts, to anim als, w hich are com posed of very different and m u tually d ep e n d en t organs, h e similarly em phasized the m echanical n atu re of th e in terrelationship betw een the operations of brain, heart, and lungs an d their jo in t dep en d en ce on processes of respiratory Stoffw echsel: In animals, on the other hand, the reciprocal interaction between blood circulation, respiration, and nerves proves to be absolutely necessary for life. The nerves deter­ m ine the respiratory m otions, but the nerves do not act without blood that has re­ spired, and blood does not flow to all the parts and thus to the nerves without the contraction of the heart, which in turn is dependent upon the bright red blood and the action of the nerves. Brain, heart, and lungs are therefore, as it were, the principal interlocking gears in the animal m achine, which is set in m otion by means of the exchange of matter in respiration.122

D espite these strong words, his sub seq u en t discussion of th e causes of anim al m otion was devoid of m etabolic or energetic considerations.123 And considering th e force of M u ller’s imagery, th e reader of his text m ight b e surprised th at, as we have already seen, h e later rejected th e sufficiency of th e oxygen theory of anim al heat. H ere as with his rejection of th e supposed propulsive force of th e blood, M uller seem s to have preferred to base his conclusions on em pirical findings— typically co n tested th o u g h ostensibly decisive— rather th an to invoke a universal physical or chem ical principle. T h e o th er side of M u ller’s occasional diffidence— his reluctance to pursue a line of reasoning in to its farther reaches— was an openen ded avoidance of do g m atism .124 M uller’s preference for an em pirical or experi­ m en tal answer to physiological questions highlights a widespread conception of science th a t h ad to b e overcom e, during th e 1830s and early 1840s, before physiol­ ogists were com fortable appealing to general principles in order to decide issues on a m ore theoretical basis. Mayer, for one, show ed no hesitancy in favoring a science based on univeral principles. Burdach was an o th er who in terp reted vital functions (das leibliche Leben) in term s of “an u n in terru p te d exchange of m a tte r [’W echsel der M aterie].”125 He differed from T ied em an n and M uller, however, n o t only in explicitly discussing relations of cause and effect— whereby he distinguished organic from inorganic system s in term s of th e lack o f correspondence betw een th e kind and m agnitude of

th e organic e ffect an d its cau se— b u t also in regarding th e b o d y ’s ch a ra c teristic force of “ex c ita b ility ” as o p e ra tin g w ith o u t th e n e e d for any a cc o m p an y in g p h ysi­ cal changes. In th a t, he lik en ed th e b o d y ’s resp o nse to stim u li to th e m ec h an ic al e x c ita tio n o f th e “d y n am ical p h e n o m e n a ” of ele c tric ity a n d m a g n e tism in in a n i­ m a te b o d ie s, cla im in g th a t th e la tte r process is likew ise u n a c c o m p a n ie d by any su b sta n tia l physical c h an g es, as it likew ise e x h ib its a d issim ilarity in kind b e tw e e n cause a n d effect. E xcitab ility is th e m a n ife s ta tio n of a “force,” b u t th a t m e a n t for B u rdach th a t it is an in te rn a l (and by im p lic a tio n n o t fu rth e r analyzable) cause of m o tio n .126 W ritin g in th e sam e year as B urd ach , V alentin h e ld o u t th e p ro sp e c t th a t phys­ iological e x p la n a tio n s m ig h t b e c o m e w holly physical, w ith organism s b ein g re­ g arded as very finely c o n s tru c te d a n d p u rp o siv e m ach in es: Physics—occupied for not yet a half century with the investigation of a specific num ber of general agencies of nature and concerned to find out their laws, mutual relations, and similarities—on the one hand dom inates physiology because its norms, as fundam ental rules for everything external, also embrace every object of every natu­ ral science; on the other hand, in view of its laws and relationships it can also be applied to the phenomena of life in the m ost manifold fashion either through the analogy of m ethod or of fundam ental principles or through actual application of its established truths. . . . Only the greatest m isunderstanding of the essence of the or­ ganism could engender the insane idea that everything which occurs in living organic beings is foreign to the so-called physical laws of dead n a tu re .. . . W ithout ignoring the autonomy of life, the pure mechanics (sundered, to be sure, from the true vital processes) of the circulation of the blood, of the conduction of the nerves, of diges­ tion, of motion, etc., will show itself to be determ ined according to the same funda­ m ental principles that physics teaches for its domain of phenomena, and th at we apply practically in our machines and instruments. Only we shall find all of the ar­ rangements [Einrichtungen] and all of the material substances employed on their behalf to be m uch more purposive than we are capable of im itating or constructing by art.127 V alentin reasserted a n d e la b o ra te d su ch views th ro u g h o u t th e 1840s.128 T h e sim ilarity b e tw e e n organism s an d m a c h in e s w h ich h e— a s tu d e n t o f L iebig’s w rit­ ings— m o s t stressed was th a t b o th n e e d to b e su p p lied ex tern ally w ith som e fo rm of a lim e n ta tio n (Speisung) in o rd er to c o n tin u e to fu n ction: The expansion of a spring, the heaviness [Schwere] of a weight that maintains a clock­ work in motion, the flow of water that drives a mill, constitute physical alimentary m om ents [physikalische Speisungsmomente], while chemical alimentary m oments exist, for example, in the combustible material with which we heat a stove and in the burning hydrocarbon gas with which we illuminate; on the other hand, both physical and chemical m om ents are simultaneously present as nourishing agencies in steam engines. Organisms have the same need for alim entation, one which is here predomi­ nantly chemical and which for plants is supplied by the atmosphere and the assimila­ ble materials furnished by the earth and water, for animals and hum an beings by the

various foodstuffs and assim ilation products. To the extent that the m otion [Gang] of th e living clockwork— if I may so put it— is thus m ade possible by m eans of this assim ilation, there occurs with every m anifestation of force a consum ption of matter or agency proportional to it, just as this is the case with our m achines and artificial apparatus.129

To b e sure, th ere were also im p o rta n t differences: th e devices we b u ild are m ade of m aterials as stable an d u n ch an g eab le as possible, w hereas organic m a tte r is changeable an d sub ject to ready d eco m p o sitio n , an d m achines can n o t repair them selves or replace th e ir own p arts, as can living organism s.130 But if we knew how n a tu re solved these problem s of stability and tran sfo rm atio n , we w ould have “a c o m p lete insight in to th e overall m ech an ism [G etriebe] o f organism s.”131 D e ­ nying th e possibility of generatio aequivoca— th a t organic beings can now b e cre­ ated o u t of inorganic m a tte r— V alentin believed th a t th e p h en o m en a of life are an expression of th e w onderfully contrived organization of organic beings deriving from an infinitely wise plan, from an original an d co ntinuously active “im p u lse ” whose n a tu re an d w hose first ap p earan ce lie beyond th e reach of science.132 O r­ g anism s’ m arvelous ability to b u ild , repair, a n d reproduce them selves is th u s a result of th e ir o rganization, a n d does n o t require th e application of forces beyond th o se recognized by physics.133 Even organism s’ capacity for self-preservation and propag atio n we can im agine to b e solely th e co n sequence of th e ir org an izatio n .134 It is only w ith respect to th e m in d and th e nervous system th a t physicochem ical explanations, in c o n ju n c tio n w ith an an te c e d en tly assum ed order, are intrinsically in ad eq u ate: they im ply th e existence of an im m o rtal an d divinely created soul (or “spiritual p rin cip le”).135 In addressing th e q u e stio n of “th e fu n d a m e n ta l force of organism s,” T h eo d o r S chw ann coined th e word “m e ta b o lic ” in 1839 to refer to p h e n o m en a relating to th e chem ical tran sfo rm atio n s in a n d aro u n d cells.135 In a work designed to be p ro gram m atic of a th o ro u g h g o in g physicochem ical approach to th e investigation of vital p h e n o m e n a in b o th anim als and p lan ts, S chw ann m ad e only passing refer­ ence to problem s of respiration an d anim al h e a t, b u t w hen h e did it was as exam ­ ples of physicochem ical processes. E laborating an analogy betw een th e “m e ta ­ bolic force of cells” an d galvanism by p o in tin g o u t th a t th e chem ical changes produced by th e galvanic pile are acco m p an ied by corresponding changes in th e pile itself, Schw ann n o te d th a t th e co n d itio n s for th e occurrence of “m etabolic p h e n o m e n a ” inclu d e an ap p ro p riate te m p e ra tu re and th e presence of oxygen and carbonic acid, an d th a t o n e result of th e universal m etab o lic process is th e devel­ o p m e n t of h e a t.137 Schw ann co in ed a new te rm for an approach w hich was in th e process of achieving d o m in an ce am o n g his G erm an contem poraries. It was th e F ren ch m an Jean-B aptiste D u m a s’s lectu re of 1841, however, w hich perhaps m ore th a n any th in g else first forcefully p a in te d a p ictu re of p lants and anim als as exist­ ing w ith in a com plex w eb of m aterial a nd energetic exchanges: plants draw force from th e sun an d n u trie n ts from th e ir en v iro n m en t to create su b stances from w hich anim als can in tu rn derive h e a t an d force: “It is thus in absorbing w ith o u t cease a tru e force, th e lig h t a n d h e a t e m a n a tin g from th e sun, th a t plants func­ tio n , and th a t they pro d u ce th is im m en se q u a n tity of organized o r organic m atter,

food destin ed for th e consum ption of the anim al kingdom . . . . T h en com e the anim als, consum ers of m atter and producers of h eat and force, veritable com bus­ tion devices.”158 D u m as’s lecture signaled th e increasingly taken-for-granted char­ acter of a view of th e organic world in term s of processes of physical and chem ical transform ations taking place b o th w ithin each organism and am ong th e ensem ble of living things. Liebig, his contentious G erm an rival, m ade such a worldview even m ore a m a tte r of public debate during th e early 1840s. In his article on organic processes and the atm osphere, Liebig expounded a rich conception of chem ical processes as they pertain to the two essential and charac­ teristic functions of the anim al organism: th e production of h eat and m o tio n .159 H e invoked a general principle of causality— the relationship betw een a force and its effect— in order to link b o th of these phenom ena to underlying processes of m aterial exchange. His analogies were com bustion, th e production of m otion and h eat in steam engines, and th e production of galvanic electricity: Similarly, therefore, as in th e closed galvanic pile a certain so m eth in g , which we call a current of electric m atter, becom es perceptible to our senses th ro u g h certain changes th a t an inorganic body, a m etal, undergoes as a result of its co n tact w ith an acid, certain m anifestations of m otion and activity th a t we call life arise as a result of transform ations and changes in m aterial substances th a t earlier were parts of or­ ganisms. Lack of a correct view of force and effect an d of th e co nnection of th e phen o m en a of natu re has led chem ists to ascribe a portion of th e h e a t generated in th e animal organism to th e effects of th e nervous system. If one thereby excludes an exchange of m a tte r as th e condition for th e effects of th e nerves, th e n this m eans n o th in g else th an to have th e presence of a m otion, th e m anifestation of an activity, com e forth o u t of n othing. But no force, no activity can arise o u t of nothing. O ne has, finally, m ade th e observation th a t h ea t is g enerated by th e co ntraction of th e m uscles, similarly as in a piece of rubber th a t one has stretched rapidly and lets co ntract again. O ne has gone so far as to ascribe a portion of th e anim al h e a t to the m echanical m otions in th e body, as if th e m otions them selves could arise w ith o u t a certain expenditure of force th a t is consum ed by these m otions. T h ro u g h w hat, how ­ ever, one can here ask, is this force generated? H eat arises through burn in g carbon, through solution of a m etal in an acid, th ro u g h th e com bination of th e two electricities, through absorption of light. In th e sam e way h eat arises w hen we rub two pieces of a solid against each o th er w ith a certain rapidity. W e can produce a certain effect through a m u ltitu d e of causes th a t are extrem ely different in their m anifestations. In com bustion and in th e generation of electricity we have an exchange of m atter, or, as w ith light and frictional h eat, the transform ation of an existing m otion into a new one th a t acts u p o n our senses in a different fashion. W e have a substrate, som ething given, w hich assum es th e form of an other substrate, in every case a force and an effect. W e can produce all possible kinds of m otions from th e fire u nder a steam engine, and fire from a given q u an tity of m o tio n .140

Liebig w ent on to con n ect his views with the conception of heat as m otion, arguing th e im possibility of creating even an allegedly “w eightless” substance by m eans of m echanical action alone. His words imply the existence of a constant equivalence betw een heat and m otion, and he cam e close to advancing a general and all-inclusive conception of force, one that would embrace the customary im ­ ponderables, m echanical forces, and the m otion of ponderable matter. W ithout citing any evidence, he m aintained the constancy of the heat produced by the com bustion o f given am ounts of carbon and hydrogen under all circum stances, and forcefully reiterated his central con ten tion that all vital functions depend on chem ical processes of material exchange: O ne has only to recall th a t th e m ost distinguished physicists accept th e phenom ena of h eat solely as phenom ena of m otion just because the concept of th e generation of a m aterial substance, even a weightless one, is simply n ot reconcilable with its origina­ tion through m echanical causes, as through friction and m otion. Everything granted, w hatever part electrical and m agnetic disturbances m th e ani­ m al's body may play in th e functions of its organs, th e u ltim ate cause of all these activities is an exchange of m atter, expressible in term s of a transition, taking place in a certain tim e, of th e co n stituents of the food into com pounds of oxygen . . . . Now it is simply impossible th a t a given quan tity of carbon or hydrogen, whatever forms they may assum e in th e course of com bustion, is capable of producing more h ea t than it affords when it is burned directly in oxygen gas or m th e air. W h e n we make a fire u nder a steam engine and use th e force obtained to produce h ea t through friction, this h e a t can in no way ever be greater th an th e h eat we needed to heat th e boiler, and w hen we use th e current in a galvanic pile to produce h eat, this h ea t is in all circum stances not greater than w hat we can obtain through com bustion of th e zinc th a t dissolves in th e acid. T he contraction of muscles generates heat; th e force needed for this m anifests itself by m eans of th e organs of m otion, which receive it by m eans of an exchange of m atter. T h e ultim ate cause of th e h ea t generated can of course only be this exchange of matter. An electric current arises through the solution of a m etal in an acid; conducted th rough a wire it becom es a m agnet, by m eans of which we are capable of producing various effects. Tire cause of all the phenom ena so generated is m agnetism , th e cause of th e m agnetic effects we seek in th e electric current, and th e u ltim ate cause of the electric current we find in an exchange of m atter, in a chem ical action. T here are various causes for the generation of force: a tensed spring, an air current, a falling mass of water, fire burning u nder a boiler, a m etal th a t dissolves in an acid— one and th e same effect can be produced by m eans of all these various causes. B ut in th e anim al body we recognize only one cause as th e u ltim ate cause of all generation of force, and th a t is th e reciprocal interaction exerted on one another by th e constituents of the food and th e oxygen of the air. T he only known and u ltim ate cause of th e vital activity in th e anim al as well as in th e plant is a chem ical process.141

T h e problem with interpreting Liebig’s views is that this clearly advanced posi­ tion of physicochem ical reductionism was at odds with m uch else that he wrote

not only in other works, b ut elsewhere in the Animal Chemistry itself (whose first section incorporated the article under discussion essentially verbatim). As Holmes pointed out, Liebig’s claim here that chemical force is the ultim ate cause of all phenomena occurring in an animal was contradicted by his invocation of a vital force in a later section of the book.142 This contradiction was missed by Theodor Bischoff, then extraordinary professor of comparative and pathological anatomy at Heidelberg and one of Liebig's most faithful supporters, who read the work as asserting that a chemical process is the source of all organic motions. In approving the direction he believed Liebig was indicating for physiology— that of assimilat­ ing it methodologically to the other sciences— Bischoff gave Liebig’s inchoate ideas a more chemically reductionist and causally more respectable interpretation than the text warranted.143 Another reviewer who looked past the inconsistencies of Liebig’s book to second what he took to be its insistence that all vital activities m ust necessarily depend on underlying processes of material exchange was the physiological chemist, Franz Simon, whose judgm ent reflects the self-evident quality of the emerging consensus: “To regard the heat generated as the effect of the nervous system, whereby an exchange of m atter is thought to be wholly ex­ cluded, means to call forth an activity out of nothing. To regard the contraction of the muscles as a source of heat is equally inadmissible, for motion cannot occur without a certain expenditure of force, and the organs of motion obtain this force only through the exchange of m atter.” Chem ist Heinrich Rose’s review, however, made no m ention at all of energetic considerations, and O tto Kohlrausch’s booklength critique explicitly held open the possibility that certain organic activities might occur without any attendant chemical changes: “The action of gravity [Schwerkraft], the magnet, etc., as yet indicate no accompanying chemical pro­ cesses. Thus nothing stands in the way of the assumption that in the living organ­ ism, too, activities may exist that are neither caused nor accompanied by chemical action; that these activities m ight possibly produce heat is likewise not to be de­ nied when we see heat liberated by causes th at give no indication of accompany­ ing chemical action.— W hether or not these possibilities are true cannot of course be decided a priori.”144 The significance of Liebig’s causal analysis of the general conditions for the possibility of organic functions was not at all obvious to him. In light of this lack of universal appreciation for the energetic implications of Stoffwechsel, it is easy to see why Mayer m ight have been prom pted to publish an elaborated version of his theory of force in 1845 as Organic Motion in Its Connec­ tion with the Exchange o f Matter. The disputed issues could now be decided as a m atter of principle on the basis of his theory of force. 2.2 Vital Forces and the Soul: The Organism's Internal Sources o f Activity During the first four decades of the nineteenth century, German life scientists and organic chemists routinely discussed the role played by specifically vital forces—th at is, those not reducible to the physical and chemical forces of inor­ ganic nature—in the functioning of the animal organism. In addition, the physiol-

ogists am ong th em regularly addressed the problem of the relationship of the vital force to th e m ind or soul— understood as the source of voluntary m otions and the seat of consciousness— and the la tte r’s relationship to physical processes.145 Until the end of th e 1830s one encounters relatively little explicit criticism of vital forces. Q uite th e contrary, a vital force was typically invoked to explain processes like embryological developm ent, growth and regeneration, and the body’s ability to synthesize com plex organic com pounds and to resist destructive external forces. As already m entioned, anim al heat was not one of th e phenom ena com ­ m only accounted for in this way. In general, although it is no t q u ite true to say th at th e vital force was em ployed only to explain phenom ena of control and direc­ tion and n o t also those we would say involve doing work, this nevertheless seems to have been th e overall tendency, at least until Liebig’s work of th e early 1840s. O f course th e nervous system was widely held to be able to produce organic m o­ tions, b u t th e nervous system itself was typically placed under th e control of the m ind or soul, not th e m ore ‘vegetative’ Lebenskraft , 146 and physiologists only slowly becam e sensitive to all-em bracing energetic considerations. T h e context of debate over these issues was to change radically in the course of th e 1840s: on th e one hand, the growing consensus th at all vital processes should be explained in term s of m aterial exchange and the norm al laws of chem istry and physics cut all explanatory ground ou t from under bo th vital forces and th e m ind or soul; on th e other hand, physiologists cam e to regard them selves as no longer responsible for the subjective experience of will and consciousness or for th e pos­ sible role of m ind or soul in organic functions, nor were physiologists (in the m od­ ern sense of th e term ) the ones who were m ost responsible for dealing w ith those problem s, such as generation and developm ent, th a t seem ed m ost to require the assum ption of a creative goal-directed agency. In addition, from the late 1830s on there was increasing m ethodological criticism of th e vital force as a meaningless term th a t explains nothing b u t only covers one’s ignorance. As we shall see, L otze’s famous Lebenskraft article of 1843 was a landm ark in the evolution of this debate. Increasingly ou t of step w ith his contem poraries, Liebig becam e the m ost outspoken, if self-contradictory, advocate for an active vital force during the 1840s. Indeed, M ayer’s Organic M otion in Its Connection w ith the Exchange o f M atter of 1845 was in large part a response to Liebig’s treatm en t of th e vital force. H istorians’ assessm ent of the scientific status of th e vital force in G erm any during the 1830s and 1840s has, moreover, often been distorted by its being viewed from the perspective of the conservation of energy: th e subsequent conviction th at “force” is universally conserved triggered a general reaction against all special vital forces and obscured b o th their prior acceptability (to some) and the m otives for their criticism (by o th ers).147 Let us first look m ore closely at th e ways in which specific investigators dealt with these issues during the preceding decades. M ayer’s professor, Johann H einrich Ferdinand A utenrieth, devoted a special section of his highly regarded Handbook o f Empirical H um an Physiology to a dis­ cussion of th e “R elationship of th e Soul to the Life of the Body.”148 His principal aim was to distinguish the soul, “th e originally active force” in th e body, from the vital force, “th e force by m eans of which th e body or its parts, provoked by exter­ nal stim ulus, produces vital m otions.”149 H e based his distinction on several well-

known classes of phenom ena. For exam ple, som e parts rem oved from the body co n tin u e to react to stim uli, whereas th e soul is no t affected by th e loss of limbs; and cases of unconsciousness, where the person shows no signs of internal volun­ tary activity b u t where the norm al bodily functions continue to be perform ed, show th a t th e activity of th e soul is not necessary for the perform ance of lifesustaining vital functions. Similarly, after an organism ’s d ea th — th a t is, after the escape (Entweichen) of its soul— some of its parts often continue to m anifest vital activity— th a t is, th e presence of vital force.150 A u ten rieth likened the soul to an internal stim ulus, capable of provoking th e body into action b u t not th e source of th e resu ltan t activity, which he assigned rather to the vital force with which the living parts are endow ed. T h e soul is th u s th e source of voluntary m otions, while involuntary m otion was regarded as a “m erely m echanical arrangem ent set into action by th e vital force.”1’1T h e soul’s independence from th e body and from the body’s vital forces is dem onstrated by b o th th e irregularity of its actions and our internal sense of freedom of actio n .1’2 C onsidering the body’s various vital activi­ ties and th e principal chem ical transform ations th a t take place in their course, A utenrieth asked: “W h ich is th e first force th a t gives rise to these changes from th e rest state of th e anim al body?” T h e answer was n eith er heat nor any of the other im ponderable substances, nor any specific chem ical reactions, n o r food or drink, nor (of course) the in d ep en d en t soul. T he necessary condition for the body’s activity is th e presence of vital force, passed on from generation to genera­ tion since th e original creation of th e species and capable of self-m ultiplication.1’3 A utenrieth subscribed to essentially these sam e views for his entire adult life and gave th em am ple exposition in his Views on the VIorld o f N ature and the Life o f the Soul, published posthum ously in 1836.154 In th a t work, which C arus re­ ported h ad “attracted widespread a tte n tio n ,”15’ A utenrieth reem phasized th e in­ dependence of th e directive and voluntary soul from th e physical substance of the body, and now m ore explicitly interpreted vital force as th e interm ediary betw een th e two, the m eans by which the soul acts on the body and through which alone th e freely acting soul can m ake itself know n.156 A utenrieth insisted th a t th e soul is connected to th e m aterial world only via th e organic vital force; hence, even if (as may well be) spirits can exist independently of bodies, they could never make th eir presence felt immediately since they w ould lack any way of setting any part of th e m aterial world in m otion. T hus he rejected as lies or deception all reports of spiritualist p h en om ena (Geistererscheinungen) .157 To be sure, the many invol­ untary vital processes th a t sustain life do no t require th e participation of th e soul b u t are th e results of th e vital force acting in accordance w ith its proper and necessary laws. It is th u s th e vital force— now identified as irritability and associated w ith bo th in stin ct and th e form ative force (Bildungstrieb)— which is in one way or another responsible for producing organic m otions. A utenrieth did n o t ignore the organ­ ism ’s need to exchange m atter w ith the external world— n u trien ts com ing in and excreta going o u t— in order to keep functioning, b u t he did deny th a t this ex­ change is th e source of th e vital force expended in perfom ing vital functions. Indeed, th e vital force of an organ, once exhausted, is capable of regenerating itself w ith o u t external assistance merely through rest.158 As will be discussed in

section 3.1 of this chapter, A utenrieth conceived of a “calling fo rth ” (Hervorrufen) of th e vital force from an invisible realm beyond th e physical world. In support of his contention th a t th e action of th e vital force is n o t due to any anteced en t chem ical changes, A utenrieth cited experim ental results published by Berlin physicist Paul E rm an in 1812. According to A utenrieth, E rm an’s experi­ m ents show th a t even very rapid m otions can take place in an organ w ithout any corresponding change in its ponderable m atter. From this A utenrieth concluded th a t even in cases where such a change does take place, it is no t the m aterial change itself w hich generates the m otion. Rather, “th at which generates the m o­ tion sim ultaneously also occasions the increase or decrease in th e ponderable m a t­ ter in th e individual organ of th e body,” and hence “we m ust therefore ascribe the vital m otions in the first instance to a purely autonom ous b u t involuntary force, which nevertheless is no longer a m ere a ttrib u te of ponderable anim al m atter or a consequence of its m echanism , and w hich we therefore in general can call or­ ganic vital force, as opposed to our free volitive force.”159 In fact, A utenrieth seri­ ously m isunderstood E rm an’s results as having failed to detect any chemical changes in electrically stim ulated m uscles, w hen in fact E rm an attem p ted no such determ ination b u t rather observed only the tem porary decrease in the contracting m uscle’s volume. Q uestions concerning th e source from which new vital force comes into the world also arose in connection w ith generation. A utenrieth denied th a t a child’s vital force com es to it at the expense of its parents’— a supposition easily refuted by (am ong o ther things) cases of num erous offspring— and concluded: “But if the child’s share of th e vital force com m on to all living things is really a new one, one which entered into th e world of corporeal phenom ena only at th e child’s form a­ tion, th en we m u st also conclude th a t every increase in the vital force during the life of th e individual com es to it in general from the same invisible source.”160 As further evidence “for a continuous stream of creation from beyond th e visible world,” he cited plants growing where no seeds had been present, Joseph Priest­ ley’s fam ous “green m a tte r” (the alga, Conferva fontinalis), spontaneous genera­ tion, and th e equal num ber of births of girls and boys.161 Likewise dem onstrating the ind ep en d en t presence everywhere of th e same “universal dynam ical source of organic life” was th e existence of series of closely corresponding anim al types in different clim ates and distant regions of th e globe.162 A lthough th e vital force possesses internal activity, it nevertheless acts “accord­ ing to laws of necessity, albeit those proper to itself,” i.e., not th e laws of dead m atter.165 And although vital force can express itself only in th e presence of p o n ­ derable m atter, A utenrieth was at pains to deny the idea “th a t life is merely a property of a body which constructs itself in a determ inate m anner.”164 As evi­ dence of th e independence of life from its m aterial substrate, h e cited th e reap­ pearance in th e geological record of beings sim ilar to those wiped ou t by an inter­ vening catastrophe and the revivification bo th of frozen fish and frogs and of d ried-out rotifers like Lam arck’s Furcularia redzvivu.165 In addition to th e law bound vital force, however, hu m an beings possess an im m aterial geistig principle w hich is, like the vital force, the product of no merely m echanical arrangem ent of m aterial parts, b u t which, unlike the vital force, is

b o u n d by no necessity. T h a t p rin cip le, w h ich m a n ife sts itself in our freed o m of will, m u s t necessarily b e in d e p e n d e n t o f b o th th e b o d y an d th e vital force: “For if fre e d o m w ere to arise o u t of co rp o real necessity, th e n it w ould arise o u t of so m e th in g , a b so lu te n o n fre e d o m , w h ich w ith regard to freed o m w ould th u s b e a tru e n o th in g . B u t o rig in a tio n [E nfstefiung] o u t of n o th in g presupposes a creative force th a t preced es ev ery th in g d e te rm in a n t, so m e th in g th a t th u s c o n tra d ic ts th e c o n c e p t o f n ecessity.”166 O n c e again th e q u e s tio n arises o f w here th is p rin cip le— th e soul o r ego— co m es fro m at th e g e n e ra tio n o f a n ew bein g . It is n o t th e p ro d ­ u c t of th e body, an d n e ith e r p a re n t is co n scio u s o f a division or d im in u tio n of its ego. A u te n rie th c o n c lu d e d th a t it m u s t have ex isted befo re it was “in v e sted w ith a body.”167 I t co m es in to th is w orld from th e sa m e p reterphysical realm w hence co m e th e vital force a n d th e im p o n d e ra b le s. A lth o u g h his c o n sid e ra tio n of th e soul a n d its re la tio n sh ip to th e vital force w ith in a physiological c o n te x t was c o m ­ m o n in h is day, A u te n rie th ’s ideas c o n c e rn in g th e c o m p le te self-sufficiency of th e vital force a n d th e causal in d e p e n d e n c e of organic m o tio n s fro m any u n d erly in g p h y sico ch em ical tra n sfo rm a tio n s w ere a strik in g anom aly by th e m id-1830s. In ­ d eed , C a ru s n o t u n ju stly c h a ra c te riz e d A u te n rie th ’s views as b elo n g in g to th e philo so p h y o f th e e ig h te e n th cen tu ry .168 W e have already e n c o u n te re d F rie d ric h T ie d e m a n n as o n e o f th e stro n g e st ad v o cates of a physiology b a se d o n th e c e n tra lity of processes of in te rn a l and ex tern al m a te ria l ex ch an g e for th e u n d e rs ta n d in g of organic processes. H e was n o t, how ever, a p h y sico ch em ical re d u c tio n ist, a n d h e believ ed th a t, by iden tify in g a n d c irc u m sc rib in g th e p urely c h em ical a n d physical processes ta k in g place in an o rganism , o n e co u ld id en tify o th e r processes p ecu liar to living th in g s. As h e re a­ soned in th e in tro d u c tio n to h is H u m a n Physiology of 1830: The im portant question, whether the phenom ena observable in living bodies are grounded in forces of a distinctive nature, in organic forces, or whether they are not rather to be regarded merely as effects of forces that belong to all bodies, even the lifeless, we can only answer on the basis of a future comparison between the phenom ­ ena and properties of living bodies and those of inorganic bodies. But since we hereby encounter manifestations of activity which are distinctive of living bodies and which we cannot regard as effects of general physical forces, this then justifies us in the assumption of vital forces [vitale Krdfte] or vital properties of their own. . . . For all essentially different phenom ena we m ust assume particular causes and forces as long as we are unable to elim inate the distinction between the phenom ena and reduce them to one another. T he endeavor of physiologists m ust ultimately be aimed princi­ pally at discovering the conditions and laws according to which the forces manifest their activity and at investigating the relationship of the forces to each other, or their reciprocal interaction, and their m utual dependency.169 W h a t th e essen ce of force or m a tte r m ig h t b e is b ey o n d th e scope o f n a tu ra l science to discover— as is th e n a tu re of th e close relatio n sh ip of th e soul to th e body.170 In th e e v e n t, T ie d e m a n n id e n tifie d th e n e e d for su ch special organic forces in th e th re e p rin cip al tra d itio n a l areas. O n e was w ith resp ect to th e greater c o m p le x ­ ity o f o rg an ic ch em ical c o m p o u n d s as c o m p a re d w ith inorganic:

T here m u st accordingly b e active in living b od ies yet another force w ith its own nature besides the chem ical affinities that determ in e the configuration of lifeless bodies, one by m eans of w hich is produced the specific diversity of organic forms having identical com position. Or, to express the sam e th in g m ore precisely in other words, th e config­ uration of organic b od ies is n ot th e effect merely of elective chem ical attraction, as in lifeless bodies; it is the effect of a force w ith its ow n— or, if you will, higher— nature, w hich produces th e con figu ration.171

A second area related to th e organism ’s power of resisting destructive external influences. For T iedem ann, putrefaction and ferm entation are m ade possible by th e removal of th e m etam orphosing substances from the protective influence of a vital force. But unlike Liebig, who later saw them as purely chem ical processes, T iedem ann placed th em in a category of interm ediate complexity, th a t of organisch-chemische Processe: “T h e chem ical processes occurring after the extinguish­ ing of th e forces distinctive of living bodies— forces which during their existence opposed th e chem ical affinities of external objects working toward th eir destruc­ tion, [i.e.] putrefaction and ferm entation, processes by m eans of which th eir com ­ position and form are changed— are processes of their own kind [Vorgange eigener A rt} such as do n o t occur w ith the decom position of inorganic bodies. T hey are organic-chem ical processes.”172 A third area em erged in the course of his consider­ ation of processes of generation, developm ent, and growth. N ot surprisingly, he found in th em th e need to assum e th e operation of a special goal-directed Bildungskraft: T h e principal result of the investigations undertaken is that, to judge from its ef­ fects, th e form ative force inherent in all living b od ies— a force w hich acts in an inter­ nal purposeful fashion, w hich propagates itself from generation to generation, and w hich m anifests itself in the generated beings under certain external con d ition s and circum stances— m u st be regarded as an au ton om ou s force different from all other know n forces. A s far as experience in d icates, it m anifests itself only in organic su b ­ stances, and in bodies com p osed o f th em , w hich are different from inorganic bodies in their com p osition , configuration, and construction as well as in their properties. T h is force thus appears to be a force inherent in organic substances and grounded in their distinctive m aterial con stitu tio n , w ith ou t our b ein g able to pronounce further over its ultim ate ground and the m anner of its action, as is also the case w ith other forces. 173

Nevertheless, despite T ied em an n ’s acceptance of special organic forces, he was careful n o t to invoke a (single) vital force, a Lebenskraft, as the cause of those peculiar organic processes. A lthough he did no t discuss th e issues explicity in these term s, in fact his vital forces were responsible for the direction of only a few typical and traditionally so-distinguished organic processes, while he consistently looked to explain th e working o u t of those processes and the general course of all th e o th er organic processes associated w ith th e m aintenance of life in term s of the exchange of m atter. His a ttitu d e toward th e com m only assum ed vital force came ou t in his consideration “of the causes and forces th a t produce th e m otions of living b odies”:

T h e m otions of living bodies can be regarded as n eith er th e effects of gravitation nor as produced by an externally co m m unicated m echanical im pulse. Just as little have they been explained up to now in a satisfactory m an n er in term s of th e attractio n and repulsion m anifesting them selves in th e interplay of chem ical affinities. D istin ­ g uished scientists and physicians therefore regard th e m as autonom ous m otions pro­ d u ced by forces of a special kind grounded in their distinctive co n stitu tio n . But if we ask, w hat are th ese forces, under w hat conditions an d according to w hat laws do they act, we th e n en c o u n te r a subject over w hich th e m ost diverse opinions an d theories have been advanced, and th e m ost violent controversies carried o u t.174

In his lo n g h isto rical sk etch of th e controversy, T ie d e m a n n c riticized S ta h l’s a t­ te m p t to id en tify th e soul as th e sou rce a n d cause of organic m o tio n s. T ie d em a n n ’s u n d e rs ta n d in g of th e physiological fu n c tio n of th e sensing a n d im agining soul, w hose reality he n ev er q u e s tio n e d , was sim ilar to A u te n rie th ’s: A gainst this theory [of S tahl’s], w hich w ould have th e anim al body as such, its organization, and its m aterial substrate to be entirely inactive and w ith o u t force, one can raise serious objections. Stahl erroneously takes th e soul, as one of th e causes th a t occasion m otions, to be identical w ith th e forces th a t produce m otions. A lthough it can n o t be denied th a t anim als decide autonom ously u p o n certain m otions by m eans of th e sensitive and im aginative principle, it nevertheless does n o t follow from this th a t th e soul also brings those m otions to com pletion, and th a t th e im pulse to all m otions is given by th e soul. W e may only regard th e la tte r as a cause by m eans of w hich m otive forces are set in to action w ithout, however, taking it to be th e very force executing th e m otions. T h a t th e tw o are essentially different follows from th e fact th a t th e m uscles, th e heart, and all parts provided w ith m uscles, [such as] th e sto m ­ ach and intestines, w hen rem oved from th e body still co n tin u e th e ir m otions for a period of tim e if they are stim ulated. If th e m otive force were here one w ith th e soul, th e n one would have to assum e a divisibility of th e la tte r w ith th e separation of th e body, w hich contradicts th e fundam ental conception of th e unity an d indivisibility of th e soul.175

T h u s T ie d e m a n n ex plicity re je c te d th e c o n c e p tio n of th e soul or vital force as a m o tiv e force cap ab le by itse lf o f p ro d u c in g organic m o tio n s w hile g ra n tin g it th e ability to direct th e expression of th e m o tiv e force possessed (presum ably in ch em ical form ) by th e m uscles. T ie d e m a n n fu rth e r criticized o th e rs ’ reliance on a vital force to explain organic m o tio n s: O n th e basis of th e ir investigations of the properties of plants and anim als an d th e com parison of th e m w ith th e properties of lifeless bodies, several scientists gained th e conviction th a t the m otions and all the o th e r m anifestations of force of organic bodies are d ifferent in their causes and m ode of action from th o se of inorganic bodies. T hey regarded as inadm issible every a tte m p t to w ant to explain th em in term s of th e gen­ eral physical forces. N or were they satisfied by th e forces proposed by th e abovenam ed physiologists, by the soul, G lisson’s irritability, or H aller’s irritability and nerve-force. T hey therefore believed they had to resort to th e assu m p tio n of one fu ndam ental force productive of all th e m anifestations of life, a force th a t m anifested its activity in b o th plants and anim als, w hich they called vital force or vital principle.

T h is on e fundam ental force inherent in organic bodies was supposed to produce all the phenom ena of life by m anifesting its activity in various ways and in various directions. Z ealous defenders of such a vital principle were Barthez, Fryer, B lum enbach, H ufeland, Springel, Brandis, R osse, and others. By p ositin g the vital force they believed th ey had satisfied th e requirem ent of reason to bring unity into the m u ltip licity of the vital phenom ena. Looked at closely, this sim ple fundam ental force is only an occu lt quality of w hose existen ce and m od e of action — as well as o f the reason why it m an i­ fests itself now as a form ative, now a m otive, now a sensible principle— th ose physiol­ ogists have given no acco u n t. 175

T h u s it was n o t th e assum ption of special organic forces per se th a t T iedem ann objected to, b u t th e hypostasizing of a single in dependent energetic agency, the vital force, as a causal explanation of complex organic processes. Such pseudocausal explanations have no place in science. A lthough less critical and elaborated than T iedem ann’s, Volkm ann’s handling of vital forces em phasized in an analogous fashion the need to assum e som e kind of internal self-active directive agency in order to be able to account no t only for th e body’s power of resisting decay, b u t also for the gross lack of proportion b e­ tween external physical stim uli and the body’s com plex responses.177 In practice, however, a vital force as such did n o t feature prom inently in his work. Volkmann also granted th e existence of a self-conscious, sensitive, and volitive soul w ithout m aking it th e agency of appreciable physiological processes.178 T h a t raised the question, however, of where th e souls of newly engendered individuals come from. His answer— th a t they derive from the parents’ souls— is of less interest th an th e term s in which h e considered the m atter: Either the divinity itself creates th e soul through im m ed iate intervention— a way of looking at things foreign to natural scien ce— or th e parents create it. If th e latter is the case, then it w ould b e against all analogies to think o f a creation out o f nothing, because as far as w e can see, creation appears as a m etam orphosis, as a transform ation of som eth in g already present into so m eth in g new. T h at th e soul of the fetus arises originally as the result of an effu sion o f the parental soul into the germ is clearly attested by the psychic correspondence b etw een parents and children.179

T hus th e question of th e origin of th e soul, in a physiological context, led to the denial of creation ex nihilo— even if, to be sure, Volkmann ignored the q u an tita­ tive problem raised by th e im plied Vertheilung of th e soul. Two works of physiology in M ayer’s library shared T iedem ann’s judgm ent that, even if th e p henom ena of organic life seem to justify the assum ption of special organic forces, we m ust nonetheless no t think th a t by bestowing a nam e on a class of phenom ena we have thereby explained them . Accordingly, Karl A sm und Rudolphi, professor of anatom y and physiology at th e University of Berlin since its founding in 1810, approved guardedly of th e assum ption of a vital force as the convenient designation for the unknow n cause of life, b u t rejected it in no uncer­ tain term s as a putative explanation or as som ething (ein Etwas) superadded to

th e organism and th u s an im atin g it; as he added, “To assum e several vital forces instead of one does n o t im prove th e m atter.”180 Ferdinand G ottlob G m elin, pro­ fessor of m edicine and natural history at T ubing en, expressed a cognate if som e­ w hat m ore a n tiq u ated opinion, recalling an older faculties-based physiology, in th e same year ( 1821): “Since we do no t yet know th e im m ediate cause [G rund] of these different kinds of excitation . . . we therefore a ttrib u te forces to th em , with which we by no m eans aim at an explanation, b u t merely wish to have an expres­ sion for som ething unknow n, and [we thus] call th em sensibility, irritability (vital turgor), form ative force, or vegetative force.” In a footnote to this passage G m elin added th a t “we recognize th a t they all m ay be com prehended by one ultim ate principle, which we call vital force.” 181 Sim ilar views were advanced nearly tw enty years later by the reform -m inded T u bingen Privatdozent, A lbert Friedrich Schill, who associated th e vital force con­ ceptually w ith o th er basic forces of nature: W e n otice everywhere in nature tw o in tim ately co n n ected things, m atter and activ­ ity; there is no activity w ith ou t m atter, nor m atter w ith ou t activity. . . . W e d o n ot know th e internal cause [Grund] o f activity, [just as] th e principle o f life is unknow n to us. W e call this X 'vital force’ and th u s understand thereby the un­ know n internal basis o f vital activity. Physiology does this w ith th e sam e right by w hich physics has called th e unknow n reason [Grund] why b od ies are heavy ‘gravity’ [Schwerkraft] and chem istry has called th e unknow n cause of chem ical com b in a tio n s ‘ch em ical force’ or ‘affinity.’ T h e vital force is co n n ected w ith every part o f organized m atter; in n on e d oes it have its exclusive seat. T h e nervous force, sensibility, is only a part; it is n ot identical to the vital force, for an acephalus is otherw ise o ften well d eveloped. T h e vital force can n ot exist w ith ou t organized m atter, in the in tim ate linking o f the tw o lies th e basis of life. E ach kind of activity of th e vital force dem an d s in turn a different organization, th en ce th e diversity in th e con stru ction o f th e organs. B oth always correspond to each other. Sam e activity, sam e organ ization.182

If, on th e one hand, SchilTs equation betw een activity and structure seems to evince th e kind of reductionist tendencies th a t were soon to be p rom inent in G erm an physiology, on the o th er h an d his defense of th e vital force in term s of its analogy w ith gravity and chem ical affinity looked back to a m ode of thinking th at Frangois M agendie h ad roundly criticized earlier in th e decade. M agendie h ad set him self a difficult task in his frequently reprinted and widely tran slated Elementary Sketch o f Physiology: namely, to press as far as possible the application of physics and chem istry to the explanation of physiological processes while at th e sam e tim e recognizing th e existence of at least som e distinctly vital phenom ena. As he wrote in the preface, “T h e belief, so harm ful and so absurd, th a t physical laws have no influence on living bodies does n o t have th e sam e force any m ore; perceptive m inds are just beginning to see th a t there could b e different classes of ph en o m ena in th e living anim al, and th a t simply physical acts do not exclude purely vital actions.”183 N evertheless, M agendie utterly rejected th e tim eh onored practice of covering o n e’s ignorance w ith an em pty phrase:

Since th e earliest tim es one has seen th a t a large proportion of th e phenom ena particular to living bodies do n o t follow th e sam e course, are not subject to th e same laws, as th e phenom ena proper to inorganic bodies. O ne has assigned a particular cause to th e phenom ena of living bodies. T his cause has received different designations. H ippocrates called it φ ύσις (nature), A ristotle, motive and generative principle; Kaw Boerhaave, im petum faciens; van H elm ont, archea; Stahl, soul; others, vis insita, vis vitae, vital principle, vital force, etc. W h a t do all these expressions m ean? O ne can take two very different courses of action w ith regard to them : to reify them , to m ake of th em beings to w hich belongs th e power of producing th e vital phenom ena, is th e first; b u t in following this one, would we n o t resem ble those savages who, after having coarsely sculpted a rock, make a god out of it? T he second course of action consists in recognizing th a t these words designate th e unknow n cause or causes— perhaps forever incom prehensible— of the actions of life; in th a t case one m ust agree th a t science hardly profited when they were invented. O f all th e illusions into w hich som e m odern physiologists have fallen, one of the m ost deplorable is to have believed, by coining a word vital principle or vital force, to have done som ething analogous to th e discovery of universal gravity [pesanteur]. Just as attraction presides over th e changes of state of inert bodies, so (they say) does the vital force direct th e m odifications of organized bodies; b u t they fall in to a grave error, because th e vital force cannot be com pared w ith attraction; th e laws of th e latter are known, those of th e vital force are unknow n. At th e present tim e physiology is at precisely th e point where the physical sciences were before New ton: it awaits an intellect of th e first order to com e and discover th e laws of th e vital force in th e same way N ew ton m ade know n th e laws of attra c tio n .184

Perhaps Mayer fancied him self to be that N ew ton of physiology, som eone w hose ideas were founded on valid analogies. Yet despite M agendie’s apparent dism issal of the concept of vital force, he im m ediately introduced a vital action (action vitale) to which, alongside nutri­ tion, he claim ed it is possible to reduce all organic phenom ena. T h e vital action is responsible for th e production of bile and urine in the liver and kidneys and for the contraction of m uscles; it was conceived of as a kind of hidden m otion of (presumably) the material parts of the affected organ. Except that M agendie im ­ plicitly advanced a m aterialistic ontology, his vital action performed about the sam e functions his Germ an colleagues assigned to the Lebenskraft. In fact, how ­ ever, such term inological skirmishing was of little im portance to the physiological work M agendie proposed to do: AU the phenom ena of life can therefore in th e last analysis be connected with n u tritio n and the vital action; b u t th e hidden m otions th a t co n stitu te these two p h e­ nom ena do n o t fall u n d er our senses, and it is not to th em th a t our atten tio n should be directed; we should lim it ourselves to studying th e ir results— i.e., the physical properties of th e organs, the sensible effects of the vital actions— and to investigating how they bo th contribute to th e general life. T h at, in effect, is th e object of physiology.185

By th e late 1830s, M agendie was speaking o u t m ore unam biguously and more confidently for a nonvitalist physiology. In his Lectures on the Blood, delivered from D ecem ber 1837 to April 1838, he told his students the first day th a t “am ong these prejudices [which hinder th e progress of science] there is one in particular against which I have protested since I have been engaged in teaching”— namely, “to believe th a t there is noth in g in com m on betw een w hat takes place in living bodies and w hat happens in inert m atter.”586 In his second lecture he pointed out th a t “it is of th e greatest im portance to properly d eterm in e th e nature of the p henom ena we wish to study,” and asserted th a t, w ith regard to physiology, “our experim ents have dem onstrated th a t such and such actions th a t one attrib u ted to th e life force [faisait dependre de la vitalite] were purely physical. T hese clearly d em on strated facts have scandalized m any an avowed partisan of th e marvelous and have provoked m any an outcry; b u t one is beginning to get used to th e m .”187 G iven M agendie’s stature and th e wide availability of his works, it is q u ite likely th a t M ayer en co u n tered his views urging at first the desirability, later the suffi­ ciency of applying physicochem ical principles to th e explanation of th e ph en o m ­ ena of organic life. T hose views m ight have been reinforced by M ayer’s professor of physiology and pathology, Carl Ludwig Elsasser, who published an annotated translation of M agendie’s Sketch in T iibingen in 1834 and 1836. Unlike A utenrieth, Elsasser would have nothing to do with som e kind of unitary im m aterial agency diffused th ro u g h o u t the body and responsible for its vital phenom ena. He seconded M agendie’s program m atic call for th e farthest possible extension of ex­ planations based on th e general forces of nature, conceding only to th e m ind the necessity of special im m aterial forces. In his remarks to the above-quoted passage from M agendie on th e “C auses of th e Vital P henom ena,” Elsasser wrote: T h e expression v ita l force may only b e used as a nam e by w hich o n e designates the totality o f th e still unknow n causes of th e vital p h en om en a. In this sense the word is harm less, but of course is also neith er here nor there [gleichgiilhg]. But if one presup­ poses w ith its use that it is only one force that produces the various vital p h en om en a, th en it is objectionab le, b ecau se o n e thereby proceeds from a highly im probable hy­ p oth esis, nam ely from the assu m p tion o f a particular, sim ple en tity [W esen], foreign to m atter, w hich is distributed throughout th e entire body and w hich brings about the various vital p h enom en a by acting on the intrinsically dead matter. T h e assum ption of a single vital force and of a vital principle foreign to m atter is accordingly unproven, unnecessary, and even harm ful, in that it declares as idle from th e start all endeavors to search for th e effects [or actions (W irkungen) ] of th e general forces of nature in the sphere o f life as well. . . . W e have to ascribe only th e psychic activities to forces th at do n ot b elo n g to m atter, although their ex isten ce and ex ten ­ sion is restricted to a certain size and co n stitu tio n o f th e brain. 188

As I will later argue, such ontological reflections on th e nature and relationship of m ind, force, an d m atter, whereby forces were typically understood to be prop­ erties of m atter, probably played a central role in M ayer’s earliest reflections about physiologically produced h eat and work. Unlike nearly everyone else’s, M ayer’s

forces— n o t im ponderables, b u t forces— were entities sui generis ind ep en d en t of ponderable m atter. Having thus sam pled G erm an physiologists’ views on the role and status of the vital force during the 1830s, we still have to exam ine the writings of Johannes Muller, th e m ost prom inent and influential am ong them . T he several parts and editions of his two-volum e Handbook o f H um an Physiology appeared betw een 1833 and 1844, spanning the crucial years of this continuing debate. Yet they provide a poor indication of th e character of th at debate, and M uller’s own views are n o t always easy to extract from his often allusive and inconclusive expositions. In part, I think, this situation reflects the fact th a t M uller’s quasi-Platonic m ode of th o u g h t was com ing into increasing disfavor, and he chose no t to m o u n t too aggressive a counterattack. T h en , too, M uller was sensitive to the kinds of ques­ tions th a t belonged to natural science, and he wished to address him self to em pir­ ically grounded natural scientists. So little did he forcefully engage the issues th at th e first through fourth editions of the im portant first part of his text were essen­ tially unchanged in all relevant particulars. Even his term inology suggests both his diffidence and his reserve vis-a-vis contem porary thinking. He only rarely used the com m on term “vital force,” preferring for the m ost part to speak of the “organic” or “organizing” force, b u t also using as apparent synonyms a plethora of alterna­ tive words: activity, rational creative force, soul, primum movens, unconsciously working purposive activity, vis essentialis, idea, m otive idea, and (a late favorite) vital principle.189 M uller first engaged th e subject in connection w ith his denial of spontaneous generation (generatio aequivoca): organic m atter never arises by itself, and only plants possess th e capability of transform ing inorganic m atter into organic. His appended com m ents contained th e germ of m uch th a t he would later expand on: Now, how organic beings have com e into ex isten ce in the first place— in w hat way a force absolutely necessary for the form ation and preservation o f organic m atter, b u t w hich, on the other hand, also m anifests itself only in organic substances [Materien], has com e to m atter [zur M aterie gekommen ist]— lies ou tsid e all experience and know ledge. Nor can the knot be cut by m aintaining that the organic force resides in m atter from eternity, as if organic force and organic m atter were only different ways of regarding th e sam e object; for organic ph en om en a are in fact proper to only a certain com bin ation of elem en ts, and even organic m atter capable of life breaks dow n into inorganic com p ou n d s as soon as th e cause o f the organic ph en om en a, the vital force, ceases. In any even t, th e solu tion to that problem w ould not at all b e the task of em pirical physiology b u t o f philosophy. S ince conviction in philosophy and in the natural sciences has a w holly different basis, w e are constrained here first of all n ot to leave the field of reflective experience [eine denkende Erfahrung] . W e m u st therefore con ten t ourselves w ith know ing that the forces that make organic b od ies alive are distinctive, and then w ith investigating their properties more closely.190

W e th u s en counter the organic force as responsible for th e form ation and preser­ vation of organisms and organic m atter— typical attributes, to be sure.191 In the event, however, when it cam e to the understand ing of any particular vital func-

tion, M uller never co n ten ted him self with invoking th e powers of this organic force, b u t rather sought either a phenom enological description or physicochem i­ cal explanation of it, reflecting his conviction th a t the satisfactory elucidation of a concept like vital force lies outside natural science. W e glimpse, too, M uller’s conception of th e vital force as an entity in d ep en ­ d e n t of m atter, som ehow joined to it to produce living organisms. He and A utenrieth, w hom he frequently cited in a variety of contexts, were am ong the few to assert th e possible independence of force from m atter. For M uller the term “force” som etim es included th e im ponderables, and he exploited at least one im p o rtan t analogy betw een vital and physical forces, though at other tim es h e was concerned to stress their differences, no t their sim ilarities.192 T he increasingly popular no tio n th at the erstw hile vital force was noth in g m ore than the expres­ sion of a particular arrangem ent of the sm allest parts of m a tte r was alien to M uller’s worldview. As we shall see, th e upshot of his reflections on th e relation­ ship betw een life and nonlife was no t to take th e laws of inorganic n ature as ad eq u ate to explain vital phenom ena, b u t rather to infuse all of nature with a kind of laten t or p otential life. Im m ediately after the passage just quoted, M uller began a new section entitled “O n th e Organism and on Life,” which revealed the K antian origins of som e of his conceptions of life. Organic bodies are distinguished from inorganic n o t only by the m an n er of th eir com position ou t of the elem ents, b u t also by the purposeful­ ness of their activity in accordance w ith the laws of a rational plan.193 For M uller th e purposive behavior of the “organizing force” is w hat keeps it from being re­ ducible to th e m ere arrangem ent of m aterial parts, though some of his imagery, rem oved from its context, makes him look like an unalloyed m echanist: S om e have believed that life or th e activity of organic b od ies is only th e result of the harmony, of (as it were) the interlocking of th e gears of th e m ach in e, and that death is determ ined by a disturbance o f this harmony. T h is harmony, this interlocking, obviously takes place; for th e respiration in the lungs is the cause of th e activity of the heart, and th e m otio n o f th e heart brings to th e brain at every m o m en t th e blood that has b een changed through respiration, whereby th e brain anim ates all the other or­ gans and again determ in es th e respiratory m otion s. T h e external im pulse for this m ech an ism [Getriebe] is, however, th e atm ospheric air in respiration. Any injury to one o f these m ainsprings in the m ech an ism [M echanism u s] of the organic body, every appreciable injury to the lungs, the heart, or th e brain can b eco m e th e cause of death, for w hich reason they have b een called th e atria mortis. But this harm ony of th e parts that are necessary for th e w h ole d oes n o t exist w ith ou t th e in flu en ce of a force which is also at work throughout the w hole and w hich does not dep en d on th e individual parts, and this force exists earlier than the harm onious parts o f th e w hole are present; they are created by th e force of the germ only during the d evelop m en t of th e embryo. W ith a purposefully constructed m ech an ism — e.g., a clock— th e purposeful w hole can exhibit an activity th at proceeds from the working together o f th e individual parts, on e that is set in m o tio n by on e cause; b u t organic beings exist n o t merely as a result o f an accidental com b in ation o f their elem en ts, they also generate the organs neces-

sary for the w hole by m eans of their forces o u t of organic matter. T h is rational creative force m anifests itself in every anim al according to strict law, as the nature of every anim al requires; it is already present in the germ, even before the later parts o f the w hole are separately present, and it is w hat really generates th e parts that belon g to th e con cep t of th e w hole. T h e germ is the w hole in potentia; during the d evelop m en t of the germ th e integrating parts of the w hole com e into existen ce in a ctu .m

A lthough M uller did no t explicitly say so, his conception of th e organism in fact allowed th e physiologist to analyze the life-sustaining operation of its organs in purely physicochem ical term s. Only the origin of those organs and of the structure of th e whole is beyond the physiologist’s com petency to deal with, though even there one can still provide a scientific description of developm ental processes inso­ far as they follow fixed laws. T hus M uller’s firmly held belief in a vital force did n o t necessarily entail a vitalistic explanation of m ost of the kinds of vital processes we consider to be properly physiological, th at is, n o t including embryological d e­ velopm ent.195 W ith respect to the latter, M uller rejected the preform ationist theory of em hoitem ent in favor of epigenesis, though w ithout using either term . In review­ ing th e evidence for the gradual developm ent of the em bryo from an originally undifferentiated state, he associated his view of the organizing force with Stahl’s anima— with one qualification: If [Georg] Ernst Stahl had know n th ese facts he w ould have b een even more co n ­ firmed in his celebrated view that the rational soul is itself th e primum movens o f the organization, that it is itself the u ltim ate and only cause [G rund] of organic activity, that th e soul purposefully constructs and m aintains its body according to the laws of its operation [Wirksamkeit], and that the curing o f diseases takes place through its organic a ctiv ity .. . . O nly Stahl w ent too far w hen he placed the conscious m anifesta­ tions of the soul on an equal rank w ith the organizational force, w hich m anifests itself purposefully b u t in accordance w ith blind necessity.196

T h at Organisationskraft, an “unconsciously working purposive activity,” gener­ ates and anim ates th e parts of the whole according to eternal laws and does not reside in any single organ.197 Consciousness, on the o ther hand, which does not create any organic products, is itself a late creation of embryological developm ent and is dep en d en t on the integrity of the brain. A lthough plants thus lack con­ sciousness, their m aterial form results from th e activity of th e organizing force, which follows th e species’ eternal archetype (Urbild). M uller’s organizing force was thus (at least here) less th e im m ediate cause of ongoing physiological functions than it was th e original ideal creator of the organ­ ism, a form -determ ining idea distinct from the form ed m atter. A lthough he de­ clined to press his reflections too far, it is clear where he saw his intellectual affinities to lie: Organic being, organism , is th e de facto [factisch] unity of organic creative force and organic matter. W h eth er the tw o have ever b een separate, w hether the creative arche­ types, the eternal ideas of Plato, as h e indicated in th e Timaeus, have at som e tim e

com e to m atter [zur M aterie gelangt sind ] and from th en on rejuvenate th em selves in every anim al and plant, is n ot an ob ject o f know ledge, b u t o f unprovable m yths and traditions th at clearly en ou gh indicate to us th e lim its of our mere co n sciou sn ess [unser blosses Bewusstseyn] .198

T his “de facto unity of th e organizing force and the organized m a tte r” (as he also p u t it) would be easy to com prehend, he said, if th e organizing force and all th e vital ph en o m ena were simply th e result of a particular com bination of the organism ’s m aterial elem ents, of its particular form and com position (Form und M ischung) } 99 But th e insufficiency of form to determ ine the course of organic d evelopm ent is shown by th e sim ilarity in th e initial em bryonic form of widely divergent species, and th e insufficiency of com position is shown by th e m aterial id en tity of an organism im m ediately before and after death. H ence one m ust assum e th e presence of som ething else in order to explain w hat distinguishes life from n o n life.200 Here again M uller pleaded ignorance b u t defended his ignorance by appealing to th e analogous ignorance of physical scientists: “W h e th e r one is to th in k of this principle as im ponderable m atter or as force is just as uncertain as the sam e question concerning several im p o rtan t phenom ena in physics, and physiol­ ogy does n o t here lag b eh in d th e o ther sciences, for the properties of this principle are nearly as well known in th e actions of th e nerves as those of light, h eat, and electricity in physics.”201 N othing b e tte r reveals th e protean n ature of conceptions of th e vital force th a n this transition, w ithin two pages, from its being regarded as a quasi-Platonic idea to its being spoken of as if it were som e kind of aetherial substance. Following now th e la tte r path, M uller argued for th e ability of this principle to act in and across space; following A utenrieth, he cited “th e capability of anim al parts whereby vital force is now w ithdraw n from , now com m unicated to them , and whereby the vital force often accum ulates rapidly in an organ.”202 Yet despite this belief in a kind of m obility (Beweglichkeit) of th e vital force, he had no hesitancy in dism issing anim al m agnetism as deception and superstition, evi­ dence only of m ost doctors’ incapacity to understand th e nature of em pirical scientific testin g .203 Insofar as M uller’s vital force was responsible n o t only for the organism ’s origi­ nal creation b u t also for its subsequent growth and reproduction, he found h im ­ self obliged, like A u tenrieth before him , to consider the problem of the creation and destru ctio n of vital force and its relationship to the o th er forces of nature, the chem ical and physical forces of the inorganic realm: Now, th e organic force is m u ltip lied during the grow th and propagation of organic bod ies, for from on e b ein g there co m e in to ex isten ce m any others, and from these again m any others, w hile on th e other hand th e organic force of dying organic bodies appears to perish. But since th e organic force d oes n o t merely pass (so to speak) from on e individual to another, since (rather) a plant, after it has annually generated the germ s of very m any new producers of th e sam e species, b ein g still capable o f th e same production, can remain a producer, th e n th e source o f th e increase in th e organic force also appears to lie in the organization o f new m aterial substances [Materien]; and granting this, on e w ould also have to ascribe to plants th e ability— insofar as they

form new organic substances out o f inorganic elem en ts [Stoffe] under th e in flu en ce o f light and heat— to increase the organic force from unknow n causes in th e external world, w hile anim als w ould in turn also be able to generate organic force ou t o f food under the influence of the vital stim u li, and to individualize it during propagation. W h eth er in th e execu tion of the vital processes [bei der Ausiibung des Lebens], b e ­ sides the con tinuous d ecom p osition of m aterials, organic force is also lost, and how it is lost, is entirely unknown. So m uch appears certain, however, that upon the death o f organic b od ies the organic force is again dissociated into its general natural causes, from w hich it appears to be regenerated by the plant. If on e did not wish to grant the increase in organic force in th e already present organic bodies from unknow n sources in the external world, th en o n e w ould have to assum e that the apparently infinite m ultiplication of organic force during growth and propagation is m erely an unfolding [Evolution] o f germ s en closed one inside th e other, or on e w ould have to assum e the inconceivable, that the division of the organic force that takes place during propaga­ tion does not weaken its intensity. But the fact w ould always remain that, up on the death o f organic b od ies, organic force con tin u ou sly b ecom es inactive or dissociated in to its general physical cau ses.204

Elsewhere M uller was more certain th a t the phenom ena of weariness and exhaus­ tion, at least, d em o nstrate “th at th e organic force is, as it were, consum ed in the execution of th e [vital] functions.”205 T hus th e organism requires a source from which to m ultiply and replenish its organic force, a source which apparently m ust be connected with th e nutrients plants and anim als take in from th e external world. It would be quite wrong, however, to interpret M uller’s cryptic reference to “unknow n sources in th e exter­ nal world” as an allusion to th e physicochem ical forces of inorganic nature, as if the organic force were som ehow a kind of higher transform ation of them . M uller did n o t here spell out what his views were, and a later analogy could also be read as im plying a causal connection betw een organic and inorganic forces, though the key (as we shall see presently) was in th e im plied latency of light and heat: “T he capability of being determ ined [bestimmt] by external influences to m anifesta­ tions of force is n o t proper to organic (in particular, anim al) bodies alone. For example, m any inorganic bodies develop light under certain conditions— e.g., through im pact— or they develop heat. According to physicists, it is probable th a t th e light or h eat was previously bound in th e bodies and becam e free as a result of th e external influence.”206 It was no t until th e third and last installm ent of the second volum e of his Handbook th a t M uller clarified his position: th e intended force of his analogy was th a t the vital force, and perhaps even the conscious soul, m ust be considered to be laten t in all m atter, requiring only special circum ­ stances— th a t is, organized matter·—to becom e m anifest. T hus the vital force was like th e o th er forces of nature only with respect to the formal aspects of its behav­ ior; it was n o t a m odification of them . Such clarification cam e only after an extended consideration of psychic life, or “th e life of the soul.”207 W riting now in 1839, M uller felt called upon to clarify the sense in which h e had spoken of the organism in m echanical term s six years earlier:

A t th e beginning of this work th e organism was com pared to a system of parts th a t have been co n n ected for th e a tta in m e n t of a certain purpose and whose operation dep ends on th e und istu rb ed harm ony of th e m em bers com posing it. T his com parison revealed a still greater difference th an similarity. T h e organism is like a m echanical device [mechanisches Kunstwerk} in its system atic com position for th e a tta in m e n t of a certain purpose; b u t th e organism generates in th e germ th e m echanism of the organs them selves, an d [thus] propagates it. T he action fW trken] of organic bodies does n o t d epend merely on th e harm ony of th e organs; rather, th e harm onv itself is a result [Wirkung] of th e organic bodies them selves, and every part of this whole has its basis [G rand] n o t in itself b u t in th e cause of th e whole. A m echanical device is created according to an idea in th e m ind of th e craftsm an, th e purpose of his activity [W irkung], An idea also underlies every organism , and all organs are purposefully organized in accordance w ith this idea, b u t this idea is outside th e m achine, on th e contrary in th e organism , and here it acts [or creates (sch a fft)] w ith necessity and w ithout inten tio n . For the purposefully active [wirksam] cause of th e organic bodies has no choice, and th e realization of a single plan is its necessity; in d eed for th is active cause to act [wirken] purposefully and to act w ith necessity are one an d th e sam e.20’’

T h e “idea” associated w ith each separate species was, M uller asserted, unchange­ able, and he renewed his denial of spontaneous generation. T h e new task at hand was to distinguish what he now preferred to call the “vital principle” (usually L ebensprincip, som etim es Princip des Lebens) from the sensi­ tive and im aginative soul o f anim als.209 Both are present in extended m atter and can (in a sense) be divided w ith the division of organic matter, but neither can be localized in th e body nor is either com p osed of parts. In order to m anifest itself, the vital principle requires only the participation of chem ical forces, whereas the soul requires th e presence of already organized m atter and the organization of the brain. Both, finally, can b e laten t, and it was this property that now enabled M uller more explicitly to suggest an answer to o n e of the ch ief questions he had posed in th e first installm ent of his book: A nd so there now finally arises th e question: How is it possible th a t through th e grow th of an organic being a m ultiple of its organizing force is form ed, an d how is a capability of th e psychic principle for division [eine Theilungsfahigkeit des psychischen Princips] to be u n derstood in connection w ith this? D oes it lie in th e n atu re of th e vital principle and th e soul as a power [Potenz] th a t they can n o t be dim inished in force through ap p o rtio n m en t [Vertheilung] to m ore m a tte r an d through division, or do m ore of those principles com e into existence through th e appropriation of m ore m a tte r in a growing organism as well, such th a t these principles are already present, la ten t, in th e food, b u t only m anifest them selves in th e m a tte r they are in in organic beings? T h e last assum ption necessarily entails a second one as well, th a t th e principle of life and the soul are la ten t in all m atter, for if anim als can live merely from plants, so can plants increase th e organic m a tte r from inorganic substances, and w ith o u t such a new form ation of organic m a tte r it w ould ultim ately b e entirely decom posed on ac­ c o u n t of th e putrefying and burn in g of so m any substances th a t do n ot en ter in to organic beings as food.

