The Metaphysics of Light in the Hexaemeral Literature: From Philo of Alexandria to Gregory of Nyssa (Oxford Early Christian Studies) 2022937568, 0192869191, 9780192869197

Table of contents :
Cover
The Metaphysics of Light in the Hexaemeral Literature: From Philo of Alexandria to Gregory of Nyssa
Copyright
Acknowledgements
Contents
List of Abbreviations
Introduction
0.1 What Do We Mean When We Speak of the ‘Metaphysics of Light’?
0.2 What This Book Aims to Achieve
0.3 Old Wine in New Skins: From Light Language to the Concept of Light
0.3.1 Boyancé’s Challenge
0.3.2 A Challenge Still Not Met
0.3.3 The Need for a Fresh Start
1: ‘From Sight to Light’: A Hexaemeral Guide for the Perplexed
1.1 The Intelligibility of Hexaemeral Light
1.2 The Oculocentric Thesis
1.3 Three Arguments for Oculocentrism in the Hexaemeral Literature
1.3.1 Sight Fantastic
1.3.2 A World with a View
1.3.3 A Christocentric Vision of Creation
1.4 Rethinking Oculocentrism
1.4.1 Narrowing down the Scope
1.4.2 Sight Is Light
1.4.3 From the Phenomenal to the Noumenal
2: The Light of the World: Hexaemeral Physics and Anti-Physics
2.1 Science at the Service of Scripture
2.2 In Defence of Hexaemeral Physics
2.2.1 Origen and His Legacy
2.2.2 Introducing Gregory’s Apology
2.2.3 Approaching Nature through the Lens of Scripture: Physics as Hermeneutics
2.3 Enter Light
2.3.1 A Look behind the Scenes: The Hexaemeral Theory of Change
2.3.2 A (Meta-)Physics of Power Causality: The Consubstantiality of Fire and Light
3: The Nature of Light: The Dawn of the First Material Form
3.1 Between Physics and Metaphysics: The ‘Immateriality’ of Light
3.1.1 Scriptural Questions
3.1.2 Philosophical Investigations
3.1.3 Cappadocian Answers
3.1.4 Hexaemeral Physics
3.1.5 Hexaemeral Hermeneutics
3.2 Going Ballistic: The Singularity of the Light Ray
3.2.1 Rectilinearity
3.2.2 Light Mechanics
3.2.3 Light Kinetics
3.2.4 The Speed of Light
3.2.5 Introducing Field Theory
3.3 The Metaxu of Light: A Metaphysical Note on the Medium
3.3.1 A Medium of Light?
3.3.2 Transparency and Brightness
3.3.3 Light Semantics as Key to Light Hermeneutics
3.4 The Metaphysics of Light: A Hermeneutical Coda
3.4.1 A Dual Aspect Interpretation
3.4.2 Back to Origen
3.4.3 Philonic Beginnings
Conclusions
APPENDIX A: Response to a Critic, or What Is the History of Optics Really About?
APPENDIX B: What Is the Colour of Light?
1.
2.
APPENDIX C: ‘Light from Light’, or What Is the Meaning of Doxa and Apaugasma?
Bibliography
I. Critical Editions of Ancient Works Cited
II. Secondary Bibliography
Index of Passages
Index of Persons and Names
Subject Index
Glossary

Citation preview

OXFORD EARLY CHRISTIAN STUDIES General Editors GILLIAN CLARK ANDREW LOUTH

THE OXFORD EARLY CHRISTIAN STUDIES series includes scholarly volumes on the thought and history of the early Christian centuries. Covering a wide range of Greek, Latin, and Oriental sources, the books are of interest to theologians, ancient historians, and specialists in the classical and Jewish worlds.     : Preaching Christology in the Roman Near East A Study of Jacob of Serugh Philip Michael Forness (2018) God and Christ in Irenaeus Anthony Briggman (2018) Augustine’s Early Thought on the Redemptive Function of Divine Judgement Bart van Egmond (2018) The Idea of Nicaea in the Early Church Councils,  431–451 Mark S. Smith (2018) The Many Deaths of Peter and Paul David L. Eastman (2019) Art, Craft, and Theology in Fourth-Century Christian Authors Morwenna Ludlow (2020) The Acts of the Early Church Councils Production and Character Thomas Graumann (2021) Nemesius of Emesa on Human Nature A Cosmopolitan Anthropology from Roman Syria David Lloyd Dusenbury (2021) Fallen Angels in the Theology of St Augustine Gregory D. Wiebe (2021) Jerome’s Commentaries on the Pauline Epistles and the Architecture of Exegetical Authority Andrew Cain (2021) Tatian’s Diatessaron Composition, Redaction, Recension, and Reception James W. Barker (2021)

The Metaphysics of Light in the Hexaemeral Literature From Philo of Alexandria to Gregory of Nyssa ISIDOROS C. KATSOS

Great Clarendon Street, Oxford, OX2 6DP, United Kingdom Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide. Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries © Isidoros C. Katsos 2023 The moral rights of the author have been asserted First Edition published in 2023 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, by licence or under terms agreed with the appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this work in any other form and you must impose this same condition on any acquirer Published in the United States of America by Oxford University Press 198 Madison Avenue, New York, NY 10016, United States of America British Library Cataloguing in Publication Data Data available Library of Congress Control Number: 2022937568 ISBN 978–0–19–286919–7 DOI: 10.1093/oso/9780192869197.001.0001 Printed and bound in the UK by TJ Books Limited Links to third party websites are provided by Oxford in good faith and for information only. Oxford disclaims any responsibility for the materials contained in any third party website referenced in this work.

Acknowledgements This book began as a dissertation at the University of Cambridge under the supervision of Rowan Williams. To my PhD supervisor I owe a profound debt of gratitude for teaching me ergois and logois that philosophy and theology should not be pursued merely as an academic endeavour but should rather be experienced as a way of life. This study is my response to his teaching. I also wish to thank Douglas Hedley for being the internal examiner of my dissertation and for his undiminished support and collaboration over the years, not least through the Cambridge Centre for the Study of Platonism. I am deeply grateful to Paul Kalligas, whose scholarship and mentorship have been fundamental in developing this book. I thank Tom Perridge from OUP and the series editors Gillian Clark and Andrew Louth for generously accepting the book for publication in the Oxford Early Christian Studies series. Andrew Louth has guided the publication of this book with wise and deeply encouraging advice. I am also grateful to the two anonymous readers, whose comments greatly improved the final manuscript. Christian Hengstermann has been an ideal friend and collaborator since our Cambridge time together. I thank him for reading the manuscript thoroughly and giving me precious feedback. I also thank Rachel Evan Webb, Henry Clarke, and the editorial team of OUP for their tremendous editorial assistance, together with Artur Suski and Konstantina Morou for their help in compiling the Indexes of Persons and Passages. I also wish to express my gratitude to Oded Irshai, the Director of the Center for the Study of Christianity at the Hebrew University of Jerusalem, and my colleagues at the Center, especially Guy Stroumsa, David Satran, Brouria BittonAshkelony, Yonathan Moss, David Lloyd Dusenbury, and Francesco Celia, for their tremendous friendship and support. My Postdoctoral Fellowship at the Center made possible the turning of the dissertation into a book manuscript. I am also indebted to Diana Lipton and Chaim Milikowski for opening up their hearts and home, initiating me into the richness and warmth of Jewish hospitality. Last but not least, I am grateful to the Fellowship and Community of Campion Hall (Oxford) for their friendship and support during the editing phase of this book. The initial dissertation was made possible due to generous funding from the British Arts and Humanities Research Council, Pembroke College (Cambridge), the George and Marie Vergottis Foundation, the Theological Studies Fund at the Faculty of Divinity (Cambridge), the Leventis Foundation, and the Church of Greece. My gratitude to them is hereby acknowledged. A preliminary version of

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the argument of this book is published in ISIS 110/2 (2019), 270–82 (https://doi. org/10.1086/703515). I thank Floris Cohen, who as journal editor encouraged its publication and the public discussion that followed; and the History of Science Society for the kind permission to use some of the material in this book. I also wish to show my appreciation to Brill publishers for the kind permission to use the following translated quotations as epigraphs: in ‘Conclusions’, a quotation from Frederick W. Norris (ed.), Lionel Wickham and Frederick Williams (tr.), Faith Gives Fullness to Reasoning: The Five Theological Orations of Gregory Nazianzen (Leiden: Brill, 1991); in ‘Appendix B’, a quotation from David Runia, Philo of Alexandria: On the Creation of the Cosmos According to Moses (Leiden: Brill, 2001). Finally, I owe my gratitude to His Beatitude Archbishop Hieronymus II of Athens and All Greece for his constant encouragement and support of my academic pursuits. Without his personal blessings, none of this would have been possible. Similarly, I am deeply grateful to His All Holiness Ecumenical Patriarch Bartholomew for his permission to continue my liturgical duties while working academically in Cambridge and Oxford; and to His Beatitude Patriarch Theophilus III of Jerusalem for his Abrahamic hospitality during my stay in Jerusalem. This book is dedicated to Metropolitan Bartholomew of Polyanni and Kilkis, who has been my lifelong spiritual guide.

Contents List of Abbreviations

ix

Introduction 0.1 What Do We Mean When We Speak of the ‘Metaphysics of Light’? 0.2 What This Book Aims to Achieve 0.3 Old Wine in New Skins: From Light Language to the Concept of Light

1

0.3.1 Boyancé’s Challenge 0.3.2 A Challenge Still Not Met 0.3.3 The Need for a Fresh Start

1. ‘From Sight to Light’: A Hexaemeral Guide for the Perplexed 1.1 The Intelligibility of Hexaemeral Light 1.2 The Oculocentric Thesis 1.3 Three Arguments for Oculocentrism in the Hexaemeral Literature

1 7 8 8 10 13

17 18 22 27

1.3.1 Sight Fantastic 1.3.2 A World with a View 1.3.3 A Christocentric Vision of Creation

27 32 38

1.4 Rethinking Oculocentrism 1.4.1 Narrowing down the Scope 1.4.2 Sight Is Light 1.4.3 From the Phenomenal to the Noumenal

47 47 49 54

2. The Light of the World: Hexaemeral Physics and Anti-Physics 2.1 Science at the Service of Scripture 2.2 In Defence of Hexaemeral Physics

61 62 71

2.2.1 Origen and His Legacy 2.2.2 Introducing Gregory’s Apology 2.2.3 Approaching Nature through the Lens of Scripture: Physics as Hermeneutics

71 76

2.3 Enter Light 2.3.1 A Look behind the Scenes: The Hexaemeral Theory of Change 2.3.2 A (Meta-)Physics of Power Causality: The Consubstantiality of Fire and Light

79

91 91 96

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3. The Nature of Light: The Dawn of the First Material Form 3.1 Between Physics and Metaphysics: The ‘Immateriality’ of Light 3.1.1 3.1.2 3.1.3 3.1.4 3.1.5

Scriptural Questions Philosophical Investigations Cappadocian Answers Hexaemeral Physics Hexaemeral Hermeneutics

3.2 Going Ballistic: The Singularity of the Light Ray 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5

Rectilinearity Light Mechanics Light Kinetics The Speed of Light Introducing Field Theory

3.3 The Metaxu of Light: A Metaphysical Note on the Medium 3.3.1 A Medium of Light? 3.3.2 Transparency and Brightness 3.3.3 Light Semantics as Key to Light Hermeneutics 3.4 The Metaphysics of Light: A Hermeneutical Coda 3.4.1 A Dual Aspect Interpretation 3.4.2 Back to Origen 3.4.3 Philonic Beginnings

107 109 109 112 118 123 125

127 127 129 130 136 138

140 140 141 144 147 147 153 155

Conclusions

159

Appendices A. Response to a Critic, or What Is the History of Optics Really About? B. What Is the Colour of Light? C. ‘Light from Light’, or What Is the Meaning of Doxa and Apaugasma?

175 175 181

Bibliography I. Critical Editions of Ancient Works Cited II. Secondary Bibliography Index of Passages Index of Persons and Names Subject Index Glossary

197 197 211 233 236 240 247

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List of Abbreviations Abbreviations of works cited are given in the bibliography. General abbreviations follow the standard bibliographical practice. Common abbreviations in this work are: GCS GNO SC

Die Griechischen Christlichen Schriftsteller der ersten Jahrhunderte Gregorii Nysseni Opera Sources Chrétiennes

Now intellect discovers the duality, because it divides until it arrives at something simple that cannot be analysed further; as long as it can it proceeds to the depth. And the depth of each thing is matter; this is the reason why matter is entirely dark, for the light is the form. Plotinus, Enn. (12) II.4.5

Introduction The first corporeal form which some call corporeity is in my opinion light. (Grosseteste, De Luce, tr. Riedl)

0.1 What Do We Mean When We Speak of the ‘Metaphysics of Light’? There are few terms that belong to the trade secrets of both philosophers and theologians. The ‘metaphysics of light’ is one of them. The term has been linked to Parmenides, Plato, Philo, Plotinus, Augustine, the Areopagite, Grosseteste, Bacon, Eckhart, Cuzanus, and Ficino. And this is just the short list.¹ The theme of light has brought scientists, historians, philosophers, and theologians to the same table and made them talk.² Light symbolism has become a codeword for the Western ‘mystical tradition’, however defined, giving it a sense of orientation, continuity, and tradition.³ Behind the popularity lies a revived interest in medieval light speculation, climaxing in a fascination with Grosseteste’s thought.⁴ Every fascination, however, comes at a price. The references to the ‘metaphysics of light’ are currently so diverse and prolific that they have nurtured a devalued and exploded term. As David Lindberg once put it: There has been much discussion of Grosseteste’s ‘metaphysics of light’ (for which I prefer to substitute the expression ‘philosophy of light’, since much of it has nothing to do with metaphysics), but this discussion has frequently suffered from a failure to make several indispensable distinctions among differing bodies of ideas. Within Grosseteste’s philosophy of light, there are at least four distinct

¹ See the overviews in Beierwaltes (1980a); Schültzinger (2003); Meyer-Schwelling (2006); Wallraff (2010), esp. 130–7. ² See the interdisciplinary contributions in O’Collins and Meyers (2012). ³ Defining the contours and setting the tone, Louth (2007). Still indispensable is the monumental study of Goodenough (1969). See also, in cross-cultural perspective, the contributions in Kapstein (2004). ⁴ For the medieval ‘metaphysics of light’ see Tavard (1950); McEvoy (1978); Hauskeller (2004); Schloeder (2012); Clarke and Bacchianti (2014). For the emphasis on Robert Grosseteste see McKeon (1948), 85–97, 156–74; Crombie (1953), 104–16, 128–31; Koyré (1956); McEvoy (1982); Lindberg (1986); Oliver (2004); Cunningham and Hocknull (2016).

The Metaphysics of Light in the Hexaemeral Literature: From Philo of Alexandria to Gregory of Nyssa. Isidoros C. Katsos, Oxford University Press. © Isidoros C. Katsos 2023. DOI: 10.1093/oso/9780192869197.003.0001

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 strands, each employing optical analogies and metaphors: (1) the epistemology of light, in which the process of acquiring knowledge of unchanging Platonic forms is considered analogous to corporeal vision through the eye; (2) the metaphysics or cosmogony of light, in which light is regarded as the first corporeal form and the material world as the product of the self-propagation of a primeval point of light; (3) the etiology or physics of light, according to which all causation in the material world operates on the analogy of the radiation of light; and (4) the theology of light, which employs light metaphors to elucidate theological truths.⁵

Lindberg’s exposition shows why so many disciplines feel attracted to the ‘metaphysics of light’, yet so little interdisciplinary consensus has been achieved, meanwhile, as to how to understand the term. In order to regain its focal meaning, we need to resist the tide, retrace our steps, and go back to where it all began. The great medievalist James McEvoy shows us the way: The term ‘metaphysics of light’ was coined by Clemens Baeumker in 1916 and has been employed widely, though not uncontroversially, ever since. It designates a whole circle of themes, a current of philosophical and religious thought that runs right through European culture from ancient times down to the Renaissance.⁶

Baeumker introduced the term Lichtmetaphysik over a century ago in an epochmaking study on the anonymous Liber de intelligentiis, which he then attributed to the medieval thinker Witelo.⁷ Baeumker spoke of ‘metaphysics of light’ to denote, very generally, the identification of the intelligible world with light. And since God was theorized in the De intelligentiis as the first principle of every intelligent nature, and every intelligent nature was identified with light, the ‘metaphysics of light’ ultimately denoted the identification of God, qua ontological foundation of reality, with some kind of primordial light. In specifying what that kind of light might be, Baeumker distinguished three ontological models and respective modes of language:⁸ • An immanentist model, according to which the divine is light properly speaking, as part of a physicalist metaphysical universe, in which God is identified with cosmic light or fire. The examples that Baeumker used

⁵ Lindberg (1976), 95. ⁶ McEvoy (2000), 87. ⁷ See Baeumker (1908). Baeumker later defended the view that the author was another ‘metaphysician of light’, Adam Pulchrae Mulieris, a generation older than Witelo, see Baeumker (1924). The question of authorship is still open. ⁸ See for the following Baeumker (1908), 357–433, esp. 360 for the tripartite classification. The criteria of ‘immanence’, ‘transcendence’, and ‘mediation–participation’ are mine. But I have only provided the categories for what Baeumker already described in words.

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include the Brahman of the Upanishads, the Heraclitean/Stoic cosmic fire, Manichean light, and, more generally, the astral deities of the Hellenistic cosmic religion. • A transcendental model, according to which the divine is ‘light’ metaphorically speaking. ‘Light’ functions here merely as a façon de parler, one of many possible ways of speaking about God, who by his very nature exceeds the limits of human thought and language. Baeumker’s examples included Plato’s celebrated light images from the central books of the Republic, the so-called ‘sun simile’ (VI 507a–509c) and the ‘allegory of the cave’ (VII 514a–520d). • A mixed model (of combined transcendence and immanence), building on a metaphysics of mediation or participation. The participatory metaphysics of this model entailed a unified and continuous notion of ‘light’, of which sensible light and intelligible light were the two extremes. Like the physicalist (first) model, the divine is here, too, light properly speaking. But unlike the physicalist model, divine light is now the transcendent intelligible archetype, of which every material-physical light is the sensible copy. Baeumker saw the beginnings of this model in Philo of Alexandria and its full articulation in later Platonism, especially in the works of Plotinus and Proclus, before it acquired its highest peak in medieval scholastic philosophy, most notably in the De intelligentiis. The metaphysical universe of Baeumker’s third model was, admittedly, ‘Neoplatonic’ and its light language ‘analogical’. The kind of analogy that Baeumker had in mind was the scholastic variant of the ‘analogy of attribution’ (per prius et posterius).⁹ In this view, ‘divine light’ was not a mere figure of speech but light properly speaking. The intelligible world was truly light (prior or original sense), while the light of the senses (like the light of the sun, the moon etc.) could only be called ‘light’ in virtue of a relation of participation to an intelligible archetype (posterior or derivative sense). As regards Christian thinkers, Baeumker’s position was ambivalent, making three incongruent claims: first, the authors of the New Testament and early Christian thinkers spoke of God as light only metaphorically. Second, post-Nicene theologians deviated from the original tradition by introducing the ‘Neoplatonic’ participatory metaphysics and its corresponding analogical language to denote the emanation of divine light to the world. As regards the transcendent divine essence and the persons of the Trinity, however, post-Nicene theologians retained the originally ‘Platonic’ metaphorical light language of the original tradition of the early Church. Implicit in this scheme was the distinction between ‘theology’ and ‘economy’ or ad intra and

⁹ On the medieval theories of analogy see Ashworth (2017).

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ad extra of God, to which Baeumker correlated the metaphorical and the analogical use of light language, respectively. The main protagonists of this binary use of language were, for Baeumker, Gregory Nazianzen and Dionysius the Areopagite in the Greek patristic tradition and Augustine and his school in the Latin tradition. Third, Aquinas criticized the Augustinian tradition for being closer to Neoplatonism than Scripture, since the scriptural language of God as ‘light’ (and of Christ as ‘true light’) had to be, under Thomas’s Aristotelian premises, metaphorical. Baeumker also warned the reader that the distinction between the three models can be hard to make, while the classification of a particular author or text as following this or that model can easily become contentious. Baeumker’s thesis would have probably remained a minor incident in the history of Western scholarship, had it not touched upon a sensitive chord. Throughout the twentieth century, continental scholars debated explicitly or implicitly, but always passionately and inconclusively, about Baeumker’s classification and model attribution. Two examples amply show how a whole century of light dialectics led to the current standstill. Giles Wetter was an early defendant of the physicalist model, which he used for the interpretation of light imagery in Hellenistic religious thought, especially the mystery cults.¹⁰ The response came almost half a century later from Franz-Norbert Klein, who, in a special monograph, argued for the contrary position, based on the writings of Philo of Alexandria and the Hermetic Corpus. Yet Klein remained enigmatic as regards his own interpretation of Philo: on the one hand, he observed the compresence of Baeumker’s transcendental and participatory ontological models in the Philonic corpus; on the other hand, he insisted that, in spite of the participatory metaphysics and in view of divine transcendence, the Philonic language of God as light had to be metaphorical.¹¹ Another famous episode in the hundred years’ war over the premodern light hermeneutics was the debate between Werner Beierwaltes and Rein Ferwerda, this time with Plotinus as the apple of discord. Beierwaltes dedicated his life’s work to the refinement and further development of Baeumker’s thesis, becoming the leading expounder of the ‘metaphysics of light’ in the second half of the twentieth century.¹² For Beierwaltes it was only the participatory model that gave rise to a proper ‘light metaphysics’ (Lichtmetaphysik), while the transcendental model allowed merely the generation of light metaphors (Lichtmetaphorik). From his doctoral thesis to his erudite studies on Plotinus and Proclus, Beierwaltes defended the participatory ‘metaphysics of light’ as the distinctive characteristic of the Platonic tradition: true being was intelligible being

¹⁰ See Wetter (1915). ¹¹ See Klein (1962), 78 (two ontological models); 72, 211–2 (metaphorical language). ¹² For the development of Beierwaltes’s thought on ‘light metaphysics’ see Beierwaltes (1957), (1961), (1965), (1976), (1980a), (1980b).

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and intelligible being was light properly speaking, while physical light was so only in virtue of its participation in its intelligible archetype. The names belonging to this tradition make up a long list, including Pythagoras and Parmenides as forerunners; Plato as the founder; and two lines of succession, through which the ‘metaphysics of light’ came to flourish: Plotinus and Proclus on the one hand, Philo and the Church Fathers, especially Augustine and Dionysius the Areopagite, on the other.¹³ Beierwaltes’s interpretation of Plotinian light imagery caused the emphatic reaction of Ferwerda, who argued that the dualistic premises of Platonic orthodoxy, of which Plotinus was a true disciple, necessitated a radical gap between the intelligible and the sensible realms. Such discontinuity precluded the possibility of any analogical language of light. Consequently, Plotinus’ use of light imagery in speaking about the higher realities was purely pedagogical, hence metaphorical, while Beierwaltes’s participatory ‘light metaphysics’ was an anachronistic eisegesis of the medieval theory of analogy, inspired by Baeumker and projected back onto ancient sources.¹⁴ Ferwerda’s argument may have shaken (though not destroyed) the credibility of Beierwaltes’s thesis as regards Plotinian scholarship.¹⁵ But it only helped reinforce Beierwaltes’s interpretation as regards the Augustinian tradition throughout the Middle Ages. Anyone interested in the analogical talk of God as light (and an alternative to Thomist Lichtmetaphorik) had only to look here for a safe heaven.¹⁶ Hence the fascination, in English scholarship, with Grosseteste under the borrowed label of the ‘metaphysics of light’. Clearly, there is something elusive in a debate that lasts over a century without reaching a conclusive result. A careful study of the major protagonists reveals a subtle but crucial detail. The recurring question in the aforementioned literature has not been the interpretation of Philo, Plotinus, Augustine, Dionysius, or Grosseteste as such. The real issue has been how these thinkers interpreted another text, namely Plato’s ‘sun-simile’ (together with the adjacent images of the ‘divided line’ and the ‘cave’), and its reception history. The real debate, then, has been about the history of interpretation of the Platonic light language. If we now go back to the original source, it is easy to see that the Platonic text is itself responsible for its ambivalent reception through the centuries. In his speech to ¹³ For the reception history see Beierwaltes (1980a), 282–5. ¹⁴ See Ferwerda (1965), 2–7, 46–9, 57–61. ¹⁵ See Emilsson (2007), 8–9: light as one of many ‘emanative metaphors’. But cf. Lloyd (1990), 100: light is not a ‘mere analogy or metaphor’, but one of many ‘examples of the physical model of emanation’. ¹⁶ It should be noted, however, that Thomas’s considered view is much more nuanced than occasionally presented, implying a distinction between ‘sensible light’, which is used metaphorically with regard to God (like the ‘sun simile’), and ‘intelligible light’, which is predicated properly with regard to intelligible beings and analogically with regard to God, see Whidden (2014), 71–86. One may remark, with McEvoy (1978), 141, that Thomas recovered, in the end, much of the ‘metaphysics of light’ of the Platonist tradition ‘in categories that were different, largely original and less ambiguous than those he rejected’.

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Glaucon, Socrates introduces the sun as an analogon of the Good (tagathon), in the sense that ‘whatever the Good is in the intelligible realm, in relation to the intellect and intelligible things, the same is the sun in the visible realm, in relation to sight and visible things’ (508b13–c2). Socrates then goes on to explain the analogy in terms of a simile (hōsper . . . houtōi 509a1–5) but he also says that the sun is the image (eikona) of the Good (509a9), exhibiting a relation of similarity (homoiotēta) to it (509c6). The perennial question in Western light hermeneutics has been, precisely, the meaning of the sun as an analogon of the Good. The constant challenge has been how to disentangle two different senses of ‘analogy’, analogy of language and analogy of being. Behind the distinction hides one of the most fascinating questions in the history of Western philosophy: the relation between being and language. For instance, if one were to approach the analogy of the sun as a solution to the paradox of talking meaningfully from within language about the Good that lies ‘beyond being’ (epekeina tēs ousias), and thus beyond the predicative ability of human language, one would have to take seriously the hōsper (‘just like’) clause and conclude that Plato’s celebrated light imagery (or any other light imagery with a transcendent referent) is a clear-cut case of figurative speech, a veritable simile in the sense of the classical theory of metaphor.¹⁷ If one were to approach the analogy of the sun, however, as an illustration of Platonic participatory metaphysics (‘theory of forms’), one would need to take seriously the predicative function of the Platonic ‘image’ (eikōn) as a type–token relation that links causally different modes of being and conclude that the sun is the sensible copy of a supra-intelligible archetype that Plato calls ‘the Good’. Even though Plato’s light imagery—in its effort to express through language what escapes ordinary language—remains a simile, the sensible object that functions as the ground of the simile (i.e. the sun) is itself causally dependent on the semantic target that it aims to explain (i.e. the Good). In other words, in Plato’s metaphysical universe the sun does not merely illustrate, as a figure of speech, the function of the Good. The sun is what it is, irrespective of any simile, because of the Good. As G.E.R. Lloyd puts it in his monumental study Polarity and Analogy, not all types of Platonic ‘metaphors’ are empty figures of speech.¹⁸ The ‘sun simile’ contains an analogical argument as ‘an important means not merely of instructing the pupil, but also of discovering and intuiting the truth’.¹⁹ It is one of those ‘true and significant analogies’, which are ‘not a mere coincidence, but rather, it seems, the result of a sort of divine guidance’.²⁰ With these thoughts in mind, and after a century of debates, it is possible to draw an irenic conclusion. The ‘metaphysics of light’ is a term with a precise reference (the talk of the divine as ‘light’) and an ¹⁷ On the classical theory of metaphor see Aristotle, Poet. 21; Rhet. III.2–4; Cicero, Orat. II.45 (261–2); Quintilian, Institutio oratoria VIII.6–IX.1. See further Soskice (1985), 3–10; Innes (2003); Hills (2017). On Aristotle’s own metaphorical interpretation of the Platonic light imagery see De an. III.5 (430a14–17): the active intellect is ‘like the light’ (hoion to phōs). ¹⁸ See Lloyd (1966), 226. ¹⁹ Lloyd (1966), 402. ²⁰ Lloyd (1966), 402.

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elusive meaning. Its elusiveness is the result of the peculiar mixture of metaphorical language with participatory metaphysics in the central books of Plato’s Republic. Much of Western light imagery can be traced back to this text.²¹ To this extent, the quest for the ‘metaphysics of light’ is the quest for the role and meaning of Platonic metaphysics in the Western intellectual tradition.

0.2 What This Book Aims to Achieve The aim of this book is not to rehearse the intellectual history of light imagery in Western thought, nor the history of Platonic metaphysics; neither does this book aim to explore the reception history of Plato’s ‘sun simile’; nor to revisit the question of metaphor and analogy. This book has the modest aspiration of revisiting only a tiny part of the intellectual tradition that has been classified under this or that model of the ‘metaphysics of light’, namely the Jewish-Christian metaphysical tradition of the early Church, and then again only one episode in the context of this tradition, which is, as we know today, extremely rich and diverse in its expressions. The episode I have in mind focuses on the so-called ‘Alexandrian tradition’ and its Cappadocian interpretation, and has Philo of Alexandria, Origen, Basil of Caesarea, and Gregory of Nyssa as its main protagonists. There are a few significant reasons for this choice. As we have already seen, Philo is the point of contention between Baeumker or Beierwaltes, who place him at the head of the participatory metaphysics of later Platonism and its analogical light language, and Klein, who pushes the point that metaphorical language is the only one adequate to express absolute divine transcendence. At the same time, Philo is at the head of a metaphysical tradition, which, through the catechetical school of Alexandria, reached down to Origen and, through an Origenian line of transmission via Gregory Thaumaturgus and Macrina the Older, became a major source of inspiration for the Cappadocian school of thought.²² Philo, Origen, and the Cappadocians exercised tremendous influence in the history of early Christian thought. In the West, they were the great sources of inspiration for Ambrose, who initiated Augustine into the deeper meaning of Scripture.²³ Similarly, in the East, the unknown Syrian author writing at the turn of the fifth and sixth centuries under the literary name of Dionysius the Areopagite is highly indebted to the

²¹ See McKeon (1948), 157; Lindberg (1976), 95. ²² For the ‘Alexandrian tradition’ in its line of continuity from Philo to Origen see Runia (2015). For the Philonic legacy of the catechetical school see van den Hoek (1997); for the patristic tradition see Runia (1993) and (2014). On the line of continuity between Origen, Basil, and Gregory see Ramelli (2007) and (2013), 372–440. For the Origenian legacy as part of the intellectual inheritance of Basil’s and Gregory’s family see Rousseau (1994), 11–14; Silvas (2008). ²³ On Ambrose’s debt to Philo, Origen, and Basil for his scriptural exegesis see Ramsey (1997), 67. As regards his hexaemeral homilies see Henke (2000), 17–29.

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Alexandrian and the Cappadocian schools for his doctrine of illumination.²⁴ But it is the short treatise on Mystical Theology, with its celebrated imagery of ‘divine darkness’, that has contributed most to the author’s legacy as the mystical theologian par excellence. The treatise is based on the theme of Moses’ mystical ascent, which the author could not have developed in this way were he not deeply acquainted with the works of Philo and Nyssen on the Life of Moses.²⁵ In drawing a line of succession from Philo to Gregory, I aim to investigate the formative period of the Christian ‘metaphysics of light’, so much so that my three main protagonists, namely Origen, Basil, and Gregory, have been, strikingly, entirely neglected by the previous discussion. In bringing them into focus, I aim to fill in a gap in current scholarship. In doing so, some of what we thought we knew about late antique ‘light metaphysics’ might shine under a different light.

0.3 Old Wine in New Skins: From Light Language to the Concept of Light 0.3.1 Boyancé’s Challenge In his review of Klein’s monograph, the French classicist Pierre Boyancé remarked that Klein had neglected to take into account the physical theories that supported and further explained Philo’s light metaphors and ‘light metaphysics’.²⁶ Take, as an example, the case of a purely metaphorical use of language. Boyancé argued that, according to the classical metaphor theory, the structure of a simile consists of the transfer of meaning (i.e. of a semantic property) from a source domain to a target domain, establishing a relation of similarity between the two. In the case of light metaphors, the source domain is physical light and the target domain is an intelligible agent or object (like the divine intellect or the intelligible world). In order to understand the meaning of ‘light’ as divine predicate in Philo and the philosophical literature he represents, we need to know which properties of light the author had in mind in each particular context. This requires an investigation into the physics of light that explained these properties. Boyancé rightly complained that Klein never conducted such an investigation. His was a serious accusation. If it is true that the Philonic use of light imagery is entirely metaphorical, as Klein argued, it is especially dire that Klein’s research never investigated the ground of meaning of Philo’s light language. Boyancé’s complaint can be generalized. With few notable exceptions, the debate on the ‘metaphysics of

²⁴ See Louth (1989), 40.

²⁵ See Louth (1989), 100–1.

²⁶ See Boyancé (1963).

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light’ did not touch upon the physical theories that ground the meaning of the language of God as light.²⁷ One might retort that Boyancé’s objection applies only to the metaphorical interpretation of light images (Lichtmetaphorik). It does not apply, however, to their analogical interpretation (Lichtmetaphysik), according to which there is no transference of meaning from the physical world to the divine reality. The followers of the latter interpretation might feel that Boyancé’s critique misses the mark, since, on this reading of the sources, the language of divine light is logically prior to the language of physical light, in the sense that the term ‘light’ has its proper and primary significance with reference to God.²⁸ This is an important point that modern scholars think was also advocated by pro-Nicene theologians, such as Athanasius, Basil, and Gregory of Nyssa.²⁹ If so, the heroes of the Nicene faith would be major exponents of the Christian ‘metaphysics of light’ in its analogical interpretation. Nevertheless, it is a moot point. We have no clue what divine predicates such as ‘light’ (or ‘father’, ‘creator’ etc.) might mean if we do not start from familiar semantic contexts in which the words already have meaning. That is precisely the point of the Platonic analogy of the sun, whose aim it is to help the reader intuit something of the unfamiliar meaning of goodness itself (auto agathon 507b; epekeina tēs ousias 509b) by comparison to something known to the senses and a commonly shared experience of goodness. The analogy of the sun proposes, as such, an experience of the self-communicating nature of heavenly fire, which illuminates the earth through its light and sustains life through its warmth. The ‘metaphysician of light’ may here retort that the philosopher who has attained direct contemplation of goodness itself has no need for analogical reasoning, apart from pedagogical purposes. The same is true for the scriptural equivalent of the Platonic philosophical vision, whether in the sense of Moses’ theophanic experience of the burning bush on Mount Sinai or in the sense of the

²⁷ The exceptions I have in mind are the studies of Boyancé (1936), 65–78, for Stoicism; Schroeder (1981), (1984), and (1992), 24–39, for Alexander of Aphrodisias and Plotinus; Lindberg (1986), 9–29, for Neoplatonism; Nikiprowetzky (1989, unfinished draft), for Philo; van Kooten (2005a), for the Johannine literature. To be clear, Boyancé’s objection holds only for the meaning of light metaphors in the tradition of philosophical theology which translates theological language into metaphysical categories, the study of which builds directly on ancient physics (or is inseparable from it, as is the case in sources of Stoic inspiration). It does not hold for the lay understanding of the language of God as light nor for how this language was further unpacked in the broader literary context of antiquity. The Philonic corpus is an exemplary case of philosophical theology of the aforementioned style, bequeathed to early Christianity through an Alexandrian legacy, see Schneider (1999); Kobusch (2006); Karamanolis (2013). ²⁸ I am here referring to the school of Baeumker and Beierwaltes, which emphatically denies the transference of properties from physical to divine light, see Beierwaltes (1980b), 289: ‘The cause and ground of all being is “true”, “real” light, whose “image” is the sensible light—not the other way around.’ ²⁹ For Athanasius and Gregory see Osborne (1993), 158–61; for Basil see Radde-Gallwitz (2009), 114–22, and DelCogliano (2010), 158–63.

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disciples’ mystical experience of the light of transfiguration on Mount Tabor.³⁰ Yet to understand the language of divine light only by direct theophanic knowledge is an extremely high bar for the average scriptural (or Platonic) reader who has not yet attained that experience and genuinely wants to learn about it. Indirect knowledge is necessary if divine predicates are to make sense in the first instance.³¹ Such indirect knowledge can only be derived from experience known and familiar to the reader, i.e. in the case of light, from the reader’s acquaintance with the light of this world. It thus makes no difference whether we understand ‘light’ as divine predicate in a figurative (Lichtmetaphorik) or non-figurative sense (Lichtmetaphysik). In both senses, we need to unpack the meaning of the concept starting from our experience of physical light. To give a celebrated example of an early Christian use of light as divine predicate, think of the Nicene formula ‘light from light’: no matter how we understand its mode of language (figurative or proper), we still need to ground its meaning in the world of our direct and immediate knowledge. How does light generate light in the physical world? What are the physical properties of light that are theologically relevant? Boyancé’s objection holds regardless of the mode of language used in the sources. There is still a dire need to investigate the concept of physical light in early Christian literature.³²

0.3.2 A Challenge Still Not Met The lack of interest in the early Christian theories of light is most evident in the camp of Lichtmetaphorik.³³ Studies which consider the light imagery to be more ³⁰ For the Platonic background to the scriptural theophanic language of light see the remarkable paper of van Kooten (2005a), with further references to the modern and ancient sources. ³¹ But also in the last instance, if claims about theophanic experience are to be verified through rational discourse, as they are in the Platonic corpus, and as they ought to be in general. ³² I here assume that the meaning of the language of ‘God as light’ presupposes a notion or concept of light underlying such language. What I mean is this: when a term (‘light’) is used not as a name (X) but to indicate some feature or property (Y) of the bearer of a name, so that bearer and property stand in a predicative ‘X is Y’ relation, such as ‘God is light’, the term signifies something other than the bearer to which it applies. It signifies a feature or description which may or may not be true of the bearer, see Osborne (1993), 159. The mental representation of that feature or description is the concept of Y. Light is such a concept. The concept of light entails theoretical knowledge that explains why certain things happen in the world, such as the illumination of a dark room, analysable in a set of properties and the causal and functional relations between these properties and the properties of entities represented by other concepts, such as a dark room. Let us here call concepts whose theoretical knowledge is reducible to abstractions about relations between variables, as in the case of the laws of physics, ‘scientific concepts’. Physical light is such a concept. For the reasons already mentioned, and which I further discuss in Chapter 2, the hexaemeral authors took seriously in their scriptural exegesis light as a scientific concept. The theoretical knowledge contained in scientific concepts may vary significantly in different scientific theories, shaping beliefs in different socio-cultural contexts. The theoretical knowledge that is part of the early Christian concept of light, then, requires an investigation into the laws of physics that are relevant to the early Christian theories of light. ³³ See for example the studies of Wallraff (2001); Kariatlis (2013); McConnell (2014).

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than a mere metaphor investigate further the ground of the analogical reasoning from light.³⁴ Yet they too forgo a systematic investigation of the early Christian physics of light, extrapolating some physical properties of light from the theological debates rather than examining the validity of the theological arguments invoked in the debates according to the physical properties of light that ground them. The lack of a thorough discussion of the ancient physics of light is also characteristic of a cluster of four seminal studies on the theological use of light language by the Cappadocians.³⁵ They significantly advance our understanding of the early Christian concept of light by showing that it is a physical power, which is logically construed as a proprium (see Chapter 2, section 2.3.2). If we ask, however, ‘physical power of what?’ or ‘proprium of what?’, the answer we get from these studies becomes blurry. In his landmark PhD dissertation on the notion of power in Gregory of Nyssa, Michel René Barnes at least once regards light, incisively, as a property of fire.³⁶ The recurring argument of the book, however, is that light for the Cappadocians is an example of power causality in which a cause reproduces itself (or its nature). Barnes thus treats the cause of light as being itself light ‘in exactly the same sense’ as its effect.³⁷ Although the premise is correct, it will be shown that Barnes’s conclusion is ultimately misleading: light as cause and light as effect do not have the same reference in ancient physics and that has direct consequences for the theological light language (see Chapter 3, section 3.3.3 and Appendix C). Something similar can be said about the brilliant studies of Andrew Radde-Gallwitz and Mark DelCogliano, which show that light as an inherent physical power is logically construed as a proprium. DelCogliano does not specify the physical substance of which light is a proprium. In general, he follows Barnes’s univocal interpretation of light in Basil’s writings³⁸ and seems at least once as bewildered as Barnes by Eunomius’ (actually correct) claim that light as cause and effect does not denote exactly the same thing.³⁹ Radde-Gallwitz goes a step further in the right direction. In his monograph he mentions, correctly, that light is the inherent power of fire⁴⁰ but then goes on to construe, misleadingly, ‘light’ together with other divine predicates such as ‘life’ and ‘goodness’ as ‘analogous to the propria of the elements’.⁴¹ He thus follows Barnes in considering heat (instead of heat and light) as the typical proprium of elemental fire.⁴² ³⁴ See the much-neglected but still best study available on the subject by Pelikan (1962), 21–36 (‘metaphor’ in the sense of a platonic paradeigma); 39–51 (the role of the doctrine of creation in the shaping of light language); 55–72 (history and development of the Nicene light language). See further the seminal studies of Theodorou (1976); Beck (1981); Hanson (1985); and McGuckin (1994), as well as the more recent studies of O’Collins (2012), who follows Pelikan, and Tanner (2012), who follows Prestige (1952). ³⁵ See Barnes (2001), Radde-Gallwitz (2009) and (2017), and DelCogliano (2010). ³⁶ See Barnes (2001), 159. ³⁷ See Barnes (2001), 119–21. ³⁸ See DelCogliano (2010), 163. ³⁹ See DelCogliano (2010), 159. ⁴⁰ See Radde-Gallwitz (2009), 160. ⁴¹ See Radde-Gallwitz (2009), 167 my italics. ⁴² See e.g. Radde-Gallwitz (2009), 163, 203 n.85.

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Similarly, in a seminal paper which further discusses light as a power and property in Basil’s Hexaemeron, he identifies, again correctly, light as a power and property of the sun,⁴³ but then goes on to distinguish the properties and powers of elemental substances from light as a property and power of the sun,⁴⁴ instead of regarding the sun as a particular instance of (elemental) heavenly fire. The aforementioned studies contribute only partially to decoding the meaning of (physical) light in early Christian literature, either because they identify the cause of light with its effect or because they identify light with a natural power or proprium without specifying adequately the source of light as power or proprium. In fact, this book will argue that the meaning of ‘light’ in early Christian literature is richer than that. In an influential study, Volker Henning Drecoll shows some traces of reflection on the Christian physics of light.⁴⁵ His claim that ‘light’ is a suitable theological predicate because of its ‘immateriality’⁴⁶ builds on a textually verifiable premise, which, however, does not mean immateriality in an ontological sense, as will be shown in Chapter 3. In a fascinating footnote, Drecoll alludes to precisely that (i.e. ‘light’, like pneuma, denotes ‘a finer substance’) but then, mistakenly, claims that in Basil ‘no clear distinction is carried out between the divine and the physical light’.⁴⁷ Finally, the paper of Adrian Marinescu is a valiant effort to enquire into Basil’s concept of light, but it unfortunately remains at a superficial level.⁴⁸ Thus, there is only one study that, to my knowledge, answers Boyancé’s objection from an early Christian perspective. In his remarkable book on the use of philosophy in early Christian theology, Christopher Stead unpacks the theological language of light in constant reference to ancient physics, most notably the Platonic and Stoic physics of fire and light.⁴⁹ But his is a book of heights and falls. The book offers only occasional, though valuable, remarks.⁵⁰ Crucially, the analysis is not always sound: as will be shown in Chapter 3, Stead’s assumption that fire in early Christian physics ‘need not involve combustion’ is false and so is his conclusion that fire was ‘an appropriate symbol for the divine nature, in that one can ignore its dependence on an exhaustible supply of fuel’.⁵¹ His assumption that in early Christian physics all material substances are composite is correct, but his conclusion that light cannot serve as a paradigm of simplicity is not.⁵² Last but not least, Stead shows an outspoken distrust in the cogency of early Christian philosophical analysis, leading to a somewhat biased assessment of the early Christian theology of light.⁵³ ⁴³ See Radde-Gallwitz (2017), 201, 210. ⁴⁴ See Radde-Gallwitz (2017), 211. ⁴⁵ See Drecoll (1996), 103–11. ⁴⁶ See Drecoll (1996), 103. ⁴⁷ See Drecoll (1996), 103 n.162. ⁴⁸ Confusing, for example, the nature of the medium with the nature of light, see Marinescu (2013), 87. ⁴⁹ See Stead (1994), esp. 46–7, 140–3. ⁵⁰ See Stead (1994), e.g. 71, 101, 156, 169, 170, 209–11, 225–6. ⁵¹ See Stead (1994), 141. ⁵² See Stead (1994), 132. ⁵³ See Stead (1994), e.g. 132.

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0.3.3 The Need for a Fresh Start This book begins with the basic assumption that the concept of physical light grounds the referential meaning and semantic context of the theological language of light in early Christian literature. To achieve its goal, this book remains intentionally agnostic as regards the mode (literal, analogical, or metaphorical) of the theological light language. Its aim is to shift focus from the language to its referent, from the sign to the signified, from ‘light’ as a divine predicate to the concept of light itself. In doing so, this book understands the quest for the ‘metaphysics of light’ differently than before. It is no longer interested in classical dilemmas of the sort ‘literal or metaphorical’, ‘figurative or non-figurative’, ‘proper or improper’ etc., which have been the focus of the ‘linguistic turn’ of the twentieth century and which have widely monopolized previous discussions. That is not to say that these are not still interesting and important questions to ask.⁵⁴ It is only to say that, unless we ask the logically prior question, there is little room left for novel contributions in this regard.⁵⁵ The logically prior question, which ancient readers had to ask before they decided how to read the scriptural references to light, literally or metaphorically, is the question: ‘what is light?’ The question is important for two reasons. First, it makes us immediately suspect that its answer is different for us today than it was fifteen hundred to two thousand years ago, which is the floruit of early Christian thinkers. Second, it helps us understand that until we have a better grasp of how early Christian thinkers conceptualized physical light, the full meaning of their theological light language will remain sealed to us, regardless of its literal or metaphorical use. Curiously, it is this question that has been omitted in the previous discussion. It is this question that is the subject matter of this book. Due to its novel research question, this book adopts a novel method. As a working hypothesis, it distinguishes at the outset between two different senses of the term ‘light’ in the locution ‘metaphysics of light’. In its traditional and extended sense, ‘light’ denotes ‘being qua being’, ‘pure being’, ‘being as such’, and the like, i.e. ‘being’ as the subject matter of traditional metaphysics in all its abstractness and generality. This is the sense used by Baeumker and Beierwaltes, which I will from now on refer to as the ‘metaphysics of light’ lato sensu. This is a stretched sense of ‘light’ because no matter how we unpack its meaning (literally or metaphorically), the term denotes something different than the common and familiar sense of the agent or state of physical illumination. By contrast, it is in the latter sense that I will from now on employ the term ‘light’ in this book. This is a

⁵⁴ Indeed, I discuss the traditional questions of the ‘metaphysics of light’ in two further studies that build on the argument of this book, see Katsos (2022) and Katsos (forthcoming). ⁵⁵ I hint at the possibility of such novel contributions throughout this book and especially in Appendix C.

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narrow sense, since ‘light’ retains its known and commonly available usage in ordinary language, as when we speak of ‘the light of the sun’ or ‘the light that illuminates a dark room’. This ordinary meaning of ‘light’ is different from its extended meaning. It no longer refers to the whole of reality but only to a part of it, namely the natural process, condition, or event that we phenomenologically attest as making things visible. If we now ask what this process, condition, or event is, we open up two different but interrelated fields of enquiry, depending on what we mean by the question. If we mean how light manifests in the visible world, we enquire into the phenomenal aspect of light and enter the domain of the physics of light. If we mean why light manifests the way it does, we enquire into the noumenal aspect of light, i.e. into the nature (ousia, phusis) and explanatory cause (aition) of light and enter the domain of the metaphysics of light. I here speak of the metaphysics of light in a narrow sense (stricto sensu) and without inverted commas, which I distinguish from the traditional ‘metaphysics of light’ in an extended sense (lato sensu), hence in inverted commas. In a narrow sense then, the metaphysics of light no longer denotes the traditional subject matter of metaphysics, i.e. ‘being qua being’ or ‘being as such’, but only one kind of being, i.e. ‘light qua being’ or ‘light as such’. Only in the latter sense is the metaphysics of light the subject matter of this book. This redefinition of the subject matter is necessary in order to move beyond the linguistic barrier of previous discussions. In the end, the working distinction may prove somewhat artificial because the nature of light reveals the nature of being in an exemplary way. At the starting point of our enquiry, however, we do not know yet whether it is so. Any a priori identification of light with being comes at the expense of a petitio principii. For the purposes of our enquiry, then, the distinction between the nature of light and the nature of being is methodologically necessary, even if it proves to be no more than a useful tool that we might need to let go of in the end. Only after the nature of physical light has been clarified (the metaphysics of light in its narrow sense) can one enquire further into the meaning of light as a theological concept (the ‘metaphysics of light’ in an extended sense). The purpose of this book is therefore to redirect attention to the question ‘what is light?’ and, in doing so, to investigate the concept of physical light in early Christian literature. Yet this is not as straightforward as it seems. The major obstacle that this book has to overcome is the absence of a systematic study on the ancient physics of light. What this means and why this gap exists are thoroughly explored in Chapter 1. I there discuss the current trend of approaching ancient theories of light from a purely ‘oculocentric’ perspective, as parts of ancient theories of vision. I show why this is not the only way to read the texts and I argue that it is actually the wrong way of reading Jewish-Christian sources. Thus, the first chapter of this study is devoted to the task of rediscovering the path that leads to the ancient physics of light—a path that is blocked by modern historiography. The second challenge that this book has to overcome is to show

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that this path is important for scriptural reasoning, and hence theologically relevant. It is one thing to show that there exists an ancient physics of light; it is another thing to show that Jewish-Christian thinkers developed their own version thereof; and it is altogether another thing to argue that the Jewish-Christian physics of light is hermeneutically significant. For this reason, in Chapter 2 of this study I discuss various objections raised to the compatibility of the ‘logic’ of Scripture with scientific rationalism. This chapter argues that binary distinctions like ‘Scripture vs. science’, ‘faith vs. reason’ etc. stem from anachronistic or uncharitable readings of the sources. The connection between Scripture and premodern science is found in the early Church doctrine of the logos. It is through the logos doctrine that the physics of light acquires a genuinely hermeneutical, hence theological, import. With the above caveats and contentions, Chapter 3 embarks on the investigation of the nature of light from the perspective of early Jewish-Christian sources. I here collect all the clues given in the texts, I discuss them from the backdrop of the major theories of light available at the time, and I reconstruct the outlines of a systematic theory of light as it would appear roughly in the timeframe between the Council of Nicaea (325) and the Council of Constantinople (381). My reconstruction shows that, irrespective of the question of language, the reconstructed theory comes with specific ontological commitments which are derived from a certain reading of Scripture. It thus presupposes a hermeneutically grounded metaphysics of light in the narrow sense. The basic source material for an enquiry into the concept of physical light of the early Church is found in the so-called ‘hexaemeral’ tradition, i.e. the collection of commentaries, homilies, and special treatises concerned with the exegesis of the biblical creation narrative of Genesis 1.⁵⁶ The earliest extant commentary is Philo’s treatise De opificio mundi, though Philo was certainly not the first to produce a hexaemeral exegesis.⁵⁷ His work, however, has exercised tremendous influence (directly or indirectly) over the subsequent tradition, giving rise to a body of literature that exhibits a certain structural and thematic unity. It is only in the latter sense that this book speaks, somewhat indiscriminately, of a ‘JewishChristian’ hexaemeral tradition, in order to stress the lines of continuity behind the indisputable exegetical variety.⁵⁸ As will become clear, it is the hermeneutical interplay of diversity and continuity that yields the particular theological import ⁵⁶ For a heuristic definition of the hexaemeral literature see Robbins (1912), 1. For a list of the hexaemeral sources see Congar (1964), 215–22. The best overview of the field is given by van Winden (1988). The most comprehensive study is that of Köckert (2009). For cross-cultural treatment of the hexaemeral exegesis see the collection of papers in Centre d’études des religions du livre (1973). For the influence of the hexaemeral literature in the history of art see Zahlten (1979). ⁵⁷ On the literary context of Philo’s hexaemeral exegesis see Tobin (1983); Runia (2001), 19–20, 30–2; Matusova (2010); and the collection of papers in Seland (2014). ⁵⁸ On the exegetical unity-in-diversity of the hexaemeral tradition see the thematic overviews of Wallace-Hadrill (1968); Bouteneff (2008); Bright (2008); Louth (2009); Allert (2018). For a systematic perspective see Young (2013), 44–91. These studies document a gradual shift in patristic scholarship towards a greater appreciation of the scientific and philosophical sensitivity of the hexaemeral authors.