T h e em pirical investigation o f the relationship o f th e vital principle and th e soul to organization and to m atter does not go beyond this alternative. From here on the investigation distances itself from the dom ain of em pirical physiology and passes over into that of hypothetical speculation and philosophy.210

A lthough M uller refused to ally him self w ith either of th e two “cosmological sys­ tem s” he was about to exam ine, he certainly introduced the first in a way th at m ade it appear m ore problem atical and less consonant w ith w hat we otherwise know ab o u t physical phenom ena. In particular, he seem ed m ore disposed to ac­ cept th e possibility th a t vital force and soul exist in a laten t form associated (somehow) with m atter than th a t they are capable of indefinite division with undim inished strength. For my purposes, it is less im portant th a t M uller’s own deepest beliefs are difficult to fathom th an th a t one u n derstand the kinds of issues raised concerning forces and their creation or destruction as background to M ayer’s creation of a new concept of force. T h e first cosmological system M uller considered was one he called the “hy p o th ­ esis of m otive ideas [bewegende Ideen] inform ing organic bodies as the cause of organization and of psychic life [Seelenleben].”211 A lthough M uller did no t explic­ itly call atten tio n to th e distinction, its chief strength lay in its ability to account for th e form -determ ining, goal-directed, ‘ideal’ aspects of the vital (read: organiz­ ing) force. T h e second system, the “pantheistic view of the worldsoul and its relationship to m atter,” seems less well suited to an explanation of species’ con­ stancy of type than of th e energetic aspects of the vital (read: organic) force, of organism s’ m aterial and energetic relationships w ith th e external w orld.212 M uller’s term inological indecisiveness and his reluctance to declare explicitly for one or th e o ther of the two theoretically possible philosophical alternatives thus b o th reflect the fact th a t his vital force was being asked to perform at least two q u ite different functions. An em erging distinction betw een th e developm ental and th e energetic aspects of the vital force was still not fully self-conscious and explicit. According to M uller’s first cosmological system, Ideas of the divine m in d [gottlicher C eist] have, to be sure, b een realized in the w hole ordered universe, but only in organic beings are such divine ideas at work w hich perpetually generate their kind and create for th em selves out o f m atter the m ech a­ nism for th e actions o f organic bodies. T h e m otive idea of an organic body is therefore an em anation of the divinity, an em an ation that has lived in it and in its products since the C reation. T h is idea is th e only th in g that persists in organic bodies, for m atter abandons it and new m atter is ceaselessly subjected to this m otive idea. M atter itself is w ith ou t its inherent soul and life. N o t even th e power [Potenz] for these actions belongs intrinsically to matter. O n the contrary, all p h en om en a o f life and the soul that appear in the m atter processed by organic bodies depend solely on th e idea that governs th e organization.213

C entral to this viewpoint is the belief “th at the soul is foreign to the physical body, is n o t a force thereof, is no kind of force at all of m atter, and th a t the soul is only u nited w ith the body in the organic being.”214 Such a view strongly recalls

M uller’s own P latonic notion of th e “de facto unity of the organizing force and th e organized m atter.” However, this first cosm ological system cannot adequately deal w ith th e problem of th e m ultiplication of force— a problem w ith clear im pli­ cations for conservation-of-force type considerations: But since life and th e soul or the m otive idea are n ot la ten t properties o f all m atter, th e increase and division o f organic b ein gs— and w ith this hypothesis the sam e divi­ sion of souls— cann ot therefore be derived from th e assim ilation o f m atter through nutrition, and th e m u ltip lica tio n o f personally an im ated and en sou led beings m ust rather be explained on th e basis of a property o f the vital principle and th e soul as a result o f w hich—-opposed and foreign to all behavior o f [material] b o d ies— their force is n o t dim in ish ed and w eakened through division to infinity. A property w hich is difficult for th e understanding to co n ceiv e o f.2b

N o sooner had M uller defined in general term s the essential features of the alternative “p an th eistic view” th a n he called a tte n tio n to its success in addressing just th a t problem : T h e theory opposed to th e foregoing is that th e principle of life inheres in all m atter and so little has b een superadded to m atter that it is n o th in g b u t a force of m atter itself, but one th at m an ifests itself only for such and such a form under precise co n d i­ tions and given a precise co m p o sitio n of m atter and a precise structure. W h en it enters th e organic body, m atter encou n ters th e con d ition s under w hich th e principle of life latent in it m u st m an ifest itself in th e precise form of that organic body. In this way the increase in organic force to a m u ltip le through growth and its capability for division are th en easily conceivable. But everything living that passes away loses m erely th e con d ition for th e m an ifestation of life in th e precise form [it h ad ], and the en souled m atter capable of life returns again to th e w om b [Scfioos] of nature.216

In order to account for th e constancy of organic form , M uller appealed to Gior­ dano B runo’s p an th eistic worldsoul as everywhere active and form -determ ining: all things partake of th e ubiquitous divinity, or G odhead (G ottheit), whose activ­ ity fu rth er allows organic beings to m anifest th e organic force th a t lies u n d etected in “th e so-called dead m atter.”217 M uller w ent on to treat th e soul analogously to th e vital force: b o th are laten t in m atter, sim ultaneously in d ependent of it for th eir existence and d ep e n d en t on it for th eir expression. M uller’s extensive discussions of th e vital force, hedged and noncom m ittal as they usually were, gave no indication th a t m any of his contem poraries were b e ­ com ing increasingly critical of th e whole notion. T h e anti-vital-force views ex­ pressed by Elsasser in a relatively obscure place in 1834 and given m ore expansive trea tm e n t by V etter in an apparently little-noted talk published in 1837 were, two years thereafter, m ade a m ajor topic of an im portant section of a highly regarded book by a m ajor figure: the long philosophical excursus on th e “T heory of C ells” in T h eo d o r Schw ann’s Microscopical Investigations o f the Agreement in the Struc­ ture and Growth o f Anim als and Plants of 1839.218 (Schwann had been M uller’s assistant in Berlin from 1834 to 1839.) To be sure, their m otives were som ew hat different. Elsasser was concerned with th e n ature of scientific explanation and the

p rogram m atic d esirability o f p u rsu in g ex p la n a tio n s in term s o f th e u su al p h y sic o ­ ch em ic a l laws; h e also rejected th e a ssu m p tio n o f forces a lleg ed to ex ist in d e p e n ­ d en tly o f m atter— ex c ep tin g , o f cou rse, p sych ic a ctiv itie s (geistige T h a tig k e ite n ) . Vetter, on th e o th er h an d , was principally co n cern ed w ith issu es o f p hysical ca u ­ sality and creation o u t o f n o th in g . W h a t S ch w an n m o st o b je cted to was th e n o ­ tio n th a t th e vital force acts p u rp osefu lly in th e m a n n er o f a rational agent: T h e different views on th e fundam ental forces of th e organism can be reduced to two, essentially different from each other. T h e first view is th a t every organism is underlain by a force [άαβ jedem Organismus eine Kraft zu Grunde liegt] th a t forms th e organism in accordance w ith an idea present to it an d joins to g eth er th e m olecules in such a way as is necessary for th e a tta in m e n t of certain purposes defined by this idea. Such a force would be essentially different from all of th e forces of inorganic n atu re because only blind action [ein blindes W irken] takes place in th em . In inorganic n a­ tu re a certain influence is necessarily followed by a certain qualitatively and q u a n tita ­ tively determ in ate change w ithout consideration of a purpose. According to this view, however, th e fundam ental force of th e organism , or th e soul in S tah l’s sense, would stand m uch closer to th e im m aterial principle endow ed w ith consciousness th a t we m u st assum e in h u m an beings, in th a t it acts in accordance w ith a d eterm in ate in d i­ vidual purpose. T h e other view is th a t th e fundam ental forces of organism s are essentially in agree­ m e n t w ith th e forces of inorganic nature, in th a t they act blindly, entirely according to laws of necessity w ith o u t regard to purpose, and in th a t they are forces th a t are assum ed given w ith th e existence of m a tte r in th e sam e way as th e physical forces. . . . Purposefulness— even a high degree of individual purposefulness of every organism — can by no m eans be denied. O nly according to this view, th e basis [Grund] of this purposefulness does n o t lie in the fact th a t every organism is produced by an individ­ ual force acting in accordance w ith a purpose; it lies rath er in th e creation of m a tte r w ith its blind forces by a rational being, wherein also lies th e basis of th e purposeful­ ness in inorganic nature. . . . O ne can call th e first view on the fundam ental forces of organism s th e teleological, th e second th e physical view point.219 In S ch w an n ’s o p in io n , th e life sc ien ce s sh o u ld fo llo w th e ex a m p le o f p hysics, w h ich has lo n g sin ce b a n n ed all tele o lo g ic a l ex p la n a tio n s su ch as th e su p p o sed horror vacui. In o p p o sin g th e “tele o lo g ic a l v ie w p o in t,” w h ich h e a sso cia ted w ith th e a ssu m p ­ tio n o f th e e x iste n c e o f a g oal-d irected force (or id ea) as ca u se o f th e organ ism ’s vital activities, S ch w an n was q u ick to se ize u pon th e p rob lem o f g en era tio n , o f w here th e n ew force co m e s from: If one assum es th a t every organism is underlain by a force th a t forms it in accordance w ith an idea present to it [nach einer ihr vorschwebenden Idee], th en a portion of this force can indeed also be contained in th e egg during generation; only one m u st then ascribe to this portion of the original force, at the separation of th e egg from th e m aternal body, th e capability of being able to produce an organism sim ilar to th e one

produced by th e force of w hich it is only a portion, i.e., one m u st assum e that this force is divisible to infinity and that each portion can nevertheless produce th e sam e effects as th e w hole force.220

N o t availing him self of A u ten rieth ’s preterphysical realm or M uller’s notion of latency, Schw ann pressed hom e th e sim ultaneously q uantitative and causal objec­ tions to th e n o tion of th e ap p o rtio n m en t (Vertheilung) of vital force which Volkrnann had simply ignored. T he “physical view point,” on th e o th er hand, which Schwann advocated, faces no such problem s: there are no forces peculiar to living things. O nce again th e consideration, in a broadly physiological context, of prob­ lem s associated with belief in an efficient form ative force led to conclusions strongly suggestive of som e kind of intuitive conservation principle. Schwann did n o t categorically reject th e possibility th at th e explanation of or­ ganic p henom ena m ight require the assum ption of laws different from those of inorganic n ature, insisting only, like A utenrieth before him , th a t any such laws m u st likewise operate w ith “blind necessity.”221 If we grant purposefulness to the original creation of things, th en we can allow all su b sequent processes to take place according to those necessary laws. However, teleological explanations are only to be allowed where th e im possibility of a physical explanation has been d em onstrated, presum ably such as w ith respect to the original creation of bo th th e inorganic and organic worlds. O ne young scientist who took Schw ann’s program to h eart was M ayer’s close friend, th e psychologist W ilhelm Griesinger, who in D ecem ber 1842 urged Mayer to apply his ideas to physiology and thereby to contribute to th e ongoing reform a­ tion of th e life sciences toward w hich G riesinger and his cohort were working: O nly I confess to you, wherever I see a possibility o f w resting w hat goes on in the organism from the m ysterious m ysticism of the vitalists, etc., and of finding for it som eth in g analogous or identical in the rest o f m atter to w hich organized m atter were also sub jected, I regard it as progress. T h e d evelop m en t and ach iev em en t o f a purely physical view of vital processes I regard as th e task o f the physiology o f our day. You probably know w hat brilliant con trib u tion s Schw ann, for exam ple, has m ade to su ch .222

For his part, M ayer had serious misgivings ab o u t certain contem poraries’ m ateri­ alistic an d reductionist aproach to life, one w hich would later seize upon the conservation of energy in defense of its position. In retrospective remarks m ade toward th e end of his life, Schwann recalled his earlier opposition to the notion of a vital force as a principle distinct from m atter, regarded as th e “architect” of th e organic edifice, and w ith which one explains the properties of m uscles, nerves, and glands in term s of th eir contractility, irritability, and secretory function.223 W ith respect to only one phenom enon, formerly passed over in silence, did Schwann qualify his belief th a t all aspects of organic life can be accounted for strictly in term s of th e laws of m atter: “O nly freedom establishes a lim it where explanations in term s of forces of this kind m ust necessarily stop. It obliges us to ad m it for h u m an beings alone a principle th a t is substantially distin-

guished from all th e forces of atom s by this essential characteristic, by freedom , which is incom patible with th e properties of m atter.”224 But of course Schwann never regarded him self as responsible for accounting for the operation of the uniquely h u m an free will. T he reach of determ inistic laws defined th e scope of his science. N ot surprisingly, th e role life scientists assigned to a vital force depended to a considerable ex ten t on the specific range of phenom ena w ith which they were m ost centrally concerned. Nevertheless, th e fact th a t a scientist’s choice of subject did n o t entail any recourse to a vital force does no t m ean th a t he rejected the reality of such an agency. Rather, w hat was involved for some was m ore a m eth o d ­ ological restriction to certain types of problem s th an a principled rejection of the com plete illegitimacy of vital forces. T h e effect of this de facto exclusion, how ­ ever, was to co n trib ute to th e growing sense, in th e years around 1840, th a t the vital force had no role to play in the scientific explanation of physiological p h e­ nom ena. Jakob H enle’s General Anatom y, published betw een 1839 and 1841, is a good illustration of this. M ost of the 1,048-page book consists of detailed anatom ­ ical descriptions and precise physicochem ical analyses, as one would expect from one of th e leaders of the self-conscious reform of th e life sciences in Germany. However, in a four-page section headed “O rganism ”— perhaps intended as a reply to Schwann— H enle revealed th a t he was very far from being a physicochemical reductionist. He asked w hat holds th e organism together and determ ines th e typ­ ical developm ent of its individual parts— questions q u ite unaddressed in th e body of his work. His som ew hat diffident answer was to enter a plea for the necessity of positing th e operation of a vital force, by which he recognized th a t he was going against the tendency of m any of his contem poraries: It is only w ith re sp e ct to re c e n t a tte m p ts a n d h o p es to re d u c e d e v e lo p m e n t a n d th e vital p h e n o m e n a of th e o rg a n ism to p hysical laws th a t I w o u ld like to in d ic a te in a few w ords th e d ifferen ce b e tw e e n th e force active in th e o rg an ism a n d th e forces of d e a d n a tu re . It differs already in th e c o m b in a tio n s o f e le m e n ts th a t arise u n d e r its in flu ­ en ce, in its cap ab ility to p ro d u c e m u ltip le co p ies of itself [sich zu vervielfaltigen] or to e x te n d itself over an ever g re a te r m ass o f m a tte r w ith o u t loss o f in ten sity , b u t e sp e ­ cially in its p e rsisten ce a lo n g sid e th e ex ch an g e of m a tte r. . . . T h e force active in th e o rganism is th erefo re n o t m erely th e sum o r th e p ro d u c t o f th e forces of its in d iv id u al c o m p o n e n ts, fo r it o u tla sts th e s e c o m p o n e n ts .225

In addition to the role of this force in producing complex organic com pounds, H enle assigned it th e further traditional tasks of generating offspring true to the species type (even by m utilated parents) and of regenerating lost lim bs— again, topics he did n o t otherw ise address in this book. His belief th at this force is capa­ ble of indefinite self-m ultiplication recalls A utenrieth’s sim ilar views, and rem inds us th a t ‘conservation of force’ was by no m eans obvious to everyone, especially when one was dealing w ith living beings. H enle’s special organic force, an Idee der G attung, was in th e long tradition of Platonic ideas and K antian purposefulness, the tradition of B lum enbach’s Bildungstrieb:

T h a t w hich forms and m aintains th e organism (one has called it vital force, organiz­ ing force, form ative force, etc.) is therefore n o t a force in th e physicists’ sense which is assum ed to be given necessarily and absolutely w ith the existence of m a tte r and w hich is bound to m atter; it does n o t perish w ith th e individuals; b u t it m anifests itself in so originally and constantly different a m an n er in th e individual species or at least genera of anim ate beings th a t one can n o t regard th eir specific conditions as having proceeded from the conH ict betw een a sim ple an d general organizing principle and th e m anifold agencies of lifeless creation. I therefore believe th a t this principle active in the organism is best designated as th e idea o f the race, and would lilce thereby to express th a t w hich characterizes this principle: on the one h an d its spontaneity, its in d ependence from m atter; on th e o th e r h an d its concrete n ature. T h e idea of the race is, as it were, th e preform ed form in to w hich grows th e germ th a t develops into th e organism . O ne can n o t do w ith o u t teleological explanations in physiology, for th e pro­ cesses of n u tritio n an d regeneration can only be u n d ersto o d in term s of th e goal they pursue. T h e idea of th e race strives tow ard a goal, b u t it strives tow ard it w ith necessity. W ith respect to lifeless nature, th e organism is auton o m o u s, it develops w ith sp o n ta­ neity, b u t in and of itself th e developm ent is a necessary one, given from th e start in th e germ . . . . Physiology m u st distinguish and seek to discover how far th e vital p h en o m en a and reactions are determ ined by th e ir original organization and th e striving toward an originally set goal, how far by th e influence of th e external world on living substance. T his goal is difficult to attain , b u t physiology will acquire a m ore dignified statu re if it rem ains conscious of it.226

In rejecting just this con cep tion of th e vital force as a purposefully directing for­ m ative force, Schw ann had attacked its legitim acy in its ostensibly securest do­ m ain, that of developm ent. As just presented, th e status of vital force(s) in the life sciences of the 1830s was com plex, and one o f th e m ost crucial issues— w hether the vital force is responsi­ ble solely for the direction of certain com plex organic operations or w hether it can legitim ately be invoked to explain processes that we w ould say involve the doing of work— was not explicitly so addressed, despite the fact that there was w ide­ spread gut sensitivity to th e issue. Moreover, there was appreciable consensus over the illegitim acy of treating the vital force as if it provided a m eaningful causal explanation o f otherw ise inexplicable phenom ena. Rather, the clear tendency within physiology was to seek as far as possible to account for all vital phenom ena in term s of underlying chem ical and physical processes, as sym bolized by the growing conceptual prom inence of Stoffwechsel. Processes such as embryological develop m en t and the operation of the m ind , which could n o t be plausibly so treated, increasingly fell outside th e com peten cy o f physiology. Perhaps indicative of the increasingly m arginalized status of th e vital force in the late 1830s was its

acceptance by philosopher Friedrich Fischer in his elaborate defense of spiritual­ ist phenom ena (Somnam bulism us, which to him and his contem poraries m eant not just sleepwalking b u t also anim al m agnetism , clairvoyance, possession, and th e like). Fischer recognized others’ reluctance to use th e adm ittedly hypothetical concept as he urged his interpretation of som nam bulistic phenom ena as some kind of transform ation of vital force into soul. For th e rest, his conception of the functions perform ed by the vital force was entirely conventional; it formed, m ain­ tained, and anim ated the organism .227 Physicists som etim es felt obliged to address th e issue of the existence of a force o th er th an th e well-known physical and chemical forces, at least in elem entary texts and inclusive handbooks. M uncke, for example, followed the opinion of m any in believing th a t a vital force is needed to explain the body’s production of com plex chem ical com pounds, and th at we otherwise know essentially nothing ab out its essence or m ode of existence, especially since we cannot im agine a force existing independently of a m aterial substrate.228 In 1831 he devoted a separate article to th e vital force in Gehler’s Physical Dictionary, the standard m ultivolum e com pendium of th e day. C hoosing a m iddle position betw een physiologists who denied any special life forces and those who attrib u ted some m easure of life to all bodies, M uncke believed he was with the majority in accepting the existence of special vital forces.229 M ost of the phenom ena he assigned to th at force were the usual ones— n u trition, growth, generation, and the creation of com plex chemical com pounds— b u t M uncke believed th a t other phenom ena, such as the capillary rise of sap in plants, the ascent of the blood against gravity to the brain, and anim als’ m aintenance of a constant tem perature, also depend on other th an phys­ icochemical laws, indeed suspend the norm al laws of nature.230 Such a belief was not, however, very com m on. Physicist Baum gartner, for exam ple, lim ited the role of the vital force in the usual fashion to the production of complex organic sub­ stances such as blood, flesh, nerves.251 T h e leading chem ists, too, accepted a vital force as necessary to explain the body’s ability to synthesize complex substances, though the terrain dom inated by th at force shrank as chem ists succeeded in synthesizing ever more and increas­ ingly complex organic com pounds. T he vital force, even when no t disallowed, seem ed more to m ark the tem porary lim it of our ever-expanding knowledge than to designate an essential and peculiar agency of living things. T h e progression of Berzelius’s thinking on th e m atter is instructive. Allowing, to be sure, th a t the ultim ate m aterial constituents of anim als' bodies are precisely those of inanim ate nature, Berzelius in 1810 believed th at even inorganic sub­ stances undergo transform ations within the body th a t are fundam entally unlike those we are able to observe directly. T h e body is, he im agined, an “instrum ent” for carrying o u t chem ical transform ations in the interest of its own survival: But, w ith all th e know ledge we possess of the forms of the body, considered as an instrum ent, and of th e m ixture and m utual bearings of the rudim ents to one another, yet the cause of m ost o f th e phenom ena within the Anim al Body lies so deeply hidden from our view, that it certainly will never be found. W e call this hidden cause vita l

power; an d like m any others, who before us have in vain directed th eir delu d ed a tte n ­ tio n to this p oint, we m ake use of a word to w hich we can affix 110 idea. T his power to live belongs n o t to th e c o n stitu e n t parts of our bodies, nor does it belong to th e m as an instru m en t, n eith er is it a sim ple power; b u t th e result of th e m u tu al operation of th e in stru m en ts and ru dim ents on one an o th er . . . . W h e n our elem entary books inform us, th a t th e vital power in one place produces from th e blood th e fibres of the m uscle; in another, a bone; in a third, th e m edulla of th e brain; and in an o th er again, certain hum ours, w hich are destined to be carried off; we know after this explanation as little as we knew before. T his unknow n cause of th e phenom ena of life is prim arily lodged in a certain part of th e A nim al Body, viz. in the nervous system , th e very operation of w hich it consti­ tu te s. T h e brain and the nerves determ in e altogeth er th e chem ical processes which occur w ithin th e body.232

T hus the vital force was, from th e standpoint of organic nature, an indispensable agency, b u t from th e standpoint of science it was an em pty concept— though its inconceivability reflects our general epistem ological im potence w ith respect to ultim ate causal explanations; “And the chain of our experience m u st always end in som ething inconceivable; unfortunately, this inconceivable something acts the principal part in A nim al Chem istry, and enters so into every process— even the m ost m in u te, th a t th e highest knowledge which we can attain, is th e knowledge of th e n ature of th e productions, whilst we for ever are excluded from th e possibil­ ity of explaining how they are produced.”233 N or can we explain how blood is transform ed into saliva, milk, or urine, or how our thoughts m ight depend on chem ical transform ations in th e brain. Nor did Berzelius here think we would ever succeed in p en etratin g th e secrets of life: “But is it n o t probable, th a t hum an understanding, which is capable of so m u ch cultivation, which has calculated the laws of m o tio n for d istan t worlds, and explored in so m any instances the beauty and wonders of surrounding nature, and even attained a degree of perfection, the sum m it of which is concentrated in G O D , m ay one day explore itself and its nature? I am convinced it will n o t.”234 Seven years later Berzelius repeated his conviction th at th e co n stitu en t parts of organic bodies follow different laws th an inorganic substances. Now, however, the discovery of th e nature of th a t difference seem ed to h im som ew hat less decidedly beyond h u m an capacities. In essentially unchanged portions of his influential Textbook o f Chemistry in editions spanning te n years, Berzelius wrote th at “to discover th e cause of this difference betw een the behavior of th e elem ents in dead n atu re and in living bodies would b e th e key to the theory of organic chemistry, ft is nevertheless hidden in such a way th a t we are w ithout any hope of finding it out, at least for th e present. N otw ithstanding th at, we m ust strive to com e closer to this knowledge; for one day we shall either succeed in wholly attaining it, or com e to a halt at a definite lim it, beyond which th e hum an powers of investiga­ tion cannot be fu rther ex tended.”235 But having m ade th a t small concession, Berzelius seem ed im m ediately to take it back, appealing to th e necessary creative role of a tran scen d ent being in bringing life to our planet. W h e n it dies, a living

individual returns undestroyed to th e inorganic realm the basic material com p o­ nents of its body, b u t its life is irrevocably destroyed. T h e essence of the living body is consequently n o t grounded in its inorganic elem ents, b u t in som ething else which disposes the inorganic elem ents com m on to all living bod­ ies to th e production of a certain result specific and proper to every particular species. T his som ething, w hich we call vital force, lies wholly outside th e inorganic elem ents an d is n o t one of their prim itive properties such as weight, im penetrability, electrical polarity, etc.; h u t w hat it is, how it com es into being and com es to an end, we do n o t com prehend. It m ay thus be predicted th a t if th e globe existed w ith its inorganic co n stituents w ithout living natu re b u t u n d er otherw ise identical conditions, it would co n tin u e forever to be w ithout living beings. A force incom prehensible to us and foreign to dead nature at one tim e brought this something into the inorganic mass, and n o t in such a way as if it were the work of chance, b u t with a wonderful diversity, and disposed [berechnet] w ith the highest w isdom to definite purposes and to an un ending succession of perishable individuals arising o u t of each other, and where in a constant exchange th e destroyed organization of one con trib u tes to th e m a in te­ nance of th e other.236

T he practical evidence for the operation of the vital force was, as Berzelius said, the fact that chem ists are incapable of producing m ore than binary com binations of chem ical elem en ts.257 Yet that reason, repeated in 1837 in words unchanged from 1827, had by th e later date been rendered untenable by the progress chem ­ ists had m ade in the intervening years in the synthesis of more com plex organic com pounds. Two years later, in a reflective essay, “O n Som e Q uestions of the Day in Organic Chem istry,” Berzelius reinterpreted the vital force as nothing more than an expression for the com plex circum stances w ithin which organic chem ical processes take place: there are no special organic forces per se. T he goal was still to discover the laws that determ ine the com bination of the elem ents in organic com pounds: But w hich are these laws? Does the vital force in organic nature place th e inorganic elem ents u nder the influence of forces other th an those th a t effect their com bination in inorganic nature? T his last question has been variously answered. O ne has assum ed th a t th e vital phenom ena depend on a particular force foreign to inorganic nature, which one called vital force. Physical and chem ical phen o m en a th a t are so different from those of inoTganic nature th a t they indeed appear to justify such an explanation certainly do take place in living nature; b u t w hen we investigate th e details of th e effects [or actions (Wirkungen)] of this force, we recognize therein the interplay of th e custom ary natural forces placed u nder th e influence of a m u ltitu d e of disparate condi­ tions th a t produce th e diversity of th e effects. W e are certainly still far from com pre­ hending w hat determ ines all of th e vital phenom ena, b u t it is obvious from the por­ tion of th em th a t we have succeeded in laying bare th a t if by vital force som ething else is understood than the particular circum stances acting to g eth er in different ways u nder which th e custom ary n atural forces are set in operation in organic n ature, if one thereby understands a particular, special natural force, [then] this natural force is an

h yp oth esis w hose existen ce is as y e t unproven and w h ose assu m p tion is o n e o f the m any cases in w hich w e, follow ing A lexander’s exam ple, cu t th e knot instead of u n ty­ ing it.238

As far as Berzelius the chemist was now concerned, the notion of a vital force is as em pty as it is unnecessary.239 R esponding to essentially th e sam e evidence as Berzelius, M ayer’s chem istry professor, C hristian G o ttlo b G m elin, could no t bring him self wholly to renounce th e need for a vital force, b u t his position looked like a halfhearted rearguard defense of territory ultim ately and inexorably to be lost. His 1835 Introduction to Chemistry, which M ayer owned, treated th e vital force as a kind of supram aterial agency responsible for th e construction of th e organism . T h a t vital force is, how ­ ever, capable of regulating th e reactions of only a small n u m b er of chem ical ele­ m ents, which form its “m aterial su b strate” as iron does for th e “m agnetic force.”240 It directs th e form ation of characteristically organic com pounds and th u s also of th e organic body as a whole, w hich it anim ates and whose au to n o ­ m ous developm ent it regulates. But th e vital force ultim ately separates itself from th e organic body, which is th e n given over to th e destructive forces of inorganic n ature— th at is, it rots and decays. AU this was standard fare. G m elin was forced, however, to recognize th a t th e distinction betw een inorganic and organic com ­ pounds, as binary on th e one han d and ternary and quaternary on the other, could no longer be m ain tained. Som e binary com pounds could (it seem ed) only be created th rough th e agency of th e vital force, and som e ternary and quaternary com pounds formerly regarded as necessarily organic, such as urea, cyanuric acid, acetic acid, and alcohol, could now be artificially synthesized. But although th a t traditional d istinction would have to be abandoned, G m elin did no t thereby sur­ render his belief in the vital force, which he th o u g h t still acts to facilitate certain chem ical com binations in the organism and under whose influence a large n u m ­ b er of com binations are effected “which up to now have no t been able to be produced w ith o u t its cooperation”: “T h e diversity of th e com pounds form ed from th e few elem ents— carbon, hydrogen, oxygen, and nitrogen— which are th e m ate­ rial substrate of th e vital force is so extraordinarily large th a t one can confidently assert th a t it will never prove possible to create all of the organic com pounds artificially, i.e., to replace the vital force by o th er forces such as light, heat, elec­ tricity, th e nascent state, e tc .”241 In th e end, G m elin’s vital force was prim arily only an agency of chem ical change, different only in degree from inorganic chem ­ ical affinities and increasingly dispensable as chem ists perfected their science. H eidelberg pharm acist and chem ist Philipp Lorenz Geiger invoked a vital force in a wholly perfunctory fashion to account (as usual) for th e production of organic bodies and com plex organic com pounds; its existence was n eith er a theoretical issue nor a m a tte r of particular practical significance to his chemistry.242 T h e treatm en t of the vital force by chem ist (and extraordinary professor of m edicine at Leipzig) C arl G o tth elf L ehm ann provides a curious indicator of its fast-changing statu s am ong G erm an scientists during th e early 1840s. In effect, like Berzelius in 1810, L ehm ann accepted its reality by attrib u tin g to it th e control

of processes b e y o n d o u r cap acity to ex p lain in te rm s of p h y sico ch em ical law s, w hile a t th e sa m e tim e d e n y in g it any leg itim acy as a scien tific e x p lan a tio n . As L e h m a n n w ro te in th e 1841 preface to his Textbook o f Physiological C hem istry, his aim was “to re d u c e th e o fte n m u ltip ly in te rc o n n e c te d p h e n o m e n a to th e sim p lest laws a n d th e re b y to se p a ra te th a t w h ich is ex plicable in te rm s of physical a n d chem ical laws from th a t w h ich is in ex p licab le, i.e., from th a t w h ich m u s t rem ain given over to th e vital fo rce.”243 In th e sam e vein, h e la te r w rote th a t o n e is usually c o n te n t to assu m e th a t th e processes of g ro w th a n d n u tritio n “rest o n th a t in ex ­ plicab le s o m e th in g w h ich , as a g en eral v ita l force, . . . m o st re c e n t physiologists allow ed to play an im p o rta n t th o u g h still u n in te llig ib le ro le .”244 For L e h m a n n , th e vital force was only o n e ex am p le of th e k in d of p se u d o -ex p la n ato ry e n tity we are o fte n c o m p e lle d to in tro d u c e w h en we find ourselves a t th e lim it of th e scien tifi­ cally explicable, th o u g h h e d e c lin e d to tak e th e n ex t ste p a n d categorically reject th e vital force as b o th m ean in g less in p rin cip le a n d u n n ecessary in fact as science steadily claim s m o re an d m o re te rrito ry from th e previously inexplicable: Even in the natural sciences [as in the science of organic nature] when we lack facts, calculation deserts us, and positive proofs quit us, we m ust have recourse to so-called dynamic explanations: b u t just because this always betrays a lack of definite knowl­ edge, just because the dynamis [or dynamic potentiality (Dynamis)] is something inexplicable, we should never grant too much scope to such modes of explanation, which betray themselves as more or less pure webs of fantasy. We m ust therefore even in anim ate nature seek to push back as far as possible this dynamis, the vital force, by means of which one thought one could explain everything, and which explains noth­ ing; we m ust make an effort to win ever more territory away from it, the inexplicable, and to pursue it up to the farthest boundaries, which our intellect [Geist] is no longer capable of crossing. We must, finally, vindicate for the all-powerful laws of physics and chemistry the rights they do not surrender even to organized bodies; in a word, we m ust draw over into the realm of the known and the explicable th at which was previ­ ously given up as inexplicable with the words vital force, and we m ust confine this dynamis to only the farthest limits of hum an investigations.245 A n an o n y m o u s an d largely s y m p a th e tic review er of L e h m a n n ’s b o o k — possibly L o tz e 246— was q u ick to seize o n th e irra tio n a lity of L e h m a n n ’s h a n d lin g o f th e vital force. As th e review er rem ark ed , L e h m a n n h a d said th a t th e d y n am is, th e vital force, m u s t b e p u sh e d b ack as far as p ossible, to th e o u te r lim its of h u m a n u n d e rsta n d in g ; at th e sa m e tim e , he was w illing to assign to th e vital force th e e x p la n a tio n of p ro b lem s n o t now soluble. W h a t one requires in ste a d is a d e m o n ­ stra tio n th a t th e v ital force is in p rinciple in a d m issib le in scien tific ex p lan atio n s: Nevertheless, remarks such as on p. 99 and elsewhere, where the rights of the dynamis alongside the chemical laws are expressly recognized, indicate th at the author does indeed wish to concede to this vital force a real, albeit very limited, sphere of activity. Nevertheless, the excellent scientist thereby gets into an odd position with respect to this dynamis. Namely, if a real vital force is anywhere assumed as an active cause of the phenomena, it then cannot be in the interest of science, given this recognition,

n ev erth eless to re d u c e th e p h e n o m e n a to o th e r p rin cip les m erely b e c a u se th a t force is by its n a tu r e o b scu re a n d d iffic u lt to c o m p re h e n d . If it really is th e vital force th a t governs organic ev e n ts in even o n ly a few p o in ts, th e n it m u s t by rig h ts also b e m a in ­ ta in e d , a n d a re d u c tio n o f ev ery th in g o rg an ic to m e c h a n ic a l p rin cip les can th e n no lo n g e r hav e th e value o f tr u th , b u t only th a t of a tr e a tm e n t for c e rta in p u rp o se s by m e a n s of th e s u b s titu tio n o f im ag in a ry b u t law fully c o n n e c te d g ro u n d s. T h e pro p o sal to a ss u m e a vital, physically law less fo rce o n ly in th o s e cases w h ere all physical p rin c i­ ples d o n o t suffice for a c o m p le te e x p la n a tio n c a n th e re fo re b e reg ard ed only as a te m p o ra ry giving u p a n d b rea k in g off of th e in v e stig a tio n . B u t o n e m u s t n o t regard th is vital force as only a n o th e r ex p la n a to ry p rin c ip le , th o u g h o n e h av in g th e sam e leg itim acy as th e m e c h a n ic a l p rin cip les. It is th e re fo re n o t only a q u e s tio n o f p u sh in g back , th ro u g h d e v e lo p m e n t o f th e m e c h a n ic a l view s, th o s e g ro u n d le ss a n d — as th e a u th o r h im se lf calls th e m — always m o re or less fa n ta stic p re su p p o sitio n s, of w in n in g te rrito ry aw ay fro m it, b u t also of sh o w in g o n c e a n d for all th a t th e s e a ss u m p tio n s are in p rin cip le in a d m issib le , a n d th a t th e as y e t u n so lv e d rid d les m u s t b e reg ard ed sim ply as u n e x p la in e d facts, n o t as facts e x p licab le only b y m e a n s o f th o s e a s s u m p tio n s .247

For th e reviewer, w ho sought a science based on valid principles, the sam e laws of physics and chem istry govern all the p h en om ena of nature; organism s seem to require additional explanatory principles only because of the special circum ­ stances under which those general laws operate, that is, the finely contrived struc­ tures of the organic m achine. H e insisted that “ [the] difference b etw een inorganic and organic is not an original difference in th e active forces, but only in the exter­ nal m echanical cond itions under w hich the latter are active.”248 T he origin of the all-im portant initial disposition of m atter— w hether of organisms or o f the solar system — lies ou tsid e th e scope of scientific explanation. L ehm ann’s book also received warm praise from fellow physiological chem ist Franz Sim on, who apparently m issed the am bivalence in L ehm ann’s handling of vital force. W lrile concedin g that organic phenom ena are governed by other than purely physical laws, Sim on insisted that one need not therefore relegate those phenom ena to a m iraculous vital force.249 For h im , the vital force is neither scien­ tifically respectable nor physiologically necessary. A nother am bivalent chem ist was Berlin professor H einrich Rose, w ho in 1843 shared at least in part the grow­ ing consensus that the vital force is an illegitim ate scientific con cep t that one invokes to explain the otherw ise inexplicable, but who also believed there is a lim it to our ability to understand the processes of life, a lim it on the other side of which lies an active vital force. As he wrote in his review o f Liebig’s A nim al C hem ­ istry: As is well know n, we call th e h id d e n c a u se of th e activ ity o f living o rg an ic b o d ie s v ita l force, a n d o n e was earlier c o n te n t to regard all of th e c h e m ica l processes in th e living b o d y as a resu lt th e re o f. . . . O n e h as recen tly a tte m p te d to stu d y m o re closely th e m o st im p o rta n t pro cesses in th e living o rg an ic b o d y from th e s ta n d p o in t of c h e m istry in o rd e r to ex p lain th e ir resu lts in a way o th e r th a n as deriv in g precisely fro m th e vital force. Every a tte m p t of th is k in d m u s t be receiv ed th an k fu lly ; fo r w e a lm o st n e v er a tta c h a co rre c t, clear

conception [Vorstellung] to the words vital force. It is convenient to ascribe to it every process that is difficult to explain. But insofar as the phenom ena whose cause it is supposed to be are represented as being so entirely anom alous with respect to all other known phenom ena, the concept one attaches to it is a m ystical, confused one. The more, therefore, one lim its the territory of the processes that one m ust ascribe to the vital force, the more science wins; arbitrariness disappears when known laws can be applied. To be sure, the application of known laws to chem ical processes in the living body will remain lim ited, and the hum an intellect cannot for the present penetrate beyond a certain lim it.2’0

Rose w ent on to q u o te B erzelius’s thirty-year-old expression of diffident accep­ tan ce of th e necessity of assum ing th e activity of a vital force, and of his belief in th e u ltim a te scientific inexplicability of life.251 M ethodological opposition to a vital force was b ecom ing increasingly w ide­ spread during th e early 1840s. A m ong those rejecting it as an em pty verbal cover for o ur ignorance was M atthias Schleiden, w hose Principles o f Scientific Botany (1842-43) co n tain e d a long and im p o rta n t “M ethodological In tro d u c tio n ” in w hich he criticized th e vital force in strongly red u ctio n ist term s: “S om ething is as little explained by m ean s of a distinctive vital force as th e attra c tio n b etw een iron and m ag n et is explained by m eans of th e n am e m agnetism . W e m u st therefore firmly insist th a t in th e organic n atu ral sciences, an d th u s also in botany, abso­ lutely n o th in g has yet b ee n explained an d th e en tire field is still op en to investiga­ tio n as long as we have n o t succeeded in reducing th e p h en o m en a to physical and chem ical law s.”252 Sim ilar categorical denial of scientific legitim acy to th e co n cep t of vital force was expressed in 1844 by O tto K ohlrausch in his book-length cri­ tiq u e of L iebig’s A n im a l C hem istry: “A t th e m o m e n t th e ch e m ists’ attack is p rin ­ cipally d irected against th e vital force as it stands in th e physiological sense. T his is a weak fortress th a t will soon cap itu late. Physiology will soon recognize th a t a vital force described as th e sole cause of th e m o st diverse effects is an absurdity [U nding] th a t m ay n o t c o n tin u e to exist in its science u n d e r this or a sim ilar d efin itio n .”253 F rom 1844 on Valentin also rejected as o u tm o d ed any appeal to a vital force: such a co n c ep t is only a verbal expression to cover our ignorance, and falsely separates organic from inorganic p h en o m en a .254 Vital p h en o m en a are to be explained n o t in term s of peculiar vital forces, b u t in term s of th e co m m o n phys­ icochem ical forces working w ithin th e co n strain ts of a divinely ordained an d selfp erp e tu a tin g organization. W e have already en c o u n te red C arl Vogt’s rejection of th e vital force (in c o n ju n ctio n w ith th e explanation of anim al h eat) as no longer having any scientific value. For Vogt th e vital force represented an o u tm o d ed and discred ited era of physiological thinking w hen life was special and m ysterious, w hereas th e new physiology seeks to explain vital p h en o m en a in term s of an alo ­ gous inorganic p h en o m en a: only in th a t way will it m ake progress.255 Nowadays th e n o tio n of a vital force is “ridiculous.”256 By th e m id-1840s th e discrediting of th e vital force in G erm any was alm ost co m p lete, certainly am ong those who id en ­ tified them selves w ith th e grow ing physicalist m o v em en t in physiology.

One of the m ost prom inent figures to consider the role and legitimacy of the vital force during the late 1830s and early 1840s was Justus Liebig. He is, however, a difficult figure to come to terms with since many of his expressed views are mutually contradictory. Although I will not attem pt to identify the ‘real’ Liebig behind his variable words and opportunistic positions, some coherence can be found if one makes allowance for the different polemical purposes his writings spoke to and for the development of his ideas over tim e. Basically, Liebig never questioned the need to assume the agency of a vital force in protecting the organ­ ism against the multifarious influences of the environm ent that work to destroy the integrity of its complex chemical constituents. The extent to which a vital force is needed for the synthesis of those complex compounds was less clear. In part, at least, Liebig shared the growing conviction of contemporary chemists that there is no defensible distinction in principle between inorganic and organic com­ pounds, that chemists could look forward to increasing success in artificially syn­ thesizing substances produced by living things. Some of Liebig’s pronouncem ents echoed the ambivalence of people like Tiedem ann7 the early Berzelius, and Lehm ann7 who spoke simultaneously both for the de facto necessity of the vital force as a real agency of change and for its emptiness as a scientific explanation. Liebig’s statem ents over tim e also reflect the changing context of debate within the scientific community, in that Liebig became concerned with dissociating him ­ self from the strident materialism that had been gaining ever more support since around 184 0.257 It is very possible, too, that it was at least in part Mayer’s reading of Liebig’s works of 1842 that prompted him to rethink his own tacit acceptance of the possibility of the creation of force in organic systems. In 1840 Liebig began explicitly and extensively to address the Lebenskraft issue. In his highly polemical essay, “On the State of Chemistry in Prussia,” Liebig seemed to imply th at the recent progress of chemistry left no room for the opera­ tion of an unintelligible special vital force. Urea, allantoin, formic acid, and a num ber of other substances are, he said, products of vital processes. He asked rhetorically: “Is it not strange that the occult vital force that produced them — this conceptually wholly incomprehensible activity— can be replaced by quite ordi­ nary chemical forces? T hat absolutely identical effects can be produced with them ?”258 The issues broached here in passing were expounded at great length in his Organic Chemistry in Its Application to Agriculture and Physiology— the socalled Agricultural Chemistry— m uch of which had appeared earlier that year (1840) in French translation as the long introduction to his Treatise on Organic Chemistry. If on the one hand he identified the very subject m atter of organic chemistry as “the substances that are produced in the organs [of the body] by the action of the vital force [force vitale], and the decompositions they undergo under the influence o f other substances,”259 on the other hand he scorned those physiol­ ogists who reject chemistry and who instead “attribute to the vital force what they cannot understand, what they cannot explain.”260 After taking one of his usual grandly unspecific swipes at “die deutsche Naturphilosophie” as responsible for the allegedly sorry state of German science during the preceding decades, Liebig ridiculed the recourse some took to a vital force as the ultim ate explanation for

obscure organic p h en o m en a. T h e position h e attacked resem bles th a t of Berzelius in 1810: As soon as physiologists encounter the mysterious vital force in a phenom enon, they renounce their senses and capabilities; the eye, the understanding, judgm ent and reflection— everything is crippled as soon as one declares a phenom enon to be incom ­ prehensible. Before this ultim ate cause there occur a m ultitude of last causes. From the ring where the chain begins up to us there is still a m ultitude of unknown links. Are these links supposed to remain im perceptible to the hum an intellect, which has investi­ gated the laws of m otion of the heavenly bodies [even though] only a single organ instructs it of their existence, to the intellect that has so many other aids at its disposal on our terrestrial globe?261

T h e in te n t of L iebig’s criticism of vital forces here seem s to have b een twofold. First, he w ished to claim for chem ists th e com petency to deal w ith certain p h e­ n o m en a of life w hich, h e alleged, physiologists h ad in th eir ignorant in co m p e­ ten ce assigned to an intrinsically unknow able agency. S econd, even th o u g h he him self (elsewhere) invoked a vital force as th e cause of certain essential vital p h en o m en a, he believed th a t physiologists had acted hastily in rem oving too m any of th ese p h en o m en a from th e purview of chem ical analysis. If we can n o t know th e first cause at th e h ead of th e causal chain, th e n a t least we can be assured th a t m o st p h en o m en a here on ea rth are d u e to secondary causes q u ite w ithin our (i.e., ch e m ists’) capabilities to discover. T h e organism , Liebig said, does n o t cre­ ate m atter, b u t only transform s th e n u trie n ts it takes in; w hatever we m ig h t call th e cause of such tran sfo rm atio n — vital force, elevated tem p eratu re, light, galva­ nism , or w hatever— we can b e sure th a t th e process itself is purely chem ical and h en ce accessible to our u n d erstan d in g .262 N ot surprisingly, a n o th er of Liebig’s ap p a ren t co n tem p tu o u s dism issals of the co n cep t of vital force cam e in th e context of his criticism of those such as the followers of S am uel H a h n e m a n n ’s h o m eo p ath ic m edicine, who do n o t u n d er­ stan d th e tru e ch aracter of natural science: “It annoys th e m and th eir ilk th a t the tru th is so sim ple, although they ca n n o t succeed in tu rn in g it to practical account desp ite great effort, therefore they present us w ith th e m o st im possible views and create for them selves in the words vital force a w onderful th in g w ith w hich they explain all th e p h en o m en a th ey do n o t un d erstan d . W ith a com pletely incom pre­ hensible in d efinite som ething one explains everything th a t is n o t co m p reh en si­ ble!”263 If Liebig’s words here echoed th e m ethodological criticism s of M agendie, Elsasser, Schw ann, th e later Berzelius, Sim on, and Schleiden, h e never seem ed to ap p reciate th a t they to ld equally well against his ow n vague notions of an active vital force. Liebig’s vital force, like everybody else’s, was a cover for p h en o m en a he could n o t otherw ise explain. Aside from such strid en t posturing, however, Liebig m ad e regular and m atterof-fact use of th e co n cep t of vital force. In fact, during th e 1840s h e was its m ost influential defen d er am ong first-rank G erm an physical scientists— a defense all th e m ore significant w hen one considers th a t by 1839 contem poraries such as

Berzelius, M agendie, and Schw ann had, in various b u t m utually reinforcing ways, already urged th e exclusion of th e vital force from science, and th a t m any others would join th eir ranks in th e course of th e ensuing decade. Vance Hall m aintained th a t Liebig’s Agricultural Chemistry assigned th e vital force two different functions: alongside its regulation of ordinary chem ical forces “in such a m an n er th a t characteristically vital phenom ena, like reproduction, could occur,” it was also “responsible for the forms which seem ed to characterize living system s.”264 Indeed, for th e m ost part Liebig treated the vital force in this work prim arily as th e cause th a t regulates organic chem ical transform ations (Metamorphosen) .265 Som etim es he spoke of it as if it were an abstract controlling agency: “T h e vital force, in its distinctive m anifestations, makes use of particular instru m en ts, for every function a particular organ.”266 H e also identified it as “the capability in herent in every individual organ of regenerating itself at every m o­ m e n t.”267 As Liebig wrote, T h e con cep t of life includes along w ith reproduction still another con cep t, nam ely that of activity by m eans o f a determ in ate form , o f creation and generation in a deter­ m in ate form . O n e will b e in a position to produce th e co n stitu en ts of a m u scle fiber, skin, hair, etc., by m eans o f ch em ical forces; h u t n o hair, n o m u scle fiber, no cell can be form ed by th em . T h e production of organs, th e collaboration o f an apparatus o f organs, their capability of regenerating ou t o f th e foods presented n o t on ly their own con stitu en ts, b ut them selves [with] th e form , co n stitu tio n , and w ith all their proper­ ties— this is the character o f organic life, this form of reproduction is in d ep en d en t of th e chem ical forces. T h e ch em ical forces are subject to th e im percep tible cause by m eans of w hich this form is determ ined; it itself, this cause, w e only have know ledge o f its ex isten ce by m eans of th e distinctive p h en om en a it produces; we investigate its laws like th o se of th e other causes that bring about m o tio n and changes. T h e ch em ical forces are th e servants o f this cause just as th ey are servants o f e le c ­ tricity, heat, a m ech an ical m o tio n , im pact, and friction; th ey undergo through th ese latter a change in direction, an increase or decrease in their intensity, a com p lete neutralization [A ufh ebu n g], or a total reversal o f their operation. It is this in flu en ce and no other that th e vital force exerts on th e chem ical forces; b u t everywhere com b in ation and separation take place, chem ical affinity and co h e­ sion are active. W e know th e vital force only through th e d istin ctive form of its to o ls, through organs that are its carriers.268

T hese two conceptions of th e function of th e (singular) vital force correspond to two classes of ph enom ena w hich T iedem ann believed were under th e direction of (plural) vital forces: the first is essentially identical to T ied em an n ’s reliance on such forces to explain th e relatively greater com plexity of organic com pounds as com pared to inorganic; th e second is close to his understanding of th e regulation of processes of generation, developm ent, and growth. N ot surprisingly, th e anato­ m ist and physiologist T iedem ann was more concerned with such goal-directed ‘m acro’ processes, th e chem ist Liebig at m ost and only in passing w ith th e general

form of organs, w hich were of in terest to him prim arily as sites of p ro d u c tio n of organic com pounds. B oth T ied e m a n n a n d Liebig, however, assigned still a third fu n ctio n to th e vital force(s): th e preservation of still-living vegetable and anim al m a tte r from d eco m ­ p o sition, from th e processes of fe rm en tatio n , p u trefactio n , and decay it in elu cta­ bly undergoes once it is outside th e actio n of th o se vital forces.269 L iebig’s co ncep­ tion recalls his im age of respiration as th e b o d y ’s struggle against the destructive force of atm o sp h eric oxygen: “It is th e vital force th a t opposes to th e incessant action of th e atm o sphere, hum idity, and tem p eratu re on th e organism a resis­ tan ce th a t is up to a certain point invincible; it is th e in cessant leveling [Ausgleichung], it is th e co n stan t renewal of these activities w hich m ain tain s m otion, w hich m ain tain s life.”270 O n ce rem oved from th e p ro tectio n of th e vital force, organic co m p o u n d s are capable of preserving th e ir form an d c o n stitu tio n “only as a result of th e power of in ertia”; they are subject to im m a n e n t d isin teg ratio n upon th e action of th e least external influence.271 In accordance w ith his antagonistic co n cep tio n of th e vital force, Liebig claim ed th a t the state of h ea lth of th e body and th e effect of any given substance on it are d eterm in e d in large part by the relative balance betw een th e Lebenskraft and th e chemische Kraft of external agencies.272 In a later work, in which he criticized H e n le ’s and o th e rs’ conception of stim uli as agencies necessary for th e eliciting of particular organic functions, Liebig d efen d ed a conception of th e organism as always active, n o t m erely react­ ing to external stim u li.275 Such a view was of a piece w ith his con cep tio n of an active vital force constantly effecting chem ical tran sfo rm atio n s an d resisting forces of decay. As he said in a m ajor an tim aterialistic address of 1856, “O n Inor­ ganic N atu re an d O rganic Life”: “T h e inorganic forces forever create only th a t w hich is inorganic; by m eans of a higher force at work in th e living body, one whose servants are th e inorganic forces, there com es in to bein g th e organic, dis­ tinctively form ed m a tte r d ifferent from th e crystal an d endow ed w ith vital proper­ ties.”274 In previous sections of this ch a p te r we en c o u n te red L iebig’s 1841 paper on “T h e Vital Process in th e A nim al, an d th e A tm o sp h ere” as a forceful advocate of a som ew hat idiosyncratic oxygen theory of anim al h e a t an d of th e m ore general p o sition th a t all vital functions d ep en d on chem ical processes of m aterial ex­ change. N evertheless, it, too, posited th e existence o f a vital force in no u n certain term s. T h e article began: In th e anim al egg, in th e seed o f a p lan t w e recogn ize a remarkable activity, a cau se of increase in m ass, o f th e rep len ish m en t o f sp en t m aterial, a force in th e sta te of rest. T h e static m o m e n t o f th is force is d estroyed [aufgehoben] by external c o n d itio n s, fertilization , and th e presen ce of h u m id ity and air; th e force th a t passes over in to m o tio n m an ifests itself in a series o f form ation s [Formbildungen] th a t, even if occa­ sionally en clo sed by straight lin es, are n ev erth eless far rem oved from g eo m etrical shapes such as w e observe w ith crystallizing m inerals. T h is force is called vital force? 13

H ere th e vital force was responsible for th e growing organism ’s increase in m ass (a newly iden tified fu nction) a n d its developm ental d ifferentiation. H ere Liebig was

co n c e rn e d to e m p h a siz e its difference from all o th e r (inorganic) forces. H e called th e vital force an in d e p e n d e n tly ex istin g force (eine filr sich bestehende K ra ft ) , a n d in siste d “th a t all p h e n o m e n a in th e org an ism of p la n ts a n d th e a n im al m u s t b e ascrib ed to an en tirely d istin c tiv e cau se w holly d iffe re n t in its m a n ife sta tio n s fro m all o th e r cau ses th a t d e te rm in e ch an g es o f s ta te o r m o tio n s.”276 T h is article, la te r in c o rp o ra te d a lm o st u n c h a n g e d in to his A n im a l C hem istry, also c o n ta in e d o n e of L ieb ig ’s few d iscu ssio n s of m in d (C eist) and its essen tial d ifferen ce fro m th e “v e g e ta tiv e ” vital force. T h e m in d can in flu en c e only th e rate of th e v ital processes, w h ich for th e m o st p a rt— a n d in p lan ts a n d n o n h u m a n an im als perforce e n tire ly — tak e place in d e p e n d e n tly of th e m in d . A lth o u g h m u c h less e la b o ra te d , L ieb ig ’s views recall th o se of A u te n rie th a n d T ie d e m a n n an d th e tra d itio n a l d istin c tio n s b e tw e e n sen sib ility a n d irritability, a n im u s an d anim a: T h e p h en om en a o f higher psychic life (geistiges Leben] can n ot, in th e present state of science, be reduced to their im m ed ia te, m u ch less to their u ltim ate, causes; we do n ot know anything m ore than th at they are present. W e ascribe th em to an im m a te­ rial activity, m ore precisely— insofar as its m an ifestation s find th em selves bound to m atter— to a force that is w holly different from , and has n o th in g in co m m o n w ith, the vital force. As cannot be d en ied , this d istin ctive force exerts a certain in flu en ce on th e vegeta­ tive vital activity, sim ilar to the way in w hich this happens w ith oth er im m aterial powers, w ith light, electricity, h ea t, and m agn etism , b u t th is in flu en ce is n o t o f a determ inative nature, rather it m an ifests itself only as an acceleration, disturbance, or retardation o f the vegetative vital processes; in an entirely similar fashion th e vegeta­ tive vital activity exerts certain effects backwards on con sciou s psychic life .277

B u t “ science h a s a d e fin ite lim it, w h ich it m u s t n o t o v e rstep ,” an d th a t lim it does n o t in c lu d e m in d or co n sc io u sn e ss.278 O c c u p a tio n w ith su ch su b jects only harm s science, w hich can g e t alo n g q u ite well by ig n o rin g th em : “T h e c o n tin u o u sly re in ­ vig o rated e n d eav o r to w ish to discover th e rela tio n sh ip of th e psyche to anim al life [die B eziehungen der Psyche z u dem anim alischen Leben] has long since retard e d th e progress o f physiology; it was a c o n tin u o u s w ithdraw al fro m th e d o m ain of science in to th e k in g d o m of fa n ta stic fo rm s.”279 T h e m in d has n o th in g to do w ith th e d e v e lo p m e n t of e ith e r em bryos or seeds. B u t if Liebig was p re p ared to exclude con scio u sn ess a n d m in d from his scien ce, if n o t y e t from his w orld, h e was n o t d isp o se d to e lim in a te th e vital force fro m either. So far th e c o n sid e ra tio n o f L iebig’s A n im a l C hem istry has c o n c e n tra te d o n th e first of its th re e m a jo r sectio n s, th e o n e e n title d “T h e C h e m ic a l Process of R espi­ ra tio n an d N u tr itio n ,” w h ich c o n siste d of m in im ally revised re p rin tin g s of two earlier jo u rn al p u b lic a tio n s. In th e b o o k ’s d ifficu lt th ird se ctio n , “T h e P h e n o m e n a of M o tio n in th e A n im al O rg a n ism ,” L ieb ig p re se n te d a radically rew orked in te r­ p re ta tio n of th e n a tu re an d fu n c tio n o f th e vital force. W h e re before h e h a d b e e n co n c e rn e d to e m p h a siz e th e d ifferen ces b e tw e e n th e vital force a n d all o th e r forces, h e re h is ag en d a was to a ssim ila te as far as possible th e fo rm e r to th e latter. W h e re previously th e vital force h a d served to d ire ct th e synthesis of com plex organic c o m p o u n d s, to d e te rm in e th e c h a ra c teristic form s of organism s, an d to

preserve them from destructive external influences, here the emphasis was on its role in increasing the organism ’s body mass and in affording resistance against external agencies. Although Liebig did not now dwell on the still-accepted role of the vital force in synthesizing organic com pounds, his overriding concern with establishing its affinities with chemical forces w ent hand in hand with his total exclusion of its more developm ental and form -determ ining aspects. W hereas the first section of the book argued overwhelmingly— if, to be sure, with a few contra­ dictions— th at the two essential and characteristic functions of the animal organ­ ism, the production of heat and m otion, depend on underlying processes of m ate­ rial exchange, the third section argued primarily— if, to be sure, with even more contradictions!— that the vital force itself is the ultim ate cause of the organism ’s production of m echanical effects. (H eat he still assigned to the chemical process of oxidation.) As he wrote: “W e are acquainted with only one source of motive force in the organism of the animal, and this source is the same cause th at deter­ mines the increase in mass of anim ated body parts and th a t gives them the ability to resist external actions; it is the vital force.”280 Earlier his analogies had been with the steam engine and the voltaic pile; now he likened the vital force to chem istry’s peculiar catalytic force, which seems capa­ ble of producing effects indefinitely w ithout any dim inution of the causative agent. T he slogan th at no force or activity can arise out of nothing belonged to the first section, not the third. Still another innovation was Liebig’s weak attem p t to elaborate a pseudotechnical set of concepts (Kraftmoment and Bewegungsmom ent), which, he hoped, would further cem ent the connections betw een vital and physicochemical forces. Given the content of his book and the tim ing of its publi­ cation, it is not impossible that Liebig was at least in part prom pted to undertake a more general analysis of force in response to M ayer’s work, which he had re­ ceived and accepted for his Annalen in April 1842, and about which he m ight also have known through his correspondence w ith Philipp G ustav Jolly, the professor of physics at Heidelberg with whom Mayer had discussed his work around Novem­ ber 1841.281 Examined m ore closely, this third section of Liebig’s Animal Chemistry is itself not a unified piece. T he first and longer of its two major subsections, designated only by the Roman num erals I and II, contains more or less the views sketched in the preceding paragraph; the second is closer to Liebig’s earlier writings with re­ spect to the im portance of Stoffwechsel.282 Although Liebig expressly claimed that his new views were “necessary conclusions” of those developed in the book’s first section,283 I have not been able to resolve the apparently glaring contradictions betw een them . It should be noted th at Liebig faced a real dilemma: how, now, to dem onstrate the close affinities between the vital and other forces while at the same tim e preserving the form er’s privileged irreducible (and higher) status. Ex­ acerbating Liebig’s problems, and ours in understanding him, was the fact that, despite m uch talk about causality, in practice he regularly obscured the question of whether the organism’s chemical activities are the cause, the effect, or the concom itant of its vital activities.284 Liebig declared at the outset th at his conclusions with respect to “the nature and essence of the distinctive cause . . . which m ust be regarded as the ultim ate

basis [letzter G rund] of the phenom ena th a t characterize anim al and plant life” would lose th eir significance if it could be proven “th a t th e cause of vital activity has, in its m anifestations, nothing in com m on w ith other known causes th a t bring ab o u t m o tio n or changes in th e form and co n stitu tio n of m atter.”28’ A lthough a distinctive force, th e vital force’s effects m u st still be in accord with the sam e general laws of resistance and m otion th a t govern th e solar system and bring ab o u t m aterial change. T h e principal physiological function of th e vital force is (here) to co u n teract the forces of attraction betw een the m olecules of th e n u tri­ en t m atter and redirect their chem ical forces toward th e production of organic substances. T h e unifying conceptualization of force th a t Liebig advanced was to see forces as agencies which b o th cause and resist m otion. W ith respect to th e force of gravity, for exam ple, one m u st distinguish th e pressure (Druck) exerted by a stone resting on a table from the m otion it acquires in free fall.286 Liebig called the intensity of th e gravitational force b o th pressure an d m otive force; its effect in causing a body to fall was proportional to w hat he term ed the K raftm om ent7 the product of th e “pressure” and th e tim e of fall. T h e poorly defined Bewegungsgrofie considered also th e m ass of th e falling body, and was equal to th e product of eith er th e m ass and the K raftm om ent or the mass and velocity of the body. T he Bewegungsmoment, finally, m easured th e effect of th e force in term s no t of elapsed tim e b u t of distance m oved, and was effectively w hat we w ould call work. Liebig concluded: Moments o f force or moments of motion are accordingly expressions or measures in mechanics for effects of force that are related to a velocity acquired in a given time or to a given space; in this sense they can be applied to the effects of all other causes of change in motion, form and constitution . . . . Accordingly, every force manifests itself in matter as resistance to external causes of changes in place, form, and constitution; it manifests itself as motion-generating force when no resistances oppose it or in the overcoming of resistances. We observe both manifestations of activity in the force that gives animated body parts their distinctive properties.287 Insofar as th e vital force resem bles other forces— at least in term s of its suscep­ tibility to analysis in analogous term s— it m ust have a certain Bewegungsmoment, in which case “we know th a t this m o m en t of m otion of th e vital force is available [verwendbar] in an anim ated body part to im part m otion to resting substances (to bring ab out decom position, to neutralize resistances), and if in its m anifestations th e vital force behaves like o th er forces, th e n this m o m en t of m otion m u st be able to b e com m u n icated or propagated by substances th a t in and of them selves do n o t neutralize its free m anifestation by m eans of an opposing activity.”288 T he analogy he had in m ind was betw een th e propagation of galvanic electricity th rough th e connecting wire, which h e believed offered no resistance to the cur­ rent, and th e propagation of m otive force via th e nerves from one part of th e body to another.289 Liebig m ade contradictory statem ents as to w hether or no t m otion can be an n ihilated w ithout effect— and u n d er “effects” he included such non-

energetic factors as th e d e n t m ad e by a falling body w hen it is stopped by a piece of wood. His exam ple of th e com ing to rest of tw o colliding inelastic bodies and his im age of forces opposing each o th e r in a state of dynam ic equilibrium , and th u s canceling o u t each o th e r’s effect, leave th e strong im pression th a t there are co m m o n con d itio n s u n d er w hich forces can b e d estro y ed .290 O n e of th e m ost im p o rta n t sim ilarities betw een vital and chem ical forces was th a t they b o th a c t only upon co n tac t or at im m easurably small d istan ce s.291 In choosing to liken vital forces to chem ical ones, however, Liebig singled o u t a special class of th e latter, w hich included those th a t Berzelius had identified six years earlier as “catalytic” forces, although Liebig did n o t use th a t term here: “T ransform ations— or, if you will, p h en o m en a of m o tio n — can . . . b e b ro u g h t ab o u t by th e free and available chem ical force active in an o th er chem ical co m b i­ n atio n , an d in d eed w ith o u t its m an ifestatio n being exhausted or n eu tralized by resistances.”292 Liebig’s exam ples were th e use of sulfuric acid in th e pro d u ctio n of grape sugar from cane sugar an d of glucose from starch and water. H e reiterated th e o u tstan d in g distinguishing characteristic of th ese u n iq u e forces: “E ntirely dif­ feren t from th e m an ifestatio n of th e so-called m echanical forces, we have recog­ n ized in th e chem ical forces causes of p h en o m en a of m o tio n , of changes in form and co n stitu tio n , w ith o u t perceptible exhaustion of th e force by w hich they were p roduced; b u t th e reason [Grund] for th e co n tin u in g m an ifestatio n of activity always rem ains th e sam e, it is th e lack of an opposing activity (a resistance) which is capable of n eu tralizing or balancing it o u t.”293 As close as Liebig som etim es cam e to an ap p aren t intu itiv e grasp of th e conservation of energy, on m any other occasions h e show ed him self to be q u ite oblivious to th e im plications of any such principle. H ere, of course, his goal was to assim ilate th e vital force to chem ical forces, am ong w hich th e experim entally dem onstrable (if conceptually murky) catalytic force ex h ibited th e closest affinities. In a passage co n tin u in g th e one just q u o ted , Liebig w ent o n to offer an in ter­ p retatio n of th e vital force in term s of th e arrangem ent of th e elem entary particles of th e organ: Just as the manifestations of the chemical forces (the mom ent of force of a chemi­ cal compound) appear to be dependent on the particular configuration in which its elementary particles are in contact with each other, in a similar fashion experience indicates that the vital phenomena are inseparable from matter, that the manifesta­ tions of vital force in an animated body part are determined by a certain form of the carrier and by a certain configuration of its elementary particles; if we destroy [aufheben] the form or composition of the organ, then all of the vital phenomena disap­ pear. Nothing prevents us from regarding the vital force as a special property that belongs to certain material substances and becomes perceptible when their elementary parti­ cles have come together in a certain form. So conceived, the vital force unites in its manifestations all of the distinctive fea­ tures of the chemical forces and of the no less wonderful cause that we regard as the ultimate basis of the electrical phenomena.