16



of the hexaemeral physics of light. To retrieve this hermeneutical interplay, this study engages in a close reading of the hexaemeral texts. My effort has been to use existing and easily accessible translations, even though in many cases they had to be (more or less) modified for the sake of a more accurate reading.⁵⁹ In a few cases, an entirely new translation had to be produced.⁶⁰

⁵⁹ For extended passages from Gregory’s Apology, I have used (slightly) modified or (significantly) amended versions of a widely circulating paraphrasis produced by Casimir/Richard McCambly, available at https://www.lectio-divina.org/images/nyssa/Hexaemeron.pdf. After the completion of the manuscript of this book there appeared the translation of Robin Orton, On the Six Days of Creation (Catholic University of America Press, 2021), while another translation is being prepared by Andrew Radde-Gallwitz for the Early Christian Writings Series of Cambridge University Press. Regrettably, it was no longer possible to take the above translations into consideration. ⁶⁰ Unless otherwise indicated, the translations provided are my own.

1 ‘From Sight to Light’ A Hexaemeral Guide for the Perplexed

The angels were made before heaven. Heaven and everything below were made afterwards. The angels, then, stood by at creation. Heaven was fixed, the angels were praising. Because they did not see themselves being made, they marvelled as heaven was made. They were seeing the sun being kindled, the moon bringing light, the stars being made, and they were astonished. For God tells Job: “When I made the stars, all of my angels sang my praises” [Job 38:7]. (Ad Gen. 1:1 from the Catenae) This book begins with the basic contention that illumination is perceived as a change in the world. If, after Aristotle, physics is the study of change and the things that are subject to change (Phys. I.2, 185a12–13), physics holds the key to answering the question: ‘what is light?’ The physics of light would be the part of physics that studies illumination as a change in the natural world, while the history of the physics of light would be the kind of enquiry that answers the question: ‘what is light?’ in a historical context. Early Christian philosophical theology offers such a context. The ancient physics of light would, therefore, hold the key to answering the question: ‘what is light?’ in an early Christian context. A closer acquaintance with the history of science, however, reveals that it may not be so simple to take the ancient physics of light as a starting point for enquiry into early Christian sources. The starting point assumes that there is such a thing as an ancient ‘physics of light’. Yet this is extremely contentious in the contemporary history of science. According to one school of thought, light was the proper object of enquiry in premodern physics. Ancient theories of light were, therefore, early intimations of modern optics in the sense of a proper ‘physics of light’. According to another school of thought, the object of enquiry of premodern optics was sight, not light. This approach understands the passage from premodern to modern optics as the passage ‘from sight to light’ in the sense of a paradigm shift. The paradigm shift does not allow us to speak meaningfully of a premodern ‘physics of light’, certainly not in the way that we use the term today. What is at stake is the possibility of a premodern discourse on the nature of light. Simply put, the question is whether the ancient sources are able to theorize light as an autonomous subject of change, an autonomous physical agent in the world.

The Metaphysics of Light in the Hexaemeral Literature: From Philo of Alexandria to Gregory of Nyssa. Isidoros C. Katsos, Oxford University Press. © Isidoros C. Katsos 2023. DOI: 10.1093/oso/9780192869197.003.0002

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The question becomes particularly pressing once we realize that the early Christian theological language of light is deeply rooted in biblical hermeneutics.¹ If we follow the first approach, it is possible to speak of a premodern ‘physics of light’ and hence enquire about its biblical version, starting with the interpretation of Gen. 1:3–5. If we follow the second approach, there is no ancient theory of light independent of a theory of vision. This complicates things from a biblical perspective since the biblical text does not mention any spectators of the first light of creation other than God: ‘And God saw the light, that it was good’ (Gen. 1:4). But should we understand this vision of God in a physical sense? This chapter aims to address the preliminary question whether it is possible to speak of a genuine physics of light in hexaemeral literature. This invites us to link the hexaemeral sources with contemporary questions raised in the history of science, more specifically in the history of optics as the scientific discipline interested in the study of light. In what follows, I shall argue that hexaemeral light is part of the late antique physics of light. My argument is going to be dialectical in the sense that I am not going to refute the optical paradigm as irrelevant to the sources. Instead, I am going to show that it has been mistakenly interpreted as subordinating light to sight when, in fact, it is the other way around. In pursuing my argument, I shall situate ancient theories of light within the framework of hexaemeral hermeneutics. I aim to show that the hexaemeral physics of light as part of a comprehensive theological project does not exhaust itself with the study of the physical world. Much more than that, it aims to guide the reader of the biblical creation narrative from the phenomenal world to the world of intelligible causes.

1.1 The Intelligibility of Hexaemeral Light Scripture begins with a thought experiment: In the beginning God made the heaven and the earth. Yet the earth was invisible and unformed, and darkness was upon the abyss; and the spirit of God was hovering over the water. And God said, ‘Let there be light’; and there was light. And God saw the light that it was good; and God separated between the light and the darkness. And God called the light Day, and the darkness he called Night. And there was evening and there was morning, day one. (Gen. 1:1–5)²

¹ For a thorough discussion of the biblical grounding of the Nicene theology of light see Pelikan (1962). ² I here quote Gen. 1:1–5 from the Septuagint, which was the text considered canonical by the hexaemeral authors. Since most modern translations of Genesis 1 rely on the Masoretic text, I provide my own English translation of the Septuagint text after consulting the translations of Brenton (1844); Louth (2001); Brayford (2007); and Hiebert (2007). Brayford and Hiebert translate the gi(g)nomai

    

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The opening chapter of the book of Genesis invites the reader to go back to the beginning of time (en archē) and visualize the universe in its early, still ‘unformed’ (akataskeuastos) state. The story narrates the formation of the universe in several cosmic periods: ‘six days’, hexi hēmerai, whence ‘hexaemeron’, denoting synecdochically—together with the seventh day of the Sabbath, to which later the Christian eighth day of the Lord was added—the whole of God’s creative work. ‘Heaven and earth’ were created first, but the earth was ‘invisible’ (aoratos) since there was no light. Then a speech act happened, a luminous epiphany of a divine command: ‘And God said: “Let there be light”; and there was light.’ The narrative continues with the reader visualizing God seeing the light, acknowledging that it was good, and dividing light from darkness. Thereupon the measurement of time appeared, ‘day’ and ‘night’, revealing a pattern of regularity of succession, ‘evening’ and ‘morning’. That was ‘day one’ (hēmera mia), the first stage of the new-born universe. There are several hints in the biblical account of the cosmogenesis that there is more to the narrative than first meets the eye. The perspective is clearly geocentric, as the measurement of time in days and nights betrays—a bizarre choice if the intended perspective is the point of view of God. And there are signs that the narrative might be more sophisticated than it initially appears. If measured time begins with the first divine speech act—fiat lux—that set creation in motion, what is the state and nature of the pristine cosmic elements: ‘heaven’, ‘earth’, ‘spirit’, and ‘water’? Which of our cosmological categories best befits the biblical notion of the ‘abyss’? Why does the earth subsist in the beginning alone and ‘unformed’, while all the stars and planets were created much later and fully adorned? And why is it that only the earth is invisible and not both heaven and earth? The biblical narrative begins with the cosmogenesis, and a storm of thoughts blows through the mind of the contemporary reader. In this confusing state, only one narrative element sounds familiar and recognizable, an element with which even a lay newcomer to this strange new biblical world can relate: ‘light’—pure natural, physical light. Yet again, the sense of familiarity vanishes once we read more closely. If ‘heaven and earth’, the ‘spirit’, the ‘water’, and the ‘abyss’ do not match, prima vista, our known cosmological categories, why should ‘light’? If there was nothing ‘out there’ apart from some strange dark cosmic ‘stuff ’—viz. the invisible and unformed ‘earth’ etc.—where did light come from? Moreover, we are told, ‘God saw the light that it was good’ (kai eiden ho theos to phōs hoti kalon, Gen. 1:4).³

clauses of Gen. 1:3a, 1:3b, and 1:5b with ‘to come into being’. This leads to the correct but rather unusual translation of Gen. 1:3a as ‘let light come into being’. I have therefore opted for the also correct but more familiar translation ‘let there be’ and carried this choice through all the gignomai clauses. ³ The Septuagint text concurs with the Hebrew text, in which ‘the light’ (‫ ֶאת־ָה ֖אֹור‬et haor) is the object of the verb ‘saw’ (wa–yar); see Alexandre (1988), 92. The same syntactical order is also preserved in the Vulgata: Et vidit Deus lucem quod esset bona. But it is usually concealed in modern translations: ‘And God saw that the light was good’ (ESV).

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Surely this is a figure of speech unless God has a body and sense organs and can see. If God’s vision is meant metaphorically, why should the object of this vision—viz. light—be understood literally? Or perhaps God’s vision of light is not a metaphor and God does indeed have some kind of strange visual apparatus. Why should then this light that God saw be less strange than the eye that contemplated it? Why assume that an awkward, if literal, divine vision has as its subject matter a less awkward, literal, light? Just a little bit of reflection on one of the most widely cited biblical commonplaces—fiat lux—and neither the fiat nor the lux is as innocuous as a naïve cosmological narrative would suggest. No wonder then that the interpretation of the first chapter of Genesis, especially the opening verses, has been hugely debated since antiquity.⁴ Anything but perspicuous itself, the first light is paradoxically meant to illuminate everything else. If so, God works in mysterious ways indeed. Or perhaps the light of Genesis is simply what it says it is, namely physical light, and it does what it says it does, namely to illuminate, but we do not yet have the right eyes to see. If one thing is clear, the question of the nature of this ‘light’ cannot be settled by the biblical text alone. It also requires an act of interpretative decision. Basil, who has been extremely influential in the patristic tradition, describes, colourfully, in his hexaemeral homilies the interpretative crux of the biblical exegete: I know the laws of allegory although I did not invent them of myself, but have met them in the works of others. Those who do not admit the common meaning of the Scriptures say that water is not water, but some other nature, and they explain a plant and a fish according to their opinion. They describe also the production of reptiles and wild animals, changing it according to their own notions, just like the dream interpreters, who interpret for their own ends the appearances seen in their dreams. When I hear “grass,” I think of grass, and in the same manner I understand everything as it is said, a plant, a fish, a wild animal, and an ox. . . . Shall I rather give glory to Him who has not kept our mind occupied with vanities but has ordained that all things be written for the edification and guidance of our souls? This is a thing of which they seem to me to have been unaware, who have attempted by false arguments and allegorical interpretations to bestow on the Scriptures a dignity of their own imagining. But, theirs is the attitude of one who considers himself wiser than the revelations of the Spirit and introduces his own ideas in pretence of an explanation. Therefore, let it be understood as it has been written. (Hex. IX.1 GCS 146.11–147.23 tr. Way)

It is clear from Basil’s militant report that the literal reading of the first chapter of Genesis was not at all evident to ancient readers—just as it ought not to be to the ⁴ In understanding these debates, we owe a lot to the work of Jacobus van Winden; see the collection of essays in den Boeft and Runia (1997), 1–157.

    

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reflective contemporary readers.⁵ Basil opts in this context for a literal reading.⁶ ‘Grass’ is grass, he says in the ninth homily, and ‘fish’ is fish. So, too, ‘water’ is water and ‘light’ is light, i.e. pure natural, physical light, as he makes clear in his second (II.4) and third (III.6, 9) homilies. Many Church Fathers, like most biblical scholars today, made the same interpretative choice as Basil and understood ‘light’ literally.⁷ Given the aforementioned aporiai that the text generates, the literal interpretation is not the easiest route to take. Augustine initially thought it an impossible task. He then tried and, admittedly, failed. Later, he tried again, and it took him fifteen years to come up with an interpretation that would hardly comply with modern standards of literal exegesis. It remained an attempt ad litteram, ‘according to the letter’.⁸ Nevertheless, the literal interpretation is perhaps the safest way into the biblical text. In the end, if ‘light’ is not light, there is little left to make sense at all of the opening verses of the Bible. This study too adopts as its starting point Basil’s basic assumption that the reference of the biblical ‫–אֹור‬phōs–lux of Gen. 1:3–5 is physical light. The question is: whose physical light? Clearly, for Basil phōs is what Basil took physical light to be. Similarly, for us phōs is our notion of physical light. I would here like to be able to add effortlessly that Basil’s concept of light is the same as ours. But that might not be so easy as it sounds after sixteen centuries of scientific progress. Surely there have been significant changes in how scientists theorize the physical world—recall only the change caused by the use of the telescope—and the mere logical assertion that ‘light’ is light will not do. ‘Hesperus’ is Hesperus (i.e. the ‘evening star’) and ‘Phosphorus’ is Phosphorus (i.e. the ‘morning star’). As we know today, the evening star is the morning star, namely the planet Venus. But people were not always aware that the two names have the same referent. At the time of Basil, the memory was still alive of the evening and the morning star being considered as different heavenly bodies.⁹ Or, to take another trivial example, ‘atoms’ are atoms. But ‘atoms’ in ancient physics occupied the place of elementary particles, while in modern physics the place of elementary particles is occupied by other subatomic ⁵ For a very good discussion of the different interpretative approaches to Genesis 1–3 see Bouteneff (2008). On the intelligibility and inner dynamics of the allegorical approach see the stimulating study of Dawson (1992). ⁶ On Basil’s ambivalent stance towards the allegorical interpretation of Genesis and the context of its rejection in the hexaemeral homilies see Lim (1990); Hildebrand (2007), 122–39; Bouteneff (2008), 126–31, 171–2; Köckert (2009), 384–91; Rasmussen (2019), 71–80. As Drecoll (2017), 97–104, has convincingly argued, however, Basil’s rejection of allegory should not be misunderstood as a rejection of the deeper sense of Scripture. On the contrary, Basil explored the hidden sense of the hexaemeral narrative by a close reading of the biblical text; see Chapter 2, section 2.2.3 below. ⁷ See the evidence in Alexandre (1988), 91. ⁸ For Augustine’s various attempts at a hexaemeral exegesis and the different levels of interpretation involved see Chaffey (2011), esp. 89–91. ⁹ See Ibycus fr. 331 Loeb/P.M.G.(= 42,43 Bergk), according to a scholiast on Basil, In Genesim (Anecd. Oxon. vol. III 413.15–17 Cramer); Achilles, De universo 17 (Di Maria 24.14–16 = Maass 43.25–7). Cf. also Euripides, Melanippe fr. 486 Nauck, quoted by Aristotle, EN 1129b (slightly altered) and, through a different source, by Plotinus, Enn. I.6.4.12.

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structures (‘fermions’ and ‘bosons’). The same term (‘atom’) has lost its previous theoretical content (elementary particle) resulting in a different concept. Why should we assume otherwise in the case of light? The examples show that one should be wary of projecting one’s own familiar concepts back into the ancient sources. The history of science teaches us that the theoretical content, even the object of scientific concepts, may fluctuate between different scientific communities and change over time. It is not to be excluded that Moses or Basil, or any premodern reader of Scripture for that matter, understood something entirely or partially different than we do today when they thought of the word ‘light’. That is the reason why my first task is to lay out the assumptions under which premodern biblical exegetes conceptualized physical light. Whether ‘light’ signifies the same thing in ancient and modern physics is in fact a disputed question. In what follows, I will situate hexaemeral literature in the context of this controversy and draw the necessary conclusions for the hexaemeral theories of light.

1.2 The Oculocentric Thesis The question of the nature of light occupies the central stage in the contemporary history of science. Significant milestones of twentieth-century historiography have been the groundbreaking, but contested, work of Vasco Ronchi, Storia della luce,¹⁰ and David Lindberg’s authoritative work Theories of Vision from Al-Kindi to Kepler.¹¹ They both established the contours of the field that is now recognized as ‘history of optics’. Both works bequeathed to younger generations of scholars a hidden tension: on the one hand, they recognized the centrality of the question of light; on the other hand, they skewed the question by shifting focus from light to sight. It is still instructive to remember how this shift occurred. Ronchi began his historical survey with a theologian’s approach: the biblical account of the creation of light. Ronchi did not make any reference to the great Jewish-Christian hexaemeral tradition. But his remarks sound like a modern version of a hexaemeral commentary on primordial light. The first verses of Genesis entail, for Ronchi, ‘a theory on the nature of light’, according to which light has ‘an existence of its own, independent of its source and of its receiver’.¹² Since the hexaemeral tradition remained elusive, if not unknown, to Ronchi he did not have the necessary material to pursue the Genesis lead further. In trying to unfold the story of light, he was left only with ancient Greek theories of light to work with. If Ronchi had paused right there, the purpose of my study would have been very simple: to compare Ronchi’s account of Greek theories of light with the respective hexaemeral theories and continue the story that Ronchi left untold, as ¹⁰ Ronchi (1970) [all citations are from the English translation]. ¹² Ronchi (1970), 2.

¹¹ Lindberg (1976).

  

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the reception history of Greek theories of light by late antique biblical exegetes. But at this point Ronchi’s narrative took a rather unexpected turn, expressed in the following astonishing remark: The Greek philosophers do not appear to have taken upon themselves the task of determining the nature of light. What interested them most was to explain the mechanism of vision. In those days the main goal of thinkers was to learn to understand man, his functions and his faculties. Vision was one of the important faculties of man, and hence the answer to the question “how do we see?” became fundamental. Every physical entity exists because it produces effects. At that time the only known effect of light was vision, and it was natural therefore, that the study of light should begin from this point.¹³

For Ronchi, who at this point has been influential for all subsequent discussion, Greek thought did not ask the question: what is light? Instead, it asked the question: what is sight? This shift in the object of enquiry, sight instead of light, was, for Ronchi, empirically attested: that is what we get from the known sources. One may wonder whether Ronchi would be willing to reconsider if he were shown different textual evidence. Be it as it may, with him started a process of assimilation between the history of light and sight in modern historiography, a process through which the story of light became an integral part of the story of vision down to the seventeenth century. Lindberg was one of Ronchi’s severest critics. He bemoaned, amongst other things, the fact that Ronchi emphasized light over sight.¹⁴ Given the fact that Ronchi in the end did not follow the path of an independent enquiry into the nature of light, but subordinated it to the study of visual theories, Lindberg’s critique sounds, retrospectively, a bit overzealous. After all, Lindberg, too, acknowledged light as a possible field of independent historical study, but followed, in the end, the visual path inaugurated by Ronchi: Before 1600 the science of optics tended to coalesce around two interrelated, yet distinguishable, problems—the nature and propagation of light, and the process of visual perception. Either problem could serve as an effective starting point for an investigation of early optics, but the second is clearly the broader and more representative. The problem of vision not only embraces the anatomy and physiology of the visual system, the mathematical principles of perspective, and the psychology of visual perception, but it also requires us at least to touch upon the nature of light and the mathematics and physics of its propagation.¹⁵

¹³ Ronchi (1970), 4.

¹⁴ See Lindberg (1971), 522.

¹⁵ Lindberg (1976), x.

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Ronchi and Lindberg understood the historian’s task of investigating light to be part of the history of vision. But that was the result of a choice or preference between two possible alternatives, the way of light and the way of sight. If they opted for the way of sight, it was because they thought it fitted better with how the source material treated the subject matter. The possibility of an independent enquiry into the physics of light in the premodern world was still a viable option, theoretically at least. But it was left for others to undertake. Today we know that volunteers have been scant. A survey of the existing literature betrays a steady preference for the visual approach.¹⁶ For Ronchi, Lindberg, and many other historians of optics, the enquiry into the physics of light and its nature was a theoretically valid question, though not one that they could—or would—choose to pursue in practice. That was not the case with another group of scholars who contested the possibility of a genuine enquiry into the physics of light in premodern thought altogether. The new thesis was first argued by one of the most influential voices in continental scholarship, that of Gérard Simon. Simon accused Ronchi and Lindberg of assimilating light (the light ray) to sight (the visual ray).¹⁷ He thereupon completely rejected their approach, dedicating a whole book to showing that the centre of the preoccupations of the Ancients is in no way the propagation of a ray but the positioning of an image, on account of the fact that they treat of vision and not like us of light.¹⁸

Simon’s concern was that contemporary scholars, like Ronchi and Lindberg, read the sources anachronistically, though probably without being aware of it (victimes d’une illusion rétrospective):¹⁹ they force the ancient texts by unduly modernizing their meaning, assuming that premodern thinkers had the same interests as we do (fausser indûment des centres d’intérêt qui ne sont plus les nôtres), not realizing that ancient sources were asking radically different questions from ours (questions radicalement différentes).²⁰ The reason is that there was no physics of light in the ancient world, only a concept of sight of which light was an integrated part: for the ancients ‘it was impossible to pose the question of the physical nature of light independently of vision, since the proprium of light was to manifest things, whether by dazzle or by making the blue, the red, or the green visible’.²¹ Simon, ¹⁶ See, from recent literature, Zemplén (2005); Darrigol (2012); Siebert (2014). But cf. the suggestions of Berryman (1998), esp. 194–6: Euclid’s visual ray model dependent on its underlying theory of light; Webster (2014): Euclidean Optics dependent on propositions and proofs from the astronomical tradition (celestial illumination). ¹⁷ See Simon (1988), 23–4. ¹⁸ Simon (1988), 25 [in French]. ¹⁹ Simon (1988), 23. See also Simon (1996), 11–29, with the charge against Ronchi and Lindberg on p. 16. ²⁰ Simon (1988), 25. ²¹ Simon (1988), 14. See also Simon (1996), 20–1: whichever ancient theory of light we take, ‘light always plays an auxiliary role (un role d’adjuvent), never that of a protagonist’.

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therefore, firmly argued that the history of optics was not the history of light, but the history of the transformation of a discipline and its subject matter: from sight to light (du visible à la lumière).²² In drawing the epistemological consequences of his position, Simon went perhaps a bit too far in contesting the intelligibility of ancient theories altogether: ‘we do not understand the purpose, nor the interests, nor the intrinsic limits of ancient optics. This is at least what this book aims to establish’.²³ But this was consistent with his broader view on the archetypical function of vision in the ancient world.²⁴ For Simon, every transformation of optics was not epistemologically innocuous; it was a transformation of our theory of knowledge (transformation de la théorie de la connaissance). In the end, the passage from sight to light signified not merely a change of the subject matter of a scientific discipline but a broader change in the way we understand the objects of knowledge (objets du savoir).²⁵ Simon’s view gained currency in continental scholarship and the passage ‘from sight to light’ became the quasi-motto of a certain way of understanding the history of optics: as a discontinuous narrative of the transformation of the concept of light, from an intrinsic feature of the mechanism of vision to an independent object of scientific enquiry. I shall from now on refer to this view as the ‘oculocentric’ thesis.²⁶ The thesis also found notable defenders in the English-speaking world. Perhaps the most eloquent example comes from a leading voice in Ptolemaic and Arabic optics, that of A. Mark Smith, who expounded the oculocentric view in a series of publications. Smith famously contested Lindberg’s view that the medieval perspectivist optical tradition was primarily concerned with the physics of light. Contrary to Kepler and his seventeenth-century successors, medieval Arabic and Latin thinkers ‘were far more concerned with making sense of sight than with understanding light’.²⁷ ‘The proper and primary end of perspectivist optics’, Smith repeatedly argued, pace Lindberg, ‘was to make full and coherent sense not of light but of sight.’²⁸ Smith then generalized the thesis. In a recently published monumental monograph, Smith aimed to capture the whole history of optics as the transition from premodern to modern optics—the celebrated passage ‘from sight to light’—as a paradigm shift. In the opening paragraph of his book Smith summarizes his thesis as follows: . . . as currently understood, the science of optics is about light, about its fundamental properties and how they determine such physical behavior as reflection, refraction, and diffraction. But this understanding of optics and its appropriate ²² Simon (1988), 11–20. See also p. 89 for the transformation thesis in the context of Simon’s work. ²³ Simon (1988), 11. ²⁴ Simon (1988), 16–17. ²⁵ Simon (1988), 17. See also Simon (1996), 21–7. For ancient optics as part of Simon’s broader epistemological agenda see Caveing (2007). ²⁶ Simon is standard reference in French literature, see, for example, Vasiliu (2010), 6, and PardonLabonnelie (2010), 45. ²⁷ Smith (2004), 181. ²⁸ Smith (2010), 165.

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      purview is relatively new. For the vast majority of its history, the science of optics was aimed primarily at explaining not light and its physical manifestations, but sight in all its aspects from physical and physiological causes to perceptual and cognitive effects. Consequently, light theory was not only regarded as subsidiary to sight theory but was actually accommodated to it. And so it remained until the seventeenth century, when the analytic focus of optics shifted rather suddenly, and definitively, from sight to light. Marking the turn from ancient toward modern optics, this shift of focus evoked an equivalent shift in the order of analytic priority. Henceforth, sight theory would become increasingly subsidiary to light theory, the former now accommodated to the latter.²⁹

It is not difficult to perceive the common agenda between Smith and the continental school of thought. For Smith, too, there is a discontinuity between premodern and modern optics.³⁰ According to the premodern optical paradigm, light was not the primary object of scientific enquiry. That role was reserved for sight, while light was an enabler or a mediating factor. Only in that subsidiary sense was there conceptual space for an enquiry into light. To be clear, Smith did not go as far as to challenge the intelligibility of the ancient sources. But he did recognize the archetypical function of optics, acknowledging that the transformation of the visual model had ‘ramifications that extended well beyond its ostensibly narrow subject matter in light and sight’. Thus, for Smith, the passage from sight to light caused a tremendous shift in the way people conceived the world, signifying not a mere transformation of a scientific discipline (optics), but a real paradigm shift in the Kuhnian sense (‘Keplerian turn’).³¹ It was a change in world view, with ‘ramifications in such apparently disparate fields as theology, literature, and art’.³² I have here sketched the contours of the modern historiography of light, following the narrative that was first laid out in the works of Ronchi and Lindberg, noting a subtle but crucial turn in this narrative suggested by Simon and recently exemplified by Smith. If I am right, there seems to be considerable consent: the passage ‘from sight to light’ becomes the signpost of a certain approach to the history of optics that studies light as part of sight in the ancient sources. Beyond this, there is room for dissent: according to some, a vision-independent enquiry into the nature of light in ancient sources is—theoretically, at least—a viable possibility (Ronchi and Lindberg). According to others, the ‘oculocentric’ nature of ancient optics denies such a possibility. In its softer version (Smith), this latter view enquires into the nature of light in the premodern world as an integral, auxiliary part of the study of sight; the genuine enquiry into light as an ‘objective’, physical agent in the world will have to wait for the paradigm shift that occurred in the

²⁹ Smith (2015), ix. ³⁰ Smith (2004), 180, 193–4; Smith (2010), 166. ³¹ Smith (2015), x, 2, 277. ³² Smith (2015), 277.

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seventeenth century.³³ In its stronger version (Simon), the oculocentric narrative precludes all possibility of light being knowable as such in the ancient world. Light was a sui generis construction, coextensive with sight. The ancients simply lacked any independent notion of light.³⁴ Clearly, the oculocentric thesis presents a challenge for the study of hexaemeral light. It puts under scrutiny the basic intuitions of the biblical exegete who, like Ronchi, attributes to light a physical existence of its own, independent of a perceiving subject. More specifically, it questions the possibility of an enquiry into the nature of biblical light independent of a corresponding theory of vision. Taking the oculocentric thesis to its logical conclusions, there can be no physics of light in the biblical creation narrative, only a theory of vision to which light is somehow instrumental. But in the beginning, the biblical exegete may protest, there were no eyes to see the light. The first animals were created on the fifth day of creation, humankind on the sixth. Who was there to contemplate primordial light apart from God? And no mainstream theologian would want to understand God ‘seeing’ the light according to Gen. 1:4 in a literal sense. Primordial light should then be conceived independently of any theory of vision. The ocularist thesis is surely inapplicable to the first light of creation. Or is it?

1.3 Three Arguments for Oculocentrism in the Hexaemeral Literature 1.3.1 Sight Fantastic The first chapter of Genesis does not say much about angels. In fact, it does not say anything at all. This was felt as a gap by late antique Jewish and Christian exegetes, who had to face the competition from rival accounts of the cosmogenesis.³⁵ The Babylonian creation myth opened up with a section on theogony to account for how order was bestowed upon disorder and the world came to be. Similarly,

³³ According to Smith (2004), in the premodern optical paradigm of Alhacen and his Latin followers, ‘pure light is a mere theoretical abstraction’ (p. 183). In a pre-Keplerian context, ‘the science of optics is not about light radiation, reflection, or refraction, as we understand them in the modern, objective sense, but about how we perceive things directly or by mediation of reflective or refractive surfaces’ (p. 191). ³⁴ See Simon (1988), 25–36. See further Blamont (2004), 199: ‘We should not search in ancient science for anything of what we nowadays call the explanation of the phenomenon of light. In fact, as Gérard Simon writes, ancient optics is in the first place an analytics of vision. None of our concepts (ray, image, visible, visual field, binocular vision, object, subject, etc.) are transposable as they are into ancient and medieval texts’ (italics in the original; my translation). In a recent paper, Smith (2019) fully endorsed Simon’s view and offered some further clarifications of his position. I discuss this latest stand in Appendix A. ³⁵ On the interplay of Jewish, Christian, Gnostic, and Platonic cosmologies in late antiquity see Endo (2002); van Kooten (2005); Blowers (2008a), 908–11.

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ancient Greek cosmogonies explained cosmic order by reference to the successive births of celestial and chthonian deities, their marriages and their battles. The educated pagan had in addition more philosophical creation myths at their disposal, like the Platonic Timaeus, which had something to say and even more to suggest on secondary gods and celestial daemons. The ‘Gnostics’ developed their own genealogies of Aeons and Archons, which they creatively embedded in their cultural milieu, drawing on the mythological, the philosophical, and the biblical traditions. Add to that the Greco-Roman popular religion, with its focus on the life of the stars and their heavenly inhabitants. Nor must we forget that Jewish Second Temple literature had also its fair share of angelology, of which the Enochic literature is a fine specimen. In this context, the silence of the biblical creation narrative might be suspected of concealing more than it was revealing. Since angels were no strangers in the biblical world, Jewish-Christian readers demanded to know why Moses eschewed mentioning their creation. They also needed to know what the role of angels in creation was. That put the hexaemeral exegetes to work. The result was the emergence of a special section on angelology in hexaemeral literature. A parallel tendency can be observed in the rabbinic exegetical tradition, which developed a vivid interest in the question of the day that God created the angels (Bereishit Rabbah 1:3). The hexaemeral exegetes justified the silence of the Mosaic account by appealing to the principle of ‘considerateness’ or ‘condescension’ (sunkatabasis) of Scripture: it was for the purpose of divine pedagogy that Moses did not include angels in the creation account.³⁶ For the proponents of the allegorical school, sunkatabasis meant that the creation of angels belonged to the deeper subtext of the creation narrative, concealed under the letter of the text for the sake of the uninitiated, ‘who were unable to endure the burden of investigating matters of such importance’. Angelology was a teaching reserved for the spiritually advanced.³⁷ For the proponents of the grammatical–historical school, sunkatabasis meant that Moses did not mention the creation of angelic powers because of the immaturity of his audience ‘and the materialism of his listeners’. Moses’ main concern was to draw the Israelites away from the dangers of idolatrous polytheism. He thus chose to instruct them in natural theology, leading them ‘for the time being from visible realities to the creator of all things, so that from created things they might come to learn the architect of all and adore their maker, not stopping short at creatures’. Only when the Israelites had matured in faith was the time ripe for them to be gradually initiated to the higher mysteries of creation that included the spiritual world.³⁸ What was common to both traditions ³⁶ On the patristic hermeneutics of sunkatabasis see Hill (1981), 3–11; Sheridan (2015), esp. 27–44. ³⁷ See Origen, DP IV.II.7–8. The addressees of sunkatabasis are according to DP IV.2.4 the simpliciores. These again must be the early-stage catechumens as we learn from CC II.4 and III.51. ³⁸ See Chrysostom, Hom. Gen. II.2–3 PG 53:28–9. The same teaching is repeated in Serm. Gen. I.2 (SC 433, 148–56 = PG 54:582–3), with some extra material.

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was the key role of the readers and their capacity to discern the depth of Scripture. The teaching about the spiritual world was accessible only to the more advanced readers. With this caveat in mind, the hexaemeral authors recognized a significant place for angels in the creation of the world. They were the spectators of God’s work. We get a first hint about the role of angels as contemplators of creation from the longest fragment we possess from Origen’s lost Commentary on Genesis.³⁹ The fragment comments on Gen. 1:14, which in the Septuagint version refers to the stars as being established ‘for signs’ (eis sēmeia). Origen found here the chance to provide a lengthy disquisition on astrology and the controversial question of whether the stars are causes.⁴⁰ In his exegesis, which had a long-lasting effect in the subsequent tradition, Origen distinguished between the causal power of stars, which he rejected, and their power to predict future events, which he accepted. The underlying idea, which was certainly not original, was that the stars are like letters written in the sky, literally heavenly ‘signs’ written by God for the angelic powers to read, rejoice in, and be instructed, just as we are instructed by reading the Bible.⁴¹ The image was borrowed from apocryphal literature, exploiting the analogy between the Torah and the world.⁴² It is clear from this passage that angels had, apart from their ministering, also a contemplative role to play in the world. Origen did not specify whether the kind of vision angels employed had as its object the sensible image of the stars or their intelligible principle. The question would be too long to discuss here, but a physicalist approach to angelic sight should not be dismissed out of hand. It suffices to say that there is enough evidence to suggest that Origen accepts an ethereal region in heaven along with an ethereal composition of the astral body of its angelic inhabitants and with some kind of idiosyncratic, heavenly, or ‘spiritual’ senses.⁴³ All this strongly suggests that the angelic vision of the stars may be understood quite literally in the context ³⁹ This is fragment D7 from the editio minor by Metzler (2010), 70–152. The fragment is translated into English by Trigg (1998), 86–102, with notes and an introduction. Further leads are Origen’s spiritual interpretation of ‘heaven’; see Köckert (2009), 256–67, and the doctrine of the pre-existence of rational souls; see Martens (2013). Both leads support the existence of angels, but do not tell us much about their corporeality. That is why I will not pursue them further. ⁴⁰ On the debate see Scott (1991), 145–6; Kalligas (2014), 278–82; Rasmussen (2019), 156–72; Juurikkala (2019), 84–90. ⁴¹ We find the same idea in Origen’s younger contemporary, Plotinus; see Enn. II.3.7 and III.1.6. The analogy and the striking similarity of the overall argument suggest a common tradition, like the Jewish, so Kalligas (2014), 292 (ad Enn. II.3.7.4–8), 434 (ad Enn. III.1.6.20–4), or a common source, like Ammonius Saccas, so Trigg (1998), 86, from which Origen and Plotinus drew. ⁴² The image of stars as ‘tablets of heaven’ is cited from the apocryphal Prayer of Joseph, a work which must have exercised considerable influence but is otherwise lost; see Smith (1985); Hayward (2005); Edwards (2019), 50; Rasmussen (2019), 170–1; Juurikkala (2019), 85–6. ⁴³ On the ethereal body of angels see Scott (1991), 150–64. On its theological justification see Edwards (2002), 94–7. On the ‘spiritual senses’ in Origen see the still influential article of Rahner (1979), which focuses on Origen’s mode of language of the perception of God. The question posed here goes in the exact opposite direction, i.e. how do angelic creatures and incorporeal souls perceive the sensible world? If we take seriously the theory of the ‘spiritual’, ‘heavenly’, ‘ethereal’, etc. body, we must

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of certain doctrines espoused by Origen.⁴⁴ Be that as it may, literally or figuratively, vision is a faculty that angels certainly possess.⁴⁵ If so, the ocularist thesis may be applied to the hexaemeral narrative in full force. Only a small substitution as regards the agent of vision needs to be made. Instead of light being instrumental to human sight it only needs to be instrumental to angelic sight. Angelic sight was no Origenian fantasy.⁴⁶ The sources inform us that the contemplative role of angels in creation proved to be a long-lasting and widespread idea. It resurfaces clearly in the hexaemeral exegesis of the late fourth- to early fifth-century Antiochene school, in the writings of Severian of Gabala and Theodoret of Cyrus, always in the context of citing Job 38:7. In his hexaemeral homilies, Severian discusses the nature and role of angels in creation while commenting on the ‘let us make’ clause of Gen. 1:26.⁴⁷ He rejects the view that angels could have been assistants of God and only accepts their role as ministers, witnesses, and spectators (theōroi), watching (blepontes) all that followed their creation: They [sc. the angels] watched (eblepon) heaven being made from what did not exist and were astonished; the sea being set within limits and were amazed; they contemplated (etheōroun) the earth being adorned and were startled. Since angels were not assistants but admirers, God tells Job “When I made stars, all the angels sang my praises.” (Cosmog. IV.6 PG 56:465 tr. Hill, slightly amended)

Theodoret discusses the issue even more extensively in his Questions on the Octateuch, a work of the genre ‘questions and answers’. The Questiones in Genesin begin with four questions on the silence of the biblical text about the invisible, spiritual world. Three out of four questions focus specifically on angels, betraying vivid discussions in the background.⁴⁸ In the fourth question,

accept some kind of accompanying (i.e. ‘spiritual’, ‘heavenly’, ‘ethereal’, etc.) sense faculties. That is how I understand the term ‘spiritual senses’ in this context. The only author who comes close to discussing this notion of spiritual senses in Origen is, to my knowledge, Dillon (1986), esp. 451–3. ⁴⁴ Origen, following his contemporary epistemology, for which see section 1.4.2 below, understands vision through a principle of ‘likeness’ or ‘sympathy’ between the sense faculty and the sense object; see e.g. DP I.1.7. This is merely an application in human biology of the cosmic principle of sumpatheia; see Chin (2015). ⁴⁵ On the ambivalence of Origen’s language of ‘spiritual senses’ see Louth (2007), 66–7. See also Coakley (2002), 136–41: figurative language; McInroy (2012): figurative and analogical, with an emphasis on analogical language. These authors, however, discuss the spiritual senses in the trajectory of Rahner (1979), which, as already mentioned, is not the direction I am taking here. ⁴⁶ See, for example, Plutarch, Is. et Os. 360E: records of experiences (pathēmata) of daemons, who also share ‘in the nature of the soul and in the perceptive faculties of the body (sōmatos aisthēsei)’. On the equivalence of Jewish-Christian ‘angels’ with pagan ‘daemons’ see section 1.3.2 below. For two excellent discussions of the material composition of angels/daemons in late antique literature see Smith (2008); Jacobs (2012). If some sort of bodily existence of spiritual beings is allowed, then sense perception, including vision, is a mere concomitant of their bodiliness. ⁴⁷ Severian, Cosmog. IV.6 (PG 56:464–5). ⁴⁸ See Hill (2007), xlviii–xlix.

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which is a dialectical refutation of the alleged pre-existence of angels based on an interpretation of Job 38:7, Theodoret expounds the same view as Severian: Now, the angels were probably created along with heaven and earth so that on seeing (horōntes) the light created from no pre-existent material, the firmament fixed in the midst of the waters, the water separated from the land, the earth beautified with all kinds of plants as soon as God spoke, and everything else made at God’s discretion, they might realize, through what they saw (horōsin), that they also have a created nature and receive existence from him. The holy apostle, in fact, links them to the world in saying, “We have become a spectacle (theatron) to the world, to angels, and to human beings.” (Quest. in Gen. IV.2 Petruccione 16.28–37 tr. Hill)

Severian and Theodoret argue explicitly for the role of angels as spectators of creation. They both follow the hermeneutics of sunkatabasis as developed by Chrysostom.⁴⁹ The shared hermeneutics and argument suggest a common theme in the Antiochene school of thought, of which Severian and Theodoret are both adherents.⁵⁰ Angels were ‘watching’ (eblepon) the heaven being made (Severian); they were ‘seeing’ (horōntes) the first light (Theodoret); they were ‘watching’ (eblepon) the stars being made (Theodoret). That is precisely what the oculocentric thesis needs in order to sustain itself in a hexaemeral context. If there were angels ‘seeing’ the primordial light the vision-centric interpretation of ancient theories of light cannot be dismissed out of hand. On this point the Antiochean meets the Origenian tradition.⁵¹ The hexaemeral literature provides ⁴⁹ See Severian, Cosmog. I.2 PG 56:431–2; Theodoret, Questions I–II PG 80:77–80 = Petruccione 6–11. The connection is noted by Hill (2007), 7–9 n.2 and (2010), 24–5 n.11. ⁵⁰ Further evidence: fr. 11 of the parallel catenist tradition (Col. Coisl.), cited at the beginning of this section, expressing a view very close to Severian. The text is traditionally attributed to Severian, but the elements of creation that the angels contemplate in the text and in the passage from the Cosmog. are not identical. Thus the editor, in my view rightly, suspects a different attribution from within the Antiochene school, most likely Theodore of Mopsuestia; see Petit (1986), ad loc. with note. Relevant also are two fragments from Diodore of Tarsus, fr. 16 and fr. 43bis (Col. Coisl.), accepting a spiritual heaven for the invisible and intelligible substances, i.e. the angels, with a role analogous to the one that the visible heaven plays for us. ⁵¹ See two examples: 1) Ambrose, Exam. II.4.15: the powers (potestates) which are in the visible (!) heaven (visibili loco) ‘behold’ (spectent) and ‘observe’ (conspectibus habeant) ‘all this’ (haec omnia). The reference of haec omnia is unspecified. But the immediate context is about the visibility of heaven, with the distinctively Platonist etymological tradition of ‘ouranos apo tou horasthai’; see Opif. 37, going back to Rep. 509d3, implied also by Tim. 23b7–8, with Crat. 396b6–c1 in the background. The whole context refers to visible creation, most probably the entire celestial creation (omnem celestis creaturaem), citing also Ps. 18:2. In this context, the passage clearly gives the theme of angels as spectators of creation. 2) Didymus, Com. Gen. 76.15–19: discussion of the pre-existence of angels in the context of Job 38:7, at which point the commentary is suddenly interrupted for several pages. This appears to be the view discussed by Theodoret in Questio IV PG 80:81–4 = Petruccione 14–19, also espoused by Severian and fr. 11 from the parallel catenist tradition (Col. Coisl.), with the caveat made by Theodoret ad loc. in fine. Though speculative, the literary context and the mention of Job 38:7 leave, in my view, no doubt that in the missing part of the commentary Didymus elaborated on the contemplative role of angels in creation.

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then a robust argument in support of the oculocentric interpretation of ancient theories of light. It is true there were no human eyes present when God created light and the heavenly stars. But that does not mean that there were no eyes at all. One may wonder whether the tactic of transferring the visual context from the human to the angelic realm is a prudent move to make. But the biblical universe is a world suffused with angels, and this is a non-negotiable framework for the biblical exegete. Given the existence of angels, the ocularist move does not come at any extra cost. It just makes use of the premises already available to the biblical exegete. If so, the hexaemeral authors were essentially right in putting the hand in the cookie jar. If there are angels in the world, simple curiosity compels the biblical reader to ask about their place and role in creation. The allegorist may refrain from saying too much and the literalist may send warnings against asking too much about what lies beyond the letter of the text. In the end, however, both allegorist and literalist have to say something about spiritual beings. What they give us is a story about vision: angelic powers contemplate God’s work, take pleasure in it, and learn from it. With this kind of story, oculocentrism becomes possible for hexaemeral light. The fuzzy ontological status of the angelic spectators (‘created before creation’) complicates the metaphysics of vision a bit. But the underlying hermeneutical principle may very well hold. All metaphysical weirdness aside, light may indeed function, purely and simply, as an instrument of angelic sight.

1.3.2 A World with a View Angel-sight and the celestial book of signs evoke something of childhood memories to the contemporary reader. The world of late antiquity, however, is a world where some of our fairy tales come true. In this world daemonology, the pagan equivalent of angelology, is discussed in literary circles and is part of the philosophical curriculum.⁵² Calcidius, a fourth-century philosopher and, allegedly, a contemporary of Athanasius and the Cappadocians, begins the second part of his Latin Commentary on the Timaeus with the section on the four kinds of living beings and the heavenly gods (Tim. 39e3 sqq. = Calc. In Tim. 119 sqq.). The passage had already become the locus classicus of pagan philosophical speculation on daemons through the mediation of a rich interpretative tradition.⁵³ Calcidius ⁵² On pagan daemonology and its sources see the excellent studies of Timotin (2012) and Mihai (2015). The marriage of philosophical daemonology with biblical angelology goes back to Philo of Alexandria; see Somn. I 141: what the philosophers call ‘deamons’ Scripture calls ‘angels’; Timotin (2012), 100–12; and Calabi (2008), 111–25, esp. 118: ‘Indeed, for Philo, the name “daemons” is equivalent to the term “angels,” it just belongs to a different theoretical sphere: the former is a Platonic name, the latter a Biblical one.’ ⁵³ On Calcidius’ daemonological section see den Boeft (1977); Somfai (2003), 129–42. On the tradition see the discussion in this section.

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opens his remarks by recalling the purpose of the Timaeus—contemplation of nature (contemplatio naturae).⁵⁴ He then enumerates the four kinds of sentient living beings, celestial and terrestrial, and proceeds: Not confining himself to treatment of the aforementioned living beings, he extends his attention to unravelling the question of the angelic nature, the beings he refers to as daemons. Of these, the purer type has its abode in the ether, the second in the air, the third in the region named the moist substance, such that the internal parts of the world are filled with living beings endowed with reason and no region of it is deserted. And this treatment he necessarily postpones, since it is of a higher order and beyond the contemplation of nature . . . (In Tim. 120 tr. Magee; my transliteration for daemon)

Though Calcidius acknowledges that the Timaeus is a work on physics (physica) and therefore not suited for a discourse on the nature of daemons, he continues on the subject for several pages, drawing on the wider Platonic corpus (127–36).⁵⁵ Midway, Calcidius makes an astonishing and valuable remark on the harmony of the Platonic with the Jewish-Christian tradition on celestial beings: The view held by the Hebrews is in accord with this as well, for they claim that the God who conferred order upon the world bade that the sun’s province should be to rule over the day, and the moon’s to keep watch over the night, and that he also disposed the other stars as the limits, as it were, between temporal periods and as the signs of the years, as indication also of future events. (In Tim. 130 tr. Magee)

The passage that Calcidius paraphrases is none other than Gen. 1:14. We have seen how this passage was used by Origen to argue for angels as spectators of creation. We have also seen how this theme was disseminated in the subsequent tradition. Thereupon, Calcidius sees no problem in expressly identifying the Platonic talk of ‘daemons’ with the Jewish-Christian talk of ‘angels’ (132–3). His definition of a ‘daemon’ as ‘a rational, immortal, passible, ethereal living being engaged in the care of human beings’ (135) is representative of Middle Platonic daemonology but resonates equally well with Jewish-Christian angelology.⁵⁶ In his eyes, clearly, angels and daemons have the same referent.

⁵⁴ On Calcidius’ reading of the Timaeus see Somfai (2004), 205–6; Hoenig (2018), 168–77; Reydams-Schils (2020), 21–36. ⁵⁵ On the thorny question of Calcidius’ sources see Somfai (2003), 131–2; Hoenig (2018), 163–4; Reydams-Schils (2020), 141–90. ⁵⁶ The definition resembles that of Apuleius’ in Deo 13, as shown by den Boeft (1977), 38, and Dillon (1996), 318 n.1, but the crucial formula diligentiam hominibus impertiens (‘engaged in the care of human beings’) is Calcidius’ addition. The idea of daemons ‘caring’ for human affairs goes back to

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The case of Calcidius shows that even as late as the fourth century it was possible to consider the Timaeus creation myth and the Genesis creation narrative as sources of parallel and compatible hermeneutical traditions. They could be regarded as anagogical discourses on physics. And they both seemed to serve a common purpose: contemplation of nature.⁵⁷ They could equally be classified as works on natural philosophy or natural theology. In both of them contemplation was not a role exclusive to humankind, as we would today assume. Spiritual beings, whether angels or daemons, were the contemplators of nature par excellence. The interpretative steps leading—not without jumps—from the Timaeus to late antique daemonology have been thoroughly investigated in recent scholarship.⁵⁸ In an excellent study, Andrei Timotin has explored the development of the daemonological theme in Platonism.⁵⁹ In a programmatic paper, Keimpe Algra has investigated its reception in Stoicism.⁶⁰ John Dillon and Francesca Calabi have highlighted different perspectives on the theme in Philo, and David Runia has shown how it entered the hexaemeral tradition through the De opificio.⁶¹ Allan Scott has extended this path down to Origen.⁶² I have shown above how the trajectory reached the rest of the hexaemeral tradition and cited Calcidius to better illustrate a hexaemeral author’s literary context. Add to this the proliferation of daemonology in ‘Neoplatonism’ and we can now have a better glimpse into the hexaemeral world.⁶³ It is a physical universe that does not exhaust itself at a materialist mechanics of nature, but also includes the quasi-physical mechanics Hesiod, Works 123 (daemons as ‘guardians (phulakes) of mortal men’) and seems to echo in the myth of the Statesman 271d–e, see Timotin (2012), 69–72. But it later acquired a stronger sense of ‘ministering’ to human beings almost contemporaneously in the Jewish, the Christian and the Platonist tradition, with strikingly similar vocabulary, cf. the Philonic formula hupēretisi kai diakonois (Gig. 12); the ‘Pauline’ formula leitourgika pneumata eis diakonian apostellomena (Hebr. 1:14); and Plutarch’s formula hermēneutikon kai diakonikon genos (Is. et Os. 361C; Def. or. 416F). Through his own formula of diligentia hominibus Calcidius was able to engage simultaneously audiences from the Jewish-Christian and the Platonist traditions (or was conversely drawing from his own schooling in them). ⁵⁷ That anagogical contemplation of creation is the purpose of patristic hexaemeral exegesis has been demonstrated by two wonderful studies; see Pelikan (1993), esp. 90–106; and Blowers (2008b). The theme of the ‘contemplation of nature’ has a ‘Platonic’ ring; see the epoch-making study of Nikiprowetzky (1977), 102–8, and now the magisterial study of Köckert (2009), esp. 528–30. The theme is hermeneutically reworked through Stoic-Homeric exegesis, enters the hexaemeral tradition through Aristobulus and Philo, and reaches the Christian authors through Clement of Alexandria; see Rizzerio (1996), 100–49; Di Mattei (2006); Lollar (2013). In the Platonist tradition the theme climaxes in Plotinus’ (singular) insight in Enn. III.8 that ‘nature contemplates’; see the classic study of Deck (1967); and more recently Wildberg (2009). Calcidius confirms this picture: anagogical contemplation of nature is no genuine hexaemeral insight. But see section 1.3.3 below on the Christological transformation of the theme in the hands of the hexaemeral authors. ⁵⁸ See Colpe et al. (1976); Brenk (1986). ⁵⁹ See Timotin (2012). Still to be consulted are the relevant sections from Dillon (1996), 31–2, 90–1, 171–4, 216–19, 287–8, 317–20, limited, however, to Middle Platonism. ⁶⁰ See Algra (2011). ⁶¹ See Dillon (1983) and the commentary in Winston and Dillon (1983), 236–44; Runia (1986), 227–31; Calabi (2008), 111–25. ⁶² See Scott (1991), 113–49. ⁶³ See Zintzen (1976); Nasemann (1991); Wilberding (2006), 206–7.