T h e vital force does n ot m an ifest itself at in fin ite d istances like th e force o f gravity or th e m agn etic force; rather, like th e chem ical forces, it is active only on im m ed iate contact; it b ecom es perceptible through a com p lex o f m aterial parts.294

This is probably as close as Liebig ever cam e to offering w hat m ight appear to be a reductionist in terpretation of th e vital force, although his interpretive enterprise m ight also be understood as an exercise in legitim ation-via-analogy— and, as I will show presently, he soon w ent on to treat the vital force m ore like an in d ep en d en t cause sui generis. Reading this passage carefully, one notes th at Liebig only as­ serted th a t th e vital force is a m anifestation or expression (Aeufierung) of m atter having an appropriate form or configuration (Form, Ordnung, O rdnungsweise), and as such his conception of th e vital force m ight reasonably be com pared with Johannes M uller’s notion of a special force laten t in all m atter b u t only m anifest­ ing itself in appropriately configured organic m atter. According to Liebig’s crude theory, the various parts of th e body, in particular th e m uscles, possess a certain quantity of vital force, a portion of which goes to preserve th e equilibrium of their substance against forces seeking their destruc­ tio n — in particular, oxygen. W h e n som e of th a t vital force is expended in the perform ance of m echanical effects, th a t part of th e body is no longer capable of co u n teracting th e destructive chem ical force of th e oxygen circulating through­ out th e body in th e blood. T h e result is th a t a portion of the once-living tissue com bines with oxygen to form lifeless com pounds, a process Liebig term ed Stoffw echsel.29> T hus this exchange of m a tte r was th e result of the production of anim al m otion, n o t its cause. Liebig m ade abundantly clear w hat th e underlying cause was in a passage M ayer quoted and criticized in his aptly titled Organic M otion in Its Connection w ith the Exchange o f M atter (1845): N o other con clu sion can be drawn from this very d efin ite co n n ectio n b etw een the exchange of m atter in the anim al body and th e [vital] force con su m ed by m echanical m otion s than that the vital force active or available in certain an im ated body parts is th e cause of th e m echanical effects o f th e anim al body. T h e m otive force doubtless derives from anim ated b od y parts. T h ey possessed a m o m en t of force or m o tio n that they lo st to just the degree that others have received a m o m en t o f force or m otion; they lose their capability for increase in m ass, their ability to resist external causes of disturbances. It is clear that th e u ltim ate cause, the vital force, from w hich they obtained th ese properties, has served to produce m ech an ­ ical force; it has b een con su m ed as m o tio n .296

Significantly, Liebig did n o t explicitly equate this m otion-producing vital force w ith th e chem ical forces contained in the anim al’s belebte Korpertheile. Except for a brief key phrase, th e following conclusion m ight wrongly be read as asserting a causal relationship betw een oxygen consum ed and work done in a sense opposite to the one Liebig intended: E xchange of m atter, m an ifestation o f m echanical force, and uptake o f oxygen stand in so close a con n ectio n to each other in th e anim al body that on e can put the quan­ tity o f m o tio n and the a m ou n t of transform ed an im ate m atter into o n e and th e sam e ratio w ith respect to a certain am ount o f oxygen taken up and con su m ed by the

anim al in a given tim e. For a d eterm in a te m easure o f m o tio n , for a p roportion o f v ita l force consum ed as m ech an ical force, an eq u iv a len t o f ch em ical forces b e c o m e s m a n i­ fest, i.e., an eq u ivalen t o f oxygen b e co m es a c o n stitu e n t part of th e organ th at lo st th e vital force, and an equal proportion o f th e m a tter o f this organ leaves th e b od y part in th e form o f a c o m p o u n d o f o x y g e n .297

Liebig’s principles led him to the curious conclusion that, when a large quantity of vital force is consum ed in the production of mechanical m otion, the body com pensates by slowing down the m otion of the h e a rt.298 To the obvious question, How is the continuously expended vital force replen­ ished?, Liebig gave only the sketchiest of unsatisfactory replies. Som ewhat at odds with his more usual claim th at the organism’s growth is a result of a directive and form-creating vital force was his passing suggestion th at the vital force derives from the assimilated nutrients, making it either a kind of higher-level chemical force or a latent force sui generis a la Muller: “W hen we consider th at the capabil­ ity for increase in mass has almost no lim it in the plant, and th at a hundred willow branches taken from one tree becom e a hundred trees, then one can scarcely doubt that, with the uniting of the elem ents of the food to a constituent part of the plant, to the already present m om ent of force, a new m om ent of force is added to the newly form ed part of the plant, th at w ith the increase in mass the quantity of vital force increases.”299 Liebig confessed his com plete ignorance as to the m an­ ner in which the vital force produces m echanical effects, and which will no more be able to be discovered through experim ent than the connection betw een the chemical action in a galvanic pile and the phenom ena of m otion it produces.300 Abandoning, at least for rhetorical purposes, his earlier expressed attachm ent to the m ode-of-m otion theory of heat, he here invoked the imponderable-fluid th e­ ory as another analogy-of-ignorance in defense of his protean notion of vital force: W e d o n o t know h o w an intrinsically invisible, im p on d erab le so m eth in g , h ea t, im ­ parts to certain natural su b stan ces th e capability o f exertin g th e m o st en orm ou s pres­ sure on th eir surroundings, or h o w at all th is so m e th in g is produced w h en we burn w ood or coal. It is th e sam e w ith th e vital force and th e p h e n o m e n a p resen ted by an im ate b o d ies. T heir cause is n o t ch em ica l force, n o t electricity, n o t m agn etism ; it is a force that possesses th e m ost general properties o f all cau ses o f m o tio n and o f ch a n g e in th e form and co n stitu tio n o f m atter, and [yet it is] a d istin ctiv e force b eca u se it has m a n ifestation s th at n o n e o f th e oth er forces p o ssess.301

As far as this passage goes, the vital force may for the m ost part be analogous to the usual physicochemical forces, b u t it is not identical to them . It remains a distinctive force, an eigenthiimliche Kraft. O ne’s frustration at discovering what Liebig ‘really’ believed is only heightened by his confused and contradictory discussion (in the next unnam ed subsection of the third part of his Anim al Chemistry) of the relationship betw een the vital force, am bient tem perature, food consum ption, respiration, the exchange of matter, organic m otions, growth, sleep, and age-dependent differences in the body’s

econom y of force and substance. Som etim es it seems clear th a t th e cause of the p ro d u ctio n of force is th e exchange of m atter.302 But if on one page he attrib u ted th e p roduction of anim al h e a t to processes of oxidation, on another he allowed th a t “h eat can be produced in th e anim al body w ithout any exchange of m at­ ter.”303 In th e previous subsection of his book Liebig had argued th a t th e expendi­ ture of vital force on m echanical effects exposes th e anim al’s tissues to th e d e­ structive effects of the ever-present oxygen, leading to an increased exchange of m atter; here h e argued th a t cooling a part of th e body reduces th e strength of its vital force with a sim ilar effect, and th a t th e increased exchange of m atter serves to raise th e tem p erature of the affected part. M ayer singled o u t th e following sum m ary paragraphs for citation and criticism in his 1845 book: How ever closely co n n ected th e con d ition s for the production o f heat and for the production o f force for m echanical effects m ay present th em selves to observation, the d evelop m en t of heat can by itself in n o way be regarded as th e cause o f th e m echanical effects. AU experience proves that there is in th e organism only on e source o f m echanical force, and this source is the transition o f anim ated body parts in to lifeless com pounds. T h e cause of the co n su m p tio n [of m atter in the body] is th e chem ical action o f the oxygen; its m anifestation is d ep en d en t up on a withdrawal of h eat, as well as on the em p loym en t [or expenditure (Verwendung) ] o f vital force for m echanical effects. The a ct o f consum ption is ca lled exchange o f m atter, a n d it occurs as a result o f the assim ilation o f oxygen in to the substance o f an im a te body parts; th is assim ila tio n o f oxygen only takes place when the resistance th a t the v ita l force o f a n im ate body parts opposes to the chem ical action o f the oxygen is sm aller than th is chem ical action itself, an d this weaker resistance is determ in ed by the w ith d ra w a l o f h ea t or by the em ploym ent for m echanical m otions o f the [vital] force active in the body parts.304

T h e effect on M ayer of his critical reading of Liebig’s confused physiology of the vital force will be addressed in chapter 6. M ayer’s university friend and later pro­ fessor of m edicine, C arl A ugust W underlich, ridiculed Liebig’s conception of vital force as a “com pletely abstract and m eaningless word,” an abstraction supposedly capable of opposing th e influence of a ponderable substance, oxygen.305 Liebig had n o t, in fact, clearly addressed th e question of th e ontology of th e vital force— w hether it is a property of m atter, like o ther forces; or a particular arrangem ent of th e sm allest parts of m atter; or an im ponderable substance sui generis; or an ab­ stract b u t causally active idea. T h a t Liebig him self was dissatisfied w ith his h a n ­ dling of th e vital force is suggested by th e fact th a t— perhaps in silent response to M ayer’s telling criticism s— he dropped th e long third section of his A nim al C hem ­ istry from th e third edition of 1846.306 If Liebig can b e taken as th e m ost influential spokesperson in G erm any for a vital force during th e early 1840s, th e n surely H erm ann Lotze can stand for a growing and outspoken antivitalist strain am ong G erm an scientists during th at period. Indeed, w ith th e publication in 1842 of L otze’s General Pathology and Therapy as M echanical Sciences and his fam ous Lebenskraft article at the head of

R udolph W agner's Dictionary o f Physiology in 1843, an assertive m aterialism th ru s t itself o n to th e contem porary biological stage, one w hose voice d em anded to be heard. A fter aro u n d 1842 th e vital force was a co n ten tio u s and sym bol-laden to p ic in ways th a t it h a d n o t b een only a few years earlier. T h o u g h m aterialist in th eir o rien ta tio n , L o tze’s w ritings c o n tin u ed th e trad itio n of th e m u ltifaceted “co m m o n c o n te x t” identified earlier. T h a t is, they dealt w ith th e in terco n n ected problem s of life and th e vital force and th eir relationship to nonlife an d th e nonvital forces of physics and chem istry; w ith th e soul (or m in d or will) and its relation­ ship to th e body and th e vital force; w ith th e relationship— w h eth er substantial or analogical— b etw een th e im ponderables and all th e rest; w ith spiritualist p h e­ n o m en a; w ith general issues of causality; an d w ith G od. T his was, I co n ten d , also M ayer’s broad p roblem context, an d if a self-professed m aterialist an d antivitalist like L otze could still allow for the effective creation and d estru ctio n of force ou t of n o th in g , th e n M ayer’s achievem ent looks all th e m ore im pressive, all th e less simply an expression of contem porary tendencies. At th e cen ter of L o tze’s worldview was his c o n ten tio n th a t exactly th e same laws govern b o th organic and inorganic p h enom ena: th ere are no forces special to living things. Life is “strictly speaking a su m m atio n of nonliving processes”; it belongs n o t to th e parts of th e organism b u t to “th e totality of th e processes which th e entire body produces.”507 L otze d em an d e d n o th in g less th a n “th e universal d o m in atio n [Herrschaft] of th e m echanical view point.”508 A longside such o n to ­ logical assum ptions, L otze m ain tain ed th e m ethodological principle th a t science can only treat of th e laws of n atu re as they apply to already given arrangem ents of things: science can n o t account for th e initial conditions (to use our term ) we find ourselves co n fro n ted w ith, w h eth er th e ob ject of investigation is th e solar system or a living organism . Yet it is in part on th e arrangem ent of th e p o in ts of applica­ tio n (durch die Anordnung der Angriffspunkte) th a t any actual course of physical events depends. L otze did n o t deny all difference b etw een organism s and inor­ ganic n atu re, b u t he placed th eir difference in th e com plex purposive organiza­ tion of organism s, w hich h e characterized as natural purposes (Naturzwecke) and w hose original creation he a ttrib u te d to G o d .309 As h e forcefully p u t it in his Lebenskraft article: W hat happens in the living body is not distinguished from what happens in the inanim ate physical [world] by a difference in principle in the nature and m ode of operation of the efficient forces [vollziehende Krafte], but by the arrangement of the points of application available to them , on which depends, here as everywhere in the world, the configuration of the ultim ate outcom e. T h e com ing together of the indi­ vidual masses into that determ inate arrangement out of which proceed, as m echanical results, all of the phenom ena of life is nothing accidental, but is only preserved and propagated by descent from the race. T h e com ing into b ein g [Entstehung] of an organism (at least of a higher one) is therefore never an object o f observation in such a way that it m ight be possible to dem onstrate how, in the course of the changes in the earth’s surface, chem ical elem ents m ight have com e together by chance in certain proportional quantities and under certain external circum stances in such a way that a series of vital m otions, an individual, m ight have been formed from them as an

au to m atic result. For th a t reason physiology has, in this co ntinuity in th e develop­ m e n t of the germ o u t of earlier organism s and of later organism s o ut of th e germ , its u ltim ate fact, one w hich it m u st take into consideration, and it can, as th e fust cause [Grund] of this continuously unfolding series of developm ents resulting from the process of reproduction, only assum e a creation lying beyond th e realm of natural science, b u t n o t a chance com ing in to being, even one th a t takes place according to m echanical principles. T h u s here, as in every natural science, it is only a q u estio n of deriving th e laws in accordance w ith w hich every n atu ral phen o m en o n can be de­ d uced from its presuppositions and in tu rn determ ines new ones. . . . Moreover, from the principles [G rundlagen] adduced here there follows by itself th e refutation of the objections directed against m echanical theories from a religious stan d p o in t, as if life w ould lose som eth in g of its dignity and sanctity if it were conceived to be th e result o f a m echanism . O ne forgets th a t this m echanism did n o t com e into being through its own virtue, b u t th a t th e w isdom of G od created it, and has charged it, as th e m ost reliable servant who never abandons him self to his own pleasure, with th e realization of th e ideas of natu re [Naturideen].iW

T he principal object of physiological investigation should be the processes o f m a­ terial exchange by w hich th e organism m aintains itself. L otze saw in th e exchange o f m atter “the centerpiece of th e organic m echanism , around which all the other processes of the animal econom y can be co n n ected .”311 H aving thus declared his in ten tion to regard vital functions as the result of the law bound working out of general physical laws, it is clear that L otze would have n oth in g to do w ith the notion of a vital force as cause of a special class of p h en o m ­ ena. N otin g, in his General Pathology, that th e word “force" was used in two senses— in physics as th e constantly acting cause of sim ple m otion and in engi­ neering as the capability of a m achine to perform a certain am ount of work— he argued that by “vital force” one m ust n ot understand a supposed active cause of organic m otions, but rather only a m easure o f the m echanical effects the organism produces.312 M ayer’s friend and confidant, W ilh elm Griesinger, took exception to L otze’s restriction o f th e term. As h e wrote to Mayer: You have occupied yourself w ith th e concept of force. In his— good— General Pathol­ ogy Lotze has . . . also called a tte n tio n to th e different senses this word can have in organic nature; [but] however m uch I am an o p p o n en t of th e views he com bats and in this regard entirely agree w ith him , nevertheless his view of it will n o t satisfy m e either. H e believes th a t one can speak of force (e.g., vital force} in organism s only in th e sense of m echanics, nam ely to designate th e m agnitude o f the work performed th a t arises from an entire system of masses, b u t th a t one can never so u n d erstan d a cause [i.e., as a force]. B ut I do n o t know w here he th en w ants to go w ith th e causes of th e first developm ent of th e germ .313

O n ce again it is the developm ental functions o f the vital force that seem m ost resistant to reduction to m echanical principles, even to som eone like Griesinger who otherw ise saw h im self as advocating a physicalist approach to the life sci­ ences. As we have just seen, L otze answered G riesinger’s question in his more

elab o rated Lebenskraft article, where generation was in terp re ted as th e passing on from gen eratio n to generation of a particu lar m aterial disposition. In th a t work, too, L otze su b jected th e concept of force to closer philosophical analysis, and co n clu d ed th a t force in general is a fiction, an abstraction we wrongly project into n ature: w hat we have knowlege of is only th e lawlike relations of th in g s.314 As for th e vital force, h e fu rth e r dism issed th e m isguided practice of regarding it as the unknow n cause of p h en o m en a— indeed, as th e u nitary cause of a m ultiplicity of diverse p h en o m en a— an d criticized th e related concepts of “form ative force” and “self-preservation force,” of th e alleged “forces” of sensibility, irritability, and re­ p ro d u ctio n , as providing at b est only a classification of ph en o m en a, n o t th eir ex p lan a tio n .315 Still o th er criticism s to u ch ed u p o n o th ers' false ontology of force. A ccepting th e use of th e term in physics to describe th e in h e re n t properties of things, L otze o b jected to a tte m p ts to regard force n o t only as a cause b u t also as an in d ep en ­ d ently existing entity: But th e definition w hich regards force as a cause at once brings w ith it th e error eith er th a t force is identified w ith som e su b stan ce w hose sole p roperty consists in possessing th is force, or th a t forces are regarded as distinctive existing en titie s th a t presuppose n o th in g further, b u t exist every b it as well by them selves as things. Both errors have b een ch am p io n ed by tw o fam ous m en , to m e n tio n w hose celeb rated nam es suffices to in d ic ate how necessary a th o ro u g h investigation of this co n cep tu al d efin itio n [Gedankenbestim m ung] is. T h e first error was d efend ed by T reviranus, th e second by A u te n rie th .516

Treviranus, said L otze, ta u g h t th a t a universal and inherently form less vital m a t­ te r (Lebensstoff) requires th e influence of external forces to d eterm in e its m an i­ festatio n as this or th a t specific creature. B ut if those external torces are so power­ ful, argued L otze, th e n th e supposed vital m a tte r is effectively reduced to th e statu s of ju st an o th er m aterial su b stan ce.317 C itin g th e first essay in A u te n rie th 's Views on the World o f N ature and the L ife o f the Soul, L otze o b jected to th e a u th o r’s identification of th e vital force as an in d ep en d e n t en tity analogous to th e im ponderables, th e w eightless fluids as­ su m ed to underlie th e p h en o m en a of h e a t, light, electricity, and m agnetism . For h im , th e im ponderables are e ith e r inactive weightless fluids or properties of m a t­ ter, and since forces ca n n o t exist ind ep en d en tly of m atter, th e very co n c ep t of an A u ten rieth ian vital “force” is em pty. Lotze also criticized th e pro-vital-force views expressed in H e n le’s General A natom y. As we have seen, H enle h ad distinguished th e vital force from th e forces of in an im ate n atu re in term s of th e fo rm er’s sup­ posed u n iq u e ability to propagate itself w ith o u t loss of intensity. Lotze dis­ co u n ted this alleged difference by citing th e behavior o f a physical agent, m ag n et­ ism: “D id n ’t th a t ingenious observer consider th a t exactly th e sam e th in g takes place w ith a m ag n et, whose force can b e propagated w ith o u t w eakening to m any iron rods so th a t they exhibit th e sam e polar form of ac tio n ?”318 H aving th u s accep ted th e possibility of th e m u ltip licatio n of force, Lotze w ent on to acknowl­ edge th e possibility of its d estru ctio n , too. H a d n ’t H enle fu rth er considered that,

especially for a few lower classes of anim als, the act of propagation appears to entail a fatal exhaustion of its forces? Johannes M iiller has also cfiscussed these ideas; never­ theless it appears to m e th a t one thereby em braces th e p h en o m en a altogether too grossly in an abstraction. Forces are in general n o t co m m u n icated from substance to substance in natu re, b u t only velocities and (in general) changes, or individual diffus­ ible fluids. W h a t takes place w ith th e transm ission of m agnetism we do n o t very precisely know; b u t vital p henom ena offer here, as I believe, no real difficulty at all.519

T h e act of generation, L otze said, involves n ot the transm ission of a vital force but the im position of a particular arrangement of parts in the germ, which then grows by drawing into itself th e am bient forces of inorganic nature, L otze criticized still another o f th e differences Idenle had identified betw een vital and inorganic forces, nam ely that the vital force, in surviving the material changes that take place in the living organism, cannot be regarded as merely the sum or th e product of the forces of the individual parts. Strictly speaking, Idenle may have been right, b u t the an tim ech an ist conclusion he drew was unwar­ ranted: From it [i.e., experience] we know in th e first place n o th in g at all ab o u t w h eth er an organic force has been conserved in th e exchange of th e [organism ’s] co n stitu e n t parts, b u t only th a t th e form of th e body and th e sum o f its vital phenom ena do n o t change markedly during this e x c h an g e .. . . T h a t th e vital force should be th e sum or th e product of th e forces of th e particles— surely no one dem ands th a t; rath er it is only supposed to be som e function or o th e r of them . W h e n we recall th a t even th e diago­ nal of th e parallelogram of forces only translates into th e sum of th e tw o com ponent forces [Seitenkrafte] in the single case w hen b o th co m p o n en t forces have one and the sam e direction, . . . th en we naturally only require th a t th e vital force vary in some, perhaps very com plicated functional form proportional to th e individual forces. S om eone who w ished to suppose here th a t it grew in accordance w ith th e sum of th e m olecules, and thus th e w eight of th e body, would n o t be proceeding m ore accurately th an som eone who wished to d eterm in e th e resu ltan t of two co m p o n en t forces merely from their velocities and w ithout considering th e angle th ey form .520

T hus in choosing analogies to refute H en le’s b elief that the organic force follows laws different from those o f the normal physical forces— analogies with the pro­ cess of m agnetization and with the com bination of forces in the parallelogram of forces o f m ech anics— L o tz e d e m o n stra te d h o w far even a dedicated m aterialist reductionist could b e from an intuitive notion of th e conservation of energy, esp e­ cially w hen th e con cep t of force still em braced N ew tonian forces, velocities, and a variety of crudely conceptualized natural powers. His exam ple reminds us, too, of the exten t to which everyone’s thinking in these m atters revolved around the exploitation o f favored analogies. M ayer’s dogged and ultim ately successful pur­ suit of a coherent understanding of force seem s all the m ore im pressive by com ­ parison. A m on g the topics dealt with in L o tze’s G eneral Pathology was the relationship b etw een the soul and th e body, b etw een ideas (either an individual’s or ‘Platonic’)

and m atter. Ideas by them selves can never fun ctio n as active forces: “T h e idea has no force of lim bs to m ove m asses; if this is to h a p p e n th ere m u st exist a system of m asses w hich is already ordered in accordance w ith its laws and w hich, therefore, [even] acting purely m echanically, nevertheless produces th e result th a t, as prede­ term in ed and necessarily existing, corresponds to th e idea of life. It follows from this th a t ideal relationships never explain th e m odes of realization of som e p h e ­ n o m e n o n .”321 T h e one huge exception to this principle, Lotze later n o ted , was th e original creation of th e world and all its physical arrangem ents and organic forms in accordance w ith th e divine idea; however, such an ideal influence is n o t a possi­ ble o b ject of h u m a n experience, and can th u s be excluded from co n sideration by science, w hich has to do only w ith th e com pletely m echanical processes th a t gov­ ern th e working o u t of th e system th u s established. T h e problem is th a t it cer­ tainly appears in th e organic realm — w ith us, a t least— th a t ideas do indeed effect changes in th e m aterial world. How is th a t to be reconciled w ith “our m echanical way of regarding th in g s”?322 L o tze’s response to this dilem m a was to change the venue for its so lution from th e natural sciences to m etaphysics: h e o p ted for occa­ sionalism .323 A pparent influences in tw o directions h ad to be considered. A fter laying o u t his occasionalist in te rp re ta tio n of th e relationship betw een physical m o tio n s an d our ideas (VorsteIlungen), he broached the q u estio n of th e con n ectio n betw een our ideas an d th e m o tions they appear to cause: T he other incomparably more difficult point is the com m encem ent of corporeal m o­ tion under the influence of the m ind. T he m echanical theory dem ands in all of its other applications that for the initial excitation of a m otion there be given either a com m unication of velocity on the part of another moved m ass or the elim ination of the obstacles that oppose the free action of the given forces. T he latter can itself not occur w ithout prior physical m otions. T he well-known principle that the quantity of m otion in the universe m ust always be the same stands opposed to every free com ­ m encem ent of a corporeal m otion by m eans of ideal influences, which would indeed continuously change that sum of m otion .324

L otze in terp re ted this line of reasoning as leading to an unacceptable denial of freedom of th e will. His solution represented n o th in g less th a n a denial of one of his fu n d a m e n tal principles, th e id en tity of th e laws governing b o th th e organic and inorganic realm s: “T here is . . . no o th e r assu m p tio n necessary th a n th a t of a physical force in th e substance of th e central organ w hose in ten sity is variable, an d in such a way th a t its variations correspond to th e ideal events in th e m in d in accordance w ith certain general arran g em en ts.”325 H e assigned th e q u estio n of th e acceptability of such a variable Kraft to m etaphysics— w hich, h e found, has no o b jection to it. So m uch (again) for th e conservation of energy! H e was well aware th a t th is m aneuver was ta n ta m o u n t to an “exclusion of th e co n cep t of causality,” and he took refuge b e h in d th e ostensible n eed for a special force to ac co u n t for a special set of circum stances: “W e are forced to assum e a variability of force only by th e influence of th e m in d ,” by th e “influence of th e ideal on th e m aterial.”326 L otze did n o t use th e term variable force in his Lebenskraft article. H e instead lo cated th e distinctiveness of th e organism , considered as a m ach in e (Mechanis-

mus), in th e fact th a t it possesses a “principle of im m an en t disturbances which follow no m athem atical law of their strength or recurrence at all,” a principle th a t endows th e organism w ith th e capability for “an absolutely new initiation of m e­ chanical m o tio n .”327 In th a t article, too, he did no t give such explicit or u nquali­ fied acceptance of occasionalism , b u t instead toyed rather inconclusively w ith the notion th a t th e soul m ight be able to affect the body insofar as b o th are “sub­ stances.”328 Accordingly, he was also willing to en tertain at least the possibility th a t one person’s soul m ight be able to affect a n o th e r’s directly, or even to affect in an im ate objects, as in alleged cases of w hat was th e n called, q u ite generally, “anim al m agnetism .” T hough skeptical about the reality of such phenom ena, he refused to rule o u t th eir possibility on a priori grounds. Lotze had expressed a sim ilar judgm ent in his earlier work, though he was m ore dismissive there of the possibility of certain spiritualist phenom ena such as th e displacem ent of one of th e senses, th e su b stitu tio n (Vicariren) of one organ for another, or th e m ove­ m e n t of an external physical object.329 L otze’s views on these difficult m atters were clearly in flux. (The last section of this ch ap ter contains a sum m ary of this section’s findings w ith respect to th e vital force and its significance as part of th e background to M ayer’s form ulation of a concept of an autonom ous, uncreatable, and inde­ structible force.)

3 L e a d in g A n a l o g ie s

As we saw in ch apter 2, the search for valid analogies played a key role in th e developm ent of M ayer’s ideas. Indeed, th e very concept of force and its character­ istics were b o th arrived at and presented in term s of th e central analogy betw een uncreatable, indestructible, im ponderable force and uncreatable, indestructible, ponderable matter. T his section will first exam ine th e rich analogies elaborated by contem porary G erm an physiologists— th e chief authors in M ayer’s presum ed in­ tellectual background— w ith respect to th e relationship betw een th e im ponder­ ables, vital force, and th e soul. In A u ten rieth ’s hands, this analogy was extended to include parallel (if n o t always evenhanded) trea tm e n t b o th of ponderable m a t­ ter and of gravitational attraction and m otion at opposite ends of a rough spec­ tru m of entities th at em braced the im ponderables, vital force, and the soul. As was th e case w ith authors’ handling of th e vital force alone, such discussions inevitably involved reflection on problem s of real or apparent creation and destruction. Similarly im p o rtan t to th e course of M ayer’s thinking were the im age of the organism as a m achine and the analogy betw een th e solar system and living organ­ isms. N ot th a t M ayer necessarily believed th a t th e organism is a m achine— he was, after all, fervently opposed to th e reductionist m aterialism of m id and late nin eteen th -cen tu ry G erm any— b u t in order to analyze its m aterial and energetic relationships he th o u g h t quite naturally of the organism as a m achine. T h a t m e t­ aphor, too, was widespread in th e scientific literature w ith which M ayer was likely familiar, and it was a m etaphor freely em ployed by people who were very far from regarding organisms to be m achines.

O ne of th e m o st perplexing features of M ayer’s work was his application of th e parallelogram of forces to central force m otions, leading h im to th e conclusion th a t force is g en erated in th e sun. T h e sources of those notions of force and m o tio n in th e co ntem porary physics literatu re will b e explored in c h a p te r 4. H ere I will presen t evidence th a t M ayer’s conclusion was facilitated by th e w idespread practice of regarding th e solar system as a kind of divinely ordered “organism .” A lthough th ere is no evidence th a t Mayer, early on, p aid any special a tte n tio n to th e co n cep t of a m otio n -p ro d u cin g vital force per se, he nevertheless did n o t h esitate to e n te rta in th e possibility th a t all “organism s” m ig h t co n tain w ithin them selves th e ability to create (th o u g h n o t to destroy) force, once he h ad co n ­ vinced h im self th a t force is created in th e solar system as a result of th e gravita­ tional in teractio n betw een planets an d sun. T h e ready availability of th e m etap h o r of solar-system -as-organism enabled h im tem porarily to bracket those system s to g e th e r as acceptable exceptions to th e laws he believed held for th e purely m echanical system s of in an im ate nature. M ayer’s th in k in g was shaped at every tu rn by th e im ages an d usages he en c o u n tered all around him . 3.1 The R elationship between the Imponderables, V ita l Force, and the Soul So in tim ately did G erm an physiologists of th e 1830s relate th e concepts of vital force an d soul to th a t of th e im ponderables th a t it was im possible n o t to an tici­ p ate th o se co n n ections in th e preceding section. T h e issue was of such c o n tem p o ­ rary significance, however, and was so significant an aspect of th e conceptual back­ g ro u nd to M ayer’s creation of a new concept of force, th a t it w arrants full and separate tre a tm e n t. It m u st constantly be borne in m in d th a t if M ayer was to discover th e conservation of energy— at least in th e form in w hich he co n c ep tu al­ ized it— h e first h ad to ‘discover’ an en tity ab o u t w hose conservation he could ask p o in ted q uestions. It is m y co n te n tio n th a t th e identification of such a new entity, M ayer’s “force,” took place w ithin th e co n tex t of th e issues to be exam ined in this section. I believe th a t a crystallization of m eanin g w ith respect to force could have taken place only if M ayer h ad already b een actively aware of a rich co n tex t of issues an d associations w ithin w hich a relatively sm all change of perspective could have b ro u g h t ab o u t a m ajor reconceptualization of th e n a tu re of force and its ontological relationship to th e im ponderables. A lthough th e physiological “com ­ m on c o n te x t” d ealt centrally w ith th e vital force and th e soul, it is well to recall th a t Mayer, in his earliest papers, specifically lim ited th e scope of his ideas to th e inorganic realm ; th e possibility, in d eed th e positive belief, th a t force can b e cre­ ated in organic system s was an idea M ayer c o n tin u ed to hold until at least th e second h alf of 1842. A lthough th ese issues were widely explored in th e physiological literature, one au th o r above all others m ade th e m th e subject of an am azingly ram ified and ex ten d ed discussion: Johann H einrich F erdinand A u ten rieth , M ayer’s m o st fa­ m ous and personally m o st esteem ed professor at T u b in g en . His posthum ously pu b lish ed book of 1836, Views on the World o f N ature and the L ife o f the Soul, was

devoted overwhelmingly to th e investigation of th e phenom enological and o n to ­ logical sim ilarities and differences am ong a series of entities ranging from the soul to m a tte r and m o tion via th e vital force and th e im ponderables. T here is, to be sure, no direct evidence th a t M ayer read this work. Fortunately, given the prom i­ n ence of th e issues in works we can b e sure M ayer knew, such as A u ten rieth ’s and M uller’s physiology texts, or in one he stood a good chance of knowing— his teacher Elsasser’s 1834 edition of M agendie— th e thesis to be argued here does n o t absolutely require him to have done so. N evertheless, th e assum ption th at M ayer read A u ten rieth ’s Views renders his problem context and initial insights m ore vividly intelligible th a n any o th er know n to me. Carl A ugust W underlich, M ayer’s university friend and later a professor of m edicine at Leipzig, wrote a History o f M edicine in which he identified several schools of physiological thinking current in G erm any during th e decades around 1800. O ne Anschauungsweise, which h e associated w ith Reil, H um boldt, and o th ­ ers, sought to u n d erstan d life in term s of th e general laws of n ature applied to the particular com binations and arrangem ents of th e fam iliar substances of the phys­ ical world found in organic (read: organized) beings. He attrib u ted a second way of regarding life to A utenrieth: A second p o in t of view regards th e principle of vital events [Lehensvorgange] as som ething distinctive, though comparable and analogous to the other imponderable substances. It is n o t electricity, not m agnetism , b u t a specific principle th a t only has analogies w ith th em . This was already a n o t u n im p o rta n t step forward. It stem s from A u ten rieth an d was expressed in m any places in his Handbook o f Em pirical H um an Physiology (1801). An extensive consideration of th e relationship betw een th e vital principle and th e im ponderables is found in th e dissertation of A u ten rie th ’s (M atthes respondens), O n the D ifference between the Nature o f the Organic Force and the Impon­ derable Fluids. A uten rieth d em onstrates at length there th a t th e vital principle can be confused w ith n o other im ponderable, b u t is com pletely specific.330

Let us look first, th en , at the two works W underlich m entioned. A u ten rieth devoted a separate section of his Handbook to th e “Similarity b e ­ tw een th e Vital Force and the Im ponderable Substances [Sto/fe].”331 H e began by no tin g th a t since a person’s body n eith er gains nor loses weight upon death, the vital force m u st consist either of an im ponderable substance or in the arrange­ m en t of th e m aterial parts of th e body. T h e m ost telling analogy h e invoked was betw een th e indefinite m ultiplication of vital force in th e process of reproduction and th e ability of im ponderables to undergo a sim ilar indefinite increase, as evi­ denced by a n u m b er of com m on phenom ena: Just as a m agnet can m ake an o th er piece of iron m agnetic, b o th to g eth er a third, and so on w ith o u t end, w ith o u t this propagation of m agnetism bein g a m ere appor­ tio n m en t [Vertheilung] of a determ in ate quan tity of th e m ag n etic m a tte r of th e first; for th e last piece of iron m ade m agnetic (and likewise every o th er piece in th e w hole collection), if it is rubbed by th e w hole collection of all th e pieces previously m ade in to m agnets, can becom e incom parably stronger th a n th e first m agnet, w hich set all

th is in m otion ; just as here there is a true gen eration [Erzeugung]; just as furtherm ore a sm all q u an tity of electricity can cau se th e u n lim ite d p rod u ction o f a larger q u an tity by m ean s of th e voltaic condensor; just as, finally, a b u rn in g kernel of g u n p ow der can set fire all at o n c e to a w h ole h eap o f th e m w ith o u t this flam e b e in g m erely a p p ortion ­ m en ts o f th e original flam elet: In th e sam e w ay th e vital force of o n e organic b od y produces others ad in fin itu m w ith o u t th is progeny c o n sistin g m erely o f an a p p o rtio n m en t o f th e first fo r c e,352

A gainst this co m m o n capability of the vital force an d th e im ponderables to regenerate them selves as they are passed from one body to another, A u ten rieth co n tra ste d th e behavior of “m ech an ical” system s, in w hich th e propagation of force is always acco m panied by its division: O n th e oth er hand, in th e m ech a n ica l world every propagation o f force is m erely ap p ortion m en t. A m o v ed ball can, to b e sure, sim u lta n eo u sly se t in m o tio n tw o o th er equal balls; b u t each of th e latter will th e n proceed w ith only h alf th e force o f th e first. Just th is apparently greater size of th e e ffe c t than th e cau se— insofar as th e n u m b er and bulk o f the organic progeny is greater than th e n u m b er and m ass o f th e organic ancestor— by w h ich b esid es th e vital force th e im p on d erab le su b sta n ces are in general d istin gu ish ed from th e m ech a n ica l e ffe c t o f im pact and c o u n terim p a ct in th e case o f ponderable su b stan ces, is also e v id en t w ith th e vital force in th e m anner in w hich external stim u li act on an an im ate part.333

For exam ple, stim u latin g only a few fibers of a m uscle will cause its en tire m ass to c o n tract, and an insignificant prick of a th o rn can cause a horse to leap several feet. A u ten rie th called explicit a tte n tio n to th e “lack of p roportion betw een effect an d cause” in an im als’ response to stim u li.334 T h ese an d o th er p h en o m en a, such as th e retu rn of th e vital force to oncefrozen body parts, A u ten rie th believed justified th e conclusion th a t th e capacity to p roduce vital m o tio n s m u st lie n o t in a particular arran g em en t of parts or solely in a p articu lar chem ical co m b in atio n of th e conventional im ponderable sub­ stances in an organ. R ather, as th e first cause of these m otions we m u st assum e th e existence of a d istinctive im ponderable substance th a t follows th e sam e laws as th e o th er im p onderables, just as one assum es th a t it is th e presence of a d istin c­ tive galvanic fluid or m ag n etic substance th a t decom poses w ater or m oves iron filings.335 A m ong th e analogies A u ten rie th elaborated b etw een th e vital force an d th e im ponderables was th e in stan tan eo u s propagation of electrical, m agnetic, and nervous ac tio n s.336 H e in terp re ted th e appearance of “Priestley’s green m a tte r” an d infusoria in distilled w ater as evidence for “th e probability th a t vital force in general can also com e in to existence w here previously none was evident, just as galvanic fluid newly com es in to existence, at least for th e observer, in th e case of h etero g en eo u s m etals a n d evaporating liquids, and as do electricity an d h e a t by m eans of friction and m ag n etic fluid in iron by m eans of an im p act in a certain d irec tio n .”337 W h e re those substances com e from , beyond th e ken of th e observer, A u ten rieth did n o t there say; his purpose was sim ply to m ake his root analogy m ore acceptable.

T h e issues b ro a c h e d in 1801 w ere fu rth e r exp lored te n years la te r in th e m e d i­ cal d isse rta tio n of o n e o f A u te n rie th ’s s tu d e n ts , O n the D ifference betw een the N a tu re o f the O rganic Force a n d th e Im ponderable Fluids. W liile re p e a tin g som e o f th e sim ilarities A u te n rie th h a d in siste d u p o n , th is sh o rt work was m ore c o n ­ cern e d w ith th e ir differen ces. T h e im p o n d e ra b le s, for ex am p le, can pass th ro u g h e m p ty space a n d , o n ce in e x isten ce, can c o n tin u e to exist in d e p e n d e n tly of p o n ­ d e ra b le m a tte r, w hereas th e organic force (vis organica) is never fo u n d w ith o u t its asso ciated p o n d e ra b le m a tte r.338 A n d w hereas th e p ro te a n organic force is c o n ­ sta n tly ch a n g in g w ith in a given organism , a n d is su b je c t to m u ta tio n in th e p ro ­ d u c tio n of fertile p la n t h y b rid s, “th e im p o n d e ra b le fluids declare th e im m u ta b il­ ity o f th e ir k in d ": “T h e re is n o c o m m o n tertiu m q u id b etw e e n galvanism and electricity, n o r b e tw e e n th e la tte r a n d m a g n e tism ; galvanism always rem ains gal­ vanism , lig h t lig h t, etc. etc. N o im p o n d e ra b le passes over in to a n o th e r by m ean s of a hybrid. T h e d e v e lo p m e n t of o n e im p o n d e ra b le fluid from a n o th e r never takes place by m e a n s of an in te rm e d ia te species or a n in sen sib le tra n s itio n .”339 T h e organic force, fu rth e rm o re , c o n ta in s w ith in itself a “first c a u se ” of its “p rim itiv e activity,” w hereas th e im p o n d e ra b le fluids, like p o n d e ra b le m a tte r, only c h an g e as a resu lt of an ex tern ally a p p lie d fo rce.340 M a tth e s ’s d is se rta tio n d iffered so m e w h a t fro m A u te n rie th ’s H andbook in its tre a tm e n t of th e cap acity of th e o rganic force a n d th e im p o n d e ra b le fluids to u n d e rg o in d e fin ite increase. A c c e p tin g p a re n ts ’ ability to p ro d u c e offspring w ith ­ o u t sufferin g a “d is trib u tio n ” of th e ir o rganic force or a decrease in its in te n sity — th u s in creasin g th e a m o u n t o f organic force in th e w orld— M a tth e s arg u ed th a t h e a t, lig h t, a n d e le c tric ity show a d ecrease in in te n sity w hen c o m m u n ic a te d to o th e r b o d ies or in to a larger sp a c e .341 O nly in a n o th e r c o n te x t d id h e invoke A u­ te n r ie th ’s ex am p les of th e in d e fin ite m u ltip lic a tio n o f th e im p o n d e ra b le s, n am ely w ith resp ect to th e ab ility o f th e organic force to se t lim its to its ow n increase— as show n, for ex am p le, by th e fa c t th a t a h a re a n d an e le p h a n t w h o e a t th e sa m e food nev erth e le ss a ssu m e vastly d iffe re n t sizes. Im p o n d e ra b le s, on th e o th e r h a n d , are in cap ab le of s e ttin g any lim it to th e ir ow n increase: “Fire . . . w ould b u rn to e te r­ nity if n ew w ood w ere c o n sta n tly su p p lied ; n o r w o u ld a co n sta n tly m o v ed e le ctri­ cal m a c h in e lack for th e e le c tric flu id , n o r w ould m a g n e tism cease its ex p an sio n if you c o n tin u o u sly ru b b e d n ew steel rods w ith th e old m a g n e t; rath er, it w ould increase w ith o u t b o u n d s .”342 N o tin g th a t th e p e c u lia r p ro p e rtie s o f b o th p o n d e r­ ab le m a tte r a n d th e im p o n d e ra b le s are an ex pression of th e ir ow n n a tu re a n d n o t so m e th in g o n e class derives from th e other, M a tth e s asked rhetorically a t th e end: “W h y s h o u ld n ’t th e cau se o f th e o rg an ic force . . . b e tak en to b e d istin c t fro m th e n a tu re of p o n d e ra b le a n d im p o n d e ra b le [su b sta n c es]?”343 In a sim ilar fashion, he fu rth e r su g g ested th a t th e soul, co n scio u s of its freed o m , is a n e n tity sui generis d is tin c t from th e o rganic force. A lth o u g h A u te n rie th stressed sim ilarities a n d M a tth e s differences, th e y w ere in su b sta n tia l a g re e m e n t th a t th e vital or o rganic force is like th e im p o n d e ra b le s in c e rta in regards b u t n e v e rth e le ss essentially d is tin c t fro m th e m . T h e issue o f th e in d e fin ite (se lf-)m u ltip lic a tio n of b o th vital force a n d th e im p o n d era b les received sim ilar p ro m in e n c e a n d was illu stra te d by essen tially th e sa m e exam ples in b o th

works. A utenrieth returned to these issues with a vengence in the work published posthum ously in 1836. Before examining it, however, let us look at the writings of two other G erm an physiologists, M uller and Elsasser, who addressed the issues from a similar standpoint during the intervening years. In W underlich’s account, “the idea of a certain parallelism betw een the vital principle and the imponderables becam e quite popular in German physiology,” especially with Karl Friedrich Burdach and Johannes Miiller.544 W underlich be­ lieved th at this Parallelisiren had benefited physiology by encouraging the appli­ cation of precise m ethods of investigation developed in physics. Be th at as it may, his inclusion of Burdach in the company of A utenrieth and M uller requires some qualification. Having adopted and retained certain features of the Naturphilosophie th a t had engaged m any G erm an life scientists more substantially during the first decade or two of the century, Burdach defended views that found little reso­ nance in the late 1830s. Unlike m ost writers of th at decade, who regarded the imponderables as weightless fluids, for Burdach vital activities resemble electric­ ity, m agnetism , and heat insofar as they are all “dynamical activities,” th a t is, m anifestations of a force, an “internal ground,” which is neither spatially ex­ tended nor endowed with m aterial substantiality.345 Burdach's conceptions of both the vital force and the im ponderables were quite outside the m ainstream when he published them in his Anthropology in 1837 and in the last volume of his Physiology as an Experiential Science in 1840— when he was in his sixties— nor did he press their analogy w ith respect to issues of causality or quantitative increase. His way of thinking about the world had few affinities with the problem context I have identified as providing the background necessary to understand M ayer’s work. Muller, on the other hand, exploited certain analogies between the vital force, the soul, and the imponderables in ways, rem iniscent of A utenrieth, th at raised the kinds of ontological questions I have put forward as central to the contextual understanding of M ayer’s achievement. Addressing the problem of apparent crea­ tion, M uller called repeated attention to the latency of the im ponderables— the concept of latent heat being the original historical exemplar— as an analog for both the calling forth of an energetic vital response to a slight external stimulus and for the replenishm ent of the organic force from ingested nutrients. W ith respect to the first likeness he wrote, in a passage already cited: “T he capability of being determ ined by external influences to m anifestations of force is not proper to organic (in particular, animal) bodies alone. For example, many inorganic bod­ ies develop light under certain conditions— e.g., through im pact— or they develop heat. According to physicists, it is probable th at the light or heat was previously bound in the bodies and becam e free as a result of the external influence.”346 T he second likeness provided one of the strongest reasons for M uller’s favorable esti­ m ation of the “pantheistic view” he sketched in the second volume of his Human Physiology: But as soon as so-called dead matter com es into interaction with the existing organ­ ism, and is transformed by it into the sam e structure and subjected to the vital princi-

pie of th e organism , th e capability la te n t in it for life in a d eterm in ate form also becom es m anifest, and th e form of its activity is co n tain ed by th e already existing organization w ithin its lim its. In this way, by m eans of th e appropriation of m a tte r by an organic being, th e organic force is increased along w ith th e appropriated an d orga­ nized m atter, and through th e increase in force a division of it is again possible. As p h enom ena analogous to th e m anifestation of th e general principle of vitality [Lebensfahigkeit] la te n t in m a tte r one m ight th e n cite th e physical phen o m en a in which an existing force— la ten t, however, as far as appearance is concerned— such as elec­ tricity or light m akes its appearance u n d er d eterm in ate co nditions of th e interaction of b o d ies.347

As already seen, th e assum ption of th e latency of organic force in all m atter solved the vexing problem of the m ultip lication of organic force exhibited in growth and generation. T h u s th e organic force is like th e forces o f electricity, light, and heat insofar as all are capable of existing in b oth laten t and m anifest forms. But the organic force is n ot thereby sim ply a transform ation of th e physical forces o f nature. T h e anal­ ogy was designed to render plausible a particular con cep tion o f the organic force, not to assim ilate it to th e physical forces of nature. M uller hastened to make that clear early on in his com p en diu m . After discussing the phen om en a w hich h e b e­ lieved support th e assum ption of an indep en den tly existing and, as it were, com ­ m unicable organic force, and after invoking the analogy w ith th e known im p on ­ derables of physics, h e cautioned: “As certain, w ith all these facts, as th e existence of an often quickly acting and spatially extend ing [organic] force or im ponderable substance is, so little is one justified in taking it to be identical to the known im ponderable substances or general forces o f nature such as heat, light, and elec­ tricity, a com parison that is rather con fou n d ed by every closer investigation .”348 M uller reinvoked this guid ing analogy and its pivotal notion of latency when he considered th e interaction b etw een the soul and th e organism. His introductory paragraph is worth q u otin g in full: T h e relationship betw een th e soul and th e organism can in general be com pared w ith th e relationship betw een any physical general force an d th e m a tte r in w hich it m anifests itself— e.g., light and th e bodies in w hich it makes its appearance. W h a t is puzzling ab o u t th e connection rem ains th e sam e in b o th cases. Light makes its ap ­ pearance in bodies partly th ro u g h merely m echanical change in th eir m a tte r— e.g., pressure and im pact— partly through a chem ical change in th em . Light is in tu rn also capable of bringing ab o u t m aterial changes in bodies. Likewise, electricity makes its appearance through m aterial change in bodies and here in tu rn produces m aterial changes in bodies. Psychic actions [geistige Wirkungen] occur in organic bodies as long as their m a tte r changes, and th e psychic actions here in tu rn change th e m atter. For th e germ contains, along w ith its indw elling vital force, at th e sam e tim e th e la ten t force ίοτ th e psychic actions of th e subseq u en t anim al being; before a d eterm in an t structure of th e brain has b een created, th e organic activity of th e germ also rem ains w ith o u t ideas [Vorstellungen]. Along w ith th e structu re is given th e activity of th e already existing force, w hich in its u ltim ate ground [Grund] is therefore n o t depen-

dent on the structure of the brain, but with respect to its manifestation is dependent on that structure. Up to that point the relationship between the psychic forces and organization is not more puzzling than the relationship between every other natural force and the material state of bodies, or rather both are equally puzzling. The rela­ tionship between the psychic forces and matter differs from the relationship between other physical forces and matter only because the psychic forces are present only in organic bodies— in particular, those of animals— and because they propagate them­ selves only to their same products, [whereas] the general physical forces, which one also calls imponderable substances, have a much more general action and distribution m nature. Since, however, organic bodies are also rooted in inorganic nature and live from it (in that animals nourish themselves from animals and plants, plants however nourish themselves in part from inorganic substances and thereby grow and multiply), it therefore remains uncertain whether the disposition [Anlage] to psychic actions itself is not also present and becomes manifest in a determinate way by means of the existing structures.349

M uller has here am plified his analogy w ith th e latency of force: n o t only is force, w h eth er organic or physical, released w hen ponderable m a tte r is appropriately distu rb ed , b u t th a t now -m anifest force can in tu rn act back on m atter. H e has also exploited a co m m o n fu n c tio n of such suggestive and ten tativ e analogies by a p ­ pealing to th e puzzling an d unexplained aspects of th e nevertheless generallyaccepted co n cep tio n of th e physical forces of nature: my vital force is no m ore p ro b lem atic th a n th e forces you accept. A lthough M uller closed th e paragraph w ith his usual diffidence tow ard expressing m etaphysical views in a scientific work, it is clear w hat kind of ontological ideas h e th o u g h t w ould answer som e of th e m o st difficult questions ab o u t life. N o te, too, th a t although th e soul, like th e vital force, requires th e presence of an organ of appropriate stru ctu re in order to m an ifest itself, its existence is n o t d e p e n d e n t on th a t stru ctu re, b u t rath er the o th er way around: th e stru ctu re is th e m an ifestatio n of th e operative idea or force. W e have already en c o u n te red C arl Ludwig Elsasser, M ayer’s professor of phys­ iology an d pathology at T iibingen, as an early an d severe critic of th e co n cep t of vital force. A central part of th a t critiq u e involved a brief discussion of th e status and legitim acy of a range of en tities considered to underlie th e p h en o m en a of b o th organic and inorganic nature. Is one dealing w ith im ponderable substances, w ith forces (eith er organic or physical), w ith som e im m aterial principle, or with th e properties of ponderable m atter? In o p tin g for th e last-nam ed, Elsasser no t only d en ied a special vital force, b u t, in accepting a world in w hich only p o n d er­ able m a tte r and its properties are real, called in to q u estio n th e existence b o th of im ponderables and of any in d ep en d en tly existing forces: The whole controversy over the causes of life turns in general on the question: are the distinctive phenomena in living bodies results of the forces of their matter, thus of their chemical and mechanical composition, such that their differences would be explained simply in terms of the differences of the latter (as is the case in inorganic nature), or do they derive from a principle which is to be sought outside the properties of matter? One saw in this principle either something wholly immaterial, spiritual

[Geistiges], or one assum ed a substrate for th e general vital force related to th e im ­ ponderables. . . . A gainst th e assum ption of an im ponderable m a tte r as substrate for th e general vital force is th e variety of vital processes th a t this one substance would have to produce, besides th e circum stance th a t physicists still leave it questionable even for th e custom ary im ponderables w hether they really exist or are n o t ratheT m ere properties or forces of th e ponderable substances in w hich th e ir effects [or actions (W irkungen)] are m anifest.— O ne would be able to decide in favor of th e acceptance of such hypotheses only if it were proven positively im possible th a t th e different activities of living bodies can be th e result of their chem ical an d m echanical com posi­ tion. In inorganic natu re we always see m a tte r and force change sim ultaneously: if two bodies have different com position and form , they also have different forces; if a body exhibits a distinctive force, then we also find a distinctive state o f its m atter or can at least infer such (if th e im ponderables are not real sustances, th e n th eir effects m ust likewise be derived from a change in com position or at least in th e m u tu al position of th e atom s). In accordance w ith these experiences we everywhere regard th e forces of inorganic n atu re not as en tities in th e ir own right [eigene Wesen], b u t as m ere proper­ ties of m atter. Now should this relationship betw een m a tte r an d th e activity-deter­ m ining forces in living nature be som ething else? D o n ’t th e living bodies endow ed w ith distinctive forces also have a distinctive com position an d form of th eir m a tte r?350

O n e of M ay er’s p rim e tasks w o u ld be to v in d ic a te for force th e sta tu s of an im m a ­ terial su b sta n c e existin g in d e p e n d e n tly of m a tte r: it is n o t ju st a p ro p erty of so m e ­ th in g else. A lth o u g h th e leg itim acy of th e vital force p e r se was n o t M a y er’s c e n tra l c o n c ern , th e o n to lo g ical issues raised in th e c o n te x t o f its tr e a tm e n t in c o n te m p o ­ rary physiological w orks— typically involving c o m p a riso n w ith th e im p o n d e r­ ables— set th e c o n c e p tu a l stag e o n w h ich h e w o uld shap e h is in n o v ativ e d o c trin e of force. T h e h ig h -w a te r m ark of a tte m p ts to e lu c id a te th e n a tu re of th e vital force by ex p lo itin g th e analogy b e tw e e n it a n d th e im p o n d e ra b le s was, in th e G e rm a n y of th e 1830s, A u te n rie th 's View s on the W orld o f N a tu re a n d the L ife o f the Soul. In m any ways th e e n tire 552-page b o o k was an e x te n d e d — in d e e d , a ted io u sly re p e ti­ tio u s— e la b o ra tio n o f th a t analogy, w hich A u te n rie th ex p lo ited to justify th e as­ su m p tio n of th e ex isten ce of b o th a vital force a n d a soul as e n titie s in d e p e n d e n t of m a tte r a n d cap ab le of in d e fin ite increase. If y o u ’re w illing to a c c e p t th u s-a n d so for th e im p o n d e ra b le s, even w h en you c a n ’t explain it, th e n you sh o u ld n ’t balk a t a cc e p tin g an analo g o u s vital force. B u t w hereas M u ller ex p lain ed th e a p p a re n t c re atio n o f th e vital force a n d th e soul in te rm s of th e ir laten c y in p o n d era b le m a tte r, A u te n rie th u se d th e sam e p h e n o m e n a to justify b elief in a realm of exis­ te n c e b e y o n d th e physical w orld. Significantly, b o th solu tio n s w ere p rem ised on th e im p lic it a b su rd ity o f g ra n tin g th e creatio n of s o m e th in g o u t o f n o th in g . So c e n tra l to A u te n rie th ’s c o n c e p tio n of th e vital force was th e analogy w ith th e im p o n d e ra b le s th a t h e scarcely ever spoke of th e fo rm er w ith o u t invoking a c o m ­ pariso n w ith o n e or m o re o f th e latter. A fter in tro d u c in g th e to p ic o f his first essay as th e n a tu re of life a n d its vital forces, h e p ro ce ed e d to id e n tify a n u m b e r of th in g s c o m m o n to all organic beings: th e ir form s rem ain w ith in d is tin c t b o u n d -

aries; they constantly exchange substances with the external world; they respond in a complex fashion to external stimuli; they grow and reproduce. W ith that, Autenrieth had cataloged pretty m uch the standard set of phenom ena assigned to the vital force. He went on: T h is com m on so m e th in g th a t expresses itself in all living bodies can b e considered n o t only by itself, separate from th a t w hich otherw ise d istin g u ish es every species, b u t one can also ask w h eth e r it is n o t also u n d erlain by a co m m o n an d real force possess­ ing an au to n o m y of its own, ap art from th e existence of th e organic body in w hich it acts, or w h eth e r life, w ith o u t an an to n o m o u s basis [G ru n d], is m erely a p roperty of visible body m ass assem bled in a d eterm in a te fashion in to a p la n t or an anim al. S uch a questio n m ay well b e raised because even th e co n tinually a g itated force of h e a t in h e a te d bodies is n o t visible to us separately; b u t we perceive h ere th a t its a ctio n com m u n icates itself to even th e m o st varied bodies w ith always th e sam e char­ acteristics, and th a t [on th e o th e r hand] its p h en o m en a in th e sam e corporeal su b ­ stance are now present, now absent, can now strongly express them selves, now be p resen t to a dim in ish ed degree . . . . W e therefore co nsider ourselves justified in as­ cribing th e p h en o m en a of h e a t to th e presence of a p articu lar au to n o m o u s force, w hich is to be sure capable of com bining w ith all space-filling bodies, b u t w hich is n evertheless still d istin c t from th e m all.551

The ability of heat and the “m agnetic fluid” to pass through space devoid of ponderable matter demonstrates that heat and m agnetism are independently ex­ isting entities, not mere properties of matter; and he believed (without apparent logic) that certain com m on phenom ena of m agnetization demonstrate the preex­ istence of the m agnetism before it becom es manifest in a particular body.3’2 In driving hom e the force of his analogy, Autenrieth invoked the equivalent inexpli­ cability of what happens to electricity, light, and life when each disappears from the visible world: Since we already recognize activities in th e rest of n a tu re w hose cause ca n n o t be m erely a property of th e bodies in w hich they are active, we m ay likewise investigate, w ith o u t u n d erta k in g anything contrad icto ry or frivolous, w h eth er th e basis of life, even if it is perceptible to us only in th e living body, does n o t nevertheless lie in an a u to n o m o u s force th a t— like th e m ag n etic fluid, w hen it com es to th e iron m akes it in to a m ag n et, an d w hen it again leaves it leaves it b eh in d as th e m ere u n m ag n etized iron it was earlier— in th e sam e way com b in in g w ith organic m a tte r an im ates it, w ith ­ draw ing from it leaves it again dead, in this regard, th e n , again th e sam e as every o th er p onderable corporeal substance. It is n o o bjection th a t h e a t an d lig h t only b eco m e perceptible to us in a sta te of u n in te rru p te d m o tio n , since we likewise also recognize life only th ro u g h its m anifestations of activity. Just as we do n o t perceive in th e case of electricity w here it again w ithdraw s to w hen it again suddenly disappears for all our sense thro u g h th e reunification of its opposing form s, th e positive an d negative elec­ tricities, a n d just as we do n o t know w here light goes w hen it is ex tin g u ish ed , in th e sam e way we are also n o t capable of perceiving w here life escapes to w hen th e anim al o r p lan t dies, an d only its visible body rem ains b e h in d for a tim e in its exterior fo rm .353

So, too, does th e sudden appearance of a disease-producing contagion dem o n ­ strate the existence of an “extrasensual world,” th e same “indifferent source” from which its opposite, th e vital force, also com es.554 W h e n a candle burning in a m irror-lined room is extinguished, th e light previously present does no t becom e laten t in th e walls, nor do the positive and negative electricities th a t recom bine in a wire becom e laten t in th e wire. In bo th cases the once-present im ponderables have literally withdrawn from th e phenom enal world, from space itself.555 T he fulm inates of silver and gold (Knallsilber and Knallgold) explode with great force upon being struck, yet they can be chemically decom posed w ithout exploding or releasing a com parable quantity of electricity, heat, or light. T h e la tte r’s nonla­ tency in th e original com pound had profound im plications: T hose im ponderables are therefore n o t laten t in th e small q u an tity of fulm inate, otherw ise they would m ore or less also have to becom e free w hen th e la tte r is dis­ solved. Now, since one also can n o t assum e th a t they could have been suddenly gath ­ ered together in such an im m ense quan tity o u t of th e surrounding air at th e m o m en t of th e explosion in order thereby to create the latter— som ething th a t could be raised to an incontrovertible certainty through observation of an electrom eter and th erm o m ­ eter in th e neighborhood of th e explosion— one m u st thus assum e th a t these im pon­ derable fluids com e into th e spatial world [R aum w elt] only a t th e m o m en t of the explosion. In th e same way it can also be shown th a t th e w ithdraw al of electricity from th e spatiaI world when its two opposing forms m utually com bine w ith each o th er is n o t a redistributing of the previously accum ulated electricity in the neighborhood of th e surrounding air— a d istribution th a t could only occur gradually, n o t suddenly be achieved. In th e same way even physics can prove th a t there really is, in th e case of the im ponderables, a com ing to the spatial world and again a w ithdraw al from it, and th a t therefore— unless one wishes to assum e a perpetual passing over of one part of crea­ tio n in to nothing and its reappearance o u t of nothing— a real world of d eterm in ate diverse forces m u st occur beyond or outside all space, forces that, given th e appropri­ ate co n stitu tio n of th e corporeal world w hen it (as it were) unlocks the world beyond [das fenseits], are capable of slowly or suddenly com ing in to it, b u t likewise also of again w ithdraw ing from it.556

T hu s th e assum ption of w hat m ight be called a preterphysical realm is th e only way to avoid having to grant creation de nihilo and destruction ad nihilum , a point A utenrieth m ade again and again. T h at realm, of whose existence physics assures us, is also th e abode of vital force and soul.557 A utenrieth likened the appearance of th e ego (unser geistiges Ich) in connection w ith the generation of an appropri­ ate organ, th e brain, to th e appearance of m agnetism in a piece of iron struck while being held along the m agnetic m eridian.558 Both th e soul and th e m agnetic force exist before their m anifestation in th e m aterial world. A utenrieth em bel­ lished th e analogy by likening the fertilization of toads’ eggs by extrem ely dilute sperm to th e ability of a small spark to set off a large mass of gunpowder: “T he mass of fire w hich this produces was no t in th e small fiery spark which ignited the powder, b u t w ith o ut this little spark it would never have appeared by itself. T he anim ation of organic germs likewise appears to be an opening up of the spatial

world for th e supervening of force from th e nonspatial Beyond, an opening up already h in ted at by p h en o m en a of even in an im ate nature. A u ten rieth cited a variety of p h en o m en a w hich he th o u g h t d em o n strate “th a t th e vital force is so m eth in g sui generis [etwas Eigenes] , w hich can have by itself a kind of c o n tin u ed existence even w ith o u t b eing joined to an organic body.”560 Such p h en o m en a, w hich reinforced th e analogy betw een th e vital force an d th e im ponderables, in cluded things like sp o n tan eo u s generation, th e regeneration of snails’ heads, and th e revivification of frozen anim als. For A u ten rieth , th e lastn am ed p h en o m en o n was an instance of th e vital force’s leaving and th e n re tu rn ­ ing to th e affected organism . H ere, too, belonged th e co m m on ability of th e vital force and th e im ponderables to undergo indefinite m u ltip licatio n as long as the ap p ro p riate substances or m otions were provided, though th e vital force d istin ­ guishes itself by its ability to create new self-contained and in d e p e n d e n t entities (i.e., individual organism s) as a result of its q u an titativ e increase.361 A u ten rieth p o in ted o u t th a t although th e im ponderables th u s share w ith th e vital force a trait w hich distinguishes b o th of th em from th e q u an titativ e invariability of p onder­ able m atter, it is only the vital force th a t possesses th e capability of se/f-m ultiplication: th e activity of an external agency is required to bring ab o u t a m u ltip lica­ tio n of th e im p o n derable fluids.362 So, too, does th e analogy break dow n w ith respect to th e ability of th e vital force to m anifest itself in a diversity of ways and in ever h ig h er stages of developm ent, w hereas electricity, th e m agnetic fluid, h eat, and light rem ain just w hat they have always b e e n .365 B oth th e vital force and th e im ponderables— w ith th e exception of h ea t— m a n ­ ifest intrinsic polarities (Polaritaten) or an tith eses (Gegensatze), whose co n stan t ratio in th e im ponderables indicates th a t they represent a “division of a com m on n eu tral activity or indifference [Indifferenz\ of th e particular fluid.”364 O n the o th er han d , only w ith respect to th e vital force are those polarities always active, never in com p lete eq u ilib riu m .365 O rganism s th u s possess a “n o t fu rth er explica­ ble basis” of au to n o m o u s internal activity:366 In th e indifference of that which, when divided, expresses itself as two kinds of elec­ tricity there appears no self-determ ining activity . . . . Even when divided electricity has been called forth, its remaining divided does not depend on itself but is entirely dependent on the bodies with which it entered into com bination. W ith the organic vital force, on the other hand, not only are the antitheses indeed produced in the same body . . . , but they also separate them selves by them selves more and more from each other in very different ways especially determ ined for each different species . . . . Thus here, too, the organic vital force, although its appearance is likewise still dependent on the influence of the corporeal external world, nevertheless already reveals vis-a-vis the im ponderables an active self-determ ination, and thereby in general a certain indepen­ dence of its m otion, m otion whose continuance and change does not therefore also depend solely on the external cause that called it to appear in the spatial world.367

Such a h id d en source of self-m ovem ent, A u ten rieth suggested vaguely, m ight also explain th e c o n tin u ed m o tio n of th e planets: “In th e sam e way only a co n tin u in g source of all m o tio n, n o t an im pulse im p arted once in rem ote antiquity, m o st

likely . . . explains th e continuation of the m otion of all of the stars, the sun, and our earth, since space does n o t appear to be any kind of absolute vacuum .”368 T hus, to use term inology which A utenrieth here did not, bo th m icrocosm ic and m acrocosm ic organisms harbor w ithin them selves an internal source of m otion, and are thereby distinguished from the merely reactive world of ponderable and im ponderable m atter. Here, as so often elsewhere, the validity of a guiding anal­ ogy was assessed and circum scribed by exploring the ram ifications of its outer reaches, though occasionally A utenrieth seems to have lost control of his images, as when he cited th e ability of motionless ponderable m atter to entice (entlocken) not m o tio n b u t th e force of attraction from the sam e im m aterial preterphysical source from which the im ponderables are enticed as a result of certain physical activities (as electricity through th e rubbing of am ber or light and heat through the collision of steel and sto n e).369 In another context, A utenrieth described the sun and stars as sources of light they draw from a universal invisible source.370 A u ten rieth ’s image of the solar system, the very paradigm of gravitational attrac­ tion, as containing som ehow within itself a source of m otion or force, has close affinities with M ayer’s atte m p t to relate the creation of heat and light in the sun to the gravitationally constrained m otion of the planets around it. Both m en sought to justify th e plausibility of their ideas by appealing to an analogy betw een organisms as creators of force and th e solar system as an organism. A utenrieth’s notion of the origination of opposing activities o u t of a prim itive state of “indiffer­ en ce” also recalls M ayer’s use of a similar conception. A u ten rieth ’s richly elaborated analogy betw een th e im ponderables, the vital force, and th e soul was part of an overall strategy designed n o t only to render the latter two entities scientifically legitim ate by assim ilating th em conceptually to certain essential characteristics of generally accepted substances, b u t also, m ore particularly, to render plausible th e idea of independently existing substances th at do n o t occupy space and the idea of w'hat I have called a preterphysical realm of existence beyond th e visible spatial world. Light, th e force of gravitational attrac­ tion, and th e vital force are all such really existing yet im m aterial and nonspatial entities: B u t already a c lo ser c o n sid e r a tio n o f l i g h t . . . d o e s n o t allo w u s to ap p ly th e c o n c e p t o f fillin g sp a ce [R aum erfiillung] . . . to ev er y th in g th a t w e m u s t u n d e n ia b ly regard as so m e th in g real, as an in d e p e n d e n tly e x is tin g en tity . If th e prop erties o f lig h t— w h ich , d e s p ite its reality, still o n ly h a s th e c a p a b ility o f fillin g sp a ce in o n e o f th e la tte r ’s th ree d im e n sio n s— give our th in k in g ability a p o in t o f su p p ort in order to rise gradually to th e c o n c e p t o f a u to n o m o u s an d n e v e rth eless n o n sp a tia l e n titie s , and to w e a n u s from im a g in in g e v er y th in g th a t e x ists o n ly in e sse n tia lly corp oreal form ; so can th e p r o se c u ­ tio n o f th is c o n sid e r a tio n also serve to a cq u ire for u s s o m e c o n c e p tio n n o t on ly o f h o w th e h e a v e n ly b o d ie s sc a tter e d in in fin ite sp a ce c o u ld , a c co r d in g to th eir d ifferen t p o s itio n in sp a ce, exert a d iffe re n t in flu e n c e o n a vital force th a t, a lth o u g h n o t itse lf e x is tin g in sp a ce, is n e v e rth eless u n iversal an d a u to n o m o u s , b u t also o f th e fa ct th a t th e s e d iffe r e n t extern al in flu e n c e s are e v e n ca p a b le o f e x c itin g in su c h a n o n sp a tia l so u rce o f force in tern al c h a n g e s u n ite d in to a particular un iversal sy stem . Insofar as

w e im a g in e th e so u r c e o f th e lig h t a b o d y calls fo rth or a ttra c ts as its e lf e x tra sp a tia l, n o th in g c a n p r e v e n t u s from n e v e r th e le s s s im u lta n e o u s ly a s s u m in g th a t th is so u rc e o f lig h t, d e s p ite its n o n sp a tia lity , c a n still retain all o f t h e p a rticu la r c h a r a c te r istic s th a t h a v e n o th in g t o d o w ith sp a c e , th u s for e x a m p le th e c a p a b ility o f b e in g a b le to b e in d u c e d to e x h ib it n o w red , n o w g reen , y ellow , or b lu e lig h t. N o t every p rop erty o f an a u t o n o m o u s e n tit y fo llo w s sim p ly from t h e w ay in w h ic h it fills sp a ce . . . . S u c h p ro p ­ e r tie s o f l i g h t . . . [are] e n tir e ly in d e p e n d e n t o f its fillin g sp a c e . . . . In ste a d o f m a k in g u s e (as h e r e ) o f th e fic tio n o f lig h t, w e c a n a lso u s e as o u r c o n c e p t io n a n y o th e r im p o n d e r a b le flu id , a c co r d in g ly e v e n th e u n iv ersa l v ita l fo rce its e lf, as lo n g as it is still o n ly a q u e s tio n h ere o f th e fo r m a tio n o f in te llig ib le m o d e s o f c o n c e p tu a liz a t io n .371

A lthough we ca n n o t form a m en tal im age of such a nonspatial entity, n o th in g prevents us from defining it in term s of concepts draw n from experience.372 D e ­ spite its n o n m aterial an d nonspatial character, A u ten rie th frequently referred to it as a sub stan ce (Substanz) .373 O n e is rem inded here of M ayer’s efforts to vindi­ cate th e “ su b stan tiality ” of force. A u ten rieth devoted a great deal of a tte n tio n to th e existence of a g raduated series of en tities ru nning from ponderable m a tte r at one en d th ro u g h th e im p o n ­ derables, th e vital force, and th e soul at th e o th er.374 In th e som etim es inconsis­ te n t and always tedious actuality of A u ten rie th ’s exposition, he also elaborated a slightly different series consisting of ponderable m atter, th e im ponderables, grav­ itational attraction, and m otion. In n eith e r case did he always trea t every m em b er of th e series w ith respect to th e particular trait u n d er consideration, and m y ac­ co u n t represents an a tte m p t to bring som ew hat m ore order to these issues th an th e tex t itself possesses. Seen from this perspective, A u te n rie th ’s book was first and forem ost an ontological tract: w hat kinds of en tities exist in th e world, and how are th ey related? W e have already looked at th e fu n d a m e n tal properties Aute n rie th a ttrib u te d to som e of those entities. O f fu rth e r interest to us are th e term s in which he characterized an d com pared th e en tities com prising those se­ ries. For exam ple, one m easure of difference was in th e ir degree of activity (Thatigkeit): T h is se lf-d iv is io n o f t h e v ita l fo r c e , as far as it arises o u t o f its o w n a c tivity, in d ic a te s m o s t d e c is iv e ly its h ig h e r s ta n d p o in t in th e series o f e n t itie s . P o n d e r a b le s u b s ta n c e s [S t o f f e ] h a v e n o a c tiv ity o f th e ir ow n ; th e im p o n d e r a b le flu id s e x is t, t o b e su re, o n ly in a n u n in te r r u p te d activity, b u t th is is n o t y e t a free se lf-a c tiv ity in so fa r as its arousal d e p e n d s e n tir e ly o n th e m o t io n s o f t h e corp oreal w orld th a t o b e y s th e la w o f gravity. B u t e v e n t h e se lf-a c tiv ity t h a t . . . first e x p r esses its e lf in t h e o rg a n ic v ital fo rce is n o t y e t a v o lu n ta r y se lf-a c tiv ity d e r iv in g from t h e fr e e d o m o f th e w ill; rather, it lik ew ise still o r ig in a te s o u t o f th e law o f a n e c e s s ity .375

O nly th e soul possesses th e capacity for free— th a t is, freely willed— self-activity. A n o th er feature w hich distinguishes th e different forces— th a t is, excluding ponderable m a tte r from th e com parative series— is th eir degree of autonom y (Selbststandigkeit) .376 T h e m otion of a body is inseparable from th e body in m o ­ tio n and extends no farther th a n th e body; it th u s possesses no independence.