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of spiritual powers. In this world, the starry sky is full of life. Hexaemeral physics includes the material but invisible inhabitants of the heavenly regions, in which humankind also originates. Hence the astonishing remark, for modern ears, that Basil makes regarding the heavenly (literally) origins of humankind. In reprising the Timaean theme of the sky as the original abode of humankind (Tim. 90a), filtered through the Stoic-Philonic image of the cosmos as a great city (megalē polis),⁶⁴ Basil allows himself to say: In this city in which is our ancient home (en tē polei tautē, en hē ē archaia patris hēmōn), and from which the man-slaying demon drove us, selling mankind into slavery by his allurements, here, I say, you will see the first origin of man and death, which immediately seized upon us and which had been begotten by sin, the first-born offspring of the demon, source of evil. (Hex. VI.1 GCS 88.12–16 tr. Way)⁶⁵

Basil then espouses a world of Stoic-Platonic coded echoes, according to which the cosmos is a ‘mega-city’ and humankind its proper citizen (cosmopolitēs).⁶⁶ This world, filled with earthly and heavenly life, is itself a living being.⁶⁷ As a living

⁶⁴ See Runia (2001), 339–40 (§142), 341–2 (§144). ⁶⁵ The text has clear Plotinian resonances; see Enn. I.6.8.16–28, though for Plotinus the original home of the soul is supra-worldly. As Kalligas (2014), 213–14, has shown, the imagery was not original but was in wide use in Homeric interpretation and the novelistic literature inspired by the Mystery cults. Rudberg in the apparatus fontium of the critical edition (GCS p. 88) cites as examples Plato, Rep. 592b; Cicero, DND II.62.154; Clement, Strom. IV.26. He further cites the hexaemeral homily IX.2 (CGS pp. 148.23–149.10), which reprises the theme with a clear allusion to Tim. 90a. All these are references to the Platonic imagery of the heavenly city and its Stoic reinterpretation of the cosmos as a city. Basil’s use of the imagery has created a stimulating controversy between Rousseau (1994), 318–49, 320 (the ‘ancient fatherland’ is ‘a world that was invisible and eternal’, i.e. paradise), and Costache (2013b), 108–9 (the phrase ‘ancient fatherland’ is not to be found in the Hexaemeron nor does it refer to paradise as a heavenly realm). As regards the text, Rousseau is right: the locution ‘ancient fatherland’ (archaia patris) is used verbatim in the passage cited. As regards the context, Costache can cite in support Hom. 336.7 (Quod deus non est auctor malorum, PG 31.314–15), while Rousseau may respond by citing the third homily of the De creatione hominis (for its authenticity see section 1.3.3 below), which uses the same language of patris and politeuma as here, suggesting carefully but clearly that paradise, though material, is not a place on earth, but the dwelling place of the saints. Both sides are partly right. The language of the hexaemeral passages (VI.1 and IX.2) is loaded with Platonic allusions, too suggestive of paradise as a heavenly realm to be taken as a simple metaphor. But this realm is not disembodied, as it is e.g. for Plotinus. It is the heavenly cosmos, the supralunary, or, as Mihai (2015) has argued, a special region of it, astonishing as this may sound to modern ears. ⁶⁶ On the Hellenistic ideal of cosmopolitanism see Schofield (1991); on its hexaemeral appropriation see Runia (2001), 103 (§3), 339–40 (§142). ⁶⁷ See Tim. 32c2–31a1; 39d8–e2; 92c5–7 and the collection of Stoic passages in Long/Sedley 53 with commentary (pp. 319–23). On Plato’s cosmobiological model and its philosophical background see Lloyd (1966), 232–72; for its Stoic development see Hahm (1977), 136–84; for late antique Platonism see Clark (2016), 209–25; for Plotinus in particular see Wildberg (2009), 143: spiritualization of the entire universe as the apex of ancient Greek speculation about nature. Twentieth-century scholarship has often dissociated Christianity from this worldview; see Zachhuber (forthcoming), with critical discussion. This led to the widely held assumption that Basil rejected the notion of the world as a living

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being it has a soul and a body.⁶⁸ If it has a body it might also have some kind of sense perception. This raises the question of cosmic vision. The idea that the world had a faculty of vision had wide currency in the religious-mystical milieu of the imperial era, strongly associated with the Egyptian and the Chaldean cult, and was discussed vividly in literary and philosophical circles.⁶⁹ It continued to generate stimulating discussions in late antiquity, as we can judge from Proclus’ vivid interest in the matter in his Commentary on the Timaeus.⁷⁰ Proclus reports on two tendencies: a poetic-theological tradition, reaching back to the Homeric worldview and identifying the sun, the moon, and the stars with celestial eyes; and the explicit contrary view of Plato in the Timaeus (33c1–4), which had its special weight among the Platonists. Proclus’ own solution lies somewhere in between, allowing for a sui generis cosmic perceptual apparatus, which does not operate like our bodily sense organs. Having explored this idiosyncratic faculty of cosmic perception, Proclus remarks:

being; see Louth (2009), 52. As van Kooten (2003), 169–70, 175–9, has convincingly shown, however, the cosmobiological model together with the idea of the cosmic city find clear scriptural expression in the Pauline literature, especially in Eph. 3:10 and 3:14–21. Origen certainly reads Paul this way, as is clear from the Hom. Ezek. IV.1–4. From then on, Origen fully subscribes to the cosmobiological model, as Scott (1991) thoroughly showed. Basil’s worldview, then, draws upon genuine scriptural premises filtered through an Origenian legacy. The cosmobiological model is clearly introduced in the hexaemeral homilies through the identification of the spirit hovering over the waters in Gen. 1:2b with the Holy Spirit, expressly indicating the life-giving power (zōtikēn tina dunamin) animating the universe (pros zōogonian); see Basil, Hex. II.6 GCS 31.1–22 and further Gregory, In Hex. 19 GNO 31.7–32.19. To the possible objection that Basil explicitly denies that stars are living creatures, see Hex. VI.7 GCS 99.23–100.2, and Rasmussen (2019), 80, 150, 178–80, 185, one need only answer that the objection misses the point of Basil’s critique: the heavenly bodies are precisely what their name says, namely bodies, i.e. receptacles (or in Basil’s own terminology ‘vehicles’: ochēma, see Hex. VI.2 GCS 90.22–91.11, and my discussion in Chapter 3, section 3.1.1 with comments) of the life-giving power permeating the universe. The same point is emphatically made when Basil denies the Manichean view of an innate (enapokeimenēn) earth soul (psychēn entithentes tē gē) in order to stress that the soul (psuchē) of the earth, in the sense of the power of the earth to generate things, bringing them from a state of potentiality to a state of actuality (tēs energeias tēn dunamin), is not an inherent quality but implanted by God through the mediating activity of the divine logos (para tou theou dia tēs epitagēs); see Hex. VIII.1 GCS 126.7–127.7 and already Hex. V.1 GCS 69.6–9, 70.4–9. Basil’s aim is not to refute the notion of a world soul (allegedly following Aristotle’s critique in the Cael. 284a), but to affirm the causal dependence of every kind of soul on God. The possibility that Basil entertained the notion of a soul of the earth sounds so difficult to our modern presuppositions that Sr. A. C. Way in her established English translation avoided translating the word psuchē as ‘soul’ in four out of the five times that the term appears in the key passage of Hex. VIII.1 GCS 126.7–127.7, rendering it instead as ‘life’. This translation is misleading in this context since Basil consciously adopts the term psuchē, deviating for the purposes of his discussion from the biblical term psuchēn zōsan and the philosophical term zōē which occupy the previous and the following passages and which properly denote ‘living creature’ and ‘life’. The more natural way of reading Basil’s text is through the lens of the basic Timaean distinction between the world’s body (31b4–34b9) and the world’s soul (34b10–36d7). If so, Basil does not reject the cosmobiological model as such but only its wrong application, which fails to distinguish between the body of the universe (i.e. the stars, the planets and the earth) and the power of the logos that animates it (i.e. the Holy Spirit). ⁶⁸ For the scriptural background see the magisterial discussion of van Kooten (2003), 9–58: the term ‘body’ (sōma) in Col. 2:19 should be understood as referring to the body of the cosmos. ⁶⁹ See Pardon-Labonnelie (2010), 45–64. For ancient Greek literature, see Bielfeldt (2016), 123–6. ⁷⁰ See Proclus, In Tim. II.81.12–85.31.

   

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For as a whole it [sc. the world] is itself both a thing that is seen and an eye, since we say that the sun is an eye as well as each of the stars. Therefore the whole cosmos is both vision and what is visible, and it really is ‘grasped by perception and opinion’ (28a2) by virtue of its sensing itself and holding opinions concerning itself, for it is grasped by these [sc. perception and opinion] in the primary manner. (In Tim. II.84.5–10 tr. Baltzly)

Proclus’ testimony is crucial. It allows for an oculocentric move that is not available to the contemporary reader. If the sun and the moon, but also the stars, function, for Proclus and the tradition he represents, as heavenly eyes through which the world sees itself, oculocentrism is right at home in the philosophical context of hexaemeral writings. How seriously can hexaemeral authors take such an oculocentric cosmology? It appears that hexaemeral authors take the possibility of cosmic vision quite seriously. We have two influential testimonies. Basil mentions twice the image of the sun and the moon as celestial eyes, and so does Ambrose, who depends largely on Basil. In Basil the image is a simile: [The sun] is as conspicuous in creation as (hoionei) a radiant eye. (Hex. VI.1 GCS 89.13–14 tr. Way) The earth had received its ornamentation from its own plants; the heavens had received the flowers of stars and had been adorned with two great lights as if (hoionei) with the radiance of twin eyes. (Hex. VII.1 GCS 111.4–7 tr. Way)

But the hoionei clause is dropped in Ambrose and what remains is the claim that the sun and the moon are truly the eyes of heaven: It is true that it [sc. the sun] is the eye of the world (oculus mundi), the joy of the day, the beauty of the heavens, the charm of nature and the most conspicuous object in creation. (Exam. IV.1.2 tr. Savage) The heaven, too, with the sun and the moon, the twin lights of its countenance (uultus), and the splendid array of the stars shone forth. (Exam. V.1.1 my translation) The eyes in man correspond to the sun and moon in the heavens. The sun and moon are the twin lights of the firmament. (Exam. VI.9.55 tr. Savage)

Taken out of context, Ambrose’s remarks may sound like a colourful figure of speech.⁷¹ The purpose of this section has been to place even the most literally ⁷¹ Or they are not properly understood. Compare, for example, Ambrose’s original text in the second abovementioned passage with Savage’s translation. Ambrose writes: ‘caelum quoque sole et luna

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inclined hexaemeral authors, like Basil, in their own cosmological, literary, and religious-mystical context. Read in this context, the imagery of celestial eyes cannot be dismissed as merely ornamental. In the hands of Ambrose, the imagery perfectly matches the poetic-theological tradition reported by Proclus. It is meant in a literal sense, not as a mere figure of speech. In the hands of Basil, the imagery is nuanced by a literary trope, an hoionei clause. This places Basil on the side of the other tradition reported by Proclus, together with traditional Platonism.⁷² Ambrose and Basil become exemplary cases of a distinctive ocularist theme and its possible modes of appropriation in hexaemeral hermeneutics. The image is taken seriously, whether in a literal sense or as a literary device appealing to a late antique author’s intellectual milieu.⁷³ This seriousness provides a further argument in support of the oculocentric thesis. Next to primordial light, which is the object of contemplation of spiritual-angelic beings, now celestial light appears to emanate from luminous eyes in the sky, namely the sun, the moon, and the stars. If so, the hexaemeral world is, truly, a world with a view. It looks down upon us and in so doing it brings light and sustains life on earth.

1.3.3 A Christocentric Vision of Creation Next to angel-sight and celestial vision there was a third, more down-to-earth move available to hexaemeral authors in support of oculocentrism: the teleological interpretation of creation. The Septuagint text offers two hints pointing towards such an interpretation. In verses 1:14–19 (fourth day), the Greek grammar suggests a purposive role of the heavenly bodies: they are intended to illuminate the earth and to produce the seasons etc. (1:14–15 eis + accusative denoting purpose or intention); they are meant to separate day and night (1:14 articular infinitive in genitive denoting purpose); their purpose is to send their light to earth (1:15 and 17 hōste + infinitive expressing an intended result).⁷⁴ Similarly, in verses 1:28–30 (sixth day), the whole vegetative and animal world is portrayed as a kingdom offered to humankind to conquer and rule. The underlying idea is that the celestial bodies, the animals, and the plants are created to serve the geminis uultus sui luminibus stellarumque insignitum decore fulgebat’ (CSEL 140.10–12). Savage translates: ‘The sun, too, and the moon, those twin luminaries, and the stars in their splendour shone fourth in the heavens’ (V.1.1 Savage 159). Savage’s translation conceals that the sun and the moon are the twin lights of a (heavenly cosmic) face—uultus, completely untranslated—and mistakenly assumes that the heaven (caelum) is the object of the verb (fulgebat) in the accusative, while it is the subject in the nominative. ⁷² One may suspect an Origenian line of transmission; see Gregory Thaumaturgus (?), To Philagrius [Evagrius], on Consubstantiality §7, preserved under Nazianzen, Letter 243 = Nyssen, Letter 26 PG 46, 1101–8: hoion tis ophthalmos. ⁷³ As Clark (2016), 210, nicely puts it, ‘people in “premodern” times lived, literally, under the eyes of heaven’. ⁷⁴ For the grammar of the Septuagint verses 14–19 see Alexandre (1988), 134–5.

   

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human being in one way or another. The hexaemeral authors made this idea more explicit. The teleological approach enters hexaemeral literature with Philo’s De opificio mundi, exactly where we expect to find it: the exegesis of the fourth (Opif. 53–4) and the sixth day of creation (Opif. 77–8). The exegesis of day four contains the Philonic version of a known Timaean theme, the so-called ‘encomium of sight’ (Tim. 47a–c).⁷⁵ The purpose of the original encomium becomes clear if it is combined with another Timaean passage (90c–d). We then get the picture of sight as supremely beneficial to human affairs because it enables the contemplation of the motions of the heavenly spheres, visible expressions themselves of the motions of the world soul. Sight becomes our ticket to supreme happiness. It generates genuine philosophical enquiry about the world enabling us to achieve the best mode of life, an emulation of heavenly divine life. The language of the Timaean text is expressly purposive (47b5–6).⁷⁶ The goal of vision is the contemplative emulation of the revolutions of the heavenly spheres by the intellect. The function of vision is in turn embedded in a global teleological framework (69a): the animal species are necessary for the human species to appear (90e–92c); vegetation is necessary to maintain the human body (77a–c); the human body is necessary for the rational soul to remain on earth (69c; 89d); sight is necessary for the soul to find its way back to heaven (90a). But to do this, sight needs light (45b–46a). In this global teleological scheme, it takes only a small interpretative step for the Timaean exegete to infer that light is an instrument of sight—a purely oculocentric thesis that is not explicit in the Timaeus itself. Indeed, we find the instrumental role of light articulated in the later interpretative tradition, of which Philo was part.⁷⁷ It is only natural that in his hexaemeral adaptation of the Timaean theme Philo makes the oculocentric premise explicit: Knowing that light was the most excellent of things that exist, he [sc. the Maker] produced it as an instrument for the most excellent of the senses, sight. (Opif. 53 tr. Runia)

The encomium of sight was one way of expressing the teleology of creation. Another way was to consider humankind as the goal towards which the structure of the world was directed. This anthropocentric focus of natural teleology had an equally long prehistory of philosophical discussions. The thread goes back to

⁷⁵ See on this Runia (1986), 270–6; Runia (2001), 200 (§53) and 201 (§54). ⁷⁶ On the teleological language of the encomium see Nightingale (2016), 58. ⁷⁷ See Philo, Abr. 158–9; Apuleius, Plat. I.10; Calcidius, In Tim. 244. Runia (1986), 274, commenting on the additions brought by Philo to the Timaean encomium of sight, remarks: ‘Philo shows an unashamedly anthropocentric tendency which goes further than Plato would allow (cf. Laws 903c). The heavenly bodies have been created for the specific purpose of providing light and ministering to sight (Abr. 158, cf. Opif. 77).’

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Anaxagoras as well as to Xenophon’s Socrates and Aristotle, as David Sedley has recently shown, and is transmitted to Philo via Stoic adaptations.⁷⁸ In its Stoic version anthropocentric teleology means that the world is a product of divine benevolence whose ultimate beneficiaries are its human and divine residents. Since the divine residents of the world are already good and happy, it is only human beings that need to strive towards these same goals. The world is therefore designed to provide systematic support in their quest. Food, health, and eyesight are part of the supporting mechanism and that puts the whole vegetative and animal realm together with the sun, the moon, and the stars in the game (global teleology).⁷⁹ That is precisely the idea behind Philo’s second aforementioned passage, the exegesis of day six (Opif. 77–8).⁸⁰ In addressing the apparently disputed question of why God created human beings last, Philo’s answer is Stoic anthropocentrism adapted to fit in biblical dress. God designed everything so that when humankind came to be all of nature’s supporting system would be in place. So for the living being which was dearest and closest to him in nature he [sc. God] made everything ready in advance, it being his will that once the human being had come into existence, he would lack nothing that was required both for life and for the good life, the former furnished by the abundant supply of things that give enjoyment, the latter by contemplation of the heavenly realm, which strikes the intellect with wonder and engenders in it the passionate desire to gain knowledge of what it observes. (Opif. 77 tr. Runia)

Philo also supplied three celebrated images to illustrate the anthropocentric teleology of his hexaemeral exegesis: the world as a cosmic banquet; the world as a cosmic stadium; and the world as a cosmic theatre. In all three images everything needs to be prepared before the guests or the spectators arrive. Only then can the meal, the games, or the drama begin (Opif. 78). We can see how this anthropocentric teleology promotes the oculocentric thesis. All light, from primordial light to the light of the sun, the moon, and the stars, is so designed to support the human species in attaining its final goal. The achievement of the goal passes through contemplation which, in turn, requires the faculty of sight.⁸¹ ⁷⁸ See Sedley (2007). ⁷⁹ See Sedley (2007), 231–2. ⁸⁰ I here extend Sedley’s interpretation of Stoic anthropocentrism to Philo. For a less charitable interpretation of Philonic and subsequent Christian anthropocentrism, according to which ‘animals as inferior beings are subject to man’, see, e.g., Floridi (1997), 37. Such interpretations still echo Lynn White’s (1967) negative valorization of biblical anthropocentrism. As Harrison (1999), esp. 90–6, has shown, however, such interpretations fail to see that patristic hexaemeral exegesis emphasized the moral-allegorical interpretation of Gen. 1:28, seeing in the ‘dominion over the earth’ the ‘dominion of the rebellious beasts within’. I am here claiming that the same charitable interpretation of hexaemeral anthropocentrism is possible even without finding recourse to allegorical exegesis. ⁸¹ But cf. Opif. 84: All the creatures in the sublunary realm are subordinated to the human being ‘excluding the creatures of heaven’. See also Runia (2001), 248 (§77.2): no human dominion over the heavenly realm. In my opinion, Philo’s anthropocentrism must be mitigated as regards heavenly light,

   

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Philo’s anthropocentric teleology was destined to have a long-lasting career in hexaemeral literature. We find it right at home in the Origenian tradition. The anthropocentric interpretation is manifest in Origen’s hexaemeral Homily on Genesis, which is an exercise in moral allegory. In transforming the creation narrative into a narrative about our inner progress towards perfect rationality, instantiated in our union with Christ, Origen integrates fully the anthropocentric agenda in his hexaemeral exegesis.⁸² The whole universe is tuned to support our encounter with Christ. In his homily, Origen combines Christocentric allegory with an anthropocentric interpretation of the luminaries in heaven: As those lights of heaven which we see have been set ‘for signs and seasons and days and years’, that they might give light from the firmament of heaven for those who are on the earth, so also Christ, illuminating his Church, gives signs by his precepts . . . (Hom. Gen. I.6 GCS 7.24–8.2 tr. Heine)⁸³

The anthropocentric interpretation of the hexaemeral narrative is also manifest in Didymus’ Commentary on Genesis, which exhibits evident traces of Philonic and Origenian thought.⁸⁴ Two convergent themes run through Didymus’ hexaemeral exegesis: the grand design underlying the cosmos and the perpetual moral progress of humankind in achieving ‘Christlikeness’. The two themes are revealed as the reader contemplates the number symbolism and narrative sequence (akolouthia) of Scripture.⁸⁵ The implicit but clear suggestion is that the sacred text functions as the literary mirror image of the cosmos—a leitmotif that runs

because a different view would undermine the contemplative needs of angels/daemons, who are the proper residents of the heavens; see Runia (2001), 256 (§84), further Gig. 6–18, with the commentary of Winston and Dillon (1983), 235–44, and the essay of Dillon (1983), 197–205. Consequently, light cannot be fully subordinated to human sight. Its final goal is to serve both human and angelic vision, as already discussed. Only with this caveat can Philo subscribe to the anthropocentric interpretation of light. The same is also true for the hexaemeral authors discussed in the rest of this section. ⁸² See Hom. Gen. I.11 GCS 13.18–23; I.12 GCS 14.5–6: the whole world anticipated the coming of humankind, for which it was created. The position is argued extensively in CC IV.74–99. ⁸³ But cf. I.12 in fine: equal honour of humankind with the luminaries in the sky, esp. the sun and the moon. See also CC IV.77: humankind is only one class of rational beings served by the light of the sun and the moon, the other class being angels or daemons. But in the same passage Origen allows for an alternative interpretation according to which the sun and the moon serve exclusively rational beings in the sublunary, i.e. humankind, while rational beings in the supralunary do not stand in the same position as regards day and night (presumably because they are served by the light of the stars). Origen’s double interpretation is another piece of evidence, next to the ambivalent interpretation of the Timaeus, that one could argue both ways for the anthropocentrism of the light of the sun. Be that as it may, the anthropocentrism of heavenly light (which is not limited to the light of the sun) is mitigated by the needs of the heavenly residents of the universe. ⁸⁴ See Nautin and Doutreleau (1976), 22–4; Runia (1993), 197–204; and now the detailed study of Rogers (2017). ⁸⁵ On the ‘numerical logic’ underlying both narrative sequence and cosmic order see the brilliant paper of Coogan (2023).

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     

through Philo’s and Origen’s hexaemeral exegesis.⁸⁶ Didymus’ sublunary world is teleological (‘nothing was created in vain’ 42.10) and made ‘to meet human needs’ (33.11–14; 42.5–10; 67.14–68.3). Humankind, being made in God’s image, is a governor (archon) ruling over all terrestrial life forms (57.10–13).⁸⁷ The stars in the sky have the task (ergon) of illuminating the earth, separating day from night, and revealing (phanerountes) the measures of time—an anthropocentric labour (36.16–37.1). At a higher level, the purpose of the stars is to reveal the cosmic design and beauty of creation and in so doing lead anagogically, through contemplation of the heavens, to the knowledge of God (74.9–17). Didymus’ universe is anthropocentric and fine-tuned. The images that Didymus uses to express this global fine-tuning are those of a cosmic choir or an army (68.9–18; 74.17) but also of a city or kingdom in which the creator God is governor and king (57.10–13).⁸⁸ The torch of anthropocentrism is next passed on to the Cappadocians, who had direct knowledge of Origen’s and most probably also of Philo’s hexaemeral work.⁸⁹ Basil’s Hexaemeron here lays the groundwork. The homilies manifest a Philonic anthropocentrism to which they add an Aristotelian teleological framework.⁹⁰ The whole work is based on Basil’s adaptation of Aristotle’s leitmotif that ‘nature does nothing in vain’. This is given in the first and the last homilies, which develop the Aristotelian theme in a twofold meaning: the first homily suggests that the teleological principle is part of a global teleological scheme.⁹¹ ⁸⁶ For Philo see Runia (2001), 106–7; for Origen and the Church Fathers see Blowers (2008b), 147–76. Conversely, the world functions as a macrocosmic book; see Schott (2015); and in a hexaemeral context Creat. hom. II.4.19–23 (SC 160, 234 = GNO 45.14–46.2). It is the early Christian idea of the ‘book of nature’, for which see the comprehensive study of Juurikkala (2019). ⁸⁷ The imagery is distinctively Philonian; see Opif. 83: hēgemona kai despotēn of the animals; Opif. 84: basilea of the sublunary. ⁸⁸ City or kingdom per implicationem since God is governor and king (archon kai basileus) of the universe. The imagery is again characteristically Philonian; see Opif. 17. ⁸⁹ For teleology as the culmination of the apologetic agenda of Cappadocian natural theology see the magisterial Gifford Lectures of Pelikan (1993), 152–65. On the influence of Philo on the Cappadocian hexaemeral project see the study of Runia (1993), esp. 235–41 (Basil), 241 (Nazianzen), 251–6, 261 (Nyssen). This does not mean, however, that the reception was uncritical, as two seminal studies have recently shown: see McGuckin (2005), 38–54; Bouteneff (2008), 121–68. When I speak of PhilonicOrigenian influence henceforth I fully side with Zachhuber (2014), 163–74, who has argued that Gregory’s De opificio hominis attempts ‘to offer a modified Origenism sustainable under the requirements of late fourth century orthodoxy’ (p. 173). In my view, this holds true for the Cappadocian hexaemeral project on the whole. ⁹⁰ For an excellent recent defence of Basil’s anthropocentrism see Costache (2013b). On the vexed question of Basil’s sources see the survey of the discussion in Köckert (2009), 322–4, 323 (Aristotle: at least mediated if not direct knowledge), 323–4 (Philo: with reservations). I do not see any reason for reservations as regards the use of Philonic material, as attested by all specialists; see Giet (1968), 49–51; de Mendieta (1985), 364–5; Runia (1993), 237–8, 241. The only (unanswerable) question is whether Basil’s knowledge of Philo is mediated or not. Regarding the use of Aristotelian material the answer seems easier. As Edwards (2019), 97, suggests, Basil’s ‘education in Athens afforded the best opportunities for the first-hand perusal of Aristotle’. ⁹¹ This is very controversial in Aristotelian scholarship, but not indefensible; see Sedley (1991), 179–96, with the status quaestionis on p. 179 and an update on the debate in Sedley (2007), 197 n.55. In order to explain his anthropocentric interpretation of Aristotle’s teleology Sedley borrows his paradigm from Stoic cosmology; see pp. 179–80. In my view, so does Basil; see Hex. I.6 GCS 11.7–13 tr. Way

   

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The ninth homily contains the applications of the principle for the local teleology of plants and animals.⁹² In between we are given to understand that the purpose of the hexaemeron is the anagogical contemplation of the world. Contemplation will lead us to the sublunary and the study of the teleological structures of all terrestrial life forms culminating in the human being, following Aristotle’s biological programme (Homilies VII to IX). But before focusing on the microcosm, contemplation will pass through the supralunary and the vision of ‘the indescribable beauty of the stars’, according to the Platonic paradigm (Homily VI).⁹³ Basil’s world is a teaching ground (didaskaleion) of divine pedagogy.⁹⁴ From a global teleological point of view, even the celestial bodies with their light are in the service of humankind. The point is made explicit in Basil’s exegesis of Gen. 1:14, following the Origenian interpretative tradition.⁹⁵ It is also made in the exegesis of Gen. 1:4 at the end of Basil’s lyric encomium of light, whence comes also the following quotation: ‘And God saw that the light was good’. What could we say that would be worthy praise of light which beforehand possesses from the Creator the testimony that it is good? Among us speech reports the judgment made by the eyes; even so, it is unable to say anything at all as great as our senses previously have borne witness to. But, if beauty in the body has its being from the symmetry of its parts with each other and from the appearance of beautiful colour, how, in the case of light,

(modified): ‘[You will find that] there was some creative (technikos) logos directing the orderly arrangement of visible things, as the word “archē” shows you. Moreover, you will find that the world was not devised at random or to no purpose, but to contribute to some useful end and to the great advantage of all beings, if it is truly a training place for rational souls and a school for attaining the knowledge of God, since through the experience of visible and sensible things the mind is led, as by a hand, to the contemplation of invisible things . . .’ ⁹² In an influential article James Lennox has argued Aristotle’s teleological maxim has two contents. The negative content explains the absence of a feature, while the positive content explains the presence of a feature; see Lennox (2001). This seems to me to be the position of Basil in Hom. IX.5 GCS 155.1–2 tr. Way: ‘If you observe carefully the members even of the animals, you will find that the Creator has added nothing superfluous, and that He has not omitted anything necessary.’ ⁹³ The theme of contemplation of the universe preoccupies mainly (but not only, see e.g. Hex. I.7 GCS 12.16–17) the opening of the sixth homily, where we also find three celebrated hexaemeral Philonic images entailing anthropocentric teleology: the word as stadium, as theatre, and as a great city. The positive use of philotheamōn (VI.1 GCS 88.1) is in a way Platonic (see Rep. 475e) though the negative connotation is more characteristic of Plato (see Rep. 475d, 476ab, 479a: lovers of sights—and sounds—incapable of contemplating the forms); see Nightingale (2016), 59–60. In Plotinus the original Platonic ambivalence is retained since the term denotes neutrally the contemplative nature, while the positive or negative outcome of contemplation depends on its direction; see Enn. III.8.4.5, 15–35. The positive use of philotheamōn in the specific context of philosophic contemplation of the heavens, as here, seems to be Middle Platonic; see Plutarch Curios. 517D1 (see further positive uses in Pyth. or. 394F3; Quest. conv. 673B6), and most notably Philonic; see Opif. 158; Her. 79; Spec. III.191. ⁹⁴ An Origenian insight; see Köckert (2009), 307, 318. For Basil see Costache (2013b), esp. 110–22; Blowers (2016), 10–13. ⁹⁵ With Origen’s exegesis of Gen. 1:14 in the background (Metzger fr. D7), Basil stresses the usefulness (chrēsimous, to ōphelimon VI.4 GCS 94.9, 95.12) and service (etachthēsan VI.8 GCS 103.19) of the luminaries but refrains from subordinating them entirely to humankind.

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      which is simple in nature and similar in parts, is the idea of beauty preserved? Or, is it that the symmetry of light is not evinced in its individual parts but in the joy and pleasure at the visual impression? In this way even gold is beautiful, which holds an attraction and pleasure for the sight, not from the symmetry of its parts, but from the beauty of its colour alone. And the evening star is the most beautiful of the stars, not because the parts of which it was formed are proportionate, but because from it there falls upon our eyes a certain joyous and delightful brightness. Then, too, the judgment of God concerning the goodness of light has been made, and He looks not wholly at the pleasure in the sight but also looks forward to the future advantage. For, there were not yet eyes able to discern the beauty in light. (Hex. II.7 GCS 33.6–22 tr. Way)

The whole world, then, beginning with the first light, anticipates the advent of humankind. So also does Basil’s audience, which is gradually led to realize that day six is the apex of creation’s grand design. But that is where the homilies come to a rushed end, with an unfulfilled promise to return to the creation of humankind in more detail at a later moment (Hex. IX.6 GCS 160.14–15). Whether the promise was ever fulfilled is a vexed question in Basilian scholarship. There are three possible places to look for an answer: 1) the De hominis opificio of Gregory of Nyssa;⁹⁶ 2) two homilies De creatione hominis of Basilian inspiration, to which occasionally a third homily is added in the manuscript tradition;⁹⁷ 3) the Basilian Homily 319 on the words attende tibi ipsi (Deut. 15:9).⁹⁸ Each of these works adopts an explicitly anthropocentric agenda with strong echoes of

⁹⁶ Gregory himself claims in the preface that the work was written in fulfilment of Basil’s promise; see Forbes (1855), 104 (= PG 44:125C). ⁹⁷ The current scholarly consensus is that the three homilies contain Basilian material which was edited later, i.e. after Basil’s death, from within his immediate circle in fulfilment of the said promise (Hex. IX.6 GCS 160.14–15); see the detailed argumentation of Smets and van Esbroeck (1970), 13–134, and the similar assumption of Hörner (1972), vii–ix. Working independently, the editors of the two available critical editions concur. In spite of initial contrary reactions, the hypothesis of underlying original Basilian material has gained wide acceptance in scholarship; see de Mendieta (1973), 713–16; Rousseau (1994), 318–63, esp. 318 n.1; Bouteneff (2008), 136–7; and now van Esbroeck (2018), 224–5, with a summary of the debate. The issue is thus settled, even though not in the most satisfactory way; see Fedwick (1996), 1201–2, classifying the work in its transmitted form among spuria et alia but accepting the argument of Smets and van Esbroeck. The remaining question is the extent of the intervention of the editing hand(s). ⁹⁸ Gronau (1914), 3–4, 281–93, suggested that this was Basil’s ‘tenth hexaemeral homily’, based on the excurse in Hex. IX.6 GCS 157.22–6 and the content of Hom. 319. The intertextual evidence is too strong to overlook Gronau’s suggestion. Basil, Gregory, and Ambrose all refer to the ‘attende tibi ispsi’ in order to show that contemplation of nature culminates in contemplation of the self; see Basil, Hex. IX.6 GCS 158.1–10; Gregory, Hom. opif. XXIX Forbes 290.9–10 (= PG 44:237D–240A); Ambrose, Exam. VI.6.39, 7.42. This exegetical strategy can best be explained with Hom. 319 in the background. Though I do not go as far as to embrace Gronau’s view, since the tenth homily was never written, I tend to think that Hom. 319 is the common material behind Gregory’s De hominis opificio and the Basilian De creatione hominis. The interconnection needs further investigation.

   

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Philonic-Origenian thought.⁹⁹ I shall concentrate briefly on Basil’s Homily 319 here, which contains material used in both Basil’s and Gregory’s hexaemeral work. The homily builds on Deut. 15:9 as the biblical adaptation of the Delphic adage ‘know yourself ’, though perhaps Deut. 4:9 would have been a more adequate biblical locus to deliver the same message. From a hexaemeral point of view, the homily exploits the idea that the human being is a ‘little world’ (mikros diakosmos, PG 31:215–16 = Rudberg 35.15).¹⁰⁰ This gives rise to the broader idea that contemplation of the world culminates in contemplation of the self. The expression and the argument bring immediately to mind the macrocosm/microcosm analogy, which in a hexaemeral context is further evidence of Philonic-Origenian inheritance.¹⁰¹ It is therefore no surprise that the homily contains perhaps the fullest expression of Cappadocian anthropocentrism. Heavenly light is part of this anthropocentric hexaemeral world. It is worth quoting in extenso: . . . you are a human being, the only one of the animals formed by God. Is this not enough to be reasonable grounds for the most exalted joy, that you have been entirely formed by the very hands of God who has made all things? That since you have come into being according to the image of the Creator you can ascend quickly toward equality of honour with the angels through good conduct? You have been given an intellectual soul, through which you comprehend God, you perceive by thought the nature of beings, you pluck the sweetest fruit of wisdom. All the land animals, domesticated and wild, and all those living in water, and all those that fly through the air, belong to you as slaves and are subject to you. Further, have you not invented arts, and built cities, and devised all the things pertaining to necessity and luxury? Are not the oceans passable for you through reason? Do not earth and sea serve your life? Do not air and sky and dancing stars disclose to you their pattern? Why then are you downcast because your horse does not have a silver-mounted bridle? Yet you have the sun carrying its torch for you in a swift race through the whole day. You do not have the luster of

⁹⁹ The point is well argued in two influential studies at the beginning of the previous century; see Robbins (1912), 4–6, 56–7, with more emphasis on teleology; and Gronau (1914), 146–73, 281–93, with convincing evidence, with the exception of the now dated thesis that Posidonius’ Timaean Commentary was the underlying common source. Gronau’s view is reprised by Runia (1993), 253, as regards Gregory of Nyssa. The Philonic influence on the Creat. hom., probably through Origenian mediation, is also affirmed by Runia (1993), 240–1. ¹⁰⁰ A common Cappadocian doctrine; see Creat. hom. II.14.17 (SC 160, 266 = GNO 65.13–14); Nazianzen, Orat. 38.11 (In theophania), see further Pelikan (1993), 121–3, on the influence of Macrina. On the seemingly ambivalent stance of Nyssen see Zachhuber (2014), 167, 234 n.16. ¹⁰¹ See e.g. Philo, Opif. 25, 69, 82; Origen, Hom. Gen. I.11 GCS 13.21–2. On the analogy in Philo see Runia (2001), 227 (§69.2a), 254 (§82); for Origen see Köckert (2009), 267. The most comprehensive treatment of the subject is still the monograph of Conger (1922), esp. 29–37, with a survey of Christian microcosmic theories. For the late antique context of the analogy see the captivating essay of Chin (2015).

46

      silver and gold, but you have the moon with its limitless light shining around you. You have not mounted a chariot inlaid with gold, but you have feet as a vehicle proper and adapted by nature to yourself. Therefore, why do you call happy one who has a fat purse but needs the feet of others to move around? You do not lie on a bed of ivory, but you have the earth which is more valuable than great amounts of ivory, and your rest upon it is sweet, sleep comes quickly and is free from anxiety. You do not lie beneath a gilded roof, but you have the sky glittering all around with the inexpressible beauty of the stars. (PG 31:212–13 = Rudberg 33.5–34.6 tr. Harrison)

The torch of anthropocentrism is further passed on to hexaemeral authors that were further influenced by Basil’s thought. The thread leads to Ambrose,¹⁰² Chrysostom,¹⁰³ and beyond. But I will draw a line here because I think the point has been made adequately clear that anthropocentric teleology is ubiquitous in hexaemeral thought.¹⁰⁴ It is time to draw some conclusions. On the basis of the above collection of passages it is evident that the anthropocentric interpretation of the hexaemeron puts light in the service of humankind. By rendering light an instrument of sight, hexaemeral anthropocentrism promotes the oculocentric thesis in a double respect. Celestial light enables the contemplation of the sublunary world, allowing us to perceive its teleological hierarchy and structure. But celestial light is at the same time the most beautiful object of contemplation in the world, instructing us in the immeasurable beauty, power, and creative genius of its divine artificer. In both respects, light becomes the medium and the apex of the contemplative work. It must be noted, however, that hexaemeral anthropocentrism is only one side of the story. The other side is the theocentric hermeneutics of creation since anagogical knowledge of God is the sole purpose of the contemplative work. In between hexaemeral theocentrism and anthropocentrism stands the image of God. This image, visible in the person of Christ, brings the two hexaemeral opposites to a harmonious balance.¹⁰⁵ The new story of creation becomes the

¹⁰² Just indicatively, see Exam. VI.1.2: the world as theatre; VI.5.30–35: teleological explanation of animals and their parts—nothing was created in vain; VI.6.39 and 7.42: attende tibi ipsi. ¹⁰³ Again, only as a foretaste, see Hom. Gen. VI.6 PG 53:61a: encomium of sight; VII.3–4 64d–66a: design argument—rejection of materialism—nothing was created in vain; VII.6 67c–68a: human authority over the sub- and the supralunary; 67d: image of creation as a banquet; VIII.3 72d: human authority over everything on earth. ¹⁰⁴ See the excellent survey of Steiner (2005), 112–31. ¹⁰⁵ The complementarity of ‘theocentric anthropology and anthropocentric cosmology’ in patristic thought, culminating in Christology, has been wonderfully argued by Meyendorff (1983), 34–6. It has been recently vindicated as the axis of the Origenian tradition in its multiform expressions by the monumental studies of Behr (2017) and Williams (2018). On the Christocentric transformation of teleology in patristic literature see the magnificent essays of Pelikan (1993), esp. 280–95; Blowers (2012); further Knight (2007), with a special focus on Maximus the Confessor. Theokritoff (2008), 70–1, rightly remarks that patristic ‘anthropocentrism’ should not be confused with the modern notion

 

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story of the union of the human with the divine logos. Christ—the logos incarnate—becomes the meeting point of the two hermeneutical axes of creation, theocentric and anthropocentric.¹⁰⁶ As Christ fulfils his earthly mission and ascends into heaven, the microcosmic (‘local’) teleology of the sublunary finds its culmination point in the macrocosmic (‘global’) teleology of the supralunary. With their anthropocentric and teleological interpretation of the creation narrative the hexaemeral authors initiate the reader into a vision of double anticipation: the whole universe anticipates the coming of humankind just as humankind anticipates the coming of Christ. The hexaemeron then revisits anthropocentrism and proposes instead a Christocentric teleological scheme for the interpretation of the world. If so, salvation history begins with eyesight: contemplation of nature reveals the forthcoming image of God. Remember here the previous two oculocentric arguments discussed above: angel-sight and celestial eyes. They now reveal their true purpose. Angelic and cosmic vision need to be integral parts of the hexaemeral narrative because the heavenly beings participate fully in the emergent cosmic theology: all rational creatures, from angelic and celestial beings reigning in heaven to the human being reigning on earth, are made to contemplate the cosmos and in so doing to be instructed in creation’s true telos, the incarnation of the logos. Humankind is only the last thread in a great chain of rational beings, to reprise Lovejoy’s celebrated theme, which is instructed in the universe’s deeper secret. Angels together with the stars are anticipating Christ from the beginning of time (or very close to that). That seems to be what the hexaemeral narrative is all about. A genuinely oculocentric narrative then it is.

1.4 Rethinking Oculocentrism 1.4.1 Narrowing down the Scope The oculocentric thesis offers a powerful hexaemeral narrative. So compelling that one hesitates before suggesting contrary evidence. But the close study of the sources raises pressing questions, with perhaps surprising answers. Take Philo’s appropriation of the Timaean ‘encomium of sight’, for example. David Runia has of anthropocentrism as ‘a human self-centredness altogether incompatible with theocentric anthropology’. But the contemplative-anagogical programme of the hexaemeron culminating in the Christocentric hermeneutics of creation clearly rules out such a possible misunderstanding. ¹⁰⁶ This point is best expressed in the Johannine literature. As Endo (2002) has meticulously shown, the Johannine Prologue is written from the background of a Christological reinterpretation of the biblical creation narrative. It is the same Christological vision of creation that animates all patristic light imagery; see Wallraff (2001), 41–59. This idea is magisterially expressed in Origen’s allegorical interpretation of light in his hexaemeral (first) Homily on Genesis. That means that Origen’s (allegorical) reading of Gen. 1 through the lens of John 1 is no Origenian fancy, but a reading of Genesis based on genuine Johannine premises, as van Kooten (2005) has skilfully shown.

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     

meticulously compared the Philonic (Opif. 53–4) and the Timaean (47a–c) versions and shown several key differences beyond the striking similarities.¹⁰⁷ The first difference is that the Timaean version is an encomium of sight, while the Philonic version is an encomium of sight and light, importing extra material from the Republic (507–9). In assessing the special weight of the two themes (sight and light) in their Philonic synthesis, Runia remarks that ‘the encomium of sight is subordinated to the encomium of light’.¹⁰⁸ But the oculocentric thesis insists that it ought to be otherwise. First need for qualification. By the time of Basil, the subordination of light to sight is almost complete. The relevant passage from Basil’s Hexaemeron (II.7 GCS 33.6–22, quoted above in extenso) shows that Basil has almost entirely replaced sight with light. The Basilian exegesis of Gen. 1:14 is a genuine encomium of light, to which sight is the instrument of perception. Sight is clearly subordinated to light. Second need for qualification. But when Philo and Basil are in accord, there is little room for manoeuvre. In the hexaemeral traditions that Philo and Basil represent sight becomes subordinated to light. These two traditions cover the whole spectrum of early Jewish-Christian hexaemeral exegesis. What varies in between is not the relation (‘if ’) but only the degree (‘how much’) of subordination. Third need for qualification. As regards the ‘encomium of sight’ all evidence speaks for its transformation into an encomium of light, in which sight plays the auxiliary part. Or, take the anthropocentric teleology of the hexaemeral worldview as a second example. From the point of view of global teleology light’s place in the world seems to be auxiliary to vision, supporting its final goal: contemplation of the world. But here, too, qualification is needed. In the grand scheme of the All, sight is only a means to an end, a necessary but not sufficient condition of contemplation. Even animals have the ability to form images looking at the sky, though they are not able—as far as we know—to infer the existence of God. Theistic proofs, like the ‘cosmological argument’ and the ‘argument from design’, require a rational agent able to infer, through the processing of sensory facts and events, a first cause. ‘Contemplation of the world’ then is a process extending over several perceptual and cognitive steps, the formation of images through vision being only the initial one of them. But it is the whole process that the hexaemeral authors have in mind when they speak of the world as a teaching ground. The goal of sight in the hexaemeron, following the Timaean tradition, is not exhausted in vision, i.e. the raw sensory input from the visual organ. The goal of sight is to serve as springboard for the reflective process to begin (with or without the combination of the other senses). In other words, ‘contemplation’ is reflective vision, according to the formula ‘sense perception + a logos account’. In a global teleological scheme, ¹⁰⁷ See Runia (1986), 270–6, 354. ¹⁰⁸ Runia (1986), 271. And now decisively: ‘The emphasis [sc. in Philo’s encomium] is placed on the role of light rather than of sight (as in Plato)’, Runia (2015), 189.

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then, light does not stop at the level of the formation of visual images. Its ultimate goal is to enable reflection and in so doing to disclose the beauty, order, and intelligent design of the world. In this respect, light serves a greater purpose: it reveals to the contemplative eye the demiurgic divine attributes underlying the cosmos. In other words, light is not for the sake of the eye but for the sake of the reflective beauty and goodness of the All. The above qualifications narrow down the field of application of pure oculocentrism considerably. Once the global perspective is taken out of the equation what is left is the role of light in local teleology, i.e its role in the proper function of the organ of sight. Remember that the three oculocentric moves discussed above, namely angelic, celestial, and human sight, require some (more or less exotic but nonetheless physicalist) faculty of vision. Remember also that the mechanism of vision is the focal point of the current discussion in the history of optics. In the soft oculocentric version of Smith light plays an auxiliary role in vision. In the strong oculocentric version of Simon light is co-extensive with sight. Oculocentrism then can be narrowed down to the role of light in the mechanism of vision. The theory of vision is the testing ground on which the oculocentric hermeneutics of hexaemeral light stands or falls.

1.4.2 Sight Is Light The theories of vision underlying hexaemeral literature have not yet been the object of study in contemporary scholarship. But we are not left entirely without a clue. In a seminal paper David Hahm has prepared the ground by sketching the contours and providing many details of the theoretical framework that was available to the hexaemeral authors.¹⁰⁹ Hahm’s study identifies three major Hellenistic theories of vision which, according to the author, remain essentially the same throughout antiquity. They are also the major theories available to the hexaemeral authors: From the Hellenistic period down through late antiquity three distinct theories of vision competed for attention—namely, those of the mathematicians, the Epicureans, and the Stoics. By the first century B.C. these three theories had eliminated all earlier competitors. A fragment of an optical treatise attributed to Geminus (first century B.C.) states that optics is not concerned with the physics of vision, but only demands that the rectilinear propagation of light or vision be preserved. Hence optics does not decide whether 1) ‘rays are poured out from the organs of sight and effluences travel to the surfaces of objects, or 2) images

¹⁰⁹ See Hahm (1978), 60–95.

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      (eidōla) streaming off from perceptible bodies in rectilinear motion penetrate the eyes, or 3) the intervening air [between the object and the eye] is extended together with, or carried along with (sunekteinetai ē sunekferetai), the raylike pneuma of the eye’. Apparently, these three theories were the only options a student of optics had to consider.¹¹⁰

Hahm’s argument proceeds in three steps. It gives a survey of the three theories of vision just mentioned.¹¹¹ It concludes with the investigation of the corresponding theories of colour.¹¹² In between, it discusses at length the Timaean theory of light and colour¹¹³ ‘because it provides the background against which the Hellenistic theories of vision had to work’, since ‘each of the Hellenistic theories shows an influence of its basic assumptions’.¹¹⁴ If Hahm is correct, the Platonic Timaeus is the common theoretical background of Hellenistic and late antique theories of vision. At the same time, however, as we know from the landmark studies of David Runia (1986) and Charlotte Köckert (2009), the Timaeus, in its reception, is also the major philosophical influence behind hexaemeral literature. And as I have argued up to now, the Timaeus and its interpretative tradition is how oculocentrism crosses the doorstep of the hexaemeral world.¹¹⁵ Connecting the threads, Hahm’s suggestion about the background influence of the Timaean theory of vision on Hellenistic and late antique sources can be extended and applied to the hexaemeral sources as well. Let us then find out what this influence means in practical terms. The Timaean theory of vision is based on the combination of three different streams of fire or light. It is summarized by Thomas Johansen as follows: Our light-bringing eyes (phōsphora ommata) were composed of the same sort of fire as daylight. This is a special sort of fire that does not burn but spreads ‘a gentle (hēmeron) light proper to each day (oikeion hekastēs hēmeras)’ (45b4–6: clearly a pun). The pure fire inside us is ‘a brother’ (adelphon) of the daylight of each day. The fabric of the eyes is fine so that only this pure fire will be let through. Whenever daylight (methēmerinon phōs: the punning continues) surrounds the stream of pure fire coming from the eye, like falls upon like (homoion pros homoion) and the two bodies of light coalesce. They become one body reaching out in a straight line from the eyes. Because the entire ray of light is similar (made of the same sort of fire) it becomes ‘sympathetic’, capable of being affected in a similar way. So whenever the ray hits upon an object and is affected by it, the affection spreads along the ray into the body all the way to the rational

¹¹⁰ Hahm (1978), 61. ¹¹¹ Hahm (1978), 61–9. ¹¹² Hahm (1978), 75–88. ¹¹³ Hahm (1978), 69–75. ¹¹⁴ Hahm (1978), 75. ¹¹⁵ The Jewish-Christian reception of the Timaeus thus created a particular school of interpretation; see Niehoff (2007), 170–91.

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soul in the head. It is this affection which we call vision. The kinship between the outer and inner light is further emphasized when Timaeus explains why vision does not happen when the light disappears at night. The pure fire coming from the eye then meets with darkness outside and is thereby cut off from its related (suggenous) fire. Meeting what is unlike (anomoion), the fire from within is extinguished. It is no longer sumphues, congenital with, the adjacent air. So vision can no longer take place.¹¹⁶

The Timaean theory of vision is based on the combination of three streams of light: the visual ray, daylight, and the colour perceived, commensurate with the visual ray. Timaean sight then is the coalescence of streams of light emanating from three different sources: the eye, the source of illumination of the surrounding environment, and the object of vision. In other words, Timaean sight is luminocentric: it is the coalescence of light with light. The fact that the Platonic theory of sight is luminocentric is attested also elsewhere in the Platonic corpus. We find it explicitly stated in the celebrated ‘sun simile’ in the Republic, where sight is described as being causally dependent on the sun (aitios) and thus the most ‘sunlike’ (hēlioeidestaton) of the senses (and not the sun being ‘eye-like’, 508a11–b11). The Timaeus and the Republic both affirm the affinity of sight with light. The Republic causally subordinates sight to light, while the Timaeus explains the reason of this subordination: sight is the coalescence of light with light.¹¹⁷ The luminocentric nature of the Platonic theory of light is constantly affirmed in the interpretative tradition. We find it clearly stated in a much-discussed fragment from Posidonius’ theory of vision, echoing the Timaeus: And as light, says Posidonius in expounding Plato’s Timaeus, is grasped by sight that is luminous (phōtoeidous opseōs) and sound by hearing that is airy, so too the nature of all that there is should be grasped by the logos that is akin to it. (fr. 85 tr. Kidd)

We find the same doctrine, together with the Posidonian terminology of ‘photoeidēs’, in Alcinous’ summary of the Timaean theory of vision: Having placed upon the face the light-bearing eyes (phōsphora hommata), the gods enclosed in them the luminous aspect of fire (tou puros to phōtoeides), which, since it is smooth and dense, they considered would be akin to the light of the day. (Didaskalikos 18.1.1 tr. Dillon) ¹¹⁶ Johansen (2004), 110–11 (transliterations in the original). ¹¹⁷ On the luminocentrism of opsis in the Republic see the epoch-making doctoral thesis of Beierwaltes (1957), 40–3. See also Ferguson (1921), 132–3: ‘The sole object of this argument [sc. the analysis of sight] is to extract a single system, that of light, from the material cosmos which will serve the purpose of his [sc. Plato’s] analogy.’

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The luminous nature of sight is also constantly stressed by Plotinus. It is paradigmatically formulated in a celebrated line from Ennead I.6 (On Beauty), echoing the Republic: For no eye has ever seen the sun without becoming sun-like (hēlioeidēs). (Enn. I.6.9.30–1 tr. Gerson)

In his Commentary on the Timaeus, Calcidius summarizes the Platonist theory of vision and brings the message of its luminocentric character home clearly: The primary cause of seeing is the internal light; but it is not in every respect complete and sufficient for the performance of its apportioned task, since assistance is required from cognate external light, above all that of the sun . . . (In Tim. 244 tr. Magee)

With the above hermeneutical framework in mind, let us go back to the hexaemeral sources and have a fresh look at the Philonic ‘encomium of sight and light’ (Opif. 53–4). We find first the characteristically oculocentric premise of light as an instrument (organon) of sight. But oculocentrism gives way as we read on: the eye has need (chreios) of light in order to see; through light (hupo phōtos) sight is drawn upwards and contemplates the motions of the heavenly bodies. Recall now Runia’s lead that Philo is here combining material from the Timaeus and the Republic.¹¹⁸ It is the same line of interpretation that we have just seen in Posidonius, Plotinus, and Calcidius. We now have all the information necessary to decode the meaning of light as an ‘instrument’ of sight. The reference is clearly to the external light which activates the mechanism of vision. But this is so because of the application of the principle of ‘like to like’. External light is an instrument of sight in the sense that its coalescence with the light of the eye is the necessary and sufficient condition for vision to occur.¹¹⁹ Philonic sight then is

¹¹⁸ See Runia (1986), 274. ¹¹⁹ This needs some clarification. One might retort that ‘colour is the sole proper object of sight’, while ‘light is not per se visible’ because ‘it is a mere catalyst for visibility and becomes visible itself only insofar as it has colour—brightness being a sort of inherent whiteness’; so Smith (1996), 72 n.5, 75 n.17, in his comments on Ptolemy’s Optics II.5 and 13, following Aristotle, De an. II.6. The remark is interesting, coming from Smith, because it incites the question: what is light per se? If light is not colour but it is ‘a catalyst for visibility’ and ‘becomes visible itself ’, then light must have some physical existence independent of colour, which leads us straight into the question of the nature and properties of light as such, i.e. into the subject matter of the physics of light. Regardless of this logical concession to the ancient physics of light, the remark is simply mistaken. It rests on a confusion of colour as the perceptual object exclusively of the sense of vision (hence not of hearing, taste, smell, or touch), misunderstood as the sole immediate object of vision (so that nothing beyond colour is per se visible). Only the former is attested in the sources; see e.g. Alexander of Aphrodisias, De an. 40.20–2. By contrast, both intramissionist and extramissionist theories of vision accept that light is per se visible in the highest degree; see Alexander, De an. 44.13–4, with the brilliant comments of Caston (2012), 163–4 (= n.365 ad loc); Ptolemy, Optics II.5; II. 13; II.18; II.23; Plotinus, Enn. V.3.8.18–25. From different

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the coalescence of light with light and as such it is, typically, luminocentric. Through Philo, luminocentrism enters the hexaemeral world. Basil’s encomium of light shows that Philo’s luminocentric premise is still valid even when Philo’s name is no longer mentioned explicitly as a source of information. Thus, in a remarkable passage, Gregory of Nyssa confirms that the same luminocentric premise that is operative in Posidonius, Plotinus, and Calcidius also explains the Cappadocian theory of vision:¹²⁰ The eye enjoys the light by virtue of having light within itself to seize its kindred light, and the finger or any other limb cannot effect the act of vision because none of this natural light is organized in any of them . . . (Infant. GNO III/2 79.16–20 tr. Moore and Wilson)

Let us now briefly go back to the oculocentric arguments discussed above, angelsight and celestial eyes, and compare them with the Platonic theory of sight. All of a sudden, what seemed to be an oculocentric hexaemeral world is transformed into a luminocentric universe. Take for example the angels. It is now clear that they are able to perceive the light of the stars because of the principle of likeness that explains Platonic vision. Just as in human vision the internal light coalesces with the external light that comes through the eye, so too in angel vision does the light of the stars coalesce with the light that comes through the angelic, ethereal, or astral—hence ‘luminous’—body. Take again the imagery of the sun, the moon, and the stars as celestial eyes. This is now explained through the macrocosm/ microcosm analogy, which allows the stars to become explanatory models for the mechanism of vision: just as the luminaries in heaven shed forward the light that they have inside (light ray), so too the eyes transmit the light that is inside the human body (visual ray). The metaphysical weirdness of ‘angel-sight’ and ‘celestial vision’ gives way to a much more coherent explanatory framework once we become aware of the basic premise of the Platonic theory of vision: the eye is ‘sunlike’, whether angelic or human, in the sense that it emulates the basic function of the sun, shedding its light to the world. It is a world full of light.¹²¹ For the hexaemeral authors, who, like many of the natural philosophers of their time, adopt the luminocentric premise of the Platonic visual paradigm, oculocentrism is a position very difficult to uphold. That compels me to part ways with schools, Alexander, Ptolemy, and Plotinus agree that light is causally prior to colour and primarily visible. The reason for the misunderstanding is the seemingly innocuous assumption that light has colour. Why this is not so simple, I discuss in Appendix B. ¹²⁰ The luminocentric premise of the extramissionist theory of vision remains constant in the byzantine tradition—see Betancourt (2016)—acquiring full force in the mystical tradition, which emphasizes the visibility of light as a sign of union with the divine; see the ample evidence adduced by Ware (2012), 142–58. ¹²¹ For ‘sight is light’ as a maxim of ancient extramissionist theories of vision see Bielfeldt (2016), with a fascinating example of lamps as man-made eyes in the Greek cultural imagination.

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the oculocentric thesis. From an oculocentric perspective, light is vision-dependent. Ancient optics is an analysis of sight and light is part of this analysis. From a hexaemeral perspective, however, light (Gen. 1:3–5) precedes human sight (Gen. 1:26–8), while light and sight are joined together through the global and local teleology of the heavenly stars (Gen. 1:14–19). The hexaemeral exegetes belong to a thought world which still regards the sun as a macrocosmic eye and the eye as a microcosmic sun. In this cultural paradigm, in which sight is theorized as light, the preponderance of sight is, actually, a preponderance of light and the proper analysis of sight becomes, in fact, an analysis of light and its properties.¹²² Vision becomes in this way a special field of application of the general physics of light. Yet the oculocentric view denies that there is any physics of light in the premodern optical paradigm. Clearly, the two views are worlds apart and cannot be reconciled with each other.¹²³ In the following chapters, I will proceed with my own reading of the sources and present the evidence for the physics of light that I think is abundant in the hexaemeral literature and its context. Before I do so, however, I need to say a final word about the role of vision in the premodern, hexaemeral paradigm, and its relation to light.

1.4.3 From the Phenomenal to the Noumenal Implicit in the oculocentric thesis is the modern critique of the premodern scientific paradigm. According to Smith light was part of the perceptual apparatus of the premodern mind, cognitively bound to it. Light mediated, together with colours, the subjective realization of an object in the mind through the very act of seeing. The object itself was ‘not actually there’ but ‘merely implied, or intended’.¹²⁴ The premise of ‘intentionality’ was abandoned with the transition from premodern to modern optics, a transition that was discontinuous and revolutionary, a true paradigm shift in the Kuhnian sense.¹²⁵ According to Simon, the modern paradigm introduced the notion of an ‘objective’ physical light, independent of the perceiving ‘subject’.¹²⁶ The oculocentric school, following Simon, identified the modern concept of light with ‘our’ light, i.e. with the concept of light of the contemporary reader.¹²⁷ The alienation of the contemporary reader from the premodern concept of light is the implicit assumption of the oculocentric thesis. It is an assumption with which I can find no common ground at all. ¹²² See Berryman (1998), 194–6: Euclid’s visual ray model dependent on its underlying theory of light; Berryman (2012), 201–20: from the point of view of Hellenistic and late antique natural philosophy the proper analysis of sight is subject to the study of the physical principles underlying it. See also the fragment from the optical treatise attributed to Geminus (first century ) in Schöne (1897), 22–4: from the point of view of geometrical optics visual rays are theorized as rays of light. ¹²³ For an explanation why this is so, see Appendix A. ¹²⁴ See Smith (2004), 187–94. ¹²⁵ See Smith (2010), 163–78. ¹²⁶ See Simon (1988), 25–36. ¹²⁷ See Simon (1988), 11–25; Blamont (2004), 199.

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From the point of view of the history of ideas, the modern paradigm is not itself invulnerable to criticism. Such criticism has been the task of postmodern thought, which has reinvited the premodern, participatory paradigm and reinstated it as a valid source of inspiration in contemporary discussions. The contemporary, postmodern reader may thus feel more in tune with the premodern rather than with the modern worldview.¹²⁸ The rejection of the medieval paradigm and its underlying metaphysical premise of ‘intentionality’, for example, is a curious argumentative choice made by the proponents of the oculocentric thesis. In twentieth-century philosophical discussions scholastic ‘intentionality’ has been rehabilitated through the influential work of Franz Brentano and has, since then, played a central role in both analytic and phenomenological schools of thought.¹²⁹ If the premodern optical paradigm is ‘intentional’, then so be it. The question is what we make of it. Even more curious is the strong defence in oculocentric literature of the concept of an ‘objective’ light as part of the modern paradigm.¹³⁰ The defence of scientific objectivism is surprising since post-Einsteinian physics has abandoned the presuppositions of classical physics, namely the Newtonian core assumptions of absolute space and absolute time, which enable the assertion of a straightforward objective reality of the physical world. But the notion of an ‘objective’ light is incoherent without such presuppositions. Post-Einsteinian light, on the contrary, is not ‘objective’ but ‘relational’. It is part of a quantum world in which indefiniteness, nonlocality, and entanglement or ‘togetherness’ are actual properties of particles, including photons. In the quantum world light is neither ‘here’ nor ‘there’, but ‘here–there’; it is neither wave nor particle, but ‘wave–particle’.¹³¹ Quantum properties of light, like relationality, nonlocality, and duality, are counterintuitive to the modern mind, which is trained to perceive the world through the spectacles of an ‘objective’ physical reality. But perhaps quantum properties are much less counterintuitive to the premodern mind. Late antique and hexaemeral physics assumed physical properties of the world, like the gradation of its material constitution, that may sound just as counterintuitive to modern ears as quantum properties. One way of reading the Timaean narrative through the eyes of a hexaemeral author is to suggest that in its pre-cosmic state the material world was in an indefinite condition manifesting all possible states of materiality at the

¹²⁸ For two different postmodern critiques to modernity arguing for the positive re-evaluation of the premodern paradigm see Milbank (2006); Hedley and Hutton (2008). ¹²⁹ See Sorabji (1991); Jacob (2014). ¹³⁰ See for example Smith (2004), 194: ‘Keplerian optics is luminocentric rather than oculocentric. Its primary goal is therefore to explain light in terms of its objective, physical manifestations alone’; Smith (2019), 287: ‘this [sc. Newton’s] way of defining colour, according to specific, dynamically determined angles of refraction, is objective and therefore viewer independent’. ¹³¹ On the quantum properties of light see, at a level understandable to the non-physicist, Walmsley (2015) and the collection of papers in O’Collins and Meyers (2012), 17–100. I have here mainly followed the approach of Polkinghorne (2012).

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same time. A contemplative divine act shaped the world into a cosmos through the attribution of arrangement and proportion. Through this act of metaphysical decision or measurement the elementary particles acquired their known state.¹³² Such a transition from disorder to order through the contemplative act of a divine Creator is not that different an intuition about the nature of physical reality from the ‘observer effect’ in quantum mechanics according to which the measurement of a system affects its end state by yielding the knowledge of one and collapsing all other states of being. Of course, the relation of the divine Demiurge to the world was never articulated in quantum terms of an observer–system relation and it would be entirely anachronistic to project quantum mechanics onto premodern cosmology. But one cannot conceal that, all differences aside, the premodern metaphysical intuitions about the structure of physical reality come closer to the post-Einsteinian than the Newtonian paradigm.¹³³ Why then should we rally unreservedly behind the modern optical paradigm and read the sources through the lens of a modern concept of ‘objective’ light when contemporary physics has

¹³² For such a reading see e.g. Gregory’s account in the Apology (esp. In Hex. 7–9 GNO 16.4–19.12, for which see Chapter 2), full of Timaean resonances. That early Christian thinkers read Genesis and the Timaeus ‘in counterpoint’ is a matter of fact. What is debatable is where to draw the line between commonalities and differences; see for two different approaches Pelikan (1997), rather focusing on how early Christians came to the cosmogony of Genesis from having read the cosmogony of the Timaeus; and Köckert (2009), rather focusing on how the interpretation of Genesis and the Timaeus produced distinct exegetical traditions, resulting in distinct cosmological projects and schools of thought: the Christian and the Platonist. In my view, the two approaches can be reconciled if we accept that Christian thinkers developed their own reading of the Timaeus through the lenses of Genesis; see Niehoff (2007), 170–91. I shall substantiate this suggestion further in Chapters 2 and 3. ¹³³ Two papers in the aforementioned volume of O’Collins and Meyers (2012) stand out in this respect, suggesting early intimations of post-Einsteinian insights in patristic and medieval thought: see Boyd (2012), esp. 74 (on Augustine); Bersanelli (2012), esp. 81–8 (on Grosseteste and Dante). The affinity between Grosseteste’s theory of light and post-Einsteinian physics has also been suggested by Mackenzie (1996), 1–5, 79–80, and hinted at by Walmsley (2015), 83–4. All these authors exhibit a vivid and not antiquarian interest in premodern theories of light as sources of inspiration for contemporary discussions. Having said that, there may be less contrast between the Newtonian and the contemporary (Einsteinian and quantum) physics of light than is often assumed, for example as regards the resuscitation of corpuscular properties of light and their combination with undulatory properties; see the remarks of Cohen and Whittaker in the 1952 edition of Newton’s Opticks, x, xiv–xviii, lxii–lxiii. The same may also be true of the Newtonian and the Timaean theories of light, at least as regards their metaphysical intuitions. The remarks of Smith (2019), 286–7, are helpful in this respect, and Smith’s dismissive judgement, unjustifiably harsh in my view (‘no relation whatever’), is another proof of how entangled oculocentrism is in its modern premises. Smith’s explanation that ‘unlike Newton, in short, Plato offers neither a quantitative nor a dynamic account, much less a coherent one, of how the colour particles act’ (287 n.16) is heavily biased. No student of Plato seriously doubts that the Timaean theory of colour is a coherent one, despite its interpretative difficulties; see for a brilliant account Ierodiakonou (2005), with further references. In Chapters 2 and 3 and in Appendix B of this book, I show that the Timaean theory in its hexaemeral adaptation offers a coherent, albeit complex, account of how light particles act through a combination of qualitative (i.e. based on elemental qualities and their interactions), quantitative (i.e. based on mathematical ratios), and dynamic (i.e. based on kinetic laws governing physical projection and collision) principles. To be absolutely clear, and to anticipate possible objections, I am not suggesting that late antique physics anticipated Einsteinian or quantum physics. I am merely suggesting that approaching the ancient theories from a contemporary perspective helps us better appreciate their explanatory principles instead of dismissing them as counterintuitive or allegedly incoherent.

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abandoned such a worldview? It is not only the conclusions of the oculocentric thesis (subordination of light to sight) that do not match the hexaemeral worldview. It is also the modern premises, upon which oculocentrism builds its argumentation, that are rather unsuitable for the task at hand: they are dated from the point of view of quantum physics and at the same time impervious to the subtle dynamics of premodern physics. The postmodern critique of modernity invites us to rethink the role of vision in the physics of light. Behind the premodern optical paradigm lies a basic anthropological insight: we start exploring the world with the senses. The Timaeus posits fire and earth as the two fundamental material constituents of the sensible world because they make the world ‘visible and tangible’ (31b4–7). Aristotle in the De anima provides an astonishing etymology of the representational faculty of phantasia, the outcome of sense perception. It is derived from light (phaos/ phōs), ‘since sight is sense perception par excellence’ and ‘without light it is not possible to see’ (III.3 428b30–429a4). Thereupon, Martha Nussbaum in an influential article has claimed that Aristotle’s ‘account of the faculty of phantasia seems to be closely tied to his usage of the verb [phainesthai (appear)] and suggests a very general interest in how things in the world appear to living creatures’.¹³⁴ We find a similar approach to phantasia in the Stoics. Chrysippus, like Aristotle, reportedly derived the etymology of the term from phōs, ‘for just as light reveals itself and whatever else it includes in its range, so impression (phantasia) reveals itself and what produced it’.¹³⁵ The underlying assumption is that light makes the world visible because light reveals things.¹³⁶ The visible world is the world as it appears to the senses understood primarily in terms derived from the experience of sight, the world as a phainomenon. The conscious phenomenal experience triggers curiosity and becomes the springboard of all scientific enquiry. Ancient physics begins with an enquiry into the phainomena, things as they appear to the senses. So does all scientific enquiry, modern physics included. Scientific enquiry, however, does not exhaust itself with the realm of appearances. It searches for rational explanations that are by nature of a different order than the phenomena that they explain. The search for rational explanations led the premodern mind to the discovery of the noumenal realm of intelligible

¹³⁴ Nussbaum (1978), 222. For the reception and further development of Nussbaum’s view see the discussion in O’Gorman (2005), 18–23, with references. ¹³⁵ Aëtius, Plac. IV.12 (900E) = Long/Sedley 39B, from where also the translation, slightly modified. For a survey of the discussion on Stoic phantasia see Dinucci (2017) and De Harven (2018). ¹³⁶ This is the basic tenet of the classical ‘metaphysics of light’; see Blumenberg (1957), esp. 142–3. Because of its triviality, however, it can serve only as a starting point for reflection. Every school of thought in late antiquity accepts that light reveals the world by making things visible. The interesting question is how light reveals things, and what this means about the nature of the world qua visible. It is in answering these questions that we get the different physics and metaphysics of light of the schools.

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paradigms and causes. Here too we find a frequent use of the analogy of light, whether in the form of the intelligible sun in Plato’s ‘sun simile’ in the Republic (VI 507–9) or Aristotle’s adaptation thereof in the analogy of the ‘active’ intellect with light in the De anima (III.5 430a10–17). The idea seems to be the same as before: light’s fundamental function is to reveal things. Just as physical light reveals the phenomenal world of change to the senses, so does light’s intelligible analogon reveal the noumenal world of causal explanations to the intellect. Not only the beginning but also the end of scientific enquiry is, in a sense, ‘phenomenological’. We perceive reality physically as it appears to the senses through the sense organs, most notably the eye. And we apprehend reality intellectually as it appears to the intellect through a corresponding receptive faculty, the so-called ‘mind’s eye’ of the Platonists or the ‘passive intellect’ of the Peripatetic tradition. The dialectics of the phenomenal world of change with the noumenal world of intelligible causes is also the general framework of hexaemeral epistemology.¹³⁷ One can see here a main theme emerging in the hexaemeral literature, a theme that each author will develop more or less independently, a common theme nonetheless. That theme is the celebrated Cosmos–Scripture analogy, which we already saw animating Alexandrian and Cappadocian hexaemeral exegesis. In approaching creation through the Genesis text as a narrative, the reader is required to develop a double vision: a retrospective vision of the world as it appears historically, in cosmic time, as we look back; and a prospective vision of the world as it appears literarily, in narrative time, as we read on. It is a double vision of the world as a material and literary phainomenon. Hexaemeral hermeneutics is thus visually contingent. But hexaemeral vision is luminocentric, we must never forget, since it is the light that reveals the phainomena to the eye—an eye which is itself luminous. With this caveat in mind I am very willing to subscribe to the ocularism—though not oculocentrism—of the hexaemeral paradigm.¹³⁸ But ‘ocularism’ in this sense will mean no more than a luminocentric phenomenal experience of reality. The gradual emergence of the world to the eyes of the reader in and through light is what hexaemeral phenomenality is all about. In narrative time, the hexaemeron takes the form of a revelation. The world appears gradually to the reader, from a state of primordial simplicity (‘day one’) to a state of complex multiplicity (‘day six’). Only the latter state is the world as we know it. To

¹³⁷ See paradigmatically Gregory, In Hex. GNO 17.4–9: Moses’ purpose (skopos) is to lead by the hand those who are enslaved to sensation (aisthēsis) through the visible (phainomena) to the suprasensible. Heaven and earth set the limits of all perceptual knowledge (tōn dia tēs aisthēseōs hemin ginōskomenōn). Clearly, for Gregory, ‘heaven and earth’ in Gen. 1:1 fulfil exactly the same phenomenological role and function as ‘fire and earth’ in Tim. 31b4–7. ¹³⁸ For a phenomenological approach to ancient theories of light see Vasiliu (1997); Pickstock (2007); Squire (2016b).

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apprehend the primordial unity of ‘day one’ a reductio is needed. ‘Hexaemeron’ denotes in this sense a retrograde motion of ascent (or descent) in six contemplative steps, from phenomenal complexity to noumenal simplicity. Take away the steps and all that is left is just another account of the archē, a biblical counterpart to ancient cosmogonies, important, maybe, for the history of cosmological speculation, but devoid of theological meaning. The hexaemeral authors transform the perennial search for the archē into a performative act of divine pedagogy, a ‘spiritual exercise’, to reprise Pierre Hadot, in six retrograde, contemplative steps.¹³⁹ The steps give rise to the invert perspectivism of a phusikē theōria, the introspective vision of a simple divine presence emerging through the world of the senses. The hexaemeron thus becomes the narrative space of a gradual encounter with the ‘mystical’, to rephrase Vladimir Lossky.¹⁴⁰ It is Moses’ guide into (and out of) the perplex structure of phenomenal reality. In learning to discern the underlying pattern of creation, its intelligent design—the ‘seeds’ or imprints of the logos—the contemplative reader is led step by step from the phenomenal world to its noumenal structure.¹⁴¹ This change in perspective, from the world as it appears to the senses to the world as it appears to the intellect, and back again, is the plan and purpose, the celebrated hermeneutical principles of the akolouthia (sequence) and skopos (purpose),¹⁴² of the Mosaic account of creation.¹⁴³ Or so at least is how I suggest that the hexaemeral authors interpreted creation, reshaping hermeneutically a historical account that can be scientifically disproved into an anagogical narrative that is theologically still valid and fertile.¹⁴⁴ The anagogy begins with the kind of light that reveals the phainomena to the bodily eye and ends with the kind of light that reveals the noumena to the mind’s eye. This anagogical theme shapes the contours

¹³⁹ On the study of nature as ‘spiritual exercise’ in the patristic period see the remarkable paper of Hankey (2013). On the contemplative and salvific nature of scriptural exegesis see the seminal study of Martens (2012). ¹⁴⁰ On contemplation of nature as part of the ‘mystical’, i.e. transformative, experience of the soul see the classical study of Louth (2007), 56–9, 99–100, 104–5. On natural theology as ‘integrated into a mystical knowledge of God and of his creation’ see Knight (2013), esp. 218. ¹⁴¹ See characteristically Basil, Hex. I.6 GCS 11.12–13: ‘since through the experience of visible and sensible things the mind is led, as by a hand, to the contemplation of invisible things’; Hex. VI.1 GCS 88.7–8: ‘through visible things you reflected the invisible Creator’. For the prehistory see Di Mattei (2006), 22 (Philo); Rizzerio (1996), 291–312 (Clement). For the exegetical continuity see e.g. Ishac (2013), 4, 14 (for the Syriac tradition). ¹⁴² See on this the landmark studies of Schäublin (1974) and Young (1989), and more recently the magnificent monograph of Young (1997). ¹⁴³ The change in perspective is also hermeneutical, from the surface level to the sensus plenior of the text, as Nikiprowetzky (1977), 102–8, rightly perceived. As will be shown in the next chapter, however, the sensus plenior is not necessarily allegorical, as Nikiprowetzky seems to have thought, but is revealed through contemplation of the akolouthia and skopos of Scripture. ¹⁴⁴ This is not an eccentric suggestion. For a similar understanding of the patristic interpretation of nature as theological transformation of the scientific knowledge available at the time see, for example, Nesteruk (2003), 20–1.

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of the hexaemeral narrative as an intellectual journey from the phenomenal to the noumenal.¹⁴⁵ It is the hexaemeral journey from the physics to the metaphysics of light. The map of this journey is the subject matter of the following sections— a hexaemeral guide for the perplexed. I shall commence with the physics of light.

¹⁴⁵ To the possible objection that the transformation of the Mosaic account into an anagogical narrative is ‘too Platonic’ one could answer that the hexaemeral authors also transformed the anagogical theme into a Christocentric narrative; see above, section 1.3.3. But Cox (2007) has, in my view convincingly, shown that the Christocentric anagogical theme was already anticipated in Middle Platonism through the role of the logos as intermediary principle. Thus, my answer to the possible objection would be that early Christian thinkers saw no discontinuity between their hexaemeral project and the philosophical contemplation of nature. On the contrary, they felt free to build on it; see Gregory Nazianzen, Orat. 43.11 (In laudem Basilii Magni, Bernardi 136–40).

2 The Light of the World Hexaemeral Physics and Anti-Physics

Fire is one of the four elements. It is light and more buoyant than the others, and it both burns and gives light. It was made by the Creator on the first day, for sacred Scripture says: ‘And God said: Be light made. And light was made.’ According to what some say, fire is the same thing as light. Others speak of the cosmic fire above the air and they call it aether. ‘In the beginning,’ then, which is to say, on the first day, God made the light to adorn and enhance all visible creation. (John Damascene, De fide II.7 tr. Chase) In Chapter 1, I set out to investigate the hexaemeral physics of light with the aim of retrieving the concept of light underlying the hexaemeral literature of the early Church. Before I could examine the source material, however, I had to meet a preliminary objection. The prevalent school of thought in modern historiography contests altogether the possibility of an ancient physics of light, and with it the possibility of a premodern enquiry into the nature and properties of light as an agent of change in the world. Instead, it argues that the study of light was subordinated to the study of sight, with the consequence of interpreting all of light’s properties in a purely visual sense. The aim of the previous chapter was to take the oculocentric approach seriously, situate it within the hexaemeral literature, and assess its cogency. The enquiry did not support the oculocentric hermeneutics, at least as far as the hexaemeral literature is concerned. On the contrary, a close study of the sources revealed that the oculocentric interpretation rests upon a subtle but profound misunderstanding. It confounds the teleological justification of light, which is indeed conceived anthropocentrically, though biblical exegetes modified ancient anthropocentrism by giving it a Christocentric twist, and the scientific explanation of light, which is a proper field of scientific enquiry independent of sight. The confusion obscures the fine but important line that separates the enquiry into the nature of things perceived (physics of light) and the nature of perception (theories of vision). It thus conceals the existence of a proper physics of light in the sources. If my argument is correct, one can do away with the oculocentric objection. The road is now open for a proper investigation into the hexaemeral physics of light. Or is it?

The Metaphysics of Light in the Hexaemeral Literature: From Philo of Alexandria to Gregory of Nyssa. Isidoros C. Katsos, Oxford University Press. © Isidoros C. Katsos 2023. DOI: 10.1093/oso/9780192869197.003.0003

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As this chapter begins, we shall see that once the oculocentric objection has been addressed, a new challenge threatens the initial quest. This time, two new sets of objections are raised against the enquiry into the hexaemeral physics of light. Ancient philosophers contested the rational foundations of the creation narrative, and with them the credibility of any project on hexaemeral physics. Modern theologians, on the other hand, contest the need for a rational foundation of Scripture altogether, and with it the justification of any hexaemeral physics at all. We thus come to the following picture: while historians of science object to the cogency of a hexaemeral physics of light, ancient philosophers and modern theologians object, for different reasons, to the cogency of a hexaemeral physics of light. In what follows, I shall attempt to thread the needle by showing how the hexaemeral exegetes defended the project of biblical physics in general and of the physics of light in particular. I shall argue that, from a hexaemeral perspective, the biblical creation narrative entails the guidelines of a scientific framework, which is the particular task of the exegetes to retrieve and contextualize in their own intellectual milieu. I shall illustrate how Origen shaped hexaemeral physics through a unique fusion of biblical exegesis with Jewish-Christian apologetics and how later hexaemeral exegetes further developed Origen’s project until it reached a culmination point in Cappadocian thought, most notably in the work of Gregory of Nyssa. Once the last sets of objections against the project of a scientifically based reading of Scripture have been addressed, I shall lay out, with the help of Gregory, the basic tenet of the hexaemeral physics of light.

2.1 Science at the Service of Scripture Any enquiry into the hexaemeral physics of light suggests that there is some scientific framework underlying the biblical creation narrative. Yet the very suggestion that there is a scientific background to Scripture is itself contentious. Karl Barth, in a famous letter to his niece, decried the comparison between the biblical creation narrative and any particular scientific theory (he had evolutionism in mind) as a category mistake, such that ‘there can be as little question of harmony between them as of contradiction’. The biblical interpreter ‘should distinguish what is to be distinguished and not shut herself off completely from either side’.¹ Barth’s message is clear, expressing the opinion of many contemporary theologians: in dealing with Scripture, one had better keep theology and science apart. There are good reasons for that distinction. The dangers of associating Scripture with a particular scientific worldview have been recently portrayed

¹ See Fangmeier and Stoevesandt (1981), 184 (letter 181).

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by John Hedley Brooke in a telling comparison between Augustine’s and Thomas Burnet’s hexaemeral projects: [Burnet] applauded St. Augustine for his warning that science and religion should not be too tightly interlocked, that it was dangerous to invoke the authority of Scripture in disputes about the natural world. The danger as Burnet saw it was this: As scientific understanding advanced, propositions that Scripture had been made to affirm would be proved false. Its authority would then be jeopardized on far more important matters. But, says Burnet with evident condescension, Augustine had fallen into the very trap he had identified. He had used the Bible in his dismissal of inhabitants at the Antipodes. Burnet, so much wiser in the late seventeenth century, is even more aware of the danger and knows how to avoid it. And yet, anyone reading Burnet’s Sacred Theory of the Earth (1684) today would be struck by the fact that he falls headlong into the selfsame trap. Instead of keeping the spheres of science and the Bible apart, he brings them together. He offers a mechanistic account of how the Genesis flood had come about, and he defines the main epochs of earth history with reference to information gleaned from his Bible. His picture of a submerged earth, in which Noah’s ark is conspicuous, shows how the flood was made constitutive of the earth’s physical history. The point of the example is not to score points against Burnet but to raise the more sympathetic question: How was it possible for Augustine to behave in a manner that, to a later generation, looked inconsistent? And similarly for Burnet.²

Brooke’s answer to the question has to do with the shifting of the boundaries between ‘science’ and ‘religion’ over time, so that Augustine, Burnet, and the contemporary reader understand the relation differently. But the point of the critique remains: how can any intelligent reader of Scripture be so short-sighted as to tie down divine revelation, which ought to be by nature universal and diachronic, to any particular scientific and cosmological worldview, which is by nature ephemeral and contingent? The question is somewhat misleading. It is one thing to acknowledge the connection between Scripture and science and another thing to claim that the connection comes at the cost of the meaning of Scripture. The difference was articulated by one of the most erudite voices in twentieth-century hermeneutics, that of Rudolf Bultmann. Throughout his work, Bultmann acknowledged that the theological meaning of the gospel (the kerygma) is delivered in the context of the physical world of the New Testament, the ‘mythical’ and ‘pre-scientific’ (as he

² John Brooke (1991), 10.

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thought) cosmology of the ancient Jewish and Greek world. Bultmann claimed that the contemporary Christian cannot relate to this ancient mythological framework, nor take it seriously. Contrary to nineteenth-century German theological liberalism, however, Bultmann did not try to eliminate the cosmological element from Scripture. Instead, he tried to make sense of it through interpretation. He thus aimed to uncover the diachronic relevance of the kerygma for the human predicament by penetrating Scripture’s mythological-cosmological background. He called this process ‘demythologizing’ (Entmythologisierung) and found the always relevant meaning of Scripture in its existentialist interpretation.³ In doing so, he did not aim at vindicating any particular scientific worldview by Scripture. Instead, he aimed at vindicating Scripture from any particular scientific worldview. The basic premise of Bultmann’s ‘demythologizing’ thesis is that Scripture is not born in a scientifically neutral hermeneutical space. On the contrary, the text is embedded in a certain premodern scientific worldview. This is an insight also shared by the early Jewish-Christian hexaemeral exegetes, though they would not follow Bultmann’s existentialist reading of Scripture. Hence, the answer of a hexaemeral author to Brooke’s criticism would go some but not all the way with Bultmann. In reading Scripture scientifically, the premodern exegete claims to follow Scripture’s own hermeneutical premises. In deciphering the scientific background of Scripture and in translating it into his own terms, the hexaemeral author is simply performing, with Bultmann, a premodern ‘demythologizing’ project, translating the meaning of Scripture for a premodern audience. Against Bultmann, however, who is wrestling with the possibilities and limitations of the existentialist philosophy of his time, the Hellenistic and late antique exegete is wrestling with questions arising from a different intellectual milieu, deeply interested in questions of cosmology. What is expected of him is not the dissociation of science from Scripture but exactly the opposite, namely a disquisition on the cosmogenesis from a scriptural perspective. The hexaemeral project aims precisely at that: to put the science of its time at the service of Scripture by actualizing, for the contemporary audience, through interpretation, the cosmological framework of the biblical creation narrative. Augustine is only one case of early Christian exegesis putting science at the service of Scripture. Another case is Gregory of Nyssa, whose Apology to Basil’s Hexaemeron is the most spectacular example of a scientifically informed interpretation of the biblical creation narrative in the early Church. In the opening paragraphs of the Apology, Gregory informs us that Basil’s literal hexaemeral exegesis was motivated by a popularizing approach to biblical cosmology reaching out to a large and mixed audience. Gregory’s own project aims to ³ Bultmann’s position, together with a valuable introduction and critical responses, can be found in Bartsch (1953).

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follow the same pattern of biblical exegesis, only adapting it to meet the needs of the erudite. Some of the most difficult issues to tackle were questions pertaining to the celestial physics of light. But I believe that some have not understood properly the aim (skopon) of his [sc. Basil’s] work On the Hexaemeron. That is why they accuse him of not giving them sufficient information about the sun, namely how the light-bearer is created after three days together with the rest of the heavenly bodies, though it was impossible to separate between morning and evening without the sun’s set and rise . . . Now, those that bring forward the above and similar accusations have not paid close attention, in my opinion, to the aim (skopon) of our father’s teaching (didaskalias), who was conversing with a large crowd in a church flooded with people and had therefore to adapt his discourse (logon) to the needs of his audience. Among so many listeners there were many who had inside knowledge of the advanced teachings (tōn hupsēloterōn epaïontes logōn). But there were even more who could not attain to the subtle investigation of the meanings of Scripture (tēs leptoteras exetaseōs tōn noēmatōn), average men and handicraftsmen engaged in manual labour, as well as a multitude of women untrained in this kind of learning (mathēmatōn), together with a crowd of children and the elderly. All these needed discourses (logōn) that would lead them by the hand from the visible creation (dia tēs phainomenēs ktiseōs), and the good in it, to the knowledge of the maker of the All, followed by an understandable pedagogy of the soul (eulēptou psuchagōgias). Thus, if we judge the words (ta legomena) of our venerable master according to the aim of his teaching (pros ton skopon tēs didaskalias), we will find nothing wanting. For he did not set up a polemical discourse (agōnistikōteron logon), zealous to wrestle with disputed questions. Instead, his discourse focused on the simpler meaning of the words of Scripture (tēs haplousteras tōn rhēmatōn exēgēseōs), with the aim of speaking in a manner suitable to the elementary level of his audience (tēi aplotēti tōn akouontōn). At the same time, however, he was lifted up, in a way, in his scriptural exegesis, together with the initiated in greater teachings (tois tōn meizonōn akroatais), comparing side by side the interpretation of Scripture with the various teachings of secular philosophy (ta poikila mathēmata tēs exō philosophias). As a result, he was understood by the many (tōn pollōn) and was admired by the knowledgeable (tōn huperechontōn). (In Hex. 3–4 GNO 8.12–11.2, my translation)

Who are Basil’s accusers? Throughout the treatise they remain anonymous.⁴ But that is beside the point. Gregory is here addressing a wider issue, common in the ⁴ We can identify at least one group of Basil’s accusers: Eunomius and his followers, see van Esbroeck (2018).

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philosophical discussions of his time. It is the charge of a certain scientific naiveté of the biblical creation narrative.⁵ The gauntlet had been eloquently thrown at the feet of any Jewish-Christian exegete a couple of centuries earlier by the Platonist philosopher Celsus. In whatever measure we are able to reconstruct his True Doctrine from Origen’s monumental response, it is clear that Celsus questioned the rationalistic foundation of the biblical creation narrative. In Origen’s words: Let us also consider the next remarks where he objects to the Mosaic story of the creation of the world with a single bare assertion without even saying anything plausible. Besides, the cosmogony too is very silly (euēthēs). (CC VI.49) After this he piles up mere assertions about the different views concerning the origin of the world and of mankind held by some of the ancients whom he has mentioned and says that Moses and the prophets who left our books had no idea what the nature of the world and of mankind really is, and put together utter trash (lēros bathus). (CC VI.50) After the passage we have examined, as though it were his object to fill his book somehow with lengthy verbosity, he makes a remark which, though in different words, is to the same effect as that which we examined a little above, where he said: But far more silly (euēthesteron) is to have allotted certain days to the making of the world before days existed. For when the heaven had not yet been made, or the earth yet fixed, or the sun borne round it, how could days exist? What difference is there between these words and this remark: Moreover, taking the question from the beginning, let us consider this. Would it not be absurd for the first and greatest God to command, Let this come into existence, or something else, or that, so that He made so much on one day and again so much more on the second, and so on with the third, fourth, fifth, and sixth? (CC VI.60 tr. Chadwick; Celsus’ text in italics)

The first two passages deliver a clear message: the biblical creation narrative does not even fulfil the minimum standards of a didactic and pedagogically useful myth. The terms used, euēthēs and lēros bathus, betray a familiarity with various interpretative attempts to read the biblical creation narrative allegorically. Celsus, who is excellently informed about the ‘Gnostic’ sects, and might have their interpretations in mind, finds fault with the allegorical interpretation of Scripture.⁶ He implies, not without some sense of irony, that, at best, the moral

⁵ On the Apology as ‘a sample of “Christian science” in answer to the critics who believed Christian theologians to be unable of like exploits’ see Costache (2013a), 391. Similarly, Köckert (2009), 401; GilTamayo (2010b), 387. ⁶ On Celsus’ rejection of the allegorical interpretation of Scripture see CC I.17; IV. 38. Origen responds that in interpreting Scripture allegorically the Christian exegetes do nothing less than what Celsus does with his own religious myths.

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or deeper meaning adds nothing new to the current discussion.⁷ At worst, it is a very bad example of allegorical interpretation.⁸ The third passage expresses the same idea from a hermeneutical perspective. In comparing Gen. 2:4 with Gen. 1:1–5, Celsus spots a series of contradictions in the narrative sequence. They remind us of the charges laid against Basil and reported by Gregory: does the first day of creation include the creation of heaven and earth (Gen. 2:4) or only of light (Gen. 1:1–5)? How could heaven and earth be created in the first day (Gen. 2:4) when we are previously told that they existed before the first day (Gen. 1:1–5)? If the first day of creation occurs with the creation of light (Gen. 1:1–5) what kind of day is the one in which heaven and earth were made without the existence of light (Gen. 2:4)? The aporiai aim to show the apparent incoherence of the scriptural narrative. At stake is, clearly, the coherence (heirmos) and narrative sequence (akolouthia) of the text. Celsus’ True Doctrine was probably written in Alexandria or Rome between 177 and 180 . Just a few years earlier, Galen had expressed a similar criticism in his celebrated treatise On the Usefulness of Parts.⁹ Written in Rome between 169 and 176 , the treatise aims to show that every part of the human body was perfectly designed by divine intelligence to fulfil a certain function. The overall point of the treatise is teleological, repeatedly expressed in the adage that ‘nature does nothing in vain’. It is in this context that the usefulness of such a seemingly insignificant part of the body as eyelashes is brought up as a polemical example against the materialist account of nature, exemplified in the Epicurean atomism of the time, as well as a more fideistic account of creation, exemplified in the biblical creation narrative. Has then our Demiurge commanded only these hairs to preserve always the same length and do they preserve it as they have been ordered because they fear their master’s command, or reverence the God who gave this order, or themselves believe it better to do this? Is not this Moses’ way of treating Nature and is it not

⁷ Notice the word play: at a surface level, euēthēs and lēros bathus denote ‘silly’ and ‘utter trash’, respectively. On deeper reflection, however, the eu-ēthēs is an implied reference to the moral (ēthos) sense and the lēros bathus to the deeper (bathus) sense of Scripture. Celsus is a skilled critic. With his first- and second-order use of language he launches a performative attack on the double meaning of Scripture, literal and allegorical. ⁸ Origen repeatedly complains that Celsus confuses non-mainstream teachings with mainstream Christian doctrines, see CC V.61–5, VI.24ff., VII.25, VIII.15, and Chadwick (1953), xxviii–xxix. We may assume that Origen’s substantiated riposte to Celsus’ attacks on the allegorical interpretation of the creation narrative would have been along the lines that Celsus confuses ‘Gnostic’ or other interpretations of Scripture, which Origen also rejects, with orthodox interpretations of the Genesis narrative, which Origen follows. Be it as it may, the brute fact remains that Celsus did not substantiate his claim nor Origen his riposte, while the relevant parts of the Commentary on Genesis, to which Origen refers the reader, are lost. ⁹ Galen’s critical stance towards Jewish-Christian creationism has recently attracted the attention of scholars, see Tieleman (2005); Sedley (2007), 241–2; Radde-Gallwitz (2017). Still fundamental is the work of Walzer (1949).

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   - superior to that of Epicurus? The best way, of course, is to follow neither of these but to maintain like Moses the principle of the Demiurge as the principle (or cause, archēn) of generation of all created things, while adding the material principle to it . . . It was, then, certainly not sufficient merely to will their becoming thus; for had he [sc. the Demiurge] wished to make a man out of a stone in an instant (exaiphnēs), it would not have been possible for him either. It is precisely this point in which our own opinion and that of Plato and the other Greeks who follow the right method in science differs from the position taken by Moses. For the latter it seems enough to say that God simply willed the arrangement of matter and instantaneously (euthus) it was arranged; for he believes everything to be possible with God, even should he wish to make a bull or a horse out of ashes. We however do not hold this; we say that certain things are impossible by nature and that God does not even attempt such things at all but that he chooses the best out of the possibilities of becoming. (Usu XI.14 Kühn III.905–6 tr. Tieleman)

In drawing attention to this passage, David Sedley remarks that Galen opposes Moses’ omnipotent God, who was ‘able to create the world and its parts by mere fiat, without concern for the properties of matter’, with Galen’s version of the Platonic Demiurge, who, by contrast, is ‘a craftsman working skilfully with the properties of his materials’.¹⁰ Teun Tieleman rightly adds that Galen seems to be an informed critic of Scripture.¹¹ Tieleman remarks that the possibility of God creating man out of a stone echoes such passages as Luke 3:8 and Matthew 3:9, with a possible distant echo of the Greek myth of Deucalion and Pyrrha also in the background.¹² From the perspective of an erudite external reader of Scripture like Galen, just like Celsus, the biblical creation narrative situates itself in the realm of the mythical rather than the rational.¹³ Even more interesting is Galen’s polemical suggestion that the biblical creation narrative relies entirely on divine command. The accusation implies more than it explicitly says. First, it insinuates that narrative inconsistencies, like those spotted by Celsus and Basil’s anonymous critics, which introduce paradoxical series of

¹⁰ Sedley (2007). ¹¹ Tieleman (2005), 125. See also the astute remark on pp. 133–4 that Galen is aware of mainstream biblical exegesis interpreting the act of creation as taking place ‘in an instant’, see Philo, Opif. 13, 28, 41, 65, 67: hama, homou, athroa kairōi; Basil, Hex. I.6 GNO 11.15–16, 12.1, 12.3–4: to akariaion kai achronon tēs dēmiourgias, achronōs, athroōs kai en oligōi; Ambrose, Exam. I.4.16: in brevi et in exiguo momento; Gregory, In Hex. 7 GNO 16.4, VIII GNO 17.11, 17.15–19, IX GNO 18.1, 18.9: homou, athroōs/to athroon/athroa, sullēbdēn, to akares te kai adiastaton, en akarei. Furthermore, Galen’s critique of divine will as the sole ground of creation captures, indeed, the focal point of Christian hexaemeral exegesis after Theophilus of Antioch and Irenaeus of Lyon, see May (1994), 156–78; McFarland (2014), 1–24. Galen seems to be a very well-informed critic of Jewish-Christian hexaemeral exegesis. ¹² Tieleman (2005), 135–6. ¹³ On the affinity between Galen’s and Celsus’ arguments see Tieleman (2005), 138–40 (citing CC V.14); Chadwick (1953), 375 n.4 (citing CC VI.60, mentioned above).

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causation, like the effect (e.g. light) preceding its cause (e.g. the sun), can be solved by mere recourse to divine omnipotence. This view is better than atomistic atheism, says Galen, because it at least recognizes God as the efficient cause of creation. From this follow, implicitly, fundamental premises of late antique natural theology, like divine providence and teleology, which are denied by the atomists, but which Galen seems willing to see as operative in Jewish-Christian theism. What is not operative, however, because the recourse to divine omnipotence eliminates its function, is the material principle. That is not to say that the Jewish-Christian exegetes have no role for matter in the world. It only means that they do not have a metaphysically robust account of it.¹⁴ In the reading of the Timaeus that Galen is following, mechanical causation (i.e. matter and its properties) is a necessary and independent category of cause.¹⁵ Having no inherent propensity towards the good, it acts in a random and purposeless way until it is guided by divine intelligence towards good ends, within the possibilities and limits of its properties. If, however, the creator is an omnipotent God, like Moses’ God, who can arrange matter in whatever way he wishes (as e.g. in making a bull or a horse out of ashes), there is no need for material causality, or, worse, God is responsible for all the randomness and purposelessness (and hence for evil) in the world. That is clearly a position that no Jewish-Christian thinker can accept. Hence Galen’s challenge: either keep divine omnipotence at the cost of making God responsible for the constraints of materiality; or accept the intrinsic limits of matter and its properties and protect divine intelligence from material imperfection. In the background lies, of course, a critique of the doctrine of creation ex nihilo, which makes matter entirely dependent on divine will.¹⁶ By overlooking the necessity of mechanical causation in the physical universe the Jewish-Christian thinkers miss something important about the structure and function of the world. That seems to be the deeper point in Galen’s critique.¹⁷ ¹⁴ In the same way Tieleman (2005), 138: In Galen’s view, the Mosaic account of creation ‘is defective in regard to causal theory, notably its lacking specification of a rationally acceptable material cause’. ¹⁵ Responsible for imperfection (and evil) in the world, see on this reading of the Timaeus Cornford (1937), 161–77. ¹⁶ That is the only point in which I diverge from Tieleman (2005), 135, 143, who does not think that creation ex nihilo plays a role in Galen’s argument. I think it does, regardless of the precise content of the ‘ex nihilo’ in Galen’s day: from nothing in particular, as seems to be the case in Philo and Justin? Or from absolutely nothing, as seems to be the case in Tertullian?, see Edwards (2002), 62. The reason for my divergence is that Tieleman, following May (1994), xii–xiii, 8, 148–80, understands the ex nihilo only in its ‘technical sense’, i.e. in its later Jewish-Christian-Muslim version as creation out of absolutely nothing (pp. 126, 134, 135), while I prefer to keep both options open. Beyond that, I think that Tieleman and I would both agree that creation ex nihilo (in all its versions) has divine omnipotence as its ontological foundation (cf. p. 126). Galen is pressing the point that the Demiurge is not unlimited, and hence not truly ‘omnipotent’, because he is confined by the conditions of empirical reality. Galen’s Demiurge is not free from empirical necessity, as his examples show, see Cornford (1937), 36, 176. ¹⁷ With the caveat just mentioned above, here I develop further the argument of Tieleman (2005), 133–8. If we accept, with Tieleman (p. 133), that ‘the basic schema underlying this passage is that of the Platonic Timaeus interpreted in terms of the four Aristotelian causes—a reading initiated by Aristotle himself and continued by his associate Theophrastus and others’, we must also accept that in

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Hence the anti-rationalistic charge against Scripture, also shared by Celsus, though in Galen the critique acquires a more appreciative tone as regards God as the efficient cause of the world. Nevertheless, in underestimating the role of the material cause the biblical account of cosmogenesis fails to satisfy, in Galen’s considered view, the minimum standards of a metaphysically robust theistic account of the world. I have here mentioned Galen’s and Celsus’ attacks on the ‘logic’ of the biblical creation narrative in order to show how different were the challenges faced by the premodern scriptural exegete compared to the modern. The twentieth-century theologian had to answer the charges pressed by Harnack, Nietzsche, Heidegger, and the like, that Scripture, contaminated allegedly by the categories of Greek philosophy, had become too rational. Origen and Gregory, on the other hand, had to face the exact opposite charges, laid out by Galen, Celsus, and their followers like Porphyry and Julian,¹⁸ that Scripture was too irrational. To dissociate Scripture from science or to shift focus from the cosmological to the anthropological dimension, as Barth, Bultmann, and their students would have it, would be detrimental to the credibility of the Jewish-Christian faith in the intellectual milieu of late antiquity. It would be like pleading guilty to the charges laid by erudite pagan circles against the credibility of Scripture. That is something that no hexaemeral author was willing to do. We therefore need to realize that the early hexaemeral project was not only exegetical but also apologetic in nature.¹⁹ On the one hand, the hexaemeral exegetes had to distinguish between non-mainstream (‘heretical’) and mainstream (‘orthodox’) readings of Scripture, arguing that Galen and Celsus simply had the wrong interpretation in mind—hence the constant

juxtaposing ‘the Demiurge as the principle (or cause, archēn) of generation of all created things’ with ‘the material principle’, Galen implicitly concedes that the Mosaic account recognizes three out of four Aristotelian causes, namely the efficient, the formal, and the final, while it misses the fourth, namely matter. This is because, according to a unitary reading of the Aristotelian corpus, Aristotle thinks of the three causes (efficient, formal, and final) as converging in the Prime Mover, see Bradshaw (2004), 38–44. Our Galenic passage seems to follow that reading, as Tieleman (p. 133) rightly perceives. ¹⁸ See the testimony of Libanius, Orat. 18 (§178), repeating the common charge against the logic of Scripture as ‘ridiculous’ (gelōta) and ‘idle talk’ (phlēnaphon), with reference to Porphyry’s Contra Christianos and Julian’s Contra Galileos. See in detail Meredith (1980), 1119–49, and briefly O’Brien (2015), 13 (on Julian as the major contender of the Cappadocians). Julian’s critique on the biblical creation narrative is now superbly discussed by Riedweg (2020). ¹⁹ For example, Philo’s De opificio, the first extant hexaemeral treatise, opens with an apologetic motif in §§1–3. The apologetic motif runs through the whole treatise and resurfaces clearly at the end in §§170–1, see Runia (2001), 99. The same feature (apologetic motif interwoven with biblical exegesis) is retained in all subsequent hexaemeral works, see e.g. Basil, Hex. I.1–2; Ambrose, Exam. I.1–2; Gregory, In Hex. 1–4 GNO 5–11, echoing the original Philonic theme. The apologetic motif seems to be present when the exposition is addressed to a wide and mixed audience, comprising non-initiates, starting with Philo’s Exposition of the Law at the head of which we find the De opificio and going down to all hexaemeral literature with a similar audience. When the audience, however, is a circle of initiates, the apologetic component is no longer necessary, as we can see from Origen’s hexaemeral (first) Homily on Genesis. I feel that the traditional apologetic dimension of the hexaemeral literature has escaped Doru Costache’s learned analysis of Gregory’s Apology, which I discuss below.