Regarded as a source of m otion, universal gravitation also requires the presence of a body in order to act, b u t its action extends beyond the lim its of th e body; it thus possesses a degree of independence. T h e im ponderables, although likewise m ani­ fest only in th e presence of corporeal m atter, enjoy an existence com pletely inde­ p en d en t of m atter, and unlike gravitation they can be com m unicated from one body to another. T h e vital force, finally, has the sam e independence from its m aterial substrate as th e im ponderables.377 A u ten rieth ’s inclusion of m otion and th e im ponderables w ithin th e sam e class of "forces” was decidedly unusual for his tim e, and even he did no t otherw ise consistently so em ploy th e term inology of force. As far as I can tell, his m ore usual characterization of th e im ponderables as “weightless fluids” did not im ply the inclusion of m otion. Closely related to th e quality of independence was th e som ew hat oddly term ed personality (Personlichkeit), w hich characterizes th e degree of self-contained indi­ viduality m anifested by th e several classes of entities. As A utenrieth saw it, arbi­ trary aggregations of ponderable m a tte r have no particular individual identity, although crystals show th e first stage of separation into distin ct “personalities.”378 Like uncrystallized ponderable m atter, h eat exists only in arbitrarily aggregated am ounts, b u t m agnets m anifest a distin ct “personality.” T h a t is, each m agnet possesses a central Indifferenzpunkt which in a sense joins the opposing m agnetic polarities stream ing ou t from it in closed vortices; although th e range of action of the m agnet extends indefinitely far out, th e ensem ble of Indifferenzpunkt and m agnetic vortex forms a kind of unity.379 Even m ore does th e vital force m anifest itself in separate individuals, though one “organic personality” may, u n d er certain circum stances, be divided— as w hen a plant is propagated by cuttings— just as two previously separate trees m ay unite to form a "com m on tree individual.”380 If such ph en o m en a d em onstrate th e spatial localizability of th e vital force, other p h en o m en a reveal its nonspatial quality. As attestin g the latter, A u ten rieth cited his favorite exam ple of th e equal num ber of m ale and fem ale births, th e supposed increased fertility of w om en after m any people have died in a plague, and the system of relationships th a t connects sim ilar b u t geographically separated species th rough space and sim pler to m ore com plex species through tim e: all of these phen o m en a, h e m aintained, can be explained only in term s of som e kind of spa­ tially nonlocalized, universally diffusable law -bound vital force. At th e end of the series are free-willed spiritual beings whose personalities are inseparable from th eir essence. T hese souls or egos—A u ten rieth used b o th words— possess the fur­ th e r end-of-the-series trait of com plete nonspatiality, just as at the beginning of th e series a com plete absence of personality characterized extended ponderable m atter, which exists only in sharply circum scribed regions of space.381 T h a t the soul is n o t extended in space is shown by th e fact th a t our consciousness is un d i­ m inished w hen even a large portion of th e brain is injured, or when we lose a large part of our body.382 Unlike all th e o th er entities, only ponderable m atter is im perishable, capable of n eith er increase nor decrease.383 Using a word th a t itself hints at his belief in a preterphysical realm , A utenrieth described ponderable m a tte r as “unexpellable” (;unverdrangbar): “B ut if ponderable m atter, too, has only at one tim e em erged

o u t of th a t w hich is beyond all space [aus dem Jenseits alles R aum es hervorgetrete n ] in order to fill it, so is it at least now on o u r ea rth w ith o u t a trace of bein g able to retu rn th ere; it has em erged from th ere com pletely and perm anently, w ith o u t preserving any co n n e ctio n w ith th a t B eyond.”384 Ponderable m a tte r is th u s q u ite unlike th e w eightless fluids, and one m u st n o t suppose th a t th e form er can be tra n sm u te d in to th e la tte r m erely by becom ing, say, rarefied, or th a t th e im p o n ­ derables are n o th in g m ore th a n a particular state of ponderable m a tte r.385 In sup­ p o rt of his c o n ten tio n th a t “th e vital force is so m eth in g au to n o m o u s added to the organic p lan t an d anim al form and again separable from it, n o t m erely th e prop­ erty [Pradicat] of a particular arran g em en t of th e m a tte r m aking up th e organic body,” A u ten rieth cited th e analogous behavior of h e a t, “an im ponderable fluid, w hich can be expressed un ch an g ed by presssure o u t of th e air, a ponderable body, like w ater o u t of a w et sponge, an d th u s m u st b e assum ed to be so m eth in g th a t exists by itself au to nom ously and n o t m erely as an alteratio n in th e activity of the air or a m ere property of a particular state th ere o f.”386 Recall th a t Mayer, too, was a t pains to deny th a t h e a t was a state of ponderable m atter. T h e im p onderables represent a particular m ode of being, betw een im perish­ ab le heavy m a tte r on th e one side an d th e m erely transitory m o tio n of m a tte r on th e o th er.387 A gainst A u te n rie th ’s form er (and exceptional) inclusion of m o tio n an d th e im p o n d erables w ithin th e sam e class of forces, he here distinguished th em : m o tio n is m erely a property of ponderable m atter, w hereas th e im p o n d er­ ables are in d e p e n d e n t en titie s sui generis. Such was A u te n rie th ’s m ore usually sta te d view. T h e invariable m o tio n -p ro d u cin g force of a ttra ctio n belonging to p o n d erable m a tte r occupies a kind of m iddle co n cep tu al ground betw een the pure m o tio n of q u an titativ ely invariable ponderable m asses an d th e in d ep en d e n t b u t q u an titativ ely variable im p o n d erab les.388 Unlike purely m echanical m otion, w hose existence is wholly d e p e n d e n t on po n d erab le m atter, th e m o tio n -p ro d u c­ ing force of universal gravitation shares w ith th e im ponderables th e quality of autonom y, th a t is, th e ability to exist or act in em p ty space in d ep en d e n tly of m a tte r.389 A lth o u g h A u ten rie th did n o t em phasize th e constancy of m o tio n in the world, let alone v en tu re to define a m easure of th e q u a n tity of m o tio n , h e did at least once distinguish th e im ponderables from m o tio n in term s of th e capacity of m o tio n , once created, to c o n tin u e indefinitely if u nopposed, w hereas th e im p o n ­ derables require th e m o tio n of ponderable m a tte r b o th for th eir creation and th eir co n tin u e d ex isten ce.390 A u ten rie th insisted th a t all changes in ponderable and im p o n d erab le substances, including th e vital force, take place only as a result of som e kind of m echanical m o tio n .391 In an am azing analogy h e even com pared the ability of th e spinning ea rth to call forth th e “cosm ic vital force” from th e “dy­ n am ic source of life” to th e ability of a spinning glass sphere to “call into appear­ an c e” an “inexhaustible stream of electricity th a t previously slept in an existence im p ercep tib le to u s.”392 A nd just as ponderable m a tte r a n d th e im ponderables are n o t transform able one into th e other, so, too, is each im ponderable wholly dis­ tin c t from all th e o th e rs.393 E lectricity m ay call fo rth m agnetism , b u t th e process involves no conversion of one to th e other, and each im ponderable co n tin u es to exist w ith its own distinctive characteristics. Similarly, violet light can m agnetize

an iron bar (as h e believed), b u t it does no t thereby cease being light, nor does it acquire th e directional property of m agnetism . A utenrieth viewed this as another expression of th e im ponderables’ autonom y.394 T h e issues p ro m inent in A u ten rieth ’s book would th u s have provided an ideal co n tex t for M ayer’s early reflections on th e n ature of force. W ith in this context a relatively small change in the way the im ponderables and m otion were co n cep tu ­ alized— now as im perishable “forces” wholly in d ep en d e n t of ponderable m atter for th eir existence and capable of being transform ed one in to th e o th er— could have b ro u g h t ab out a radical reorganization of his entire worldview. It is, to re­ peat, th e issues th a t are m ost significant, m ore so th an A u ten rie th ’s own views on this or th a t point. W h a t is a force? An im ponderable? A property of m atter? Recall M ayer's term inological wavering betw een forces and im ponderables, an d his insis­ tence th a t forces m ust no t be confused w ith th e properties of m atter. R epeatedly discussed in A u ten rie th ’s book was th e issue of th e creation and destruction of the vital force and th e im ponderables: his idiosyncratic allowance of th eir passage into and o u t of th e visible world was in fact prem ised on the absurdity of th eir creation de nihilo and d estruction ad nihilum . H e also m ade a point of the im perishability of ponderable m a tte r— a point, as we shall see in ch a p te r 4, th a t virtually no physics or chem istry texts of the period explicitly m entioned. A u ten rieth was also unusual in at least occasionally considering m otion and th e im ponderables to belong to th e sam e class, th a t of forces; and even where he did no t, he repeatedly raised th e issue of th eir relationship. H e insisted on the necessity of m o tio n for th e appearance of th e im ponderables an d th e vital force, even as h e denied any form of transform ation of one species into another. He considered the force of gravitation as a source of m otion and suggested th a t th e sun, the preem inent source of gravitational force in our world, is som ehow the focus of the calling into this world of light and gravitation from th e sam e preterphysical realm . In one place he im plicitly contrasted m echanical and organic systems insofar as the lat­ ter— which include th e solar system — are capable of generating im ponderable fluids and vital force, th a t is, of enticing th em o u t of their hidden realm of exis­ tence. And, finally, A u ten rieth ’s use of th e term “indifference” recalls M ayer’s reasonably similar usage. If there rem ains no hard evidence th a t Mayer read Au­ te n rie th ’s Views on the World o f N ature and the L ife o f the Soul, th en th e least th a t one can say is th a t M ayer’s problematique probably derived from cognate (if less rich) sources, which included A u ten rieth ’s own earlier work an d th e writings of M uller and Elsasser. T h a t A u ten rieth ’s ideas on these m atters enjoyed some contem porary visibility is shown, finally, by th e fact th a t Lotze regarded th em as w orth citing and oppos­ ing in his Lebenskraft article of 1843. O fth e first essay in A u ten rie th ’s book, which Lotze characterized as a “treatise on th e vital force,” he wrote: H e borrows his abstractions from an already m anifestly incorrect consideration o f the im ponderables. A lth ou gh a healthy physics can only im agine tw o kinds o f things under im ponderables— either really existin g im ponderable substances or d istinctive changes and m otion s o f th e co m m o n ponderable bod ies— so is th e d ou b t nevertheless

n o t u n co m m o n (as o th erw ise also— to m e n tio n th is paren th etically— in physiology, especially apropos o f th e nervous principle) as to w h eth er it is su b stan ces or m o tio n s or m erely forces that exist here. N o w th e last is certainly never p o ssib le, for abstract relationships ca n n o t run around in th e w orld w ith o u t so m e th in g th ey b elo n g to. Now, it is u p on su ch m isg u id ed an alogies th at A u ten rieth has erected h is theory o f th e vital force as an a u to n o m o u sly ex istin g force separable from m atter; h e even thinks to find em pirical verification for th is w andering of th e vital force w h en th e b lo o d previously driven away as a result o f th e freezin g o f th e lim b s flow s back in to th e parts u p on h eatin g. It is u p on th is sim p le error th a t his oth erw ise careful and learned work fo u n d ers.395

For L otze, as for m any of his contem poraries, th e im ponderables are eith er really existing weightless substances (S to ffe or M aterien) or, as forces, properties of p o n ­ derable m atter. For him , th e co n c ep t of force rem ained tied to its N ew tonian roots, h ence tied to m atter; any o th er con cep tio n was a n o n ex isten t abstraction. For Griesinger, w riting in 1845, com parisons betw een th e soul an d th e im p o n d er­ ables in term s of th eir sim ilar relationship to m a tte r— b o th appear to b e im m a te ­ rial, and to b o th effect an d b e affected by m aterial transform ations— are of little use. In his view, th ere is "n o th in g really analogous” to th e "psychic or nervous agency.”396 T h e rich analogies of his im m e d ia te predecessors m e a n t n o th in g to him . 3.2 Organisms as M achines T h e m etap h o r of th e organism as a m achine was w idespread in th e G erm an scien­ tific lite ratu re of th e early n in e te e n th century. In som e cases th e m etap h o r was little m ore th a n a passing tu rn of phrase, n o t indicative of any particular c o m m it­ m e n t to m ech an istic m odes of th o u g h t— as, for exam ple, w hen B urdach asked, “W h e re [is] th e seat of life, an d w here th e spring w hich sets th e wheels of th e m ach in e in m o tio n ?”397 Following a favored usage of Berzelius, Friedrich T iedem an n frequently likened th e body to a laboratory (W erkstatte) for th e carrying o u t of chem ical processes: “A living body, considered as an object of chem ical investi­ gation, is, as Berzelius expresses it, a laboratory in w hich m any chem ical processes take place whose en d result is to produce all of th e p h en o m en a w hich in th eir en tirety we call life.”398 M ore charged w ith literal significance was A u te n rie th ’s repeated characterization of th e body as a m ach in e or m echanical arrangem ent (M aschine, M aschineneinrichtung): tor A u ten rie th , as for D escartes, except for th e o p eratio n of th e soul, th e physical an d chem ical functions of th e body take place in a strictly law bound, m echanical, fashion. A nim als' involuntary m ove­ m en ts are, h e th o u g h t, "m erely a m echanical arran g em en t set in m o tio n by the vital force.” O nly th e freely acting soul introduces a physically u n d eterm in e d fac­ to r in to organic processes.399 M uller, too, w hile n o t a defender of a thorou g h g o in g m ech an istic reductionism of th e p h en o m en a of life, nevertheless o ften em ployed graphically m echanical im agery in characterizing organic functions. Recall his likening of th e execution of

th e organic functions to th e harm onious interconnection of th e wheels of the bodily m achine, whereby the respired oxygen was the cause of m otion of the m echanism , and th e lungs, heart, and brain were referred to as th e m ainsprings of th a t m echanism . Recall his reference to external stim uli as the source of m otion of th e gearworks of th e whole m achine. Recall, finally, his later clarification of the quasi-idealistic im port of his m echanical imagery: if, to b e sure, th e body can be likened to a purposeful m echanical contrivance, then it also rem ains true th a t m echanical contrivances do n o t create them selves, b u t rather represent th e reali­ zation of a creative idea. In another place M uller asserted th a t th e m aintenance of a m ature organism , considered apart from th e processes of developm ent and growth th a t characterized its earlier life, can be com pared w ith th e m aintenance of a m achine: “If one com pares th e em bryo of an organic being w ith its state in advanced age, th e n th e whole (which according to Kant determ ines th e existence of th e individual parts) consists in advanced age alm ost only in the interaction of th e individual parts and their forces, in a m an n er sim ilar to a m echanism which is m ain tain ed merely by th e interaction of its p arts.”400 T h e tradition of natural theology, as represented by H enry Peter Brougham , paid particular a tte n tio n to m echanical contrivances and com pared organism s to purposefully constructed m achines and in stru m ents w ith essentially th e sam e in ten tio n as Muller: a m ech ­ anism designed to accom plish a clear purpose ca n n o t be im agined to have com e in to being by itself, independently of a guiding idea (w hether divine or ‘Pla­ to n ic’).401 Brougham repeatedly referred to the special “m echanism s” by which anim als accom plish their vital functions, such as the system of bones and joints or th e paddlelike w ebbed feet of w ater birds. W riting in th e sam e tradition, W illiam P rout followed Paley in aim ing to give readers “som e notion of th e ‘concealed and internal operations of th e m achine’”— by w hich he m ean t the h u m an body.402 Prout, too, used th e argum ent th a t from th e existence of “a m achine adm irably fitted for th e office it perform s” we infer th e existence of an intelligent creator.403 T h e im p o rtan t p o in t is th a t in the pre-1840s clim ate, th e m etap h o r of organism as-m achine was n o t only widespread b u t theologically safe, n o t yet th e polem ical property of an assertive and spirit-denying m aterialism . Krem er has po in ted o u t th e sim ilarity betw een M uller’s m echanistic lan ­ guage and a passage in Liebig’s A nim al C hem istry taken over from earlier p u b ­ lications: [R]espiration is the falling weight, the tensed spring, that keeps the clockwork [of the body] in motion; the breaths are the strokes of the pendulum that regulate it. We know with mathem atical precision for our ordinary clocks the alterations exerted on their regular m otion [Gang] by th e length of the pendulum or by external tempera­ ture, but only a few clearly recognize the influence that the air and temperature exert on the state of health of the human body. Yet discovering the conditions for maintain­ ing it in the normal state is not more difficult than for an ordinary clock.404

Valentin, in reporting Liebig’s views on anim al h eat, asked the reader to consider th e organism as a m achine in which the am o u n t of h eat produced depends on the com bustion of fuel,405 His elaboration of this m etaphor two years later in the

introductory section of his Textbook o f Physiology (1844) nicely signals th e way in which broad-based general changes in physiological thinking had com plicated its significance: “O rganism s have already often-—an d indeed from very diverse points of view— been parallelized [parallelisirt] with m achines or o th er artificial contriv­ ances th a t h u m an beings are capable of m anufacturing, w ithout, however, the friends of this view having been able to com pletely sustain the com parison, b u t w ith o u t its o p p onents, who often th o u g h t to see in such endeavors only th e prod­ ucts of a crude m aterialism , having been able to expose it as com pletely inappro­ p riate.”406 A lthough Valentin did no t so p u t it, the difference was th a t now m ore people were asserting, or were seen to be asserting, th a t organism s are m achines, hence th e greater need to specify th e range of validity of th e likeness. T he sim ilar­ ity he stressed was th e fact th a t for bo th m achines and organism s th e m anifesta­ tion (or exertion) of force (Kraftauperung) depends on th e consum ption of fuel, for which th e steam engine provides an especially tren c h en t analogy.407 T he rela­ tive coarseness of hum anly constructed m achines vis-a-vis th e m icroscopic fine­ ness of organism s need n o t weaken th e analogy, b u t rath er can be taken as evidence of “th e infinite skill of th eir creator.”408 V alentin’s use of the steam -engine analogy probably reflected Liebig’s influ­ ence. Alluding to its ingenious purposive activity, Liebig had been one of the earliest to invoke the im age of th e organism as a steam engine: “A no t entirely inappropriate im age for w hat goes on in the anim al body is provided by self­ regulating steam engines, for which th e h u m an m ind has shown th e m ost am azing ingenuity for th e production of uniform m o tio n .”409 Significantly, a later, m ore elaborate analogy betw een organism s and steam ships suggested in addition the indispensability of rational, purposive guidance: b o th have a m otion-producing source of heat and force in th e food or fuel consum ed, and just as th e ship is kept in repair th ro u g h th e activities of the skilled crew, so, too, is th e living body m ain­ tain ed by its own carpenters, blacksm iths, an d locksm iths.410 As we have seen, the idea of an active vital force had a strong hold on Liebig’s im agination. T h e first person to insist upon this kind of imagery seem s to have b een Liebig’s rival, Jean-B aptiste D um as, who in a frequently reprinted lecture of 1841 spoke of anim als as “producers of h ea t and of force, veritable com bustion devices.”411 As already n o ted, D um as suggested th a t “the poetic assim ilation of th e railroad loco­ m otive to an anim al rests on a m ore serious foundation th a n one perhaps th o u g h t.”412 Indeed, several authors have argued th a t technological change in W estern Europe, in particular the advent of railroads, stim ulated th e develop­ m en t of a new way of thinking, of regarding n atu re as (in H erbert Breger’s words) a “working m ach in e.”413 M any cam e to think of m achines in term s of their capac­ ity to do work. For Breger, th e m echanical tradition, which increasingly h ad com e to m easure perform ance in term s of th e height to w hich a weight could be lifted, was an im p o rtan t elem en t in M ayer’s conceptual background: Mayer, he noted, referred repeatedly to th e m echanical effect (Nutzeffekt) of m achines, horses, and people, and m easured the work done by th e lifting of a w eight.414 Breger sought to d ate this conceptual break in people’s view of the world to the years after 1830, when there was growing awareness of th e radical im pact of th e burgeoning indus-

trial revolution.41’ Indeed, an anonym ous article from 1842 on the founding of physiological in stitu tes characterized th e tim es in term s of th e restless whirl of daily events and th e “roaring of steam engines.”416 H erm ann Schlriter’s study of n in eteen th -cen tu ry biology paid particular a tte n tio n to the m etaphor of organism as m achine; he, too, singled o u t th e railroad as th e m ost im p o rtan t transform er of consciousness. S chluter cited H enrich S teffens’s im pressions of th e profound ef­ fect of th e railroad on people’s im agination after around 1830, and qu o ted physi­ ologist Carl Ludwig’s D um as-like recollection of the im aginative im pact th e rail­ road locom otive h ad h ad on his science: “For th e first tim e there was constructed w ith this m achine a self-acting m echanism in which th e interplay of forces took shape transparently enough to discern the connection betw een the h ea t gener­ ated and th e m otion produced. T h e great puzzle of th e vital force was also im m e­ diately solved for th e physiologist in th a t it becam e evident th a t it is m ore th an a m ere poetic com parison w hen one conceives of th e coal as the food of the locom o­ tive and th e com bustion as th e basis for its life.”417 Given this com plex of images and attitu d es, one can im agine a kind of grafting o n to a m ore or less traditional post-C artesian picture of th e organism as an exqui­ sitely contrived m achine, of energetic considerations derived principally from steam engines and, in particular, locom otives. W h a t was the balance betw een fuel, waste products, and the h eat and work produced? If, to be sure, such general changes in worldview and th eir influence on any given individual are notoriously difficult to pin down, the least one can say is th a t Mayer, growing u p during those tim es, show ed a deep and early interest in th e work perform ed by waterpowered m achines, and h e applied q u ite naturally and heuristically to organism s energetic considerations th a t derived from a general un d erstan d in g of steam engines.418 In th e 1830s natural theology and industrial technology b o th reinforced the tradi­ tional physiological m etap h o r of th e organism as a m achine— and R obert Mayer was well situated to b e affected from all three directions. 3.3 The Solar System as a Living Organism Even m ore widespread and m ultifaceted in th e G erm an scientific literature of the 1830s and early 1840s th an th e m etap h o r of organism s as m achines was th e anal­ ogy b etw een organism s and th e solar system , an analogy th a t harked back to the traditional com parison of m icrocosm to m acrocosm and drew force from th e ex­ planatory success of th e N ew tonian world system . An appreciation of th e perva­ siveness of th a t im age and of th e issues it entailed will go a long way in reducing th e apparent strangeness of M ayer’s understanding of th e dynam ics of centralforce m otions and his early belief, held even after the publication of his first paper, th a t force can b e created in organic systems, including th e solar system. O nce again th e developm ent of M ayer’s ideas depended strongly on the analogies he regarded as valid. Recalling A u ten rieth ’s extended analogies betw een processes whereby th e soul, th e vital force, th e im ponderables, or the force of gravitation are called into exis­ tence from a com m on preterphysical realm , one is n o t surprised to find him

am ong th ose w ho drew an analogy b etw een living organism s and th e solar system as con tainin g w ithin th em selves perpetual sources of m otion: B ut th a t p erpetual internal change in th e vital force presupposes . . . in this force itself a n o t fu rth e r explicable basis [G rund] th a t su stain s such co n tin u al d istu rb an ce in th e balance b etw een th e essentially interrelated an tith eses and does n o t allow th em to com e to equilibrium . In th e sam e way only a co n tin u in g source of all m o tio n , n o t an im pulse im p arted once in rem ote antiquity, m o st likely also explains th e co n tin u a­ tio n of th e m o tio n of all th e stars, th e sun, an d our earth, since space does n o t appear to be any kin d of absolute v acuum .419

Johann Carl Passavant, a practicing physician in Frankfurt am M ain w ho pub­ lished extensively on anim al m agn etism , advanced a similar claim in his desire to establish a link b etw een th e forces of organic and inorganic nature: O rganic bodies are principally distinguished from inorganic in th a t they are d eter­ m ined by an au tonom ous, purposefully acting principle. By m eans of th is au to n o ­ m ous principle they th e n also have th e capability to develop [sich zu entwickeln]. N evertheless, this d istin ctio n is n o t absolute. For n atu re in th e large— e.g., our solar system — also has such an autonom y. T h e m otive an d conservative forces are repro­ d uced in it; they are n o t given to it from th e outside. L ight an d gravity hold sway in th e entire visible world. . . . T h e universal powers of n atu re [allgemeine N aturpotenzen] th u s appear to us as universal processes of n atu re, an d th ese la tte r as functions of ou r planetary system , an d probably of o th e r solar system s, too. In th is view physics is no longer essentially divided from physiology. Just as every individual organism is a to tality in and of itself, an d at th e sam e tim e repeats in a d istinctive m a n n er th a t of a higher universal w hole, so, too, does it repeat, th o u g h w ith m odifications, th e u n i­ versal functions of th e planetary system th a t generates an d nourishes it. It follows already in general from this . . . th a t th e organic forces can only b e m odifications of th o se universal forces of n a tu re .420

L otze’s Lebenskraft article also broached this issue, though in a som ew hat am ­ bivalent fashion. In one place L otze den ied th e justness of an analogy b etw een organism s and the solar system , arguing th at whereas in such natural m echanical system s th e fundam ental forces of nature “call forth that self-preserving interplay of m otio n s of a perpetuum m o b ile,” organic b od ies are like artificial m achines “since they are in perpetual need of a new replenishm ent and im pulse for their m o tio n .”421 Later on, however, L otze m aintain ed that organism s and the solar system are alike in b oth ex h ib itin g a divinely ordered purposefulness. Even so, as he now con clu d ed from a consideration o f th e relationship b etw een th e soul (die Seele, das Ideale) and th e body, “th e organism n ot only pursues th e purposes [or ends (Zwecke)] p redestined by th e com b in ation of its m asses, but can set itself new purposes and is itself capable o f procuring the m eans conducive to their realization w ith an absolutely n ew initiation of m echanical m o tio n .”422 T h e design — or, in th e m ore Kantian term s used by L otze, the purposefulness ( Zweckmaf i gkei t)— exh ib ited by both living things and th e solar system was prob­ ably the m o st com m on ly insisted-up on sim ilarity b etw een the tw o m anifestations

of o rg a n iz a tio n . B u rd ach , for ex am p le, w ro te (in his “an th ro p o lo g y ” of 1837) of th e diverse b o d ie s m a k in g u p th e solar system : “T h e re is p u rp o sefu ln ess in th e ir p la c e m e n t su ch th a t ea c h m oves in its o rb it w ith o u t d istu rb in g th e o th e rs, an d insofar as th e in flu e n c e of th e su n over all p a rts o f th e e a rth is a p p o rtio n e d w ith a c e rta in u n ifo rm ity d u e to th e o b liq u ity o f th e e c lip tic, it resem bles a n organic arra n g e m e n t. T h e p la n e ta ry system th u s b ears in itse lf th e essen tial tra its o f th e o rg a n ic .”423 For th e R o m an tically tin g e d B u rd ach, th e force o f th is analogy was seem ingly to m ake th e w orld system in to a k in d of cosm ic organism ; in d e e d , he played u p th e N e o p la to n ic p arallelism b e tw e e n m ac ro co sm a n d m icro co sm .424 For V olkm ann, to o , w ho also em p lo y ed th e la n g u ag e o f m a c ro c o sm a n d m ic ro ­ cosm , th e likeness o f th e solar sy stem to a n o rg anism im p lies th a t th e u n iverse is also a living th in g (ein BeZefefes).425 F or th e m ore re d u c tio n ist-m in d e d S chw ann, on th e o th e r h a n d , very nearly th e sam e analogy served to m ak e living th in g s in to finely c ra fte d m a c h in e s. T h e p u rp o se fu ln e ss S ch w an n a d m itte d is n o t th e ex p res­ sion of a p u rp o sefu lly a c tin g organic force, b u t derives fro m “th e c re a tio n of m a t­ te r w ith its b lin d forces by a ra tio n a l b ein g , w herein also lies th e basis of th e p u rp o se fu ln e ss in in o rg an ic n a tu re . W e know, for ex am p le, th e forces th a t a c t in o u r p lan etary system . T h e y are forces th a t a c t acco rd in g to b lin d laws of necessity, like all physical forces, a n d y et th e p la n e ta ry sy stem is ex trem ely p u rp o se fu l. T h e basis for th e p u rp o se fu ln e ss does n o t lie in th e se forces, b u t in H im w ho so cre­ a te d m a tte r w ith its forces th a t in o b ey in g th e ir b lin d laws th e y n ev erth ele ss b rin g fo rth a p u rp o se fu l w h o le .”426 A lth o u g h th e lan g u ag e a n d in te n tio n w ere d iffere n t, S c h w a n n ’s physicalist p o sitio n was very close to th a t o f B ro u g h a m ’s n a tu ra l th e o l­ ogy: a fte r d escrib in g , as ev id en ce of d esig n , a n u m b e r of a n im a ls’ co n triv a n ce s for p e rfo rm in g c e rta in tasks, B ro u g h am c ite d th e sta b ility an d regularity o f th e solar system as likew ise ev in cin g d esig n .427 H ere again varian ts o f th e sam e basic an al­ ogy co u ld b e em p lo y ed to very d iffe re n t ends. S c h le id e n ’s a d a p ta tio n of th a t analogy e c h o e d th e sp irit o f S ch w an n ’s deo rg an icizing a n d d e sp iritu a liz in g u n d e rs ta n d in g of scien tific e x p lan a tio n . S ch leid en re jec te d th e n o tio n th a t o rg an ic a n d in o rg an ic b ein g s are radically a n d fu n d a m e n ­ tally d is tin c t, p referrin g in s te a d to find only g rad u al differences: The actual riddle of life breaks down upon closer consideration into two problems: 1) the construction of a system of motive forces that m aintain themselves in regular periodicity; 2) the construction of the process of configuration [Gestaltungspracess]. Thereby is embraced everything which even the unhandiest abstraction can desig­ nate with the word life, for such people who mix along the psychic [das Geistige ] into pure natural science warrant no consideration here; their wrongheadedness is dem on­ strated to them in the realm of philosophy. But the solution to the one as to the other of the just-described tasks does not at all fall within the limits of the organic. The first has already been solved through the construction of the solar system, which is only the simplest form of such a vital process.428 S ch le id e n d is tin g u is h e d th re e ord ers o f su c h o rg an ized system s: solar system s (th e sim p le st a n d m o s t in d e p e n d e n t), th e in d iv id u al p la n e ts, a n d in d iv id u al terrestrial

organism s, whereby he apparently followed th e lead of his m entor, Jacob F ried­ rich Fries, who h ad specified a parallel division.429 If S chleiden’s and Fries’s tripar­ tite hierarchies go beyond th e sim pler analogies of o th er w riters, they nevertheless effectively juxtaposed m icrocosm ic organism s and m acrocosm ic solar system s as belonging to parallel conceptual classes. They, too, challenged th e contem porary reader to reflect on th e essential sim ilarities and differences betw een those two all-im p o rtan t classes of beings. In th e view of several authors, just as we can know w ith great precision th e laws of planetary m o tio n w ith o u t know ing anything ab o u t th e origin of th e solar sys­ tem , so to o can we aspire to know th e laws of organic life even if its origin rem ains forever unknow n to us. It belongs to science to investigate laws, n o t origins. In his review of Karl W ilh elm Stark’s General Pathology, Lotze applauded R eil’s desire to explain vital p h en o m en a in purely physical term s, b u t criticized him for failing to recognize th a t no explanation of actually existing systems is possible solely on th e basis of know ledge of th e laws of action, w ith o u t know ledge also of th e p artic­ ular circum stances in w hich th e system finds itself, of w hat we would call the initial conditions. H e drove h om e his p o in t by referring to th e analogous situation th a t we are in w ith respect to our knowledge of th e solar system: For th e action o f th e sim p le fu n d am en tal forces is always only possible; u n d ecid ed as to different d irection s, it always acquires th e form o f its activity only from th e m ore precise co n d itio n s o f th e p h e n o m e n o n to b e fash ion ed , co n d itio n s w hich d o n o t lie in it. T h e force o f attraction . . . w ou ld ten d toward th e collap se of th e gravitating m asses in to a center; b u t in truth w e only see this process occur in nature in a subordinate way on th e surface o f th e individual h eaven ly b od ies, w hereas its realization in th e totality of th e system is im p ed ed by a tan gen tial velocity of that w hich is attracted, whereby a circular m o tio n is g en erated as th e true form of th e solar system . T h a t velocity, how ever, and th e corresponding arrangem ent of th e d istan ces are d eterm in ation s ac­ cording to w hich th e m ech a n ism co m es in to operation b u t w hich are n o t given in the m ech an ism itself.430

L otze reiterated this p o in t three years later in his own General Pathology, and again th e n ex t year in his Lebenskraft article. In th e la tte r work he recognized th a t alth o u g h science can only deal w ith th e general laws of existing systems, we never­ theless still desire to know th e origins of things. C o n fro n ted w ith th e choice b e ­ tw een chance or special creation, scientists have com e increasingly to reject the la tte r alternative as intrinsically unscientific: “T h e curiosity which w onders how in fact th e solar system or th e germ s of th e organic first cam e into being is, rather, accustom ed always to presuppose th a t it h ap p en ed th ro u g h som e chance m e­ chanical occurrence.” B ut, argued L otze, we u ltim ately can n o t avoid assum ing som e kind of divine creation in order to explain th e com plex and purposeful disposition of cosm ic and organic system s— organized m acrocosm and organic m icrocosm once again linked in term s of th eir organization.431 His position, too, cam e very close to th a t of natu ral theology. L eh m an n invoked th e sam e analogy betw een solar system and organism in de­ fending precisely th e sam e views in his Textbook o f Physiological Chem istry

(1842). W e have been able to discover th e invariable laws of m otion of the heav­ enly bodies— laws th a t allow the precise prediction of th e system ’s future behav­ ior— even though we m u st rem ain forever ignorant of how th e inscrutable prim um movens first im parted m otion to it. In th e sam e way we shall never know how a seed or an egg or a germ first cam e into being, “b u t we are not thereby prevented from investigating th e laws of th e organic m otions once initiated just as well as the regularity in th e continued m otion of th e heavenly bodies.”432 W e thus expect to find organic processes to proceed according to invariable organic laws. In a similar vein, Valentin likened the periodically recurring processes of self-preservation of th e “organic m ach in e” to th e law -bound organization of th e solar system .433 If the purpose of L otze’s and L ehm ann’s extended analogies was to defend a m echanis­ tic view of life, nevertheless their significance here is in the fact th a t th e m e ta ­ phoric assim ilation of organisms to the solar system was everywhere to be encoun­ tered in th e G erm an literature of the 1830s and 1840s; others, like Mayer, ex­ ploited th at analogy for different ends. Still an o th er analogy betw een th e solar system and living things h ad to do with th e association of straight lines, flat surfaces (such as th e faces of crystals), and straight-line m o tio n w ith inorganic systems, curved lines and surfaces and curvi­ linear m otion (such as th a t of th e planets) with organisms. W rote Karl W ilhelm G o ttlo b Kastner, professor of chem istry and physics at Erlangen: “C urvilinear m otions that, proceeding o u t from a point return to it and thus endlessly renew them selves, we call organic motions insofar as they did n o t arise as artificial pro­ ductions of willing [wollend] beings, b u t cam e into existence in the necessary course of th e activities of nature, and either exist only w ithin certain intervals of tim e or continue to exist beyond all determ inable tim e. To the first belongs the circulation o f humors of living higher anim als and h u m an beings, to the latter the visible motion o f the heavenly bodies.”434 A lthough he did n o t explicitly invoke the analogy with planetary m otion, Liebig expressed essentially th e sam e views in an im p o rtan t speech of 1856: “All of th e configurations of inorganic bodies are bounded by plane surfaces and straight lines, all of th e configurations of th e bear­ ers of organic activity are b o u nded by curved surfaces and curved lines; in organic bodies a cause m ust be active w hich bends th e straight line into a curve.”435 In the solar system , too, there acts a force which produces curvilinear m otion by con­ stantly deflecting bodies from straight-line m otion. M ayer and his contem poraries were th u s confronted w ith a richly elaborated set of analogies th a t conceptually u n ited the solar system and living organisms. T hus M ayer’s readiness to apply to living systems conclusions derived from his analysis of th e gravitationally controlled m otion of th e planets around th e sun— in partic­ ular th e creation of force— would have appeared to be entirely in harm ony with generally accepted views. Is the organism like a m achine, and hence incapable of creating force o u t of nothing, or is the organism like th e divinely disposed solar system, capable (as some believe) of calling force continually into existence? At different tim es M ayer drew inspiration from b o th possibilities. T he progress of his thinking depended crucially on the analogies he took to be significant at different tim es.

4 P h y s io l o g y a s a n O p p o n e n t o f M a t e r ia l is m

It has already beco m e clear th a t a large n u m b er of th e m ost im p o rtan t scientists am ong M ayer’s co n tem poraries— m en like A utenrieth, Muller, Schw ann, Liebig, and Lotze— all gave place to theological considerations in th eir physiological w rit­ ings. A lthough th e self-styled genre of natural theology was m ore characteristic of English th a n of G erm an-speaking writers, th e la tte r nevertheless evinced wide­ spread allegiance to its central line of argum ent: design— or, as th e G erm ans m ore o ften p u t it, purposefulness— proves th e n eed to assum e th e existence of a ra­ tional Creator. Also im p o rtan t in G erm any were argum ents of a m ore general ‘spiritu al’ nature; th a t is, if science, and in particular physiology, can d em onstrate th e existence of non m aterial agencies such as m ind, soul, or vital force, th e n a th e ­ istic m aterialism is proven invalid. T h e issue was som etim es p u t in th e m ore general term s of w hether forces are m erely properties of m atter, or w hether they, like th e soul or th e vital force, can exist in d ependently of m a tte r as a distin ct kind of entity. As Volkm ann p u t th e issue in 1837 in an elem entary handbook of an a t­ om y and physiology (in words in part already quoted): If w e design ate th e u ltim a te cau se [Grimd] o f a p h e n o m e n o n by th e n a m e force, th en a force m u st also underlie life [dem Leben zu m G run de liegen], o n e th at can appropri­ ately be called vital force. But op in ion s already divide here insofar as o n e d isp u tes w hat a force is. M aterialists co n fla te force and m atter in th at for th e m forces are n o th in g b u t properties of m atter itself. . . . Spiritualists proceed in th e op p o site fash­ ion: either th ey allow m atter itse lf to be prod u ced o u t o f force, or they at least regard force as in any case in d ep en d en t o f m atter, and assu m e an actual ex isten ce even w ith o u t th e filling o f space. A ccording to th em th e vital force is earlier than the organism and is related to it as cause is to effect. T h e spiritualist therefore also d istin ­ g uishes th e soul from th e body, and regards it in d e e d as th e cause o f all vital p h e n o m ­ ena, and as the architect o f its body, as Stahl ta u g h t.456

A nd like m any others, Volkm ann identified G od as th e original creator of organic forms: T h e original force [Urkraft] w hich called organism s in to ex isten ce co n tin u es to act, alb eit now on only a reduced scale. W e are th u s in a p osition to follow th e co n d itio n s u n der w hich th e original creation [IJrschopfung] takes place [sic]; th ey are air, water, h eat, and light, b u t th e essen ce o f th e force itse lf does n o t thereby b e c o m e clearer to us, for th e d eterm in in g ele m en ts are n o t th e creating force itself. T h e original force, however, is in G od, to w hom the natural scien tist returns just like th e th eologian , to b e sure in a different way, b u t w ith th e sam e n ecessity.437

T h e perceived m aterialism of science was of such concern to m any of th e reli­ giously m in d ed scientists of th e day th a t a m inor genre existed w hich addressed itself specifically to just th a t issue. Volkm ann, for exam ple, published a short work in 1838 en titled Physiology as O pponent o f the Doctrine o f the M aterialism o f the Identity o f the Body and the Soul. T h e central issue for Volkm ann was th e im m or-

tality of th e soul, b elie f in w hich fo u n d its m o st serious o p p o n e n t in th e m a te ria l­ istic a s su m p tio n th a t all th e p h e n o m e n a of life are a fu n c tio n of th e c o n stru c tio n a n d c o m p o sitio n of th e b o d y .458 H e b e g a n by c itin g som e of th e a rg u m e n ts in favor o f th e b e lie f th a t th e soul is n o th in g m o re th a n a m a n ife sta tio n of th e p h y s­ ical o rg a n iz a tio n of th e b rain : th e soul is u n d e n ia b ly c o n n e c te d to th e body, and we find a close c o rre la tio n b e tw e e n th e in te lle c tu a l c ap acities of an anim al an d th e co m p lex ity o f its n erv o u s system . M oreover, th e divisibility of th e soul, w hich w ould acco rd w ith its m a te ria l n a tu re , is su g g ested by th e ability of organism s to re g e n e ra te lo st p a rts a n d by th e in te lle c tu a l c o rre sp o n d e n c e b e tw e e n p a re n ts and ch ild ren . H e th e n re s ta te d th e m a te ria lists’ a rg u m e n t a g ain st th e ex isten ce of a corporeally in d e p e n d e n t soul b a se d o n an analysis of th e re la tio n sh ip b etw e e n force a n d m a tte r: A ccording to this system the word force is so m eth in g entirely idle if o n e d esignates by it som eth in g other than activity. Force in contrast to m atter, and w ith o u t m atter, is a con cep tion w ith ou t co n ten t, and just b ecau se force is n o th in g in and of itself it can also not be th e cause o f an activity. Every m aterial su b stan ce m ust, insofar as it exists, also be active, for an ex isten ce w hich did n ot m an ifest itself w ould n ot b e existen ce. A ctivity thus attaches im m ed iately to m atter, w hich w ith o u t b ein g active w ould not even exist. Every activity is therefore th e property originally pertaining to and insepa­ rable from m atter.439

T h u s o n ce again th e issue of th e ex isten ce of th e soul was in ex tricab ly c o n n e c te d w ith th e q u e s tio n of th e gen eral n a tu re o f forces: are th e y e n titie s sui generis, or p ro p e rtie s of m a tte r? O n ly th e first a lte rn a tiv e lends su p p o rt to b elief in an in d e ­ p e n d e n t (an d im m o rta l) soul. A gain st th e m a te ria list c o n c e p tio n of th e soul as sim ply a fu n c tio n of th e b rain, V olkm ann arg u ed th a t th e level o f an a n im a l’s in te lle c tu a l d e v e lo p m e n t does n o t in fact co rrelate d irectly w ith th e d e v e lo p m e n t of th e b ra in — w itness, h e said, stu p id fish c o m p a re d w ith clever bees. N o r d oes severe dam ag e to th e b ra in n eces­ sarily im p a ir a p e rso n ’s m e n ta l facu lties. As for th e p u rp o rte d divisibility of th e soul, h e c o u n te re d th a t w hereas th e division of m a tte r is always ac c o m p a n ie d by a co rre sp o n d in g division of all its p ro p e rtie s, th e psychic force (Seelenkraft) of each re g e n e rate d h a lf of a b is e c te d w orm is n o t less th a n th a t of th e original creatu re. V o lk m an n ’s ex am ples w ere n o m o re th a n o n e is a c c u sto m e d to find in th e G e rm a n physiological lite ra tu re of his day. W h a t decisively d e m o n stra te s th e differen ce b e tw e e n th e soul a n d th e physical forces o f n a tu re , a n d h e n c e su p p o rts th e in d e p e n d e n c e o f th e soul from th e body, is th e so u l’s sp o n ta n e o u s activity, its ability to in itia te o rganic m o tio n s w ith o u t b e in g b o u n d by th e im m u ta b ility th a t ch aracterizes th o se forces, an im m u ta b ility a tte s te d by th e co n sta n cy of th e m o v e ­ m e n ts of th e p la n e ts. N o r d id th e fact th a t b o d ie s’ active chem ical forces are capable o f c o m in g to rest in c h em ical c o m p o u n d s w eaken his g eneral co n c e p tio n of th e n a tu re of forces— forces in o u r sen se of th e word: “M a tte r acts by m e a n s of forces th a t it h a d fro m th e b eg in n in g , by m e a n s of c o n sta n t forces th a t c a n n o t decrease, m u c h less cease a n d b e g in .”440 T h u s V olkm ann’s physiologically b a sed a n tim a te ria lis tic a rg u m e n t for th e e x isten ce of th e soul finds h im assertin g th e

ind estru ctib ility and uncreatability of th e physicochem ical forces of n a tu re — w ith o u t, to be sure, his having h ad a clearly elaborated general concept of force, let alone of its m easure. V olkm ann’s essay repeated in large m easure th e m ain points of an article e n ti­ tled “Reasons against M aterialism ” published by A u ten rieth in 1816 in a scientific journal h e co ed ited an d reprinted in his posthum ously published work of 1836. T h e basic stan d p o in t was th a t m aterialism could be refuted by d em o n stratin g the existence of a soul in d ep en d e n t of th e body. A u ten rieth , like V olkm ann, based his arg u m en t on th e existence of free will an d on th e nondivisibility of th e soul during processes of gen eration and regeneration. Still a n o th er work in this genre was the A tte m p t to Prove the Im m ortality o f the Soul from the Standpoint o f Physiology (1830) by th e professor of m edicine at Bonn, M oritz E rnst A dolph N aum ann, w hich based its arg um ent on th e m anifestations of consciousness. T h ese works, along w ith related discusssions in m ost of th e m ore exclusively physiological works of G erm an scientists published in th e decades before around 1840, n o t only reinforced th e theological connections of physiology, b u t also th ru st into p rom i­ n ence th e issue of the dependence or indep en d en ce from m a tte r n o t only of the soul b u t also of forces. At least one kind of force, th e Seelenkraft, is n o t m erely a property of m a tte r b u t is an ind ep en d en tly existing en tity sui generis. W ith in such a co n tex t, M ayer’s vindication of force as such an en tity c o n stitu te d an o th er pow ­ erful arg u m en t against such a conception of m aterialism .

5 H om eopathy

T h e ad vent of hom eopathy, an alternative to th e drug-based trea tm e n ts of trad i­ tional m edicine, can b e identified w ith th e appearance of Sam uel H a h n e m a n n ’s Organon o f R ational M edicine in 1810. H a h n e m a n n ’s system won m any devoted followers, b o th lay and professional, an d aroused th e equally passionate o pposi­ tio n of m any “allo p athic” physicians, as H a h n em an n term e d th e practitioners of traditio n al m edicine. In 1834 th e new system found a new d efen d er in th e m ed i­ cally train ed professor of “practical philosophy” at T u b in g en , C arl A ugust von Eschenm ayer, who published a m o d est work en title d A llopathy and Homeopathy Compared in Their Principles. T h a t work elicited th e critical response of a n o th er T iib in g en professor, F erdinand G o ttlo b G m elin— at th e tim e one of M ayer’s m edical professors— who published a C ritique o f the Principles o f H om eopathy in 1835. H o m eo p ath y was th u s a controversial p a rt of th e m edical landscape during th e years of M ayer's schooling, and one can only assum e h e h ad som e know ledge of th e m ajor issues. H om eopathy was part of th e broad com m on co n tex t which involved physiology, m edical practice, ontology, theology, and th e spiritualist ph en o m en a of anim al m agnetism and som nam bulism . W underlich, in his H istory o f M edicine, n o ted th a t h o m eo p ath y h ad found favor w ith th e o p p o n en ts of m a te ­ rialism .441 In part this reflected th e m aterialistically co u n terin tu itiv e basis of h o ­ m eo p ath ic practice; in p art it h ad to do w ith th e fact th a t h o m eo p ath y ten d ed to

find support am ong those who also believed in such scientifically suspect p h e­ n om ena as anim al m agnetism and th e like.442 A lthough there is no evidence th a t M ayer was attra cted to or in any special way influenced by hom eopathy, nevertheless several of the central issues were pre­ cisely those already identified as im p o rtan t aspects of his conceptual background, nam ely th e relationship betw een cause and effect, th e nature of force, and the refu tatio n of m aterialism . T h e debate concerning hom eopathy thus m ay well have co n trib u ted som ething to M ayer’s awareness of such conceptually loaded topics. H om eopathy was a p art of th e stage-setting context of M ayer’s intellectual m ilieu, even if one cannot say w ith any assurance th a t he atten d e d to th a t com po­ n e n t of his surroundings. For Liebig, th e plausibility of hom eopathy reflected people’s confused notions of force, cause, and effect. As he wrote in the first of his new series of “C hem ical L etters” in 1844: “W ith o u t correct conceptions of force, cause, and effect, w ith­ o u t practical insight into th e essence of th e phenom ena of nature, w ithout a thorough physiological and chem ical education, is it a w onder th a t otherw ise rea­ sonable people defend the m ost absurd views, th a t H ah n em an n ’s theory could arise in Germany, th a t it could find pupils in all countries?”443 T h e acuteness of these issues stem m ed from the fundam ental te n e t of hom eopathy th a t properly prepared dosages of extrem e dilution are m edically m ore powerful th a n the relatively large doses custom arily adm inistered. (The h o m eopathic p o ten tiatio n [Potenzirung] of th e substance was achieved by prescribed shaking of th e progres­ sively d iluted solutions.) Eschenmayer, for one, argued th a t das Q uantitative (rep­ resented by gravitation) and das Q ualitative (representated by heat) oppose each o ther in an inverse relationship: gravitation seeks to bind, h eat to release, and as th e hom eopathically active substance is progressively divided— its bulk d e­ creased— so m u st its qualitative (medical) action increase.444 T his phenom enon is an exam ple of th e general law “th a t th e q uantitative and qualitative elem ent stand in an inverse ratio.”445 A rem ark o f E schenm ayer’s to his close friend Justinus Kerner in 1838 suggests n o t only th e centrality of th a t contested doc­ trine, b u t th e extent to which th e T ubingen m edical establishm ent regarded h o ­ m eopathy as worthy only of ridicule: “At the university (T ubingen), where wigs have n o t yet long been p u t aside, the victory still belongs to the pill boxes, herb presses, and heavy-bodied m ixtures. To w ant to cure a robust m achine with a m illionth of a grain these m en call a piece of foolishness, and they also perm it them selves th e sarcasm th a t hom eopaths will eventually succeed in teaching peo­ ple to b ath e in th e th o u san d th part of a drop of water.”446 In countering w hat an anonym ous au th o r recognized is “th e inconceivability of th e effectiveness of such small doses,” defenders of hom eopathy typically appealed to experience.447 To defenders of th e system, hom eopathic physicians are th e true em piricists, who refuse to let theoretical preconceptions blind th e m to th e tru th s of experience. In an a tte m p t to render th e inconceivable a little m ore plausible, analogies were enlisted from well-known phenom ena about th e ability of small physical and chem ical causes to produce large effects:

Even in so-called dead nature th e sm allest, m o st invisible su b stan ces o ften produce th e greatest effects. W lrercas a glass is n ot dam aged by th e lo u d est sou n d , an insignif­ icant to n e h aving a particular harm ony w ith it o ften cau ses it to exp lod e. S teel and sto n e lie peacefully on gunpow der, b u t a strobe of th e first tw o against each other m elts sm all steel spheres (sparks) w ith th e h ea t, w h ich [then] p rod u ce a h u g e ex p lo ­ sion or a d evastatin g fire. In th e m o st in sign ifican t q u a n tity of silver fu lm in a te there slum bers th e m ost prodigious p rod u ction of force, w h ich n o on e su sp ects there and w h ich co m es in to b e in g by m ean s of an in sig n ifica n t friction '.448

As for th e vanishingly sm all w eight of h o m eo p ath ic dosages, H a h n em an n pointed o u t th a t physicists accept th e existence of “prodigeous force en tities (powers) [ungeheure Kraftdinge (Potenzen)] . . . w hich are entirely w ith o u t w eight— for ex­ am ple th e substances of heat, light, etc.— and w hich are th u s still infinitely lighter th a n th e m edicinal c o n te n t of th e sm allest dosages of hom eopathy.”449 N or was th a t all. R ecalling th a t th e p o te n tia te d h o m eo p ath ic dosages are prepared n o t just by progressive d ilu tio n b u t u n d er th e acco m p an im en t of a prescribed am o u n t of shaking, a d efen d er of hom eopathy invoked th e fu rth e r physical analogy of the ability of friction to evoke large q u an tities of force: For th e rest, th e effectiv en ess o f th e sm all h o m eo p a th ic dosages b e co m es all the moTe explicable w hen o n e considers their preparation and th e co n d itio n s under w hich they act. Infinite forces are produced in nature and transferred from o n e b od y to another through friction. T h erefore if (say) a m a g n et m akes iron m a g n etic through friction, or a con tag io n c o m m u n ica tes itself to other b od ies, why sh o u ld n ’t m ed icin al forces also co m m u n ica te th em selv es through friction equally w ell to u n m ed icin al m ilk sugar or spirits o f w ine? T h e h o m eo p a th ic dilutions are th u s also im properly so term ed , sin ce they are at th e sam e tim e a generation o f force, a c o m m u n ica tio n o f force. H o m eo p a th s therefore also prefer to u se th e expression (for exam p le) third or th irtieth development o f force or p o ten tia tio n . . . . C o u n t Rum ford h ea ted room s by m ean s o f th e rapid friction o f m etal plates, e tc .4>0

In its innocence of any in tu itiv e n o tio n of th e conservation of q u an tity of m otion, such a defense of th e plausibility of h o m eo p ath ic rem edies was n eith er m ore nor less unreasonable th a n Liebig’s explanation of putrefaction and ferm en tatio n in term s of th e propagation of m olecular m o tio n s.451 G m elin was especially critical of th e h o m eo p ath ic principle th a t th e m edically effective stren g th of a substance increases w ith decreasing con cen tratio n , espe­ cially since th e d ilu tio n is typically so extrem e. O u r usual experience, h e co u n ­ tered, is th a t th e quality expressed by a m aterial substance decreases in propor­ tio n to th e am o u n t present, at least u p to a point. Below a certain concentration, contagions cease to b e able to cause disease an d frog sem en ceases to be able to fertilize eggs, and th ere are lim its below which small q u an titie s of electricity, sound, and light can no longer b e perceived:452 “A ccording to th e foregoing there are th u s extraordinarily fine m otions of the im ponderables, and otherw ise im per-

ceptible m inim a of ponderable m atter, which still produce a reaction in dead and living bodies, b u t even w ith these it is evident th a t the reaction is stronger and the effect greater w ith a greater qu an tity th a n with a lesser, and th a t every kind of reaction ceases at a certain lim it of division and fineness, a lim it which occurs m uch earlier th an the H ahnem annian dilu tio n .”4’3 Alongside the issue of the q u an titativ e relationship betw een cause and effect, G m elin has raised the possi­ bility of th e disappearance of an effect once th e cause has becom e sufficiently small.