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guard against deviant readings in the hexaemeral literature.²⁰ On the other hand, the hexaemeral authors had to vindicate the rationality of the creation narrative, creating space for mechanical causation in their exegesis. If the Jewish-Christian philosophical theology were to be meaningful, it had to argue for the manifestation of divine omnipotence at the level of the material principle. Otherwise the whole arrangement of the world would be completely arbitrary and there would be no metaphysical explanation for the properties of material things other than a suprarational divine will.²¹ The only way of integrating material causality into the explanation of the world was by putting the whole philosophical knowledge available at the time, especially cosmology and science, at the service of Scripture. It is the celebrated ‘handmaiden’ formula, imported and adapted by Philo to fit the demands of scriptural exegesis,²² reshaped by the Cappadocians into the principle of chrēsis or selective appropriation.²³ Both maxims (‘handmaiden’ and chrēsis) encourage the readers to make use of the best available scientific and other secular knowledge of their time as a necessary condition for penetrating the deeper meaning of Scripture. It is precisely in this context that the ancient physics of light became an indispensable part of the hexaemeral project.

2.2 In Defence of Hexaemeral Physics 2.2.1 Origen and His Legacy A forceful response to Celsus’ erudite criticism came, famously, from Origen. In his celebrated apologetic treatise, the Contra Celsum, Origen undertook the heroic effort of answering, one by one, all the charges laid against Scripture, including the credibility and rationality of the biblical creation narrative. Origen met Celsus face ²⁰ See Philo: Opif. 13, 26–7; QG 1.1; Leg. 1.20; Basil: Hex. II.4, III.9, VIII.1, IX.1; Ambrose: Exam. I.8.30, IV.7.32; Chrysostom: Hom. Gen. II.3 PG 53:29d; Serm. Gen. I.1 (SC 433, 144 = PG 54:581), I.2 (SC 433, 156–8 = PG 54:583), I.3 (SC 433, 164–6 = PG 54:584), VIII.1 (SC 433, 350 = PG 54:617). The tone is already given by Philo, who constantly strives for a median line of exegesis, rejecting both extreme literalism and extreme allegorism, see Daniélou (2014), 76–89; Hay (1991), 81–97. The locus classicus is Migr. 89–93. The charges of Galen and Celsus against the rationality of Scripture are already anticipated in the Philonic corpus, see e.g. Conf. 2, 5, 9 (regarding Gen. 9:1–9): hostile critics claim that the Jewish scriptures contain borrowed and foolish myths (muthous, phrenoblabeia deinē, muthōdes); QG 3:43 (regarding Gen. 18:5): uninitiated (tōn amuētōn) critics ridicule the biblical account of the change of names. ²¹ A thorough discussion of hexaemeral theories of materiality goes beyond the scope of this study. For a way in see for Philo: Sterling (2017), 243–58; for Origen: Edwards (2002), 61–5; for Gregory: Tollefsen (2010), esp. 175–6; for Basil, Gregory, and their milieu: Sorabji (1988), 44–59; Corrigan (1993). The best survey is that of Karamanolis (2013), 66–107. For early Christian idealist theories see Edwards (2013). For the theological debate see May (1994); McFarland (2014); and the essays in Burrell, Cogliati, Soskice, and Stoeger (2010) and in Anderson and Bockmuehl (2018). ²² See Philo’s treatise Congr., esp. §§73–80; Henrichs (1968); Sterling (2009); Rogers (2014); Roskam (2017). ²³ See Basil’s treatise Ad adulescentes; Gnilka (1984).

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to face on the dialectical battleground of late antique rhetorical polemics: he reversed the charges by contesting the validity and accuracy of Celsus’ own hermeneutical presuppositions. As regards the real meaning of Scripture, however, Origen did not reveal a word more than necessary for his apologetic defence. The reader who was eager to learn more about Origen’s hexaemeral exegesis had to look at the (now mostly lost) Commentary on Genesis.²⁴ We find the same method of explicit deferral to the Commentary in Origen’s other great philosophical treatise, the De principiis.²⁵ Here, however, Origen was a bit more informative as regards his philosophy of nature, giving us three chapters on corporeality, a chapter on the orderly arrangement of the world, and a long section on matter.²⁶ Gen. 1:1–2 appears throughout the discussion, showing that Origen never lost sight of the hermeneutical connection. The latter, however, was the focus of the Commentary, of which we have only fragmentary and often indirect knowledge. That is the reason why two external pieces of evidence are so important for reconstructing the picture, however partial, of Origen’s treatment of the material principle. The first is a fragment from the Commentary preserved in Eusebius’ Praeparatio Evangelica, discussing the craft analogy of the divine Demiurge in conjunction with the question of the pre-existence of matter.²⁷ The second is a long testimony in Calcidius’ section On Matter (De silva) from the Commentary on the Timaeus, elaborating in detail on the pre-existence of matter.²⁸ As a result, we may lament the lost sections of Origen’s Commentary on Genesis. But we may safely conclude that Origen discussed the role of the material principle extensively and exhaustively, in all likelihood in his exegesis of the first two verses of Genesis. Charlotte Köckert has done us an enormous service by studying all the relevant passages and reconstructing, in a coherent narrative, what can be inferred about Origen’s doctrine of matter.²⁹ I will here refrain from repeating that discussion. But I will briefly report on what is necessary, building on Köckert’s report, in order to advance my argument. My purpose will be to show how Origen opened the door for a version of material causality, and hence of a proper hexaemeral physics, after Galen’s and Celsus’ attacks, without compromising divine omnipotence. From what we may deduce from the existing evidence, Origen counterattacked his erudite critics by turning their own argument against them. Remember that for those critics a creationist account based purely on the supposition of divine power and will was not metaphysically solid. Origen undertook to show that it was the other way around. His core idea goes something like this: if matter pre-exists, it imposes external conditions on the exercise of divine will. That undermines the notion of absolute divine freedom, with its correlative of unlimited divine ²⁴ See e.g. CC IV.37, VI.49, VI.51, VI.60. ²⁵ See DP I.3.3, II.3.6. ²⁶ See DP II.1–3, II.9, IV.4.5–8. Add also a couple of scattered but important passages: DP I.4.1, IV.3.15. ²⁷ PE VII.20.1–9 GCS 402.6–403.18 [= fr. D 3 (Metzler)]. ²⁸ In Tim. 276.1–278.16 [= test. C II.1 (Metzler)]. ²⁹ See Köckert (2009), 278–93.

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omnipotence and wisdom.³⁰ Even more crucially, it undermines the coherence of divine creation, making demiurgic divine activity itself contingent on the existence and the properties of a precosmic state of affairs, namely matter.³¹ If one agrees, however, that only an unconditionally free, omnipotent, and extremely skilful Demiurge can also be the absolute foundation of all being, one must further agree that the best way for God to manifest these attributes is for God not only to arrange pre-existing materials in the best possible way but to also create his own materials.³² At this point the craft analogy breaks down, because all human craftmanship is based on materials that are already provided—not so with the divine creator.³³ Origen then retaliates: in making matter dependent on divine will, the Jewish-Christian thinker does not neglect the role of the material principle but puts it in its right place within a theistic framework. In a subtle critique of Galen’s own reading of the Timaeus, Origen responds that the Demiurge did not work with ready-made materials to mould the universe, but that he selected and created these materials. It is because of the unlimited goodness, freedom, and power of divine intelligence that these materials are the best possible.³⁴ It is in this broader context that Origen discusses two views on the nature of the material principle: the view according to which matter is the sum of all (sensible) qualities; and the view according to which matter is the receptacle or material substratum to which qualities are added from without.³⁵ Both scenarios accept

³⁰ Eusebius, PE VII.20.1. ³¹ PE VII.20.3–8. What is here at stake, Origen implicitly but unmistakably suggests, is the (so-called ‘cosmological’) argument for the existence of God (cf. Laws X; Phys. VIII): in order to safeguard unconditional divine freedom, a pre-existent matter would either require the existence of another prime mover, who would be unconstrained, but with a ‘third man’ argument (i.e. a regressio) hanging in the background, collapsing the entire argument (20.4); or it would result in the breakdown of the chain of causality by introducing spontaneity (automaton), next to God, as a universal co-explanans of change, annihilating the whole project of ancient creationist physics (20.6). Since neither option is available to a theist philosopher, Christian or pagan, their rejection leads easily to the design argument (20.8). Origen’s defence brings the whole philosophical arsenal into play, asking his pagan critics to concede that the acceptance of a pre-existent matter brings down their own theistic premises from within. ³² PE VII.20.2. ³³ PE VII.20.9. ³⁴ As Sedley (2007), 113–27, has recently shown, it is possible to read the Timaeus in such a way that the pre-existence of matter does not impede divine freedom, nor is matter the cause of evil. In that reading, the Timaean Demiurge exhibits his brilliant practical reasoning ‘by actually devising the nature of his materials in such a way as to maximize their regularity and causal dependability in achieving his goals’ (p. 118). That the divine Demiurge selected and shaped his materials is a doctrine also shared by Galen, see Tieleman (2005), 131, 134. A comparison between Sedley’s and Galen’s reading of the Timaeus and Origen’s reading of Genesis 1 reveals that we stand in front of a dialectical argument about the best version of the same doctrine. If that is so, Origen actually argues that Moses expressed better what Plato and his followers had in mind. It is the so-called ‘theft of philosophy argument’, going back to Aristobulus (fr. 3) and early Jewish-Alexandrian apologetics, claiming that Greeks stole philosophy from the Jews, see Sterling (2014). ³⁵ See DP IV.4.7. As Edwards (2002), 62–3, rightly observes, these scenarios were not Origen’s inventions but reported by him. That means that the ‘idealist’ theory of matter (first scenario) pre-exists Origen, hence also his younger contemporary Plotinus and the later Gregory too, who are usually considered as the first pagan and Christian expounders of idealist metaphysics, respectively, see Sorabji

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God as the creator of qualities.³⁶ But that is also to say that God is the creator of the materials of the universe. If indeed all individuated being is qualified being, and the whole is the well-functioning sum of its parts, the universe comes to be through the skilled apportioning of the material qualities.³⁷ Such an apportioning requires quantification (‘measure and number’), giving each quality its shape, place, and role in the whole.³⁸ Thus, the emergence of the cosmos as a functioning whole of well-tuned, qualified, and quantified parts manifests the power and practical wisdom—the logos—of the divine creator.³⁹ Origen’s response to the erudite critics of his time fully integrates the material principle in the Mosaic account of the cosmogenesis, while at the same time subordinating its role and function to divine power and will. To the subtle attack that in the absence of mechanical causation there is no room for hexaemeral physics, Origen can now give an even subtler response: divine will is the power upon which hinges all scientific explanation of the world.⁴⁰ To the further possible objection that Origen has, in this way, denigrated matter from the role of a ‘cause’ to a mere ‘enabling condition’, making mechanical causation entirely dependent on divine power and will and depriving the material principle of any independent metaphysical existence of its own, the Alexandrian was not left defenceless. He could respond that the whole purpose of materiality was to enable the manifestation of divine will and power in

(1988), 44–59. Rasmussen (2019), 81–100, 109, 112, has recently advanced the view that Origen in DP IV.4.7 ‘makes it clear that he disagreed’ with the idealist theory (p. 100). This view fails to grasp the dialectical nature of Origen’s argument, namely that the doctrine of the pre-existence of matter is refuted from within both theories. Origen then reports the idealist theory ‘without endorsement or rebuttal’, as Edwards (2013), 578, remarks. But I would even go as far as Edwards (2002), 63, and suggest that the idealist theory might have been Origen’s own preferred theory. It is the theory advanced by ‘those who desire to investigate more deeply into these matters’ (quidam ergo altius de his volentes inquirere), which perfectly corresponds to the spiritually advanced reader of Scripture, such as Origen, who ‘capable of being taught may, by searching out (ereunēsas) and devoting himself to the deep things (tois bathesi) of the sense of the words, become a participant in all the doctrines of the Spirit’s counsel’ (DP IV.2.7 tr. Behr). It should also be noted that the so-called ‘idealist’ theory of matter (for which see also section 2.2.3 below) does not eliminate matter properly speaking, as is commonly but erroneously assumed since the influential paper of Armstrong (1962), 428, but only the material substratum, precisely because the theory identifies matter with the sum of a thing’s sensible properties, see DP IV.4.7: nec materia esse infecta, si quidem qualitates sint omnia. Origen appeals to the idealist theory to substantiate his claim that ‘matter is not uncreated’. Had he maintained that matter is nonexistent, he would have no argument. ³⁶ Expressly so for the first scenario in DP IV.4.7; implied through the statement that omnia, quae sunt, a deo facta esse for the second scenario, see DP IV.4.8 GCS 359.9. ³⁷ See DP IV.4.8 GCS 360.10–361.2. ³⁸ See DP II.9.1, IV.4.8 GCS 359.14–15: Fecit autem omnia numero et mensura; nihil enim deo vel sine fine vel sine mensura est. Origen is reading Wis. 11:20 in light of Tim. 53b4–5 (or, to be more precise, vice versa). On the Demiurge as a good apportioner see DP II.9.6. ³⁹ See DP IV.4.8 GCS 359.20: Virtute enim sua omnia conpraehendit; 360.10–11: Omnis igitur creatura intra certum apud eum numerum mensuramque distinguitur. That this is the work of Wisdom or logos is clear from DP I.2.3 GCS 30.10–12: species scilicet in se et rationes totius praeformans et continens creaturae: hoc modo etiam verbum dei eam [sc. sapientiam] esse intellegendum est. See further Eusebius, PE VII 20.8: tōi technitēi logōi theou. ⁴⁰ This is the foundation of Origen’s logos doctrine, see DP I.2.9–10, and more generally O’Leary (2004). Origen inherits the doctrine directly from Clement, see Karamanolis (2013), 89.

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spatio-temporal terms, communicating the fullness of divine benevolence to rational agents, according to the measure of their ability to grasp it. Origen’s answer to the erudite critics of his time gives shape to the fundamental maxims of all subsequent hexaemeral exegesis: the world is a theophany; creation is contemplation. To the educated reader, the discussion evokes an ambivalence as regards the place of matter in Platonic metaphysics. While Socrates in the Phaedo excluded material causation altogether, classifying the matter involved in a causal process as a necessary condition instead of a ‘cause’ (99a4–b6), Plato in the Timaeus reinstalled matter in the class of causes, identifying Phaedo’s necessary conditions as secondary, ‘auxiliary causes’ (46c7, d1, e7). To put it simply: if Platonizing critics of Scripture like Galen and Celsus could invoke the Timaean metaphysics of matter to attack the hexaemeral narrative, Origen could appeal to the metaphysics of the Phaedo to score a point from within the same school of thought.⁴¹ If my argument is correct, Origen had produced a tremendous defence of hexaemeral physics. In arguing that divine omnipotence manifests in and through the material world, Origen had saved hexaemeral physics from its critics, allowing for a scientific explanation of the world.⁴² The only condition was for the scientist to

⁴¹ The ambivalence concerning the classification of the matter involved in a causal process as a (secondary) ‘cause’ continues in Plato’s later works. Thus, the terminology of primary and secondary ‘causes’ is reprised in the Statesman (281c–282a) as regards productive arts and activities, while in the Laws (896a–897b) Plato seems to reserve the term ‘cause’ only for the activity of soul (896d5–8), speaking merely of secondary, material-bodily ‘motions’, not ‘causes’ (897a4–5), questioning even the appropriateness of the notion of ‘secondary’ as regards their role in change (896b4–8), apparently because bodies do not seem to originally produce motion but only transmit it from one to another (896b4–6). In the latter view, soul is the ruling principle (i.e. the mover) while body is what is ruled (i.e. moved, 896c2–3). The question then seems open for debate from within the Platonic corpus itself. For the hexaemeral tradition, it was Philo who first denied the status of a ‘cause’ to matter, see Runia (1986), 143–4, 454–5; Runia (2001), 115–16 (remarks on Opif. §8); and now the paper of Sterling (2017), 243–57. Origen, here, is clearly developing a Philonic position. Plotinus is doing the same from within the Platonist camp, see Perdikouri (2014), 33–7, 168–71. ⁴² To be absolutely clear, I am not suggesting, here, that Origen was the first to produce a hexaemeral physics or include elements of physics in his hexaemeral exegesis. That would be a grave misunderstanding of the preceding and parallel tradition, cf. Philo’s Opif. and Theophilus’ Autol. II.11–9. I am merely suggesting that Origen was the first to respond to philosophical attacks on the coherence of a notion of hexaemeral physics (and hence of a scientific explanation of the biblical world) if material causality is rejected and divine benevolence and omnipotence are accepted as the sole causes of materiality. This does not exclude a further layer of argumentation in which Origen would be answering previous critics by making recourse to the new interpretation of creation ex nihilo as creation from absolutely nothing, if we accept, with Tieleman and May, that this development was not available at the time of Celsus and Galen, see my discussion above in section 2.1. In my view, however, Origen’s doctrine of a creatio aeterna, for which see Bostock (2007), 222–7; Behr (2017), lvi–lxii, allows for both interpretations of the creation ex nihilo, as creation from nothing in particular and absolutely nothing, a point that Gregory of Nyssa will spell out later through his substratum and idealist theory of matter, respectively, for which see right below. For this reason, I do not think that we can make sense of the hexaemeral physics by focusing only on the question of the creation of matter. The latter approach would be rather one-sided, leaving big questions open as regards the metaphysics of Origen and Gregory. In my view, the real (and intellectually stimulating) point of controversy was about the ontological status of matter as a ‘cause’ or not. Only after this status had been effectively denied could one argue for a creation out of nothing other than the power of God, regardless of how one would exactly understand that ‘nothing’.

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realize that the role of all enquiry into nature was to lead the enquiring mind anagogically from the study of the natural world to the study of its divine cause. But that is phusikē theōria, the very essence of the hexaemeral project, as we saw in Chapter 1. In subordinating materiality to the divine will, Origen had turned physics into the threshold of hexaemeral hermeneutics. It was Gregory of Nyssa who, in the late fourth-century context of post-Nicaean orthodoxy, would creatively appropriate most of Origen’s physical thought.⁴³ In his Apology on the Hexaemeron, Gregory would reiterate the basic tracks of Origenian thought and spell out the consequences for the hexaemeral physics of light. It is to Gregory, then, that I shall now turn.

2.2.2 Introducing Gregory’s Apology Gregory’s Apology is, in many respects, a riddle. It has attracted the attention of some of the greatest patristic scholars and yet the work itself, its genre, its purpose, and its place in patristic literature, if not also the content, remain obscure. The obscurity goes a long way back. Only about a generation after the work was written, the church historian Socrates made a brief remark in his annotated chronicle stating that, after Basil’s death, Gregory ‘completed Basil’s Hexaemeron, which had been left unfinished’.⁴⁴ It is customary to think that Socrates here alludes to the Apology.⁴⁵ Under this assumption, however, lies a confusion between Gregory’s two works: the De hominis opificio, which was written with the explicit purpose of fulfilling Basil’s promise of a further discourse on the creation of humankind;⁴⁶ and the subsequent Apologia in Hexaemeron, ⁴³ In a remarkable paper, Andrew Radde-Gallwitz (2017) has filled in the gap between Origen and Gregory by providing a detailed analysis of Basil’s riposte to Galen’s critique. My argument fully concurs with Radde-Gallwitz’s analysis of Basil’s physical thought. Radde-Gallwitz, however, downplays the role of Origen in providing a fully Christian, exegetically rigorous, and philosophically robust riposte to Galen and Celsus, claiming that Origen eschewed the challenge by having recourse to allegory (pp. 202–3; cf. also 210). In this section I have argued for the contrary position. In what follows, I further argue for: 1) the continuity between Basil’s and Gregory’s views on material causality; and 2) the dependence of Basil’s and Gregory’s views on Origen. The difference between the two assessments of Origen hinges upon how one understands the relevant passages in the Contra Celsum (cited at the beginning of this chapter). I take the passages to refer to the analytical Commentary on Genesis, the content of which we may (partially) reconstruct from the existing fragments and the parallel sections of the De principiis. Radde-Gallwitz takes the passages to refer to the hexaemeral (first) Homily on Genesis (p. 202 n.15). In my view, the recourse to the hexaemeral Homily is misleading here because, unlike the Commentary and the De principiis, it does not expound Origen’s metaphysics. It is rather an exercise in moral Christocentric allegory, as Radde-Gallwitz also accepts and as I have already indicated in Chapter 1, section 1.3.3. The Homily therefore serves Origen’s catechetical project much better than the apologetic purposes of the Contra Celsum. If I am right, the Commentary on Genesis expounds Origen’s metaphysics of creation. It is there that we find Origen’s response to Galen and Celsus and the continuity between Origen’s, Basil’s, and Gregory’s hexaemeral physics (for which see this and the next section, esp. section 2.2.3 in fine). With the above caveat, my Origenian reading of Basil and Gregory comes strikingly close to RaddeGallwitz’s reading of Basil. For another caveat see Chapter 3, section 3.4.1. ⁴⁴ Socrates, Hist. Eccles. IV.26.27 GCS 262.20–1. ⁴⁵ See e.g. Risch (1999), 1. ⁴⁶ See Basil, Hex. IX.6 GCS 160.14–15; Gregory, Hom. opif. Preface, 1–2 Forbes 104 (= PG 44:125C). See also Chapter 1, section 1.3.3.

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whose purpose was not to continue Basil’s project, which had just been completed with the Hom. opif., but to expand on it. Gregory set himself a new aim in the Apology: to answer several objections raised to Basil’s literal interpretation of the scriptural narrative by exploring the inner structure (the akolouthia) of creation.⁴⁷ Going back to Socrates’ statement, we may observe that the passage quoted refers to the Hom. opif., the only supplement to Basil’s Hexaemeron, while the Apology, the defence and expansion, is not mentioned at all. Socrates is an early witness to the fact that the Apology has often, though not always, been overshadowed by the influence of the Hom. opif. in the reception history.⁴⁸ It will be the future task of the historian to distinguish between the influence of Gregory’s two hexaemeral works in the patristic literature.⁴⁹ In current scholarship, the Apology has had a fascinating but turbulent career. For Karl Gronau it was important to argue, against Gregory’s explicit intentions, that the Apology is a continuation and, in some respects, the culmination of Basil’s hexaemeral project.⁵⁰ This gave further support to Gronau’s thesis that Posidonius’ (alleged) Commentary on the Timaeus was the common source behind late antique biblical and Platonic exegesis.⁵¹ Gronau’s position was later attacked from multiple sides. As regards the method of ‘source hunting’ (Quellenforschung) underlying Gronau’s work, the majority of English-speaking scholars gradually contested and eventually abandoned the ‘Posidonian frenzy’ that marked the first half of the twentieth century, rendering Gronau’s argument dated.⁵² Gronau’s particular reading of Gregory was also attacked by E. Corsini, who, in an influential article, suggested that Gregory only pretended to ⁴⁷ See In Hex. 6 GNO 14.9–12; 77 GNO 83.10–84.14. ⁴⁸ For example, according to O’Meara (1998), 76, 78, ‘Eriugena’s use of Gregory of Nyssa is confined to the De opificio hominis.’ But Eriugena’s remark in Periphyseon I.521a27 on ‘the nature of light, which is fire’ (naturam lucis quae est ignis) cannot be derived directly either from Basil’s Hexaemeron or from Dionysius’ Celestial Hierarchy, which are mentioned by Eriugena in this context, nor from Gregory’s Hom. opif., but only through a reading of Basil’s Hexaemeron through Gregory’s Apology, see Katsos (2021). Another example: Grosseteste, In Hexaemeron I.XVI.3, refers to a view attributed to Josephus, Gregory, and other anonymous hexaemeral commentators, according to which, contrary to the standard interpretation of Jerome, Strabus, Bede, John Damascene, and Basil, the firmament of the second day is the same as the heaven of the first day. In his annotated translation, Martin (1996), 74 n.4, mentions as Grosseteste’s source the first chapter of Gregory’s Hom. opif., which offers a recapitulation of the creation narrative from Gen. 1:1 to 1:26. But there is no discussion there of the relation of the ‘firmament’ [Gen. 1:6] to ‘heaven’ [Gen. 1:1], even less an allusion to their identification, nor anywhere else in the Hom. opif., as far as I can tell. The only source that Grosseteste could derive that information from Gregory is through some reading of the Apology. ⁴⁹ For a detailed discussion of the influence of the Apology in the reception history and contemporary scholarship see Risch (1999), 46–52. ⁵⁰ See Gronau (1914), 5. ⁵¹ See Gronau (1914), 112–41. ⁵² For the changing of the tide in Posidonian scholarship see the groundbreaking paper of Edelstein (1936), 286–325; for the current, much more balanced assessment on Posidonius’ influence see Dillon (1996), 106–13; on the hypothesis of a Posidonian Commentary on the Timaeus, which was the foundation of Gronau’s thesis, see Kidd (1988), 337–43, esp. 339: there is no sure evidence that Posidonius wrote a separate commentary on the Timaeus, nor that he did not. Hence Kidd classifies the much-debated fr. 85, which is the main textual evidence of a direct Posidonian exegesis of the Timaeus, under the dubia. Gronau’s thesis, however, continues to be popular in German scholarship, see Risch (1999), 52–5.

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clarify Basil’s positions further, while in reality he promoted a different, personal agenda.⁵³ For Corsini, Basil and Gregory could not have used the same original source, disproving Gronau’s Posidonius thesis.⁵⁴ In the subsequent discussion, scholars have often followed Gronau’s or Corsini’s argument, with certain modifications, especially as regards the Posidonius thesis.⁵⁵ Peter Bouteneff, for example, adopts the continuity argument, according to which the Apology and the Hom. opif. elaborate or complete Basil’s hexaemeral homilies.⁵⁶ For Bouteneff, the Apology is intended for a different audience from Basil’s, allowing Gregory to use ‘a more technical and scientific level of discourse’.⁵⁷ At the same time, the Apology builds on ideas already present, even if only latent, in Basil’s work, like the simultaneity (athroon) and sequential order (akolouthia) of creation or the double aspect of creation (intelligible and sensible).⁵⁸ Doru Costache, on the other hand, follows the discontinuity argument, contesting that the real intention behind the Apology was to defend or expand Basil’s Hexaemeron.⁵⁹ Instead, Gregory ‘used Genesis as a pretext for his own discourse’.⁶⁰ Gregory’s real purpose was twofold: to assert his own scholarly standing against the memory of his brother and to bridge the scriptural and the scientific worldviews, showing that the biblical worldview could raise a respectable voice in the scientific and cosmological debates of the time. Costache therefore challenges the established view of the Apology as an exegetical work, arguing that it mainly serves an apologetic purpose.⁶¹ The examples aim to show that the interpretation of the Apology is still open to debate.⁶² In Bouteneff ’s words: ‘It is, in many respects, a puzzling text.’⁶³ In the limited scope of the current chapter, I cannot begin to do justice

⁵³ See Corsini (1957). ⁵⁴ Corsini’s conclusion is that Basil and Gregory drew independently from many sources, like Cicero, Philo, Seneca, Posidonius, Panaetius, etc., with the use of multiple doxographic material and scholastic handbooks as most probable (pp. 102–3). ⁵⁵ For an overview see Risch (1999), 1–2, 52–5: though the importance of Posidonius is not contested in its entirety, he is no longer regarded as the ur-source of hexaemeral literature. ⁵⁶ Bouteneff (2008), 154. ⁵⁷ Bouteneff (2008), 155. ⁵⁸ Bouteneff (2008), 155–6. ⁵⁹ See Costache (2013a), esp. 378–83, with the explicit adherence to Corsini’s view on p. 382. The view was developed further in Costache (2013c). ⁶⁰ Costache (2013a), 386. ⁶¹ Costache (2013a), 383–91; (2013c), 1–7. ⁶² Corsini’s key argument that Gregory’s Apology contradicts Basil’s Hexaemeron has recently been heavily criticized by Risch (1999), 5–9, 54–5. But Corsini’s argument is also the foundation of Costache’s reading of the Apology. Similarly, Costache’s emphasis on Gregory’s scientific agenda has been anticipated and called into question by Risch (1999), 50–1 (discussing earlier German scholarship). Conversely, Risch (1999), 55, is much more positive to the idea of a Posidonian influence than most English-speaking scholars would allow. Meanwhile, O’Brien (2015) and DeMarco (2013) have expressed intermediate positions. They both acknowledge the continuity between Basil’s and Gregory’s hexaemeral projects, but they also affirm the divergence as regards the interpretation of the upper waters. Lollar (2013), 120–37, oscillates between commonality regarding the theory of matter (p. 133: ‘similar line of thinking’) and divergence regarding the hexaemeral project (p. 134: ‘very different’; p. 135: ‘quite different’), while his final view remains unclear (p. 137). I express my own opinion in Chapter 3, section 3.1.3. ⁶³ Bouteneff (2008), 154.

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to the complexity of the questions raised in the text. On the other hand, I cannot afford to ignore its unique importance for the discussion of hexaemeral physics. Taking stock of the different approaches to the Apology, there is at least one thing that seems common to all: the central role of material causality, with a special focus on light, whether in the context of the discussion of the nature of the heavenly bodies (Gronau), the doctrine of universal conflagration (Corsini), the theory of the four elements with its direct bearing on fire, light, and water (Bouteneff), or Gregory’s aim to bridge the Christian and the scientific worldview (Costache). I shall therefore only approach the text from a specific viewpoint, that of the hexaemeral physics of light, fully aware that in skipping over several interpretative difficulties my treatment may seem provocative, inadequate, or both. For the purposes of my discussion, I shall treat the Apology as a philosophical commentary on the biblical creation narrative, building on Basil’s homilies and continuing Origen’s apologetic agenda.⁶⁴ But first a note on the overall plan, aim, and structure of the treatise.

2.2.3 Approaching Nature through the Lens of Scripture: Physics as Hermeneutics The Apology opens with a series of questions addressed to Gregory by his younger brother Peter, later the bishop of Sebastia, triggered by Basil’s literal hexaemeral exegesis. Here is a synoptic overview of the questions asked. 1) If the revolution of the sun is the cause of day and night, and the sun is created on the fourth day, how ⁶⁴ Though a proper discussion exceeds the scope of this chapter, let me say, at least, why I suggest the solution of a philosophical commentary. Convincing as I find Costache’s arguments on the apologetic nature of the treatise to be, it is not clear to me why he excludes the possibility of an exegetical commentary also serving an apologetic purpose, as is the case with Philo’s De opificio, or of an apologetic treatise also having exegetical value, as is the case with Theophilus’ Ad Autolycum (Book 2). In my view, there is ample evidence to suggest that the Apology combines material from (and the style of) the biblical commentary tradition on Genesis and the commentary tradition of the schools on the Timaeus. Gronau (1914), 114–15, is still helpful in this respect because he shows that Gregory’s views on material causality come very close to Calcidius’ Commentary on the Timaeus, while Alexandre (1976), 178–80, has suggested Origen’s Commentary on Genesis as the common influence behind the corresponding passages in Gregory and Calcidius. For this reason, I propose to take seriously Gregory’s own remarks about the nature of his treatise (In Hex. 6 GNO 13.7–4.12), namely that it is modelled after a school exercise (ōs en gumnasiōi tini scholastikōs), which proceeds argumentatively (eggumnazein tēn dianoian), investigating the ‘grammar’ of creation (sunērtēmenēn tina kai akolouthon theōrian) without raising any doctrinal claims of an authoritative exegesis (ou didaskalian exēgētikēn). See for a similar interpretation Köckert (2009), 400–6, esp. 405–6. In my view, the Apology is nothing short of a diatribē on Genesis 1. It stems from Gregory’s own meditation on creation, his phusikē theōria. This allows for Costache’s emphasis on the apologetic component, next to the exegetical component recognized by the prevalent view, see e.g. Alexandre (1971); Simonetti (2010), 331. Gregory’s constant emphasis on the akolouthia of the scriptural text is, in my view, the ultimate argument in favour of the Apology’s undeniable exegetical character. And again, the emphasis on the akolouthia, skopos, and dianoia of the text, rather than the lexis, proves that Gregory’s exegesis is philosophical rather than philological. For these reasons I fully concur with the discussion and assessment of Risch (1999), 1–11, 49: the Apology is at the same time an exegetical, apologetic, and philosophical work. In what follows, I will not question further the exegetical character of the Apology.

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is it possible to speak of three preceding days (and nights)? 2) If the creation narrative refers to only two heavens (Gen. 1:1 and 1:8), why does Paul introduce a third (2 Cor. 12:2)? 3) If God commanded the creation of light (Gen. 1:3), how did darkness exist without a divine command? 4) Building on (1), if the presence of light is enough to account for the change of day and night, why did God create the sun? 5) If ‘creation’ (poiēsis) and ‘formation’ (kataskeuē) denote the same thing, how is it possible that the earth which was ‘created’ (Gen. 1:1) in the beginning together with the heaven is nevertheless ‘unformed’ (Gen. 1:2a)? 6) Assuming, with Basil, that the ‘waters’ of Gen. 1:7 refer to physical water, how is it possible for water to remain on top of the circular and rotating heavens without falling? 7) If heavenly fire is constantly nourished by vaporized water, as Basil suggests following the Stoic theory of exhalations, how is it possible for the mass of fire and water in the universe to remain the same without the one element devouring the other?⁶⁵ The questions raise objections similar to those put forward by Celsus and Galen against the ‘logic’ of the biblical creation narrative.⁶⁶ They bring to surface logical contradictions that arise from the literal reading of Genesis. In other words, they contest the coherence (heirmos) and consistency (akolouthia) of the scriptural text. At the same time, they question the existence of mechanical causation: if there is light, days, and nights without the sun, why would the world need a sun at all? If the sun is the cause of day and night, how can there be three days before the sun comes into existence? And so on. It is precisely the kind of inconsistency that Augustine wrestles with in his Commentary ad litteram, constantly making the reader aware of the tremendous challenge of a purely literal reading of the biblical creation narrative.⁶⁷ From Origen to Augustine, the hexaemeral exegetes strive to

⁶⁵ See In Hex 3 GNO 8.12–9.15 and 5 GNO 11.8–12.22. ⁶⁶ The objections are already an ancient problem by the time of Gregory, going at least as far back as Hellenistic Judaism, see Kugel (1998), 72, with reference to Jubilees 2:2 and the Qumran Hymn to the Creator 11QPsa. Nevertheless, the charges were continuously reprised and actualized in different subsequent intellectual contexts, as the examples of Galen and Celsus show. In the second half of the fourth century the charges were more or less emphatically repeated by Julian (see section 2.1 above). That is not to say that Peter serves as a pagan mouthpiece. Augustine’s ambivalent stance towards the literal reading of Genesis 1 (for which see the next note) shows that Peter articulates genuine aporiai from within mainstream Christian theological circles as to whether Basil’s project represents the best exegetical strategy in addressing the issue. Gregory’s defence aims to satisfy a twofold audience: Christian sceptics and non-Christian critics. ⁶⁷ See e.g. Gen. ad lit. I.3.7: whether the light of Gen. 1.3 is spiritual, corporeal, or both; 12.24–5: how can there be evening and morning before there is a sun; 15.31: rejection of a physical explanation (contraction and emission of light) in favour of a spiritual; 17.32–5: allegorical interpretation (sin and redemption) distinguished from spiritual interpretation: the work of the first day refers to the creation of the intelligible world, that of the second and third to the visible world (heavenly and earthly realm, respectively), followed by metaphysical interpretation (ordered succession of things); 19.38–9: spiritual interpretation ranks higher than physical explanation; II.1.1–4: how there can be waters above the sky: priority of figurative interpretation over physical explanation; 4.7–8: Basil’s physical explanation supported; 13.26–7: reaffirmation of the spiritual interpretation of the first three days, etc. It is therefore no surprise that the literal reading appears to the early Christian mind as ‘most laborious and difficult’ (Retract. I.18.1), forcing a more aporetic than affirmative stance towards the proper sense of Scripture (Retract. II.24), while leaving open the resources of allegory, when needed.

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come up with a convincing answer to the problems posed by the letter of the scriptural text.⁶⁸ Gregory’s questions epitomize these problems.⁶⁹ Interestingly, four out of the seven aporias (five, if we consider heaven as the luminous space par excellence) concern the biblical physics of light. The questions are exegetically formulated, subordinating the hexaemeral physics to the needs of scriptural interpretation. Gregory’s answers follow the opposite pattern, subordinating the aporiai to the physics of the creation narrative. The questions are answered not in the order they are asked, but in the order that the cosmogony unfolds.⁷⁰ This reveals the inner structure of the treatise. The Apology is a reflection on nature, or, if you like, a disquisition on materiality, starting with the question of matter (§§7–9), continuing with that of the physical elements (§§10–27), their generation and corruption, with an emphasis on the circle of water (§§28–63), moving on to the heavenly bodies (§§64–74), and finishing up with the vision of Paul’s third heaven (§§75–6). A proem (§§1–6) and an epilogue (§§77–8) contextualize Gregory’s discourse within the hermeneutical framework ⁶⁸ A comparison with contemporary developments in Platonist hermeneutics is instructive. Famously, Porphyry used allegory to deduce an ethical reading from the Timaeus, while Iamblichus retaliated with a ‘literal’ interpretation vindicating the primary skopos of the Timaeus as a work on physics, see Larsen (1972), 390–4. We see the two approaches complementing each other in Origen and Augustine. Origen’s first Hom. Gen. and Augustine’s Gen. c. Man. employ the same kind of moral allegory as Porphyry. By contrast, Origen’s (mostly lost) Com. Gen. and Augustine’s Gen. ad lit. emulate the Iamblichean project, shifting towards a physical explanatory scheme. The latter remains open to allegorical and analogical-spiritual interpretation, identifying for example the primordial elements of the hexaemeral narrative (‘heaven’, ‘earth’, ‘waters’, etc.) with intelligible realities, as long as the physical explanatory framework is preserved, see Larsen (1972), 397–8, for Iamblichus; Hill (2002), 157–62, for Augustine. For all these authors, exegesis occurs dialectically between two planes, literal and allegorical, as Martens (2008) has convincingly argued at least in the case of Origen. But it is important to note that the mode of language (allegorical or literal) is also linked to a certain skopos of the text (ethical or physical). The shift of the Cappadocian project is clear: Basil wants to bring back all possible skopoi of the text to the proper sense of Scripture, investigating the deeper sense of Scripture without allegory, see Chapter 1, section 1.1.1. It is this commitment to the proper sense that Gregory sets out to defend. Thus, the Cappadocian project represents an apogee of early Christian literal (though not literalist) exegesis, in that it aims to defend the coherence of the scriptural text, and of its metaphysical underpinnings, at the level of the proper use of language. Today we are unaware of this tremendous exegetical achievement, because modernity trained us into thinking of the proper sense (‘letter’) as the most obvious and least expensive hermeneutical approach to the scriptural text, treating it independently from its metaphysical or ‘deeper meaning’ (‘spirit’), as shown in the epoch-making essay of Louth (1983), esp. 96–131. By contrast, a sustained and comprehensive non–allegorical reading of the cosmogenesis is the least obvious and hermeneutically most expensive path for an interpreter who is committed to a metaphysical reading of Scripture, as is the case in early Christianity. To the question of what prompts Basil to take this challenging route, Niehoff (2018), 108, provides an insightful answer: the need to defend the cogency of the biblical creation narrative over against pagan allegorical readers of the Timaeus, such as Porphyry and Julian. If we now recall Julian’s philosophical connection to Iamblichus, it is possible to provide an answer to one of the most puzzling questions in Basilian hexaemeral exegesis: the rejection of all allegorism, see Lim (1990); Hildebrand (2007), 122–39. Clearly, the Cappadocian hexaemeral project is intended as a reaction not only to the allegorical reading practices of the Porphyrian type but also to the ‘literal’ reading practices of the Iamblichean type, which remain open to physical allegory. For the competition between pagan and Christian readers of the Timaeus in late antiquity see Niehoff (2007). ⁶⁹ See Risch (1999), 6: The questions were not invented by Peter but appear again and again in hexaemeral exegesis. They predate Basil. ⁷⁰ See Risch (1999), 22–3.

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of questions and answers based on Basil’s hexaemeral homilies.⁷¹ As Risch has convincingly shown, we stand in front of a bottom-up contemplation of nature (phusikē theōria), starting with the densest form of materiality, namely earth, and moving upwards, through water and air, to the finest forms of corporeal existence, namely the fiery planets and stars of the ethereal and sidereal region, until we reach the highest heaven, Paul’s paradise. Risch rightly sees in this ascending motion of the intellect, from earth to heavenly fire and beyond, an early intimation of Gregory’s signature idea of epektasis, the constant stretching and perpetual progress of the soul. It is the idea animating the structure of Gregory’s response.⁷² The juxtaposition between Peter’s questions, which are based on the scriptural text, and Gregory’s answers, which are based on his contemplation of nature, creates a chiasm running like a thread through the whole treatise. As the reader goes back and forth trying to match each question with its appropriate answer, what emerges is the idea of narrative logic as the guiding principle of interpretation, manifested further in the hermeneutical subprinciples of coherence (heirmos), consistency (akolouthia), and overall structure (taxis) of the text, revealing its aim or purpose (skopos).⁷³ In placing the narrative logic—or the ‘grammar of creation’—between the text and the world, Gregory suggests that the key to a comprehensive contemplation of nature is, essentially, hermeneutical. I want to take some liberty in reconstructing this aspect of Gregory’s thought, because some of it belongs to the subtext of the Apology. After all, this is a philosophical treatise addressed to erudite readers. Gregory’s aim is to prompt his readers to think. His argument goes something like this: from a non-theistic perspective, we cannot find any rhyme or reason in nature—it is all a product of tuchē (luck).⁷⁴ In order for a philosophical investigation into nature to be conclusive, we need to adopt a theistic framework (cf. ‘cosmological proof ’). That was Moses’ great insight on the Mountain.⁷⁵ In order to help his readers find their way through the chaotic phenomena of the world, Moses wrote down the key in the form of a

⁷¹ I here follow the analysis of Risch (1999), 16–20. ⁷² See Risch (1999), 23–4. As becomes clear from §76, which contains the vocabulary of epektasis, the contemplation does not stop at the boundaries of the physical world but stretches beyond, entering the intelligible realm, Paul’s third heaven. See also 5 GNO 12.22–13.6 with a rather didactic suggestion as to how Peter would achieve real epektasis. ⁷³ See In Hex. 4–6 (skopos, akolouthia, to akolouthon); 9 (heirmos, taxis, akolouthia, to akolouthon). ⁷⁴ See In Hex. 9 GNO 19.5–6; 17 GNO 29.12–17, which reprises the traditional hexaemeral attack against materialism, identified at the time with Epicurean atomism, see Basil, Hex. I.1 and I.7, and the comments of Risch (1999), 148–50 n.123 and 176 nn.188–90. ⁷⁵ See the references to Moses’ contemplation of nature (§1) and philosophical ascent on the mountain (§5). The allusion to the ‘cosmological proof ’ (or rather the theistic framework of contemplating nature, which, philosophically speaking, presupposes some version of the cosmological argument, e.g. of the sort we find in Laws X or Phys. VIII) is made through the reference to Basil’s first hexaemeral homily (I.1) and, much later, through Gregory’s own explanation of Moses’ life, see e.g. Vit. Mos. II.25, 152–61. Gregory informs his readers multiple times that the hexaemeral contemplation of nature is a philosophical one: tōn en tēi kosmogoneiai philosophēthentōn (1 GNO 6.1–2; 6 GNO 13.13–14); pephilosophēmenōn (1 GNO 6.8–9); dia tēs hypsēlēs philosophias (1 GNO 7.2–3).

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creation narrative.⁷⁶ The key to the narrative is the idea of a necessary order (akolouthia) revealed in the six ‘days’, i.e. the six stages or episodes of creation— the hexaemeron.⁷⁷ The aporiai that emerge from the text only make us think harder on the meaning of akolouthia and how it applies to nature.⁷⁸ That is Moses’ guide to the perplexed. In approaching nature through the prism of Scripture, we approach the world as a coherent whole that has a beginning, a middle, and an end, serving a certain purpose. In other words, we unlock the meaning of nature by reflecting on the heirmos, the akolouthia, and the taxis of the universe.⁷⁹ Gregory argues that the same hermeneutical principles apply to the interpretation of Scripture and the interpretation of the world.⁸⁰ For Gregory, then, we are hermeneutically contingent creatures. We make sense of material phenomena by interpreting them. And we learn the principles of interpretation by reading Scripture, wrestling with the question of meaning.⁸¹ To speak of ‘creation’ is to already look ⁷⁶ See In Hex. 8 GNO 17.2–6. ⁷⁷ On the principle of akolouthia see the magisterial essay of Daniélou (1953) still setting the tone. On the principle of skopos see the informed discussion of Heine (1995), 29–49. See also the excellent treatment of both in the introductory notes of Norris (2012), xxix–xxxviii (skopos) and xxxviii–xliv (akolouthia). For the current state of discussion see Gil-Tamayo (2010a). As Daniélou has shown, akolouthia is a word with a fluid range of meanings, denoting literally ‘what follows’ or ‘what comes next’, always in the sense of necessary and progressive correlations between the parts of a well-ordered and coherent whole. It is thus usually translated as ‘sequence’, ‘series’, or ‘succession’. Another possible range of meanings is that of ‘connection’, ‘junction’, ‘coordination’, ‘concatenation’. It is closely connected to the terms heirmos (lit. ‘chain’) and taxis (lit. ‘order’), together with which it denotes the inner coherence, consistency, and well-ordered structure of a whole (e.g. a speech, a text, an argument, an artistic creation, or even nature). From the point of view of hermeneutics, the term denotes the unfolding of the different episodes of a narrative, revealing a systematic and methodological unfolding of the plot. The term goes back to Stoic logic (though Gregory mentions it in an Aristotelian context at least once, see C.Eun. I.46 GNO 37.19–38.2) but its use in a hexaemeral (i.e. both cosmological and hermeneutical) context is undoubtedly Philonian, see Opif. 28: ‘Order (taxis) is a sequence (akolouthia) and series (heirmos) of things that precede and follow, if not in the completed products (apotelesmasin), then certainly in the conceptions (epinoiais) of the builders’ [tr. Runia with the helpful comment in (2001), ad loc. (p. 160)]. I here refrained from translating the term unilaterally in order to capture something of its extremely nuanced and versatile use by Gregory. ⁷⁸ See In Hex. 1 GNO 6.4–5 (dia tinos akolouthou dianoias eis heirmon agagein). ⁷⁹ See e.g. In Hex 5 GNO 11.8–9 (tēn anagkaian tēs ktiseōs taxin); 6 GNO 14.11–12 (akolouthon en tēi ktisei tōn gegonotōn epinoēsai tēn theōrian); 9 GNO 18.16 (heirmos tis anagkaios kata tina taxin); 9 GNO 19.7 (hē anagkaia tēs phuseōs taxis); 77 GNO 83.14–15 (tōi tēs phuseōs heirmōi). ⁸⁰ See In Hex. 6 GNO 14.10–12: Gregory enquires ‘whether it is possible for us, with God’s help, to keep the letter of the text as it is (menousēs tēs lexeōs epi tēs idias emphaseōs) and along with it, following its sequence (sunērtēmenēn tina kai akolouthon), contemplate the events of creation (en tēi ktisei tōn gegonotōn epinoēsai tēn theōrian)’. The answer is affirmative: everything was brought to completion by a certain necessary heirmos (pattern) according to a certain taxis (order), ‘not by haphazard chance (ouk automatōi tini suntuchiai), appearing randomly and without order, but following a sequence (to akolouthon) as the necessary order of nature (hē anagkaia tēs phuseōs taxis) requires of everything that partakes of becoming. This is how Moses said that everything was made, expounding in narrative structure the doctrines of natural philosophy (en diēgēseōs eidei peri tōn phusikōn dogmatōn philosophēsas).’ It is precisely this chain of natural causality that the narrative structure of the biblical creation narrative mirrors (77 GNO 83.14–15). Contemplation of nature goes hand in hand (sunagoreuein) with contemplation of Scripture (77 GNO 84.10–14). ⁸¹ In a fascinating paper, Catherine Rowett has shown that there is ‘an analogy between Timaeus’ act of describing a world in words and the demiurge’s task of making a world of matter’, see Osborne (1996), 179 and 203–11. The parallel between contemplation of Scripture and contemplation of nature has, then, clear Timaean resonances, namely the analogy between language and the world. Hexaemeral

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upon the world from a certain viewpoint. It is the viewpoint—viz. the theōria—that Moses acquired when he looked at the world from the top of Mount Sinai.⁸² I have dwelt a bit longer on the overall plan and purpose, the akolouthia and skopos, of the Apology because they hold the key to Gregory’s approach to hexaemeral physics. At the heart of the issue lies the question of materiality. We are entering here a much-disputed terrain of Nyssen studies and it is not my intention to reprise the whole discussion.⁸³ But it is important to acquire a taste, at least, of how Gregory deals with the most fundamental question of hexaemeral physics. Remember that Origen reported two different views on matter, a bundle theory and a substratum theory, as alternative metaphysical possibilities. Gregory builds on Origen’s exegetical strategy by restating both models (idealist and substratum), yet with a subtle nuance that appears to disturb the exegetical balance. For Origen the two theories were derived from two different exegetical traditions, not raising any claim to being consistent with each other. With Gregory the two theories become part of the same unified exegesis of the creation narrative.⁸⁴ This raises the issue of compatibility.⁸⁵ Some of the best Nyssen scholars see an unsolvable difficulty here: if matter is the substratum that receives qualities, it cannot be that matter is the sum of all qualities.⁸⁶ It seems, however, that there is more to Gregory’s dialectical strategy than first meets the eye. For Gregory does not try to fuse the two parallel doxographies into one, suggesting that matter is both the substratum and the concurrence of qualities in one and the same respect. Instead, he takes great care to distinguish between the two models as two different angles from which one could approach the question of materiality.⁸⁷ In one interpretation unfolds within a ‘languaged cosmos’ (see Schott 2015), which articulates the Christian version of ‘linguistic cosmology’ (see Coogan forthcoming), distinguished from competing accounts through the key doctrine of creatio ex nihilo (see section 2.1 above). ⁸² For Sinai as the symbolic mountain of knowledge of God see Vit. Mos. II.152, 158. For the use of the metaphor in the Apology see 5 GNO 11.5–10. Moses’ ascent becomes the symbolic expression of the ladder of knowledge of the philosophers. It is the ascent of the intellect from perceptual to intelligible reality, working its way upwards from the sensible realm to the intelligible and from one proximum movens to the next until it reaches the divine prime mover. The chain of causality that leads to the prime mover is the heirmos and the movement along the chain of causation is the akolouthia of nature. The suggestion is that contemplation of nature, and hence the whole plan of the Apology, is a meditation repeating the stages of the argument for the existence of God. We are at the heart of the early Christian natural theology. ⁸³ For an informed overview of the status quaestionis see Costache (2013c), 14–27. ⁸⁴ See In Hex. 7 GNO 16.4–11 (idealist theory); 16–17 GNO 27.10–29.11 (substratum theory). The first model is developed as part of the exegesis of Gen. 1:1, the second as part of the exegesis of Gen. 1:2a. The transition from the one model to the other is made in 16 GNO 26.14–27.9 through a brief recapitulation of the exegesis of Gen. 1:1 before proceeding to Gen. 1:2a. ⁸⁵ The question has triggered the seminal paper by Alexandre (1976), 159–86. ⁸⁶ See Alexandre (1976), 184–6; Köckert (2009), 432–6, 433: ‘Der Widerspruch . . . lässt sich nicht auflösen’. ⁸⁷ Gregory’s dual aspect epistemology is certainly not innovative, see already Philo’s Opif. 13, 28, 67, and the comments of Runia (2001), ad loc.: sub specie aeternitatis, everything was created simultaneously; sub specie temporis, however, creation is envisaged as an ordered sequence of events. For Gregory’s adaptation of the same exegetical motif see Costache (2013c), 22–7 (‘creation as one event and as a series of events’). In my reading, however, Gregory goes a step further in directly connecting