6 S ummary

However m uch a variety of factors influenced th e course of M ayer’s intellectual developm ent, th at he was trained as a physician was th e central im p o rtan t fact of his background w ith regard to understanding his route to som ething like th e con­ servation of energy. T h e crucial influence of th a t m edical background was roughly speaking twofold: it prepared him to observe and react to th e anom alous color of th e blood he let in the tropics, the event th a t set off his unstoppable train of reflections, and it provided him w ith a rich context of issues concerning th e on to ­ logical status of forcelike entities, in particular their possible creation an d destruc­ tion. It was those issues, I believe, th a t led him to transform a lim ited conviction concerning th e quantitative equivalence of h eat and m otion into a global theory ab out a new conceptual entity, force. Since it has been the purpose of this long ch apter to lay o u t the full richness of th a t m edical and physiological context in order to dem o n strate just how profoundly M ayer was connected with im p o rtan t and highly visible issues of th e day, it m ay be useful to sum m arize its principal findings in a few pages. As the them e of this book has em phasized, th a t context defined several fields of m eaning w ith respect to which M ayer defined the issues and solved th e problem s of central concern to him . It is im p o rtan t to recognize th a t although we see the issues of the color of the blood, th e n ature of respiration, and th e sources of anim al h eat as intim ately connected, in M ayer’s day they were by no m eans all regularly considered in the same context. At th e same tim e, each issue alone was m ore com plicated and u n set­ tled th an would be th e case after a theoretical consensus had allowed th e separa­ tio n of essential from nonessential factors. T hus in the 1830s th e color and physi­ ological function of th e blood were n o t clearly or universally connected in th e first instance w ith respiration and the generation of heat: th e presence of saline m atter was widely held to influence th e blood’s color, and its essential functions included th e removal of excess carbonaceous m atter from the body in an excretory process u n co n n ected w ith the problem of anim al heat. Indeed, it was th a t excretory func­ tion th a t probably shaped M ayer’s initial expectations. According to a widely held view, th e dim inished oxygen co n ten t of warm air m eans th a t less carbon will be removed from th e blood via respiration, im plying th a t such blood will be darker th a n norm al. Such seems to have been M ayer’s expectation. At the sam e tim e, the body was supposed to com pensate by increasing th e production and secretion of

bile pro d u ced in th e liver from th e venous blood passing th ro u g h it— a com ple­ m entary process th a t underscored th e excretory fu n ctio n of th e oxidation of car­ bon in th e blood. To be sure, th e pro d u ctio n of anim al h e a t was m ostly ascribed to an oxidation process involving th e blood, b u t discussions of th a t issue were typically in d ep en d e n t of th e foregoing kinds of considerations— th a t is, they were in d ifferen t works or in different parts of th e sam e work. AU th ro u g h th e 1830s factors o th er th an oxidation were also th o u g h t to c o n trib u te to th e pro d u ctio n of anim al h ea t, m o st notably th e influence of th e nervous system . O nly gradually in th e course of th e d ecade did th e increasingly taken-for-granted conviction th a t all physiological processes m u st b e u n d ersto o d in term s of underlying processes of m aterial exchange begin to u n d e rc u t th e validity of such supposed additional sources of h eat; and even at th a t, it was still only gradually, during th e late 1830s and 1840s, th a t G erm an scientists becam e generally sensitive to issues of w hat one m ig h t call ‘energetic causality.’ For som e, th e organism m ight well b e a kind of p erp etu u m m obile. D u lo n g ’s and D esp retz’s universally know n findings— th a t respiratory oxidation cannot account for all of th e h e a t produced— seem ed to give experim ental w arrant to th e no n accep tan ce of th e sufficiency of Lavoisier’s th e ­ ory. T h u s it was a radical and decisive step for D um as and Liebig to com e o u t w holeheartedly in favor of th e oxidation theory of anim al h ea t in 1841 and 1842, a step n o t m o tivated by new experim ental findings b u t by a new theoretical con­ ception of physiological processes. T h u s, too, in 1840 it is highly unlikely th a t M ayer m ad e his initial b lo o d lettin g observations from th e stan d p o in t of th a t th e ­ ory; rather, it seem s m ore likely th a t he cam e quickly to accept th a t theory in part because it h elp ed h im m ake sense of his anom alous observations. T h e oxygen theory of anim al h eat was n o t M ayer's starting point, b u t an early conclusion from his developing train of reflections. A few generalizations can be m ade ab o u t th e status of th e vital force as an issue relevant to th e em ergence of th e concept of th e conservation of energy during the 1840s in Germany. Always open to criticism as being m erely a verbal cover for o n e’s ignorance of th e real causes of organic ph en o m en a, from th e m id-1830s on th e vital force was in clear retreat from th e advancing front of organic chem istry as th e special agency responsible for th e synthesis of com plex organic com pounds. Up u n til around 1839-40, though, less w idespread th a n a principled general rejec­ tion of th e vital force was th e growing consensus th a t th e task of physiology is to explain vital p h en o m en a in term s of processes of m aterial exchange. (T iedem ann and M uller are good exam ples of this position.) And as physiology proper cam e m ore an d m ore to exclude issues of developm ent— especially involving cross-spe­ cies com parisons— in favor of a narrow er science of th e organic functions of th e (tacitly) already developed single organism , physiologists no longer n eeded to in­ voke a special organic (or as M uller p u t it, organizing) force to explain a class of p h en o m en a for w hich they no longer accepted responsibility. Freed, as it were, of th a t in tractab le explanatory bu rd en , physiologists now h ad only to deal w ith th e m ore plausibly physicochem ical functions of th e erstw hile vital force. H avinglong b een a topic of discussion and deb ate, after around 1839 th e vital force becam e a co n ten tio u s issue am ong G erm an scientists in ways it h ad n o t b een during th e

preceding decades, even as its defenders becam e fewer and fewer. In m any ways it was Liebig who b ro u g h t th e issue to a head by claim ing for th e vital force an unprecedentedly large and explicit role in th e production of organic m otions, a position m ore glaringly at odds w ith th e general tenor o f scientihc th in kin g than th e m ore traditional reliance on th e vital force to explain processes of generation and developm ent. A t th e sam e tim e, Lotze spoke ou t in favor of lim iting physio­ logical laws and explanations to those sanctioned by physics and chemistry, a position w hich would win an increasing num ber of adherents as th e decade wore on an d w hich left little room for any kind of special vital force. Ironically, th e otherw ise opposing positions of Liebig and Lotze provided equally fertile ground for th e germ ination of an awareness of th e im plications of th e absence of some kind of energy conservation principle. Liebig’s w ork-perform ­ ing vital force and L otze’s variable organic force b o th grossly violated th e feeling m any scientists had long held, in appropriately circum scribed realms, th a t n o th ­ ing can be created from nothing, th a t a physical effect m u st be assignable to a bona fide physical cause. If H elm holtz was m isleading in claim ing th a t h e had b een reacting against th e “vitalists” of his youth, nevertheless th e context sur­ rounding th e issue of vital force had never been m ore conducive to energetic reflections th an it was during the first half of th e decade of the 1840s.454 M ayer’s 1845 book, Organic M otion in Its Connection with the Exchange o f M atter, re­ flected this new state of affairs. Significantly, th e vital force h ad not been a problem atic issue for M ayer in the progress of his thinking, from m id-1840 to early 1842, leading up to his first p u b ­ lished paper, th e “Remarks on th e Forces of Inanim ate N ature.” In part this re­ flects th e relatively uncharged atm osphere surrounding th e issue as of around 1840; in part it reflects M ayer’s decision, in his earliest papers, to exclude the organic realm from consideration; and in part it has to do with th e fact th a t M ayer followed o ther routes to his theory of force, as will be laid ou t in chapter 6. Never­ theless, although principled criticism of the vital force did no t, I believe, play a significant role in M ayer’s earliest reflections, a num ber of the issues regularly raised in discussions of th e vital force, as part of the broader com m on context indentified here, were directly relevant to the kinds of issues th a t did occupy M ayer’s thoughts. For exam ple, discussions frequently touched on th e general issue of w hat characterizes a scientifically legitim ate concept of force, and w hether or n o t th e vital force m eets those criteria. Are forces properties of m atter, or can they have some kind of in d ep en d e n t existence? W ith the significant and idiosyncratic exception of A utenrieth, alm ost everyone denied the latter possibil­ ity; b u t th e issue was engaged. Similarly broached was the question of w hether or n o t th e vital force can be created (at birth) or destroyed (at d eath ), of w hether anything can be created ou t of nothing, of w hether (as som e m aintained) the vital force is capable of indefinite self-m ultiplication. Such issues were precisely those th a t engaged M ayer’s early atte n tio n as he struggled to forge a coherent concep­ tion of a new physical entity, force. O f perhaps secondary im portance here were attem p ts to liken th e vital force to chem istry’s catalytic force, an assim ilation th a t depended on th e suppression of

energetic considerations as it suggested th a t th e vital force, too, m ig h t be in ter­ pretable in term s of th e properties of appropriately arranged m atter. (T he cata­ lytic force will be d ealt w ith at greater len g th in ch a p te r 4.) O f great significance to M ayer was th e fact th a t th e growing tendency to rein terp ret th e increasingly disreputable vital force in term s of th e arran g em en t of organic m a tte r raised the specter of m aterialism , and m ade his relationship w ith his self-assertively progres­ sive co n tem poraries som ew hat problem atic. Indeed, m any G erm an physiologists had, u p till th e end of th e 1830s, seen physiology as an o p p o n en t of m aterialism , and it is clear th a t M ayer saw his co n cep t of force as p art of th a t tradition. T h ese discussions o ften involved th e soul in ways entirely parallel to th o se of th e vital force: Is th e soul an au to n o m o u s entity? C an it (or th e psychic force) be created? D oes it g en erate itself? W h e re does it go upon th e death of th e individ­ ual? W h a t is its relationship, substantive or analogical, to th e general forces of n atu re and to th e vital force? A fu rth er im p o rtan t issue w hich concerned th e soul in p articular was w h eth er it (or the nervous system ) can by itself in itiate (and perhaps sustain?) anim al m otions. W h a t is th e relationship betw een cause and effect here? W h a t is th e relationship betw een th e m ag n itu d e of th e cause and the m ag n itu d e of th e effect, an d how is eith er to b e estim ated? Q uestions of this natu re, widely discussed in th e physiological lite ratu re— or at least strongly im ­ plied by th e issues th a t were discussed— were, I believe, an im p o rta n t part of the co n tex t w ithin w hich M ayer shaped his own conception of force as a distinct en tity capable of n eith er creation nor destruction. As I have show n, th e physiolog­ ical literatu re co n tained a rich consideration of analogies am ong the im p o n d er­ ables, th e vital force, and th e soul: How are they similar, an d how are they dis­ tin ct? M uller, for exam ple, defended a con cep tio n of th e vital force as an entity sui generis, n o t reducible to chem ical and physical forces, b u t w hich like heat, light, and electricity can exist in m a tte r in a la te n t form . Significantly, b o th M u ller’s n o tio n of th e latency of th e vital force an d A u te n rie th ’s im age of its passage to an d from a preterphysical realm are tacitly prem ised on th e absurdity of assum ing th e creation de nihilo or th e d estru c tio n ad nihilum of (vital) force. Recall, too, th a t for a period of tim e M ayer wavered term inologically betw een “force” and “im ponderable": he created his conception of force less by rejecting th e im ponderables th an by rein terp retin g th e n atu re of th e ir “su b stan tiality ” and by exten d in g th e ir scope to include m otion. M uch of M ayer’s own thin k in g was guided by his search for valid analogies— for exam ple, b etw een force and ponderable m a tte r in term s of roughly th e sam e is­ sues others h ad applied to th e relationship am ong th e im ponderables, th e vital force, and th e soul. A second im p o rta n t guiding analogy, also w idespread in the physiological lite ratu re of th e day, was th a t of th e organism as a m achine. Indeed, th a t im age was also dear to authors w riting in th e trad itio n of natural theology, for w hich M ayer m ay have h ad an ear. A lthough M ayer’s antim aterialism kept him from believing th a t th e organism is n o th in g b u t a m achine, his willingness to treat it as a m ach in e w ith regard to its ability to perform work an d produce h e a t as a result of physiological processes th a t are them selves essentially chem ical was a necessary co m p o n en t of his initial d ed u c tio n of th e equivalence betw een h e a t and

m o tio n . (Part of th a t d e d u c tio n also drew u p o n his ch ild h o o d failure to c o n stru c t a p e rp e tu u m m obile.) L ater on , a th ird c o m m o n m e ta p h o r— th a t of th e solar system as a living o rganism — e n co u rag ed M ayer to accep t th e possibility th a t force m ig h t well be cre a te d in n o n m e c h a n ic al “org an ism s,” a conclusion rein­ forced by a c o m m o n general d istin c tio n b e tw e e n m ech an ical an d dy n am ic (or organic) system s an d ren d ered all th e m ore plausible insofar as M ayer d id n o t begin w ith a p rin cip led rejectio n of th e n o tio n of a vital force, a co n cep t only th e n just co m in g u n d e r increasing critical scrutiny. M ayer’s c o n te x t supplied h im w ith rich if m u tu ally in c o m p a tib le analogies; an essen tial p a rt of his creative process was to id en tify for h im se lf th e valid analogies, a difficult task w hen one keeps in m in d th a t h e was n o t so m eh o w d e stin e d to proceed m o n o to n ically tow ard th e conserv atio n o f energy. H is u ltim a te ly decisive rejection of th e vital force was an integ ral p art of an e x te n d e d process of clarification: it was n e ith e r sim ply th e sta rtin g p o in t n o r sim ply th e en d p o in t of h is in tellec tu al journey, p a rt of w hich involved d e cid in g w h a t kinds of things his new th eo ry of force w ould apply to. W ith o u t in sistin g o n its im p o rta n c e , th is c h a p te r has also looked a t h o m e o p a ­ th y as a n o th e r p o te n tia l c o m p o n e n t o f M a y e r’s m edical c o n te x t th a t m ay have b ee n relev an t to th e course of his th in k in g . T h a t is, th e controversies aro u n d this d o c trin e — w hich were active in T u b in g e n at ju st th e tim e M ayer was a m edical stu d e n t th e re — b ro u g h t to th e fore issues of th e relatio n sh ip b e tw e e n cause and effect, th e n a tu re of force, an d m aterialism th a t m ig h t conceivably have fu rth e r stim u la te d his th in k in g on th e se im p o rta n t general issues.

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C H A P T E R

F O U R ·

Physics and Chem istry

A l t h o u g h th e im m ediate co n tex t of M ayer’s initial reflections was physiologi­

cal— in th e broad sense of the term as th e n u n d ersto o d — h e carried w ith h im a residue of his childhood fascination w ith m achines an d th eir capacity to do work, he h ad b een well train ed in chem istry, h e h ad taken one course in physics at th e university, an d he early on tu rn e d his a tte n tio n to physics in an a tte m p t to secure a physical fo u n d a tio n for his developing conception of force. C en tral to M ayer’s thinking, moreover, were an analogy betw een m a tte r and force an d a parallel con­ ception of chem istry as th e science of m a tte r and physics as th e science of force. It th u s behooves us to have a clear sense of how his contem poraries dealt w ith the relevant concepts of force, m atter, and th e im ponderables. Alas, M ayer en co u n ­ tered m ostly confusion an d co n trad ictio n in contem porary texts and com pendia concerning th e co n ceptual and ontological statu s of forces and im ponderables, and he sp en t several years trying to work his way to co n sisten t clarity. In w hat follows I have paid prim ary a tte n tio n to G erm an works of th e 1830s, th o u g h I have exten d ed th e survey to include a few French an d English works, in particular th o se M ayer consulted, such as Lam e, Biot, W hew ell, a n d H erschel. A lthough, w ith th e exception of G eiger’s H andbook o f Pharmacy, there is no direct evidence u n til several m o n th s after th e appearance of his first published paper th a t M ayer had read any particular text, for th e m o st part th e works th e n generally available were in su b stantial agreem ent ab o u t th e m ost im p o rta n t relevant issues. It is, therefore, for th e m o st part of no great consequence th a t we do n o t know in m ore detail w hat he read w hen, although in ch ap ter 6 I will argue th a t M ayer h ad Fries’s Textbook o f Physics on board th e Java w ith him , a work th a t was different from th e no rm in certain im p o rtan t regards. A m ong th e m any features com m on to G erm an works of th e period was a con­ ceptual division of th e world of physics into m a tte r an d force. A lthough M ayer offered a p rofound re in terp retatio n of th e m eaning of th a t distinction, th e m atter-force dichotom y itself was a com m onplace. M u n ck e’s H andbook o f Physics was entirely typical: “As th e object of our investigation, th e com plex of everything affecting our senses is called nature. W e thereby distinguish m a tte r and force, and call m a tte r th a t w hich is know able through th e senses and w hich fills space, w hereby we distinguish it . . . from an effect produced and from th e forces pro­ ducing th e effects.”1 In his articles on “Physics” and “M a tte r” in Q ehler’s Physical Dictionary, M uncke essentially repeated this form ula, adding th a t “if one adm its th at, w ith th e exception of everything pertaining to th e world of spirits, no force can exist autonom ously, th e n all of n atu re, or th e corporeal world, offers only m a tte r w ith d ifferent forces peculiar to it.”2 F ischer’s Textbook o f M echanical Physics ad ded an epistem ological tw ist to this standard distinction: “In th e inner

being of every body there lie inseparable m otive forces, nor can we in reality w ithdraw any body from th e influence of external m otive force. But since we are com pelled by a necessity lying in th e inner being of our conceptual faculty to distinguish matter and force, we can thus also separate th e m in th e idea, and we m u st do so for th e sake of theory.”5 E isenlohr’s characterization of th e subject m a tte r of physics was entirely typical of w hat was to be found in m ost texts of the day: Everything we perceive through our senses is called body or matter; everything that causes a change, force. Physics is thus the science o f the causes or forces th a t determine the phenomena a n d changes th at take place in inorganic nature. T h e p h en om en a of nature take place according to d eterm in ate rules th at w e call laws o f nature. T h e u ltim a te causes of th ese p h en om en a are called fun dam en tal forces, and th ose laws o f nature that, according to exp erience, express th e sim p lest know n effects of these fund am en tal forces are called fu n da m en tal la w sd

Even this brief p resentation of m a tte r and force as th e two fundam ental con­ ceptual elem ents of physics has touched upon two of th e m o st general and im por­ tan t characteristics of force: forces are th e causes of change in th e physical world (especially of m otion); and forces (unlike das Geistige) have no ind ep en d en t exis­ tence in n ature, b u t are properties of m atter. T h e goal of physics is to discover the laws th a t em body the effects of th e m o st basic forces. T hose forces, however, did not usually include th e so-called im ponderables— heat, light, electricity, and m ag­ netism . T h e issues are com plex and im portant; let us consider in tu rn th e three basic classes of force, th e im ponderables, and m atter.

I F orce

C onsidering th a t M ayer believed he could prove th e tru th of his doctrine of force by invoking th e axiom s “forces are causes” and “cause equals effect,” it is of great significance th a t statem ents to th e effect th a t “forces are causes”— in particular th e causes of motion— were part of virtually every trea tm e n t of force M ayer m ight have read.5 Indeed, M ayer com plained to his friend Baur th a t physics texts treated force as an “obscure cause of m o tio n .”6 He cited Baum gartner, who had w ritten: O ften the cause [Ursache] o f a p h en o m en o n is itself in turn a p h en o m en o n , and thus requires a new cause [Grund]. If it is present in experience, th e latter presup­ poses in turn a new cause, such th at, via a series of p h en om en a of w hich each is sim ultan eously cause and effect, on e u ltim ately com es to a final supersensible cause that has its roots in th e interior of nature. O n e calls it force, w ith o u t w ishing to desig­ nate w ith this expression m ore than a cause of a p h en o m en o n that is in its essen ce com p letely unknow n to u s.7

M ayer also quoted Lam e, in French: “O ne gives the nam e force to every cause th at is capable of taking a body from the state of rest to one of m otion, or of producing th e inverse effect.”8 And he cited Fechner’s edition of Biot for likewise stating th at “every cause th at is capable of transposing m atter from th e state of rest to th a t of m otion is called force.”9 Eight or ten m onths later, m another letter to Baur, M ayer broached the subject again, this tim e citing from th e G erm an edition of W heweH’s Elementary Treatise on Mechanics. O ne passage he referred to read, in th e original: “A ny cause which moves or tends to move a body, or which changes or tends to change its motion, is called f o r c e . ” 10 In another place cited by Mayer, W liewell had w ritten th at “no change can take place w ithout a cause, and th at causes are measured by their effects."u In another English work M ayer owned in G erm an translation, H erschel’s Trea­ tise on Astronomy, th e author characterized astronom y as “a science of cause and effect.”12 In his chapter on gravitation he attacked the “attem pts . . . m ade by m etaphysical writers to reason away th e connection of cause and effect, and fritter it down into th e unsatisfactory relation of habitual sequence.”13 Lorenz G eiger's Handbook o f Pharmacy, which Mayer knew (and probably owned), contained an appreciable section discussing the general concepts of phys­ ics and chemistry. It followed the norm in characterizing physics as the science th at investigates th e causes of change in the m aterial world, causes th a t are in general called forces.14 Geiger, too, further identified forces more particularly as th e causes of motion, b u t in a som ewhat m ore quantitative fashion th a n most: “W here m otion is to arise or again cease there m ust be a force th a t occasions or hinders it (see inertia). But the force experiences each tim e from the body upon which it acts a co u n ter action proportional to its mass or to th e m agnitude of its m otion, whereby th e acting force is dim inished or entirely annihilated.”15 Mayer thus had am ple license from the well-known and respected authorities he consulted for regarding forces in general as causes, and in particular as causes of m otion— though to be sure, as M ayer com plained, th at was not the only way in which th e word “force” was used. C onceptual and term inological inconsistencies abounded. Fischer included under th e “m otive forces of n atu re” th e force of the will, m om entum , elasticity, and the causes of gravity, m agnetism , heat, and elec­ tricity.16 In th e event, however, he did n o t m aintain consistent usage w ith respect to “forces” versus “im ponderables.” Am ong the effects for which Biot assigned various forces as th eir cause were th e expansion and contraction of bodies by h eat and cold, the m u tu al attraction of m agnet and iron and of electrified bodies, the fall of bodies toward th e center of the earth, chem ical affinities, the endeavor of the planets toward th e sun, and organic forces subject to som e extent to voluntary control (though such forces played no role in his physics).17 But Biot also referred to gravity, attraction, and light as “properties” of m aterial bodies and urged the probability of th eir materiality, and he spoke of the “principles” of electricity and m agnetism , b oth of which he likewise took to be “fluids,” just as he leaned toward the m ateriality of h e a t.18 Biot’s physics did not have a consistently applied concep­ tion of force, nor was th e term usually applied to the class of entities m ore com ­ monly referred to by contem poraries as im ponderables.

T h e m o st obv io u s a n d in d e e d p a ra d ig m a tic ex am p le of a physical force was th e a ttra c tiv e force of gravity. T h e law of u niversal g ra v itatio n ad m irably fulfilled th e goal of physics of exlain in g an o rd ered class of p h e n o m e n a in te rm s o f a n u n d erly ­ ing cause, a force n o t red u cib le to a n y th in g else. As K a m tz p u t it, in tra cin g back th e c h a in of effects a n d cau ses we finally co m e to a cau se th a t is in sep arab le from th e essen ce of m a tte r: “T h is u ltim a te cau se of th e [p h e n o m en al] chan g es is called force.”19 T h e force o f g ra v ita tio n a p p e a re d to m o st to be in ex tricab ly associated w ith m a tte r. For Fries all th e fu n d a m e n ta l forces (G rundkrafte) are e ith e r a ttra c ­ tive or repulsive, a n d are th e causes of increase or decrease in m o tio n or of dev ia­ tio n fro m stra ig h t-lin e m o tio n . H e, too, a tta c h e d his forces firm ly to m a tte r: “Every fu n d a m e n ta l force or original force is an im m e d ia te invariable p ro p erty of its m a ss.”20 M u n c k e likew ise re p e a te d ly in siste d th a t forces are necessarily b o u n d to m a t­ ter, th a t o n e c a n n o t co nceive of forces h av in g an e x isten ce in d e p e n d e n t of m a t­ ter.21 In h is article o n “F o rce” in G e h le r’s Physical D ictionary h e co n sid ered an d re je cte d as scientifically valueless th e d y n am ical th e o ry of fu n d a m e n ta l a ttra c tiv e a n d repulsive forces— th a t is, K a n t’s th e o ry (or o n e of its la te r v ariants) w hereby m a tte r is c o m p o se d o f o ntologically p rim itiv e o p p o sin g forces. H e th e n ad d ed : “E m p ty in a lm o st th e sam e way are th e h y p o th e se s o f th o se w ho regarded th e im p o n d e ra b le pow ers (im p o n d e ra b le s, inco ercib les) as m erely forces or activities, or fan cied th a t th e y h a d ex p la in e d th e ir real essence by in tro d u c in g su ch a n a m e .”22 H e re je c te d th e n o tio n of a la te n t force as “u n th in k a b le .”23 A lth o u g h for m o st w riters m a tte r an d force w ere o sten sib ly (and form ulaically) th e tw o parallel c o n s titu e n ts of th e physical w orld, only m a tte r was g ra n te d a n in d e p e n d e n t exis­ tence. F ried rich T ie d e m a n n gave an u n u su a lly e x te n d e d c o n sid e ra tio n of th e n a tu re of force in his highly reg ard ed H u m a n Physiology. In large m e a su re h is views were close to th e c o n sen su s of his p h y sicist c o n te m p o ra ries: forces are th e causes of physical ch an g es, an d c a n n o t b e co n ceiv ed to ex ist in d e p e n d e n tly of m atter. H ow ­ ever, h e also e n te rta in e d th e id ea, rejected by H ersch el, th a t th e c o n c e p t of force expresses th e (purely c o n c e p tu a l) relationship b e tw e e n causes a n d effects, al­ th o u g h h e h im se lf seem s to h av e preferred giving th e c o n c e p t o f causality a K a n t­ ian ep istem o lo g ical g ro u n d in g . H is tr e a tm e n t well e p ito m iz es th e co n te x t w ith in w hich forces w ere d iscu ssed by G e rm a n sc ie n tists in th e 1830s: We call the internal conditions or causes of the manifestations of activity [Thdtigkeits-Aeusserungen] of living bodies th a t lie in the constitution of the living bodies themselves their forces. The word force has long since been used with different meanings, which has thus caused confusion in the explanation of the phenom ena of nature. O ne understands by it sometimes the property, or the cause lying in the constitution of a body, that produces certain phenomena; on the other hand one sometimes imagines by it a som ething which only (as it were) adheres to bodies, penetrates them , b u t which is objectively different from their m a tte r.. . . W here we perceive certain phenom ena in the sensory world, there we are obliged by the nature of our cognitive faculty to relate them as results or effects to a thing th at we call the

cause or th e basis in reality [Realgrund] of the phenom ena. W e attrib u te to this thing, as the cause of th e production of certain phenom ena, a force, and we call th e p h en o m ­ ena its effects, or m anifestations of force [Kraft-Aeusserungen]. T h u s do we perceive th e phenom enon of gravity in bodies. Physicists bestow th e nam e force of gravity [Schwerkraft] on th e cause of this phenom enon th a t lies in th e bodies. As far as our experience w ith it reaches, this force is grounded in th e m aterial co n stitu tio n of b o d ­ ies, and we see th e phenom ena of gravity to be different according to their differences; we call this their specific gravity. Physicists regard the cause of gravity th a t lies in bodies [die in den Korpern liegende Ursache der Schwere) , which they designate by the term force of gravity, not as som ething existing by itself, objectively different from the m atter [of the bodies] and only just attached to them ; rather they regard it as a property grounded in the co n stitu tio n of the bodies themselves. . . Force is thus a subjective concept by w hich we express th e relationship obtaining betw een cause and effect or betw een the properties of bodies and their phenom ena . . . . If we ask further: are th e phenom ena th a t bodies or m aterial substances present really only just effects of their m aterial properties, or are they n ot perhaps grounded in a som ething th a t is n ot m atter? Here we m ust openly confess th a t the answer to this question lies wholly outside th e realm of our knowledge; because such a som ething, w hich is n o t m a tte r and consequently supersensible, can in no way be an object [Cegenstand] of our knowledge insofar as it has no access to our im aginative faculty [Vorstellungs-Vermogen] . T here is only one force known to us through experience, the psychic force [Geisfeskra ft] or soul, th a t knows itself, investigates th e causes of th e phenom ena of nature, and conceives of a suprem e or highest cause of nature and itself, som ething Absolute o r Divine. W e regard this force as grounded in a supersensible substrate insofar as it docs n o t perceive itself, as it does other things, by m eans of th e external senses, b u t knows itself sim ultaneously as object [O bject] and subject, or is th e object [Cegen­ stand] of its own internal perception. Even this force m anifests itself, as far as experi­ ence goes, in and through a body. W e have no experience and no real conception [reeller Begriff] of an im m ediate action of th e psychic force, one n ot m anifesting itself in a body and hence entirely independent of it. W h e th e r and how this self-knowing force m ight be able to m anifest itself as active even independently of and n o t bound to a body is not a m a tte r for physics and physiology, which only deal with th e p h en o m ­ ena and properties of bodies in general, and of living bodies in particular, as far as they can be known through sensible perception. T h e solution to th a t problem thus belongs in the dom ain of m etaphysics.24

For Mayer to have advanced a concept of forces as independently existing physical entities was thus a severe challenge to those, the overwhelming majority, for whom such an idea was unthinkable and unimaginable.25 Let us look more closely at just what forces were invoked as causes of various classes of phenomena. According to Leopold Gmelin, “all changes in the material world can be reduced to the following causes, or fo rc e s” : forces of repulsion and attraction (gravitation, cohesion, adhesion, and chemical affinity) and the vital force.26 Baumgartner noted that the diversity of the phenomena prevents us from

tracing th em all to a com m on original force, hence “we therefore assum e a partic­ ular force for every related series of phenom ena th a t we cannot further explain, and nam e it according to the last phenom enon to be explained by it. O ne thus speaks of a force of gravity, or a force of adhesion, in order thereby to designate th e u ltim ate cause [G rund] of gravity, of adhesion.”27 B aum gartner identified the G rundkrafte as (otherwise unspecified) attractive and repulsive forces. He did not, however, include th e im ponderables am ong the forces of nature. T hey constituted a separate class.28 Fries, too, identified th e G rundkrafte, the m otive forces th at cause bodies to change their state, as forces of attraction and repulsion, such as those responsible for expansion and cohesion.29 He classified sound, light, and h ea t as “ph en o m en a of im m ediate sensuous perception,” m agnetism , electricity, and organic processes as “phenom ena of m ediate observation.”30 Fries thus a p ­ plied a phenom enological criterion to break u p th e conventional class of im p o n ­ derables. For Geiger the Vrkrafte were forces of attraction and repulsion whose m u tu al relationship determ ines th e characteristic properties of m atter (Schwere, cohesion, adhesion, and affinity) through which bodies in tera ct.31 For th e m ost part, th en , M ayer’s contem poraries m ean t by Kraft the attractive and repulsive forces of m a tte r th a t were conceived to b e th e u ltim ate causes of the properties of m a tte r and of phenom ena of physical change (in particular, of phys­ ical m otions), th o u gh to be sure there was appreciable latitu d e in the application of th e term . T h a t motion played such a prom inent role as th e general effect of a force may have encouraged M ayer to include m otion w ithin th e new class of en ti­ ties he was com ing to identify as forces, entities of a radically different nature from those previously designated by th a t term . In developing his own conception of force, M ayer realized a t an eary stage th at he need ed a q u an titativ e m easure of its m agnitude, in particular of the quantity of m otion. To his great frustration and confusion, w hen he tu rn ed to co ntem po­ rary physics texts for en lightenm ent he found him self at sea in a mass of inconsis­ tencies and contradictions. M ayer never had a sure com m and of even th e rudi­ m ents of m athem atical physics, and was thus poorly equipped to correct his sources. Fortunately his friend Baur gave him valuable help in this area, though even he expressed exasperation at M ayer’s som etim es dogged a ttac h m e n t to in­ correct notions. W riting as if the vis viva controversies of the eig h teen th century had never taken place, writers of physics texts universally took the m easure of the quantity of m otion to be mass tim es velocity, even though such a definition could not be rhym ed with th e definition of force as cause of m otion in the case of the m otion produced by th e force of gravity on a falling body.32 W rote Lam e, in a passage cited by Mayer: “In all cases th e ratios of th e m asses of bodies are defined and m easured by th e ratios of the quantities of force of th e sam e nature th a t are capable of im pressing on these bodies m otions with th e sam e velocity. O ne is only repeating this definition, th e only exact one, of th e word mass w hen one says th at the instantaneous forces are proportional to the masses that they move with the same velocity.”33 M ayer further q u o ted L am e’s statem en t th a t “forces are proportional to the velocities th a t they would impress on the same m ass.”34 Biot and Wlrewell

gave th e sa m e m e a s u re (mv) of q u a n tity of m o tio n a n d o f fo rc e , re sp e c tiv e ly .35 F isc h e r in tr o d u c e d h is c o n c lu s io n “th a t in all ca se s th e q u a n tity o f m o tio n is p r o p o rtio n a l to th e p r o d u c t o f th e m a ss a n d th e v e lo c ity ” w ith a b rie f p h ilo s o p h i­ cal a n a ly sis.’6 W h e n o n e c o n s id e rs b o th th e “m o tiv e fo rces o f n a t u r e ”— t h a t is, t h e fo rc e o f th e w ill, m o m e n tu m , elasticity , a n d th e c a u se s o f gravity, m a g n e tis m , h e a t, a n d e le c tric ity — a n d th e force of in e rtia (B e h a rru n g s-K ra ft), th e n o n e easily p erc eiv e s th a t the conception [Vorstellung] o f a force is never som ething perceptible [Anschauliches], thus also in no case som ething in and of itself measurable. B ut since m a th em a­ ticians have nevertheless long since represented m otive forces by m eans of lines, n u m ­ bers, and form ulas, it is necessary th a t th e beginner be clearly instructed right from th e beginning in w hat sense such expressions for forces are to b e understood. Now w hat can be said ab o u t this in general is first of all that what can be measured is never the force itself, but only the effect it has produced or would produce— insofar as it is again a necessary law of our cognitive faculty to recognize th a t th e effect is always proportional to th e force (or part thereof) th a t is actually used for th e effect. Now since th e effect of m otive forces is nothing b u t motion o f a body, we m u st first concern ourselves with a measure for the motion o f a body}' F isc h e r w e n t o n to set u p w h a t h e to o k to b e a m o re g e n e ra l la w th a n N e w to n ’s th ir d law, a c c o rd in g to w h ic h a b o d y loses th e s a m e q u a n t ity o f m o tio n it c o m m u ­ n ic a te s to a n o th e r. H is gloss o n h is n e w law rev eals h o w th e in c lu siv e n e ss o f th e d e f in itio n o f fo rc e as c a u se o f m o tio n , c o u p le d w ith a n a p p e a l to e x p e rie n c e as fin al a rb ite r, w o rk e d a g a in s t an y in tu itiv e se n se o f th e c o n s e rv a tio n o f energy: T h a t even this law is not a rational one, b u t only one known through experience, is evident because it does n o t apply at all to th e production of m otion by psychic force (the force of th e w ill). O ne ca n n o t even attrib u te m otion to th e will itself when it acts as a m otive force; b u t it can produce and com m unicate m o tio n w ith o u t thereby suf­ fering any loss. Indeed, one can even doubt w hether this law is applicable to im per­ ceptible substances, e.g., to the m otions produced in perceptible bodies by heat, light, m agnetism , e tc .38 M u n c k e ’s a rtic le o n “F o rc e ” in G e h le r ’s P hysica l D ic tio n a r y p ro v id e s a g o o d e x a m p le o f th e e x te n t to w h ic h a u th o r s s o m e tim e s a d v a n c e d sev eral m u tu a lly in c o m p a tib le d e fin itio n s of fo rce. In o n e p a ra g ra p h M u n c k e a p p lie d th e w o rd K r a ft to w e ig h t, m o m e n tu m , a n d vis viva: T he m otive force of any mass can clearly be m easured by th e w eight w ith w hich it presses against its support and sets in actual m otion a body capable of being moved by it. If one thus calls th e absolute w eight of a body P, its m otive force is x = P. But at th e sam e tim e th e intensity of a force m u st be all th e greater, th e greater th e space is through w hich a given body [Last] is m oved by it in a u n it of tim e, because b o th the exertion of force [Kraftanstrengung] as well as the m echanical effect [Klutzeffect] are so m uch greater. T hus if the mass of a body expressed by its w eight is called M, its velocity C, and if it exerts a force proportional to its m o tio n against any o th er body,

then th e m easure of th e latter [force] is clearly k' = M C . But on e m ust consider here that one obtains a different m easure o f force when a m ovable body is kept in con stan t m otion by another o n e m ovin g w ith a given velocity, than w hen the latter hits a body at rest and com m u n icates to it all at on ce th e entire force of its m otion; as is well known, the former is also called th e m echanical m o m en t of th e m otion , the latter the m om en t o f inertia o f the m otion . . . H uygens was th e first . . . to point out that the effect of a m oving body on on e at rest m u st be equal to th e product o f the m ass and th e square of the velocity.59

A few writers called atten tio n to this chaotic situation. An anonym ous reviewer of K am tz’s Textbook o f Experim ental Physics chided the au th o r for speaking of the m otion of a force (das Bewegtwerden der Kraft) instead of th e m otion of th e body m oved by the force, and called this “a confusion of concepts which stem s from the fact th at quantity of m otion and accelerative force are designated w ithout distinc­ tion by th e sam e word force. For th at reason com m unication of m otion and accel­ eration are also regarded as the result of the same kind of force.”40 T he author of a textbook of m echanics, Johann Andreas Schubert, com plained th a t the word Kraft had been given several different m eanings; “O ne does not always designate th e sam e concept with the word force; som etim es one understands by it the cause of th e actual m otion of a mass, som etim es th e tendency for th e production of m otion, even (finally) a pressure, whereby no account is taken of any m o tio n .”41 T he H eidelberg professor of physics, Philipp G ustav Jolly, who reviewed the book, objected (with som ew hat quibbling justice) to S chubert’s charge, saying th a t ev­ eryone agrees on the definition of force, although they m ay give different m eas­ ures for th e m oment of the force. Jolly’s own understanding of force was quite the norm; As the author h im self remarks, and as is universally assum ed in all scien tific works, by force one understands th e cause o f m o tio n of a mass or the cause of th e ten d en cy of a mass toward m otion . A force itself cannot be m easured, only its effect is m easured, i.e., th e m otion that it produces or w ould produce when no o b stacle to the m otion opposes it. T h e effects of tw o forces are in the sam e ratio as the m asses m u ltip lied by the velocities w hich they possess or w ould possess if there were no obstacle to the m o tio n .42

Jolly, th e reader will recall, was one of the professors to whom M ayer turned in the fall of 1841. Several authors noted the tendency of the forces of n ature to produce a state of rest or “indifference.” Berzelius, for example, coupled th at belief (som ewhat oddly and ambivalently, given our acknowledged understanding of th e solar sys­ tem ) w ith our inabililty to understand the purposeful contrivances of living organ­ isms, an inability th a t should instill in us a hum ble respect for the wisdom of the creator: AU effects [or actions (Wirkungen)] originate ou t o f what we call forces; th ese in turn (like th e will) strive to b e carried o u t or satisfied in order to com e to rest after having b een satisfied, to a rest w hich cannot be disturbed and in w hich n oth in g can arise that

accords w ith th e n o tio n of chance. W e do n o t u n d erstan d how it is precisely this striving of inorganic m a tte r to com e to an indifferen t an d resting sta te th ro u g h the yearning for satiation of opposing forces [Sdttigungsbegierde wechselseitiger Krdfte] th a t is em ployed to keep it in ceaseless activity; b u t we see this calculated regularity in th e m otions of th e planets [Welten], o ur investigations discover every day m o re and m ore a b o u t th e stru ctu re [Gebaude] of organic bodies co n stru cted in so m arvelous a fashion for certain final purposes, and it will always do us m ore credit to adm ire th e w isdom th a t we ca n n o t im itate th a n in philosophical arrogance to reason ourselves speciously to th e supposed know ledge o f th a t w hich is perhaps n o t given to us ever to u n d e rsta n d .43

Davy, in his Consolations in Travel, considered m ore particularly th e ten d en cy of gravitation, if un op p osed by other forces, to reduce the world to a featureless sphere: T h e property, w hich . . . universally belongs to m atter, gravitation, is th e first and m ost general cause of change in our terrestrial system . . . . T h e forms u p o n th e sur­ face of th e globe are preserved from th e influence of gravitation by th e attractio n of cohesion, or by chem ical attractio n ; b u t, if th e ir parts had freedom of m o tio n , they would all be levelled by this power, gravitation, and th e globe w ould appear as a plain and sm ooth oblate spheroid, flattened at th e poles. T h e attra c tio n of cohesion or chem ical attractio n in its m o st energetic state, is n o t liable to b e destroyed by gravita­ tion; this pow er only assists th e agencies of other causes of degradation; attractio n , of w hatever kind, tend s, as it were, to p roduce rest, a sort of etern al sleep in n atu re. T h e great antag o n ist pow er is heat. By th e influence of th e sun, th e globe is exposed to great varieties of te m p e ra tu re .44

Such pronou ncem en ts help make intelligible M ayer’s still odd statem en t, toward th e b eg in n in g of his first (unpublished) paper, that “w e can derive all phen om en a from a prim itive force [Urkraft] th at tend s to annihilate th e existing differences, to u n ite everything th at exists in to a h o m o g en eou s m ass in a m athem atical p o in t.”45 L I The Parallelogram o f Forces and Central-Force M otion Virtually all physics texts of th e period follow ed the introduction of the con cep t of force w ith a discussion o f th e parallelogram o f forces. In a straightforward and unproblem atic fashion, they laid o u t th e graphical tech n iq u e o f representing forces and m otio n s by m eans of directed line segm en ts, and o f th en com b in in g and d ecom p o sin g th em so that, for exam ple, tw o equal and oppositely directed forces (or “m o tio n s”) cancel each other ou t (sich einander aufheben, or words to that e ffe c t).46 Such co m m o n treatm ent m ay have suggested to Mayer a deeper com m on ality b etw een force and m otion. Be that as it may, other than reinforcing his inclination to take mv as the m easure of force and providing him w ith a m is­ leading instance o f the annihilation o f force, th e parallelogram of forces was im ­ portant insofar as it also provided a w idely used schem a for the analysis of central-

force m o tio n s, in p a rtic u la r of th e m o tio n of th e p la n e ts a ro u n d th e sun. M ost G e rm a n tex ts o ffered a close v a ria n t of a sta n d a rd analysis of th e p ro d u c tio n of c o n stra in e d circu lar m o tio n re su ltin g from th e qu asi-v ecto rial c o m p o sitio n o f a c e n tra l force a n d w h a t was typically referred to as a “ta n g e n tia l fo rce ”— th a t is, n o t as resu ltin g from th e a c tio n of a c e n tra l force o n a body w ith a p a rtic u la r initial velocity. E v en a te x t like G e ig e r’s, w hich o ffered n o d e ta ile d analysis o f ce n tra lforce m o tio n s p er se, still em p lo y ed th e sam e language: Every curvilinear m otion is a composite m otion where at least two forces must operate. If one force hereby always seeks to drive the body toward a fixed point, while the other drives it steadily away from there, and both forces act equally, then the body describes a circle. One of the forces, the one that drives the body toward the midpoint, is called centripetal force, the other, which drives it away from there, centrifugal force (tangential force); both together are also called central forces.47 H aving reflected o n su ch lan g u ag e, a n d h av in g co m p a red th e m a g n itu d e s of th e tw o c o m p o sin g “fo rces” to th a t of th e re s u lta n t “m o tio n ” in th e typical diagram s of ce n tra l-fo rc e m o tio n , M ayer was u n d o u b te d ly led to th e erro n eo u s co n clu sio n th a t force can b e d e stro y e d a n d c re a te d — since th e solar system is a k in d of perp e tu u m m o b ile — in g rav itatio n ally c o n tro lle d c e n tra l-fo rce m o tio n s. C e rta in c o n ­ sid eratio n s led h im to m ak e a fu n d a m e n ta l d is tin c tio n b e tw e e n su c h “n a tu ra l” physical system s a n d “artificially” c o n stra in e d m e c h a n ic a l system s, in w hich force can only b e d estro y ed . L e t us lo o k a t so m e typical exam ples of th e tre a tm e n t of ce n tral-fo rce m o tio n . O n e o f th e boo k s in M a y e r’s library, o n e th a t his fa th e r h a d given h im w h en h e was a boy, w as T u b in g e n p rofessor Jo h a n n H e in ric h M o ritz von P o p p e ’s m u lti­ v o lu m e “physics for c h ild re n ,” D er physikalische Jugendfreund. In a c h a p te r on ce n tra l forces, P op pe an alyzed th e m o tio n of th e m o o n a ro u n d th e su n as th e re su lta n t of tw o se p a ra te forces: Gravity causes it [the moon] to remain always near our earth, b u t gravity united with still another force is the cause of its always going around our earth. O ne can imagine this second force as an impulse which the moon received right at its creation in a direction going off sideways from our earth, and whose effect now continues undim inished. If S indicates the earth and the point a the moon (Figure 2, Plate IV), and if a is driven in such a way toward the earth and at the same time in such a way away from the earth that by means of these two forces the parallelogram abed can be constructed, then

force/motion/ vis viva F ig s .

6.3 and 6.4

By June of th e next year (1844) M ayer had drafted a long essay, which, after repeated and extensive revision in response to suggestions from G riesinger and Baur, would be published toward th e m iddle of 1845 as Organic M otion in Its Connection with the Exchange o f M atter. T he original draft contained a long “po­ lem ic” against certain usages in m echanics— an abiding concern of his— which he to n ed dow n at Baur’s urging.84 It likely contained a critique of th e concept of “Schwerkra ft” as a source of m otion, criticism (again) of th e custom ary definition in m echanics texts of force as th e cause of m otion coupled w ith their use of mv as its m easure, and a m isguided attack on the concept of force instantanee (as he p u t it, after L am e).8’ W h e n he sent th e essay to Griesinger, he explained th e small part physiology played in it— “th e inorganic has becom e w ithout qualification my principal concern”— in term s of the need first to secure his theory on physical grounds before seeking wider applications.86 He pictured his work as an im pregna­ ble citadel over which flew a banner bearing th e words “H eat can be transform ed into m o tio n .”87 In the sam e letter to G riesinger he added th a t “‘M otion is trans­ form ed in to h e a t’: in these five words you have im plicitly my whole theory,” and to Baur he wrote th a t he considered it to be his “life’s task ” to prove the principle th a t “m e2 = h e a t.”88 T h e centerpiece of M ayer’s work was still, w ithout question, th e equivalence of h eat and m otion. A lthough there is no evidence as to just how or w hen M ayer achieved clarifica­ tion on the m atter, som etim e betw een 1842 and 1844 h e m u st have discovered th e fallaciousness of his reasoning ab o u t central-force m otions, the apparent cause in th e first place of his having en tertain ed th e possibility th at force m ight be creatable in divinely contrived “organism s,” and thus have convinced him self th a t forces can never be either destroyed or created. His published essay of 1845 could th u s lead with just th a t confident assertion: “Ex nihilo nil fit.”9* Q u ite ig­ noring th e fact th a t he him self had for years th o u g h t otherw ise, he now boldly asserted th at “th e creation ox the destruction of a force lies outside th e range of h u m an th o u g h t and ac tio n .”90 H e now for th e first tim e criticized th e notion of an inexhaustible vital force in th e sam e term s: “T he creation of a physical force . . . [is] already in and of itself hardly conceivable.”91 T h e transform ability of forces he likewise presented as a logical necessity: “It can be proven a priori and confirm ed everywhere by experience th a t th e different forces can be transformed into one another. There is in truth only a single force.”92 It is also possible th a t M ayer’s newly critical attitu d e tow ard th e vital force was in part a response to Liebig’s forceful, if confused, em ploym ent of th a t concept. Earlier, M ayer had rendered acceptable th e creation of force ou t of noth in g in th e solar system by identifying th e solar system as a divine organism , as if it were obviously m ore acceptable th a t organism s— th a t is, living things— m ight be creators of force. Such an analogy gave M ayer a vested interest in not rejecting the vital force. His consciousness raised by th e inconsistencies of Liebig’s handling of th e vital force, M ayer may have reth o u g h t th e justness and th e necessity of his analogy from th e o th er direc­ tion, and concluded th a t he no longer had to make an exception for any organism. T he som ew hat m isleadingly nam ed booklet th a t resulted from M ayer's inter­ changes w ith G riesinger and Baur contained his fullest statem en t of his theory of

force. Even at that, the sentence just quoted was the closest he ever cam e to anything expressive of the notion of the “unity of force,” a term he never used. Nor did he there or elsewhere ever settle upon a single phrase to express some­ thing like the notion of the conservation of energy. For him his theory was first and foremost “the m echanical theory of h e a t” whose central fact was “the equiva­ lence of heat and m otion.” In the surviving m anuscript from the series of drafts th a t preceded his 1845 work he once spoke of “the axiom of the indestructibility of force,” b u t nothing like that ever becam e his standard way of designating his theory.93 Intriguingly, instead of “axiom” Mayer had earlier w ritten “principle," and instead of “indestructibility of force” he had first w ritten “positive m otions,” th en crossed th at out in favor of "conservation of force,” finally crossing out “con­ servation” and writing above it “indestructibility.”94 Mayer was indeed almost the discoverer of “the principle of the conservation of force”! But he consistently declined to adopt such language. Even after H elm holtz’s work had becom e generally known and its terminology standard, Mayer clung to his favored term s. In an essay from 1862 he spoke of the enrichm ent physics had recently experienced “through the discovery of the law ‘of the indestructibility of force.’"95 In another from 1870 he spoke of “the m echani­ cal theory of heat, or as H elm holtz calls it, the law of the conservation of force.”96 Since Mayer him self had once weighed and rejected the phrase “conservation of force” years before H elm holtz arrived on the scene, his resistance to it cannnot have been solely a question of sour grapes and amour propre. Rather it had also to do with what he perceived to have been his prim e accom plishm ent. In a review w ritten in 1877, the year before his death, of a published speech by H elm holtz on medical thinking, Mayer recalled th a t the purpose of his first publication had been “to secure m y priority rights to the mechanical theory of heat and to the calculation of the m echanical equivalent of heat, which I was the first to carry through.”97 Q uoting a passage in which H elm holtz recounted some of the back­ ground to his discovery of the law of the conservation of force, Mayer countered th at, as far as he knew, the law of the conservation of living force had been discov­ ered two hundred years earlier by Huyghens and th en defended by Leibniz against Descartes: “This law was thus known m uch earlier than the discovery in our day of the m echanical equivalent of heat with its connection to m edicine.”98 Mayer resisted what he perceived to be the danger of having his discovery appear to be merely an extension or a special case of the law of the conservation of vis viva in mechanics: better to avoid any suggestive terminology. In his 1842 paper he had even sought to subsum e the older conservation law under his new principle of the “indestructibility of causes”— forces being of course also causes.99 An im portant aspect of the progressive crystallization of m eaning th a t attended the evolution of M ayer’s thinking was his choice of appropriate terms. Although he did not accompany its statem ent with a handy phrase, Mayer nev­ ertheless did give clear if somewhat awkward expression in 1845 to the essence of the conservation of energy: “In all physical and chemical processes the given force remains a constant quantity,”100 He identified what he took to be the five principal forms of physical force as fallforce, m otion, heat, m agnetism and electricty (con-

sidered together), and chem ical force.101 He th en listed exam ples of each of the twenty-five possible forms of transform ation am ong th e different forms of force. For th e first tim e either in print or in private, M ayer h ad significantly expanded his atten tio n beyond heat, m otion, and (as of late 1841) fallforce. In working up to this conclusion, he had devoted separate sections of his essay to each of th e five principal form s of force, in which h e anticipated th e full network of interconnec­ tions. He analyzed, for example, the transform ation of m echanical effect into electricity and m agnetism in th e electrophore and in the m agnetization of previ­ ously “indifferent” steel rods.102 And m ost im portantly, he offered a full and clear calculation of th e num erical equivalence betw een h e a t and fallforce. Here again it would have been term inologically anachronistic to have spoken of M ayer’s calculation of the m echanical equivalent of h eat, since no such phrase had yet m ade its appearance in his writings. It was the theoretically central equiv­ alence of h eat and m otion th a t was of greatest im portance to him , less so the num erical equivalent connecting h e a t and fallforce: th e latter was, to b e sure, im p o rtan t, b u t its function was to confirm the former. Even in his next m ajor work, in 1848, he again calculated the number w ithout assigning it any particular descriptive nam e.m Only in 1851, in his Remarks on the M echanical Equivalent o f Heat, did he expressly introduce the te rm .104 W h a t had taken place in th e m ean­ tim e was his interchange with Joule, though even as Joule spoke in 1849 of “the m echanical equivalent of h eat [calorique],” M ayer responded w ith a claim to his priority in discovering “th e law of th e equivalence of h eat and vis viva and its num erical expression.”105 For m e the fact or no t of giving som ething a nam e is an im p o rtan t indicator of th e self-consciousness a person has w ith respect to its im ­ portance, hence it would appear th a t M ayer required an external stim ulus before he ‘realized’ just how im p o rtan t the nu m b er in question was: it had becom e the focus of an international priority dispute, a specific fact on which hard claims could be based. T h e m eaning of M ayer’s work experienced another small shift, an o th er small b u t significant sharpening of its focus. A lthough M ayer always considered the establishm ent of the m echanical equiv­ alence of h ea t on physical grounds to be his forem ost scientific undertaking, he nevertheless m ain tain ed an interest in th e relevance of his ideas to physiological phenom ena. Such is hardly surprising, since he was a physician and h ad begun his train of speculations by addressing issues of respiration, th e function of the blood, and anim al heat. C ontem porary authors’ use of a vital force m ight also have pro­ vided him with a rather obvious target of criticism against which he could argue in term s of cause and effect and th e like, assum ing th a t those works h ad caught his atten tio n . Yet his desire to devote his energies first to physics, coupled w ith his lingering suspicion th a t organisms m ight be capable of creating force, effectively diverted his a tte n tio n from physiological issues u ntil (it appears) som etim e b e ­ tw een m id -1843 and m id -1844.106 In May 1843 Griesinger inquired of him w hat th e situation was w ith respect to th e in ten tio n he h ad earlier expressed of writing a physiological essay for W underlich and Roser’s journal.107 M ayer replied in June 1844, sending his friend a draft of such an essay for criticism .108 H e m entioned th a t C arl Pfeufer, who in 1844 m oved from Z urich to H eidelberg as professor of

clinical m edicine, had been inform ed of his work (by an unnam ed third party) while he was in H eilbronn, and th a t Pfeufer had urged him strongly to publish something else, “since he thought the theory prom ised to do m uch for physiology, which decided m e all the m ore to move the m atter as close as possible to physiology.”109 In reply Griesinger offered Mayer two bits of advice: “In the first place you should spread people some critical b u tte r and sprinkle them some polemical salt on the dry bread of m echanics and m athem atics.”110 H e suggested in particular targeting Liebig’s theory of anim al m otion (in the controversial third section of his Anim al Chemistry) and L otze’s handling of the concept of force (in his Gen­ eral Pathology). In the second place he recom m ended th a t Mayer make the phys­ iological part of his essay longer and broader, addressing issues of general rele­ vance to the understanding of vital phenom ena. He suggested considering the views of others— for example, Valentin, who, he said, stood m ethodologically close to M ayer’s approach to physiology. M ayer thereupon asked Griesinger to send him L otze’s book and som ething of Valentin’s, and expressed his profound disagreem ent with Liebig’s work, adding th at it would be easy to refute Liebig’s entire theory on the basis of internal contradictions— a task that, following his friend’s advice, he would set about to do.111 Griesinger responded by suggesting that Mayer separate the physiological from the physical part of his work and seek its publication in his friends’ journal, and he again urged him to address general questions— “on force, vital force, etc.”— and to write with sharp polemics against the already m entioned authors.112 To Baur, Mayer wrote at the end of July th a t he had decided to include “a m odest polemic against Liebig’s ‘Phenom ena of M otion in the Animal O rganism ’; maybe th at will succeed in bringing the m atter into consideration.”113 M ayer’s response to Liebig’s work was strange, given the obvious points of major disagreem ent betw een them on fundam ental physiological m atters. It is striking th at the errors he alluded to, late in 1842, in the third section of the Animal Chemistry had to do not with the vital force b u t w ith Liebig’s stillborn attem pt to introduce physical concepts such as Bewegungsgrofie, Kraftmoment, and Bewegungsmoment} 14 Even in 1844 the first thing he criticized about Liebig’s use of the concept of vital force was th at he associated it with "forces” of gravity and adhesion (Liebig had said cohesion): “Since I firmly com bat these latter two [misapplications of the word force], there lies therein indirectly a polem ic against Liebig, the contest can thus m ost easily be settled on physical grounds.”115 How­ ever ‘natural’ M ayer’s eventual criticism of Liebig’s physiological ideas may ap­ pear— and conceptually it does follow directly from im portant differences in the views they held— the evidence strongly suggests th at it was primarily Griesinger’s pressure th at prom pted him to compose the highly critical passages directed against Liebig’s Animal Chemistry th at occupy such a prom inent place in his Or­ ganic M otion in Its Connection with the Exchange o f M atter. T h at Mayer himself may have been uncom fortable with such a level of polemics is suggested by the fact th at he om itted those nine pages from the collected edition of his works in 1867. It is hardly less odd th a t arch-polem icist Liebig let such an attack go un­ answered.

I argued earlier th a t, although M ayer’s pre-1845 reflections do n o t seem to have involved a critique of th e vital force, nevertheless som e of th e issues raised in co n n ectio n w ith it m ay well have stim u lated his thinking ab o u t problem s of the creation and d estru ctio n of substances like forces, th e im ponderables, and the soul, as well as of th eir m u tu al sim ilarities and differences. T h e present evidence suggestive of a p ro tracted reluctance to attack th e concept of vital force head-on accords w ith th e possibility th a t M ayer m ay have been attac h ed to th e concept because it le n t su p p ort to his belief th a t organism s, including th e solar system , are in fact capable of p roducing force even in th e absence of a n te c e d e n t physical or chem ical transform ations. It w ould certainly seem th a t his use of th e term “organ­ ism ” in th a t con n ection im plies a tacit u n d erstan d in g th a t living beings are som e­ how m ore naturally acceptable as creators of force. It w ould appear, too, th a t it was only after he gave u p th e idea of th e creation of force ex nihilo in th e solar system th a t h e in fact cam e o u t against th e concept of a w ork-perform ing vital force. O n e m u st be cautious, however, in th e absence of clear evidence, of m aking too strong an d one-sided a causal claim , since M ayer m ay also have becom e in­ creasingly sensitive to th e increasingly negative ju d g m en t on the status of the vital force by G erm an scientists during th e half-decade in question. Slightly less th an a third of M ayer’s 1845 book— th e first p art— was devoted to physical an d chem ical m atters. T h ereafter cam e a six-page depiction a la D um as of th e energetic an d m aterial interrelationships am ong sun, earth, plants, and anim als. T h e first physiological controversy to engage him was w hether the pro­ d u ctio n of force in th e m uscles is due, as m any (including Liebig) th o u g h t, to the co n su m p tio n of m uscle tissue or, as M ayer m aintained, to th e oxidation process in th e capillaries of th e m uscles.116 However, th e bu rd en of th e polem ics against Liebig was directed against his use of th e concept of vital force in th e th ird section of th e A n im a l C hem istry. M ayer did n o t fail to call a tte n tio n to th e “logical incon­ sistency” in Liebig’s explanation of organic m otions, one of those “internal con­ trad ictio n s” n o t infrequently en countered in his w ritings.117 H e q u o ted w ith ap ­ proval th ree paragraphs from th e first section of Liebig’s book in w hich Liebig traced th e p ro d u ctio n of all h ea t and m otion to th e exchange of m a tte r.118 H e th e n q u o ted w ith disapproval tw o paragraphs from th e last section of th e book in w hich th e ex p en d iture of vital force was identified as th e cause of an an im al’s p ro d uctio n of m echanical work.119 M ayer concluded: T h e exch ange o f m atter th a t was first declared to b e th e cause of th e work per­ form ed by th e m u scles is here m ad e in to its result. To p u t it in term s o f on e o f L ieb ig’s exam ples, first th e river drives th e m ill, and afterwards th e m ill drives th e river. A specific capability o f resistance of livin g tissu e “against external causes o f distur­ b a n ces,” against th e in flu en ce of atm osp h eric oxygen, against p u trescen t d eco m p o si­ tion, as th e effect of a d istin ctiv e vital force in L ieb ig’s sense, w e ca n n o t allow b ecau se w e do n o t regard ourselves as justified in h y p oth etically introd u cin g specific causes w here no sp ecific effects have b een d em onstrated; in oth er words, b ecau se we should n o t think anyth ing w ith o u t a reason [G ru n d].

S in ce we perceive in a ch em ica l process, in th e ex ch a n g e o f m atter, an a d eq u a te basis [vollwichtiger G ru nd ] for th e co n tin u e d e x iste n c e o f livin g organism s, w e m u st th erefore p rotest again st th e proposal o f a vital force in th e sen se o f L iebig, A u ten rieth, H unter, etc. But as regards L ieb ig’s h y p o th esis o f th e expenditure o f a vital force to [prod uce] m ech an ica l effects, th at appears to b e still m o re v en tu reso m e than th e p o sitin g o f such a vis occulta in and of itse lf.I2

M ayer q u o te d a n o th e r four paragraphs from L iebig’s book in w hich Liebig d e ­ scribed th e p ro d u c tio n of m echanical effects in th e anim al organism in term s of th e tran sfo rm atio n of a n im ate in to in an im ate m atter, th e p recondition for w hich was a red u ctio n in th e pow er of th e vital force to resist oxidation, th a t red u ctio n in tu rn having b e e n caused e ith e r by a w ithdraw al of h e a t from th e affected p art of th e anim al or by th e co n su m p tio n of vital force to pro d u ce m echanical m o ­ tio n s.121 M ayer offered a chem ical analogy to d em o n stra te th e w eakness of Liebig’s arg u m en t: certain substances (such as g adolinite and five o th ers he nam ed) u n d ergo a change in resistance to chem ical action a tte n d a n t u p o n th e p ro d u ctio n of h e a t or som e o th e r (unspecified) force, b u t unlike th e effect of th e organism ’s loss of h e a t or its p ro d u c tio n of m echanical effects in reducing its resistance to chem ical decom position, th e resistance of gadolinite (etc.) increases. T h e p o in t M ayer drew from this line of reasoning was im p o rta n t, a n d recalls th e kind of q u estio n s physiologists h ad traditionally asked w ith regard to an alleged vital force: B ut th e causal co n n e c tio n b e tw e e n vital force and m e ch a n ica l effec t m u st also be declared in ad m issib le for an o th er reason th an th at o f analogy. Just as an effe c t d oes n ot arise by itself, so to o n o ca u se van ish es w ith o u t a corresp on d in g effec t. T h e binary co m b in a tio n o f carbon and oxygen c a n n o t occur, nor can g a d o lin ite (etc.) acquire th a t capability o f resistan ce, w ith o u t a corresp on d in g d e v e lo p m e n t o f h ea t (or an eq u iv a len t force). L ieb ig says (op. cit., p. 249): “T h e su m to ta l of force ex p en d a b le for m ech a n ica l effects m u st b e equal to th e su m total of th e vital force o f all th e organic structures [G e b ild e ] su itab le for th e ex ch a n g e o f m atter.” N ow, w h at e ffe c t d oes th is force m a n ifest after d ea th has occurred? A ccord in g to L ieb ig ’s theory, th e b od y o f a b eh ea d ed person w ou ld have to p rod u ce a great su m o f m ech a n ica l e ffe c ts, or a corre­ sp o n d in g a m o u n t o f h ea t, before th e o n se t o f p utrefaction; b u t ex p erien ce confirm s n o th in g o f th e kind.* 'Q u estio n : W h a t b e c o m e s o f th e vital force after death? Answer: N o th in g . C o n c lu ­ sion: T h e vital force is therefore = n o th in g .— N ih il fit a d nihilum . A force or cause th a t can van ish w ith o u t m a n ifestin g an effe c t is n o t a fo rce.122

W h e re M uller h ad posited th e latency of th e vital force in all m atter, w here Auten rie th h a d assu m ed th e existence of a preterphysical realm to w hich th e vital force could re tu rn after d ea th , a n d w here L otze h ad assum ed th e existence of a variable force, M ayer tacitly invoked his id en tificatio n of forces as causes and his principle of th e in d estru ctib ility and uncreatability of force in order to deny leg it­ im acy to th e very n o tio n of a vital force a Ia Liebig.

M ayer w ould n o t have been M ayer had he n o t elaborated still a n o th e r analogy, this tim e b etw een th e irritability of organic tissues an d th e expansibility of gases. Irritability was, in his in terp retatio n , th e capacity of living m a tte r to transform chem ical force in to m echanical effect, while expansibility was th e capacity of gases to transform h ea t in to m echanical effec t.123 H e com pared th e disappearance of th e elasticity of a gas at a low enough tem p eratu re (at which th e gas condenses) to “th e well-known gradual difference in th e permanence o f irritability, or tenacity of life, am ong different classes of anim als”— namely, th a t cold-blooded anim als rem ain capable of irritable m uscular response u n d er circum stances (such as re­ d u ced oxygen supply and d eath) w hen th e m uscles of w arm -blooded anim als cease to fu n c tio n .124 T h u s “th e apparatuses of m o tio n [i.e., th e m uscles] of cold­ b looded anim als appear in general analogous to p e rm a n e n t gases, those of w arm ­ b looded anim als to vapors.”125 H e reinvoked th e analogy a few pages la te r when considering th e “m echanical q u o tie n t” of m uscles, th a t is, th eir efficiency in transform ing a given am o u n t of chem ical force into work. A lthough th e necessary experim ental data were lacking, he ventured tw o ten tativ e conclusions: “ I) T he stronger th e chem ical process or th e form ation of carbonic acid is in an anim al, th e sm aller th e m echanical q u o tie n t and th e less th e m echanical work in relation to th e p ro d u ctio n of heat. 2) By analogy w ith elastic fluids, th e m echanical q u o ­ tie n t is greatest for perm anently irritable m uscles.”126 In o th er words, cold­ blooded anim als m ay be slower and consum e less oxygen th a n w arm -blooded ones, b u t th eir m uscles work m ore efficiently. T his tim e, however, unlike m ost instances w hen he appealed to som etim es rath er farfetched analogies, Mayer seem s to have ap p reciated th e intrinsic lim itations of all analogies: If the parallel drawn between the elasticity of gases and the irritability of muscles is carried further, then it shares the fate of all analogies; the initially natural compari­ son soon becom es artificial and ultim ately loses itself in paradoxes. Gases are formless substances, whereas m uscles are organized, and their actions depend more or less on the influence of the motor nerves; we call this specific influence innervation, to which the expansible fluids in and of them selves reveal nothing corresponding.127

Few characteristics of M ayer’s way of thinking are as striking as his a ttac h m e n t to analogies, w hich ran th e g am u t from th e m ost essential co m p o n en t of his ideas to m erely ephem eral usages, from th e analogy betw een force and m a tte r to th at b etw een th e increasing rate of decom position of dead anim al tissue and th e in­ creasing rate of acceleration of bodies falling to earth from far o u t in space.128 U n d o ubtedly in response to th e perceived danger of a m aterialistic m isin terp reta­ tio n of w hat was only a h euristic analogy, in later years M ayer carefully qualified th e all-im p o rtan t com parison of organism s to m achines: T he material necessary for this m echanical work [of animals] derives, however, from the plant kingdom, to which it has in any case earlier flowed from the sun; thus animals transform erstwhile sunlight into m otion and heat. In this regard, I say in this regard the animal organism, w ith all the infinite diversity of its anatomy, can never­ theless be compared to a steam engine. That is, the steam engine also consum es for

the production of its output [Leistung] , for the production of work— -and of heat— the sunlight stored up by the plant world, and we cannot help b u t . . . make frequent use of this comparison. But let it be stated right at the beginning that a com parison depends on the discovery of sim ilarities, but that similarities are a long way from being an identity. T h e animal is by no m eans a mere m achine; it stands far above even the plants, for it has a w ill.129

He was not always so fastidious in his distinctions. W e have already encountered M ayer’s fascination with the perennial problem of explaining the source of the sun’s unim aginably great ou tp u t of heat and light. For a while he thought he had found it in the continuous annihilation of the centripetal com ponent of the orbital m otion of bodies circling the sun, even if that m eant abandoning the (later!) logically necessary principle th at nothing can be created out of nothing. Giving up th a t explanation was part of the cost of accepting the universal uncreatability of force. Yet the problem stayed with him of explaining w hat Herschel had term ed (in the G erm an translation Mayer read) “das grosse G eheim niss.”130 M ayer’s new solution to the problem was a straight­ forward application of his m echanical theory of heat: the sun’s radiation is the result of the transform ation into heat of the vis viva of m eteors falling a t trem en­ dous speed into the sun. As he put it with his usual rhetorical confidence in his announcem ent of his theory in 1846 to the Paris Academy: “T he sun’s radiation is produced by the fall of cosmic masses, because w ithout th a t there would have to be effects w ithout cause and causes w ithout effect.”131 He developed his theory further in the Contributions to Celestial Dynamics of 1848, where he showed th at the known effect can be accounted for on the basis of reasonably plausible as­ sum ptions— but for one problem. Even if the increase in the sun’s diam eter were unobservable over thousands of years, the increase in its mass should have pro­ duced a detectable effect on the periods of the planets. M ayer’s solution revealed his profound ignorance of the nature of wave phenom ena: An undulating m otion proceeding outwards from a point or a surface in an un­ bounded m edium cannot, however, be conceived w ithout a sim ultaneous progressive m otion, a being-pushed-forward [Fortgedrangtwerden] of the vibrating massy parts, and there thus lies— according to the vibrations theory no less than according to the em anations theory— in the sun’s radiation a reason for a continuous decrease in mass of this fixed star. But why, despite that, the sun’s mass does n ot suffer an actual decrease, for that a sufficient reason was already given. T h e radiation of the sun is the centrifugal action equivalent to a centripetal m o tio n .132

The last sentence is a startling reincarnation of his earlier ideas: the physical m echanism may have changed, b u t the suggestive spirit of the language sur­ vived.133 Ironically, at the beginning of the work he had invoked an analogy be­ tween light and sound th at m ight have set him straight about the nature of wave motion: both consist of vibrations given off by glowing or resonating bodies to the surrounding m edium , vibrations th at m ust steadily dim inish unless there is some

source of c o n tin u e d m o tio n . B ut w h en h e n o te d th a t “people have freq u en tly and appro p riately co m p ared th e su n to a co n tin u a lly so u n d in g b e ll,” h e failed to c o n ­ sider th a t th e so u n d of a bell is n o t carried to o u r ears by air p articles traveling o u t from th e source of vibrations: th e bell is n o t a source of air.134 A m o n g th e m a n u sc rip ts in th e M ayer archives in H eilb ro n n is an appreciable fra g m e n t o n large sh eets, n u m b e re d 57 to 67. It was ap p arently o n c e p a rt of a sizable work, a n d from th e c o n te n ts of w h a t rem ains it w ould seem to have b een a m ajo r su m m in g -u p of his ideas, p re se n te d in su ch a way as to give a good sense of th e o fte n u n sp o k en co n sid eratio n s th a t a tte n d e d his original reflections. It reveals a lo t a b o u t his w restling w ith th e issue of th e possible creatio n of force in n o nliv in g system s an d its im p lic a tio n s for living organism s; a b o u t his c o n cern for das Geistige a n d his co n v ictio n th a t science le g itim ate s b elief in th e soul; and a b o u t th e d e p th of his religious co n c e p tio n of th e w orld in general. F rom in tern al eviden ce o n e can only say w ith so m e assu ran ce th a t it d a te s from after th e late 1840s, a n d probably after aro u n d 1860; o n th e basis of c erta in p ecu liarities of expression I have te n ta tiv e ly d a te d it to aro u n d 1866.135 It th u s provides a n u n u ­ sually v aluable in sig h t in to b o th his m a tu re th in k in g a n d th e kinds of con sid era­ tio n s th a t m o tiv a te d h im a t earlier stages. T h e surviving m a n u sc rip t picks u p in th e m id s t of a d iscussion of issues th a t m ig h t cause som eo n e to q u e stio n the u n crea ta b ility of force: .. . to spread light over what takes place in the microcosm; for if it could be proven that mechanical work were performed, that light or heat were developed somewhere in the macrocosm through the joint action of its parts, ordered with such great wis­ dom, then the possibility would be indubitably dem onstrated that the same thing could also take place in the living creatures of the earth; in the other case, however, if the law valid for the inorganic world— no work without consumption— proves to be true everywhere, even in the planetary system itself, then we are [justified] by the strictest induction to claim the same law as well for muscles and the animal organism in general—a conclusion that henceforth could only be undone by assured facts, but not by scientific-vitalistic meditations. There are, however, in all three kinds of such macroscopic phenomena: I) the motions of the heavenly bodies in their orbits around the sun, 2) the development of light and heat in the planetary system, and 3) the tides.136 S uch h a d b e e n his ow n co n c e rn in 1841 w ith resp ect to th e second p o in t; w h en he first p erceived th e tid es to p re se n t a sim ilar challenge is im possible to say. W h e th e r o r n o t he h im self was ever tro u b le d by th e fact th a t th e solar system is a kind of p e rp e tu u m m o b ile, as som e co n te m p o raries p u t it, is unclear, a n d he m ay have in c lu d e d it for expository p u rposes. S uch as it m ig h t have b ee n , th a t p ro b lem h a d b e e n solved lo n g ago by N e w to n ’s law of gravitation. M ayer c o n tin u e d : Now as regards 2) the development of light and heat on the sun, it would be entirely in accordance with the taste of the vitalists if one were to imagine this action as the effect of a vital force inherent in the planetary system produced by polarity, etc.; but

since, as everyone knows, th e exact sciences will n o t c o n te n t them selves w ith such phrases, I have therefore a tte m p te d to explain th is n atu ral p h en o m e n o n in th e sp irit of th e latter, i.e., to rep rese n t it as a law bound process. T h e tides, finally, w hich m u st be m e n tio n e d here o n ce again, are an in te restin g an d im p o rta n t p h en o m e n o n for biology because it can be d e te rm in e d w ith m a th em atical precision w h e th e r th e work p ro d u ce d by th is m acroso p ic process is to b e regarded as only th e result of th e co m b in atio n of certain o rgan-p arts of th e p lan etary system , or w h eth e r here, too, work an d c o n su m p tio n again go h a n d in h an d . T h e q u e stio n is, nam ely: can work be perfo rm ed by g ravitation in an d of itself alone? If [th e answ er to] th is q u estio n tu rn s o u t to be affirm ative for th e tides, th e n on th e basis of th is exam ­ ple th e possibility m ay n o longer be d en ied th a t m o tio n can also be g en erated by m eans of th e irritability of th e m uscles, w ith o u t any co n su m p tio n . B ut insofar as I have d e m o n stra te d in th e foregoing th a t th e work of th e tid es can only b e p erfo rm ed at th e expense of th e e a rth ’s rotatio n al m o tio n , th e n th e re rem ain s n o ju stificatio n to claim for th e organic arran g e m en t o f a system , or for th e vital process, th e capability in an d of itself alone of b ein g able to perform a c tio n s.1,7

Perhaps M ayer had b e e n prom p ted to consid er th e problem o f th e tid es in c o n ­ junction w ith his running b a ttle against th e c o m m o n usage w h ich id en tified grav­ ity (Schwerkraft) as a force: sin ce it was n o t a force in his sen se of the word, it could n ot by itself be the cau se o f m o tio n . Perhaps h e had b e e n b oth ered by th e fact that th e earth ’s rotation has apparently n o t slow ed m easurably sin ce an tiq ­ uity, d esp ite th e co n tin u o u s friction o f th e tid es, and h e n ce co n tin u o u s c o n su m p ­ tion o f m otion : h is solu tion was to posit a precisely c o m p en sa tin g con traction of th e earth ’s radius. In his co n tin u a tio n , M ayer gave his m o st exten sive surviving consideration of 'm etap h ysical’ issues: A pplying this to psychic actions, it can th u s no longer be a q u estio n of w ishing to see th e se actions, in accordance w ith physical laws, as th e resu lt of th e co m b in atio n of th e b ram fibers or of th e vital force of th is organ; b u t th e re w ould still rem ain tw o assu m ptions. T h a t is, if o n e m akes an analogy b etw een brain a n d m uscle, th e n one can arrive at th e co n c ep tio n th a t, ju st as th e m u scle perform s its m ech an ical work w ith th e h elp of th e chem ical process an d w ith th e co n su m p tio n of th e force supplied by th e latter, so, too, th e brain m ay b e able to p rodu ce its psychic activity w ith th e h elp of th e sam e process. A t first glance such a view m ig h t have so m e th in g sed u ctiv e ab o u t it, [but] on closer ex am in atio n it proves to b e com pletely u n te n ab le . T h a t is, th e actio n s of th e secretory an d m o to r organs d e p e n d essentially on th e fact th a t th e work [Leistung] th ey p ro ­ d u ce— th e p ro d u c t of secretion or th e m echanical work [Arbeit]— is eq u iv alen t to th e co n su m p tio n taking place in th ese organs, an equivalen ce th a t can b e and has been d e m o n stra te d by m ean s of em pirical laws. T h e carbon ic acid exhaled by th e an im al is eq u iv alen t to th e carbon an d oxygen th e anim al co nsum es, its m ech an ical work is eq u iv alen t to th e process of chem ical co m b in atio n taking place in its m o to r organs; b u t how is th e psychic work p ro d u ce d by th e b rain su p p p o sed to b e tak en as th e eq u iv alen t of th e chem ical process, h e a t, electricity, etc.? A nd on e w ould w ish to u n d erta k e to ad d u ce proof o f this?