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respect, matter can be theorized as the simultaneous (homou) concurrence (sundromē) of certain conceptual ingredients: 1) pairs of opposite qualities, such as heaviness and lightness, rareness and denseness, softness and hardness, wetness and dryness, coldness and hotness; 2) special sensibles, like colour; 3) common sensibles, like shape and outline (tēn perigraphēn);⁸⁸ and 4) interval or extension (to diastēma). These are the materials that God produced in order to bring material existence instantaneously into being (sullēbdēn ho theos en akarei katebaleto).⁸⁹ In another respect, however, matter can be theorized as the substratum (hupokeimenon) that receives the qualities, being itself devoid of any particular or determinate quality.⁹⁰ It is difficult to understand exactly why this dual approach has caused so much controversy and misunderstanding in Nyssen scholarship. It only takes a simple look just a bit outside of the Apology to realize that the two approaches go a long way back to the interpretative tradition of the Timaeus and are commonly discussed in the relevant philosophical literature.⁹¹ If nothing else, the alleged ambiguity is already found in Aristotle’s discussion of Plato’s receptacle.⁹² Basil himself alludes at least twice to this discussion but does not want to enter into details which he finds unhelpful for the needs of the mixed this dual aspect epistemology with the theory of matter. Köckert (2009), 433–6, 437–8, comes extremely close to my reading by distinguishing between two aspects of creation, sub specie dei, i.e. from the perspective of the intelligible substance (ousia or phusis) of things, and sub specie silvae, i.e. from the perspective of material bodies (hulē), attributing to them, correctly, two different modes of temporality (homou and to akolouthon). But she insists that the two aspects address two different questions (p. 433). I here argue that they address the same question, namely the question of materiality. ⁸⁸ Retaining with Forbes the mathematical notion of perigraphēn (circumscription, outline, surface) instead of Drobner’s epigraphēn (inscription, name, description), which makes little sense in this context. ⁸⁹ See In Hex. 7–9 GNO 16.4–18.13 and 16 GNO 26.14–27.10. ⁹⁰ See In Hex. 16–17 GNO 27.10–29.16, esp. 17 GNO 29.1–6. ⁹¹ For the ancient debates see Sorabji (1988), chs. 1–3 (substratum theory) and ch. 4 (idealist or ‘bundle’ theory). ⁹² See e.g. GC II.1: no substratum separate from the elements, and yet there is a substratum separable from them in thought, without which we could not account for the inter-transformations of the elements. The ambiguity is solved by a dual perspective already in Aristotelian scholarship, see e.g. Lloyd (1968), 168: ‘Quality-less matter . . . is an abstraction: although logically matter can be imagined without qualities of any sort, in fact it never exists in such a form. The building-blocks from which other material objects are constructed are the four simple bodies.’ Hence the dual approach in the subsequent discussion, an extensive report of which can be found in Calcidius, In Tim. 300–20, distinguishing between two forms of reasoning: the way of analysis or abstraction (resolutio), leading to the apprehension of matter’s proper nature as the substratum of bodies, devoid of qualities (302–3, 308); and the way of synthesis (compositio), approaching bodies from an idealist perspective, i.e. from the point of view of the divine intellect and the paradigmatic forms, leading to the apprehension of matter through conceptualizations (‘mental affections’) of sensible qualities (304, 308, 335). Calcidius seems to regard this dual aspect theory as the strongest view among the Platonists (302), reaching back to Plato himself (308). He also provides the common ground of both reasonings: matter is deprived of qualities not in the sense that it can ever exist independently but in the sense that forms and qualities are not part of matter’s proper nature (310). The two approaches help illustrate matter’s peculiar status as neither corporeal (319 qua substratum) nor incorporeal (320 qua bundle of properties: silva formata qualitatibus, quantitatibus etiam figurisque). Calcidius’ conclusion that matter is ‘neither corporeal nor incorporeal but both body in potency and non-body in potency’ (320 tr. Magee) corresponds, in my view, to Gregory’s statement that the earth in Gen. 1:2a ‘was and was not’ (16 GNO 27.15–16: ēn kai ouk ēn). It is surprising that Calcidius’ report has escaped proper attention in scholarship, with the

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audience that he is addressing.⁹³ But he does suggest a starting point, namely that materiality is a compound of form (viz. qualities) and matter, and opens up two ways of unpacking the metaphysical implications. In the exegesis of Gen. 1:1 he approaches the question of materiality by way of analysis or abstraction (hekastēn tōn enuparxousōn tēi phusei idiotētōn hupexaireisthai tōi logōi), which results in the elimination of the substratum (ouden estai to hupokeimenon).⁹⁴ Conversely, in his exegesis of Gen. 1:2a, he approaches the question of materiality from the reverse perspective, as a synthesis of form (morphē) and matter (hulē), a view that presupposes matter as a substratum devoid of qualities (hupokeimenon chōris morphēs). He also stresses that God created matter (hulēn) together with the forms (tōi eidei sunapegennēse), while he conceived substance (ousian) through the forms (tōi eidei suneilēmmenēn).⁹⁵ Gregory’s audience is different, and this gives him the chance to elaborate on what was only hinted at by Basil. Following his brother, Gregory develops the idealist theory for the purposes of the exegesis of Gen. 1:1, while he elaborates on the substratum theory for the purposes of the exegesis of Gen. 1:2a. If there is a tension between the two theories, then it is

notable exception of Gronau, Genesisexegese, 113–15 (but again with no discussion of the dual approach). Alexandre (1976), 178–9, who discusses extensively the relevant part of the De silva, curiously focuses only on the ‘way of analysis’ (p. 166 n.12). To a certain degree, Calcidius is himself culpable of baffling his readers, see Reydams-Schils (2020), 135–7. Whatever is going on with the text, one should not lose focus of the main argument that analysis and synthesis are two ways of explaining one and the same subject matter: the composition of bodies as bundles of properties (303: concretio ex formis et qualitatibus; 304: hoc est genera qualitates figuras; 307: ex diversis materiis naturisque concreta). Nor should one misunderstand Calcidius’ rejection of the identification of matter with qualities (308: nequaquam placet eandem silvam esse et qualitatem) as rejection of an idealist theory of matter. All Calcidius needs to be doing here is arguing against an (e.g. Stoic) theory of corporeal qualities, reiterating, even if opaquely, standard Platonic tropes in the tradition of the Didaskalikos §§5 and 8–11, see Hoenig (2018), 208–13. Once we accept that the idealist theory is a theoretical option available at the time, silva formata qualitatibus (320) means exactly what it says: matter formed, produced, or constituted by qualities (rather than van Winden’s (1965), 166: ‘matter, provided with qualities, quantities, and figures’, or Magee’s ‘informed’). A much shorter report of the dual approach is also found in Plotinus, Enn. II.4.14.17–28 (matter as privation and matter as substratum), as the product of Peripatetic thought, see the comments of Kalligas (2014), ad loc. (p. 324). In light of this evidence, Gregory’s dual approach to the question of materiality is much less innovative than it seems. Why there has been such a big fuss about it remains to me an incomprehensible mystery. ⁹³ See Hex. I.8 GCS 14.12–15.15 and II.2–3 GCS 23.6–25.18; Zachhuber (2006). ⁹⁴ See Hex. I.8 GCS 15.3–12. The underlying idea is the following: if something (a tode ti) is a composite of eidos and hulē (see Hex. II.3 GCS 25.12–17, following the standard analysis of Aristotle e.g. in Metaph. VII.3 1029a2–7) then it is self-evident that neither of the two components can, by and of itself, be a ‘something’. Basil spells this out as regards matter: it is not-a-thing (ouden). Gregory spells out the other half of the equation: neither are qualities per se a something; they are mere thoughts and concepts (ennoiai eisi psilai kai noēmata). ⁹⁵ Tōi eidei tēn harmozousan hulēn sunapegennēse: dative of association following a verb with a sunprefix meaning ‘together with’. Autēn tēn ousian tōi eidei suneilēmmenēn: Giet, Hexaéméron, 149, translates once more as a dative of association (‘leur substance et leur forme tout ensemble’). But for the meaning ‘together with’ one would need here a syntax such as meta tou eidous or sun tōi eidei or kai to eidos. Instead, we get a dative of instrument: the substance is conceived by God through/by the form, a clear allusion to the doctrine of Metaph. VII.7–9 that the substance of a thing (and the moving cause of its coming to be) is the form, which in artistic production is found in the soul of the artisan, here God.

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already present in Basil.⁹⁶ Gregory simply tries to provide a rational explanation of how the hupokeimenon can be at the same time a nothing (ouden) and yet one of the two components of materiality (eidos and hulē). He thus comes up with the ingenious suggestion that the first two verses of Genesis describe two different approaches to the world. The idealist model approaches creation sub specie dei (tōi theiōi ophthalmōi), showing that the materialization of qualities, which per se are mere thoughts and concepts (kath’ eauta ennoiai eisi psilai kai noēmata), necessarily entails a mode of being other than God. This is because a material mode of being requires a conceptual space other than God who is immaterial (aülos).⁹⁷ The second model, which now reprises the narrative sub specie mundi, makes explicit what was previously implicit.⁹⁸ It elaborates on the conceptual space ‘in which’ creation occurs, namely the substratum (hupokeimenon), showing, however, that it is not a physical but a metaphysical enabling condition, a state of potentiality (dunamei to einai eiche). The transition from potential to actualized being (energeiai) is achieved by the concurrence of qualities, described as a process of ‘thickening’ or solidification (puknōsis). Clearly, the two models approach the question of materiality from two different but, at the time of Gregory, convergent philosophical languages, the Timaean language of space (chōra) and the Aristotelian language of potentiality (dunamei).⁹⁹ The two are combined in the ⁹⁶ It seems that the dual approach has also escaped Basilian scholarship, see e.g. the lengthy discussion of Rasmussen (2019), 101–12, with further references yet no suspicion that Basil is able to sustain both theories if argued from different methodological (analysis–synthesis) and exegetical (Gen. 1:1–Gen. 1:2a) perspectives. ⁹⁷ See 7 GNO 16.5: God kateballeto the intelligible ingredients of the material world. Kataballō means ‘lay down, deposit, put in, sow’, clearly employing a spatial metaphor. The ‘space’ that is here implied cannot be physical place or mathematical space, since interval or extension (diastema) figures among the ingredients that God kateballeto. If place and space are ruled out, kateballeto can only mean a kind of ‘conceptual space’ as a metaphor for a different mode of being, as von Balthasar (1995), 29–30 and 47–8, rightly seems to have thought (though confusingly also identified with ‘space and time’, causing a lot of objections, see Alexandre (1976), 184–5; Köckert (2009), 432). Later treatments of Gregory’s diastēma have not helped clarify that dimensionality and space–time are the mere consequences of ‘otherness’ and logically posterior to it, as Plotinus rightly remarks, see Enn. II.4.12.11–13. What Gregory here presupposes is spelled out in Enn. II.4.5.28–31: otherness as prior to (and productive of) matter. Plotinus speaks in this context of intelligible matter (while the consequences for sensible objects are discussed in Enn. II.4.16) and Gregory gives us a clue that he is indeed thinking in similar terms. The ingredients of the world are, per se, intelligible (ennoiai eisi psilai kai noēmata). ⁹⁸ Sub specie mundi, since the exegesis has now moved from Gen. 1:1 (sub specie dei) to Gen. 1:2a, starting with the unformed earth, which I take as an exemplary case of unformed matter, following the Philonic-Origenian tradition (but avoiding the blunt identification, against which Basil had protested in Hex. II.2, as too suggestive of the uncreated matter of the schools), see Gronau (1914), 115–16 n.2 and Alexandre (1976), 172–80. Risch (1999), 175 n.184, and Köckert (2009), 430, rightly protest that Gregory refers here only to the unformed state of ‘earth’ as one of the four elements and not to ‘unformed matter’. The latter view, however, overlooks the fact that the earth functions here as a case study. The discussion is about the materiality of the world, not just earth, see 16 GNO 27.7–9: the exegesis of Gen. 1:2a helps illustrate the creation of the whole universe (tēs hulikēs tou pantos kosmou katabolēs). The emergence of the element ‘earth’ (tēs geōdous poiotētos) is part of the exegesis of Gen. 1:9–10, i.e. of the third day of creation, which is the subject matter of 26 GNO 39.13–40.15. ⁹⁹ On the history of this convergence I found the comments of Runia (1986), 141–5; and Fleet (1995), 164–7, very helpful. On the exegetical and philosophical issues involved see the brilliant introductions of Perdikouri (2014), 19–27, and Kalligas (2014), 304–8.

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formula of matter as a chōrētikē dunamis.¹⁰⁰ Once the language is understood, we can better appreciate Gregory’s intentions. The dual approach to matter goes back directly to the Timaeus: an account of creation from the point of view of the Intellect (29d7–47e2), approaching the body of the cosmos as materialization of qualities or powers (31b4–32c4); and an account of the world from the point of view of Necessity (47e3–69a5), positing a substratum for the material manifestation of qualities to occur (49a6–50b5). Gregory’s two models, the idealist and the substratum, correspond to the work of the Intellect and the work of Necessity, respectively,¹⁰¹ betraying a close engagement with Timaean physics in the subtext of the Apology.¹⁰² But Gregory learns to read the Timaeus through Origen. As we saw, even a Platonist like Galen would go as far as to accept that the Demiurge shaped the materials out of which he moulded the world. But he would still think of matter as a cause. That is where Gregory uses Origen’s corrective. First, the idealist theory clearly denies the causal role of matter in creation (since matter does not exist per se). Second, the substratum theory ascribes an enabling role of matter in creation (since the materialization of qualities requires the possibility of a mode of being other than God). Gregory sides decisively with Origen against Galen, arguing that matter is not a cause but only an enabling condition of the phenomenal world.¹⁰³ The whole of creation, including matter, is the work of divine will, power, and wisdom.¹⁰⁴ That is the whole point of Gregory’s theory of matter and at least on this everybody seems to agree.¹⁰⁵

¹⁰⁰ See In Hex. 17 GNO 29.6–10: chōrētikēn tōn poiotētōn dunamin; dektikēn dunamin tōn poiotētōn (the power to receive qualities). ¹⁰¹ Another possibility would be to suggest that Gregory’s two models correspond to the two ways of thinking about the receptacle, namely as a neutral ‘stuff ’ and a space or place, reiterating an ambiguity inherent in the Timaeus itself, see Zeyl (2000), lxii–lxiv. But, as already explained, Gregory’s first theoretical construction cannot mean mathematical space or physical place. Having said that, Gregory could of course reinterpret the receptacle as ‘conceptual space’ but to do so he would need to argue top down, i.e. from the point of view of the Intellect. Hence my solution. ¹⁰² The Timaeus contains also a third part, referring to the combined work of Intellect and Necessity, which explains the formation of the human being as a psychophysical living organism (69a6–92c9). In my reading of Gregory, the Hom. opif. treats the same subject matter as the third part of the Timaeus (namely the combined work of Intellect and Necessity exemplified in the human being as a psychosomatic entity), while the Apology treats the same subject matter as the first two parts (namely the work of the Intellect and the work of Necessity). If I am right, the Apology and the Hom. opif. contain, together, Gregory’s Christianized version of the whole programme of the Timaeus. This might go some way to explain why the Apology and the Hom. opif. have been so often treated indiscriminately in the reception history. ¹⁰³ We stand here in front of a clear dialectical strategy. As Ludlow (2009) has convincingly shown, Gregory repeats a similar anti-Platonist move from within Platonism in the An. et res., once more in relation to the role of materiality, exploiting (again) the ambivalence of the Platonic corpus. Ludlow concludes that ‘the dialogue in the De anima et resurrectione is not just a dialogue between Christianity and Platonism, but it is a dialogue inserted into an ongoing conversation within Platonism between different strands of Plato's own thought’ (p. 488). I here argue for a similar position to Ludlow’s, which I trace back to Origen (see section 2.2.1 above). ¹⁰⁴ See In Hex. 7 GNO 14.13–15.8; 9 GNO 18.7–19.15. ¹⁰⁵ See Costache (2013c), 14, 17, with references.

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We are back, then, to Galen’s objection: if creation is grounded in divine omnipotence, what is the role of the material principle? Can there be a coherent notion of hexaemeral physics? We saw how Origen answered the question by denying the status of a cause to the material principle but fully integrating it as an enabling cause for the divine will, power, and wisdom to manifest. This is where Gregory picks up the thread. The whole point of the Apology is to show how divine will, power, and wisdom manifest in the world as the creative logos, God’s practical reasoning, so to speak.¹⁰⁶ It is through the logos that God separates (diakrisis) each element from an indeterminate conglomeration of properties, allowing it to manifest distinguishable, quantifiable, and regular characteristics, accountable for the appearance of sensible qualities.¹⁰⁷ And it is through the logos that God combines (sundromē) the qualities in such proportion and measure as to allow particular beings to emerge.¹⁰⁸ Phenomenal being is actualized being; actualized being is individuated being; and individuated being is qualified being, i.e. a tode ti emerging, gradually, out of an initial panspermia of indeterminate properties according to an innate logos. It is this logos that bestows order, causality, and regularity to the natural phenomena. Conversely, it is the study of the regular, causal, and structured patterns of nature that reveals the presence of an egkeimenos (i.e. innate) logos at work.¹⁰⁹ That seems to be the result of Gregory’s contemplation of nature. If I am right, the story of creation is, for Gregory, the story of the self-disclosure of the logos. Scripture and nature become the receptacle of the logos in its dual aspect, as speech and as reason.¹¹⁰ Hence the fusion of physics with hermeneutics in the Apology—a purely Origenian insight: it is the same heirmos, akolouthia, and ¹⁰⁶ See In Hex. 10 GNO 20.17–21.6 and 11 GNO 22.5: everything was created according to the logos of God’s wisdom (kata ton tēs sophias logon; pan to ginomenon logōi ginetai); creation manifests God’s wisdom as logos (hē en tēi ktisei theōroumenē sophia logos esti). Gregory describes creation with the help of a craft analogy, see 10 GNO 21.15 (technikēs theōrias). Hence, God’s creative logos reveals the skill of the divine craftsman to give material shape to his thought, see e.g. 10 GNO 21.5–6 (logon tina sophon kai technikon). Gregory also uses the biological analogy of the seed (spermatikē dunamis 16 GNO 26.13–14), which is another popular image of the creative power of the logos inherent in nature, see Köckert (2009), 461–81, and Köckert (2010), 27–32. On the role of the logos in Gregory’s doctrine of creation see Mateo-Seco (2010), esp. 184; Costache (2013c), 21–2. ¹⁰⁷ On the Apology as a form of the so-called ‘diakrisis-cosmogony’, see Spoerri (1959), 76–7; Risch (1999), 34–6; Köckert (2009), 461–5. That the separation (diakrisis) of elements is the particular work of the logos is exemplified in the case of light, see §§10, 12, 72, and 74. ¹⁰⁸ Gregory describes the emergence of the phenomenal world of change as a continuous process of combination and separation of elements, see In Hex. 53 GNO 63.18–64.2: panta en allēlois esti kai di’ allēlōn diakekritai. On the combination of qualities according to the logos of each thing compare the two passages on materiality, 7 GNO 16.4–11 (sundramonta pros allēla) and 17 GNO 29.1–6 (kata ton logon). On sundromē see the detailed comments of Risch (1999), 124–5 n.84 and 133–6 n.97. ¹⁰⁹ See In Hex. 10 GNO 21.5–6: chrē hekastōi tōn ontōn kai logon tina sophon kai technikon egkeisthai pisteuein; 11 GNO 21.8–9, 26 GNO 40.7: ton egkeimenon [tēs phuseōs] tēi ktisei logon. ¹¹⁰ See In Hex. 10–11 GNO 20.71–22.14: the works of God’s creative logos (ho kata ton tēs sophias logon egeneto) are described by Moses as words of divine commandment (hōs logos theou prostaktikos emnēmoneuthē). They are the divine fiats of the creation narrative (ta prostaktika tēs tōn ontōn ktiseōs rhēmata). Hence, the works of creation are the words of creation (to ergon logos esti) revealing the logos at work in creation (pan to ginomenon logōi ginetai).

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taxis that disclose the indwelling logos of the world, whether in the literary world of Scripture or the physical world of nature. The contemplation of the emergent logos becomes the deeper insight driving Gregory’s work, the real skopos of the Apology. It is here, at the level of the logos, both cosmic and literary, that Gregory defends Basil’s hexaemeral project. The vision of creation as the manifestation of the creative logos, of God’s practical wisdom revealing itself through the works that it creates, allows Gregory to answer Basil’s critics and defend, at the same time, Basil’s affiliation with the Origenian agenda.¹¹¹ The detractors were not able to see past the method and grasp the deeper unity and continuity in Origen’s and Basil’s hexaemeral exegesis: the world as a theophany; creation as contemplation of the divine logos at work.¹¹² Gregory’s defence is beautiful but has the major disadvantage of being elusive, due to the nature of the vision that it aims to capture. It is the vision of a paradoxical logos, divine and yet in the world, always

¹¹¹ See Basil, Hex. I.7 GCS 12.6–13.11 (craft analogy): God as technitēs, the world as a technikon kataskeuasma, bearing in it the technikos logos of the divine craftsman. I.8 GCS 15.3–12 (a contrario): the rational investigation (tois logismois, tōi logōi) into individual substances (tēn ousian) leads to the logos of their nature (tōi tēs phuseōs logōi) and the accidental qualities that complement it (sumplērōtika tēs ousias, enuparchousōn poiotētōn). II.2 GCS 23.6–25.8: corrective to the craft analogy, which, if understood anthropomorphically, leads to the erroneous postulation of an uncreated matter. Instead, God created both matter and form and shaped the elements of the world as was required by their individual logos (hōs ho hekastou logos apēitei); God then bound together all the different (anomoiomerē) parts of the world into a harmonious whole through a friendly bond (philias thesmōi). This is, as Callahan (1958), 46, rightly perceived, a clear allusion to the composition of the world’s body according to Tim. 31b4–32c4. There we learn that the harmonious bond (desmos) of the world is a logos in the mathematical sense of (geometric) proportionality (analogia). III.2 GCS 40.7–41.6: the divine fiats reveal the creative intent (boulēma) and innate propensity (hormē) of God to be the divine logos (logos tou theou). The creative activity of God is a purely intelligible motion (noerou kinēmatos) communicated to the logos as the co-author of creation (sunergou), in a purely intelligible fashion (tou noēmatos koinōnein; tōn en kardia noēmatōn hē metadosis). III.10 GCS 55.7–20 (continuation of the craft analogy): in the eyes of God (ophthalmois theou), the goodness of creation is measured by the logos of the creative art (tōi logōi tēs technēs). God moulded together the individual parts of the world through his creative logoi (tois technikois heautou logois), like a skilled artist (technitēs). V.4 GCS 74.22: every created being realizes a particular logos (idion tina logon) in creation. V.2 GCS 70.20–71.21: the species (genos) of plants is in their seed (sperma) or their innate seminal power (spermatikēn dunamin). VII.2 GCS 114.4–7 (seminal causes): the biological image of the seed applied by analogy to animal species (hoionei spermata tina tēs phuseōs); etc. Compare now Origen’s Hom. Gen. I.1: The in principio of Gen. 1:1 means that God made heaven and earth in verbo suo, i.e. in the logos of John 1:1. See also my references above (section 2.2.1) on the role of divine wisdom and logos in Origen’s doctrine of creation. The deeper point of the Apology is to show that the doctrine of the logos is the crucial link between the Origenian and the Basilian hexaemeral exegesis. Once the continuity of the logos doctrine is established, all differences in hermeneutical method and details are revealed for what they are, namely exegetical variations on the same theme: creation as the topos of incarnation, i.e. self-manifestation, of the divine logos. The assumption is of course that Origen and Basil share the same doctrine of the logos. The proof for that can be found in the Christological conclusions of Basil’s final homily, referring to the Son in the characteristically Origenian (and originally Philonian) language of the logos as the image (eikōn) of the Father, see Opif. 25; Fug. 101; DP I.2; cf. Hex. IX.6. It is exactly at this point that Gregory picks up the thread of the hexaemeral narrative from Basil, first to complete the work of the logos with the creation of humankind (Hom. opif.) and then to clarify further its cosmic significance (Apology). ¹¹² For a recent defence of the deeper unity of the Cappadocian contemplation of creation see Blowers (2016). If we deny the exegetical continuity it is impossible to grasp the unity of the Cappadocian vision. However, that would be a methodological mistake, see Anatolios (2007).

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hidden and yet always present, showing itself in the reflection of the works that it creates.¹¹³ It is the mystery of this logos that Moses sets out to narrate, not by saying the unsayable—an impossible task—but by following its trace in the taxis and akolouthia of the world.¹¹⁴ It is this akolouthia that the creation narrative retells in six episodes, the ‘six days’. Moses disguises in narrative form the key to nature’s deepest secret, to the hidden logos of things, turning physics into hermeneutics. Akolouthia and hexaemeron thus become terms co-extensive in meaning: they both tell the story of the universe as the unfolding of the logos, creation as the divine workshop, the world as revelation of the divine craftsman’s ineffable skill. The first act of the revelation of the logos is also the first speech act of creation: ‘let there be light’.¹¹⁵

2.3 Enter Light 2.3.1 A Look behind the Scenes: The Hexaemeral Theory of Change There is a certain Heraclitean flair in Gregory’s doctrine of the egkeimenos logos that loves to hide. Consider the first divine fiat: God said ‘Let there be light’ and there was light. No matter how many times we read the verse, we are merely spectators of the end product, the outcome of God’s creative activity. There is nothing in the text about the creative process itself, nothing about the preparatory work that the craftsman has to do in order to bring light into existence. The workshop of creation, the divine mind where all the planning and shaping of the world is done, remains forever hidden behind the lines of the creation narrative. To reprise a celebrated metaphor: if creation is a cosmic drama, we only get to see what moves on stage. If we want to learn how everything was prepared, however, we have to lift the curtain and take a look behind the scenes. In identifying the logos of nature with the logos of Scripture, Gregory cannot be more explicit: The hexaemeral logos is of a Heraclitean breed. To those who fail to grasp the message, Gregory sends the signal out twice. The Apology begins with Moses leaving the crowd behind, entering the cloud of knowledge alone, and ends with Paul leaving the sensible world behind, entering the third heaven. Both images use mystical language, inviting Peter, together with the able reader, to follow Moses and Paul,

¹¹³ See In Hex. 7 GNO 22.15–23.17: kata ton arrēton tēs dunameōs logon. Notice the paradox: arrētos logos denotes both ‘unspeakable speech’ and ‘irrational ratio’, thus surpassing all human understanding (pasan ennoian pariōn anthrōpinēn). ¹¹⁴ See In Hex. 71 GNO 77.14–19. ¹¹⁵ See In Hex. 10 GNO 20.17–21.1: fiat lux as the first double manifestation of the logos as divine wisdom and divine commandment.

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lift the veil of phenomenality, and take a look at the adytum.¹¹⁶ It is there, behind the scenes, that the immanent logos of things abides. And it is the task of the hexaemeral exegete to retrieve this logos from the subtext of the creation narrative in order to provide a rational account of the phenomenal world, the realm of change. The rational enquiry into the realm of change is precisely the task of ancient physics. Contemplation of Scripture, then, leads to contemplation of the phenomenal world. ‘Genesis’ means precisely that: generation, becoming. In defending the role of the material principle, Gregory reinstalls the world of Heraclitean flux, and all its challenges, back onto the centre stage of the hexaemeral discussion. The enquiry into the nature of light is an integral part of the broader enquiry into the nature of change. The physics of light is no disconnected part of the rest of the physical world. That means that the physics of light is an intrinsic part of the mechanics of nature, of the technikos logos of the world. Contrary to contemporary physics, which has not yet achieved a unified theory of everything, the physics of light of the Apology is but one aspect of a comprehensive theory of change, or of how things come to be and pass away. The Apology reduces all explanations of change to the theory of the four elements (fire, air, water, and earth) and their mutual inter-transformations. The outlines of the theory are Aristotelian: each element consists of a pair of two opposite but not contrary sensible qualities (hot and cold, dry and wet), which Gregory already accounted for in his theory of matter. Fire is hot and dry, air is hot and wet, water is cold and wet, and earth is cold and dry. Gregory, following Aristotle, allows changes to take place between all four elements by an exchange of qualities. Water (more generally: liquid) becomes air (more generally: gas) under the effect of external heat (e.g. of the sun) by a substitution of hot for cold. Similarly, air becomes fire by a second transmutation of cold into dry etc.¹¹⁷ ¹¹⁶ See 5 GNO 11.5–6: eis ton gnophon tēs tōn aporrētōn theōrias; 75 GNO 81.3–4: kathaper en adutois tisi tēi sophiai genomenos tōn arrētōn epēkroasato; 76 GNO 83.1–2: en tois adutois tēs noētēs genommenon phuseōs. ¹¹⁷ The key passages are §§ 29, 41, 55–6, and 62, with §§29 and 59 clearly showing that Gregory elaborates on the standard Aristotelian theory of the elements as we know it from the GC II.2–4. Risch, Sechstagewerk, 216–17 n.328, argues that Gregory distances himself from the Aristotelian doctrine in various respects, e.g. in adding quantity (pēlikotēs; posotēs) and weight (baros) to the essential characteristics of the elements (§§41 and 55). I do not think there is deviation here. The point of Aristotle’s theory is not to deny the rest of the sensible qualities, but to give a parsimonious account of them. He thus reduces all sensible qualities to pairs of contraries, like hard and soft, rough and smooth, heavy and light, etc., and then reduces these contraries to two pairs: hot and cold, dry and wet, see Lloyd (1968), 167. Thus, in §55 the light (kouphon) is an attribute of fire and air while the heavy (baru) is an attribute of earth and water. This is a faithful application of Aristotle’s doctrine in Cael. I.3 and IV.1–5 (cf. also GC II.3), which classifies the elements from the lightest (fire) to the heaviest (earth). Gregory may be further suggesting that this attribution is due to the elements’ defining characteristics, which explains why he connects the wet, the cold, and the dry with heaviness in §41. But that would be a clarification of the original Aristotelian doctrine of Cael. IV.4–5, probably necessary in view of Stoic developments (see e.g. Philo, Heres 134–5, 146), and certainly no deviation. Again, in §41 Gregory clearly states that quantity and weight are not the differentiae of the elements, but what survives the transmutation. Quantity and weight denote here the surviving material substance (cf. §39 ho de kata tēn hulē ogkos; §40 to hulikon), which they always accompany. This, in turn, corresponds to Aristotle’s

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Gregory uses this theory to explain all natural phenomena in the universe, from the hydrological cycle to meteorological and astronomical phenomena. This comprehensive explanation is a divergence from Aristotle, who limited the use of the four elements to the sublunary, arguing that a different substance is active in the supralunary—a doctrine refuted by hexaemeral authors due to the religious overtones of the celebrated ‘fifth element’.¹¹⁸ For Gregory, aether is not a new element but just a finer form of warm air extending beyond the atmosphere towards the vast regions of outer space. It is vital for the nourishment and sustainability of the celestial fire of the stars.¹¹⁹ The aim of the hexaemeral theory material substratum, according to GC I.6 and II.1. One could argue that the idea of a surviving material characterized only by weight and quantity is an early anticipation of the modern concept of ‘mass’. But that is, once more, not a deviation from the original Aristotelian theory, but a brilliant interpretation of Aristotle’s principle of mass conservation in Phys. IV.9, 217a26–31 (see also Meteor. II.2 and 3 for the hydrological cycle). Plotinus, on the other hand, seems to regard lightness as an essential property of fire together with heat and brightness, see Enn. II.6.2.11–13. ¹¹⁸ On Aristotle’s ‘primary element’ or ‘first body’ (prōto stoicheion, Meteor. 339b16–30; prōton tōn sōmatōn, prōtē ousia, Cael. 270b1–25), the ‘fifth element’ or ‘heavenly body’ of the tradition (apud Alexander apud Simplicius, In Cael. 436.4–6), see Moraux (1963). On the role and place of the fifth element in Aristotelian physics see Lloyd (1968), 134–9. It was passages like Cael. 269a31, 270b5–25, 284a2–17, and Metaph. 1074a38–b14, endorsing popular religious ideas about the divinity of the heavenly substance, that prohibited the hexaemeral authors from accepting Aristotle’s fifth element, see Origen DP III.6.6, CC IV.56; Basil, Hex. I.11, III.3 (dialectical refutation of the Peripatetic doctrine), and II.6 (identifying heaven with fire); Ambrose, Exam. I.6.2–4 (detailed refutation of the Peripatetic doctrine); Gregory, In Hex. 18 GNO 30.5–8 (explicit refutation of the existence of another—viz. fifth— element), see further the monumental study of Pépin (1964), esp. 151–72 (on the divinity of the fifth element) and 103–25 (on the Epicurean background to Ambrose’s refutation). ¹¹⁹ The key passages on the nature of aether are §§36–7 and 48. On the theory of exhalations see §§34–5, the consequence of which is the nourishing of celestial fire, see §§ 46 GNO 59.11–12; 47 GNO 60.9–11; 53 GNO 64.11–13. The precise role and function of aether in the sources is problematic, simply because every late antique school had a concept of ‘aether’ in its cosmology, see Waszink (1950). As already explained, Gregory rules out the Peripatetic notion of aether as the fifth element. Since Gregory distinguishes between the denser air of the sublunary and the subtler aether (§§36, 44, 75), while he adheres to a system of four elements (§§29, 31), we can safely infer that aether denotes the fine stuff that fills outer space, i.e. the supralunary, Gregory’s biblical ‘firmament’ (§18) and Paul’s ‘second heaven’ (§75–6), which hosts the celestial fire of the stars (46 GNO 59.11 en tōi phlogōdei; 47 GNO 60.9–10 ton huperkeimenon kai phlogōdē chōron) that revolve in it (18 GNO 30.8–9 to akron tēs aisthētēs ousias hoper hē tou puros phusis peripolei; 75 GNO 82.5–8 to meta tēn aplanē sphairan peri to entos theōroumenon en hōi oi planētai tōn asterōn diaporeuontai). Gregory thus distinguishes between three things: the outer space (= the supralunary); its stuff (= aether); the heavenly bodies that revolve in it (= the planets and stars). Since the heavenly bodies are made of fire (see Chapter 3), Gregory seems to rule out the notion of aether as celestial fire, an ancient use attributed by Aristotle to Anaxagoras (Cael. 270b24–5; Meteor. 339b20–5, 369b14–15) and made popular by the Stoics, see Lapidge (1973), 254–9; and Long/Sedley 46–7 with comments ad loc. That brings Gregory closer to the mainstream use of aether as ‘fiery upper air’ in archaic and classical Athens, see Mihai (2010) and (2015), 104–13. We find this use in the Phaedo (109b–c, 111a–b) and the Timaeus (58d), where aether denotes the purest form of air, but also in the Epinomis (984b–c, e), which situates aether between air and fire. It is precisely this finest form of warm, fiery air extending in the supralunary that Gregory has in mind when he speaks of aether in the Apology. In that sense, aether can be called a fiery substance, see 48 GNO 61.21–62.2 (aitherion eidos . . . puros phusis), just as elsewhere it can be called luminous (phōtoeidēs) due to its pure (tōi katharōi), in the sense of transparent (diafainetai), nature suffused with light (aktinōn empiplatai kai phōs ginetai), see Virg. XI.4 GNO 294.24–295.13. Gregory clearly takes this use from Basil, see Hex. II.7 GCS 32.7–18 (phusis leptē kai diafanēs), III.7 GCS 49.14–50.14 (aithera purōdē kai diakaē). Other hexaemeral authors understood aether rather in the Anaxagorean-Stoic sense of pure, celestial fire. This is clearly the case when Origen identifies aether with light in the context of his doctrine of the ‘spiritual

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of the four elements is to address the fundamental challenge of ancient physics, namely how to account for the mixture of identity and flux that characterizes all sensible phenomena. Gregory’s answer is not innovative: identity is due to the innate qualities of elements; change is due to their inter-transformations. What, then, is nature (phusis)? The Creator who made the earth’s elements did not endow any one of them with constancy and permanence. That is, all things are subject to change and the power of change is maintained through other things by means of a certain type of revolution where everything reverts to some earthly element and they return into themselves from other elements. This change (alloiōseōs) is unceasing among the elements and by necessity they pass into other things, undergo alteration and once again change into other things, for not one of them retains its own identity unless it mixes with another durable substance. How, you ask, does change come about through the four changeable elements which go around in a circular course? For all things do not change to all things nor does the cycle of change (ho tēs alloiōseōs kuklos) proceed in the same manner through all beings; rather, water flows into air in the form of exhalations and after the exhalations have nourished fire they turn into earth, like some kind of residue after it has been burnt. After the earth has received them the cycle of change (ton tēs alloiōseōs dromon) comes to a halt. It remains to be seen whether the nature of water has its origins from the earth, and we must consider if earth can change its nature into water . . . If it has been shown that cold is a complementary quality of water next to moisture, it follows that, since the quality of cold is innate also in earth, the water is potentially in earth and the earth in water . . . (In Hex. 53–4 GNO 63.18–64.18 and 56 GNO 66.16–20 tr. McCambly, modified)

Gregory sees the theory of the four elements contained in nuce in the opening verse of Genesis: ‘heaven’ and ‘earth’ denote the fundamental contrariety of sensible qualities (ta men akra) and thus the extreme limits of materiality. The

body’, see DP I.4.1, II.3.7, II.4.3, III.6.4. But cf. CC III.42, where Origen speaks of ‘aether and the realms above it’ rather in the sense of the Epinomis. It seems to me that the latter is also the meaning of aether in Philo, Opif. 70, but also Plant. 14, 18, 21–2, for which Colson rightly translates ‘upper air’. But cf. Plant. 3, which understands aether in the Stoic version of pure celestial fire, and Deus 78, which identifies the pure flame of the sun with aether in the traditional Stoic way. The use is therefore ambivalent, see Dillon (1983), 198–9, unless celestial fire is just compressed masses of aether, see Philo, Deus 78: hēlios . . . pilēma aitherion; Plutarch, Facie (928c = SVF II.668): tou aitheros to men augoeides kai lepton hupo manotētos ouranon gegonenai, to de puknōthen kai suneilēthen astra; ps.-Justin, Ad gentiles 172c: ho hēlios pilēma, aitheroeides tēi ousiai, lampros tōi eidei. If that is the case, there is no real deviation between the Philonic-Origenian language of ‘aether’ and the Cappadocian language of ‘pure fire’ as regards the composition of the heavenly bodies.

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extremes also imply their middle terms (ta de mesa).¹²⁰ As it stands, Gregory’s doctrine is obscure. It becomes transparent once we compare it with the Timaean theory of the extreme and middle terms of which the world’s body is constituted (Tim. 31b4–32c4). The comparison helps us perceive that, in Gregory’s reading, the scriptural ‘heaven’ and ‘earth’ correspond to the Timaean fundamental duality of phenomenal properties: visibility and tangibility. The latter properties presuppose, in turn, two primary but contrary elements: fire, which illuminates everything due to its mobility and subtlety (Tim. 58b); and earth, which manifests solidity, being the most immobile and pliable body (Tim. 55e). The middle terms required for the bonding of the contraries correspond to the other two basic but derivative elements, air and water, manifesting median subtlety and solidity (Tim. 56a–b, 58b). Thus, Gen. 1:1 entails, in Gregory’s adaptation of Timaean physics, the existence of the four elements in their potential state, together with their cycle of inter-transformations. And since corporeal beings are composites of the four elemental bodies, Gen. 1:1 also entails the existence of all corporeal beings— potentially. Thus, the whole creation narrative becomes a disquisition of how Gen. 1:1 unfolds in time, in exactly the same way that all corporeal beings can be derived through a series of inferences from the cycle of the four elements. The akolouthia of Scripture entails the akolouthia of nature. The beginning of the creation narrative establishes then the following preliminary point for us to grasp, namely that God laid down all at once (sullēbdēn en akarei katebaleto) the constituents (aphormas) of all things, the causes (aitias) and the powers (dunameis), and by the first impulse of his will the substance of each being, such as heaven, aether, the stars, fire, air, sea, land, animals and plants, came together (sunedramen). God beholds them all by reason of his power; as the prophet says, ‘He saw all things before they came into being’ [Dan. 13.42]. By his power and will each and every part of the cosmos achieves its end, following a certain determined chain of events (heirmos tis anagkaios) and order (kata tina taxin) so that a particular substance (tode ti) [namely fire] first appeared preceding all things that can be seen in the universe, and in the same way appeared that which comes by necessity after the first, and then the third, as the designing nature (technikē phusis) foreordained, then the fourth and the fifth and so on in order of sequence (tēs kata to ephexēs akolouthias). Not by a spontaneous circumstance (ouk automatōi tini suntuchiai), appearing randomly and without order, but following a sequential pattern (to akolouthon) as the necessary order of nature requires of everything that partakes in becoming. That is how Moses said that everything was made, expounding in narrative form the

¹²⁰ See In Hex. 9 GNO 18.3–6; 16 GNO 26.16–27.8. This doctrine is already announced in Hom. opif. I.2 and I.5, as a recapitulation of Basil’s doctrine. Basil indeed makes this exegetical move in Hex. I.7.

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   - doctrines of natural philosophy (en diēgēseōs eidei peri tōn phusikōn dogmatōn philosophēsas), foretelling how each thing came to be according to certain divine commands. (In Hex. 9 GNO 18.7–19.10 tr. McCambly, modified)

As the sequence of events flowing from Gen. 1:1 unfolds, we find the four elements in an initial state of total blending, with their powers neutralized by each other’s contrary qualities.¹²¹ In order to pass from potentiality to actuality, the elements need to be separated from each other. The separation (diakrisis or apokrisis) allows them to exhibit their intrinsic characteristics and occupy their natural place in the universe.¹²² Separation then provides a first rational model for the explanation of change. As the initial state of total blending disappears, qualified being emerges. Thus, the mechanics of separation reveal the logos at work shaping the world.¹²³ Moses depicted the work of the innate logos through the rather anthropomorphic narrative of days and divine commands. This narrative must be understood in a higher sense (theoprepōs).¹²⁴ The work of the first three days denotes simply the actualization of the four elements in descending order of succession, from the most agile and subtle to the most heavy and solid: fire on day one, followed by air, water, and earth on days two and three. ‘Let there be light’ is then nothing more than the narrative expression of the first manifestation of the logos in nature. The transition of the fiery element from a state of potentiality to a state of actuality becomes the first manifestation of qualified being.¹²⁵

2.3.2 A (Meta-)Physics of Power Causality: The Consubstantiality of Fire and Light The question then is: how does the separation of fire from the rest of the elements take place? Gregory’s answer picks up on a difficulty in Aristotle’s theory of the elements. It is helpful here to recall that according to the considered view of the Timaeus, the capacity of the elements to transform into each other is limited to three (fire, air, and water), while earth is excluded entirely from the cycle

¹²¹ See In Hex. 7 GNO 15.19–16.11; 9 GNO 18.7–13; 16–17 GNO 27.10–29.6. ¹²² See In Hex. 10 GNO 10.10–17: adiakritōs; 12 GNO 22.15–18: hē phōtistikē dunamis heautēn tōn heterophuōn apokrinasa; 19 GNO 31.19: hē de tōn hudatōn diakrisis; 25 GNO 37.17–18: tē photistikēs te kai purōdous ousias tais idiais poiotēsi tōn allōn apokritheisēs; 26 GNO 39 14–15: hē to hudōr tēs gēs apokrinousa theou phonē; 40.10–12: to apokrithen tēs hugrotētos. ¹²³ See In Hex. 10 GNO 20.17–21.6. ¹²⁴ See In Hex. 9 GNO 19.5–15; 26 GNO 39.14–15, 40.3–8. So, too, for the Psalmist: 11 GNO 22.11–14. Theoprepōs literally means ‘in a sense worthy of God’ or ‘befitting God’. Its opposite is anthrōpopathōs. As Sheridan (2015), esp. 27–44, has shown, theoprepōs is an Origenian trope introducing the higher sense of Scripture against anthropomorphic interpretations. In the Apology it signals the passage from the phenomenal aspect to the causal structure of creation. ¹²⁵ See In Hex. 9 GNO 18.13–19.5; 65 GNO 72.16–73.1; 72 GNO 78.1–22.

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of transmutations (Tim. 54c–d).¹²⁶ Aristotle is quite critical of this exception, claiming that it contradicts observation (Cael. 306a1–7), and he explicitly mentions the production of fire from earth (GC II.4 331a33–331b23). And yet Aristotle does not provide any practical examples of how this generation of fire from earth can be observed. For a useful insight we have to look elsewhere. We get an interesting lead from Theophrastus, Aristotle’s student and collaborator, who, in the special treatise De igne, gives us two examples for the production of fire from earthy materials: the striking of stones and the rubbing of sticks (De igne 1.4–7). These examples will become classical in subsequent literature.¹²⁷ Cicero will use them to illustrate how fire permeates everything, including the earth (DND II.9.25). We find the same examples widespread in the context of the hexaemeral elemental theory in its Basilian inspiration.¹²⁸ Gregory has precisely this context and these examples in mind in his explanation of the generation of fire from the initial state of total blending,¹²⁹ Scripture’s ‘invisible and unformed earth’ (Gen. 1:2a).¹³⁰ The examples aim to show the generation of fire by friction and hence by force. The implicit suggestion is that some kind of violent motion in the initial chaotic state of the precosmic materials caused friction which, in turn, kindled the primordial fire.¹³¹ Being of an agile and swift nature, fire separated itself immediately from the other elements, illuminating the all. That leads to the first fundamental tenet of Gregory’s physics of light: light is the innate capacity or power of fire to illuminate. Conversely, fire owes its power of illumination to its inherent logos. The exact structure of that logos, however, is elusive. When the world was made and before each of its parts appeared, darkness covered everything; fire’s sparkle (tou puros hē augē) lay hidden within matter and did not yet come forth. The situation was comparable to small pebbles which ¹²⁶ In 49b–c the Timaeus seems to extend the possibility of inter-transformation to all four elements, including the earth. But Plato qualifies this opinion twice: hōs dokoumen (49b8); hōs phainetai (49c7). His considered opinion is given in 54c–d, which excludes the earth from the cycle of transformations. ¹²⁷ See further Pliny, Nat. Hist. II.239; Porphyry, Gaur. XVII.4 Kalbfleisch 59.11. ¹²⁸ See Basil, Hex. I.7 GNO 13.15–20; Ambrose, Exam. II.3.12; Severian, Cosmog. I.5 PG 65:435. ¹²⁹ See In Hex. 10 GNO 20.4–8 (text cited below). ¹³⁰ See In Hex. 10 GNO 20.8–13 and 17 GNO 28.12–29.6. This is Gregory’s interpretation of the Hebrew tohu wa–bohu, equivalent to a chaotic state of primordial qualities, see Gronau (1914), 116; Spoerri (1959), 76–7; Risch (1999), 154 n.134. ¹³¹ The force that set the akolouthia of nature in motion is the divine logos or command (10 GNO 20.14–21.6), which manifests God’s creative wisdom, power, and will (11 GNO 22.5–6, 11–12; 7 GNO 14.17–19, 15.3–4). The idea of the separation of the elements by friction goes a long way back into ancient Greek cosmogony, see the still helpful study of Spoerri (1959). Gregory, here, is clearly developing a biblical version of Tim. 52d–53b. His own contribution is to show that the will of the Demiurge is the cause of the agitation of the receptacle (i.e. the ‘earth’ of Gen. 1:2a) that leads to the separation of the elements. This shows that Gregory writes the Apology with the Bible and the Timaeus both on his desk. A mere secondary knowledge of Timaean physics through doxographic material or an epitomē cannot explain that level of reflection. Gregory must have studied closely the Timaean physics, which he skilfully combines with a close reading of Aristotle’s De caelo, Meteorologica, and De generatione et corruptione, as we have seen. Passages like Tim. 53a1–2 allow him the combination. Moreover, that level of sophisticated analysis requires access to the commentary tradition, for which see Baltes (1976–8).

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are concealed in the gloom, though they have in them the power to illuminate (en heautais tēn phōtistikēn echousi dunamin) by producing fire when they strike one another; but when the spark (spinthēros) that comes from them blazes up (anaphanentos) they too appear due to its glow (tēi lampēdoni). Thus, everything was invisible and imperceptible before the illuminating substance (phōtistikēn ousian) was revealed. For, since everything came into being at once by a single movement of the divine will, each element was compounded with others and fire was clouded in darkness, hidden under an abundance of matter. But because its power (dunamis) is both sharp (oxeia) and agile (eukinētos), the moment God gave the signal to nature (tēi fusei tōn ontōn) to give birth to the world, fire leaped out before the other elements, which were heavier (pasēs tēs baruteras phuseōs proexethore), and immediately everything was surrounded by light. ... The illuminating power (hē phōtistikē dunamis) assumed first place and was set apart (apekrithē) from the other elements (tōn ontōn) by reason of its swift (tachei) and agile (eukineitōi) nature, separating itself from the rest (heterophuōn). And all that was lit around (to perilamphthen hapan) was filled with light (katephōtisthei) by its radiant power (dia tēs apaugastikēs autou dunameōs). God alone can say what is the logos through which (hōi de logōi) the fiery substance acts this way, God who has endowed nature with the logos of light (ton phōtistikon logon). And the great Moses in his own writing bears witness to this when he says, ‘And God said, “Let there be light.” ’ In my opinion the passage teaches that the work of light (to tou phōtos ergon) is a divine logos (theios logos), exceeding all human understanding. We may only consider the outcome (to ginomenon) and acknowledge the marvel through our senses. But what is the abode from which fire is suddenly generated, whether it springs forth through the striking of stones or through the friction of any other material with itself, and what is the power (dunamis) that consumes everything that fire encompasses, while it illuminates the air by its flame, all this we can neither know nor anyhow understand. The only thing we can say is that the account (logos) of this strange marvel is reserved for God, who made through the ineffable logos of his power (kata ton arrēton tēs dunameōs logon) the light to be born from fire and together with fire (eggenēthēnai) as Moses testifies in his own account (logōi), ‘And God said, “Let there be light and there was light,” and God saw that it was good’ [Gen. 1.3–4]. (In Hex. 10 GNO 20.1–17 and 12 GNO 22.15–23.13 tr. McCambly, modified)

The passage invites several comments. The first comment has to do with the intrinsic link of fire and light. Gregory uses the terms relationally, if not reciprocally: light is the ‘illuminating’ (phōtistikēn) or ‘radiant power’ (apaugastikēn

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dunamēn) of fire. Conversely, fire is the ‘illuminating substance’ (phōtistikē ousia).¹³² Gregory understands the relationality of light and fire in an ontological sense: the existence of fire entails the existence of light. The first work of creation is not the release of fire’s power, namely light, into the universe, as if fire can and cannot illuminate upon God’s command. If it were so, it would be paying full justice to Galen’s and Porphyry’s critique of the (allegedly Jewish-Christian) notion of an unqualified divine omnipotence that activates and deactivates the laws of nature ad lib. By contrast, Gregory stresses that the first work of creation is, precisely, the activation of the whole apparatus of universal mechanical causation in an instant. It is the separation of the lightest and most mobile substance from the rest that allows fire to take shape and automatically release its luminous power, which was previously blocked. Fire does nothing extra or special in order to bring out the power of light. As long as there is fire, there is light too, ‘necessarily’ and ‘automatically’. Light is thus construed as a logically necessary property of fire: the existence of fire always entails the existence of light and the existence of light always entails the existence of fire, so that one cannot have the one without the other (‘ontological entailment’). The basic features of the rule of entailment are convertibility and simultaneity.¹³³ The rule of entailment means that in Gregory’s physical universe it is impossible to have fire without light or light without fire.¹³⁴ Secondly, fire entails light (and light, fire) not only ontologically but also cognitively and terminologically.¹³⁵ Gregory sees no problem in speaking interchangeably of fire and light, as when he says that ‘the illuminating power (hē phōtistikē dunamis) assumed first place and was set apart from the other elements’. What we would have expected Gregory to say is that the illuminating substance (i.e. fire), not its power (i.e. light), assumed first place, since the talk is about the four elements. Clearly, the power of illumination also implies the

¹³² I here translate ousia as ‘substance’, without specifying whether it means a particular entity (a ‘this’ or tode ti) or a natural kind (a ‘such-and-such’ or eidos). At the end of Chapter 3 I will suggest that it could mean both, depending on the context. If so, the terminological ambiguity is intended, and it should be kept in mind from now onwards. ¹³³ Convertibility: if there is X there is also Y, and if there is Y there is also X. Simultaneity: if there is X there is also Y at the same time, and if there is Y there is also X at the same time, see Radde-Gallwitz (2009), 160–1, 162–9, and 200–7; DelCogliano (2010), 219 and 224–34. ¹³⁴ See C.Eun. III.6.50–1 and Letter 35 (= Basil(?) Letter 38.7.11–23). To the possible objection that the rule of entailment breaks down in the precosmic state of affairs, so that there was a time (better: state of affairs) in which fire did not shine its light, Gregory is not left defenceless: first, he can retort that fire always has the capacity to give light, even though it cannot manifest this capacity in the state of total mixture; second, he can explain that the reason why this capacity is not activated is because fire does not yet share in qualified being but is in a state comparable to the precosmic ‘traces’ of the primary bodies in Tim. 53a2–b5. The potential state of fire’s existence is precisely the point of Gregory’s example of small pebbles that conceal in them the power of illumination, see In Hex. 10 GNO 20.3–8. The rule of entailment remains unbroken: if there is potentially fire, there is also potentially light (and vice versa). The point becomes important in a theological context, see C.Eun. III.6.50–3. The passage implies that Eunomius directly or indirectly raised the aforementioned objection. ¹³⁵ See on the relation of ontological to terminological and cognitive entailment the excellent discussion of DelCogliano (2010), 234–53.

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presence of the agent of illumination. The cognitive-terminological entailment allows Gregory to speak of fire and light synecdochically, substituting the substance with its power. The use of synecdoche becomes particularly noticeable in the exegesis of day four (§§64–73). Here, Gregory speaks of ‘light’ (phōs), of ‘the illuminating power’ (hē phōtistikē dunamis), and of ‘the illuminating substance’ (hē phōtistikē ousia) to denote, interchangeably, the light of the stars or their fiery substance.¹³⁶ The substitution of ‘light’ for ‘fire’ results in an equivocity: the same term (‘light’ or ‘fire’) is used to denote two different things (substance and power). Conversely, the proper terms become polyonyms: ‘fire’ and ‘light’ denote, interchangeably, here the illuminating substance and there its illuminating power. Exegetically, the synecdochical, polyonymous, and equivocal use of ‘light’ and ‘fire’ helps underline the link between the work of the first day (phōs = light) and the work of the fourth day (phōstēres = luminaries). But there is more going on here than simple rhetorical devices. The synecdochical, polyonymous, and equivocal use of ‘fire’ and ‘light’ is a manifestation, at the level of language, of the unbreakable ontological entailment that binds fire and light inextricably together in the physical universe. ‘No light without fire’ is then the basic tenet behind Gregory’s exegesis of day one and that already implies a certain theory of causation. The ontological entailment of fire and light together with the rules of convertibility and simultaneity that it implies leave no doubt that Gregory understands light in the sense of a natural power or innate capacity of fire necessarily coexisting with it.¹³⁷ One can ¹³⁶ In sections 69–73 (on the creation of the stars), Gregory uses cognates of ‘fire’ on three occasions: 65 GNO 72.20 hē purōdēs kai phōtistikē dunamis; 66 GNO 74.5 tēs purōdous ousias; 69 GNO 75.14 tēn kinēsin tou puros. These references help the modern reader realize that Gregory is referring to (celestial) fire even though he uses light terminology, see e.g. 66 GNO 74.11–12: tou phōtos moriōn = particles of light (i.e. fire); 67 GNO 74.14: en tēi phōtistikēi ousiai tēs hēliakēs phuseōs = in the illuminating (i.e. fiery) substance of the sun, etc. ¹³⁷ For dunamis (‘power’) in ancient physics as an elemental property that varies in degrees of intensity, see Tim. 32a1, 33a3, 52e1, 56c3; Aristotle, Phys. III.5 (204b14–19); Pritchard (1990); Zeyl (2000), xxxix. For late antique philosophical theology see Barnes (2001) and the collection of essays in Marmodoro and Viltanioti (2017). According to Barnes, ‘power means the affective capacity (or capacities) of any given existent distinctive to the identity of that existent’ (p. 7, see also p. 10). Power in its ‘proper sense’ is the unique power of an existent ‘that is distinctive or peculiar to a thing and thereby identifies the nature of that existent’ (p. 8). The main example that Barnes uses for power in its proper sense throughout his book is heat. Light is analogous to heat: it is the unique capacity of fire to illuminate, i.e. a power of fire ‘in its proper sense’. As such it is distinctive of fire’s nature and therefore identifies fire’s nature as luminous. According to Marmodoro (2017), 2, ‘powers are instances of physical properties that enable their possessors to bring about or suffer change, when the conditions are appropriate’. Those powers that bring about a change are ‘active’; those that dispose the possessor to suffer a change are ‘passive’. On this account, light is the active power of fire to illuminate and the passive power of the medium (e.g. air or water) to be illuminated. Two other studies have further specified that in Basil’s writings light qualifies as a Porphyrian ‘proprium’ of fire, see Radde-Gallwitz (2009), 131–7, 154–69; DelCogliano (2010), 219–22. According to this view, Basil used Porphyrian propria as ‘distinguishing marks’ (idiōmata) of species, convertible (antistrephei) and connatural (sumphuton) to the species and therefore sufficient for identifying the species without yet defining it. On this account, light is connatural to fire and a distinguishing mark of fire. Light identifies fire and fire alone, obeying the rule of convertibility: ‘no light without fire’.

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speak in this sense of light as being ‘connatural’ or ‘consubstantial’ with fire.¹³⁸ Indeed, in the passage from the Apology, Gregory speaks of light as being ‘inborn’ (eggenēthēnai) to fire. In other contexts, he speaks of light as a ‘natural property’ of fire (C.Eun. III.6 GNO 28.10 phusikēn idiotēta), as ‘innate’ to fire (C.Eun. I.1 GNO 415.2 sumphuēs), and as ‘coexisting’ with fire (C.Eun. I.1 GNO 532.8 sunuphistamenēn).¹³⁹ Fire and light are ontologically intertwined through the fundamental causal link that binds together a substance with its natural power. What is the nature of this causal link? Gregory clearly thinks that light is the power of fire in the sense that it brings a certain change in the world: it illuminates space.¹⁴⁰ But once we start wondering why it is the case that fire’s light illuminates space, we start running into difficulties. We can state as observational fact—and for Gregory also as a scriptural fact—that fire has the power to generate light and perhaps also that only fire has this power.¹⁴¹ And we can also establish a relation of metaphysical priority, namely that if fire has the innate power to generate light, then this has to do with the fire’s own nature. Fire is itself luminous and this explains why fire is theorized in the Apology as the illuminating substance or nature. The causal relation of fire and light is an expression of the broader metaphysical principle that species have causal or explanatory priority over their properties qua formal causes.¹⁴² To the question ‘Why is it that the sun radiates light?’ the answer is ‘Because it is made of fire.’ That is to say, the nature of fire explains how it is that fire radiates light. Which particular aspect of fire’s nature? Gregory speaks repeatedly of fire as the ‘illuminating substance’ or ‘illuminating nature’ (see e.g. phōtistikē ousia, phōtistikē phusis, phōtistikos logos, phōtistikē dunamis: In Hex. 10, 12, 64–70), and so does Basil (phōtos phusis, Hex. II.7, VI.2), indicating that they both understand luminosity as an essential qualification of fire (similarly to humans being rational). It is fire’s innate luminosity, then, that explains why fire has the power to generate light, making other things luminous.¹⁴³ Once luminosity is accepted as fire’s essential property, it exhibits great explanatory power. First, it shows that ‘light’ can be (and is often) used equivocally in the sources to denote several different properties: (a) ‘being naturally luminous’

¹³⁸ It is precisely in this sense of connaturality that light was used as an argument for the ‘consubstantiality’ (homoousion) of the Father and the Son in the fourth-century trinitarian debates, see Prestige (1952), 214, 227, 230, 243, 257; Pelikan (1962), 63–72; and more recently Barnes (2001), 274–88; Ayres (2004), 41–52; O’Collins (2012), 114–19; Tanner (2012), 122–6. ¹³⁹ Gregory’s terminology evokes strongly Porphyry’s treatment of propria as ‘connatural’ (sumphuton), and so does Basil’s, see e.g. Hex. I.8 GCS 15.8–12 (enuparchousōn poiotētōn). This reinforces the view that the Cappadocians construe light as a proprium of fire in the strict Porphyrian sense, see Callahan (1958), 45–6; Radde-Gallwitz (2009), 160–1, 162–9, and 200–7; DelCogliano (2010), 219–21. ¹⁴⁰ See In Hex. 10, 12, 25. ¹⁴¹ This is certainly the case with Cappadocian physics, but I nuance the premise (‘perhaps’) to leave room for the contrary Peripatetic view, according to which heavenly light is the property of aether. I discuss this in more depth in Chapter 3. ¹⁴² See Barnes (2003), 258, 265, 293. ¹⁴³ See further Appendix B.

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as essential property of pure elemental fire; (b) ‘the power to generate light/make things luminous’ as proprium of every fiery body; and (c) the passive capacity or affection of an external patient, such as air or water, to ‘become luminous’ in the presence of fire. Second, it shows how the causal priority works between the different properties: it is because of (a) that (b) exists and (c) occurs.¹⁴⁴ Why is fire itself luminous in the first place? And why is it that luminosity radiates light? These are questions that reach the limit of phenomenality and what the sensible world can teach us. Gregory claims that it is impossible for us to grasp the logos that explains why light is the natural capacity or power of fire. We may see how light relates to fire, as natural property to substance, but the reason why this particular property relates to this particular substance is elusive. Apparently, we stand in front of an intrinsic feature of the world that is impossible to analyse further. We must simply accept the consubstantiality of light with fire as quasiaxiomatic. It is a brute fact, part of how the world is made, expression of the inner fibre of nature. That makes it futile to enquire further into the logos that binds fire and light as substance and property. We can only accept the relation as given and study its consequences.¹⁴⁵ The most fundamental consequence of the causal link of fire and light is that light is part of the physical world as fire’s sensible natural power. Light reveals the activity of fire to the senses by making things luminous just as heat reveals the activity of fire by making things hot. Light is a property signifying the physical activity of a luminous agent. But we already saw that the term ‘light’ also denotes

¹⁴⁴ The theory seems to ingeniously combine the Porphyrian theory of predication with the Plotinian theory of causation, also known under the signature name of ‘double activity’, of which light is a case in point, see Bradshaw (2004), 73–96; Emilsson (2007), 22–68; Kalligas (2012), 49–63; Gurtler (2018), 157–61. ‘Being essentially luminous’ (Porphyrian differentia and Plotinian first activity in the sense of the internal activity of a thing’s logos) explains why fire has the natural capacity to ‘generate light’ and ‘make other things luminous’ (Porphyrian proprium and Plotinian second activity in the sense of the external activity of a thing’s logos). Indeed, Gregory theorizes the generation of light from fire in terms strongly evocative of a Plotinian second activity emanating naturally from an undiminished source at least once, see Ref. Eun. 89–90 GNO 349.2–11. In addition, Basil seems to hold that elemental powers designate a field of intersection of essential and peculiar properties, see Hex. IV.5 GCS 64.20–65.5. In the case of fire, for example, the theory means three things: that there is only one substance that is essentially luminous; that there is only one substance that has the natural capacity to generate light; and that there is only one substance that has the natural capacity to generate light because it is essentially luminous. If so, Basil solves, for natural elements, two traditional problems that trouble dialecticians of old: how can propria say what something is; and how can propria explain what something is, see from a philosophical perspective Barnes (2003), 59, and from a theological Stead (1994), 133. In suggesting that elemental powers are unique external manifestations of unique internal properties, Basil also suggests that powers convey substantial information about the elemental species they belong to without being predicated substantially of it. Gregory applies the doctrine to light, see C. Eun. III.6.12–14. ¹⁴⁵ In other words, knowing that fire is essentially luminous does not mean that we know why fire is essentially luminous. On the Cappadocian distinctions between ‘knowing that’, ‘knowing what’, and ‘knowing how’, and the essential unknowability of substances, see Radde-Gallwitz (2009), 122–31, 154–69, 200–1; DelCogliano (2010), 137–8, 189–260. In particular, the essential unknowability of light’s logos owes a lot to Plato’s discussion of colours in Tim. 68b6–8 and 68c7–d7, see Ierodiakonou (2005b), 228–9, see further Appendix C.

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the agent itself, the fiery substance. Indeed, Gregory uses light terminology to signify several kinds of fiery phenomena: fire’s sparkle or glitter (lampēdōn); the light that flashes forth from a luminous body surrounding it, like the corona of the sun and the aura of the stars (apaugasma); a fire’s ray or beam (augē). At the same time, the terms are also used as cognates of luminous properties: gleam, glow, or lustre (lampēdōn); shine, radiance, or splendour (apaugasma); and brilliancy or brightness (augē). It seems that we stand in front of a technical vocabulary that denotes fiery phenomena together with the luminous qualities they exhibit. ‘Luminescent glow’, ‘shining aura’, ‘bright beam’ is perhaps the fuller meaning of what these terms express.¹⁴⁶ If this is a plausible interpretation of the technical vocabulary that Gregory uses, it means there is not one thing that corresponds to the notion of ‘light’ in Gregory’s physical universe. ‘Light’ instead denotes a process of emanative stages of fire with corresponding qualifications of luminosity. This notion of ‘light’ captures a continuum of physical fiery phenomena together with the sensible qualities that characterize them. Gregory’s language delineates a range of meanings capturing what I will from now on designate as ‘the physicality of light’. The term denotes that light manifests both as a sensible quality and a physical power of fire in the world. The physicality of light is the cornerstone of hexaemeral power causality.¹⁴⁷ Being the physical manifestation of the first natural substance, light not only reveals the luminous nature of its bearer but also becomes the subject matter of proper scientific enquiry in Gregory’s physical world. In its hexaemeral version, the physicality of light means that light as a power and property of fire has itself a corporeal nature.¹⁴⁸ The physicality of light thus grounds the subject matter of the hexaemeral physics of light. Furthermore, the physicality of light explains why hexaemeral light is logically and ontologically linked to fire, while vision remains external to light’s definition: vision is an incidental change that fire brings to the world on the condition of the presence of a percipient subject (warmth is another such incidental change). Fire, however, radiates light (and heat) irrespectively of the presence of any percipient subject. Consequently, fire has causal or explanatory priority over light, and light has causal and natural priority over sight. Causal or explanatory priority means that fire is the explanans of light and light of sight. Natural priority means that the ¹⁴⁶ The translation is indicative. Many contemporary readers oscillate between material (light as fiery emanation, e.g. O’Collins (2012), 115–16) and immaterial readings (light as quality, e.g. Tanner (2012), 125). I here suggest that Gregory’s hexaemeral semantics is more nuanced than usually suspected, extending in both directions. This is an expression of the general pre-theoretical assumption of the ancient mindset that luminosity is an inherent property of physical substances, according to the presence of fire in them, see Sassi (2015), 264–8. Luminosity is thus a paradigmatic case of Gregory’s basic metaphysical intuition that qualities are physical aspects of material objects, see Marmodoro (2015). ¹⁴⁷ On the notion and philosophical origins of ancient ‘power causality’ see Barnes (2001), 21–53 and more recently Marmodoro (2017), 11–45. On the Christian reception see the collection of essays in Marmodoro and Viltanioti (2017). ¹⁴⁸ As I explain further in Chapter 3, in the corpuscular theory of light adopted by the Cappadocians light is itself a fiery substance. See further Appendix B.

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absence of light co-removes vision but the absence of an eye does not co-remove light.¹⁴⁹ In other words, it is impossible to have vision without light, though it is perfectly possible to have light without the existence of a perceiving subject. The causal and natural priority of light over sight is fundamental to the hexaemeral narrative: God created light on the first day, though there were no (bodily) eyes yet to contemplate the phenomenon.¹⁵⁰ The causal priority of fire over light and the causal and natural priority of light over sight are the two cornerstones of the hexaemeral power causality as applied to light. In turn, power causality is the metaphysical foundation of the hexaemeral physics of light and the reason why light cannot be construed as ‘subordinated’ to sight in any meaningful sense. The above remarks do not represent a novelty in ancient physics. The idea that fire is itself luminous is trivial in ancient physics.¹⁵¹ The consubstantiality of fire and light, its premises and logical consequences (ontological entailment, synecdochal and equivocal use of terms denoting both substance and property) can be traced at least as far back as the Presocratics and are clearly attested in the Platonic corpus.¹⁵² The use of the same technical vocabulary to denote both a substance and a quality will create tensions, but will continue to have many followers.¹⁵³ Thus, by the time of Gregory, the intrinsic connection of light to fire and the ¹⁴⁹ On the two forms of priority, causal or explanatory and natural, see Aristotle’s Metaph. IV.5.1010b35–1011a2 (causal); Metaph. V.11.1019a1–4 (natural); Barnes (2003), 248–50, 258. ¹⁵⁰ See Basil, Hex. II.7 GCS 33.21–2; further Bradshaw (2004), 214. ¹⁵¹ See e.g. De an. 419a22–4; Sens. 439b14–18; De coloribus 791b6–14; Optics II.24 Lejeune 23.3–4; Ennead II.1.7. ¹⁵² On the vocabulary of ‘fire’ and ‘light’ in Greek literature see the magnificent study of Mugler (1960). On the synecdoche, polyonymy, and equivocity of ‘fire’ and ‘light’ in the context of early Greek natural philosophy see already Parmenides’ poem, in which phaos denotes both ‘light’ (B 1.10) and ‘fire’ (B 9.1) as equivalent to pur (B 8.56); Tarán (1965), 231 n.1; Aristotle, Phys. I.5 188a20–2, with the correction of Simplicius, In Phys. IX.25.15–16, and the comments of Ross (1936) ad loc. Similarly, in Empedocles phōs (B 84.5) and pur (B 84.10) are used interchangeably in the celebrated ‘lantern simile’ (B 84 DK = 88 Wright), which I discuss in Chapter 3. In the Platonic corpus the most obvious instance of synecdochical and equivocal use of light language is the Timaeus: in 39b4–5 phōs is used instead of pur to denote the sun’s fire; in 45e1–2 phōs denotes fire’s physical power of illumination; and in 45b5, 45c3, and 58c6–7 phōs denotes the illuminated medium. Plato’s light language is adopted by the hexaemeral authors, see e.g. Philo, Somn. I.72, the most striking example of which is Basil’s emulation of Tim. 39b4–5 in Hex. VI.2 GCS 91.9–11. For a taxonomy see Chapter 3, section 3.3.3. ¹⁵³ The dissociation of light as a property (illumination) from light as a substance (fire) starts with Aristotle’s famous criticism of the corpuscular ray theory in the De an. II.7 and the Sens. 2, see Burnyeat (1995); culminates in Alexander of Aphrodisias’ construction of light as a relative property of the transparent, see Schroeder (1981); Caston (2012), 154–68 (nn. 375–417), Ierodiakonou (2018); and reaches the Platonic tradition through Plotinus’ sharp distinction between light as corporeal substance (fire) and light as fire’s incorporeal activity (radiation) which causes the illumination of space, see Schroeder (1984) and (1992), 24–39; Kalligas (2012); Gurtler (2018). In the other camp, the Stoics hold on to the old Timaean identification of light as a species of fire and the corporeality of the light beam, see Philo, Aet. 86.1–88.9 and Boyancé (1936), 65–78. So, apparently, do other Platonists, who continue to think of light as a radiant and luminous substance causing illumination, see Galen, PHP VII.6.2 (= 629.2 de Lacy) and Com. Tim. (Larrain) fr.18 (substance), fr. 19–20; Nemesius, DNH III.40.23–41.4 and VII.58.11–14 (= Aëtius, Plac. IV.13); Priscian, Answers to Chosroes 51.33–52.5. As will be shown in Chapter 3, Gregory borrows from both tendencies, distinguishing the luminous substance (fire) from its power of illumination (‘radiant light’) and its illuminating effect (‘ambient light’), but still theorizing radiant light as a physical, albeit extremely refined, emanation of fire.

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implied chain of causality are widely accepted maxims of Greek physics. The full force of Gregory’s thought becomes apparent only when one applies Greek physics to hexaemeral exegesis. In this chapter I have discussed at length why the fusion of Greek physics with hexaemeral exegesis proved so daring. Remember the debates about the literal or allegorical meaning of the biblical creation narrative. Recall the attacks against its rationality. Call to mind the doubts against the coherence of hexaemeral physics. From the point of view of late antique hermeneutics, the physicalist reading of Genesis was the least obvious path a hexameral author could take. It was worth the effort. Once Gregory was able to assert the internal link between fire and light through a skilful application of Greek physics to the biblical creation narrative, the doubts were dispelled, the charges dropped, and the objections answered. The intrinsic connection of light to fire became the key that unlocked the hidden hermeneutical potential of the biblical narrative. Gen. 1:3 had finally acquired a clear reference: it referred to the emergence of light together with the physical substance that generated it, namely fire. Now everyone could see that the cosmogenesis started with the creation of physical light. It was therefore the story of creation of this sensible world. In the hands of Gregory, the causal relation of light to fire became the catalyst for a physicalist interpretation of the whole creation narrative. Yet Gregory was not alone. He was merely executing, albeit brilliantly, the exegetical plan that his brother Basil, and Origen before him, had already conceived. Gregory championed a whole school of thought. ‘No fire, no light’ is then the fundamental tenet that Gregory uses to unlock the meaning of Gen. 1:3. The premise invites the reader to explore further the exegetical value of the physicality of light. It inaugurates a certain exegetical pattern by suggesting that if fire is the subject matter of day one, then the other elements must be, for reasons of hermeneutical consistency (i.e. due to the heirmos of Scripture), the subject matter of the following days of creation. It also opens up a bridge from physics to metaphysics by grounding the exegesis of day one on the substance–property relation, as an expression of the primitive—viz. irreducible— relation of a substance to its natural, productive power.¹⁵⁴ The result is the transformation of a hermeneutical working hypothesis into a verifiable exegetical project. What began as constructive hermeneutics with Basil, namely the possibility of a sustained physicalist reading of Genesis 1 starting with ‘light’, acquires with Gregory a robust theoretical grounding in contemporary physics. Every fourth-century hexaemeral author draws more or less extensively from the same

¹⁵⁴ It should be noted that light as power is not an exclusively Greek idea. As Endo (2002), 165, 250, has shown, early Jewish exegetes understood the creation of light as a manifestation of the sovereign power of God. That means that the hexaemeral exegesis of light brings together two intellectual streams: the Greek metaphysical tradition of power causality and the Jewish exegetical tradition of light as manifestation of the power of God.

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pool of physical theories as Gregory.¹⁵⁵ But no one gives us the full story of light so clearly and magisterially narrated as Gregory does in the Apology. To suggest that Gregory’s work goes against Basil or beyond the scope of hexaemeral exegesis, as the proponents of the discontinuity thesis do, would result in the loss of a valuable piece of information for understanding the hexaemeral project. It would dissociate the hexaemeral literature from the work that provides the key to deciphering why and how the hexaemeral exegetes regarded primordial light as consubstantial with (while causally dependent on) elemental fire. If my analysis is correct, this is a key that we cannot afford to lose. The Apology gives us the ultimate textual proof that a proper physics of light was developed in late antiquity as part of the JewishChristian hermeneutic and apologetic tradition.¹⁵⁶ This hexaemeral physics of light understood itself as a proper enquiry into the physicality of light as the natural capacity or power of fire. It is a genuine enquiry into light’s own physical behaviour and characteristics.

¹⁵⁵ See Basil, Hex. II.3: light is the natural power of fire (phōtistikon gar to pur); II.7: the first fiat refers to the creation of the luminous substance (phōtos phusin); both doctrines combined in VI.2: tote men gar autē tou photos hē phusis parēchthē; [to pur] tēn tou phōtizein tēn dunamin echon. Ambrose, Exam. II.3.14: light as the intrinsic property of fire (sive de flammae lumine lumen accendas); IV.3.9: light as the power of fire (virtutem inluminandi; ignis inluminant; vis inluminationis). Severian, Cosmog. I.4–5 PG 65:433–6: an exciting variant of the same doctrine as Basil and Gregory (Gen. 1:1–2a refers to the creation of the material ingredients [tas hulas], while the rest of the creation narrative refers to the shaping of particular beings; first fiat = creation of the element of fire [hē tou puros phusis]; fire has the natural power to illuminate [phusin lampousan]). Didymus’ text is badly damaged in the exegesis of Gen. 1:3–5. But we do get the physics of fire and power causality later, see Com. Gen. 233.20–9: fire (pur) has a twofold power (dittēn dunamin), to illuminate (phōtizon) and to burn (kaion). Cf. Theophilus, Autol. II.11 together with II.13 (lantern simile): light is the illuminating power of fire (to phōs phanerei; phainon hōsper luchnos). See also Stead (1994), 140–3. ¹⁵⁶ The hexaemeral physics of light and fire remains a constant theme in the subsequent tradition, see Zaganas (2017), 234–6.

3 The Nature of Light The Dawn of the First Material Form

So “Let there be light,” says God, that is: Let the primordial causes proceed from the incomprehensible hiding-places of their nature into forms and species comprehensible and manifest to the understandings of those who contemplate them, “and light was made,” that is by the will and utterance of God the obscurity of the primordial causes proceeded into revealed forms and species. (Eriugena, Periphyseon III 692c8–12 tr. Sheldon-Williams) This book began as an enquiry into the ancient physics of light that grounded the meaning of the early Christian theological language of light. The enquiry stumbled upon two methodological obstacles. The first was the objection, raised by contemporary historians of science of the calibre of Simon and Smith, that there was no ancient physics of light, at least not in the sense of an enquiry into the properties of light as an agent of change in the world, other than its role in the mechanism of vision. On this view, only the properties relevant to visual perception have been the subject matter of ancient theories of light. For an enquiry into the nature of light as such, we would have to wait for the dawn of modern science. The second objection was raised by ancient readers of Scripture and modern theologians who contested, for different reasons and from different perspectives, the coherence of a hexaemeral physics of light. Ancient erudite critics of Scripture like Galen and Celsus argued that the doctrine of creatio ex nihilo eliminated the role of the material principle, and hence of physics, in the biblical creation narrative. Modern theologians of the status of Barth and Bultmann insisted that Scripture ought to be kept separate from science, and hence from physics, rendering the hexaemeral theories of light irrelevant from the point of view of biblical exegesis. These obstacles might explain why there has been no systematic study of ancient theories of light in general and of their hexaemeral reception and further development in particular. At the same time, it was clear that if such a study were ever to take place, the above objections ought to be taken seriously and be either proved, condemning the initial enquiry as a failed project, or disproved and, in view of the obvious fact of contrary textual evidence, be set aside to let the investigation proceed.

The Metaphysics of Light in the Hexaemeral Literature: From Philo of Alexandria to Gregory of Nyssa. Isidoros C. Katsos, Oxford University Press. © Isidoros C. Katsos 2023. DOI: 10.1093/oso/9780192869197.003.0004

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In the first chapter of this book I dealt with the first objection. There I argued that there is compelling textual evidence for a proper study of the physics of light in the ancient world and that the road was open to pursue this new approach from within the body of hexaemeral literature. In the second chapter of the book I carried the argument forward, addressing the second methodological objection. I investigated the reasons why hexaemeral exegetes felt no scruples in blending science with biblical exegesis, seeing fit to place the physics of light at the service of Scripture. The analysis showed that hexaemeral exegetes relied on the ‘hard science’ of their time to demonstrate that light acts as a physical agent in the world. The demonstration of the physicality of light played a vital role in biblical hermeneutics. It paved the way for a physicalist interpretation of the biblical creation narrative, the kind of reading that we recognize today as ‘literal’. And since the physicalist interpretation passed through the theory of the four constituent elements of the world and their sensible qualities, the exegesis of light signalled, from the first verse of Genesis, the recourse to physics for the sake of hermeneutics. Through the physicalist interpretation of the first fiat, it was now possible to argue that the biblical creation narrative defined the realm of phenomenality, revealing the laws of nature that underlie all stages of God’s creative act. These laws were the manifestation of the technical logos, immanent in all six stages of God’s creative act, viz. in all the hexaemeron, guiding each particular thing to its fruition, as a well-functioning part of a meaningful whole. The second chapter of my study culminated in the view that the logos immanent in light was the logos that defines the irreducible relation of a substance to its natural capacity or power. The enquiry revealed, with the help of Gregory’s Apology, that hexaemeral light was theorized as the natural capacity or power of fire, the first of the four physical elements. The hexaemeral physics theorized fire (the luminous substance) and light (its illuminating power) in terms of an inseparable unity: light coexists with fire and acquires its physical characteristics through its intrinsic relation to it. Even more than that, light is fire. And since the physical consubstantiality of light and fire, together with the semantic co-extensionality of the vocabulary of ‘light’ and ‘fire’, could be derived from both the Greek and the scriptural thought world, the hexaemeral authors had produced a disarming argument against their critics. The hexaemeral physics of light served simultaneously a double purpose: biblical apologetics and scriptural hermeneutics. In this third and final chapter, I pick up the thread from where I left it and examine, in more detail, the meaning of the physicality of light and its ontological link to fire. The enquiry will take us through ancient theories of light and their transformation in the hands of hexaemeral exegetes due to their scriptural commitments. At the heart of my enquiry lies an ancient intuition about light’s liminal corporeality. Light appears in the ancient sources as a singular phenomenon marking the limits of the material world both spatially (where the physical universe ends) and qualitatively (where materiality begins). Such an insight

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triggers fascinating questions regarding light’s physical nature: if light marks the limits of the material, does it belong to the physical world? Does it have physical characteristics? Can we adequately grasp them, let alone describe them? In short, how are we to capture the physicality of light if light marks the limits of physicality itself? It is this set of questions that animates the remaining part of my study. In what follows, I leave behind all previous reservations and produce a systematic theory of hexaemeral light, which I reconstruct from a combined reading of Basil’s Homilies and Gregory’s Apology. As my reading proceeds, I clarify further why I perceive the two works as expounding on the same physics of light, building on one continuous Cappadocian project. My reading focuses on three axes: the substance of light (‘fire’); the emission of light (‘radiant light’); and the effects of light in space (‘ambient light’). This leads me to a discussion of the nature of the heavenly bodies, the nature of the light ray, and the role of the medium in light mechanics. The investigation culminates in a causal analysis of light, tracing all the stages of light’s dissemination, from the luminous source to the illumination of space. Faithful to the hexaemeral project, my reading proceeds in two parallel planes, those of hexaemeral physics and hexaemeral hermeneutics. This double reading produces a performative argument, showing that, from a hexaemeral perspective, physics and hermeneutics go hand in hand, contemplation of nature being the other side of the contemplation of Scripture. If my argument is correct, early hexaemeral exegesis included not only a detailed analysis of the physics of light but also the metaphysical grammar that supports it. What at first sight appears to be a reference to the creation of physical light, namely Gen. 1:3, turns out to be a reference to the very nature of light, introducing to creation, the first ‘material form’. The logic of the creation narrative then appears to have a Heraclitean ring: just as the logos of nature likes to hide, so too does the akolouthia of Scripture. As the reading proceeds and the understanding of Scripture deepens, the physics of light transforms into a genuine metaphysics, but not before the reader has traversed material creation, only to realize that at the end of the phenomenal world lies the endless sphere of the ineffable. Having reached the limits of phenomenality, the reader is finally prepared to reprise the contemplative exercise, this time though from a different angle: creation as the dawn of an intelligible world.

3.1 Between Physics and Metaphysics: The ‘Immateriality’ of Light 3.1.1 Scriptural Questions One of the most striking features of Basil’s hexaemeral exegesis was the emphasis on the aesthetic dimension most prominently expressed in his lyric encomium of

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light.¹ In Basil’s hexaemeral exegesis, light became the paradigmatic expression of the intrinsic beauty of all creation, yet not because of its alleged symmetrical structure, which it altogether lacked, being a simple substance, but because of its brightness. The best way to demonstrate this was through the contemplation of the gentle radiance of the light of the stars (II.7). There are two features in Gregory’s exegesis that strike the reader when compared to Basil’s. First, there is a remarkable silence about the aesthetic aspect of light. Anyone who has read Basil’s Hexaemeron cannot help but initially wonder why there is no reference to the encomium of light in the Apology.² Second, and on a deeper level of reflection, one begins to understand that the Apology has a different way of paying tribute to the beauty of light: it gives us the means to figure out the mechanics of nature that make light so special. In his exegesis of day four, Gregory provides several hints about the brilliancy of cosmic light and the celestial mechanics that govern it. Thus, instead of an encomium of light the Apology gives us the physics that explain it. Claiming that light is the innate power or capacity of fire is one thing. Claiming that the light of the stars is the innate power or capacity of fire is another. It presupposes that the stars are made of a fiery substance. But that was a concession that not every erudite reader of Gregory was willing to make. The debate about the substance of the heavenly realm and the bodies that abide in it was vigorous, notoriously controversial, and almost entirely speculative.³ In joining the discussion, Basil adopted a dialectical strategy, partly sceptical and partly dogmatic. The core argument was sceptical: if the opinions of the schools dialectically oppose each other, they are mutually refuting. The consequences of the argument were dogmatic: the inherent incapacity of the scientific community to reach a consensus as regards the substance of the heavens entitles the hexaemeral exegete to the freedom to follow the teaching of Scripture without further concerns about competing alternative theories.⁴ Behind Basil’s dialectics lies a fundamental epistemological premise: the logos that is at work in the heavens is by its nature beyond the human capacity to grasp.⁵ ¹ See Chapter 1, section 1.1.3, with the relevant passage cited in full. ² In the Apology there is only reference to the beauty and goodness of all creation (§31), even in the absence of light (§21). Gregory had already included the encomium of light in the first chapter of the De hominis opificio (I.5 Forbes 118), in which he summarizes Basil’s hexaemeral exegesis. The absence of the encomium of light in the Apology is therefore deliberate and clearly indicates that Gregory’s skopos is not to repeat Basil’s exegesis but to carry it forward. ³ For a survey of the available opinions and their variety see Achilles, De universo 5 (on the substance of heaven), 11 (on the substance of the stars), 19 (on the sun), 21 (on the moon); Aëtius, Plac. II.11 (on the heaven: what is its substance), 13 (on the substance of the stars, moving and unmoved, and how they came to be); 20 (on the substance of the sun and that there are two and three suns), 25 (on the substance of the moon). See further Mansfeld and Runia (2009), with comments ad loc. ⁴ See Hex. I.8 (on the substance of heaven) and III.3 (on the number of heavens). The same logic applies also for the enquiry into the nature of the stars in homily VI.1. ⁵ See Hex. VI.1 GCS 89.8–9: megethos anthrōpinēs dianoias ekbainei; VI.10 GCS 107.4: logos arrētos.

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Thus, any theoretical attempt to give a full account of celestial physics is doomed to fail. Yet, with the help of a suitable scientific framework, we can grasp that there is a logos at work in heaven.⁶ The scientific contemplation of the world exceeded, of course, the needs of the large crowds of Basil’s audience. But it met the immediate demands of the erudite reader of Scripture. It was against this background that Basil formulated his idiosyncratic theory of the heavenly bodies as the celestial ‘vehicles’ (ochēma) of light.⁷ According to the theory, the work of the first day was the creation of light; the work of the fourth day was the creation of the luminaries as vessels of the primordial light. The theory sought the support of the letter of Scripture, which was seen as distinguishing between the light (Gen. 1.3 phōs) and the light-bearers (Gen. 1.14 phōstēres) that shed it forth (eis phausin; phainein). The theory also had the support of some esoteric teaching of the Church,⁸ with possible allusions to the theory of the luminous or spiritual body.⁹ We certainly find the characteristic distinction between the phausis (kindling) of the first day and the phōstēres (luminaries) of the fourth in Origen’s newly discovered Homilies on the Psalms, in an apocryphal context.¹⁰ Basil reproduced the Origenian distinction between the light of the first day and the luminaries of the fourth, and left only allusions to its apocryphal background, eschewing the inner logic of the Origenian exegesis.¹¹ He was thus able to come up with an interpretation that paid attention to the scriptural text and relied on the interpretative tradition. What he did not come up with, however, was a new explanation of the inner logic of Scripture once he had eschewed the old, namely why ⁶ See Hex. VI.1 GCS 88.20–1: tēi de tou logou periousiai pros ouranon auton huperarthēnai dunamenon. ⁷ See Hex. VI.2. ⁸ See Hex. I.8 GCS 14.20: en idiōtikois rhēmasin; III.3 GCS 42.25–6: ton ekklēsiastikon logon. ⁹ Henke (2000), 283–4, links Basil’s astral vehicle (ochēma) of light with the celebrated Platonist doctrine of the luminous ochēma of the soul (to augoeides tēs psuchēs ochēma) and its correlative Origenian doctrine of the luminous spiritual body. The fact that Basil is here drawing from Origenian material of an apocryphal nature reinforces the assumption of a possible link with the theory of the vehicle. But the link is not straightforward. Basil’s ochēma is the body of the light; the PlatonistOrigenian ochēma is the light that functions as the body of the soul. The role is inverse unless Basil thinks of light analogously to the soul of a star. This is possible. At the end of this section I argue that the Cappadocians thought of primordial light as the first immanent form of creation. If the soul is the form of the body (cf. De an. II.1 412a20–1) and primordial light is an enmattered form, then the heavenly bodies are indeed the ochēmata of the primordial light. On the theory of the luminous vehicle of the soul see Sorabji (2012), 306–8, and Mihai (2015), 98–104; for its Origenian counterpart see my discussion in Chapter 1, section 1.3.1. ¹⁰ See Hom. Ps. 73, III.2–3 GCS 255–6. The exegesis is textually based, see III.3 GCS 255.17: epi tōi rhētōi. The context, however, is apocryphal, see III.2 GCS 254.22–3: ta tēs sophias logia ta aporrēta kai kekrummena; III.3 GCS 255.15: kata tēn tropologian. ¹¹ Basil gives several allusions to Origen’s esoteric teaching of Christ as the true light of the world. He alludes to (but does not explicitly mention) Christ the logos as the theological teaching that is mystically (mustikōs) interspersed in the whole creation narrative, VI.2 GCS 90.13. And he speaks of Christ ‘the light of the world’, but only as a metaphor (hōs gar) that illustrates the physics of light (VI.2 GCS 91.6–1), while the purpose of Origenian exegesis is the inverse, i.e. to use light as an illustration of the incarnation of the logos in Christ. What Origen reveals, lifting the veil of the letter of Scripture, Basil conceals, leaving only hints behind. See further Chapter 3, section 3.4.2.

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God separated the light from its heavenly vessels by an interval of three days, especially if the heavenly bodies were necessary for the illumination of the cosmos (and if they were not, then why were they created at all?). Basil was aware of the hermeneutical challenge and went some way towards answering it: the biblical narrative mentions the creation of the sun on the fourth day, so that people realize that the sun is not the cause of creation (but part of it) and hence not the creator God. There is a clear anti-pagan message in Basil’s defence.¹² But does it solve the hermeneutical challenge? Clearly not. The exact same problem would still hold even if the sun were created in the second or the third day, so why the fourth? To press the question more exactly: why should there be an interval at all? What was the inner logic that led Moses to distinguish between the light and the luminaries that bear it? The question was raised by Peter and it fell upon Gregory to answer it.

3.1.2 Philosophical Investigations Gregory followed closely in Basil’s footsteps. On the one hand he professed his scepticism of the human ability to grasp the logos of the heavens. On the other hand, his scepticism freed him from the need to further explain his choice of celestial physics. All he needed to do was follow the lead of Scripture, reprise the theme of light as a property of fire from day one, and proceed directly from there. And that is precisely what he did. Sections 64–73 of the Apology contain the most extensive and detailed treatment of celestial physics of fire and light in the whole body of early hexaemeral literature, rivalled only by the most elaborate technical treatises on astronomy and physics of the time. If one thing is absolutely clear from reading these sections, it is the view that stars are made out of fire. Upon this premise stands and falls all of Gregory’s celestial exegesis. Gregory explains celestial light through a twofold process of separation (diakrisis) and concurrence (athroisis, sundromē) taking place on the first and fourth day, respectively (§§65–9). The diakrisis that took place on the first day was the separation of fire from the rest of the elements. The respective sundromē was the gathering of all the fire that was separated in heaven. Conversely, the diakrisis that took place on the fourth day was the distinction of the fire gathered in the heavens into an infinite number of parts. The respective athroisis was the gathering of all the homogeneous parts into countless subspecies (§65 tois idiois moriois pros ta suggenē te kai katallēla diakrinetai; §66 pantōn tōn katallēlōn tou photos moriōn allēlois kata to suggenes sumphuentōn; §73 pasēs tēs phōtistikēs phuseōs idikōs diafaneisēs).

¹² See Radde-Gallwitz (2017), 211, 217. On the ‘solar theology’ in late antiquity see the comprehensive study of Wallraff (2001). See further Armstrong (1940), 54–8; Dillon (1998–9); Moreschini (2018), esp. 376–7; Mace (2018), esp. 440–4. Christian hexaemeral exegetes vigorously attacked the ‘solar theology’, see Origen, CC VIII.66; Basil, Hex. VI.2; Ambrose, Exam. IV.1–2.

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These are the stars that we see in the night sky. Each star is made of a particular subspecies of fire, which occupies its proper place in heaven and sheds forth its own light. The infinite chorus of stars (§72 to apeiron plēthos tōn asterōn) betokens an immeasurable variety of luminous substances in heaven (§65 pollēn tēs phōtistikēs dunameōs diaphoran; §69 tas apeirous tautas tōn photon diaphoras). The brilliancy (doxa) of the light of each star, exhibiting its particular colour and radiant intensity (§65 astēr gar asteros diapherei en doxēi; tēs kata to phōs diaphoras), is the distinguishing mark of the subspecies of fire that constitutes it (§66 kata tēn diaphoran tēs egkeimenēs autōi idiotētos). Gregory’s celestial physics teaches us that the illuminating power of each celestial body depends on the particular details of the composition of its fiery substance; and that the latter composition also dictates the place that each celestial body occupies in the heavens.¹³ Luminosity then is an outcome of the correlation of the internal geometry (density and weight) with the external locality (place in the universe) of a fiery body: the more homogeneous the composition, the greater the concentration of fire particles in it; the greater the concentration, the lighter its weight and the swifter its upward motion; the lighter and swifter, the closer it moves to the outskirts of heavens; the closer to the outskirts, the purer and brighter the light it radiates. This is because the finest and lightest part of fiery substance (to men akrōs lepton kai kouphon tēs purōdous ousias) and entirely pure (kai katharōs aülon) dwells in the farthest limit of the material universe (en tōi akrotatōi tēs aisthētēs phuseōs), after which comes the intelligible and incorporeal realm (hē noētē kai asōmatos phusis); whereas the other part, which is more inert and heavy (to de argoteron kai narkodesteron), occupies the region beneath the fine and light part. (In Hex. 66 GNO 74.5–9, my translation)

I have here translated the key word aülon not as the expected ‘immaterial’, but as ‘pure’ in the sense of unmixed. There are obvious reasons for ruling out the possibility that Gregory thinks of celestial fire as immaterial. If fire is a substance, and as such has sensible qualities, it belongs to the physical world and cannot be, strictly speaking, immaterial.¹⁴ Aülon then has another meaning, and we can start unpacking it by following Aristotle’s lead in the De generatione et corruptione II.8 that fire is the most ‘form-like’ of the four elements. The information we get from Aristotle’s passage is worth recalling:

¹³ See In Hex. 66–7 GNO 74.2–20; 70 GNO 77.6–13; 72 GNO 78.1–22, which provide the explanatory principles behind Basil’s Hex. VI.3 and 10. ¹⁴ Fire may be the subtlest and lightest of all elements (to men akrōs lepton kai kouphon tēs purōdous ousias), but this still means that it has a minimum weight and density, no matter how light (kouphon) and rare (lepton) it is. Since weight and density are tangible qualities, fire belongs to the physical realm.

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Additional evidence seems to be furnished by the food (trophē) each compound takes. For all of them are fed by substances which are the same as their constituents, and all of them are fed by more substances than one . . . Although food is akin to the matter, that which is fed is the figure (morphē)—i.e. the form (eidos)—taken along with the matter (hulēi). Hence it is reasonable that, whereas all the simple bodies come-to-be out of one another, Fire (pur) is the only one of them which (as our predecessors also assert) is fed. For Fire alone—or more than all the rest—is akin to the form (kai malista tou eidous to pur) because it tends by nature to be borne towards the limit (pros ton horon). Now each of them naturally tends to be borne towards its own place; but the figure—i.e. the form— of them all is at the limits. (GC 335a9–21 tr. Joachim)

The simple comparison between the passage from the Apology and the passage from the De generatione et corruptione shows that Gregory adopts the Aristotelian premises of fire as the element that is more akin to the form (and in that sense more ‘immaterial’) in relation to the other elements because of its natural propensity to move to the limits of the material universe. There is one complication, however, with this comparison. For Gregory the natural place of fire is the whole heavens, covering the vast regions of the supralunary from its uppermost part to the sublunary. For Aristotle, by contrast, the natural place of fire is at the limits of the sublunary. The supralunary, as already mentioned, is the place of aether, Aristotle’s fifth element, which remains unmixed with the other elements, requires no nourishment, and has no weight.¹⁵ Aristotelian physics, then, do not fully support Gregory’s theory. We need to turn to the Stoics for a fuller understanding. The Stoic school accepted the presence of fire in the supralunary and thought of celestial fire as fire of the purest kind. According to at least one report, heavenly fire does not need fuel to sustain itself. It takes, therefore, no admixture, contrary to the fire in the sublunary, which is always mixed.¹⁶ Celestial fire was called ‘aether’ by some¹⁷ and at least Chrysippus spoke of ‘the purest part of the aether’.¹⁸ The superlative suggests a notion of gradation of fire according to the degree of admixture, from the most pure and unmixed state in the outskirts of the universe to fire mingled with the other elements the more we approach the terrestrial realm. The idea of a gradation of materiality as fire descends from the supralunary to the sublunary is given further support by the Stoic view that the elements were

¹⁵ Later commentators of Aristotle accepted the gradual purity of aether in the supralunary to account for the variety of heavenly bodies and the brilliancy of their light, as intimated by passages in the Aristotelian corpus like Cael. II.7 and Meteor. I.3 (340b6–10), see the note of Guthrie (1939), 176–9. The Aristotelian notion of aether is rejected by the hexaemeral authors for theological reasons, see Chapter 2, section 2.3.1. ¹⁶ See Stobaeus, Ecl. I.213.15–21 (= Long/Sedley 46.D). ¹⁷ See Diogenes Laertius, Vitae VII.137 (= Long/Sedley 47.B). ¹⁸ See Diogenes Laertius, Vitae VII.139 (= Long/Sedley 47.O).

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made out of fire by alteration and will eventually return into fire by resolution.¹⁹ Chrysippus called precisely that purest kind of primordial and end-state fire ‘light’.²⁰ This goes a long way towards explaining Gregory’s view of the different varieties of fire in the supralunary divided according to their density and weight, i.e. according to the two indexes of fire’s ‘materiality’. Moreover, Chrysippus’ identification of pure fire with light seems to accord nicely with Gregory’s exegesis of primordial light qua pure fire. Yet Stoic physics fails to give full support to Gregory’s theory. Gregory’s exegesis does not support the Stoic eschatological vision of an eternally recurring cycle of universal conflagrations. Nor does the Stoic protology, according to which the elements proceed from primordial fire by alteration, match Gregory’s diakrisis cosmogony, according to which the elements proceed from the tohu wa-bohu by separation. That means that the Stoic conception of pure fire/light as cosmological principle does not resonate with the cosmic principles of Gregory’s hexaemeral physics. Stoic pure fire/light does not fit in Gregory’s cosmogonical scheme. We therefore need to continue the search. This brings us to the Platonic camp and its fundamental tenet, derived from the Timaeus, that all material things are compounds of the four elements, including the heavenly bodies, which are made ‘mostly out of fire’ (40a). By the time of Gregory, there was quite some Stoic water poured into that old Platonic wine; and the mix was stored in Aristotelian wineskins. We thus see the early Plotinus reprising, in an aesthetic context, Aristotle’s view of fire as the subtlest element and closest to the forms: It [sc. fire] has the role of form (taxin eidous) in relation to the other elements, highest in position, finest of the other bodies, being as close as possible to the incorporeal, and is alone not receptive of the other elements, though the others receive it. For it heats them, but is itself not cooled, and is primarily coloured, whereas the others get the form of colour from it. So, it shines and glows as if it were form (hōs an eidos on). (Enn. I.6.3.20–5 tr. Gerson)

The late Plotinus refines and further develops this doctrine, adding Stoic colorations to its Aristotelian backdrop. In his cosmological treatise (Enn. II.1 On Heaven), Plotinus explains that the natural place of fire is in the highest regions of heaven (II.1.3); that celestial fire differs from the common flame (phlox) of our experience, which needs constant nourishment and burns (II.1.4); that this difference corresponds to the different constitution and behaviour of bodies in the supralunary and the sublunary (II.1.5); that the stars are made wholly out of

¹⁹ See Stobaeus, Ecl. I.129.2–130.13 (= Long/Sedley 47.A). The idea of gradation of materiality is of course much older, going back at least to Anaximenes, who explained corporeality purely on the basis of the condensation and rarefaction of air, see Kirk, Raven, and Schofield (1983), 144–53. ²⁰ See Philo, Aet. 90 (= Long/Sedley 46.M).

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pure, celestial fire, which is corporeal ‘light’ (phōs) (II.1.6); and that the mixed constitution of the celestial bodies that the Timaeus seems to refer to is not a mixture of elements but of elemental tactile properties, like solidity (from earth), cohesion (from water), and lightness (from air) (II.1.6–7). Plotinus thus distinguishes clearly between fire in the sublunary (flame, phlox) and fire in the supralunary (light, phōs) (II.1.7).²¹ The former (flame) bears all the attributes of Aristotle’s fire: it confines itself to the sublunary and is bright (lampron) and hot (zesin). But its powers die out (maranomenē) as it moves higher in the atmosphere. The celestial fire, on the other hand, bears all the characteristics of the Stoic pure fire, as even its name (‘light’) betrays: it radiates the purest light (tou phōs parechontos to katharōtaton); it obviously does not burn; its natural motion is circular (II.1.8); but most importantly, and in a striking similarity with Gregory’s doctrine, it is distributed in different varieties in the heavens to which correspond different degrees of luminosity: But as for the light in the heavenly region, some of it is variegated in proportions (en logois) in the stars so that it produces a difference in their colours (chroais) just as in their magnitudes (megethensin). The rest of the heaven is itself, too, of this sort of light (phōtos), but it is not visible due to the non-resistant fineness (leptotēti) and transparency (diaphaneiai) of its body, just as is the case with pure air, as well. And their distance (to porrō) should also be added to these factors. (Enn. II.1.7.43–9 tr. Gerson)

Plotinus’ view was further developed and explained by Proclus, who, in his great Commentary on the Timaeus, expounded the doctrine of varying degrees of materiality according to degrees of purity: nothing is visible separate from fire, from which one might infer that all bodies participate in fire, but different bodies have different sorts of fire. For light (phōs) and flame (phlox) are not the same thing, nor is flame the same thing as burning

²¹ Plotinus distinguishes here between two different senses of the term ‘light’: in one sense the term denotes pure, celestial fire (i.e. the substance of the heavenly bodies); in another sense it denotes the luminous power or capacity of any kind of fire. In the former sense light is a corporeal substance, in the latter sense it is an incorporeal ‘activity’. This is a clear case of equivocity (‘homonymy’), see Enn. II.1.7.25–30. The former sense of light as celestial fire Plotinus derives from Tim. 39b: ‘the god kindled a light (phōs) . . . the light that we now call the Sun’. The Timaean terminology finds parallels in the Homeric tradition, which denied that the sun was made of ‘fire’ (mē einai pur ton hēlion), being rather a ‘pure light’ (alla phōs katharōtaton), Stob. Ecl. I.25.6–7. See also ps.-Plutarch, Homer. 105 Kindstrand (ou pur estin ho hēlios all’ hetera tis kreissōn ousia). If we compare the Homeric tradition with Plotinus’ terminology it is clear that there was a widespread notion of celestial ‘light’ as a luminous substance different from fire. How far one would drive the difference was debated. While Aristotle would claim that it is not fire at all (see the following line of the passage cited above from the De Homero), Plotinus would claim that it is not sublunary fire or ‘flame’ (phlox). For the hexaemeral terminology of celestial light see the following section (3.1.3).