Now since the psychic activities can and should accordingly b e regarded as n eith er th e result of th e anim al’s vital force nor th e result of a chem ical process in it, we are th u s led necessarily back to the principle th a t th e healthy reason of all h u m an ity has at all tim es and in all places recognized as an axiom atic tru th and [for w hich the expression is found in all languages], and we can n o t h esitate to declare th a t th e as­ sum ption of a m etaphysicial [?] existence, the assum ption of a feeling, willing, and thinking entity, a soul, asserts its authority as an irrecusable p ostulate for th e natural scientist.138

After a one-and-a-half-page discussion (of the kind com m on in A utenrieth, Muller, et al.) of m ental functions and th e exten t to which they do or do not depend on th e integrity of the brain, Mayer concluded: N ow since there is no part of th e brain, m uch less of the rest of th e body, th a t necessarily determ ines a certain psychic disturbance by m eans of a change in its struc­ ture, it thus in tu rn follows th a t all corporeal organs are only capable of exciting disturbances in th e psychic activities per consensum , or in oth er words th a t th e organ of psychic activity is n o t corporeal.

If I should now in addition speak o u t ab o u t th e con tin u ed existence of th e soul after th e death of its m aterial organs, ab o u t th e h u m an bein g ’s personal im m ortality, th en I can repeat th a t w hich has very often been said and w hich is w ritten in every breast. T h e com plete proof of this continued existence lies in the divine perfection [Vollkom menheit] of th e entire arrangem ent of nature. Every p lan t and anim al organ­ ism is constructed in such a way th a t it is capable of fulfilling the purpose for which it was created and of attain in g th e last stage of perfection, [and it would b e a ridicu­ lous presum ption to regard an im provem ent in a single organ(ism?) in th e long series of p lant and anim al species even as only possible]. A nd yet the fool com plains rightly, as does th e wise m an, about the im perfection of this world; b u t th e only th in g im per­ fect [or incom plete (unvollkom m en)] in it is the hum an spirit; it alone in this world is n ot perm itted to attain its purpose, th a t of divine consum m ation [or perfection (Vollendung)], for w hat is th e w isdom of a h u m an being an d th e virtue of th e m ost virtuous of this earth? T he h u m an spirit can be com pared to th e air enclosed w ithin th e em bry­ onic m em branes. If we take its future away from th e in fan t organism at its separation from th e um bilical cord, or from th e spiritual organism at its separation from the body, th en we are left in b o th cases w ith n o th in g b u t a miscarriage, incapable of bringing to m aturity th e germ placed in it. T here are thus only two assum ptions possible: eith er nature m ust have neglected, in this world otherw ise everywhere constructed w ith divine perfection, to im press th e seal of consum m ation on the crown of its creation, th e h u m an being, or the h u m an being’s spiritual individuality m u st also have a future after its separation from the

body, a future in w hich it will have th e leisure [?] to attain its purpose, divine perfec­ tion. T h e m eans nature chooses for the attain m en t of its in ten tion s are, to be sure, entirely h id den from us in very m any cases, and in particular the m ost im portant epochs of hum an ex isten ce— generation, birth, and death— are enclosed in im p en e­ trable m ysteries. But since we know that th e farthest fixed stars send each other light in an unknown fashion, and that a m ysterious bond o f attraction con n ects together all the masses of universal space, why should w e wish to despair o f the possibility o f a con n ection betw een distant spaces and distant tim es in the moral world?139

In w hat remains of the m anuscript, M ayer w ent on to discuss the production of heat in the sun from the fall of fast-m oving “cosmic m asses” and th e transm ission of th at force to us as light; he addressed the contention of Georg Friedrich Parrot th at projectiles cannot be heated by friction; and he argued againt the existence of active vulcanism on the m oon.140 As usual, he sought to buttress his ideas by m eans of an analogy, this tim e betw een m eteorites and blood corpuscles: O ne regards a m eteorite as to o inconsiderable to credit it w ith an im portant pur­ pose in the econom y of the planetary system . But what a small thing is a b lood corpus­ cle, o f which over 100 m illion float in a single drop o f blood! And yet the organism can m ore easily do w ith ou t w hole lim bs than th ese blood corpuscles, on w hich depend its m anifestations of life, its heat, and its m echanical actions. In th e m icrocosm as in the m acrocosm it is th e incalculable num ber [unermefliche(?) Zahl] that is capable of endow ing the tiniest objects w ith th e highest significance.141

M ayer’s attac h m e n t to his m any analogies was such th a t it is hard to see them all as merely literary devices or heuristic illustrations; they seem rather to have con­ stitu ted a wide-ranging web of connections th at len t his ideas broad significance, th at gave them meaning. O ne of th e m ost difficult issues Mayer faced at the beginning of his creative process was deciding w hat forces are and how they are to be m easured. Is m otion a force, and n o t simply, as was m ore usually m aintained, the effect of a force? If so, is it to be m easured by mass tim es velocity or mass tim es th e square of veloc­ ity? (Mayer never m ade the conceptual transition from vis viva to kinetic energy—· th at is, by introducing the factor of one-half— nor was he fussy about the distinc­ tion betw een mass and weight.) Is gravity a proper force? If not, w hat is the force th at causes bodies to fall? Similar uncertainties atten d ed the concept of cause. If forces are causes, and causa aequat effectum, w hat about cases where the effect seems m uch greater than the cause, such as a spark setting off an explosion or a tiny (chemical or physical) stim ulus eliciting a violent response in an organism ?142 Is the problem w ith the definition of cause, with the presum ed equality betw een cause and effect, or with the application of those concepts to the organic realm? W h a t did his basic term s mean, and w hat was his theory a theory of? T h e answers to such difficult questions evolved over tim e. As M ayer p u t the issue in 1851, as far as forces are concerned, the question is not “w hat kind of a thing a ‘force’ is, b u t w hat thing do we wish to call ‘force.’”143

H e achieved th e desired circum scription of the term “force” w ithin two to four years of his initial thoughts on heat and m otion. How to deal w ith causes was a problem th a t occupied him till th e very end of his active intellectual life. His last essay, in 1876, dealt w ith w hat he term ed Auslosung, th e “unloosing” or release of a large effect by a small cause. N ot surprisingly, he began his essay w ith one of his oldest and favorite examples of chem ical change: Very m any natural processes only take place if they are initiated by m eans of an im pulse, and this circum stance is w hat the science of the day calls “u n lo o sin g .” O ne of th e readiest exam ples is certainly oxyhydrogen gas [Knallgas). As is well known, a m ixture of oxygen and hydrogen gas in th e ratio in w hich they yield water enters by itself into no chem ical com bination until the latter is in itiated by m eans of heat or an electric spark or by platinum black. In th e sam e way, when we ignite a m atch by m eans of a little frictional heat and by m eans of this burning m atch initiate a further, arbi­ trarily large com bustion process, so, too, do we have here another sim ple exam ple of “u n loosin g,” and such exam ples confront us close at hand in infinite plenty. Light pressure w ith the finger produces a violent effect w ith firearms, etc., e tc .144

C haracteristic of processes of unloosing was th a t they cannot be defined in term s of a q u antitative relationship betw een cause and effect. Organic phenom ena pre­ sent countless examples of such processes, for example the m ovem ent of a m uscle in response to a nervous im pulse under the direction (perhaps) of the will. Mayer im plicitly likened such physiological processes to the function of a person control­ ling a m achine: he recalled how, as a child, h e enjoyed w atching th e operator of a water-powered sawmill set it in m otion by simply pressing a lever and thereby w ithdraw ing th e sluice gate. M ayer’s concept of unloosing represented th e culm ination of long years of wrestling w ith issues of cause and effect. In a letter to Griesinger in 1844 h e wrote th a t “w ith pedantic logic I cherish th e pious wish th at by cause and effect (in inanim ate nature) one understand either things th a t stand in a quantitative rela­ tionship to each o th er or th a t are not in proportion to each other.”145 His example of th e latter was a spark setting off an explosion. Forces are causes, b u t no t all causes are forces. A principle of the ‘indestructibility of causes’ was not, u lti­ mately, one he wished to defend. Several adum brations of his later distinction occurred in his Organic M otion of 1845. W ith respect to th e phenom ena of m uscular m otion he suggested a dis­ tinction betw een “conditions” and “causes,” betw een “psychic” and “physical” factors: Two different things b elon g to a m u scle’s m anifestation of activity: I) the influence of a m otor nerve as co n d ition , and 2) the exchange o f m atter as cause of th e work perform ed [Leistung], Like the w hole organism, so, too, does the organ, the m u scle, have its psychic [psychisch] and its physical sides; to the former we reckon the influence o f the nerves, to the latter the chem ical process. T h e m ovem ents of a steam boat obey th e will of the h elm sm an and the m achinist.

B ut th e psychic [geistig] in flu e n ce , w ith o u t w h ich th e sh ip w o u ld n o t set itself in m o tio n . . .— it d irects, b u t it does n o t m ove a n y th in g ; c o n tin u e d m o tio n req u ires a physical force, coal . . . . T h e a ctio n of th e m u scle, th e tra n sfo rm a tio n o f ch e m ic a l force in to m e c h a n ic a l effect, is c o n d itio n e d [or d e te rm in e d (b ed in g t)] in a m y sterio u s fash io n by a c o n ta c t in flu en ce th a t, as ex p erien ce show s, p e rta in s to th e n ervous system . Inso far as th e m o to r a p p a ra tu se s d e p e n d to a different degree o n th is in flu e n ce , th e y are d iv id ed in to v o lu n tary an d involuntary. If we im a g in e a ste a m e n g in e of w h ich o n e p a rt w orks as soon as steam is g e n e ra te d , b u t a n o th e r p a rt is only se t in m o tio n as a resu lt of th e m a c h in is t’s co n triv a n c e , th e n we h av e v o lu n ta ry a n d in v o lu n tary m o to r a p p a ra tu se s h e re as well. T h e m a c h in is t is only cap ab le of b rin g in g his in flu en c e to b e a r on th e a p p a ra tu s a t h is disposal by m e an s of a c e rta in e x p e n d itu re of force; b u t th e ex p e n d i­ tu re of force is vanishingly small in co m p ariso n w ith th e m ec h a n ic a l w ork p ro d u c e d , a n d can in general, w ith th e in creasin g p erfe c tio n of th e a p p a ra tu s, b e m a d e sm aller th a n any given m a g n itu d e . In th e sam e w ay w e m u s t declare it to b e n o t only p ossible, b u t even p ro b ab le, th a t w ith o u t [n o tab le] e x p e n d itu re o f a physical force, w ith o u t an electric c u rre n t a n d w ith o u t any ch em ical process a t all, th e in n e rv a tio n ex erts its c o n tro l over m u sc u la r a c tio n . 146

But for th e a d d itio n of a qualifying “n o ta b le ” in 1867, M ayer cam e close to a ssert­ ing a sharp d istin c tio n b etw een th e entirely n o nphysical direction of organic p h e ­ n o m e n a an d th e physicochem ical sources o f force th a t p ro d u ce th e m echanical effect, especially co n sid erin g his use of th e phrase “c o n ta c t in flu e n ce .” S uch a d istin c tio n corresp o n d s closely to th e ta c it d istin c tio n m any earlier physiological w riters m a d e b etw een th e vital force as e ith e r th e directo r of organic processes or th e source of m o tiv e force. For M ayer th e will belongs to th e “realm of fre ed o m ,” w hich is th e b usiness of p h ilosophy an d theology; science pro p er deals w ith th e realm s of necessity an d purposefu ln ess p e rta in in g to th e physical and organic w orlds.147 T h e relatio n sh ip b e tw e e n force an d th e soul was a lo n g -term co n c ern of his. C o n ta c t an d catalytic forces co u ld n o t be b o n a fide forces in M ay er’s sense of th e te rm , b u t th e y co u ld nev erth eless still b e regarded as causes of certain p h e n o m e n a ; th e te rm s co u ld b e re ta in e d as lo ng as th e y were properly u n d e r­ stood: E veryone know s th a t in n u m e ro u s cases c h em ical a c tio n s are d e te rm in e d by th e m ere presen ce of c e rta in su b sta n c e s th a t th em selv es tak e n o p a rt in th e c h a n g e tak in g place. If o n e w ishes, w ith o u t m ak in g any a ssu m p tio n s, to b e sto w a n a m e o n an e sta b ­ lished fact, th e n o n e can d esig n a te by m e a n s o f th e ex pression “c o n ta c t in flu e n c e ” th e role played in su ch c ircu m stan c es by th e m a tte r th a t rem ain s u n c h a n g e d ; as is well know n, o n e is otherw ise also a cc u sto m e d to speak o f “ca ta ly tic fo rc e ” a n d “catalytic e ffe c t”; b u t if by force o n e is su p p p o se d to u n d e rs ta n d only “ th e m e a su rab le cause p ro p o rtio n a l to a m e asu rab le e ffe c t,”’ th e n for u n d e rs ta n d a b le reasons a specific force c a n n o t be a ttrib u te d to th e p h e n o m e n o n in q u estio n .

*A force is called “catalytic” insofar as it stands in no kind of quantitative relationship to the intended effect. An avalanche falls into the valley; a gust of wind or the beat of a bird’s wing is th e “catalytic force” that gives the signal for the fall and brings about the extensive destruction.—T he “catalytic” or “paralytic” aspect of this force refers in the first place to logic, or the law of causality.148 In o th e r w ords, “c a ta ly tic ” pro p erly relates to h ow we use th e c o n c e p t o f cause, n o t h o w w e use th e c o n c e p t o f force. By “p a ra ly tic” h e probably in te n d e d th e w ord’s ety m o lo g ical sen se o f “lo o sed fro m b e s id e .” H e was still search in g for c o n ­ cep ts a n d te rm s c o rre sp o n d in g to h is evolving u n d e rs ta n d in g of th e in te rtw in e d issues, ju st as h e c o n tin u e d to refine th e sco p e o f h is ideas a n d th e field of ap p lic a­ tio n of th o s e c o n c e p ts a n d te rm s. A u slo su n g sto o d a t th e e n d of a d e v e lo p m e n t o f ideas th a t h a d b e g u n w ith th e p a rtic u la rs h eat a n d m o tio n , seen th e c re a tio n of th e general c o n c e p t of force, a n d e n ta ile d a lab o rio u s struggle to co m e to te rm s w ith th e in c o m m e n su ra b le m e a n in g s of cause.

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C H A P T E R

S E V E N ·

Mayer and Naturphilosophie

As I r e c o u n t e d in th e Introduction, this study began as an investigation of the widely accepted belief th a t M ayer’s form ulation of what becam e known as the principle of th e conservation of energy was due in some essential way to the influ­ ence of Schelling’s Naturphilosophie, interpreted primarily as asserting a funda­ m ental unity of th e forces of nature. T he om ission of any evidence supportive of such a claim from the foregoing reconstruction of the context and developm ent of M ayer’s ideas implies th a t I have not found such a contention supported by the available evidence, nor does a satisfactory understanding of M ayer’s work appear to require th e assum ption of such a philosophical influence. O n the other hand, neither th e inadequacy of past interpretations, nor the absence of com pelling evidence, nor even the possible sufficiency of the present historical analysis neces­ sarily entails the im possibility th a t M ayer’s way of thinking in fact owed som e­ thing to Naturphilosophie. T here are, indeed, certain m otifs in M ayer’s writings th at are rem iniscent of topics addressed by some of the principal Naturphilosophen, notw ithstanding the striking absence in his writings of m any of th e betterknown and seemingly more characteristic aspects of Naturphilosophie. T h e issue does n o t, I think, ultim ately lend itself to a categorical determ ination, although one can go qu ite far in circum scribing th e possible extent and significance of such an influence. From a larger perspective, the now alm ost ritual invocation of Naturphilosophie to explain M ayer’s discovery of the conservation of energy is worth addressing as an issue in its own right whose elucidation can help clarify the widely m isunderstood and caricatured nature of th a t early nineteenth-century Germ an philosophical m ovem ent and its relationship to th e science of the day. T h e first person to suggest, albeit guardedly, th a t M ayer’s thinking may have owed som ething to Naturphilosophie seems to have been Salomo Friedlaender in an insightful study of M ayer’s work published in 1905. Associating Naturphiloso­ phie w ith belief in a vital force, Friedlaender (wrongly, as we shall see) took M ayer’s opposition to the latter as evidence of his rejection of the former.1 Never­ theless, he suggested th a t M ayer’s early enthusiasm for the idea of the unity and indestructibility of forces betrayed atavistic traces of Naturphilosophie.2 Friedlaender did not identify just w hat those traces were, b u t w ent on (w ithout clear warrant) to identify as naturphilosophisch M ayer’s lingering disposition to regard th e solar system as a divinely ordered system in w hich force is produced. However, in previous chapters I have argued th at the latter belief resulted from M ayer’s attem p t to make sense of th e then-standard application of the parallelogram of forces to central-force m otions in conjunction with the then-standard reference to the solar system as an organism.

In 1940 Alwin M ittasch asserted m ore forcefully th a t th e characteristically Ro­ m an tic n o tio n of th e “unity of force,” coupled w ith em pirical exam ples of the in terco n n ected n ess of all forces, h ad created a kind of general consciousness of th e unity and tran sm u tab ility of force th a t influenced M ayer during his stu d e n t years. As evidence for the influence of Naturphilosophie h e cited the ostensibly telling words from M ayer’s u n published 1841 paper, “W e can derive all p h en o m ­ ena from a prim itive force [Urkraft].” Two years later Paul D iepgen identified rath er vaguely as naturphilosophisch M ayer’s predilection for analogies and (som ew hat inconsistently) b o th his frequently deductive style of p resentation and th e ten d en cy he evinced even as a youth to leap over th e connecting links of a logical arg u m en t. In his 1959 book on Naturphilosophie in the N ineteenth Cen­ tury, G erhard H e n n em an n asserted, w ith o u t evidence or argum ent, th a t M ayer was unconsciously influenced by th e R om antic n o tio n of th e unity of th e forces of n atu re even th o u g h h e claim ed to oppose Naturphilosophie} As far as th e cu rrent historiography of science is concerned, however, th e largely u n elab o rated suggestions of F riedlaender e t al. are obscure an d forgotten forerun­ ners of th e arg u m ent m ore forcefully and visibly advanced by T hom as Kuhn in a sem inal paper read in 1957 an d published in 1959. K uhn’s now classic “Energy C onservation as an Exam ple of S im ultaneous Discovery” sought to isolate the factors b eh in d th e spate of closely contem poraneous form ulations of concepts akin to energy conservation by com paring th e ideas an d backgrounds of th e twelve m ost im p o rtan t scientists. H e argued th a t there were “m ajor conceptual lacu n ae” in th e accounts of how six of his figures got to som ething like energy conservation, th a t “in th e cases of C olding, H elm holtz, Liebig, Mayer, Mohr, and Seguin, th e n o tio n of an underlying im perishable m etaphysical force seem s prior to research and alm ost u n related to it. P u t bluntly, these pioneers seem to have held an idea capable of becom ing conservation of energy for som e tim e before they found evidence for it.”4 K uhn located “M ayer’s leap ” in th e gap betw een his observation of th e lighterth an -ex p ected color of venous blood in th e tropics and his conclusion “th a t inter­ nal oxidation m u st be balanced against both th e body’s h ea t loss and th e m anual labor th e body perform s. To this form ulation, th e light color of tropical venous blood is largely irrelevant. M ayer’s extension of th e theory calls for the discovery th a t lazy m en, rath er th a n h o t m en, have light venous blood.”5 K uhn’s error here was in trying to get energy conservation o u t of M ayer’s physiological observations and reflections, w hereas w hat M ayer thereby discovered (w ithout any logical lacu­ nae b u t only by invoking b o th a long-held conviction in th e im possibility of m e­ chanical perpetual m o tio n and a heuristic energetic analogy betw een organism s and m achines) was th e equivalence betw een h e a t and “m o tio n .” B oth th e general co ncept of force an d its indestructibility and uncreatability were ideas M ayer ar­ rived at via a h o st of o th er considerations. Kuhn found in Naturphilosophie a possible source for th e kind of m etaphysical conviction h e identified in six of his codiscoverers of energy conservation: “Posit­ ing organism as the fu n d am en tal m e tap h o r of th eir universal science, the Naturphilosophen constantly sought a single unifying principle for all natural phe-

nom ena.”6 T hough Kuhn did no t use the phrase “unity of forces,” he did cite Schelling’s belief in the interconnectedness of the forces of nature. O f apparently greater significance to him was the atten tio n Schelling paid to conversion and transform ation processes, though th a t was no t the way Schelling conceptualized them . Kuhn did not substantiate the assertion th a t Schelling’s teachings “dom i­ nated G erm an and m any neighboring universities during the first third of the nineteenth century,” an overbroad generalization in need of specification, espe­ cially since it is not true of M ayer’s university. Kuhn further m otivated the suggestion th at Naturphilosophie m ight close the explanatory gap in the accounts of Mayer, Helm holtz, Liebig, Colding, and H im by citing what he adm itted were only “biographical fragm ents” relative to each. Thus: “Mayer did not study Naturphilosophie, bu t he had close student friends who did.”7 Only further research, he recognized, could substantiate this hunch. But he argued th at it was significant in this regard th at five of his twelve pioneers were G erm ans, at a tim e w hen G erm any “had not yet achieved the scientific em inence of eith er Britain or France,” an d th at furtherm ore “a sixth, Colding, was a Danish disciple of O ersted’s, and a seventh, H im , was a self-educated Alsatian who read th e Naturphilosophen .”8 Kuhn th u s concluded: U nless th e N aturp h ilo so p h ie in d ig en o u s to th e e d u c a tio n a l e n v iro n m e n t o f th e se seven m e n h ad a p ro d u ctiv e role in th e research es o f so m e, it is h ard to see w hy m o re th a n fifty p er c e n t of th e p io n eers sh o u ld have b e e n draw n from an area barely th ro u g h its first g e n e ra tio n of sig n ifican t scientific productivity. N o r is th is q u ite all. If proved, th e influ en ce o f N aturphilosophie m ay also h e lp to explain w hy th is p a rtic u ­ lar group of five G e rm an s, a D a n e , a n d an A lsatian in clu d es five o f th e six pio n eers in w hose ap p ro ach es to energy c o n serv atio n w e have previously n o te d su ch m arked c o n ­ cep tu a l la c u n a e .9

Kuhn was cautious enough to do no more th an urge the reasonableness of his conclusion as a stim ulus to further research. Given the state of historians’ under­ standing of bo th Mayer and Naturphilosophie when Kuhn wrote his paper, his hypothesis concerning M ayer’s relationship to Naturphilosophie was not unrea­ sonable. Nor was Kuhn alone in failing to distinguish Naturphilosophie from Kantianism , though th a t confusion weakened the cogency of his m ore general hypothesis, especially with regard to Helm holtz. During the 1970s the historian of science who m ost insisted on M ayer’s affilia­ tion with Naturphilosophie was Armin H erm ann. Such a connection was, he said, “dem onstrable,” though he him self consistently om itted th at dem onstration.10 H erm ann som etim es preferred to link M ayer’s work no t so m uch to Schelling’s Naturphilosophie in particular as to the broader school of tho u g h t he term ed “dy­ nam ism ,” which em phasized the ontological primacy of force and the intercon­ nectedness of th e various forces of nature.11 Alas, there is no evidence Mayer ever entertained th e central tenet of dynam ism , the construction of m atter out of oppposing attractive and repulsive forces, or th a t he ever rejected chemical atom ­ ism; nor do th e term s “dynam ic” and “dynam ism ” often appear in his writings. In H erm ann’s m ost elaborated account, however, he argued for M ayer’s debt to spe-

cific ideas of S chelling’s. R eferring to M ayer’s u n published essay of 1841, H er­ m an n wrote: “M ayer here ad o p ted th e Schellingian conception th a t everything th a t h appens in n atu re depends on th e separation and recom bination of polar forces. But he followed Schelling n o t only w ith respect to general principles, b u t also w ith respect to specifics, in particular th e explanation of th e generation of light in th e sun th ro u g h th e force of gravity, through th e m u tu al attra ctio n of p lan et and su n .”12 H e n o ted (w ithout citing any textual support) th a t Schelling had spoken of th e separation of zero in to two opposing forces of equal m agnitude. H ere, at least, H erm ann identified som e of th e m ost naturphilosophisch-sounding aspects of M ayer’s work, although polarities per se played scarcely any role in M ayer’s thinking. H e rm an n ’s consistently brief discussions do n o t evince eith er a d eep u n d erstan d in g of M ayer’s work or a broad appreciation of th e range of M ayer’s likely sources, nor do they address th e crucial question of how specifically M ayer m ig h t have b een exposed to th e putative influence of Naturphilosophie, n or of how its concerns related to problem s M ayer m ight plausibly have been concerned with. Ideas are no t just in th e air, an d one w ants to know how a pro­ fessedly unphilosophical m edical stu d e n t a t th e University of T iibingen w ould have en co u n tered such ideas during th e 1830s, decades after th e heyday of N aturphilosophie. D uring th e last two decades it has been especially D u tch an d G erm an histori­ ans of science who have co n tin u ed to assert the im portance of Naturphilosophie to M ayer’s co nception of th e conservation of energy, usually in term s of belief in th e u n ity of forces, an d always w ith o u t anything approaching a cogent historical analysis.13 N one of these authors seem s to have n o ticed th a t M ayer never m ade an issue of th e u n ity of force(s). T h e focus of his a tte n tio n was rather on the relation­ ship betw een h e a t and m otion, ab o u t w hich N aturphilosophen typically h ad little to say.14 C o n tin u in g to conflate Naturphilosophie and K antianism , N orton W ise argued th a t early n in etee n th -cen tu ry G erm an “Idealist trad itio n s” tau g h t th e in d estru cti­ bility of th e prim ordial m otive forces of nature, and th a t such ideas “form jed] the basis . . . for a tte m p ts such as M ayer’s to en u n c ia te conservation m ore p re­ cisely.”15 But his only textual reference was to K ant’s th en -u n p u b lish ed “O pus p o stu m u m ,” and we are left ignorant of th e ex ten t to w hich N aturphilosophen in fact m ad e an issue of th e indestructibility of force. N or did W ise suggest w hat works M ayer m ig h t plausibly have g o tten such ideas from. His analysis is typical of those th a t, like H e im an n ’s five years earlier, prefer the philosophical analysis of ideas and isolated texts to th e tracing of actual problem s in specific, historically relevant sources.15 N evertheless, W ise did appreciate th e broad historical signifi­ cance of an aspect of M ayer’s works related to his rejection of th e m echanical (i.e., m ode-of-m otion) theory of heat: In refusing . . . to reduce heat (and electricity) to matter, motion, and the forces acting between parts of matter, Mayer maintained the naturphilosophisch notion of force as a sort of substance, now independent of m atter but still having the same status as matter. . . . That the rejection of Naturphilosophie meant precisely the rejec-

tion of such “m etaphysical” force substances in favour of th e m echanics of m atter helps to explain why space-occupying force fields did n ot receive serious consideration in G erm any m uch before 1880. A m echanical eth er provided th e only legitim ate basis for unity.17

W ise h a d his finger o n an im p o rta n t asp ect of M ayer’s th in k in g — th e ontological (“su b sta n tia l”) in d e p e n d e n c e of force from m a tte r— b u t h e was m istaken in asso­ ciatin g su ch an idea w ith N aturphilosophiet w hich te n d e d in part to regard force as ontologically m ore prim itive th a n m atter, in p art to tre a t th e agencies m ore generally know n as im p o n d erab les as special states of m atter. Mayer, on th e o th er h an d , a d am an tly insisted o n th e in d e p e n d e n c e of both ontologically prim itive substan ces, force a n d m a tte r.18 T h e h istorical b ackground to th o se considerations was, as I have argued in earlier ch ap ters, A uten rieth-Iike reflections on th e nature of th e soul, th e vital force, th e im p o n d erab les, and p o n d e ra b le m atter. As w ith th e association of N aturphilosophie w ith b elief in a vital force, so here its association w ith th e n o tio n of a m etaphysical force su b stan ce represents a d isto rte d picture created by its latter-d ay critics. As will b e d e m o n stra te d below, even th e associa­ tion of N aturphilosophie w ith belief in th e u n ity of th e forces of n a tu re represents so m eth in g of a d isto rtio n of w h a t N aturphilosophen actually said a b o u t forces, th o u g h th is d isto rtio n has co m e prim arily from th o se w ho find a positive historical role for N a turphilosophie. Several h isto rian s have, to b e sure, q u e stio n e d th e cogency of th e p u ta tiv e co n ­ n ectio n b etw een N aturphilosophie an d th e conservation of energy. Barry G ow er conclu d ed his 1973 p ap er o n “S p ecu latio n in Physics: T h e H istory and Practice of N aturphilosophie”— still one of th e b e st analyses of th e su b ject— w ith th e judg­ m e n t th a t “ [O e rste d ’s] dynam ical th eo ries o f physical actio n , w ith th e ir em phasis upon th e in te ra c tio n of polar forces, c o n trib u te d little to th e creatio n of a c o n cep ­ tual fram ew ork w ith in w hich th e energy conservation principle could em erge and be u n d e rsto o d . . . . For th is principle involved th e idea th a t som e physical quan­ tity is conserved u n d e r tra n sfo rm a tio n .” 19 H e rb e rt Breger likewise em phasized th a t Schelling’s c o n c e p t of force was n o t am en ab le to q u an tificatio n , an d th a t R o m an tic scien tists d id n o t have th e im p o rta n t co n cep t of m echanical w ork.20 P eter H e im a n n ’s insightful study of M ay er’s c o n c e p t of force and its possible philosophical co n n e c tio n s led h im to th e conclusion th a t N aturphilosophie was unlikely to have played a significant role: T he fundam ental aim of Schelling’s philosophy was to discover certain a priori princi­ ples th a t were inaccessible to empirical cognition. . . . Schelling’s conception of phys­ ics stands in sharp contrast to th a t of Mayer, who sought to render th e concept of force as empirically m eaningful as the concept of m a tte r.. . . Schelling's theory of the polarity of forces as an expression of the tension betw een productivity and its lim ita­ tion has no parallel in M ayer’s writings. T he general thrust of th e writings of the Naturphilosophen such as R itter was to account for phenom enal changes by an appeal to inner essences, and their notions of the unity of nature and th e polarity of forces bear only a rem ote analogy to M ayer’s concept of th e transform ation of forces.21

N ev erth eless, H e im a n n re co g n ized — w ith n o ta b le a m b iv ale n c e— th a t so m e of M a y e r’s c o n c e p ts d o b e a r so m e re se m b la n c e to th o se of N a tu rp h ilo so p h ie, th o u g h th a t re c o g n itio n d id n o t u ltim a te ly m o v e h im far from his previously s ta te d c o n ­ clusion: It seems th at he was familiar with their speculations, and it is possible th at the influ­ ence of Naturphilosophie was so pervasive in this period th at it was implicit in all scientific activity concerned with the unity and conversion of “forces”; indeed, M ayer’s reference to an Urkraft and to the unity of forces suggests an indebtedness to the ideas of the Naturphilosophen. But while such an influence is possible, it m ust be emphasized th at in other respects Mayer’s conception of nature was fundamentally at variance with the ideas of the Naturphilosophert. His m atter-force duality and stress on the concept of force as an empirical quantity suggest that there would be little reason to attribute to Naturphilosophie any substantive role in shaping Mayer’s natu ­ ral philosophy. His intentions were fundam entally opposed to those of the Naturphilosophen, and claims for the influence of their ideas on Mayer’s work m ust therefore be regarded with some suspicion.22 In h is la st p a ra g ra p h H e im a n n ag ain k e p t o p e n th e p o ssibility th a t N a tu rp h ilo so ­ p h ie ’s n o tio n of th e u n ity of forces m ig h t h av e h a d lim ite d in flu e n c e on M a y e r’s o th erw ise m arkedly d iffe re n t n a tu ra l p h ilo so p h y.23 A llow ing for H e im a n n ’s c o n ­ tex tu a lly re stric te d p ic tu re o f b o th N a tu rp h ilo so p h ie a n d M a y e r’s w ork, for th e c o m m o n m is id e n tific a tio n of th e “u n ity of fo rc e s” as M a y e r’s c e n tra l m o tif, an d for th e failure to sp o t th e significance of c o n c e p ts su c h as in d iffe re n c e a n d th e c re a tio n o f force o u t o f n o th in g , H e im a n n ’s a sse ssm e n t was n o t u n rea so n ab le. T h e a tte m p t to se p a ra te M ay er fro m S ch ellin g e t al. in te rm s of a d istin c tio n b e tw e e n e m p iric ism a n d sp e c u la tio n is to o c ru d e to h av e m u c h force. Nor, o n th e o th e r h a n d , d o e s M a y e r’s p re d ile c tio n for an alo g ies by itself im p ly any affinity w ith N a tu rp h ilo so p h ie, especially sin c e M a y e r’s p a rtic u la r analogies are largely w ith o u t any R o m a n tic reso n an ces. A m o n g th e c o n c e p ts m o st c e n tra l to M a y e r’s w ork m o s t n o ta b ly a b s e n t fro m w orks o f N a tu rp h ilo so p h ie (th o u g h im p o r ta n t to K an tian s) was e ffic ie n t causality. As H e rm a n n S c h liite r rig h tly em p h a siz e d , S c h ellin g ’s sy stem was chiefly c o n c e rn e d w ith “form al c a u se s,” w ith fin d in g th e place o f a given p h e n o m e n o n w ith in a s tru c tu re of in te rc o n n e c te d c o n c e p ts. H e q u o te d fro m S c h e llin g ’s Ideas tow ard a P hilosophy o f N a tu re (1797/1803): Explanations take place as little in the philosophy of nature as they do in m athem at­ ics; it proceeds from principles certain in themselves, w ithout any direction prescribed to it (say) by th e phenom ena; its direction lies in itself, and the more faithful it remains to this, the more certainly do the phenom ena appear by themselves in that place in which alone they can be seen as necessary, and this place in the system is the only explanation of them that there is.24 A m o n g th e c o n c e p ts m o st c e n tra l to N a tu rp h ilo so p h ie m o s t n o ta b ly a b se n t from M a y er’s w orks w ere th o s e o f Steigerung a n d S tu fen fo lg e , in p a rtic u la r th e trip a rtite h iera rc h ies of lig h t, electricity, a n d m a g n e tis m (as in S ch ellin g ’s sy stem ), of gravi­ ta tio n , h e a t, a n d lig h t (as in E s c h e n m a y e r’s), a n d of th e forces of m a g n e tism ,

electricity, an d ch em istry (as in W a lth e r’s)— typically in parallel w ith a h o st of o th e r forces, realm s, essences, o r asp ects. Such co ncepts form ed th e ideal stru c ­ tu re w ithin w hich individual p h e n o m e n a acquired th eir significance. Nor, given th e ir preference for th e co n c e p tu a l an d th e q u alitativ e, were Naturphilosophen advocates of th e k in d of q u a n tific a tio n exem plified by M ayer’s a ll-im p o rta n t cal­ c u la tio n of th e m ech an ical eq u iv alen t of h e a t. Any a rg u m e n t c o n n e c tin g M ayer w ith Naturphilosophie th u s faces serious co n ­ cep tu al difficulties. N or is such a case m ad e easier by th e lack of direct evidence co n n e c tin g M ayer to Naturphilosophen or th e ir works. His close friend G ustav R u m elin rep o rted th a t, as of th e fall of 1841, M ayer h a d never read a philosophical book— w hich, even if n o t literally correct, tells us so m eth in g a b o u t M ay er’s scanty b ack g ro u n d in philosophy. W h e n , a t M ay er’s request, R iim elin le n t h im tw o works by H egel, M ayer re tu rn e d th e m after a few days, com p lain in g th a t h e had n o t u n d e rsto o d a single w ord.2’ N or do M ay er’s few disparaging references to Naturphilosophie reveal th a t h e h a d any real a c q u a in ta n ce w ith its doctrines: for him , as for m any of his co n tem p o raries, it h ad beco m e a term o f general abuse applied im precisely to w hat w ere perceived to be m ystically unscientific and spec­ ulative ideas.25 T h a t evidence, by itself, w ould n o t preclude th e possibility th a t M ayer was in flu en ced by som e m ore properly 'sc ien tific ’ work of Naturphilosophie. It is, however, h ard to identify any such work th a t w ould seem to provide a likely c o n te x t for u n d e rsta n d in g any of th e leading ideas an d peculiarities of M ay er’s work, q u ite aside from th e q u e stio n of th e likelihood of his having read it. In an historical analysis su ch as th is, one faces th e pro b lem of w ho to take as represen tativ e of Naturphilosophie. A lth o u g h a m ore exhaustive analysis w ould have to deal w ith th a t issue in a m ore prin cip led an d so p h isticated m anner, I have trie d to choose m ajo r individuals unarguably so identified such as Schelling, L orenz O ken, C arl G u stav C arus, an d P h ilip p F ranz von W alther, plus a few oth ers w ho evinced stro n g ties to th a t m o v e m e n t such as C arl A u g u st von E schenmayer, M o ritz E rn st A dolph N a u m a n n , G eorg Friedrich Pohl, a n d (w ith som e qualifications) Karl F riedrich B urdach. I d o n o t th in k my conclusions ab o u t Naturphilosophie have b e e n d isto rte d by idiosyncracies or u n rep resen tativ e ideas in th e works I chose to review, n o r do I th in k m y selection will be controversial to h isto rian s w ho have som e fam iliarity w ith th e relevant prim ary sources. At th e sam e tim e I have allow ed m yself to skate pragm atically p ast th e otherw ise difficult and im p o rta n t issue of th e legitim acy of iden tify ing an individual as a rep resen ta­ tive of a p articu lar ‘tra d itio n ,’ a lth o u g h I will address th a t issue briefly in ch ap ter

8. A fter a tte m p tin g briefly to id en tify th e leading ch aracteristics o f Naturphilosophie, th e rem ain d er of th is c h a p te r will exam in e w hat specific leading Naturphilosophen h ad to say a b o u t such topics as force(s), th e vital force, a n d th e physiol­ ogy of respiration an d anim al h e a t, thereby providing a basis for com parison w ith M ay er’s th inking; an d it will evaluate th e significance of the naturphilosophisch flavor of c e rta in o f M ayer’s ideas an d usages su c h as Urkraft, Indifferenz, creation o u t of n o th in g , an d th e relatio n sh ip b etw een lig h t and gravity in planetary sys­ tem s. I h o p e th e passages q u o te d from prim ary sources will give th e reader an

ad eq u ate sense of th e style and ten o r of Naturphilosophie, since N aturphilosophie, m ore th an m ost philosophical systems, cannot be understood independently of its peculiar use of language, and since it is im possible to gain a faithful sense of the character of Naturphilosophie from sum m aries and paraphrases alone.

I T h e L e a d in g C h a r a c t e r i s t i c s o f N

a t u r p h il o so p h ie

It will be useful to begin w ith a rough sketch of th e kinds of concepts and topics generally characteristic of works of N aturphilosophie, w ith o u t claim ing th a t w hat follows can be taken as exhaustive or canonical. A lthough o ther authors w ith dif­ ferent purposes would u n doubtedly identify a slightly different set, th e features I have singled o u t were q u ite general, if n o t all present in every single work.27 T he w eighting I’ve given to th eir exposition here reflects bo th th eir relative signifi­ cance to my purposes and their likely (u n )fam iliarity to my readers. T h e m o st renow ned characteristic of Naturphilosophie is surely its speculative character, as exhibited by th e aprioristic deductivism prevalent in (for exam ple) Schelling’s and O ken's writings. N aturphilosophen had a high regard for th e ability of th e h u m an m ind to fathom the deepest tru th s ab o u t th e world. As Burdach p u t it, “th e laws of our th o u g h t are realized in th e external world, since our m ind [■G eist] is only th e reflection of th e world spirit [Weltgeist], O nly thus are we capable of knowing n a tu re .”28 For Naturphilosophen, experience often served pri­ marily to exemplify th e fundam ental principles supplied by philosophical analy­ sis. T h u s th e polarities of electricity and m agnetism illustrated th e kind of funda­ m ental an titheses (Gegensdtze) found th ro u g h o u t nature, b u t the polar n ature of th e activities and forces of n atu re was an a priori tru th in d ep en d e n t of specific em pirical verification. At th e same tim e, however, N aturphilosophen subscribed to a quasi-inductivist ideology of scientific knowledge, according to w hich th e basic tru th s of n atu re— as em bodied, for exam ple, in certain Ur- or C entralphdnomene— could literally be seen (angeschaut). An essential feature of a good th e ­ ory was th u s its A nschaulichkeit, its capacity for being grasped via an im m ediate perception of its fu ndam ental tru th s. O f sim ilar im portance to m any of th em was th e direct experience of certain Fundamentalversuche.29 Accordingly, I find the com m on charge th a t N aturphilosophen ignored experim ent to be an oversim ­ plification. M ore accurate is the general view of Naturphilosophie as opposed to m ath em atics and quantification; such m athem atical n o tatio n as one finds was o ften used in an unconventional and purely symbolic, n o ncom putational m anner. Real physical u n d erstanding was essentially qualitative. Such a stance was in part a reaction to th e m echanistic and reductionist hy­ potheses of m ainstream physics and chem istry (such as atom ism ), especially since th e latter were often highly abstract and m athem atical, devoid of any Anschaulichkeit. As n o ted above from Schluter, N aturphilosophen ten d ed to downplay the efficient causality of conventional science in favor of acausal, merely formal expla­ nations. It is in this context th a t Naturphilosophie’s pen ch an t for analogies m u st be understood: th e parallelism s identified in different realms were no t merely

suggestive, b u t expressed th e essential a n d d eep in terco n n ected n e ss of th in g s— w ith o u t, however, necessarily im plying any actual tran sfo rm atio n b etw een an alo ­ gous e n titie s. T h u s O ken associated th e processes of gravitation, h e a t, and light w ith th e organic system s of bones, m uscles, a n d n erves.30 T h u s for Yelin th e id e n ­ tity of electricity an d m a g n e tism did n o t consist in o n e ’s b ein g reducible to th e other, b u t in th e ir c o m m o n polar n a tu re an d in o th e r analogies in th eir behavior, whereby of special im p o rta n c e was, for exam ple, th e com parison betw een m a g ­ n ets an d th e rm o e le c tric crystals su ch as to u rm a lin e .31 Naturphilosophen did typically believe in th e u n ity of n atu re, an d in th e u n ity of know ledge w ith in a closed system . In som e ways th e system atic c h arac ter of Naturphilosophie was its m o st striking ch a ra c teristic, one w hich d istin g u ish ed it from o th e r stran d s of R o m an tic science: it is im possible to im agine Schelling assenting to G o e th e ’s “N a tu re has n o sy ste m .”32 Naturphilosophen such as Schell ing, E schenm ayer, an d W a lth e r c o n stru c te d elab o rate trip a rtite and hierar­ chical schem as em b ra c in g all n a tu ra l p h e n o m en a. C o m m o n , too, was a m icrocosm -m acrocosm view of th e form al relatio n sh ip b e tw e en h u m a n beings and th e world. Two of th e m o st c h aracteristic te rm s of Naturphilosophie were th e already m e n tio n e d Steigerung an d Stufenfolge— roughly, “raising (or inten sificatio n ) by degrees” a n d “g ra d u a te d progression (or series).”33 O n e th u s o fte n spoke of th e relatio n sh ip o f o n e activity or force to a n o th e r in term s o f th e ir b ein g m an ifesta ­ tions of d iffe re n t pow ers (Potenzen). W a lth e r’s co n cep tio n s were entirely typical of th e genre: If on th e other hand one also considers life in its relation, and thereby as a necessary power of the eternal substance o f natural objects [D inge], th en it still expresses the unity o f activity and existen ce, only no longer the original, b u t rather the synthetic unity of both, i.e., their indifference. O n the one hand, therefore, the series o f powers, as it is present in the real universe, proceeds in this w ay that existence designates the first power (through m atter), or the power with predom inant reality, activity the sec­ ond power (through ligh t), or the power with predom inant ideality, and finally life the third power, in which the first and second, th e ideal and the real, are equal to each other.34

T h e passage also illu strates th e k in d of language th a t relentlessly characterized Naturphilosophie. O n e of th e chief tasks of S chelling’s n a tu ra l p hilosophy was “to derive a d y n am ­ ical Stufenfolge in n a tu re .”35 T h u s for S chelling th e relatio n sh ip betw een m ag n e­ tism , electricity, and th e so-called chem ical process lay in th e degree of separation of th e a n tith e se s p resen t in th e original p ro d u ctivity o f n a tu re, n o t in any reducibility of one to a n o th e r.36 Naturphilosophen paid particu lar a tte n tio n to processes of d ev elo p m en t an d m e tam o rp h o sis, or progressive qu alitativ e change. C o m p a ra ­ tive a n a to m y a n d em bryology w ere, n o t surprisingly, am ong th e research areas m o st favored by th o se to u c h e d by Naturphilosophie. T h u s, for exam ple, th e te n ­ dency to try to u n d e rs ta n d an im al h e a t by co m p aring p h en o m e n a from across th e anim al kingdom , as o p p o sed to analyzing th e physicochem ical relationships w ith in a single organism in a cau se-and-effect m anner.

In ad d ition to “p roductivity/' Schelling also spolce of the “absolute activity" th a t forms th e basis of all e x iste n c e /7 T h e necessary lim itatio n of th a t productiv­ ity or activity produces “an original duality” in n ature of opposing tendencies of expansion and co n tractio n .58 T hus the absolutely fundam ental im portance in all versions of Naturphilosophie of concepts of dualism and polarity. Polarities, polar­ ities, and again polarities. O ne of th e m ost fundam ental was th e opposition b e ­ tween th e prim itive attractive and repulsive forces th a t co n stitu te m atter. Indeed, m atter as an ontologically in d ep en d en t en tity te n d e d to disappear via its con­ struction o u t of opposing prim itive forces (Urkrdfte). N aturphihsophen were strongly attach ed to dynam ism , and typically opposed w hat they saw as an unphilosophical and crudely reductionist atom ism . T h e original duality th a t Schelling et al. posited in nature arose from a prior state of “indifference”: th e process of developm ent was thus one of differentiation of an originally “indifferent” state, of th e creation of heterogeneity o u t of h o m o ­ g en eity /9 As will b e developed m ore fully in section 4 of this chapter, this set of concepts provides th e m ost fruitful lead for establishing a connection betw een M ayer and Naturphilosophie, and hence w arrants a few general exam ples here. For Schelling, life is characterized by a continuously reproduced state of differ­ entiation, unlike th e general tendency toward indifference in th e inorganic world: T h e product, as lo n g as it is organic, can never sink in to indifference. If it w ould su ccom b to th e universal striving toward indifference, th en it m u st first descen d to [the level of] a product of th e lower power. As an organic product it can n ot perish, and w hen it has perished it is actually already n o longer organic. D ea th is return to the universal indifference. For just that reason th e organic product is ab solu te, im m ortal. For it is an organic product just b ecau se it can never co m e to in d ifferen ce in it. O nly after it has ceased to be organic d oes th e product dissolve in to th e universal in­ differen ce.40

For Burdach, th e organism com es into existence “through th e vital activity in an indifferent prim itive m ass [Urmasse],” thereby introducing a basic polarity into its nature: “O rganic form ation is a differentiation of the indifferent, a develop­ m en t of an tith eses th a t co n tin u e to reproduce them selves, th at produce ever new antith eses in them selves.”41 T h e context of W a lth e r’s use of indifference in the following passage offers a rich harvest of m any of th e characteristic them es of Naturphi losoph ie: For th e h um an organism form s n ot only th e m id p o in t, th e actual dynam ical indif­ ference p oin t in the zoological series, b u t it represents at th e sam e tim e th e h igh est m etam orphosis of organic nature in general, and th e cu lm in a tio n poin t in th e c o n ­ su m m ate organization of th e earthly nature of our planet. AU co sm ic co n n ectio n s and configurations are therefore reproduced in it in the sm all, and even light and the perfection o f th e astral b od ies of distant worlds have found th eir radiantly transfigured reflection m th e h um an m icrocosm : for th e divine essen ce o f the universe shines forth in the sam e way o u t of th em all; and they are only different w ith respect to th at w hich

is accidental and alienated from the essence o f things. Since th e ideas of all sensible objects are eternally u n ited and equal to each other in th e absolute, so do the objects, into w hich those ideas have b een sunk as (so to speak) souls into matter, stand in com p lete relation to each other, and th e hum an m icrocosm can b e com pared n o t only w ith the other anim als o f th e earth, but with everything that exists and m oves in the universe. T h e laws of the planetary system , and all cosm ic con n ection s, m ust there­ fore again be found in the organism .42

A lthough A utenrieth was known in his day as a defender of em piricism in phys­ iology— and his writings belonged overwhelmingly to th e m ainstream , non-Rom antic tradition— he, too, occasionally invoked some of th e central m otifs of Naturphilosophie. In com parative-anatom ical contexts he som etim es used the term s Stufen der Entwicklung, Steigerung, and Stufenfolge, though never as part of a grand trip artite schem atization.45 And in both organic and inorganic contexts he frequently spoke in term s of Indifferenz, lndifferenzpunkt, Gegensatze, and pro­ gressive differentiation.44 Am ong those concepts, only indifference played a sig­ nificant role in M ayer’s thinking, and th a t was the concept with the m ost exten­ sive connections to non-R om antic usages in physics and chemistry. To be sure, Mayer also spoke of the neutralization of differences, b u t he never m ade particu­ lar use of th e term inology of antitheses. Since tripartite schem atization was such a characteristic aspect of Naturphilo­ sophie, it will be useful to look at a few, m ore extended examples. T he archetype of sorts was Schelling’s “universal schem a” of the “dynam ic Stufenfolge,” in which he associated w ith th e three realms of organic, universal, and inorganic nature the parallel categories of form ative force (Bildungstrieb or Reproduktionskraft), irrita­ bility, and sensibility (under organic), of light, electricity, and the cause of m agnetism (under universal), and of chem ical process, electrical process, and m agnetism (under inorganic).45 In th e organic realm, at least, there was a kind of com pensatory relationship am ong the three factors, so “that through the whole o f organic nature, as the irritability rises [steigt], the sensibility falls, and as the sensibility rises, the irritability falls,” and the like.46 I have not found th at Schelling so understood th e relationship am ong the physical forces of nature, th a t is, those pertaining to his “universal” and “inorganic” realms. W alth er’s H um an Physiology with Thoroughgoing Consideration o f the Compar­ ative Physiology o f Anim als (1807-1808) divided m edicine into three parts— physiology, pathology, and therapy— dealing respectively with th e theories of life, dis­ ease, and cure: “T hese three parts express w ithin the sphere of this science the three powers [Potenzen] of the infinite, the finite, and the eternal. For life is to be regarded as the infinite, disease as the finite, and cure as the synthesis of both (the third pow er).”47 W alther elaborated an especially complex m ultileveled system of concepts and relationships as “potentiated series” of the “three-part division of the absolute unity of the idea.”48 T he la tte r’s “first reflection” was the division into nature, spirit, and art; n atu re’s “second co unterpart” was th e division into being (m atter), activity (light), and life (the organism ). Being, activity, and life

were in tu rn analyzed into series consisting of the unity of substance (W esen), form, and totality; of the m agnetic, electric, and chem ical forces; and of the tradi­ tional favorites, reproduction, irritability, and sensibility. A late exam ple of this way of thinking is th e O utline o f Nature Philosophy pub­ lished in 1832 by the then sixty-four-year-old T iibingen professor, Carl August von Eschenmayer. Invoking Schelling’s nam e, though in fact introducing his own schem a, Eschenm ayer identified three realms of spirit, life, and nature, each di­ vided into a particular series of three powers: thinking, feeling, and willing; repro­ duction, irritability, and sensibility; and gravity, heat, and light.49 He further correlated gravity with the principles of necessity and the true, heat w ith the principles of life and th e beautiful, and light with th e principles of freedom and th e good.50 He also identified three “planetary powers” of galvanism, elec­ tricity, and m agnetism , b u t I could no t determ ine how they fit into his larger schem a.51 N one of th e specific details from the foregoing samplings is of particular im por­ tance here. W h a t is im portant is the consistent extent to which th e general way of thinking characteristic of Naturphilosophie finds few resonances in any of M ayer’s writings. He never em ployed tripartite conceptual schemas, nor did any of th e central concepts of dynam ism , polarities, activities, Stufenfolgen, and the like play a detectable role in his thinking. M ayer did, to be sure, em ploy m ath e­ m atical no tatio n in an idiosyncratic and primarily symbolic and noncom putational m anner, b u t not, as far as I have been able to determ ine, in a way specifi­ cally identifiable w ith any particular work of Naturphilosophie, and in M ayer’s day it was quite com m on for even m athem aticians to m ultiply and divide with zero and infinity in ways we regard as illegitim ate. Nor does M ayer’s occasional (and in p art strategic) appeal to th e laws of th o u g h t bear m uch resem blance to the a p h ­ orism of Naturphilosophie: Mayer em phasized efficient causality and the notion {common in th e physics texts of his day) of forces as causes; and the law of suffi­ cient reason, which he especially invoked, was no t one I have found any Naturphilosoph to have m entioned. Nor can it be too strongly em phasized th a t Mayer never m ade an issue of som ething like the “unity of forces”: he began w ith a narrow focus on th e relationship betw een heat and m otion, and only gradually expanded the scope of his theory to include o ther forces (a.k.a. im ponderables). O ne can slog through hundreds of pages of Naturphilosophie w ithout encounter­ ing many passages th at even rem otely sound like anything Mayer wrote. W ith th e im p o rtant exception of the concept of indifference and the atten d a n t n o tion of th e creation of antitheses o u t of a null state, th e case for som e kind of general influence of Naturphilosophie on M ayer’s form ulation of energy conserva­ tio n is difficult to sustain. Nevertheless, there are a few specific topics dealt with by several Naturphilosophen having to do with planetary m otion th at do not allow this historiographical issue to be entirely disposed of. Before turning to them , however, we need to consider in more detail w hat Naturphilosophen had to say ab out two subjects of great im portance to Mayer: the n ature of force(s), and the explanation of respiration and anim al heat.

2 F o r c e a n d F o r c e s in N a t u r p h i l o s o p h i e

Since concepts of force and the unity of forces would appear to co n stitu te the strongest ostensible link betw een Mayer and Naturphilosophie— such, at least, has been the general argum ent— let us take a closer look at just w hat different Naturphilosophen had to say on th e subject. In doing so it will becom e clear not only how un settled such concepts were, b u t also the extent to which Naturphilosophen like Schelling and Oken offered largely m aterialistic interpretations of light, heat, electricity, galvanism, m agnetism , and chem ism . For th e rest, they and others were m uch more likely to refer to these agencies as principles, antitheses, activities, and efficiencies than as forces. T he widely held view th a t Naturphilosophie was centrally characterized by a preoccupation w ith forces and their unity has, to be sure, some foundation in historical reality, b u t it is a m isleadingly over­ simplified characterization quite at odds w ith th e textual reality of m any of the works themselves. It has owed its origin, I suspect, in large part to the subsequent centrality of a m ore precise concept of “force” and its retrospective im p u tatio n to a no-longer well understood philosophy of nature. And unless one pays careful attentio n to language, one may wrongly read a discussion of electricity (and so forth) as dealing with forces, when in fact no such general (let alone clear) concept may have underlain the particulars. T h e fact th a t Naturphilosophie’s “forces” in­ cluded things like irritability, sensibility, and some kind of formative force did no t bring th at concept closer to the physics of the conservation of energy, either. Schelling developed his protean ‘system ’ of Naturphilosophie in four principal WOrks originally published betw een 1797 and 1799: Ideas toward a Philosophy o f Nature (1797/1803), On the World Soul; an Hypothesis o f Higher Physics toward an Explanation o f the Universal Organism (1798/1806/1809), First Sketch o f a System o f N atural Philosophy (1799), and Introduction to His Sketch o f a System o f Natural Philosophy (1799). T h e fact th a t none of these works was reprinted b e­ tween (at th e latest) 1809 and 1857/58 (in Schelling's collected works) adds to the unlikelihood th a t Mayer knew them . Nevertheless, they will help define a kind of baseline of views properly identified as naturphilosophisch. In th e first-nam ed book— which, in Schelling’s early estim ation, had of all his works received the m ost atten tio n from natural scientists52— th e author revealed his d eb t to Kant in distinguishing betw een em pirical and philosophical natural science and in characterizing force as a concept belonging essentially to the u n ­ derstanding, th a t is, one which is never an im m ediate object of Anschauung and which is hence out of place in em pirical science: W ith respect to questions as yet still partly in dispute concerning th e nature of heat and the phenom ena o f com b u stion , I follow ed the principle of ad m ittin g absolutely no h idden elem ental substances in bodies, the reality of w hich can in n o way be established by experience. O ne has recently m ingled more or less philosophical princi­ ples in to all th ese in vestigations concerning heat, light, electricity, etc., . . . principles

w hich in and of them selves are already foreign to experim ental n atu ral science and w hich are besides usually so indefinite th a t inevitable confusion arises as a result. T h us in physics nowadays the concept of force is played w ith m ore frequently than ever, especially since one began to d o u b t th e m ateriality of light, etc.; one has indeed already asked several tim es w hether electricity m ig h t n o t perhaps be vital force. AU these vague concepts in troduced illegitim ately into physics I have had, in th e first part of this work, to leave in their indefiniteness, since they can be rectified only philosophically. Here is now th e place to secure for th e concept of fu n d am en tal forces of m a tte r its reality, b u t also its bounds. Force in general is a m ere concept of th e understanding, hence som ething th a t can n o t directly be any sort of object of perception [Anschauung] . . . . T h e fundam ental forces of m a tte r are th u s n o th in g b u t th e expression of those original activities for the understanding, for reflection, n ot th e tru e [thing] in itself, w hich exists only in perception; and thus it will be easy for us to define them w ith perfect com pleteness.5’

Following Kant, th e fundam ental forces of m atter were th e usual attractive and repulsive forces o u t of which m atter is philosophically co n stru cted .’4 Indeed, force and m atter are in such in tim ate association th a t “n eith er forces w ithout m atter nor m atter w ithout forces is im aginable.”” Such an u n d erstanding con­ trasts sharply, of course, w ith M ayer’s central concern to vindicate for force an existence in d ep en d en t of m atter. For Schelling, there is no force in n ature th at is no t lim ited by an opposing force; the two are eith er in equilibrium or in continu­ ous conflict (Sireif).56 T h u s th e dynam ical polarities so p rom inent in Naturphilosophie. It should be kept in m ind, too, th a t th e attractive and repulsive Grundkrafte, th e paradigm atic opposing forces, were forces in th e traditional N ew tonian sense. Such language represents no groping toward a m ore energetic conception of th e term . R eductive analysis into opposing forces was not, however, a feature of Schelling’s trea tm e n t of light and h eat, the phenom ena of which do no t readily lend them selves to a dualistic interpretation, especially before th e discovery of the polarization of light. Instead, he argued repeatedly for their m ateriality in ways rem iniscent of th e im ponderables language of later physicists (as discussed in ch ap ter 4). He introduced th e issue as follows: T h e first q u estion th a t m u st occupy us is this: How are light and h ea t connected? Are they b o th of a com pletely different nature? Is one perhaps cause, th e o th er effect? O r do they differ only in degree? O r is one only th e m odification of th e other, and in th a t case would th e marvellously rapid, easily m obile elem en t of light perhaps be a m odification of heat, a substance [Matene] w hich, as it appears, diffuses w ith diffi­ culty and only gradually in m uch sm aller spaces? T hey do not appear to b e of a different nature; for th e striving tow ard expansion and diffusion is com m on to b o th . B ut one diffuses infinitely faster th an th e other. H ence m ight they b e different in degree? But the greatest h ea t is w ithout light, while

often far less heat is associated with great flame. These presuppositions therefore lead to no reliable result.’7 In ex am ining th e relatio n sh ip b etw een lig h t an d h e a t, Schelling n o te d th a t lig h t produces h e a t w hen it is ab so rb ed by a black surface, su ch th a t th e h e a t p ro d u ced is p ro p o rtio n al to th e resistance th e lig h t ex p erien ces.58 T h a t tran sfo rm a tio n being (im plicitly) p arad ig m atic of th e ir relatio n ship, he conclu d ed n o t only th a t h eat is a m o d ificatio n of light, b u t also— som ehow — th a t light is m a tte r (Materie) and th a t it b ecom es h e a t w h en its elasticity is d im in ish e d .59T h e crucial p o in t here is th a t Schelling did n o t speak of lig h t a n d h e a t as forces, b u t as m aterial su b ­ stances. “T h e m o st general assertio n " we can m ake w ith respect to lig h t is th a t “it is m erely a m o d ificatio n of m a tte r,” th o u g h w h eth e r or n o t light is a distinctive substance o n e c a n n o t say.60 A ccording to Schelling, th e effects of th e sun ta u g h t people th a t lig h t an d h e a t com e from o n e source and are th e only vivifying forces (,belebende Krafte) in th e u n iv e rse .61 H e likened th e expansion of d e ad m a tte r by h e a t to th e expansion of a b u d an d to th e d e v elo p m en t of a h u m a n em bryo b ro u g h t a b o u t by an “in te rn a l, living h e a t.”62 S chelling in tro d u c e d th e c h a p te r o n electricity w ith words th a t suggest he m igh t be a b o u t to a d o p t th e language of force: “So far we have b ec o m e ac­ q u ain te d w ith only one force o f n a tu re , lig h t an d h e a t, w hich could be checked in its action only by th e o p p o sin g en d eav o r of d ead m atte r; now an entirely new p h e n o m e n o n arouses o u r a tte n tio n , one in w hich activity appears to rise up against activity, force against fo rce.”63 In th e ev ent, however, Schelling spoke c o n ­ sistently o f th e “electric m a tte r," occasionally of th e “electric fluid.”64 H e even identified it as “d eco m p o sed vital air.” C itin g exp erim en ts th a t show ed th a t elec­ tricity is capable of calcifying m etals even in m e p h itic airs, h e concluded: “G iven so co m p letely th e sam e effects of b o th — of electricity an d vital air— I d o n o t know w h eth er one can d e m a n d m ore ev id en t proofs of th e ir id e n tity .”6’ H e later su p ­ ported th is in te rp re ta tio n by citing a co n tem p o rary c h e m ist’s q u o ta tio n of La­ voisier's o p in io n to th a t e ffe c t.66 Schelling te n d e d to call m ag n etism a force, b u t he also sa n ctio n ed th e “scientific fictio n ” of “tw o m ag n etic su b sta n ce s.”67 If term inologically S chelling so m etim es app lied th e word “force” to light, h ea t, elec­ tricity, an d m ag n etism , conceptually he h a d (in this early work) n o t broken w ith th e ontology of su b tle fluids. N o th in g b e tte r reveals S chelling’s im precision, b o th term inological an d c o n cep tu al, th a n his in clu sion of water am o n g th e “forces”: “only forces th a t p e n e tra te bodies, su c h as h e a t an d electricity, n o t such as only reach its surface, such as w ater (am o n g o th ers)— w hich are h arm ful to elec tric ­ ity— are capable of w eakening th is [m agnetic] force.”68 In a la te r c h a p te r Schelling re tu rn e d to th e q u e stio n of th e n a tu re o f lig h t and heat. R idiculing th e n o tio n th a t lig h t m ig h t be a particular su b stan ce (eine besondere M aterie), h e asserted th a t “everything we call m a tte r is in d eed only a m odifi­ cation of o n e an d th e sam e m atter, w hich we a d m itte d ly do n o t know sensibly in its ab so lu te sta te o f eq u ilib riu m an d w hich m u st e n te r in to p articu lar relatio n ­ ships to b e know able for us in th is way.”69 A gainst calling lig h t a force was (again)

th e inappropriateness of introducing philosophical term s into physics and th e fact th a t everything we have direct knowledge of could b e called a force. N or is a Lichtmaterie any m ore hypothetical th a n any other kind of m atter. Light can ac­ cordingly be regarded as m atter characterized by a particular ratio betw een the underlying dynam ic forces, one in which th e expansive force m ost strongly pre­ dom inates. A change in th at ratio can cause the m atter of light to en ter into chem ical com bination. In th e sam e vein, any substance can becom e light if its elasticity can b e m ade to equal th a t of light.70 Light was n o t a force; it was a species of dynamically constructed m atter. W h e n it cam e to heat, Schelling now em phasized how it fundam entally differs from light: T h in gs are qu ite otherw ise w ith th e m a tter o f heat [W arm estoff] than w ith light. Light itself appears as m atter of a particular quality, whereas h eat is itself no m atter, bu t merely a quality— m erely a m od ification o f every (no m atter which?) matter. H eat is a particular degree of expansion. T h is state of expansion is n o t peculiar to only one particular matter, bu t can b elo n g to every possible matter. T h us the situ ation here is very different from that w ith light. For up to now we know of only on e m atter as such (vital air and a few that closely resem ble it) that can pass over in to th e degree of elasticity that is accom p an ied by th e p h en o m en o n of light. W e are therefore en titled to speak o f a m atter of light. But every m atter can b e heated in itself directly (through friction), and this n ot only by th e adven t o f an u n ­ known fluid, b u t by a sim u ltan eou s change th at takes place in the body itself. If one now in addition considers that h eat arises in very m any un dou bted cases through a m ere change in capacity, th en on e will be inclin ed to regard heat in general as a mere phenom enon o f th e transition o f a m atter from the m ore elastic to th e less elastic state (as from vaporous to liq u id ).71

H eat is th u s neith er a force nor a particular species of m atter, b u t “merely a p h en o m en o n ,” a “m odification of m atter,” “a quality d ep en d en t on accidental conditions.”72 H e now argued against Scherer’s assertion of th e identity of light and h eat, and countered his argum ents for their im m ateriality.73 M isunderstand­ ing th e concept of h eat capacity, and w ith o u t considering the transform ation of h eat in to anything else, Schelling denied th a t there is any m easure of the absolute q u an tity of heat: “It is no t only in general a mere m odification of o th er m atter, b u t also a m odification for which there is no absolute m easure (hence th e concept of th e capacity of bodies [for h e a t]).”74 Schelling’s next m ajor work, O n the World Soul, for th e m ost part retained this m aterialistic in terp retation of light and heat. T h e first edition of 1798 spoke ex­ plicitly of th e “ponderability” of light; although the second and third editions of 1806 and 1809 did no t use th a t word, and seem ed otherw ise to wish to to n e down th e earlier strongly m aterialistic language, th e au th o r left unchanged a statem ent of his belief in its “m ateriality.”75 H e assum ed th e existence of a Warmematerie, spoke of a W arm efluidum , and postulated the existence of an Urmaterie present in bodies as either light or heat, depending on th e degree to which th e positive,

expansive p rin cip le p re d o m in a te s .76 H e m a d e n o use of th e word K raft in this contex t. W h e n h e d id use th a t w ord, in his d iscussion of electricity, h e ap p lied it to th e positive an d n egative prin cip les w hose reciprocal relatio n sh ip un d erlies and defines th e electrical p h e n o m e n a .77 E ven a t th a t, he d e v o ted a section to an “In ­ vestig atio n of th e P ond erab le Basis of th e E lectrical M a tte r,” a n d w rote: “If th e source of all lig h t th a t we are capable of developing is to b e so u g h t in th e vital air, so, too, m u s t th e electrical m a tter owe its origin to a d eco m p o sitio n of th is air.”78 T h e electrical m a tte r is, like lig h t, a “com pound flu id .”79 Significantly, in exam in­ ing th e relatio n sh ip b e tw e e n h e a t, lig h t, a n d electricity, Schelling looked n o t at tra n sfo rm a tio n s of one in to an o th er, b u t a t sep arate classes of p h e n o m e n a ex h ib ­ itin g analogous p a tte rn s of behavior. As h e c o n clu d ed , “If a n y th in g proves th e identity o f the positive m a tter o f light, o f heat, a n d o f electricity, th e n it is this ag reem en t in th e laws according to w hich, in th ese d ifferen t states of w hich it is capable, it is a ttra c te d or repelled by b o d ie s.”80 Schelling h a d earlier expressed his a ccep tan ce of w h at he to o k to be a fu n d a ­ m en ta l principle of physics, nam ely “to assum e a m aterial principle as th e vehicle of every force in n a tu re .”81 W h a t h e o p posed was recourse to “ab so lu te forces,” as oppo sed to th e “p rim itiv e forces” in tro d u c e d in to science by th e dynam ical p h i­ losophy: They serve namely in no way as explanations, but only as limiting concepts of empirical science, whereby the freedom of the latter is not only not endangered but is even assured, because the concept of forces— since each one of them allows of an infinity of possible degrees of which none is absolute (the absolutely highest or lowest degree)— opens up for it an infinite space in which to manoeuvre, within which it can explain all phenomena empirically, i.e., in terms of the mutual interactions o f different substances.82 T h u s forces b elo n g properly to th e philo so p h ical u n d e rp in n in g o f n atu ral science, w hereas n a tu ra l science itself bases its ex p lan atio n s on th e a ssu m p tio n of m aterial substan ces. S chelling ap p lied th is reasoning to m ag n e tism , th o u g h h e cau tio n e d th a t o n e sh o u ld n o t assu m e a d istin c tiv e m a g n e tic m a tte r.83 S u ch m a te ria l principles c a n n o t, however, explain th e possibility o f an ordered world since th o se p rinciples are th em selv es only possible w ith in su ch a universal system .84 It is th e ord ered d isp o sitio n of th e universal forces of n a tu re th a t a p ­ pears as th e various seem ingly specifically d iffe re n t m ate ria l su bstances. A lth o u g h his lang u ag e is vague, Schelling seem ed to im ply th a t only th e force of gravity is invariable: “O n ly th e general m o tio n of th e u niverse is d e p e n d e n t u p o n etern al and invariable causes; b u t variable causes b etray m a teria l principles; th u s th e m ag n etic dev iatio n s, w hich o n e c a n n o t explain w ith o u t th ereb y a ssu m in g a m a te ­ rial su b sta n c e as active, one w hich is developed or b ro u g h t to rest, deco m p o sed and again c o m p o u n d e d , an d w hich (like a tm o sp h e ric electricty) arises and disap ­ pears.”85 Very few passages in O n the W orld Soul speak directly to th e issue of th e alleged u n ity o f forces th a t is su p p o sed to be such a hallm ark of S chelling’s N aturp h ilo so p h ie. T h e follow ing is th e m o st striking:

Now, since in consequence of the preceding it is undeniable that a graduated series [Stufenfolge] of functions occurs in the living organism— since nature has opposed the animal process with irritability, irritability with sensibility, and thus has orches­ trated an antagonism of forces that m utually hold each other in equilibrium, in that as one rises the other falls, and vice versa— one is thus led to the idea that all these functions are only branches o f one and the same force, and that perhaps the one princi­ ple o f nature that we must assume as the cause o f life appears in them only as in its individual phenomena, just as without doubt it is only one and the same universally distributed principle th at reveals itself in light, in electricity, etc., as in different phenom ena.86 T h e forces of n a tu re w ere th u s seen as expressions o f a c o m m o n u n d erly in g d u a l­ ism: it is th a t d u alism th a t runs th ro u g h o u t n a tu re , n o t a c o m m o n a n d self-sub­ sisting force so m eh o w tra n sfo rm e d in o n g o in g physical processes from one form in to an o th er. S ch ellin g ’s explicitly self-styled works o f N a turphilosophie— th e First Sketch an d th e su b se q u e n tly p u b lish e d Introduction th e re to o f 1799— c o n tin u e d his u n ­ resolved a tte m p t to co m e to te rm s w ith th e p ro p er ontology of n atu re , in p a rtic u ­ lar th e c o n n e c tio n b e tw e e n force an d m atter. (N ote th a t S chelling did n o t choose to rep rin t e ith e r of th e se tw o works as h e d id th o se p u b lish ed d u rin g th e previous tw o years. S oon a fte r 1800 his p h ilo so p h izin g to ok a d ifferen t tu rn .) A t tim es his “dynam ical p h ilo so p h y ”— in its allow ance of “n o special m a teria l su b sta n c e s” to explain lig h t, h e a t, electricity, an d m a g n e tis m — ap pears to ex p o u n d an ontology of pure force: “AU original (i.e., all dyn am ical) p h e n o m e n a of n a tu re m u st be ex p lain ed in te rm s of forces th a t inh ere in m a tter even a t rest (for even in n a tu re ’s rest th e re is m o tio n ; th is is th e ch ief p rin cip le of th e d y n am ical philosophy): those p h e n o m e n a — e.g., th e electrical— are th u s n o t phenom ena [E rscheinungen] or ef­ fects of p a rtic u la r in d iv id u al m a te ria l su b stan ces, b u t changes in th e existence [Bestehen] of m a tte r itself.”87 In his c o n c e p tio n of th in g s h ere, th e essential p ro p ­ erties of fluids p ro v id ed h im w ith an analogy ap plicable to n a tu re ’s original co n ­ stru ctio n : fluids are form less an d in d e te rm in a te a n d th u s close to th e in d e te rm i­ n a te source of all p ro d u ctiv ity ; a n d in fluids, a ctio n s a n d a ttra c tio n s are th e sam e in all d irectio n s. F ro m th is h e co n clu d ed : The most original and most absolute combination of opposing actions in nature m ust accordingly produce the most original fluid, which, since that combination takes place constantly (the act of organization is constantly in motion), will represent itself as a universally distributed entity [Wesen] which absolutely opposes the nonfluid (the rigidity) and which strives continuously to fluidize everything in nature. (This principle is called principle o f heat, which is accordingly not a simple sub­ stance [Substanz], no sort of m atter at all, b u t always only a phenomenon of the constantly diminished capacity (of the original actions for each other), and it is there­ fore proof in nature of the ever persisting process of organization.— New theory of heat in accordance with these principles.)88

Similarly, Schelling reasoned th a t m a tte r is n o t sim ply given in n a tu re as a p rim i­ tive entity, b u t is so m e th in g th a t has b eco m e w hat it is— everything in n a tu re is “ein G ew ordenes”— as a c o m b in a tio n of th e p rim itiv e actions: “T h u s there exists in n a tu re absolutely n o p rim itive substance [U rstoff\ o u t of w hich everything m ig h t have become— roughly as th e an cien ts im agined th e elem ents. T h e only tru e prim itive su b stan ce are th e sim ple actions. T h u s there also exist in n a tu re no originally u n d eco m p o sib le, i.e., really simple m aterial substances [wirklich einfache M a terien ] .”89 N evertheless, desp ite th e a p p aren t prim acy of forces and actions— Schellingw as n o th in g if n o t in co n sisten t in his use of te rm s— th e original prim itive fluid (and its m an ifestatio n as h e a t a n d electricity) cam e m ore and m ore to look like a conven­ tional subtle fluid, allying S ch e llin g w ith th e plethora of a eth e r philosophies devel­ oped th ro u g h o u t th e e ig h te e n th century.90 C on sider his in tro d u c tio n of heat: T h e m a tte r of fire (or of h e a t) is fam iliar to us as th e original p h e n o m e n o n of th e ab so lu te fluid. T h e fo rm er appears to arise o r to disap p ear w here a m ere q u a n tita tive d ecrease or increase m cap acity (e n la rg e m e n t or d im in u tio n m v olum e) takes place. T h e m a tte r of h e a t ap p ears as sim ple, a n d as yet o n e has b e en able to perceive w ith it n o d u ality or d eco m p o sito n in to o p p o sin g a ctio n s, as, e.g., w ith electricity. Just th is is th e proof th a t in th is m o s t original of all fluids th e m o st c o m p le te c o m b in a tio n a p ­ p ears still undisturbed. O n th e o th e r h a n d , even th e lig h te st c o n ta c t o f h etero g e n e o u s bodies (in galvanism a n d o th e r recently p erfo rm ed ex p erim en ts) p ro d u c e s p h e n o m e n a of electricity, an d since h e a t as well as elec tricity are ex cited by m e a n s of friction (c o n stan tly rep eated a n d in ten sified c o n ta c t), it th u s ap p ears th a t w ith every collision of d iffe re n t bo d ies th e ab so lu te fluid th a t p erm e a te s all o f them , (because it endeavors to fluidize every­ thing) is displaced b o th m ech a n ically o u t o f e q u ilib riu m a n d dynam ically o u t of its original co m b in a tio n T h e fo rm er p ro d u ces th e p h e n o m e n o n o f h e a t b e c o m in g free, th e la tte r th e p h e n o m e n o n o f excited electricity. A nd th e re exists really a lm o st no ch em ical process in w hich h e a t arises or d isap p ears t h a t do es n o t also show traces of ex cited electricity; closer a tte n tio n still has m u c h to teac h h ere. N o t to m e n tio n th e fact th a t in very m an y cases electricity m a n ife sts th e sam e effects as h e a t, a n d th a t bo d ies b eh av e th e sam e way w ith resp ect to th e ir c o n d u ctiv e pow ers for b o th .91

N ote th a t th e a p p a re n t absence of duality shown by th e m a tte r of h e a t was here in te rp re te d n o t as evidence for its n o n p o lar n atu re, b u t for th e com p leten ess o f th e co m b in a tio n of prim itive forces in it. T h e difference betw een h e a t and elec­ tricity was a ttrib u te d to th e degree of d istu rb a n c e of th e eq u ilib riu m of th e c o m ­ p o n e n t forces. N o te, too, th a t alth o u g h this ren dering of th e sense of the passage required m e to speak ju st now of “forces,” th e w ord does n o t ap p ear in th e original text. W h e n it cam e to h eat, Schelling still co n sistently spoke of W a rm e sto ff and W a rm em a terie92 T h e re are, to b e sure, a few passages ripe for q u o tin g as evidence for Schelling’s insisten ce o n th e u n ity of forces. T h e follow ing is one of th e b e st from th e two works presently u n d e r discussion:

T hus instead of th e unity o f the p r o d u c t . . . we have now a unity o f th e fo rce of production throughout all of organic nature. It is, to be sure, not on e product but rather one force that we only perceive checked at different stages of th e p h en o m e­ non. . . [*] *

And it w ould thus th en be about tim e to exhibit that graduated series in organic nature as well, and to justify the idea that th e organic forces— sen sibility, irritability, and form ative force— are a ll only branches o f one force, just as w ithout dou b t as in light, electricity, etc., only one force appears as in its different phenom ena.93

N ote th at in this conceptualization, light, electricity, and so forth are in a sense n o t them selves different forces, b u t only the different m anifestations of one com ­ m on underlying force— the same force th at, raised to a higher power, appears in th e organic realm as the familiar sensibility, irritability, and so forth. In accor­ dance with this conceptualization, Schelling more often spoke of the com m on fundam ental dualism or antithesis th a t underlies th e prim ary phenom ena of n a­ ture. He had no clear or consistently deployed doctrine of force, let alone one th at em phasized transform ations, equivalences, or quantitative measures. C om pare th e following: “T h e antitheses occur in the interior of the universe, b u t all these antitheses are nevertheless only different forms into which is transform ed the one prim itive antithesis [Ur-Gegensatz] th at extends itself in infinite ramifications throughout all of nature— and thus th e universe in its absolute identity is never­ theless only the product of one absolute duplicity.”94 And again the following: T h us the chem ical p h en om en a, just like th e organic, confront us w ith the question of the ultim ate origin of all duplicity. . . . It is th us o n e universal dualism that runs through all of nature, and the individual antitheses we perceive in th e universe are only sh oots . . . o f that one prim itive antith­ esis. B ut w hat has that prim itive antithesis itself produced, produced ou t of the univer­ sal identity of nature? . . . But to produce heterogen eity m eans to create duplicity in identity. But unity in dichotom y only exists where that w hich is h eterogeneous attracts itself, and d ich otom y in unity only exists where that w hich is h o m o g en eo u s repels itself. . . . But this production o f the h eterogeneous out of th e h o m o g en eo u s and o f the h o m o ­ gen eou s out of the h eterogeneous we perceive in the m o st prim itive fashion in the phenom ena of m a g n etism . T h e cause of u niversal m a g n e tism w ould th u s also be the cause o f the universal heterogeneity in hom ogeneity an d hom ogeneity in h eterogeneity.95

In Schelling’s view of the idealized productivity of nature, it was through m agne­ tism th at an original antithesis entered nature; the question then was how, ou t of this original antithesis, all the other individual antitheses cam e into being.96 His goal was to prove a priori "that it is one and the same universal dualism which, from the magnetic polarity on through the electrical phenomena, ultim ately loses itself in

the chem ical heterogeneities and which finally reappears in organic na tu re.”97 T h e goal of S ch ellin g ’s N aturphilosophie was to discover th e a b stract d ev elo p m en tal schem a acco rd in g to w hich N a tu re p ro d u ced (and produces) its full range of “p ro d u c ts”— th e histo rical echoes h ere are of S p in o za’s natura naturata a n d natura naturans— by assu m in g so m e kind o f ch eck (H em m ung) to oppose th e origi­ nal expansive p ro d u ctiv ity of n a tu re . As h e su m m a rize d his overall co n c ep tio n of th is process in his last m ajo r work of N aturphilosophie, T he initial disposition [erster Ansatz] toward original production is the limitation of productivity by the original antithesis, which is still distinguished as an antithesis (and as the condition for all construction) only in magnetism; the second stage of production is the alternation of expansion and contraction, which is still visible as such only in electricity; the third stage, finally, is the transition of that alternation into indifference, which is still recognized as such only in chemical phenomena. M agnetism, electricity; and the chemical process are the categories of the original construction of nature— the latter withdraws itself from us and lies beyond perception [Anschauung], the former are that which is thereof residual, stable, and fixed—the universal schemata of the construction of matter. And—in order to again close the circle here at the point from which it began— as in organic nature the secret of the production of all o f organic nature lies in the graduated series of sensibility, irritability, and formative force, so does the secret of the production of nature out of itself He in the graduated series of magnetism, electric­ ity, and the chemical process, as it can also be distinguished in the individual body.98 G egensatz, D ualism us, D u p licita t, Polaritat, P ro duktivitat: su ch were th e cen tral m otifs o f S ch ellin g ’s N aturphilosophie. It is h ard to escape th e conclusion th a t h isto ria n s’ p re o c c u p a tio n w ith force as th e supposedly cen tral c o n c e p t of N aturphilosophie represen ts a b iased retrospective reading of th e original texts. N o r is th a t co n clu sio n lim ite d to S ch ellin g ’s works. L a n d sh u t professor of m e d ­ icine an d surgery P h ilip p F ran z von W a lth e r’s H u m a n Physiology p o sited an ab so ­ lu te su b sta n c e m a d e u p of activity a n d being: th e word m a tte r accordingly desig­ n a te s an excess of b e in g over activity, lig h t th e excess of activity over being.99 Force was n o t one of W a lth e r’s g u id in g concepts. Z u ric h physiology professor L orenz O k e n ’s Textbook o f N ature Philosophy pos­ ite d an a e th e r as th e fu n d a m e n ta l cosm ic U rm aterie th a t, c o n stitu tin g tim e, space, a n d das schwere Urwesen, is n o th in g less th a n G o d ’s etern al p o sitio n an d first m a n ife sta tio n in m aterial reality; it is th e “U rsubstanz (= 0 T - ) . ”100 T h ro u g h th e se p a ra tio n of th e a e th e r in to polar m asses it beco m es denser, h eav ­ ier, a n d m ore m a te ria l in a process conceived as taking place via th e fixation (Figierung) of a d e te rm in a te pole in a d e te rm in a te m ass of th e a e th e r.101 A side from th a t fixation, th e a e th e r itself exists in a sta te of indifference, and it strives to tran sfo rm m a tte r in to an in d iffe re n t s ta te .102 A lth o u g h I ca n n o t follow th e reason­ ing— such as it m ay have b e e n — O ken asserted th a t it is th ro u g h th e activity of lig h t th a t th e a e th e r congeals in to m atter, th e lig h t th ereb y “dying” a n d “b e c o m ­ ing d ark e n e d .” 103 T h e n e x t “d ark en in g ” of light, its im m e d ia te tra n sitio n in to m a tte r, p ro d u ces oxygen, h e re also te rm e d “corporeal lig h t.”104 H e a t was inter-

preted as an act of m otion of th e Urmaterie: “A m aterial substrate does to be sure underlie heat, as it does light, b u t this substrate does not h ea t and illum inate; rather, th e m otion of th e substrate heats, and only the tension of th e substrate illum inates.”105 In accordance with O ken’s ontological continuum , m atter and heat are transform able one into th e other: “T h e developm ent of h eat by a body is not a pressing out of a substance lying w ithin it and foreign to it, b u t a dissolution [Aufgehen] of m atter itself into heat. M atter does n o t develop or yield heat, it rather becom es h e a t.”106 T h e aether being so rare, th e loss in w eight experienced by a glowing body is negligible, though “philosophically” real. N ote th a t such a conception m akes problem atic any principled notion of th e conservation of (pon­ derable) m atter. T hus Lorenz O ken, one of the best known and m ost influential of all th e N aturphilosophen, defended in his Textbook o f N ature Philosophy a worldview m ore in the spirit of m aterialistic aetherial natural philosophies th an of force-based dynam ism . Force was simply no t one of his central concepts. Eschenmayer, for his part, approved of O ken’s concept of aether as entailing the “sub­ stantiality” and “m ateriality” of the fundam ental forces.107 Nor did a conception of force underlie D resden professor of m edicine Carl G ustav C aru s’s natural philosophy. In a review of A u ten rieth ’s Views on the World o f N ature and the L ife o f the Soul, published in 1837, C arus criticized the com m on notion of forces as som ething conceptually added to bodies in order to explain the phenom ena, and he attacked the notion of force as an objective entity separate from th e body.108 H e elaborated his views on force th e next year in the first vol­ um e of his System o f Physiology, which, like m ost physiological works of the period, paid particular a tte n tio n to fundam ental questions of ontology and the categories of explanation. He there criticized th e concept of force as “a purely subjective concept” th at, abstracted from th e objects undergoing change, has wrongly been m ade into an object itself.109 Echoing Oken, C arus w anted to re­ place th e words M aterie and Substanz with Aether, which, h e argued etymologically (“άειθέω , to be in eternal m o tio n ”), contains in itself th e idea of intrinsic m otion: T hus th e aether, or the aetherial substance, in this sense, is to be acknow ledged as som eth in g that to be sure exists nowhere in a sensibly perceptible fashion, b u t as som eth in g that is nevertheless absolutely om nipresent, as that w hich, as so m eth in g indifferent, underlies every how ever different and individual object, con seq u en tly as that ou t of w hich continuously proceed the differentiations th at represent in every m om en t th e order of th e universe, and back in to w hich th e latter is con tin u ou sly transform ed.110

W h a t he term ed das All-Leben proceeds as a revelation of th e divine being in the continuously repolarized aether.111 Addressing him self to th e issue of th e sup­ posed antithesis betw een force and m atter, an antithesis th a t appears in physiol­ ogy as th a t betw een activity and organ, C arus effectively dism issed th e concept of force from science as a purely subjective representation. His words recall Schelling’s similar sentim ents:

Now, if we wish to consider all of this properly, then upon closer exam ination it m ust also very soon becom e clear that, as soon as we speak of th e activity or force of an organ, we thereby designate n oth in g b u t the series of certain tem porally succeeding changes in the state o f this organ itself, in that we separate off and distinguish this sequence just in the m ind [eben im G eisf]— i.e., artificially and merely intellectually— from the states th e m se lv e s.. . . O ne should therefore at least never forget, when we speak of the force of a thing and im agine this force for the m om en t as som eth in g d istin ct from the thing, th at this is a com pletely subjective notion, with which we may to be sure at least have the use of [a] more convenient and concise expression, just as with m any other subjective n o ­ tions, and w hich w e may in particular indeed well em ploy a s a measure o f the m ini­ m um and m axim um o f th e changes o f a t h in g ,. . , as long as w e thereby take care not to lose sight of the actual state of affairs o f the matter. N evertheless we may in no way grant objective truth to this expression.112

Kant follower Heinrich Friedrich Link objected to C arus’s dismissal of the con­ cept of force: “T he au th o r rightly criticizes the antithesis of m atter and force, b u t he ignores th e simple conclusion th at force is not distinct from m atter in order to say th at force is nothing.”113 Bonn professor of m edicine M oritz E rnst Adolph N aum ann’s heavily naturphilosophisch work Pathogeny of 1840 expounded another vaguely m atter-bound conception of light, heat, electricity, and m agnetism . Here again one looks in vain for a regularly em ployed general term for these four principal agencies. (Works of Naturphilosophie did not as a rule refer to them as im ponderables, as did m ain­ stream scientists and, following them , Mayer.) For N aum ann they were “phenom ­ ena th at indicate the state of m atter passing or about to pass from one form into another.”114 They were to be regarded as “properties of m a tte r” with respect to its change of form .lb Even if, for the rest, N aum ann tended to employ less m aterial­ istic and more idiosyncratically unintelligible language, it remains the case th at force in o th er than a New tonian sense was no t one of his basic concepts, and he did not regularly so designate electricity et al.116 Nor did force (Kraft, vis, or whatever) play a central role in the natural philoso­ phy of Georg Friedrich Pohl, the m ost prom inent representative of Naturphilosophie in physics and chem istry during the 1820s and 1830s.117 In a book devoted to m agnetism , electricity, and chem ism — th e three “m om ents” of the efficiency (Wirksamkeit) of nature— Pohl for the m ost part used no generic term to charac­ terize their com m on class m em bership; when he did, he preferred activity (Thdtigkeit) .118 T he word “force” appeared only once in his book: figuratively, as th e “force of th o u g h t.”119 H e expounded his natural philosophy a t greater length in his 1837 inaugural address as professor of physics at Breslau, On the Heretofore Sought-For Principles as Well o f General Physics as o f Its Chemical Part in Particu­ lar. He began by criticizing the usual practice of assigning different classes of phenom ena to “various kinds of efficient forces and powers as the causes of [the phenom ena].”120 Such a procedure leaves th e phenom ena w ithout any fundam en-

tal unity, ju st as if o n e w ere to assu m e a sep arate force (vis) for seeing, hearin g , e tc., w hile igno rin g th e efficiency (or efficien t power, efficientia) of th e m in d th a t perform s th o se diverse a c tio n s .121 A d e e p e r u n d e rsta n d in g of n a tu re th u s requires th a t w e have a firm m e n ta l an d p e rc e p tu a l grasp of th e “u n ity of th e actions or primary efficiency” th a t rem ain s o n e a n d th e sam e th ro u g h all th e form s, degrees, an d states in w hich it is m a n ife st. 122 P o h l’s c e n tra l c o n c e p t was ju st th a t efficientia primaria, w h a t h e m ig h t have te rm e d die ursprungliche N aturw irksam keit h a d he b e e n w riting in G e rm a n . H is im age, as vividly naturphilosophisch as it was vague, was of a “prim ary fu n c tio n ” u n fo ld in g in c o n tin u o u s activity in w hich all p h e n o m ­ en a are u n ite d a n d w h ich unlo o ses o n e m o tio n of th e “universal efficency.”123 T h e “activity o f th e p rim ary efficiency,” th e source of th e u n ity of th e p h e n o m e n a of n a tu re , is c o n stra in e d b e tw e e n tw o o p p o sin g te n d e n c ie s or m o m e n ts, one urging forw ard (or positive), th e o th e r restrain in g (or n e g a tiv e ) .124 T h e efficientia univer­ salis (as h e so m e tim e s te rm e d it) an d its tw o active a n d o p p o sin g m o m e n ts are jo in ed in in d isso lu b le unity. A lth o u g h h e agreed th a t th e m in d c a n n o t conceive of force w ith o u t m a tte r or m a tte r w ith o u t force, h e explicitly re je cte d th e fundam e n ta lity of K an tian d y n am ism an d asserted th a t force a n d m a tte r are aspects of a th ird p rim itiv e entity, th e efficacitas (or efficientia) prim aria .125 M atter, w hich is sim ply th e low est specific d e te rm in a tio n of th a t prim ary efficiency, can be b ro u g h t in to ex istence a t any tim e an d anyw here in sp a c e .126 N o t force b u t a p rim itiv e activ e polarity— h e also spoke of an “a b stra c t polar im p u lse [conatus]”— was P ohl's cen tral c o n c e p t, an d it was in te rm s o f th e ir fu n ­ d a m e n ta l p o larity th a t th e d iffe re n t realm s a n d p h e n o m e n a of n a tu re are u n i­ fied .127 H is lang u ag e o m itte d all m e n tio n of force ju st w here one m ig h t ex p ect to find it: h e spoke o f th e “p h e n o m e n a ” of lig h t an d colors, th e galvanic “c o n ­ cu ssio n ,” an d ch em ical “activity.” 128 T h e electrical “e ffe c t” or “im p u lsio n ” or “in ­ c ite m e n t” was now a conatus, now a nzsus.129 A nd a lth o u g h h e n o te d ce rta in sim ­ ilarities b etw een electricity a n d m a g n e tism , su ch as th e ir relatio n sh ip to m etallic co n d u c to rs, h e w arn ed strongly ag ain st assu m in g th e “ su b sta n tia l” id e n tity of electricity an d th e m a g n e tic an d ch em ical actions; such id e n tity as th ey h a d lay in th e ir c o m m o n polar n a tu re (as Yelin, too, h a d argued): O ne m ay therefore in no way approve o f the com m on opinion according to which electricity is considered to b e th e identical and substantial cause of b o th th e m agnetic as well as th e ch em ical action. For in truth the electrical and m agn etic activities, although closely con n ected , nevertheless differ on e from the other by a w ide measure of opp osition , and enjoy n o other id en tity than th at by w hich are produced, as of one and the sam e chem ical activity, diam etrical polar im pulses as from a co m m o n center bu t tending in opposite directions, just as w ithin the entire com plex of earth and atm osphere, w ith ch em ical activity everywhere in force, th e m agn etic im pulsion is only strong where th e electrical is weak, and vice versa. 150

As th e rest o f th e p arag rap h m a d e clear, w h at h e m e a n t by th e last se n te n c e was th a t electrical activity occurs prim arily in th e e a r th ’s c ru st a n d a tm o sp h ere, m a g ­ n e tic activity in th e e a rth ’s m etallic core. H e was n o t talking a b o u t th e transfor-

m a tio n of o n e in to th e o th e r or som e k in d of m u tu a l lim ita tio n w ith respect to th e m ag n itu d e of th e ir jo in t effects. It is very h ard to im ag in e w hat kind o f stim u la tio n M ayer m ig h t have g o tte n from th e tre a tm e n t (or n o t) of force in works such as th e se . W ith th e exception of M ay er’s (for h im ) u n u su a l use of th e te rm U rkraft in his first (u n p ublished) essay of 1841 a n d in a le tte r of 1844, n e ith e r th e general term s of discourse n o r th e specific pro b lem s add ressed b e a r any striking affinity w ith M ay er’s work. N or did works of N aturphilosophie, unlike th e works of m a in stre a m science discussed in Part Two, tre a t th e im p o n d erab les in ways suggestive of th e issues of ontology and creation th a t I believe stim u la te d M ay er’s reflections. As for th e association of M ayer w ith N aturphilosophie via b elief in th e su pposed u n ity o f forces, such a co n cep t d id n o t strikingly ch aracterize either party.131

2.1 V ita l Force M any critics, g oing back a t least to th e tim e of L iebig and H elm h o ltz , have associ­ ated N aturphilosophie w ith vitalism an d th e b elief in a vital fo rc e.132 As we saw, F ried laen d er took M ay er’s o p p o sitio n to th e vital force as evidence of his rejection of N aturphilosophie. S u ch an association is, however, b ased on a m isu n d e rsta n d ­ ing of N a turphilosophie’s fu n d a m e n ta lly organicist w orldview a n d its rejection of a m e c h a n istic view of th e physical world as essentially dead. H erm an n S chliiter has given an excellen t analysis of th e issues in his book, T h e Sciences o f L ife be­ tween Physics a n d M etaphysics (1985), w hich deserves to be m ore widely known. As h e p o in te d o u t, even if vitalists m a in ta in e d th a t th e exp lan atio n of life requires th e a ssu m p tio n of a special vital force su p e ra d d ed to th e otherw ise d ead m e c h a ­ nism of th e physical w orld, th ey nev erth eless agreed w ith m ech an ists th a t th e m aterial world is in a sense intrinsically in a n im a te , in capable of self-m ovem ent. N aturphilosopheni for w h o m th e w orld is itself a kind of organism c o n tain in g intrin sic pow ers of self-m o v em en t, h a d n o n eed of such a “secondary a n im a tio n [.Belebung] by m ean s of a vital force.”133 A lth o u g h S c h lu te r’s conclusion will re­ quire som e q u alificatio n for S chelling, it is a reasonably accu rate g en eralizatio n for N aturphilosophie overall. Already in th e in tro d u c tio n to his first work of N aturphilosophie Schelling re­ jected th e im age of an organism as a m a c h in e or a chem ical laboratory an d argued against th e n o tio n of a vital force capable of som ehow rem oving th e organism from th e n o rm al laws of ch em istry.134 In S chelling’s eyes, b elief in a vital force seem ed to h o ld o u t h o p e for an ev en tu al physical ex p lan atio n of life, w hereas he believed in th e h ig h e r directive agency of spirit. It was his O n the W orld Soul of 1798, how ever, th a t c o n ta in e d S chelling’s m o st extensive critiq u e of th e vital force, p a rt o f w hich re p e a te d his earlier reasoning: How does nature bring it about that the chemical process active in the animal body never oversteps the limits o f organization? Nature cannot (as one rightly maintains against the defenders of the vital force) suspend a universal law, and if chemical

processes take place in an organization they m u st proceed according to the same laws as in dead nature. How does it happen th a t these chem ical processes always reproduce th e sam e m a tte r an d form, or by w hat m eans does natu re o b tain th e separation of the elem ents whose conflict is life and whose union is death?15’ T h e c o n te x t o f th e se reflection s w as a con sid era tio n of “th e o p p o sin g principles o f an im al lif e ,” p rin cip les th a t S ch ellin g, as u sual, so u g h t to u n d erstan d in term s o f a n alogies draw n from oth er realm s o f p h en om en a : To every positive principle in th e world there stands . . . opposed a negative one: thus th ere corresponds to the positive principle of com bustion a negative principle in the body, to th e positive principle of m agnetism a negative one in th e m agnet. T h e basis [Grund] of th e m agnetic phenom ena lies n either in th e m agnet nor outside th e m ag­ n et alone. T h u s there m u st correspond to th e positive principle of life outside animal m atter a negative principle in this m atter, and thus here, too, as elsewhere, tru th lies in the u nion of b o th extrem es.156 N o t a unitary vital force, b u t a fu n d a m en ta l a n tith esis is th e basis o f life. W h a t in th e foregoing passage resem b les an A ristotelian d istin c tio n b e tw e e n form (active, p o sitive) and m atter (passive, n egative) represented for S ch ellin g th e a n tith esis of freed om and law fu ln ess, th e u n io n o f w h ich in N a tu rphilosophie a v o id ed th e u n ­ accep ta b le im p lica tio n s o f b o th vita lism and m ec h a n ism , th o u g h S ch ellin g did n o t u se eith er o f th e latter tw o term s: In general it appears to m e th a t m ost scientists have up to now still m issed th e true sense of the problem o f the origin o f organized bodies. W h e n a portion of them assumes a special vital force, w hich like a m agic power suspends th e operations o f th e laws of nature in anim ated beings, they in ju st th a t way elim inate a priori the possibility of physically explaining organization. O n th e other hand, w hen others explain the origin of all organization o ut of dead chemical forces, they in just th a t way elim inate all freedom of nature in form ation and organization. N ature should neither behave simply lawlessly (as the defenders of the vital force m u st m aintain, if they are consistent), nor simply lawfully (as th e chem ical physiolo­ gists m aintain), b ut it should be lawless in its lawfulness and lawful in its lawless­ ness.nl For th is “u n io n o f freed om and la w fu ln ess” S ch ellin g em p lo y ed th e term Trieb; w e can th u s say th a t “a prim itive Bildun gstrieb acts in organic m atter, by virtue of w hich it takes o n , preserves, and con tin u ally restores a particular fo rm .”158 T h e “first cau se o f organ ization ” m u st lie o u tsid e th e organized m atter itse lf.159 S ch ellin g em p h a sized th a t B ildungstrieb is only an exp ression for th a t u n io n , n o t an ex p lan ation o f it. It is a sy n th etic co n c e p t, co m p o sed o f tw o factors, “a positive (th e prin ciple o f nature, by m ea n s o f w hich th e dead crystallization o f anim al m a tter is con tin u ally d istu rb ed ) and a n egative (th e ch em ic a l forces o f anim al m a tter). O u t o f th e se factors alon e is th e form ative force c o n str u c tib le.” 140 In th e

even t, Schelling e n d e d u p w ith a co n c e p tio n of life seem ingly n o t m u c h different from th e vital force h e ostensibly re je c te d — th a t is, one b ased on th e assu m p tio n of an “ex tern al principle not subject to the chem ical process” th a t acts continually on th e organic m atter, d istu rb in g th e in a n im a te chem ical laws an d rekindling th e vital processes.141 In typical fashion, Schelling a b a n d o n e d th e language o f Bildungstrieb tow ard th e en d of th e book in favor of w hat h e o n ce called “th e c o m m o n soul of n a tu re ” as th e p rin cip le an d cause of life.142 T h a t p rin ciple p erform ed roughly th e sam e two classes of fu n ctio n s— form -giving an d en erg etic— com m only (if usually only im plicitly) assigned to th e vital force by m o st G erm an physiologists of th e 1830s: “It c a n n o t of course b e said th a t th is p rin cip le suspends th e d e ad forces of m a tte r in th e living body, b u t ratheT th a t it I) gives th e se dead forces a direction th a t, left to th em selves, th ey w ould n o t have taken; 2) th a t it repeatedly rekindles and con­ tinually sustains th e conflict o f th ese forces th a t, left to them selves, w ould soon have tran sp o sed them selv es in to e q u ilib riu m an d rest.” 143 S chelling’s First Sketch o f a System o f N a tu ra l Philosophy, p u b lish ed th e next year, was again so m ew h at in c o n siste n t in its h an d lin g of th e vital force. H e first gave it qualified ac c e p tan c e as an im m aterial principle controlling th e chem ical forces of organic m atter: Now the cause that in part suspends and in part alters the chemical forces and laws of m atter in the organism cannot in turn be a material cause, since every material substance [jede Materie] is itself subject to the chemical process— it is thus an imma­ terial principle, which is rightly called vital forced 1 . . . Nature can of course only suspend the chemical and physical laws through the opposing action of another force, and it is precisely this force that we call—because it is as yet still wholly unknown to us— vital force. There already lies in this deduction of the vital force the confession 1) that it has been invented solely as a makeshift of ignorance and is a true product of indolent reason; 2) that by means of this vital force we advance not a step further in either theory or practice.144 If th is recalls th e qualified use of th e vital force by m ain lin e G erm an physiologists d u rin g th e 1830s, all th e m ore d oes S chelling’s an tag o n istic way o f th in k in g recall in p articu lar L iebig’s c o n cep tio n of th e vital force as th e in tern al creative force th a t opposes th e external forces d estru ctiv e of th e organism ’s integrity— in p artic­ ular, oxygen: a) T he principle of life exhibits itself, where it manifests itself, as an activity that opposes every accumulation of m atter from without, every press [Andrang] of exter­ nal force . . . . External nature will thus attack life; most of the external influences that one considers to be conducive to life are actually destructive to life— e.g., the influ­ ence of the air, which is actually a process of consumption, a continuous attem pt to subject living m atter to chemical forces.

β ) B u t it is p recisely th is a tta ck in g by e x tern a l n atu re th a t m a in ta in s life , b e c a u se it c o n tin u a lly r e e x cite s th e organ ic activity, rek in dles th e sla c k e n in g c o n flic t .145

Schelling did n o t rest w ith this qualified understanding of the vital force, b u t sought to go beyond it by incorporating Scottish physician John Brown’s notion of excitability into his dualistic system as th e expression of the alternation betw een receptivity and activity. Such a system would, he said, overcom e the subject-object dichotom y of th e traditional alternatives: T h e [B ru n on ian ] sy ste m . . . tak es th is [p o sitio n ] b e tw e e n tw o o p p o sin g sy stem s, o f w h ic h o n e — th e c h e m ic a l— kn ow s th e organ ism m erely as o b je c t, as p r o d u ct, and allow s e v er y th in g to act u p o n it on ly as o b je c t u p o n o b je c t (i.e ., c h e m ic a lly ), th e o th e r — th a t o f th e vital force— kn ow s it o n ly as su b je ct, as a b s o lu te activity, an d al­ low s e v er y th in g to act u p o n it o n ly as activity. T h e third sy ste m p o sits th e organ ism sim u lta n e o u s ly as su b je ct an d o b je c t, a c tiv ity an d recep tivity, an d p recisely th is m u ­ tu al d e te r m in a tio n o f r ecep tiv ity an d activ ity c o m p r ised w ith in o n e c o n c e p t is n o th ­ in g o th e r th a t w h a t B row n h as c a lle d ex cita b ility .146

T h e beauty of Brown’s system, as Schelling interpreted it, was th a t it was based on a “prim itive duplicity”: For e v en if w e . . . w ish ed to a ssu m e a v it a l force (a lth o u g h n e ith e r p h ysics nor p h ilo s­ op h y sa n c tio n s th e a ss u m p tio n o f a fic tio n ), n o th in g at all is e x p la in e d w ith th is p rin cip le. . . . N o force is lim ite d e x c e p t by an o p p o sin g force. If o n e n o w p o sits th a t th ere e x is ts in n atu re a sp ecial vital force th a t w o u ld b e a sim p le force, th e n in d e e d by m e a n s o f th is fo rce it c o u ld never c o m e to a d e te r m in a te p r o d u ct, an d if, in order to exp lain th e d e te r m in a te n e ss o f n a tu r e ’s p r o d u c tio n , o n e already p o s its so m e th in g ne g a tiv e in th is force, it c e a se s to b e a sim p le fo r c e . 147

If it would appear th a t w hat Schelling ultim ately objected to about the vital force was th a t it did n o t fit his fundam entally dualistic system, one m u st nevertheless no t forget th a t in his World Soul of the previous year he flirted with a m atter-form dichotom y th a t readily accom m odated the vital force. But th e reader who hopes for eith er consistency or logic in Schelling’s writings will be continually disap­ pointed. For th e rest, Schelling’s aim was less to distinguish life sharply from nonlife th an to in terpret them as different m anifestations of a hierarchy of forces: “life is n o th in g b u t an augm ented [gesteigert] state of th e com m on forces of na­ tu re .”148 N ot a transform ation or reduction of forces was intended, b u t a concep­ tualization of th eir ideal relationships. O th er Naturphilosophen th an Schelling provide a m ore straightforw ard illustra­ tion of Schlriter’s characterization of N aturphilosophie’s general rejection of the vital force.149 W alther began the body of his book H um an Physiology w ith a chap­ ter “O n Life” in which life was equated with self-activity and th a t activity identi­ fied as one attrib u te of the “idea of life.”150 In typical naturphilosophisch fashion, “th e whole universe is a living nature, and all activity recognized in it m u st be predicated as an internal and necessary condition of its existence.”151 W alther explicitly rejected the notion of a vital force:

T h e m o st erron eo u s o f all m o d es o f re p rese n ta tio n is, however, certain ly th a t a c ­ cord in g to w hich o n e regards life as a p a rtic u la r c o n d itio n , m o d ificatio n , or q u a lity of ind iv id u al m aterial su b stan ces (of org an ized b o d ies) an d on th a t basis (insofar as th e active g ro u n d o f any q u ality is called force) one falsely im p u te s to it a v ita l force of its ow n, w hich has always rem ain ed an o c c u lt q u ality — in su c h a m a n n e r th a t o n e as­ su m es th a t d e a d m a tte r w ould in d e e d b e c o m e a n im a te d if o n e w ere able to im p a rt vital force to it in an a p p ro p ria te m an n er, a n d th a t living m a tte r b e c o m e s d ead w hen th a t force is destroyed in i t .152

In a sim ilar v ein , C arus u sed his review' o f A u ten rieth to criticize n o t only th e co m m o n u n d erstan d in g of force in general, b u t in particular th e illeg itim a te c o n ­ cep t o f vital force: “N everth eless th e n o tio n o f particular forces a tta ch ed to m a te­ rial ob jects still cau ses th e greatest m isch ie f in every natural scien ce, b u t esp e­ cially in p hysiology th e rep lacem en t o f a h ealthy pure p ercep tio n [Anschauung] o f life its e lf as a p rim itive p h e n o m en o n o f th e world by th e n o tio n o f a particular vital force w hich is su pp osed to p en etrate and rule and th en bring to life (o n e knows n ot how) intrinsically d ead ob jects, has cau sed th e greatest co n fu sio n .”153 In his System o f Physiology C arus again criticized th e view o f life as d ue to th e im p osition of so m e force o n to otherw ise dead m atter, as h e criticized th e co n ce p t of force in general as purely su b jectiv e.154 S u ch a m isu se of th e co n cep t o f force he term ed th e first n egative asp ect (Schattenseite) o f physiology.155 T h e secon d con cern ed th e n o tio n o f a soul: O n e assum ed: I) a n u m b e r of p articu lar m a te ria l su b stan ces or ele m e n ts, each fur­ n ish ed w ith m anifo ld “fo rces” (alth o u g h n o o n e was able to say w h a t a force is in an d o f itself and how it a tta c h e s to m a tte r); 2) a p a rtic u la r force, “th e vital fo rce,” w hich in p art c o n stru c te d from th e se m a te ria l su b stan c es th a t w hich o n e called an organism , in p art, like th e w eight in a clock, served to m a in ta in th is o rg an ism m vital m o tio n (alth o u g h again no o n e was able to say w h at th e vital force is in a n d o f itself a n d how th is force m ig h t also b e able to deal w ith th e m a teria l su b stan c es in acco rd an ce w ith its p urposes); 3) finally, a fte r o n e h a d now im ag in ed to have c o n stru c te d an organism w ith th ese forces a n d m a te ria l su b stan ces, o n e again to o k from som ew here a new force called “so u l” w h ich — w ith o u t o n e know ing a n y th in g else a b o u t it, or b e in g able to in d icate how it ever en ters in to reciprocal in te ra c tio n w ith th e organism — was placed in th e organism a t a ce rta in tim e a n d w hich again a b a n d o n e d it a t a c erta in tim e , w h ereu p o n th e vital force likewise th e n escaped an d th e individual m aterial su b stan ces w ere now again seized b y o th e r vital fo rces.156

A third crim e (Gebrechen) was th e ten aciou sly h eld d istin c tio n “b etw een an or­ gan ic and living and a so-called inorganic and d ead n a tu re.”157 Still an oth er prob­ lem was th at as scien tists saw everyw here the sam e m ech an ical, ch em ica l, and electro m a g n etic processes, and tried to apply th e m to living th in gs, they b egan to regard organism s as m ach in es. T h at was a fun d am en tal m istake, however, sin ce organism s arise via d ifferen tiation or separation w ith in a sin gle h o m o g e n e o u s en ­ tity, w hereas m a ch in es are co m p o sed of m any d ifferen t h eter o g en eo u s parts. For Carus as for S ch ellin g, th e p oin t was n o t to separate physical and ch em ical pro-

cesses from physiological and organic ones, b u t to appreciate “th at here as there, only one life holds sway, although to be sure th e expressions of th e one— of higher organic life— are m uch m ore com plicated, m anifold, and m ore difficult to follow in term s of their m ental construction [schwerer im Geiste durch Construction zu verfolgen] th an those of the other.”158 Schliiter was right: the problem Naturphilosophen had w ith the vital force was th a t th e very need for it presupposes the intrinsic inactivity of inorganic (or “dead”) nature. If on the one hand the discus­ sion of th e vital force in the m ainstream physiological literature of the period broached topics of plausible relevance to Mayer, involving issues of creation and destruction and of the relationship of the generally accepted vital force to the o th er forces and im ponderables of nature, on th e o th er hand the widespread re­ jection of a specific vital force (as of force in general) in works of Naturphilosophie would appear to have offered a significantly poorer context for th e stim ula­ tion of th e kinds of ideas th a t led M ayer in the direction of conservation of energy. 3 R e s p ir a t io n

and

A n im a l H

eat

As shown in ch apter 3 , m ainstream G erm an physiologists of the period discussed respiration n o t only in term s of its connection w ith anim al h eat, b u t also as one of the two chief m eans by which the body excretes excess carbon (along with the production of bile in the liver). M ost did not unequivocally subscribe to La­ voisier’s com bustion theory of anim al heat— the nervous system was typically as­ signed a role here— though th at process was nevertheless well-nigh universally regarded as th e principal source of anim al heat. M ayer was well inform ed about b o th of those respiratory functions; indeed, his understanding of the blood’s ex­ cretory function was w hat prepared him to be surprised at th e color of the venous blood he let off th e Java coast. A lthough there is no evidence regarding M ayer’s views on anim al heat before his voyage to the D utch East Indies, those bloodlet­ ting observations led him very quickly to the acceptance of the com plete suffi­ ciency of the com bustion theory, a crucial step in the progress of his thinking. In o ther words, M ayer’s discovery is unintelligible outside the context of the dom i­ n an t ideas regarding respiration and animal heat. Given the centrality of those topics, one m ight w onder w hether their treatm en t by Naturphilosophen could have provided a similarly rich, if specifically different, context for the understand­ ing of M ayer’s thinking. In term s of th e sources th at I have read, the answer to th at question is a decided “n o.” Indeed, Naturphilosophen had such bizarre and idiosyncratic views on the subject th a t they are difficult to paraphrase in language other than their ow n.159 In the exposition th at follows, we will encounter m any of the leading characteristics of Naturphilosophie: analogies and parallelisms galore (notably betw een microcosm and m acrocosm ), Potenzierung, Figierung, an tith e­ ses, an appeal for Anschauung, and a rejection of b o th artificially contrived exper­ im ents and q u antitative thinking. W h a t we will n o t encounter is m uch th a t en­ lightens us with respect to M ayer’s possible sources.

Schelling said little relevant to these topics in the works of his that I have read. In his Ideas of 1797 he asserted that animal heat flows from an internal source copresent with “the spark of life” itself; in that connection he noted that light and heat work against the laws of gravity that would otherwise rule an inert earth.160 His First Sketch of 1799 related respiration to the now-central activity of irritabil­ ity, but it said nothing about animal h ea t.161 According to Burdach, W ilbrand’s Nature o f the Respiration Process (1827) taught that “there exist no oxygen and carbon at all, for one cannot see them ; on the other hand the light nature [Lichtnatur] of th e elem ents is a fact, since one sees the light in com bustion, and respiration [das A thm en] consists in com m unicating to the organism the light nature inherent in the elem ents and thereby internal anim ation.”162 Pohl’s Views and Results Concerning Magnetism, Electricity, and Chemism (1829) m ade pass­ ing m en tion of respiration, though it is harder to understand his positive views than his rejection of the conventional com bustion theory: Respiration [Respiration] is the im m ediately victorious positive act of vanquishm e n t against the chem ism in the air th a t hostilely opposes th e organism . T he course and th e products of this absolutely antichem ical function m ust therefore no longer be judged in term s of the one-sided viewpoints in accordance with which th e chemical experim ent in and of itself is accustom ed to being conceived, and th e views th a t have becom e current regarding this subject— deriving, in accordance w ith a vague analogy w ith th e process of com bustion, from wholly unsuitable experim ents w ith anim als in enclosed, confined air— belong to th e greatest aberrations in to w hich a science that has deviated from the fundam ental perception of n atural life [Grundanschauung des N aturlebens] has ever been able to fall. D igestion, as the other polar m om ent of th e vital process in th e anim al, is, vis-a-vis th e positive act of respiration, only a negative, defensive side of th e latter.163

For Pohl, respiration is an activity that opposes the fundam entally chem ical action of the hostile atm osphere, and h en ce was n ot itself to be regarded simply as a chem ical process. W alther's Human Physiology provides a superabundance of characteristically naturphilosophisch ways o f thinking. C onsider his discussion o f the heart: T h e h eart, although representing in itself the identity of b o th types of vessels, is nevertheless according to its position venous, situated tow ard th e left side. Positive, expansive m otion has in general the direction from left to right. (The dextrum is therefore everywhere th e good, th e correct, th e true, th e sinistrum is everywhere the evil, th e false, the baleful. T he m otion of th e heavenly bodies is also governed accord­ ingly.) For th a t reason, therefore, th e arterial blood circulation goes from th e left tow ard th e rig h t.164

Perhaps follow ing Schelling’s lead, W alther associated the production of heat with the irritable system . His section on animal heat is a tour de force of the genre: T h e relationship of cohesion to gravity is the sam e as th a t of h ea t to light. For just as gravity is innate in things in twofold fashion— as gravity, and th en again, attaining

a distinctive life in th em through the particularity of things, as cohesion— so, too, does th e principle of light indwell in them in twofold fashion. For th a t reason h e a t is an tith etical to cohesion, it is th a t w hich is anticoh eren t, th a t w hich liquefies and gasifies— the universal m enstruum of th in g s .. . . T h e process of h e a t is therefore also th e inverse process of gravity. Just as gravity is the centripetal tendency of things, so, on th e contrary, does h e a t act in th e centrifugal direction. How can th a t w hich follows such a determ inate, expansive, direction, and w hich is essentially com pletely a n tith e t­ ical, be taken as a m anifestation of th e third, synthetic, dim ension? H eat is n o t the reconciliation of differences, th e leveling o u t of antitheses, b u t it is th a t w hich ignites th e antitheses: and all th e affinities of things am ong them selves, w hich after all d e­ pend on th e antithesis of qualities, appear only at a particular tem p eratu re of heat. H eat has an im m ediate relationship only to light, n o t to gravity. It derives from light and belongs to those attrib u tes of things th a t are an expression of th eir e nsoulm ent by light. T h a t w hich corresponds to gravity in the process of h e a t is cold: for just as there is a process of heating, there is also a process of cooling. Both are th e opposing m an i­ festations of one and th e sam e cause [G rund]. But it is a highly objectionable view to regard cold as merely a w ithdraw al of heat, as a privation of the latter. C old and h eat are n o t merely quan titativ e differences of an arithm etical m ag n itu d e capable of in­ crease and decrease; there is an antithesis of qualities betw een them : cold is a cohe­ sion process, heat an anticohesion process. H eat is th e identity of light and gravity, b u t w ithin the power [Potertz] o f electricity: for th a t reason every process of th e excitation of h e a t is th e excitation of electricity. H eat conduction is an electrical conduction process. T h e sentence: th e organic being generates h e a t in itself, m eans the same as th e sentence: th e organic being bears in itself th e identity of gravity and light, reflected in th e second dim ension. For just as w ithin th e atm osphere of th e earth h e a t only arises th ro u g h th e antithesis betw een sun and earth, in th e same way th e organic being, w hich bears in itself th e center of its position and is sim ultaneously m idpoint and circum ference, has in itself th e source of h eat. T h e capacity to generate heat in itself and to b in d it, to give itself its tem per­ ature through its own action, is the sign of th e cosm ic perfection of th e organic being. But th e irritable system is preem inently th a t of th e generation of heat: for h eat is the identity of light and gravity w ithin the second power.165

It is hard to know how to evaluate a theory of animal heat that rests ultim ately on an obscure cosm ic analogy, on “the identity of gravity and light, reflected in the second d im en sion .” O n the other hand, although W alther’s style of philosophiz­ ing was for th e m ost part quite at odds with M ayer’s, there are a few m otifs rem iniscent o f som e o f the peculiarites of M ayer’s earliest ruminations: a con n ec­ tion b etw een light, heat, and gravity; centripetal/gravitational versus centrifugal/ thermal tendencies; th e neutralizing of differences; and the self-creation of heat by a cosm ic organism. T h e significance of such connections will be explored in depth in section 4 of this chapter. For the present, I n ote simply that there is no

evidence— and it seems to m e little likelihood— th a t W alther’s book of 18071808 was one of M ayer’s sources. O ken’s brief consideration of anim al h eat in his Textbook o f Nature Philosophy is as inscrutable as any extract from a work of true Naturphilosophie: 2575. T he chief function of cell form ation is the heat process. Cell process and heat process are one. H eat is the product of the condensation and rarefaction process. 2576. T he tem perature process is individualized in the skin. 2577 AU tem perature depends on th e evaporation process. It is som etim es nerves, som etim es vessels, som etim es external influences th a t alter th a t process. Animal heat is produced like cosmic heat, through th e alternation of fixation [Wechsel der Figierung]. But this alternation occurs principally in nutrition and tran ­ spiration.166

N aum ann, in a work of 1835, concluded th at the production of animal heat is principally “th e result of the passage of the liquefied nerve-m edulla [fluidisirtes Nervenmark] into the blood of the capillary vessels,” a conclusion anticipated by the title of th e book: The Problems o f Physiology, or the A ntithesis between NerveMedulla and Blood.167 N aum ann allowed th a t it was probable th a t the influence of air on th e blood in the lungs m ight further increase the anim al’s tem perature, b u t he denied th at this could be the principal source of anim al h e a t.168 C arus considered five possible causes of the production of heat in higher ani­ mals, two of which were relevant to physiology: “4) repetition of manifold telluric (or, if one wishes to follow custom ary linguistic usage, m echanical-physical-chem ­ ical) processes in the organism itself th a t are capable of developing heat; 5) repe­ tition of an internal solar-planetary tensional relationship in the organism itself th at, like the action of the sun on the earth, brings about the liberation of h e a t.”169 T he processes included under (4) were in turn fourfold: “a) densification by m eans of pressure and b) the friction related to it, i.e., a variable pressure, c) m etam orphosis of the phenom enal form of the substance in the sense of increas­ ing densification, and d) the com bination of diverse substances whereby new products are formed, and the electrical processes th at accom pany these [last] two processes.”170 Of these the m ost im portant physiologically were (c) and (d). Ac­ cordingly, C arus addressed the pros and cons of the (there unnam ed) oxygen theory of anim al heat, m entioning the well-known experim ents of “D epretz.” But C am s ultim ately rejected the attem p t to quantify the production of animal heat and to assign a percentage to any given chemical process. More “indicative of the dignity of th e hum an organism ” th an the mere production of a certain degree of h eat is, he m aintained, the body’s m aintenance of the sam e tem perature under widely varying circum stances.171 T h a t ability indicates the influence of another heat-producing relationship— the fifth possibility on his earlier list— namely, the opposition between the nervous system and the other tissues of the body: “Now as such an (as it were) regulative relationship . . . one can only recognize the inter­ nal mutually opposing action o f planetary and solar structures, upon which de­ pends in general th e more strongly pronounced individuality of the hum an being,

one th a t rises [sich steigt] as far as th e concept of the person. It is th e relationship betw een th e nervous system , which represents th e unity of the idea of th e organ­ ism, and th e o th er structures th a t it pervades.”172 A nim al h eat is thus not the result of a conventional chem ical reaction, b u t th e result of an antithesis th at is itself th e expression of a cosm ic analogy. Such reasoning is, of course, pure Naturphilosophie, and dem onstrates once again how far th a t m ovem ent was from th e m ainstream of G erm an science by the 1830s. I see nothing here particularly conducive to conservation-of-energy-type reflections, and no -explanatory gain from assum ing th a t M ayer m ight have read Carus. Burdach, in a book M ayer owned, offered his own variant of the explanation of anim al h eat in term s of som e kind of polar opposition betw een nerves and (in this case) th e vascular system: “As with an electrical antithesis, heat is generated th rough th e interaction of the nerves with the vascular system on which they are distributed; it is developed in th e blood, as its carrier and conductor, . . . every­ where th a t nerves and blood vessels are present, and it is the greater th e m ore energetically (on th e one hand) th e nerve acts, the m ore com plete (on th e other hand) th e blood and th e m ore rapid its circulation.”173 He said nothing about oxidation in this connection. Against a purely m echanical explanation of the cir­ culation of th e blood, Burdach tau g h t th a t th e organs of the body attra ct the bright red (and oxygen-rich) arterial blood, just as the air in th e lungs attracts the dark red (and carbon-rich) venous blood.174 As one would expect, he was ready w ith a raft of analogies to render th e phenom ena intelligible: This action is not mechanical, but can only be compared to phenomena where bodies attract a fluid chemically related to them in order to enter into combination with it; or where, by virtue of the constitution of the substance, no change in composition comes about, but only adhesion—where, for example, a body attracts water out of the air, a narrow tube raises water, bodies floating on water are attracted or repelled by the rim of the vessel according as their substance and that of the vessel are different, etc.; or where, without regard to the substance, particular force relationships are at work, north- and south-polar magnetic bodies or positive and negative electric bodies at­ tract each other, while the like-named repel each other. We recognize as a rule that two bodies which agree with each other in general, but which are opposed to each other in particular, attract each other, that therefore related but dissimilar bodies, or those in dissimilar states, strive toward unity and to level out their differences [sich auszugleichen], and we may be permitted to presuppose a like relationship between the blood and the organs.17’ In th e sixth volum e of his well-known Physiology as an Experiential Science (1840), Burdach considered the problem of anim al h eat at greater length. He introduced th e topic w ith words redolent of th e conceptual apparatus of Naturphilosophie: Heat is accordingly generated wherever life stirs. But as we cannot, like the ancients, regard the capacity to generate it as identical with the vital principle, just as little could it suffice when one simply declared in general that it is generated by the vital

force. For although its essence lies in the con cep t of life, it can nevertheless only be produced by life through th e m ed iation of the universal forces o f th e world. A) Heat in general m anifests itself as th e expansive force that em erges free from th e conflict w ith contractive force. In particular, it is produced by all kinds of con d ition s that presuppose contraction: a) m echanically, by m eans of pressure, Hiction, im pact, and hitting; b) chemically, w ith th e interaction of dissim ilar related substances, whereby there takes place a leveling out of their difference, an exhaustion o f their chem ical force, and a densification o f substance; c) dynamically, by m eans o f the retarding effect of the earth on sunlight, and by m eans o f the con flict o f positive and negative electricities w hose indifferentiation has b een m ade more difficult.176

Burdach reviewed th e experim ents and conclusions of Lavoisier and Laplace; con­ sidered and rejected explanations based on friction, com pression, or changes in specific heat; and weighed argum ents in favor of the nervous system. He was of two m inds as to w hether or not respiration and the production of heat are directly proportional, though the com parative evidence from other anim al species dis­ posed him to deny such a connection. He concluded negatively th a t “respiration [das A thm en ] does not produce heat directly, though to be sure it belongs to the conditions of its p roduction.”177 He appealed to Johannes M uller in support of his positive conclusion th at the source of anim al heat lies principally in “th e interac­ tion of the nerves with the rem aining tissues” of the body.178 Burdach believed, moreover, in th e qualitative difference betw een inorganic and organic electricity and heat: “Solar heat, the heat of a stove, and anim al heat make an entirely differ­ e n t im pression at the same degree [of heat]; Rumford found th a t his hand had a stronger effect on the therm om eter than an inorganic or dead organic body of the sam e tem perature; with som eone suffering from putrid fever we feel a distinctive, disagreeable, b iting h eat th at th e therm om eter does no t indicate.”179 Such a view is n o t apt to dispose a person to accept a purely chem ical explanation of animal heat, nor to look for a universal m easure of the quantity of heat. If th e sources th at I have looked at are representative, it would n o t appear likely th at M ayer’s understanding of physiological processes owed anything to Naturphilosophie. Its peculiar m odes of thinking were in th e m ain entirely foreign to the considerations th at characterized M ayer’s. Nevertheless, if the m ajor them es, as­ sum ptions, and conclusions of Naturphilosophie do no t appear to have been likely contributors to M ayer’s theory of force, there are still a num ber of its recurring m otifs th a t do have rough counterparts in M ayer’s work. It is to those we now turn.

4 E choes o f N

a t u r p h il o s o p h ie

in M a y e r ' s W o r k ?

From th e m aterial presented in the foregoing sections and chapters, I conclude th at th e traditional link betw een M ayer and Naturphilosophie, th e doctrine of the unity of forces, cannot support such a connection: not only was the unity of forces n o t one of M ayer’s guiding m otifs, b u t it was n o t all th at prom inent am ong

Naturphilosophen, either. N e ith e r d id th e la tte r speak of forces as causes, or c o n ­ sider th e possibility o f th e ir q u a n tita tiv e m e a su re m e n t. O nly M ay e r’s (for him ) ra th e r e x cep tio n al u se of th e te rm Urkraft— tw ice in th e e n tire b o d y of his surviv­ ing p u b lish e d a n d u n p u b lish e d w ritings— rem ains to suggest a possible link b e ­ tw een his d o c trin e of force a n d th a t of Naturphilosophie. It does n o t a p p e a r even rem o tely likely th a t M a y e r’s th in k in g ow ed a n y th in g to its p ecu liar physiological teach in g s. Nor, w ith th e im p o rta n t ex c e p tio n of in difference, do th e m o st p ro m i­ n e n t tra its of Naturphilosophie find significant c o u n te rp a rts in M ay e r’s w ritings. M ayer n e v e r even m a d e p articu lar u se of th e w ords “d y n a m ism ” an d “d y n am ic ,” d e sp ite th e fact th a t his was a th e o ry of force. T h e re rem ain , however, certain p ecu liarities in M ay er’s first (u n p u b lish e d ) essay a n d his co rresp o n d en ce from th a t early p erio d th a t do have c o u n te rp a rts in th e Naturphilosophie lite ra tu re — m o st n o tab ly in S ch ellin g ’s World Soul, First Sketch, a n d Introduction— th a t re­ q u ire us to leave o p e n th e q u e stio n of in flu en ce: in particular, ideas su ch as crea­ tio n o u t of n o th in g a n d th e relatio n sh ip b e tw e e n lig h t an d gravity in plan etary system s, ideas th a t were th em selv es c o n n e c te d w ith th e cen tral c o n c e p t of indif­ ference. T h e first p arag rap h of M ay er’s earliest surviving essay, “O n th e Q u a n tita tiv e an d Q u a lita tiv e D e te rm in a tio n of F orces,” c o n ta in e d th e striking a n d (for h im ) u n u su a l se n te n c e , “W e can derive all p h e n o m e n a from a p rim itiv e force th a t te n d s to a n n ih ila te th e ex istin g differences, to u n ite ev ery th in g th a t exists in to a h o m o g e n e o u s m ass in a m a th e m a tic a l p o in t.”180 As n o te d in c h a p te r 2, M a y er’s d e v e lo p m e n t of th e se ideas suggests th a t th a t Urkraft m ig h t b e th e force o f grav­ ity, w h ich te n d s to e lim in a te th e spatial se p aratio n , or “d iffe re n ce,” b e tw e e n b o d ­ ies. E ven allow ing for th e fact th a t Urkraft m ig h t conceivably be here ju st a n o th e r G e rm a n w ord, fo rm e d acco rd in g to q u ite regular p rinciples— an d th u s n o t b e tra y ­ ing any p a rtic u la r p h ilo so p h ical p ro v en en ce— an d d e sp ite th e fact th a t N a tu rp h i­ losophen te n d e d to speak in te rm s of opposing forces (Ur- or otherw ise, b u t in plu ral), th e se n te n c e still h as a strongly naturphilosophisch flavor. As far as I can tell, th e only o th e r use of th e word Urkraft in M ay er’s w ritings o ccurred in a le tte r to B aur fro m A u g u st 1844 in w hich h e in d ic a te d h e w a n te d th e follow ing passage ad d e d to th e m ech an ical p art of th e long m a n u sc rip t h e h a d se n t Baur n in e days earlier: If one has once begun to ascribe the properties of things to particular forces, then logically one should also derive the property to exist from a distinctive force, a force not unjustly called the primitive force. O ut of this “force of being” [“Seikraft”] there would em anate the composing principles of matter, the forces of repulsion and attrac­ tion, like the spectrum out of the sun’s ray. T he prism that accomplishes such a wonderful feat is the wisdom, rising above normal hum an understanding, of the philo­ sophical investigator.181 T h is passage c o n ta in s o n e of M a y e r’s very few references to th e dynam ical cen trif­ ugal a n d c e n trip e ta l forces from w h ich Schelling an d th e rest h a d c o n stru c te d m atter. H is so m ew h at obscure analogy w ith th e s u n ’s sp e c tru m also h e ig h ten s th e naturphilosophisch to n e of th e passage.

T h is is su g g e stiv e e v id e n c e , b u t it d o e s n o t ta k e o n e very far. T h e th e m e s b ro a c h e d d o n o t play a m a jo r ro le in M a y e r’s w ork, a n d th e se n se o f th e p assag e a p p e a rs to b e d ism issiv e: M a y e r d id n o t w ish “to ascrib e th e p ro p e rtie s o f th in g s to p a rtic u la r fo rc e s”— h e re p e a te d ly in s is te d t h a t fo rc es are n o t m e re p ro p e rtie s of m a tte r — a n d th e alleg e d e x c e p tio n a l “w is d o m ” o f th e “p h ilo s o p h ic a l in v e s tig a to r” w as surely in te n d e d ironically. M o re im p re ssiv e are c e r ta in sim ila ritie s b e tw e e n M a y e r’s early a tte m p ts to g e n e r a te th e s u n ’s lig h t s o m e h o w o u t o f its g ra v ita tio n a l in te r a c tio n w ith th e e a r th , a n d s o m e o f S c h e llin g ’s a n d o th e r s ’ id eas c o n c e rn in g p la n e ta ry m o tio n s a n d th e n a tu r e o f th e u n iv e rse . H e re a g a in , only fairly e x te n siv e q u o ta tio n fro m th e p rim a ry so u rc e s ca n co n v e y th e q u a lity of th e re so n a n c e s b e ­ tw e e n th e ir c o n c e p tio n s a n d M a y e r’s. S c h e llin g ’s e a rlie s t p e r tin e n t d isc u ssio n s o c c u rre d in th e W orld S o u l o f 1798, in th e first h a lf of th e b o o k e n title d “ O n th e F irs t F orce o f N a tu r e .” H is o p e n in g p a ra g ra p h w o u ld s e e m to b e a clea r a llu sio n to th e g e n e r a tio n o f cyclically re c u r­ rin g p la n e ta ry m o tio n o u t o f tw o o p p o s in g forces, o n e a c tin g c e n trip e ta lly , th e o th e r ta n g e n tia lly : Every m otion th a t returns back into itself presupposes, as condition for its possibil­ ity, a positive force th a t (as impulse) initiates th e m otion (as it were, produces the initial tendency toward the line) and a negative force th a t (as attraction) directs the m otion back into its e lf (or prevents it from striking o u t in a straight line). In nature everything strives continuously forwards; we m ust seek the reason th at this is so in a principle th at, being an inexhaustible source o f positive force, continually initiates th e m otion anew and uninterruptedly sustains it. T his positive principle is the first force o f nature.182 N a tu r e th u s p o ssesses w ith in its e lf a n in e x h a u s tib le so u rc e o f m o tio n , c o n n e c te d so m e h o w w ith p e rio d ic c e n tra l-fo rc e sy stem s. S c h e llin g la te r in v o k e d an ex p lic it an a lo g y b e tw e e n u n iv e rsa l g ra v ita tio n a n d th e o p p o s in g fo rc es o f th e so -ca lle d c h e m ic a l p ro cess, b o th o f w h ic h reveal th e g e n e ra l te n d e n c y in n a tu r e to w a rd e q u ilib riu m : Since there is a universal striving [Bestreben] toward equilibrium in nature, every excited principle arouses necessarily and in accordance with a universal law the oppos­ ing principle with which it stands in equilibrium . O ne n o t unjustly regards this law as a m odification of the universal law of gravitation; it is, along with th e law of universal gravity, at least dependent upon a common higher law. O ne m u st assum e th a t in every chem ical process there predom inates such a dual­ ism of opposing, m utually excited forces. For in every chem ical process there arise qualities w hich were n o t there previously, and w hich owe th eir origin merely to the striving of opposing forces to com e into equilibrium w ith each other. It has long since been th e am bition of philosophers and physicists to investigate th e connection in w hich th e chem ical attraction of bodies stands to th e universal attraction. O ne m ust affirm th a t b o th attractions stand under th e sam e original law, namely th a t m atter in general reveals its existence in space by m eans of a continual striving toward equilib­ rium , w ithout w hich all m aterial substances would be exposed to dissipation into infinity.183

Schelling fu rth er connected gravitational system s and th e opposing forces m ak­ ing u p m atter w ith th e production of light, regarded as stream ing ou t from the cen ter toward th e periphery. T h e details are hazy, b u t th e general tendency of his thinking recalls som e of M ayer’s early planetary speculations: T h e positive cause o f all m o tion is the force th at fills space. If m o tio n is to be sustained , th en this force m u st be excited. T h e p h en o m en o n o f every force is there­ fore a m aterial substance [eine M a te rie]. T h e first p h en o m en o n o f th e universal force of nature by m eans of w hich m o tion is kindled and sustained is light. T h a t w hich stream s toward us from the sun (since it m aintains th e m otion ) appears to us as the p o sitive [factor], that w hich our earth (as merely reacting) opposes to that force ap ­ pears to us as negative. T h e m atter th at in every system stream s from the center toward th e periphery— i.e., ligh t— is m o v e d w ith such force and speed that so m e have even d ou b ted its m ateriality becau se it lacks the universal characteristic o f m atter, inertia. T h at therefore light disperses itself m all directions in rays m u st b e exp lain ed from th e fact that it finds itself to be in continuous developm en t and in th e original disper­ sion. T h at even ligh t attains relative rest can already be con clu d ed from th e fact that th e light of an infin ite num ber of stars d oes n ot propagate its m o tio n as far as u s. 184

Yet despite th e sim ilarities betw een these passages from Schelling and som e of M ayer’s early speculations, in th e same book Schelling in fact explicitly consid­ ered th e production of light in th e sun as due to a decom position of its atm os­ ph ere.185 And th e Abhandlung added to th e second and third editions, whose title m ig h t seem to an n ounce another source of cognate ideas— “O n th e R elationship betw een th e Real and th e Ideal in N ature, or D evelopm ent of th e first Principles [G rundsdtze] of th e Philosophy of N ature from th e Principles [Pnncipien] of Gravity and L ight”— was for th e m ost part a striking exam ple of th e kind of gib­ berish Naturphilosophie is fam ous for, and it provides no prom ising connec­ tio n s.185 Schelling’s two m ajor works of Naturphilosophie of 1799 elaborated on the above th em es and connected them w ith th e central concept of indifference, in particular creation via the annihilation of difference. In analyzing the n atu re of gravity (Schwere), Schelling n o ted th at a body alone in em pty space is n o t heavy (schwer), b u t becom es so only in th e presence of another body outside itself: every body has th e degree of its w eight (Schwere) in itself, b u t th e cause of its w eight outside itself. T here thus m u st b e “an original difference.”187 (Recall M ayer’s in­ terp retatio n of gravitation in term s of th e spatial difference betw een two bodies.) In im agining th e original developm ent of th e universe in term s of an alternation betw een expansion and contraction, Schelling added th a t this alternation was n atu re’s a tte m p t to return to a state of indifference from the difference th a t is contrary to its original unity.188 T hough h e did no t there connect these ideas with gravitation, th e general context was clear. T h e explicit connection w ith gravita­ tion cam e in his second work of th a t year, in discussing th e production of a se-

quence of antitheses out of the original productive identity o f nature, antitheses that are in turn partially neutralized around particular points of indifference. Som e of his language recalls that of the first paragraph of Mayer’s first (unpub­ lished) essay of 1841: T he organization so determ ined is none other than th e organization of th e universe in the gravitational system.— T h e force o f gravity is simple, b u t its condition is d u ­ plicity.— Indifference proceeds only out of difference.— T h e neutralized duality is m atter, insofar as it is only mass. T he absolute point of indifference exists nowhere, b u t is (as it were) distributed am ong several individual points.— T h e universe, w hich forms itself from the center tow ard the periphery, seeks th e point where even the m ost extrem e antitheses of nature neutralize each other; th e im possibility of this neutralizing [Aufheben] assures th e endlessness of the universe. O f every product A the unneutralized antithesis is transferred to a new p roduct B; th e former thereby becom es the cause of th e duality and the gravitation for B. . . . T hus for exam ple the sun, because it is only relative indifference, sustains, as far as its sphere of action reaches, th e antithesis th a t is the condition of gravity on th e subordi­ nate heavenly bodies. T h e indifference is in every m o m en t neutralized, and in every m o m e n t rees­ tablished. . . . T h e universal reestablishm ent of duality and th e renewed n eutraliza­ tion in every m om ent can only appear as a striving [nisus] toward a third th in g [ein Drittes]; this third thing is abstracted from th e tendency, [is] nothing, therefore merely ideal (only designating th e direction)— a po in t.1 1 It is precisely nought [die N u ll] into w hich natu re strives continuously to return, and into which it would return if th e antithesis were ever neutralized. L et us imagine th e original state of nature as = O (lack of reality). Now th e n o u g h t can of course be im agined as separating itself into 1 - 1 (for this = O).189

Schelling argued that the production o f light in the sun m ust be necessarily conn ected with its position at the center of the solar system , though again his solution to that problem did not here (in the First Sketch) involve gravitation.190 That connection cam e later, in a passage rem iniscent of Mayer’s probing for con ­ nections: T h a t th e greatest and forem ost portion of the heavenly bodies is in ten d ed for light processes does n o t indicate som eth in g accidental, b u t rather a universal, higher, and farther-reaching law o f nature. T he action of light m u st stand in secret connection w ith th e action of gravity exerted by the central bodies.2 T h e former will give the things of th e world th e dynam ic, as th e la tte r the static tendency. 2 T h a t is, through th e action of gravity the indifference is continually neutralized— th e condition of gravity reestablished. But we perceive in light n o th in g b u t this rees­ tablishm ent of th e antithesis, therefore it is already clear here in w hat connection the chem ical action may well stand w ith th e action of gravity.191

He expanded upon th ese conn ection s— now also including chem ical reactions— later that year in the Intro d u ctio n in words likewise suggestive of the conceptions Mayer brought together. At issue was the dynam ical process by which antitheses give rise to each other via the alternation of difference and indifference, o f which process Schelling offered th e follow ing further illustration: [T]hus w hen the bond of gravity is dissolved in th e chem ical process, th e p h en o m e­ n o n of light, w hich accom panies th e chem ical process in its greatest perfection (as the process of com bustion), is a strange p h enom enon th a t, w hen fu rth er pursued, con­ firms w hat is said on page 146 of th e Sketch: “T h e action of light m u st stand in secret connection w ith th e action of gravity exerted by the central bodies.” For is n o t th a t indifference of gravity dissolved a t every m om en t, since indeed gravity, as always active, presupposes a continuous neutralizing of indifference?— T hus does th e sun bring ab o u t a universal dissociation of m a tte r into th e original antithesis (and thereby gravity) by m eans of th e separation [Vertheilung] exerted on th e earth. T h a t universal neutralizing o f indifference is w hat appears to us (anim ate beings) as light; where, therefore, th a t indifference is dissolved (in th e chem ical process), th ere light m ust appear to us.— According to th e foregoing, it is one antithesis th a t, from m agnetism on through electricity, finally loses itself in th e chem ical p h en o m en a .1 1 . . . W h a t happens th e n in the chem ical process? Two en tire products gravitate toward each other. T h e indifference of each one by its e lf as absolute is neutralized. T his absolute neutralizing of indifference puts th e entire body in to a state of light, just as th e partial neutralizing in th e electrical process puts it in to a partial sta te of light. T hus th e light th a t appears to stream to us from the sun will also in all probabil­ ity be n o th in g b u t a phenom enon of th e indifference neutralized a t every m om ent. For since gravity never ceases to act, its condition— th e antithesis— m u st also b e regarded as arising again at every m om ent. W e w ould th u s have in th e case of light a continuous visible p h enom enon of the force of gravity, and it would be explained why precisely those bodies of th e world system th a t are th e principal seat of gravity are also th e principal source of light, explained, then, in w hat connection th e action of light stands w ith th a t of gravity.192

If there is, to be sure, n o Mayer-like application of the parallelogram of forces to central-force m otion s in Schelling’s works— the confusions surrounding which seem to have led Mayer to first entertain the possibility of the creation of force out o f nothing— and even if Mayer never spoke o f Schelling-Iike antitheses (m uch less of their successive production), nevertheless the nexus of issues and m uch o f the language is q uite similar to that o f M ayer’s earliest work. O ne of the criticism s Schelling leveled against m echanical and atom istic sys­ tem s of natural philosophy (such as that of the G enevan natural philosopher, G eorges-Louis LeSage) was that they cannot explain the first origin o f m otion in the universe, only its continuance. A ccording to his dynam ical philosophy, how ­ ever, m otion originally arose o u t o f a state of rest. Although he did not relate this creation of m otion to central-force system s, nor speak in this context in terms of

equal and oppositely directed m otions arising out of zero a la Mayer, m uch of his language is otherwise strongly rem iniscent of M ayer’s: Since heterogeneity is th e source of activity and m otion, so would th e cause of universal m agnetism also be the ultim ate cause of all activity in nature, thus the original m agnetism would be for nature in general w hat sensibility is for organic n a­ ture— a dynamic source of activity; for in the realm of m echanism one sees m otion arise out of m otion. But w hat is th en th e first source of all m otion? It cannot again be m otion. It m u st be the opposite of m otion. M otion m u st originate from rest. As in the chem ical process, where th e m oved body does n o t move th e resting or m oved one, b u t th e resting body moves the resting one. Likewise in the organism, where no m otion im m ediately again produces m otion, b u t where every m otion is m ediated by rest (by sensibility). For since th e first problem of this science, to investigate th e absolute cause of m otion (w ithout w hich nature is nothing in itself whole and bo u n d ed ), is simply n o t to be solved mechanically—because mechanically m otion only arises o ut of m otion ad in ­ finitum — there thus remains open only one route for the actual construction of a speculative physics, th e dynam ical, with th e presupposition th a t m otion arises not only o u t of m otion, b u t even out of rest as well, th a t there is therefore also m otion in n atu re’s rest, and th a t all m echanical m otion is merely th e secondary and derivative of th e sole prim itive and original, w hich originates already from th e first factors of the construction of any kind of nature (from the fundam ental forces).193

O nce again we find certain similarities with Mayer— such as the creation of m o­ tion out of rest— in close connection w ith other them es quite absent from his work, such as the (in part im plied) tripartite sequence of m agnetism , electricity, and the chem ical process, plus the further analogies w ith sensibility and so forth. Nor was Schelling the only Naturphilosoph to deal with these issues. Consider the connection b etw een light, gravity, and heat as expounded in E schenm ayer’s Outline o f Nature Philosophy: Light stands in proportion w ith th e greatest degree of velocity and force, gravity w ith th e greatest degree of inertia and w eight [Last], b u t heat w ith m otion of an interm ediate degree. . . . Gravity seeks to reduce everything to a point— i.e., th e cen ter of gravity— and thereby to im pede all m otion. For th a t reason it is the negative force of n ature, or rather it belongs to th e negative order, where inertia has its dom ain. Light seeks to neutralize all centers of gravity and to p o ten tiate every m otion. For th a t reason it is th e positive force of nature, or rather it belongs to th e positive order, where velocity has its domain. H eat is the indifference of nature and m ediates gravity and light, it stands as unity, as it were as th e zeroth power betw een the negative and positive exponents of gravity and light. Light is the integrating, gravity the differentiating, and heat the indifferentiating principle of nature.

T here are only three powers: light, heat, and gravity, ou t o f w hose reciprocal inter­ action , integration, ind ifferen tiation , and differentiation all m aterial substances re­ ceive their q uantitative and qualitative relationships.194

If som e of th e specifics are different from the ideas M ayer toyed with, neverthe­ less there are suggestive generic similarities. Before assessing the evidence for M ayer’s having read and been influenced by one or m ore works of Naturphilosophie, let us look at one m ore work, N aum ann s Pathogeny, published during the second half of 1840 while M ayer was on board th e Java. N a u m an n ’s work illustrates b o th som e of the affinities betw een aspects of M ayer’s work and aspects of N aturphilosophie as well as some of th e fu n d am en ­ tal differences betw een them . As was n o t unusual in m edical and physiological works of th e day, th e au th o r developed a t som e length th e ontological an d epistem ological views th a t underlay his thinking. O u r knowledge of m atter is thus only in term s of certain basic antitheses, and the “highest law of n a tu re ” is a vaguely en u n ciated “law o f antithesis or p o l a r i t y these antitheses and “the original polar­ ity” have th eir basis “in th e original difference [D ifferenz] of m atter.”19’ T here was th e standard naturphilosophisch talk of the “neutralization of all a n tith e ­ ses.”196 N au m an n distinguished— idiosyncratically— two fundam ental polarities, a Direktionspolaritat, which referred som ehow to the relationship betw een the density an d extension of m a tte r and corresponded roughly to “m echanism ,” and an A ffinitdtspolaritdt, which referred som ehow to the particular properties of m atter and corresponded roughly to “chem ism .”197 T ransitions betw een these tw o m anifestations of polarity, accom panied by changes in th e form and com posi­ tion of m atter, produce the phenom ena of electricity, m agnetism , etc. It was in discussing these two Fundamentalpolaritaten th a t N aum ann treated th e relation­ ship betw en th e sun an d th e earth in a way th a t recalls at least one of th e m otifs of M ayer’s u n d erstanding of it: T h at they [i.e., th e tw o fu n d am en tal polarities] can b e derived from on e and the sam e cause— nam ely from th e original difference o f m atter (§ 11)— can easily be proven from th e relationship o f the earth to th e sun. T h a t relationship clearly corre­ sponds to th e directional polarity insofar as it design ates th e activity o f a force by m eans of w hich th e d istan ce of th e planet from th e central body and its m o tio n and orbit are determ ined. But at the sam e tim e this relationship m an ifests itself as affinitative polarity in that it affords th e op portunity for m anifold changes in th e m atter o f th e terrestrial body. T h e polarity b etw een su n and earth is, however, in essen ce o f a dynam ical nature; for it is co n tin u ou sly excited and just as co n tin u ou sly again a n n ih i­ lated [aufgehohen], so th at th e earth retains its relative autonom y, w hile nevertheless th e antithesis b etw een th e mass and th e elem en ts [Stoffe] is con tin u ally called forth anew in its m atter by m eans of th e pow erful external im pulse. But th e polar relation­ sh ip o f th e earth to th e sun is only d eterm in ed by th e higher a n tith esis as w hose result on e m u st regard th e gradually occurring change in loca tio n w ith in th e universe o f the sun w ith its w hole planetary system , and w hich itself presupposes th e con tin u ou s activity of a m aterial force that, even if otherw ise unknown, is n evertheless directed toward th e su n .198

T h u s am idst all th e decidedly un-Mayer-like language we find N aum ann talking ab out th e continuous interruption and reestablishm ent of the polarity betw een th e earth and the sun. Tliis is still not really M ayer’s language— polarities and antitheses were not two of his usual concepts— b u t the passage nevertheless shows th a t th e general issue of relating sun-centered planetary m otion to some kind of dynamical process of creation and annihilation was a com m on topos of N aturphilosophie. In term s of understanding M ayer’s possible sources, however, it does n o t get us m uch to assum e he read N aum ann, nor does it seem very likely th a t he would have done so during the undoubtedly hectic four m onths betw een his return to H eilbronn in February 1841 and th e com pletion of his first essay in Ju n e.199 Eschenm ayer’s O utline o f Nature Philosophy was published in T iibingen in 1832, the year Mayer entered the University of T iibingen to study m edicine. T hus tim ing and location make this a reasonable candidate for a work of Naturphilosophie M ayer m ight well have known. U nfortunately— as the case may be— it does n o t provide eith er very m any or very strong leads for understanding th e peculiari­ ties of M ayer’s work. Like N aum ann’s Pathogeny, Eschenm ayer’s book has served here mainly to illustrate the characteristically naturphilosophisch aspects of a pe­ culiar way of relating light and gravity and to highlight the problem of identifying M ayer’s potential sources. As far as th e works considered here go, th at leaves Schelling, in particular his two works of Naturphilosophie from 1799. In this case the them atic sim ilarities are indeed very strong: a connection betw een light and gravitation via the annihila­ tion of differences; the all-im portant concept of indifference; and the creation of opposites out of some kind of zero or rest state. These points of contact rem ain striking even considering the more num erous ways in which Schelling’s and M ayer’s work and tho u g h t were vastly dissimilar. But did Mayer actually read Schelling? N ot only is there no direct evidence th at he did— and Shelling’s nam e never once appears in the entire corpus of M ayer’s surviving writings— b u t other evidence, already cited, argues th a t he had little exposure to or appreciation of philosophical works in general. T h at Schelling’s especially relevant works of 1799 were not reprinted until 1858 further lessens the likelihood th a t they would have com e to M ayer’s attention. In assessing M ayer’s receptivity to naturphilosophisch ideas one may cite, too, his response to an essay en titled “Toward a C riticism of C ontem porary Science” published in the Deutsche Jahrbiicher fiir W issenschaft und K unst by an otherwise unidentified “Dr. N. Lowenth al” in O ctober 1842— too late to have influenced him , b u t one of th e only naturphilosophisch works M ayer specifically com m ented upon in his sur­ viving writings. Lowenthal paid particular attention to the issue of the proper m eaning and com m on m isuse of th e term s Schwere and Schwerkraft, the issue th a t caused Griesinger to call th e article to M ayer’s atten tio n in D ecem ber 1842.200 Lowenthal wrote: T h e individual heavenly body’s sim ultaneous d ep en d en ce on and relative ind ep en ­ den ce of the law o f th e unity of the entire material world reveals itself nam ely in a three-part process w hose first m om en t is that the particular heavenly body posits itself

[setzt sic/i] as autonom ous and closed w ithin itself. . . . T h e second m o m en t is th a t th e heavenly body th a t posits itself m its individual auto n o m y by m eans of th e axial rotation proceeds to negate the codeterm ining influence of th e universal center. It strives to tear itself loose— in th e direction of the tan g en t perpendicular to the line co nnecting its center w ith the cen ter of th e world— from th e co n n ectio n w ith th e universal ground o u t of w hich its particular existence has been form ed. But because th e universe never ceases to be th e bearer of all particular configurations, this negating tendency of th e individual is opposed by the universal principle of gravitation, w hich strives by m eans of a central force to m ain tain th e individual heavenly body in its dep endence on th e universal center. T h u s there finally results (thirdly) from th e an ­ tithesis and th e struggle of forces acting at th e sam e tim e in tangential and centripetal directions on th e individual heavenly body th e revolution of th e p lanet around th e sun sim ultaneously with th e rotatio n about its own axis.201

N ot th a t L ow enthal’s essay contained as suggestively sim ilar language as Schelling’s or even E schenm ayer’s, b u t its overall tone was com parable and it to u ch ed upon certain conceptions, such as th e com bination of tangential and centripetal forces in th e production of planetary m otions, to which M ayer m ight have been responsive. In M ayer’s reply to Griesinger, h e said he had read Lowenth al's article b u t not paid m uch atten tio n to it “because he begins m ore with philosophical reflections unintelligible to a layperson in this school than he pro­ vides a clear scientific viewpoint [Anschauung] ”202 As far as it goes, this suggests th a t M ayer had n o t had m uch exposure to, nor have m uch sym pathy for, writings in a naturphilosophisch m ode. Yet, lim ited as they were to a few topics, the above-identified sim ilarities b e­ tween M ayer and Schelling rem ain strong and should no t be brushed aside too easily. Given th a t th e specific topics of relevance were reasonably well represented in th e Naturphilosophie literature, it is possible th a t M ayer encountered th em in some as yet unidentified and m ore ‘scientific’work published closer in tim e to the years of his education and creative intellectual life. I personally regard this as the likeliest possibility. T he only other explanation would seem to be either an ad m it­ tedly possible coincidence of convergent considerations or an exceedingly problem atic active Zeitgeist a la R upert Sheldrake’s m orphic fields. Even granting th e first alternative, however, one m ust be careful to specify just w hat is being explained, and just w hat is being claim ed. W h a t is being explained are certain aspects of M ayer’s early confusion surrounding central-force m otions and th e idea th a t force m ight be created in “organism s” like the solar system. Even at th at, Naturphilosophie does no t seem to provide sources for M ayer’s allim p o rtan t m isunderstanding of th e parallelogram of forces, derived from the standard scientific works of th e day, th e application of which to central-force m otion apparently first led him to entertain th e possibility th a t force m ay be created. Naturphilosophisch m ight th en have been (merely?) the exposition and term inological packaging of those ideas. Even the ostensibly telltale concepts of indifference and the neutralization of differences had close analogs in contem po­ rary physics and chemistry. W h a t a Mayer-Naturphilosophie connection does not explain is M ayer’s conception of force— including its uncreatability and inde-

structibilitv— let alone his notion of the quantitative equivalence betw een heat and m otion— th at is, the central features of his theory. Nor does it help in under­ standing th e physiological ideas th a t provided th e initial context for the develop­ m en t of his theory. For the m ost part M ayer's work can be situated quite ade­ quately w ithin the context provided by m ainstream work in physiology, physics, and chemistry; such metaphysical issues as may have been im portant did not in any event belong to Naturphilosophie. Nor, in the m ain, does M ayer’s writing sound at all naturphilosophisch. I would even venture to say that, insofar as Naturphilosophie exerted any influence on him , it was an influence th a t he had to get past on his way to clarity, not an influence th a t helped guide him to energy conservation. Remove all the suspected traces of Naturphilosophie, and one can still (so to speak) get Mayer to his m ature conclusions. Q uite aside from th a t judgm ent, there rem ains the m ore general issue of what one is in fact claim ing by (for example) identifying as naturphilosophisch certain aspects of M ayer’s work. Even if th at identification is valid, the fact rem ains th at th e relevant topics— indifference, the generation of light som ehow in connection w ith gravitating bodies, etc.— make up a very small part of th a t larger exuberant philosophical whole known as Naturphilosophie, alm ost all of which is entirely irrelevant to an understanding of M ayer’s ideas. Again, alm ost all of the m ost characteristic features of Naturphilosophie— Steigerung, antitheses, tripartite hi­ erarchies, and the rest— are quite w ithout traces in M ayer’s work. It would thus seem to m e problem atic in any account to speak simply of th e influence of Naturphilosophie on Mayer. T he vexing issue of identity broached here will be addressed in chapter 8. For the present, I would only note th a t the traditional way of asking and answering such questions of influence operates at too great a level of abstraction. As this entire book has sought to illustrate, it is only by avoiding general identity labels and paying atten tio n to specific problem s w ithin specific and historically reasonable contexts th a t the historian can adequately render the past. O n th e other side of th e claims equation— th at is, with respect to what one claims to have shown about Mayer— even if the naturphilosophisch pedigree of th e aspects of his work under consideration were solid and unobjectionable, it would still n o t be accurate to state simply th a t Mayer was influenced by N aturphi­ losophie w ithout specifying w ith regard to what and to what extent. After all, the only reason anyone pays any atten tio n to M ayer is because of his role in th e E u ­ rope-wide form ulation of th e principle of the conservation of energy, and, if my judgm ent is correct, the role Naturphilosophie played in th e developm ent of his ideas was not only m inor at best, b u t also largely negative. In an im portant regard M ayer’s work was no t a whole, b u t a mosaic of pieces drawn from a variety of sources, pieces whose shape and m eaning changed as th e more-or-less final pic­ ture emerged. Pieces labeled Naturphilosophie did not appear in th a t final picture, nor did their earlier presence, such as it may have been, facilitate its com pletion.

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C H A P T E R

E I G H T ·

A ssessm ent and C onclusions

M y g o a l i n this study has b een to m ake M ayer historically intelligible, th a t is, to

reconstruct his probable context and th e likely specific issues around w hich his reflections crystallized in such a way as to illum inate b o th th e w hat and the why of his (conventionally so-term ed) discovery of th e conservation of energy. It is in th e location of M ayer’s thin k in g w ithin a rich co n tex t of contem porary problem s and th em es th at, in my opinion, the book’s strength lies. As it turns out, M ayer’s work fell during a crucial period of accelerated change in th e assum ptions and id en tity of th e life sciences in Germ any, and th e particulars of M ayer’s story high­ light im p o rtan t aspects of th e larger state of affairs. For exam ple, during th e few years extending from th e late 1830s to the m id1840s, th e vital force w ent from being generally granted as essential to the expla­ n atio n of organic processes to being widely criticized as em pty and unscientific. At th e sam e tim e, Liebig defended a conception of th e vital force th a t m ore force­ fully th an ever b ro u g h t into focus th e differences betw een its developm entally directive and its physiologically operative— th a t is, w ork-producing— functions. Its directive functions receded in im portance as physiology proper cam e to ex­ clude Entw icklungsgeschichte, just as th e vital force lost th e ontological validation it h ad enjoyed from analogies w ith m ind and soul as physiology cam e m ore and m ore to exclude such en tities from its purview. And its im plicitly w ork-producing functions ran afoul of th e increasingly taken-for-granted assum ption th a t all vital processes are underlain by processes of m aterial exchange. Issues having to do w ith th e scope and definition of science and th e legitim acy of scientific concepts were in tu rn situ ated against th e rise of a self-assertive scientific m aterialism . In such a co ntext M ayer sought to occupy a precariously narrow position: to accept a physiology based on Stoffw echsel and the laws of physics and chem istry while rejecting a despiritualizing scientific m aterialism and (later) an antiteleological and antitheological D arwinism . T h e course and m eaning of M ayer’s theory of force can be understood only against th e backdrop of these issues. At first th e vital force was n o t a critical problem for him ; indeed, his acceptance of th e creation of force in divinely or­ dered “organism s” like th e solar system , his early restriction of his ideas to inani­ m ate n ature, and his peculiar reluctance (until around 1844/45) to criticize Liebig’s conception of the vital force all strongly suggest th a t he at least im plicitly accepted th e legitim acy of a vital force for several years after 1840. A fter all, belief in a conventional vital force len t analogical legitim ation to his interp retatio n of cosm ic systems, giving him a vested interest in its acceptability. And his convic­ tio n th a t his theory of force refuted m aterialism — in vindicating the autonom ous existence of a n o n m aterial substance— and th a t it solved im p o rtan t problem s of

m etaphysics suggests th at he was responsive to the widespread discussion during the 1830s of th e relationship betw een the vital force, th e soul, and th e im ponder­ ables. W h a t caused him to change his m ind about the creatability of force is not clear from the surviving evidence, though part of th a t change m ust have had to do with th e resolution of his confusions concerning central-force m otions. At the same tim e, increasing criticism of the vital force as unscientific just as Liebig was m aking unprecedentedly strong (if n o t always self-consistent) claims for its ener­ getic efficacy may also have prom pted M ayer to rethink the m atter. As I have also argued, problem s relating to the creation and destruction of th e vital force, the soul, and th e im ponderables would have provided M ayer with a rich specific con­ text within which to reflect on those crucial issues of conservation, issues not com m only broached in th e physical and chem ical literature of the day. T h e im portance of relating context to specific problem s is highlighted by com ­ paring Mayer to Liebig and Lotze. M ayer and Liebig shared m uch of the same scientific context, and Liebig even delivered him self of m any an utterance that, taken by itself, m ight seem to make him a contender for the codiscoverer title; yet Liebig never m ade a sustained atte m p t to form ulate a new conception of force— his toying with th e vague notions of K raftmom ent and Bewegungsmoment was a feeble flash in th e pan— and h e was bafflingly slow to recognize it even after several others had. (Recall th a t both M ohr and Mayer published their relevant work in Liebig’s Annalen.) In part th a t was (I suspect) because of his denial th a t forces can exist independently of m atter, in part because Liebig was not consis­ tently a deeply consequential thinker. Similarly, his appreciation of issues of cau­ sality as they related to his (som etim e) conviction th a t all organic functions m ust be underlain by processes of m aterial exchange did no t translate into a clear gen­ eral appreciation of energetic considerations. For the rest, Liebig’s ‘failure’ under­ scores th e crucial historical im portance of the particular issues th a t occupied M ayer’s thinking— including, too, his childhood failure to construct a perpetuum mobile. In som ew hat the sam e way, it underscores the im portance of historical contingency over w hat m ight appear to be internal logic to note th a t Lotze, a self-professed m echanist and antivitalist, could still accept th e effective creation and destruction of force, if to be sure for his own contingent philosophical reasons. If at tim es this study of Mayer has seem ed like a study of Liebig, too, th en th at is due to th e further fact th at M ayer’s life and work intersected repeatedly and intim ately w ith Liebig’s. Mayer reported th a t he was prom pted to com pose his “Remarks on the Forces of Inanim ate N ature”— and to tender it to Liebig’s A nnalen— as a result of reading Liebig’s essay on “T he Vital Process in th e Animal, and th e A tm osphere”; and his book of 1845 is unintelligible except as a response, in part, to the questionable legitim acy of Liebig’s handling of the vital force in his A nim al Chemistry. It has been my goal to reconstruct, as far as th e evidence and reasonable specu­ lation will allow, th e p ath of M ayer’s thinking from his initial surprise at the color of th e blood he let on arriving in the D u tch East Indies, to the m ature statem ent of his ideas in 1845, down to his late conception of Auslosung, the last represent-

ing the conclusion of a long struggle to com e to term s w ith th e proper scope and m eaning of concepts like force and cause. M ayer’s 'discovery’ had a com plex inter­ nal structure ex tending over m any years, during which the scope and m eaning of his theory u n d erw ent profound change. N otable is the extrem e contraction of his effective sphere of interest, at least as it pertained to th e ideas h e was willing to m ake public: from a grand view of physics and m etaphysics— recall his early con­ versations w ith R iim elin— to th e m echanical equivalent of h e a t.1 O ne of th e rea­ sons M ayer has been so hard to un d erstan d is th a t th e context of his earliest reflections left few traces in his published writings. Just as M ayer’s use of m a th e ­ m atical symbols was frequently sym bolic and no t literal— recall his use of zero as a pseudocoefficient in expressions like 0 2Ac— so, too, was force for him m ore th a n a physical co ncept susceptible to q uantitative determ ination: at another level, it sym bolized an entire antim aterialistic worldview, and was a p o in t of crys­ tallization ab o u t which a new physics and a new physiology could organize th e m ­ selves. If my reading of M ayer is correct, in an a tte m p t to accom m odate him self to contem porary norm s in th e natural sciences he kept th e m etaphysical m ean ­ ings of force o u t of his m ore self-consciously scientific writings. It is ironic, I think, th a t by playing th e gam e of hypothesis-free objective science, by refusing (for the m ost part) publicly to engage ontological questions, and by em phasizing logic and m ethodological considerations, M ayer essentially assured th a t an appropriately recast co ncept of force would be easily assim ilable by a m inim ally readjusted sci­ entific m aterialism . In som e ways M ayer’s theory was com posed of two strangely separate parts: the equivalence of h eat and m o tio n — his earliest and always cardinal insight— and th e sub seq u en t elaboration of an overarching theory of force. Such a distinction may explain an apparent inconsistency w ith respect to M ayer’s conception of th e o n ­ tology of force. O n th e one hand, I have argued th e centrality of his reflections on th e n atu re of th e im ponderables an d th e soul, and on th e sim ilarities and differ­ ences, ontological and otherw ise, betw een force and m atter. Yet he elsewhere denied a tta c h m e n t to any particular ontological conception of h eat, and h e o th er­ wise grounded his theory of force on abstract general principles (causa aequat effectum and th e like). Perhaps his abiding nonontological un d erstan d in g of h eat reflected th e circum stances of his original deduction, soon after his bloodletting observations, of th e necessity of a co n stan t num erical relationship betw een h ea t and m o tio n , a d ed u ctio n wholly ind ep en d en t of any representation of th e nature of heat. And perhaps it was precisely in his sub seq u en t creation of a general theory of force th a t ontological considerations cam e— for the first tim e, b u t crucially— to guide his thinking. His appeal to general philosophical principles w ould appear to reflect b o th his process of discovery— W h a t are causes? C an force ever be cre­ ated?— and his later a tte m p t to justify his theory by grounding it on ostensibly universally valid principles. T he equivalence of heat and m otion was thus b o th logically and autobiographically in d ep en d en t of any ontological conception of force or its universal principled uncreatability or indestructibility. In his m ore m ature writings M ayer never insisted on th e im portance of his having identified a new conceptual entity, force, even as physics became in a sense

th e science of force— th a t is, energy. H e never ad opted a phrase equivalent to the “conservation of energy”— in part to avoid suggesting th a t his theory was merely an extension of th e principle of th e conservation of vis viva— and he called his collected works The M echanics o f Heat. In som e ways M ayer’s status as codis­ coverer of th e conservation of energy represents a fu rth er crystallization of m ean ­ ing w ith respect to th e co n ten t of his work w hen assessed from a perspective broader th a n th a t of his work alone— th a t is, from the perspective of a new field of m eaning. M ayer’s conception of physics as th e science of force and chem istry as the sci­ ence of m a tte r captured m ore th a n one im p o rtan t insight. He forged his concept of force and th e principle of its uncreatability and indestructibility in close con­ ju n ctio n w ith his co n tem plation of the n ature of th e im ponderables and of the essential properties of m atter— his guiding analogy par excellence. As I argued in ch apter 4, there was no explicitly form ulated and generally invoked principle of th e conservation of m a tte r in th e physics and chem istry literature of M ayer's day: w hat he did was in essence to create, for him self, both principles sim ultaneously. (How the conservation of m a tte r becam e the conservation of mass is an o th er story.) Similarly, M ayer’s u nderstanding of force represented b o th a reconceptual­ ization of th e erstw hile im ponderables— recall his term inological wavering in 1842— and a struggle to specify th e proper m eaning of cause in physics. To p u t it figuratively, on th e one side he h ad to take th e m aterial aspect away from the im ponderables, on th e o ther side he had to m ake force m ore th a n a m ere property of m atter. A lthough M ayer personally was n o t an im p o rtan t enough figure in the world of science to have co n trib u ted m u ch to its transform ation, his insights nev­ ertheless foreshadow ed th e growing im portance of self-consciously enunciated fu n d am en tal principles as th e conceptual foundations of scientific knowledge a la R udolph C lausius. As E rnst C assirer p u t it, “In its general structure n in etee n th century physics m ight be characterized as a physics n o t of images and m odels bu t of principles.”2 Johannes M uller’s a tta c h m e n t to em piricism and reluctance to take a m ore principled (and energetic) approach to the question of anim al heat sym bolizes, in its own small way, an earlier conception of science. T h e reader may have noticed a disharm ony betw eeen th e historiographical style of th e ch ap ter on M ayer and N aturphilosophie and th a t of the rest of the book. For th e m ost part I have striven to write an historical account in term s of particular people, particular works, and particular ideas w ithout feeling any need to identify th em as belonging to this or th a t trad itio n .5 Indeed, th e desire to assign M ayer to one or an o th er nam ed philosophical tradition, w ithout due considera­ tio n of th e historical particulars on b o th sides, has been the bane of m uch of the scholarship on Mayer. T h u s few have noticed th a t th e alleged “unity of forces” was n o t a p ro n ounced m otif of either M ayer’s or of m uch N aturphilosophie. How ­ ever, in devoting a ch ap ter to N aturphilosophie I could n o t wholly escape the im plicit dangers of ‘identificationist’ historiography short of w riting a second and m uch longer book. T h e interlocking questions of who th e representatives of N aturphilosophie were and w hat its principal characteristics are cannot be ade­ quately answered short of a broad and deep analysis of a large m ass of roughly

like-spirited sources. In so doing, one w ould need to distinguish a K antian strain of natural philosophy th a t shared certain conceptions with N aturphilosophie (such as dynam ism ) as it differed from it profoundly in others (such as w ith re­ spect to efficient versus formal causality). O n e would also need to distinguish an architectonically luxuriant Naturphilosophie from antisystem atic R om antics like G oethe. Nor should one expect clean divisions, since m any individuals— such as Eschenm ayer, Burdach, O ersted, and m ineralogist C hristian Sam uel W eiss— drew inspiration from Kant, Schelling, and a w ealth of o th er som etim es overlap­ ping sources.4 In any event, ideas can be classified into abstract conceptual group­ ings m ore easily th a n historically m ultifaceted people. T he ever-present danger is th a t generalized descriptive categories, th e use of which is all b u t indispensable in practice, very quickly becom e hypostasized into oversim plified explanatory classi­ fications. Even after th a t kind of classificatory analysis m ight have b een accom plished, it would rem ain problem atic to identify an individual as a representative of a partic­ ular trad itio n , as if th a t identity som ehow covered and explained all aspects of th a t person’s work, and as if any influence he or she m ight have on som eone else could be tagged as due to th a t tradition. Som etim es one will in fact wish to make such claims, b u t o th er tim es th e casual use of insufficiently considered identity labels results in a style of historiography dangerously abstracted from th e com ­ plexities of historical reality and liable to im pose ill-fitting categories on unruly d a ta .5 Just as M ayer m u st be explained in term s of his co n tex t w ithout being reduced to th a t co ntext, so too m u st his work be understood at least in part in term s of his biography and his personality. O f crucial im portance were, for exam ple, his failed childhood a tte m p t to construct a p erp etu u m m obile, his m edical training, and th e accident of fate th a t confronted him w ith unexpectedly red venous blood in a h o t clim ate. Likewise his religiosity, in particular his belief in th e im m ortality of th e soul and his oppostion to m aterialism , co n trib u ted in im p o rtan t ways to th e shaping of his theory of force as an autonom ous entity on an ontological par with m atter. His character, too, was n o t w ith o u t influence on th e kind of science he did. His strong will; his passionate atta c h m e n t to slogans and quotations; his pro­ digious mem ory; th e dogged consequentiality of his m ind, w hich delighted in b o th th e logical and th e paradoxical; his preoccupation w ith principles, laws, and rules; his in terest in causality; his quirkiness and originality— such traits all left th eir traces on his scientific work. Insofar as this study can be taken as typical, it illustrates n o t only th e inseparability of th e individual scientist from his or her social, intellectual, and scientific com m unities, b u t also the inappropriateness of tTying to u n d erstan d th e dynam ics of scientific change w ith o u t due atte n tio n to biographical particulars. Should historians venture to judge th e quality of a scientist’s work, or m ind? S uch a q u estion is n o t usually relevant to the kinds of things we wish to say, though in fact M ayer has enjoyed a rather poor reputation as a thinker ever since anyone began to take notice of him . And n o t surprisingly, since his earliest literary endeavor was confused and obscure, since his forays into public speaking late in

life w ere easy to p u t dow n as th e em b arrassin g ly C h ris tia n effusions of an in te lle c ­ tu a l lig h tw eig h t, since h e never d id a n y th in g o f su b sta n c e o th e r th a n his work on force, a n d sin ce h e d id in fa c t su ffer from fits of insanity. Jolly’s o ft-re to ld a n e c ­ d o te alo n e pain fu lly reveals th e low e ste e m in w h ich he was h eld by m a n y scien ­ tists d u rin g th e seco n d h a lf o f th e century, d e s p ite h is grow ing sta tu re a m o n g a b ro a d e r p u b lic as a h e ro o f G e rm a n science a n d th e p rid e of his b irth p la c e . N o r did a la te r h isto rio g ra p h ic a l asso ciatio n w ith N a turphilosophie le n d m u c h polish to M a y e r’s scien tific re p u ta tio n . M y ow n e s tim a tio n o f th e q u a lity of M a y e r’s m in d has flu c tu a te d over th e years, only to gel in to an a b id in g am b iv alen ce. O n th e o n e h a n d h is dogged lack of a p p re c ia tio n for so m e o f th e sim p le st facts of m a th e m a tic a l physics a n d th e a m a z ­ ing c o n sid e ra tio n of various sy stem s of co in ag e in th e c o n te x t of an address in 1870 o n " th e m e a n in g of in v ariab le m a g n itu d e s ”— a m o n g o th e r possible e x am ­ ples— d o n o t b e sp e a k m u c h sc ie n tific s o p h is tic a tio n .6 O n th e o th e r h a n d , m an y of his early co n fu sio n s w ith re sp e c t to c e n tra l-fo rc e m o tio n s a n d th e m e asu re of th e q u a n tity o f m o tio n (as my) re fle c ted th e c o n sen su s o f th e b e s t c o n te m p o ra ry physics te x ts, a n d his c a lc u la tio n o f th e m e c h a n ic al e q u iv a le n t of h e a t in th e only way th e n possib le w ith e x istin g d a ta was in fa c t an im pressive a c c o m p lish m e n t, all th e m o re c o n sid e rin g his d eficien cies in physics a n d m a th e m a tic s. T h e n , to o , it was M ayer a n d n o t, for ex am p le, L iebig w ho a p p re c ia ted th e n e e d for a n ew c o n ­ c e p t of force, a n d w ho w orked h is way th ro u g h th e co n sid erab le term in o lo g ica l a n d c o n c e p tu a l c o n fu sio n of his sources to forge ju st su ch a c o n c e p t. Ju d g ed ag ain st c o n te m p o ra ry n o rm s, his a c h ie v e m e n ts w ere b rillia n t. In sofar as M ayer refu sed to go th e m a te ria listic ro u te o f in te rp re tin g forces as p ro p e rties o f m a tte r, b u t in s te a d in siste d on th e o n to lo g ical in d e p e n d e n c e of force (read h e re energy), h e w'as o n su rer g ro u n d th a n m o s t o f his p re e n e rg etic ist c o n te m p o ra rie s— allow ­ ing for th e fa c t th a t n e ith e r h e n o r th e y a n tic ip a te d m ass-energy eq u iv alen ce. T h e p o ssible valid ity of M a y e r’s analogical linkage b e tw e e n force a n d soul— as I have re c o n s tru c te d it, follow ing A u te n rie th ’s le a d a n d H irn ’s e x a m p le — is precisely th e k in d of q u e s tio n th a t n o lo n g e r h a d m u c h re sp e cta b le scien tific cu rren cy in G er­ m a n y a fte r th e 1840s. Ironically, th e triu m p h o f H e lm h o ltz ia n c o n serv a tio n of energy c o n trib u te d m ig h tily to th e se c u rin g o f th e new scien tific d isp e n sa tio n .

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A P P E N D I X E S

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A P P E N D I X

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T im elin e of R o b ert M ay er7S Life an d W o rk 1

1804 N ovem ber 5: m arriage of R obert M ayer’s parents 1805 D ecem ber 18: b irth of his brother, Friedrich F erdinand (“F ritz”), who took over th eir fath e r’s apothecary ca. 1832/33 1810 M ay 3: his father (since 1803 apothecary in Lorch) purchased th e apothecary “Z u r R ose” in H eilbronn 1810 A ugust 22: b irth of his brother, C arl G ustav, w ho b ecam e an apothecary in M esskirch and Sinsheim 1814 N ovem ber 25: b irth of Julius R obert M ayer in H eilbronn 1829 Spring: left h o m e to a tte n d th e evangelisch-theologisches Vorbereitungsseminar in Schontal, following his friend G ustav R iim elin, w ho had gone there th e previous fall 1831 S eptem ber: returned to H eilbronn; assisted in his fath er's ap othecary till May 1832 and au d ited th e highest class of th e G ym nasium there 1831 S ep tem b er 12-13: took th e Studienkandidatenprufung in S tu ttg a rt, th e equivalent of th e later A biturientenexam en2 1832 M ay 17: en tered th e E berhard-K arls-U niversitat in T iibingen to study m edicine 1836 A ugust 12: M ayer and W ilh elm G riesinger am ong th e cofounders of th e stu d e n t corps “G u estp h alia” 1837 M arch 13: expelled from th e university for one year du e to m em b ersh ip in a forbid­ den organization 1837 S um m er-F alI: traveled to Sw itzerland; visited clinics in M u n ich and Vienna 1837 O cto b er 19-23: in a le tte r to Paul F riedrich Lang, a friend from S chontal, M ayer discussed his planned trip to Java 1838 January 24: pardoned by King W ilh elm I of W iirttem b erg to b e able to take his m edical exams 1838 M arch 2-3 : took th e first sta te m edical exam (erste m edizinische Staatsprilfung) in T ub in g en ; the oral portion of th e exam followed on M arch 5 1838 M arch 6: took (oral) doctoral exam 1838 July 25: prom otion to doctor of m edicine and surgery in T iibingen 1838 A ugust 15—20: took th e second state m edical exam in S tu ttg a rt (m edicine on A ugust 15-16, surgery on A ugust 17—18, and obstetrics on A ugust 20) 1838 A ugust 23: licensed to practice m edicine 1838 N ovem ber-D ecem ber: atten d e d m edical lectures an d d em o n stratio n s in M unich 1839 M arch 4: began practicing m edicine in H eilbronn 1839 June 15: took exam in A m sterdam to becom e a ship’s d o ctor in D u tc h service 1839 S eptem ber 25: ad m itte d to D u tc h service as ship’s doctor 1839 Fall—1840 February 14: in Paris to study m edicine; atte n d e d prim arily clinical and surgical dem onstrations; b ecam e friends w ith C arl Baur 1840 February 23: left R otterdam aboard th e ship Java to sail to th e D u tc h E ast Indies 1840 M arch 9: reu n ited w ith his chest of books 1840 June 8: ship reached th e S unda straits 1840 June 11-23: at the roads off Batavia

1840 June 20-24: le t blood seven tim es (twice on th e 20th, once each on th e 21st a n d 22nd, and th ree tim es on th e 2 4 th )3 1840 July 4 -A ugust 30: ship anchored off Surabaja 1840 ca. D ecem ber 25: Java arrived back in R otterdam 1841 February: retu rn ed to H eilbronn; resum ed m edical practice 1841 M ay 28: nam ed O beram tsw undarzt in H eilbronn (with prim arily forensic m edical responsibilities; resigned 1845)4 1841 June 16: sen t paper “U ber die q u an tita tiv e u n d q u alitativ e B estim m ung der K rafte” to Poggendorff for publication in th e A nnalen der Physik; got no reply an d th e m a n u ­ script was not returned; sen t follow-up letters on July 3 and 31 1841 July 24: began intensive correspondence w ith Baur 1841 betw een S ep tem b er 6 and 12: m eeting w ith Johann G o ttlieb N orrenberg, professor of physics at T iibingen5 1841 S eptem ber: com posed an u n title d m an u scrip t headed “sapere a u d e ” 1841 S ep tem b er 16 an d 30: publication (anonym ously) of th e second an d fo u rth of L iebig’s “C hem ische Briefe” in th e A ugsburger Allgem eine Z eitung 1841 ca. N ovem ber: m eeting w ith Philipp G ustav Jolly, professor of physics at H eidelberg 1841 D ecem ber 15: publication of Liebig’s “D er LebensproceB im T h iere, u n d die A tm osphare” 1842 M arch 31: sent th e paper “B em erkungen iiber die Krafte der u n b eleb te n N a tu r” to Liebig for publication in th e A nnalen der C hem ie u n d Pharmacie 1842 April: d ate of th e preface of Liebig’s D ie organische C hem ie in ihrer A nw endung a u f Physiologie u n d Pathologie, w hich appeared by July 16 1842 May 31: m arried by R um elin to W ilhelm ine Regine C aroline Closs (born in W in n en den on July 31, 1816) in a joint cerem ony w ith CIoss’s sister an d R iim elin’s brother; on the sam e d ate was published th e M ay H eft of Liebig’s A nnalen co n tain in g his first published paper 1842 O ctober-1843 Spring: Baur was in H eilbronn to teach m a th em atics an d physics at th e G ym nasium , and he tu to re d M ayer in m a th em atics an d m echanics 1842 N ovem ber 30: began intensive correspondence w ith G riesinger 1843 May 18: b irth of d au g h ter W ilhelm ine Elise (died 1919) 1844 January 6: d ea th of his m o th er 1844 June 11: sent G riesinger an early version of w hat eventually b ecam e Die organische Bewegung (1845); requested its retu rn on July 16 1844 July 20: sent Baur a new d raft of this work 1844 July (?): com posed an essay “U eber m edicinische Physiologie,” possibly for subm is­ sion to W underlich and R oser’s Archiv fiir physiologische H eilkunde 1844 A ugust 14: b irth of second child, C hristian R obert 1844 A ugust 21 and 30: sen t Baur u p d ated drafts and revisions late 1844/early 1845: com p leted a m anuscript en title d “T h eo rie der physikalischen Principien als G rundlage physiologischer L ehrsatze” 1845 January 3: sent Liebig th e m an u scrip t of w hat eventually b ecam e D ie orga­ nische Bewegung; retu rn ed by A ugust W ilhelm H ofm ann, L iebig’s assistant, on January 6 1845 M ay 13: d eath of second child, C hristian Robert; around th is tim e he was revising th e m anuscript of D ie organische Bewegung 1845 A ugust: stay a t spa in W ildbad 1846 April 10: Johannes M uller retu rn ed to him a m an u scrip t h e h ad su b m itte d for p u b li­ cation in th e Archiv fiir Anatom ie, Physiologie und wissenschaftliche M edicin on th e connection betw een oxidation and m echanical effect in th e organism

1846 June 12: b irth of th ird child, A nna 1846 July 27: th e Paris A cadem y received his paper “S ur la p ro d u ctio n de la lum iere et de la chaleur du soleil” 1847 June 25: b irth of fourth child, Julie W ilhelm ine 1847 July 22: nam ed Stadtarzt in H eilbronn (charged w ith th e care of th e city’s poor and th e lower civil servants); resigned S ep tem b er 1873 1847 A ugust 23: Joule’s co m m u n icatio n on th e m echanical equivalent of h e a t read a t th e Paris A cadem y 1848 A ugust 19: d ea th of th ird child, A nna, from w hooping cough 1848 A ugust 25: d e a th of fo u rth child, Julie W ilhelm in e 1848 O cto b er 16: M ayer's priority claim vis-a-vis Joule read at th e Paris A cadem y 1849 January 22: Joule’s reply to M ayer read a t th e Paris A cadem y 1849 S eptem ber 19: b irth of fifth child, Paul T heo d o r (died 1909) 1849 N ovem ber 12: M ayer’s reply to Joule read at th e Paris A cadem y 1850 May 28: severly injured him self after ju m p in g o u t of a third-floor window and falling n ine m eters to th e ground 1850 S eptem ber 8: d e a th of his father 1850 O cto b er 13: b irth of sixth child, E m m a Johanna (died 1894) 1851 Sum m er: stay at spa in W ildbad 1852 April: short stay a t sanatorium in K ennenburg (near Esslingen) 1852 M ay-July 31: stay at C hristo p h sb ad asylum (near G o p p in g en ) 1852 A ugust 1-1853 S eptem ber I: forced stay at W in n e n th a l asylum (near W in n en d e n ) 1854 January 12: b irth of seventh child, R ichard Friedrich 1856 April 27-M ay 30: stay at sanatorium in K ennenburg 1858 S eptem ber: atte n d e d th e m eetin g o f G esellschaft d eu tsch er N a tu rfo rsc h e ru n d A rzte in Karlsruhe 1858 N ovem ber 10: nam ed corresponding m e m b er of th e N atu rfo rsch en d e G eselIschaft in Basel (at th e instigation of C h ristian Friedrich Schonbein) 1859 July 4: aw arded an honorary docto rate by the philosophical faculty of th e University of T iibingen 1859 N ovem ber 28: nam ed corresponding m e m b er of th e Bavarian A cadem y of Sciences in M u n ich (subsequent honorary m em berships and awards n o t listed here) 1860 January I: d ea th of seventh child, Richard Friedrich 1862 June 6: John Tyndall recognized M ayer’s priority in a lectu re at th e Royal In stitu tio n in L ondon 1863 S eptem ber: a tte n d e d th e m eetin g of th e G esellschaft d eu tsch er N aturforscher und A rzte in S tettin 1864 A ugust 22—24: atten d e d th e m e etin g of th e Schw eizerische N aturforschergesellschaft in Z iirich, where he m e t Tyndall 1865 O cto b e r 3—N ovem ber I: second stay at sanatoriu m in K ennenburg 1867 July: publication of D ie M echanik der W drm e 1867 N ovem ber 5: aw arded personal nobility w ith bestow al of th e W iirttem b erg R itterkreuz 1869 S ep tem b er 18: delivered a talk “U ber nothw endige C o n seq u en zen u n d Inconsequenzen d er W a rm em e ch a n ik ” a t th e m eetin g of th e G esellsehaft d eu tsch er N aturforscher u n d A rzte in Innsbruck 1871 A ugust 8 -N ovem ber 15; last stay at sanatorium in K ennenburg 1878 M arch 20: d ea th a t age 63 from tuberculosis 1899 June 7: d ea th of M ayer’s wife, W ilh elm in e Closs 1944 D ecem ber 4: H eilbronn destroyed by Allied air attack

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Courses

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D I X

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~Iayer .

Took at the University. of Tubingen, 1832-37

information IS based in the fIrSt instance on the Belegbogen (a sort of preregistration fonn) prepared b~ \Iayer listmg the courses he anticipated takmg during the ensuing semester. Ho\\'e\'er, not all the courses so listed (belegO \\ ere actually offered or taken, and the entries belo\\' ha\'e been edited in accordance with the Horeriisten (class rolls) of students attending the courses given and \\'ith the pnnted \ oriesungsrer:::elchnis (course list) for that semester.! The letters Hand \' m brackets after a course ent~ indicate that \!ayer's name appeared on the appropriate Horer/iste and that the course \\'3S listed in the \ oriesungsl'er:::eichnis for that semester, Sometimes there are variations m the name of the course as gi\'en in these three sources; that of the Horer/zste is gi\'en priont~ as representing most accurately the focus of the course as actualh gi\'en, Variant course names from the Belegbogen are identified by the letter B,: \Ia\er's Belegbogen are in the Uni\'ersitiitsarchi\, Tubmgen ("UAT"), Personalakten, -tOIl·H. NT. 88. The Horerlisten are UAT ; lin, \\,here n is the particular number for each individual as given m the following list of the mstructors \\'Ith ",hom \Iayer listed courses for the designated semesters:

THE FOLLO\\T\G

,-\utenrieth. Hermann Fnednch (n= 12): \\'S 183:;/36. SS 1836 .-\utenneth. Johann Hemnch Ferdmand ("Kanzler \, .-\utenrieth". n=II): SS I 83-t. \\'S 1834/3:;. SS 183::; Baur. Chnstlan Jakob (n=20): SS 1832, \\'S 1832/33, SS 1836 Elsasser. Carl Lud\\'ig (n=12l)' \\'S 1832/33, SS 1833 Frank. Chnstlan Fnednch (n=I::;:;)' \\'S 1836/37 Gmelm. ChrIStian Gottlob (n=18-:-): SS IS32. \\'S 1832/33 Gmelin. Ferdmand Gottlob (n=186): \\'S 1833/34. SS 1834. \\'S 18;4/;:;, SS 183:; \larklm . .Gusta\ Fnednch (n=404)' SS 1832 Oftcrdingcr. Lud\\lg FelI" (n=464): SS 1832 Rapp. \\'dhelm Lud\\'lg In=:;18), \\'S 1832/33. SS 1833. \\'S 1833/34. \\'S 1834/3:; Riecke. Leopold Sokrates \on (n=)30) SS 1834. \\'S 1834/35. SS 1833. \\'S 1835/36, SS 1836. \\'S 1836/r SchIll. Albert Fnednch (n=:;71): \\'S 1835/36. 5S 1836. \\'51536;37 Schubler. Gusta\ (n=606)' SS 1834 I:\ote that \Ia\er seems not to ha\'e had courses mth Frank, SchdL or Schtibler.) SI'\I\lER SE\IESTER

153:

"Anatomle" \llth Baur (H, \'] ["Osteologle" Illth Baur; no H found; not listed m V for that semester] "Pharmaeeutlsche Chemle" \\'ith C G, Gmelm [H. \"J

• ca (

R 5 EST .4 K E ,.

B l

\1 4 )' E R

•

333

"SpeClelle Botamk" \\"Ith \larklm (H, V] "Ph~sik (Theoretische und Expenmental Ph~slk)" Wlth Ofterdmger (H; on Bas "Phlslk". V lIsts h\ 0 courses, "Theone der Kegebchmtte" and "Theone der Cranzen," for neIther of l\hlCh an H is extant]

\Y"TER SE\'E~TER

11),2-)3

"Allgemeine Chemle" \\lth C C. Cmelm [H, \'] "Verglelchende Anat0l11le" \\lth Rapp [H, \'] "Das Prapariren am Lelchnam" \nth Baur [H, \'; on B as "RepetItIonen der Anatomle"] "\lenschlIehe Phvsiologle" \nth Elsasser [H, V]

Sl \I\IER SE\IE33

":\lIgememe Pathologie" \\Ith Elsasser [H, \'] ["Zoologie" with Rapp; \la~er's name absent from H, m V as ":\'aturgesehichte der Thlere"]

"Der meite TheIl der speClellen Krankheitslehre" with F C. Cmelm [H, V, on Band m \ as "Specielle Theraple"] "Pathologlsche Anatomle" \\'lth Rapp [H, \] "Demonstrationen der Anatomie des \lenschen" \\lth Rapp [H, V]

Snl\lER SE\lEQER

1",H

"\latena medica" with F C Cmelm [H, \'] ",\llgememe ChITurgle" \\'lth RIecke [H. \'j "Der erste TheIl der ;\,osologle" \\1th J H.F :\utenneth [H, Y] ["Botamk" \\"lth Schubler; no H found-Schubler died on 8 September 1834]

"Formulare" \\1th F C. Cmelm [H, \'j "Der melte Theil der ;-';osolog,e" wIth J.H f Autenneth (H, Y] "Geburtshu1f1iehe D,agnostik," Erste :\btheIlung, wIth Riecke [H; not m \'] "Clmurg,seh-geburtshulfliehe Chmk" \\lth RIecke [H, \'] ["Clmik der inncrhchen Krankhelten" \\lth F. C Cmelin; \la\er's name absent from H. same course name m \', on Bas "\led'Clmsche Chmk"J "Cursus operatIonum chlrurglcarum" \\Ith RIecke [H, \'] "DemonstratlOnen der AnatomIc de, \lemehen" \\ Ith Rapp [H. \'] "Speclelle Chirurgle, L TheIl" WIth RIecke [II, \']

SI \I\IER SE\lE