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coal (anthrax), but from higher up there is a deterioration (huphesis) of fire down as far as Earth. It proceeds from a more immaterial (aülotera), purer and less corporeal condition until it gets to the most fully enmattered (enulotata) and densely packed (pachutata) bodies. (In Tim. II.8.20–7 tr. Baltzly)

We clearly stand in front of the doctrine that also explains the behaviour of Gregory’s celestial light. The basic tenet of the doctrine is that there is a great distribution of kinds of fire in the universe as a direct correlation of each kind’s particular composition (purity) and structure (density), which in turn determines each kind’s location in heaven (natural place). To be absolutely clear, I am not here suggesting that Gregory is reading Proclus, who appears on the scene a generation later. If anything, Gregory is reading Basil, who theorized primordial fire as ‘the most pure and unmixed and immaterial light’ (Hex. VI.2 tōi katharōtatōi ekeinōi kai eilikrinei kai aülōi phōti). But I am suggesting that Basil and Gregory share a common point of view and parallel doctrines, as well as various details of terminology—the ‘immateriality’ of celestial corporeal ‘light’ most notably—with Proclus, which cannot be accidental.²² Gregory’s physics of light has an undeniable Platonist ring, situating his terminology of the ‘immateriality of light’ somewhere between Plotinus and Proclus.²³ If so, then the following ²² The multiplicity of philosophical (including Neoplatonic) influences of Cappadocian hexaemeral thought have been portrayed in their complex variety first by Robbins (1912) and more recently by Köckert (2009) and, as regards Gregory in particular, by Risch (1999). ²³ The most serious challenge to Plotinian and post-Plotinian influences in Basil and Gregory is raised by John Rist, who, in several seminal papers, argued that Cappadocian knowledge of Plotinian thought, direct or indirect, was very limited, suggesting instead a direct influence of Jewish-Christian Middle Platonic sources, especially Philo and Origen, and a direct access of the Cappadocians to the Platonic corpus itself, see Rist (1981), (2000), and the overview in (1996), 397–401. I here depart from Rist’s argument in favour of Plotinian and post-Plotinian influences: the Cappadocians indeed make limited use of the Plotinian theory of light. But this does not imply limited knowledge as well. The Cappadocians indeed learn from Origen and Philo how to read the Bible philosophically, including the idea of a physical world of gradating materiality in terms of purity, see e.g. Philo, Heres 146, 152; Origen, DP II.2.2, II.3.7, III.6.4. And they also learn from them how to understand the biblical language of ‘light’ as celestial fire, see Philo, Decal. 49; Origen, DP I.1.1–2 and 6, I.2.4–8, I.7.4. There is one exception. Philo and Origen do not seem to know of an ‘immaterial’ (aülon) light. I could find no occurrence of aülon connected to light in the Philonic corpus (TLG search), while Origen presses the opposite point, namely the ‘materiality’ of celestial fire/light, see DP I.7.5 GCS 92.10–11 (nam licet aetherium sit corpus astrorum, tamen materiale est), cf. also DP I.1.1 GCS 17.16 (corporali lumine). Having said that, Origen does allow for the same doctrine underlying Proclus’ ‘immateriality’ of light, using, however, a different terminology. In the Preface (§8) of the DP he speaks of asōmaton (id est incorporei) to denote the subtle aetherial substance of the demonic body, which ‘is by nature a fine substance and thin like air’. Later he claims that the scriptural equivalent of the Greek term asōmaton is acheiropoiēton, see DP II.3.6 (in fine) apud 2 Cor. 5.1. Interestingly, Plotinus also insists on the corporeality of celestial ‘light’ as fiery substance compared to the incorporeality of ‘light’ as luminous power or activity of fire, see I.6.3.18 and 19 (phōtos asōmatou—kai to pur auto para ta alla sōmata), II.1.7.26 and 28 (sōma—asōmaton), IV.5.7.33–42 (estin oun to apo tōn sōmatōn phōs energeia phōteinou sōmatos pros to exō; asōmaton kan sōmatos ēi), but at the same time, like Origen, tries to find ways of expressing its ‘immateriality’, i.e. fineness and subtlety, compared to the other elements, see I.6.3.20–2 (taxin eidous pros ta alla stoicheia echei, leptotaton tōn allōn sōmatōn, eggus on tou asōmatou), III.6.6.41 (feugon ēdē tēn sōmatos phusin). It is clear that both Origen and Plotinus try to find ways of expressing the ‘immateriality’ of celestial fire without creating the wrong assumption that it

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passage from Proclus’ Commentary is also helpful in deciphering Gregory’s celestial physics: enmattered (enulon) fire is one thing but immaterial (aülon) fire is another—that is, it is immaterial because compared to the matter of the things in the sublunary sphere it is immaterial (aülon)—and the one kind is destructible while the other is indestructible. While one kind is mixed with air, the other is pure. (In Tim. II.9.10–15 tr. Baltzly, italics in the original)

I consider this passage a fair approximation of Gregory’s remark on the ‘immateriality’ of heavenly fire, which is the reason why I have translated aülon as ‘pure’.

3.1.3 Cappadocian Answers There is one important detail which separates Gregory from the Neoplatonic tradition. The major part of the Apology is a sustained argument for the principle of mass conservation in the universe in spite of (and at the same time because of) the continuous interaction of the four elements (§§28–63). A vital role is attributed, by the law of conservation, to the hydrological cycle, i.e. the ever-recurring cycle of evaporation, condensation, and precipitation of water through the mediation of the sun’s heat (§§33–5). During its condensation, the water releases moist emissions in the form of exhalations that travel from the sublunary to the supralunary. The moist emissions result in an element exchange between the supralunary and the sublunary. The moisture that rises up to heaven nourishes the fire of the heavenly bodies (§§46–8, 53). This tells us that the celestial fire has a consuming nature, nourishing itself upon the exhalations that it receives from the belongs to the intelligible realm of the purely immaterial substances, escaping the physical universe. The term that the Cappadocians use for celestial light, however, is not asōmaton but aülon, a term which we also find in Proclus’ Commentary, e.g. In Tim. II.9.10. This speaks for a later terminological development: in a letter which is now correctly ascribed to Gregory Thaumaturgus (†270–5), Origen’s pupil, we still encounter the older asōmaton terminology for celestial light (accepting the conjecture [hēliou] kuklou as a reference to the solar disc), see Ad Philagrium §7 (= PG 46, 1105 transmitted as Nyssen, Letter 26 Ad Evagrium, with the comments of Slusser (1998), 29–32). A generation later, however, we see Iamblichus speaking of aülon pur in the sense of ‘celestial fire’ in the De mysteriis V.11.6, a text dated between 280 and 305, see Clarke, Dillon, and Herschbell (2003), xxvii. A very interesting hexaemeral parallel is Severian, Cosmog. I.4 PG 65:434: aülon pur. Severian’s homilies were delivered during Lent 401, see the detailed analysis of Carter (2000), which is a date later than Basil and Gregory and before Proclus. This reinforces my argument of an earlier (but post-Plotinian) Neoplatonic influence, for which I propose Iamblichus. The latter is already suspected in scholarship for influencing Gregory, see Heine (1995), 29–49; Cross (2002), 399. Apart from this terminological affiliation, the Cappadocian physics of light deviates in a crucial respect from Plotinus’ and Proclus’ celestial physics (see my discussion in section 3.1.3), which forbids us to call it ‘Neoplatonic’. Having said that, it is only by comparison to Plotinus and Proclus that we can retrospectively reconstruct in a meaningful way the Origenian-Cappadocian physics of light. That is why I give much more attention to the Neoplatonic theory of light than Rist would.

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sublunary. The theory of exhalations had wide currency in ancient physics. It had a Heraclitean flavour, echoing in several Stoic sources, and it appears to have acquired at least some support even within Middle Platonic sources.²⁴ Plotinus seriously considers it but, for his own reasons, explicitly rejects it.²⁵ Basil, on the other hand, endorses it, and with it the un-Plotinian view that celestial fire is nourished by the moist emissions released during the condensation of water in the atmosphere.²⁶ Gregory followed in his brother’s footsteps, adding certain important clarifications to Basil’s theory.²⁷ This raises the question why the Cappadocians chose to deviate in this respect from Neoplatonic physics. The reasons have to do with their hermeneutical—viz. scriptural—commitments. It appears that long before the Cappadocians a hermeneutical tradition had been established according to which there was no exception to fire’s caustic power in biblical physics. The tradition is summarized in a passage from Origen’s De principiis, which gathers several biblical locutions denoting the burning power of all fire, even when the language is stretched to include intelligible or divine fire.

²⁴ On Heraclitus’ theory of exhalations see Diogenes Laertius, Vitae IX.9 (=22 A 1 (9) DK); Kirk, Raven, and Schofield (1983), 200–2. On its Stoic echoes see SVF II.446, 572, 612, 658. The Middle Platonic source I am referring to is Atticus, fr. 6.12–18, who ascribed to Plato the view that celestial bodies are subject to ‘processes of material loss and accretion’. See the comments of Kalligas (2014), 258–9; Wilberding (2006), 158–60, 218–19, both with references. ²⁵ See Enn. II.1.3.23–30, II.1.4, and II.1.7.33–43, with the comments of Kalligas (2014) and Wilberding (2006) ad loc. ²⁶ See Hex. III.5 on the general principle of fire consuming water and III.7 on the application of the general principle in the supralunary (theory of exhalations). ²⁷ See In Hex. 28 GNO 41.12–15 reporting on the general principle of fire’s consuming nature. This is the view of Basil, as Gregory remarks in the next line, and it is also Gregory’s view, see Risch (1999), 198 n.247. The rest of the Apology up to §63 explains in detail how the supralunary fire constantly consumes the moisture of the exhalations from the sublunary. §28 (GNO 41.15–42.6) introduces a seeming divergence from Basil’s doctrine (cf. 29 GNO 42.7 hupenechtheisan antithesin: ‘implied opposition’), which was taken in secondary literature as introducing a real divergence from Basil’s doctrine, see Robbins (1912), 49 n.4, 55; Corsini (1957), 96–101; DeMarco (2013), 345–52 and (2017), 83–4; O’Brien (2015), 10–11, 12–13. This reading of the Apology rests on a profound misunderstanding of Gregory’s skopos as meticulously shown by Risch (1999), 7–8, 198–9 n.251. The gist of the Apology lies elsewhere. Basil had already remarked in Hex. III.4–6, though not further explained, that the consumption of water by fire should not be understood in the sense of a complete annihilation (ekleipsei) of one element by the other, otherwise the theory of the elements would explain not the conservation but the dissolution (dialusin) of the universe. Basil’s doctrine is reprised by Ambrose, Exam. II.3.12–14, with no further substantial advancement. It fell upon Gregory to explain how fire could consume water without the one element annihilating the other. Gregory’s laborious answer results in the formulation of the law of mass conservation from within hexaemeral physics (§§29–62). The law of conservation was already known in Greek physics, see Sambursky (1960), 7–8, 107–8; Long/ Sedley 4 with comments ad loc. (pp. 25–7). It was based, however, on the axiom that ‘nothing comes from nothing’. Gregory undertook the valiant effort to prove that the law was defensible from within the scriptural framework of creatio ex nihilo. This is the reason why the idealist theory of matter is so important for the hexaemeral exegesis: if the ingredients of mass (i.e. weight, density, extensionality, etc.) are qualities, and hence immaterial objects (‘pure concepts’), they pre-exist and outlast material change. The combination of the ingredients may change, and with it the distribution of mass in the universe. But the total sum of the ingredients remains unchanged, which means that the total mass of the universe remains constant. Since Gregory derives the idealist theory of matter from Basil too (see Hex. I.8, II.3, and my discussion in Chapter 2), there is no substantial divergence between Basil’s and Gregory’s physics.

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For the divine word calls God a fire, when it says, ‘Our God is a consuming fire’ [Deut. 4:24, 9:3; Heb. 12:29]. And concerning the substance of angels, it says as follows, ‘Who makes his angels spirits and his ministers burning fire’ [Ps. 104:4; Heb. 1:7], and in another place, ‘The angel of the Lord appeared in a flame of fire in the bush’ [Exod. 3:2]. We have, moreover, received a command to be ‘aglow with the Spirit’ [Rom. 12:11], by which without doubt the Word of God is shown to be fiery and hot. The prophet Jeremiah also hears from him who gave him the oracles, ‘Behold I have given my words into your mouth as a fire’ [Jer. 5:14]. As God therefore ‘is fire’, and the angels ‘a flame of fire’, and the saints are all ‘aglow with the Spirit’, so, on the contrary, those who have fallen away from the love of God are undoubtedly said to have cooled in their love for him and to have become cold. (DP II.8.3 tr. Behr)

The contrast with the Plotinian physics of fire is striking. For Origen, even the purest kind of fire burns. For Plotinus, the higher a fire is situated in the spheres of the universe the purer it is and the less it burns. Plotinus seems here to articulate a general premise of Greek thought, regardless of the particular details of the celestial physics of each school. The principle can be traced at least back to Theophrastus, who in his special treatise De igne reports it as self-evident. The De igne begins with the fundamental observation that all fire needs a material substrate to burn for its subsistence. The question that follows is what happens in the supralunary. Given that the stars appear to be fire-like, but their activity does not appear to burn, can we still say that they are truly made out of fire? In short, everything that is burning (pan kaiomenon) is, in a sense, in generation, comparable with motion, for which reason it somehow is destroyed as it is created, and with the exhaustion of the fuel (to kauston), it itself is done away with. The ancients were referring to this when they said that fire always seeks nourishment (trophēn aei zētei to pur), being unable to persist without fuel (aneu tēs hulēs). Hence it seems foolish to speak of fire as a first substance and original element if it cannot exist without fuel (chōris hulēs). For in that case it is not elemental nor prior to the substrate (hupokeimenou) and the fuel (hulēs), unless there is some such substance (toiautē phusis) in the first heavenly sphere itself (en autēi tēi prōtēi sphairai) which is pure (katharan), unmixed heat (amikton thermotēta). In that case it would no longer burn (ouk an eti kaioi). But burning is the essence of fire (puros), unless indeed there are several different kinds of fire, one pure and unmixed (kathara kai amiktos), an element, the other located in the earth’s sphere, mixed (memigmenē), and always in generation. (De igne 3–4 tr. Coutant)

We can see in this passage the premise that prompted Plotinus to theorize the unmixed fire of the stars as qualitatively different from sublunary fire: if it does not

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feed, it does not burn. And since celestial fire does not behave like sublunary fire, he preferred to name it differently.²⁸ It is a pure, though still corporeal, ‘light’. It is the same logic that prompted Aristotle to abandon the talk of heavenly fire and speak instead of a fifth element: if what is up there does not behave like fire at all, then it is not fire and should not be called that.²⁹ It is unclear where exactly the Stoic sources stand in that debate.³⁰ Some sources adopt a more Heraclitean tone and claim that celestial fire feeds and burns.³¹ Other sources suggest that it behaves like Aristotle’s fifth element or Plotinus’ pure light.³² The divergence within the school is reflected in how each tendency theorized the fire of the conflagration. The line attributed to Cleanthes spoke of ‘flame’ (phloga), which was the term for a consuming and burning fire.³³ The line attributed to Chrysippus spoke of ‘light’ (augēn), suggesting that it no longer consumes nor burns.³⁴ In this context, the hexaemeral authors sided, against the tide, with the

²⁸ To be absolutely clear, Plotinus excludes only the caustic effect from celestial fire. He does accept that celestial fire generates heat, which enables him to regard it still as a species of fire. But the heat in question is of a different kind. Plotinus speaks of ‘a gentle warmth’ (Enn. II.1.7.25–6 thermon de prosēnōs monon), which, as Wilberding (2006), 216–17, rightly argues, is Plotinus’ terminology for ‘vital heat’. The difference between caustic and vital heat is that the former converts fuel into fire while the latter produces growth and generation, see Wilberding (2006), ad loc., with references to which the above quoted passage from Theophrastus must be added. The sources mentioned anticipate or build upon Theophrastus’ explanation (or a similar one). ²⁹ Contrary to Plotinus, Aristotle thought that the substance of the stars does not generate any heat at all, see Cael. II.7; Meteor. I.3. For his explanation of vital heat see Gen. anim. II.3: it is a property of pneuma which is analogous but not identical to the substance of the stars. Since Aristotle’s fifth element lacks the most basic characteristic of fire (i.e. heat), it cannot be classified under ‘fire’ anymore. ³⁰ The ambivalence of the available sources has been pointed out by Boyancé (1936), 65–78, and Hahm (1978), 65–9. ³¹ See Aëtius, Plac. II.17.2 and 23.5; SVF 2.446 (= Galen, Tremor. VII.617), 572 (= Cleomides, Caelest. I.8.79–99 = Posidonius, fr.289 Theiler), 612 (Philo, Aet. 86). The principle is expressed in Plutarch, Quaest. conv. VII.4 (703A): fire is nourished by itself (kinoumenon te kai trephomenon di’ hautou). This does not mean that fire nourishes fire but rather that fire seeks its fuel by its very nature, see Cicero, DND II.23 (cietur et agitur motu suo). See, however, my remarks in the footnote below on the fire of conflagration (n. 34). ³² See Lapidge (1973), 255–7: Stoic celestial fire exhibiting the characteristics of Aristotle’s fifth element, causing ambiguity as to the differences between Stoic and Aristotelian ‘aether’. On Plotinian celestial fire see Enn. II.1: its natural motion is circular; it does not burn; it is quasi-material. These are the common features of Stoic ‘aether’ (in at least one version) and Aristotle’s fifth element. ³³ See Philo, Aet. 90 (= Long/Sedley 46.M). A similar tradition is also attributed to Zeno apud Alexander Lycopolis 19.2–4 (= Long/Sedley 46.I). ³⁴ See Philo, Aet. 90 (= Long/Sedley 46.M). Long/Sedley 46.M, in their comments (p. 278), interpret Chrysippus’ ‘light’ as ‘pure fire’ and argue for ‘the essential unity of all fire’ in Stoic physics (46.D, vol. 2, p. 273). This would be possible if pure fire and pure light are both aether in varying degrees of density: the compression of aether kindles fire; the dispersion of aether in space gives the transparent (and, as such, invisible) light of heaven, as Plutarch in Facie (928c = SVF II.668) tells us. If this is the general principle, then ‘flame’ (Cleanthes) and ‘light’ (Chrysippus) denote simply two different states of condensation of pure fire. Flame, which is consuming, is the last and the first state of elemental fire. Light is the state in which the dispersed aether rests tranquil in itself, until it begins condensing again. Perhaps this is what is meant under the allegorical expression that ‘Zeus [sc. flame] withdraws into providence [sc. its pre-cosmic state], whereupon both, having come together, continue to occupy the single substance of aether’, see Long/Sedley 28.O.4 and 46.O. In this pre-cosmic state, aether would not need to consume anything. The need for consummation appears with the change of aetherial light into

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Heraclitean tradition.³⁵ There is no reason to explain this adherence other than the biblical language of fire. As we saw, Origen affirms that pure fire burns, hence is truly fire. We find the exact same doctrine in Philo, who asserts the consuming nature of all fire³⁶ and follows the Stoic view that celestial fire is burning fire.³⁷ The reason why we do not feel its caustic effects is not intrinsic but extrinsic: it is the cool-down effect of the interposed air.³⁸ Thus, all biblical language of fire entails a burning material and its caustic effects, even when the language is stretched to include pure (corporeal) light or analogically applied to God.³⁹ The Cappadocians appear hermeneutically committed to the Philonic-Origenian twist on celestial physics, while maintaining a distinctively Neoplatonic terminology. Basil, who first speaks of the celestial ‘immaterial light’, adopts the Philonic view of the sun being a most burning fire (phlogodestatos).⁴⁰ He moreover argues that it is only logically (though not empirically) possible to separate the illuminating from the caustic power of fire. That is at least what the thought experiment from miracles (burning bush) and other possible worlds (eschatology) suggests: It is inconceivable for you to separate the burning power (kaustikēn dunamin) of fire from its brightness (lamprotēs); yet God, wishing to turn his servant back by an incredible spectacle, placed a fire in a bush, which was active only by its brightness (lamprotētos) and had its power of burning (tēn tou kaiein dunamin) inactive. This, too, the psalmist testifies when he says: ‘The voice of the Lord dividing the flame of fire’. Whence also in the requital for the actions of our lives a certain saying teaches us in cipher (logos tis hēmas en aporrētōi paideuei) that flame through compression with the contemporaneous emergence of air and so on. If that is a plausible reading of the fragments, see e.g. Long/Sedley 46.G.2 and 47.A, the essential unity of all fire is indeed preserved in the Stoic system, while all elemental—i.e. intra-cosmic—fire has a consuming nature. ³⁵ This does not mean that I classify the Cappadocian physics of fire as ‘Stoic’ because, if my analysis is correct, the Cappadocians follow the elemental theory of Aristotle in the sublunary and the theory of aether of the Epinomis in the supralunary, see Chapter 2, section 2.3.1. With these caveats, the Cappadocians share with the Stoics the view that celestial fire is a consuming ‘flame’ (phlox). ³⁶ On the consuming nature of fire see Abr. 140; Somn. II.212. On the terminology see Aet. 86: the burning species of fire is called ‘flame’ (phlox). ³⁷ Celestial fire is phlox, see Cher. 25–6; Deus 78. ³⁸ See Deus 79. ³⁹ On the burning nature of all biblical fire, whether archetypical or derivative, divine, angelic and celestial, see Philo, Decal. 49; Clement, Ecl. 26.3; Origen, DP. I.1; further Stead (1994), 142, all commenting on the scriptural locus that ‘God is a consuming fire’. Thus, the most basic tenet of the early Christian physics of light was shaped by the ‘Alexandrian’ interpretation of Deut. 4.24 and remained constant in all subsequent scriptural exegesis, see e.g. Didymus, Comm. Gen. 233.12–234.4 ad Gen. 15:17 (burning celestial and divine fire); Ambrose, Exam. II.3.13–14 (burning celestial aether); Severian, Cosmog. I.4 PG 56:434 and IV.6 PG 56:464 (angels as burning fire). We can now clarify the terminology: the scriptural language of light exhibits the same equivocity (‘homonymy’) as the language of Plotinus, denoting here pure (celestial) fire (i.e. a fire that is ‘light’) and there any fire’s luminous power (i.e. a fire that has light). But while for Plotinus celestial fire is not burning flame, for the scriptural exegetes it is. Celestial flame, however, exhibits different degrees of causticity and luminosity than sublunary flame due to the finer material that it burns, see the following section. Thus, in both Christian and Plotinian physics celestial fire radiates not the destructive but the vivifying kind of heat, the so-called ‘vital heat’, see for a clear exposition of the Christian doctrine Clement, Ecl. 26.3–5. ⁴⁰ Hex. VI.8 GCS 102.9. See also III.7, VI.10.

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the nature of fire will be divided, and the light (phōs) will be assigned for the pleasure of the just, but the pain of burning (to tēs kauseōs odunēron) for those punished. (Hex. VI.3 GCS 92.1–9 tr. Way, amended)

Gregory, who also speaks of supralunary ‘immaterial light’, follows in the footsteps of Origen. During the exegesis of day two he repeats the celebrated imagery of God as a ‘consuming fire’, applying it to the divinity.⁴¹ Like Origen in the De principiis, he finds no reason for separating the two necessary features of fire, brilliancy and causticity, from one another, not even when the language of ‘fire’ is stretched to include purely immaterial states like the light of the Holy Spirit.⁴² Gregory clearly feels the weight of a long interpretative tradition supporting his exegesis. He thus boldly suggests that the Spirit of God mentioned in Gen. 1:2a stands to the spiritual waters in the same relation as celestial fire stands to the moist exhalations of the sublunary world. The implied analogy drawn from the physics of the hydrological cycle suggests, to the intelligent reader, that the consummation of the soul by divine fire brings not destruction but transformation and regeneration. All this goes beyond the premises warranted by Neoplatonic physics, which does not theorize celestial fire as having a consuming activity.

3.1.4 Hexaemeral Physics The hermeneutical twist of the hexaemeral authors has further consequences. It leads to a more parsimonious account of celestial physics requiring no deviation from the theory of the four elements, e.g. through the introduction of a fifth element or the stipulation of a sui generis species of celestial fire. It also has the great merit of extending the principles of sublunary fire to the supralunary. The latter extension allows us to learn more about how Gregory would explain the different physical characteristics of various kinds of light. For the relevant doctrine we need to turn again to the De igne. Theophrastus there explores further the relation between the fuel and the light of a particular species of fire. Based on the principle of purity, Theophrastus argues for a comprehensive chain of causation that binds fuel, fire, and light together. This creates a direct, causal link between the qualities of the fuel involved in the reaction and the qualities of the light produced. In other words, the accidental physical characteristics of a fire’s light (brilliancy, purity, and radiant intensity) are directly dependent on the degree and purity of moisture contained in the inflammable material that sustains the fire’s activity. The purer and more unmixed (hence rarer, lighter, etc.) the fuel

⁴¹ See In Hex. 19 GNO 32.7–10.

⁴² See In Hex. 19 GNO 31.15–19.

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is, the greater the brilliancy of the light it gives. To put it in more Neoplatonic terminology, the more ‘immaterial’ the fuel, the more ‘immaterial’ the light. Since the inflammable and combustible substances are numerous and various, their qualities are different, and one cannot do what another can: for example, charcoals (anthrax) cannot give light (phōtizein) as flame (phlox) can, nor does a flame give the same light as a lamp (luchnos), nor does the lamp give the same when dying down as when it is flaring up. The purer the flame (hosōi dē katharōtera), the clearer it burns (tosoutōi mallon), since it contains no earthy (geōdes) or liquid (hudatōdes) matter which may block it and from which smoke (kapnos) and exhalation (anathumiasis) may arise. That is why the flame (phlox) from green wood is redder than that from dry wood; it contains more moisture through which the light shines and gets its colour (chroian), as happens with the sun when the air is dense (pachus). Charcoal (anthrax) produces only a little flame (phloga) because it does not contain much moisture (hugrotēta) to be volatilized (exaeroumenēn). When the moisture is being burned (puroumenē), we have flame (phlox). (De igne 30–1 tr. Coutant)

We can now begin to see the full picture of Gregory’s physics of light in the Apology. It is a synthesis of Stoic physics (celestial flame) with Aristotelian principles (theory of the four elements), embedded in a premodern cosmological framework (varying degrees of materiality from the centre to the limits of the universe), expressed in Neoplatonic terminology (‘immateriality of light’), carrying forward the Philonic-Origenian legacy of hexaemeral hermeneutics in the context of fourth-century post-Nicaean orthodoxy. The fundamental tenet of Gregory’s physics of light is that all accidental attributes of light, whether in the sub- or the supralunary, are the direct consequence of the quality of the fuel that light’s productive fire uses to sustain itself. What the fuel is in the case of celestial fire, we have already seen. It is the exhalations of the vaporized water coming from the earth. Thus, the brightness of the stars is the direct correlation of the subtlety of the material that sustains it, namely the purest kind of moisture carried to the supralunary by the exhalations of vaporized water. We can even go a step further and supply the final details of the picture that Gregory sketches but never fully draws. We may deduce that once the moist and dry exhalations reach the hot and dry aether of the supralunary a process of separation begins under the effect of aether’s heat. The moisture that is gradually released travels through the vast regions of space under the motive power of aether’s heat to the planets and the stars to be consumed. The dry part that is left behind falls down on earth under the power of gravity in the form of dust-like particles (konis).⁴³ That means that ⁴³ See Gregory, In Hex. §§38–40, 46–8  Basil, Hex. III.7 GCS 49.17–50.16 (including the same example of the burning lantern).

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the farther a heavenly body is positioned in the sphere of the universe, the more complete the process of separation between the moist and dry element and the purer the quality of its fuel will be. That further suggests that the supralunary is not an entirely homogeneous space, as sometimes assumed, but exhibits its own varying degrees of heat and moisture. The latter insight brings us back to the old suggestion of Chrysippus about the variegated purity of the aether of the supralunary, revamped in a biblical physical universe. The result is a fascinating relation of dependence between natural place, materiality, and luminosity: the higher a fiery body is positioned in the sphere of the universe, the finer (i.e. purely moist) the physical characteristics of the material it consumes, and the finer (i.e. purely bright) the colour, irradiance, and clarity of the light it produces.⁴⁴

3.1.5 Hexaemeral Hermeneutics We have come far with Gregory’s physics of light. Let us now go a bit further and consider its exegetical consequences. The connecting thread of Gregory’s physical world is the law of universal mass conservation. The world is a continuum in which all elements interact with each other and there is no part of the world that is separated from the rest. This unity is the outcome of the constant interaction of celestial fire, which reigns in the supralunary, with the hydrological cycle, which governs the laws of change in the sublunary. The hydrological cycle requires water, fire, and air (for water to evaporate) and earth (for water to return to a basin). Celestial fire again requires the hydrological cycle (which sustains it). Thus, the existence and sustenance of heavenly bodies requires the synergy of the four elements. In Gregory’s hexaemeral exegesis, the creation of the four elements is explained through a process of gradual separation of one element from the others over a period of three cosmic days: fire first (§§10–15), then aether and air (§§18–25), then water and earth (§§26–63). That means that the exegesis of the fourth day of creation (§§64–73) continues the sequence of events that took place on days one to three. Not because Moses says so, but because this is the natural order of things, the akolouthia of nature (§74). Moses simply wrote down this akolouthia in the form of a hexaemeral narrative. It is this akolouthia, the laws of physics, that the reader is called to retrieve by contemplating nature through the mirror of Scripture. If the contemplation is successful, the reader will discern that there is a logos guiding the heavens (§69 hoti pantōs esti tis logos) and that this ⁴⁴ The synthesis of the various theories is conditioned by a layered theory of harmonization and results in a distinctive (from other schools) and coherent theory of light, see the rest of this chapter and Appendix B. This speaks for originality induced by certain hermeneutical commitments. The result is not a cocktail of different theories accommodated to serve scriptural exegesis but an altogether new theory. This was necessary if the original plan of defending the possibility of hexaemeral physics against erudite readers of Scripture like Celsus and Galen was ever going to succeed.

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logos manifests through the chain of natural events as material causality (§71 tēs tōn ontōn ktiseōs akolouthian tina). What the exact structure of the celestial logos is remains, however, beyond the ability of the reader to grasp. We may understand the laws of celestial physics—the physics of light par excellence: the immeasurable variety of luminous substances circulating the heavens, their physical properties, the factors of their luminosity, their relation of dependence upon the other elements—but we will never comprehend why it is these laws and not others that reign in nature, why it is this logos and not another that defines the individual structure of a star, the physical properties of its light, or the current configuration of the elemental distribution in the world (§70 mē dunamenos exeurein ton logon, pōs . . . ; §71 ton logon . . . idein . . . adunatei). Bearing this in mind, we may finally understand the inner logic of Scripture, the akolouthia of the creation narrative, why there needed to be an interval of three days between the light of the first days and the heavenly bodies that exhibit it in the fourth. The interval was necessary for the four elements to appear and start the cycle of their inter-transformations, without which there could be no fire and hence no light in the universe. And since there can be no light without fire and no fire without fuel, the four days cannot denote intervals of time, but only logical steps necessary in reconstructing the akolouthia of nature. Seen from a cosmic perspective, the four elements must always coexist and constantly interact with each other. If this is a plausible interpretation of the Apology, it reveals something of the beauty and erudition of Gregory’s hexaemeral exegesis. Gregory is not interested in repeating Basil’s project but in explaining it. He avoids a second version of what we already know, namely of the encomium of light. Instead, he gives us the physics that explain the variety and beauty of light itself, and in so doing fulfils the very purpose of light’s encomium: to lead us through the contemplation of the heavens to the apprehension of the divine logos shaping and sustaining the world. But Gregory does not stop at that. His physics of light requires a hexaemeral exegesis that links the different stages of creation intrinsically with each other. The physics of light explains not only how light works but also why the special work of each day of creation cannot actually exist without the work that comes before and after. Gregory’s analysis of the four elements and the cycle of their mutual intertransformations reveals heavenly light to be the outcome of a global synergy, so that there is no feature or part of the world that does not contribute to the other, ‘for the world is continuous as a whole (suneches esti to pan en heautōi) and the whole (to holon) is made up by parts (ek merōn)’ (§48). Gregory’s hexaemeral exegesis tries to make sense of the world as a meaningful whole or there is no world at all. The contemplation of light helps us intuit that there can be but one act of creation, that the whole cosmos is created from the outset and nothing was left out from the very beginning. But we are feeble (§71 hē ptōcheia tēs phuseōs hēmōn) and cannot sustain this vision for long (§70 ho nous iliggiai). That is why Scripture narrates the cosmogenesis step by step (§71 kata tēn ektetheisan para tou

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nomothetou taxin), hexaemerally, training the mind (dia tinōn stochasmōn) to perceive gradually the divine logos guiding the All. Gregory’s contemplation leads us through the All by telling the story of light. A story of light worthy of a true hexaemeral exegete. So far, Gregory has told us the story of light from within (ad intra). He has shown us light’s substance (fire) and structure (a power of fire), its essential property (luminosity), how this property comes about (separation of fire from the other elements), how its accidental attributes are configured (particular brightness and radiant intensity as a function of fire’s purity), and how its activity is sustained (interaction of fire with the other elements). In other words, he has shown us the internal manifestation of the logos of light, how light’s innate logos becomes embodied as luminosity. It is now time to follow the other side of the story of light and see how light’s embodied logos manifests its luminosity out in the world (ad extra), causing things to become bright. The exteriorization process of the logos of light requires two things: a vehicle and a recipient. The former is the light ray, the latter the medium. I shall take them in order.

3.2 Going Ballistic: The Singularity of the Light Ray The Apology mentions the light ray (aktis) in several different contexts. The ray theory helps explain the magnitude of the sun (§32), the evaporation of surface water (§33), the infiltration of space with light (§48), the distance of the stars (§70), and the light of the moon (§70). The references explicitly presuppose some version of a ray theory.⁴⁵ But the systematic exposition of the theory itself and its details are left for the intelligent reader to figure out. That is what I here propose to do. In what follows, I shall attempt a systematic reconstruction of the ray theory underlying the Apology, pieced together from clues scattered here and there.

3.2.1 Rectilinearity The first feature of the light ray is that it is rectilinear. We learn this indirectly from Gregory’s disquisition on the magnitude of the sun, which is mathematically inferred from the conoid shape of the shadow of the earth.⁴⁶ The passage in the Apology is an abbreviated version of the astronomical theory expounded in the De hominis opificio, which runs as follows:

⁴⁵ Already intimated by Basil, see Hex. II.4, II.5, II.7, VI.3, VI.4, VI.8, VI.9, VI.11, VII.1. ⁴⁶ See In Hex. 32 GNO 45.15–20.

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For just as those skilled in astronomy tell us that the whole universe is full of light (phōtos katapleōn), and that darkness (skotos) is made to cast its shadow (aposkiazomenon) by the interposition of the body formed by the earth; and that this darkness is shut off from the rays of the sun (tēs hēliakēs aktinos), in the shape of a cone, according to the figure of the sphere-shaped body, and behind it; while the sun, exceeding the earth by a size many times as great as its own, enfolding it round about on all sides with its rays (pantachothen autēn tais aktisin en kuklōi periptussomenon), unites at the limit of the cone the concurrent streams of light (tas tou phōtos sumbolas); so that if (to suppose the case) any one had the power of passing beyond the measure to which the shadow extends, he would certainly find himself in light unbroken (mē diakoptomenōi) by darkness. (Hom. opif. XXI.3 tr. Wilson)

The passage does not explicitly say that the rays of the sun travel in straight lines. But this is clearly presupposed by the mathematics that explain the shape of the earth’s shadow. Gregory is interested neither in the astronomical theory as such nor in its mathematical proof. They are full of details that are superfluous for hexaemeral exegesis, as Basil had already remarked.⁴⁷ Basil’s statement is fully justified in view of his largely uneducated audience, and Gregory, who is addressing the learned, is not deviating from the basic principle by providing the basic outlines but not the detailed explanation of the theory. To the educated readership the astronomical theory was well known and the information missing easily accessible from multiple sources.⁴⁸ Calcidius, who is one of the possible sources available and who provides the astronomical theory and its mathematical proof in detail, also clarifies that the mathematical proof requires the light ray to be rectilinear: The rays of the luminescent celestial fires travel in straight lines (ignium lucem praebentium radii directi feruntur), shaping variously the shadows cast by the intervening bodies . . . Thus whenever the sphere radiating light has the greater magnitude and the illuminated one the smaller . . . the shape of the shadow will be conical. (In Tim. 89–90 tr. Magee)

The general principle is already expressed in the optical fragments attributed to Geminus: For every kind of light moves in straight lines.

(Schöne 24.2–3)

⁴⁷ See Hex. IX.1. ⁴⁸ For the astronomical theory see Aristotle, Meteor. I.8 (345b1–9); Posidonius, frs 9 and 19 EK; Cleomedes, Caelest. II.2.19–30 Todd; Plutarch, Facie 932e (59.20–2 Pohlenz); Pliny, Nat. hist. II.49–52; Alexander Aphrodisias, In Meteor. A.8 (38.8–13 Hayduck); Calcidius, In Tim. 90. For the mathematical proof see Aristarchus, Magnitud. 2; Cleomedes, Caelest. II.6.79–108 Todd; Calcidius, In Tim. 89–90.

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The rectilinearity of the ray is therefore an intrinsic feature of the ancient physics of light.⁴⁹

3.2.2 Light Mechanics The second feature of the light ray is that it exhibits mechanical properties. This is, again, an indirect inference, this time though derived from the presuppositions of Gregory’s theory of lunar illumination. Here is the relevant passage from the Apology: I mean the lunar body . . . whose nature is considered to be somehow median (mesē pōs phusis), participating equally in the absence and the presence of the power of light (tēs te alampous kai tēs phōtistikēs dunameōs kata to ison metechousa). The dense composition of its substance blunts its original glow (lampēdona), but due to the reflection of the sun’s rays (tōi de antiphōtismōi tēs hēliakēs aktinos) it is not entirely alienated from the production of light (phōtistikēs phuseōs). (In Hex. 70 GNO 77.9–13)

The passage clearly states that the light of the moon is the result of the combined action of the sun’s light with the moon’s composition. When the sun’s rays hit the surface of the moon the light is reflected (antiphōtismōi). The Apology does not say how exactly this reflection is justified. But we can supply the details if we allow for intertextual evidence from Gregory’s other works.⁵⁰ A look at Gregory’s corpus shows that the term antiphotismos of the Apology (70 GNO 77.12) accords perfectly with the term anaklasis of the An. et res. (32C): they both denote the reflection of the light of the sun by the moon. If so, we can fill in the details by collating the information we are given in both texts. The Apology informs us that the fiery substance of the moon is so weak that its luminosity remains practically ineffective (alampous).⁵¹ The An. et res. picks up the thread and explains that even ⁴⁹ See explicitly, in a Stoic framework, Marcus Aurelius, Meditat. VIII.57.5. The testimony is important because in the Stoic system the ray, like everything else, has bodily existence. Rectilinearity is therefore a feature of the ray not only as a mathematical abstraction, as the optical references might suggest, but also as a physical reality. Rectilinearity is a concomitant of the physicality of light. ⁵⁰ See An. et res. PG 46:32B–33B; Trid. spat. GNO 297.6–298.3. Risch (1999), 226–7, objects to a combined reading of these texts, arguing that Gregory employs two different astronomical models. The Apology adopts the rather Posidonian model of mixture (sugkrasis) of the light of the sun with the inherent but latent luminosity of the moon, a model which is deemed incompatible with the theory of reflection, see Cleomides, Caelest. II.4, esp. lines 21–32. The An. et res., on the other hand, clearly adopts the reflection theory (anaklasis). Risch explains the inconsistency away by claiming that Gregory is ‘completely indifferent’ (völlig unbekümmert) to the physics of the light ray that he uses here and there. As I show, Gregory is not inconsistent and a combined reading is possible. ⁵¹ Of the two theories reported by Plutarch on the nature of the moon’s glow, the one attributed to the Stoics and the other to the mathematicians, Gregory follows the Stoic view, according to which the

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if the moon has no power to illuminate by itself (apheggē kata tēn idian phusin) it still retains something of the inherent luminosity of its fiery substance: it is the glittering colour of its surface (stilbontos), which bestows the properties of a mirror to the moon’s surface (hōs epi tōn katoptrōn). This mirror-like property allows for the reflection of the sunrays. We can derive the same doctrine from another text, the De tridui spatio, which describes the moonlight as the combined effect of the sun’s rays with the moon’s glow.⁵² All this is textual evidence enough that the rectilinear ray is a physical entity with mechanical properties. It creates a physical impact on the surfaces that it strikes, being forced to rebound on dense surfaces with mirror-like (i.e. glittering) properties or to penetrate the surfaces of non-opaque bodies, according to the degree of their density.⁵³ This means that the light ray has a physical reality, obeying the laws of general dynamics, and is not a mere mathematical abstraction.⁵⁴

3.2.3 Light Kinetics Does the light ray travel? And if so, how fast? Gregory is not explicit on this point and the information we get from the Apology is unclear. During the exegesis of the first day we are told that elemental fire is swift (tachei) and agile (eukinētōi), having a sharp (oxeian), upward (anōpherē) and ever-mobile (aeikinēton) nature (§§12, 14). When fire was separated from the other elements it leaped up (proexēlato), shot out like an arrow (ektoxeuthen kathaper ti belos), to the high and light region by virtue of its natural motion. It traversed the

moon is ‘a fire turbid and dreggish’ (pur tholeron kai trugōdes), Facie 928d, 933d, 935b. As Smith nicely puts it, according to this view ‘the moon is endowed with its own faint luminousness that becomes visible in the absence of occluding light’; Smith (1996), 109 n.109. ⁵² Trid. spat. 297.14–15: plērōtheisan tais augais tēs hēmeras tas par’ heautēs lampēdonas summixai. I am here reading summixai in the sense of ‘joining forces’; ‘be formed by combination’; ‘happening together’ rather than in the stronger sense of ‘mix together’ or ‘commingle’. But even the stronger reading is possible, in which case the doctrine at hand would imply a model of sugkrasis. The sugkrasis (blending) model does not have to be incompatible with the anaklasis (reflection) model, as Risch (1999), 226–7, suggests. Kidd (1988), 475–6 (comm. on fr. 123), has argued that ‘there may have been different variations of the theories. For example, Macrobius . . . seems to combine a reflection theory with a Posidonian semipenetration theory of solar light.’ I would be very willing to accept that Gregory’s theory employs such a mixed model. My difference with Risch would then be whether the anaklasis and the sugkrasis models are incompatible with each other, as e.g. Cleomedes thinks, or whether they are compatible, as Macrobius suggests. Having said that, the difference is of little importance for the argument I am making here. Whether reflected on the moon’s surface (anaklasis model) or penetrating the moon’s surface (sugkrasis model), the light ray clearly has mechanical properties. ⁵³ In the sugkrasis model the moon is permeated by the light rays but not totally. Cleomedes, Caelest. II.4.34–41 uses the analogy of a sponge absorbing water. ⁵⁴ On the laws of projectile motion applied to the light ray in physical optics, see Ptolemy, Optics II.17–18, 20 and III.21–2, with the comments of Smith (1996), 23, 37, 42–3 and ad loc.

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perceptible universe just like thought (isa noēmati) . . . (In Hex. 14 GNO 25.1–4)

The passage attributes a special mechanical status to elemental fire. It has a natural projectile motion moving at an enormously high speed. The comparison with thought does not mean that fire is an intelligible entity, but that it moves with an extreme velocity, like the speed of thought, i.e. occupies space instantaneously. There is a resemblance, in the sense of a loose analogy, with the speed of light in contemporary relativity theory, as the limit of spatio-temporal motion. It is then no surprise when the Apology tells us that once the fire leaped forth, everything was immediately (euthus) surrounded by light. (In Hex. 10 GNO 20.17)

How are we to understand this euthus: is it that light flows out from fire at an enormously high speed, like the speed of fire, or is it because light is a static extension of fire, appearing and disappearing together with fire?⁵⁵ The problem

⁵⁵ The question was raised by Christopher Stead (1994b). The two alternatives that Stead examined were an ‘outflowing’ model of light as effluence of flame (for which see below) and a ‘static’ model of light as the extension of its source, ‘as some Stoics had held’ (p. 727). The Stoic source that Stead had in mind was Marcus Aurelius, Meditat. VIII.57, a text first noticed by Dölger (1929), 280. We there find two mutually exclusive models of the ray theory, the ‘Stoic’ model of light as ‘stretched air’ (tasis), describing the ray as a pouring forth (chusis) or diffusion (diachusis) of brightness in ambient space; and the ‘Platonic’ model of ‘emanation’ (aporroē), describing the ray as an outpouring or effusion (ekchusis) of brightness in ambient space. The Stoic model identifies the motion of the ray (chusis) with the tension or stretching of the air (tasis) and the ray (aktines) with the extension, i.e. transmission, of brightness (augai) in the air, through the telling paretymology of ray (ak-tis, ak-tinos) from ex-tension (ek-teinō, ek-tasis). Clearly, Marcus Aurelius develops a version of the Stoic theory of light as stretched air, also known through the celebrated simile of the ‘walking stick’, see Lindberg (1986), 9–11; and now Betancourt (2018), 52–63. Stead (1994a), 141, claims that in the Stoic theory ‘the ray of light is conceived as a static extension of the luminous body’, citing also Tertullian, Apol. 21. He thus opposes the Platonic theory of light as a dynamic emanation from fire with the Stoic theory of light as a static extension of fire. The juxtaposition is indeed warranted by the text, not however because of the lack of dynamism of the Stoic model. Marcus Aurelius describes the propagation of light with dynamic language: katakechustai, chusis, ekteinesthai, parapempon all denote the motion of the ray in space. At the same time, Marcus Aurelius uses static language to describe the illumination of space: once stretched, the ray remains still (estē, istasthai) and illuminates (epilampein) that which receives it (to dechomenon). Strictly speaking, then, this is not a static model of light but a static theory of illumination. The comparison with Tertullian leaves no doubt: Apol. 21 adopts the Stoic theory of the ray as an extension of the sun (extenditur), but it also makes clear that the ray proceeds from its source as a dynamic phenomenon: prolatum, porrigitur, profectum, excessit, delapsus all denote motion and a pouring forth. The Stoic version of the ray theory is not static. In what follows, I distinguish between the emission of light (‘radiant light’) and the illumination of space (‘ambient light’). As regards light kinetics, the crucial question is whether the emission of light is only logically prior to the transmission of light in space (allowing no interval of time between the two) or also temporally prior (accepting an interval of time, no matter how infinitesimally small), see section 3.2.4 below. As regards the theory of illumination, the key question is whether the transmission of light affects a real change in space or not, see section 3.3.2 below.

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is that when we are dealing with extreme velocity, at the verge of the conceivable, there is no difference that can be attested by the senses between an instantaneous motion (requiring an interval of time conceivable only in thought) and a simultaneous presence (requiring no interval of time whatsoever).⁵⁶ Does the transmission of light in space mean ‘getting there’ or does it mean ‘being already there’? The ‘immediacy’ of light could mean both. The euthus alone does not suffice to clarify its meaning, and we must once more rely on intra- and intertextual evidence. On two occasions Gregory uses verbs that denote locomotion in relation to the light ray. He speaks of the light ray ‘streaming in’ (eischetheisa) a dark space (§48); and he assumes that the light ray weakens in power the more distance it covers (§70). But the illumination of a dark space does not necessitate a moving ray, only the positioning of a fire at the right distance and angle for its rays to fill a space. And the weakening effect of a light ray away from the source could be due to other reasons, like the dispersion of light rays in space, the intensity of the fiery source, the quality of fuel, or even the resistance from the intervening field. Here too terminology alone does not help.⁵⁷ There is, however, another hint that may be useful, depending on how much one wants to draw lines of contact between the theory of light and the theory of colour. In a brief passage explaining why the earth was originally invisible according to Gen. 1:2a, Gregory gives us a brief definition of colour: it is ‘like some sort of effluence of the surface shape’ (hoion tis aporroē tou kata tēn epiphaneian schēmatos).⁵⁸ The language of aporroē (effluence or emanation) is distinctively Empedoclean and famously reprised by Plato.⁵⁹ The definition of colour in relation to surface has reportedly Pythagorean echoes.⁶⁰ If that is the contextual framework of Gregory’s theory of colours and if Gregory thinks of colour and light in similar terms—a plausible assumption⁶¹—we may further infer that Gregory is broadly thinking in terms of some kind of Empedoclean-Timaean

⁵⁶ The fact that extreme velocities exceed the observational capacity of the human eye, generating the optical illusion of immobility, was already known in antiquity, see Ptolemy, Optics II.82 and 98. In such cases, motion had to be cognitively inferred. ⁵⁷ In other words, Gregory’s language of eischusis could fit both alternative models described by Marcus Aurelius in Meditat. VIII.57. It is impossible to tell, based only on terminology, whether Gregory’s eischusis refers to the (dia-)chusis or the ekchusis model. ⁵⁸ See In Hex. 16 GNO 28.1–3. ⁵⁹ For Empedocles see Plato, Meno 76d4–5; Aristotle, De an. II.7 (418b15); Theophrastus, Sens. 7.10–11; Aëtius, Plac. IV.14 (in the context of catoptrics); Kirk, Raven, and Schofield (1983), 309–10; Ierodiakonou (2005a); Rudolph (2016), 44–8. For Plato’s further development of the theory see Tim. 67c6–7; Ierodiakonou (2005b). ⁶⁰ See Aristotle, De sensu 3 (439a30–1); Aëtius, Plac. I.15.2. According to Aristotle’s report, the Pythagoreans did not seem to distinguish between ‘surface’ (epiphaneia) and ‘colour’ (chroia), see Burkert (1972), 57 n.26, 68 n.96, 236 n.93, 247. ⁶¹ See e.g. Tim. 45b–e, 58c, and 67c–68d: light and colours belong to the same species of fire as effluences of flame commensurate with the visual ray; Ptolemy, Optics II.23: light and colours belong to the same genus.

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theory of light as effluence of flame.⁶² There are two pieces of evidence that support this suggestion. In the middle of a dialectical argument in support of Basil’s physics of light, we are told that the ray conveys thermal power to the surface that it hits, making the water evaporate from the earth (§33). The language suggests that the ray is not the mere conveyor of the thermal power of fire but that it affects the surface with its own heat (tōi thermōi tēs aktinos). This is possible only if light is a species of fire and therefore shares in fire’s brightness and heat. If that is the theoretical terrain we find ourselves in, then Gregory’s light is very close to the Timaean theory of light as the second species of fire.⁶³ As such, it shares in all of fire’s physical characteristics—agility, swiftness, and sharpness included— but in the most refined way possible.⁶⁴ If so, it may indeed cover huge distances in space instantaneously.⁶⁵ For the second piece of evidence that light is an outflowing current and not a static extension of flame we have to look at Basil’s explanation of celestial illumination. In his exegesis of day four, Basil gives the example of a lantern (luchnos) to illustrate how the heavenly bodies work as physical systems of fire burning and emitting light and heat. In fact, at that time [sc. day one] the very nature of light (tou phōtos hē phusis) was introduced, but now this solar body (to hēliakon touto sōma) has been made ready to be a vehicle (ochēma) for that primordial light (tōi prōtogonōi phōti). Just as fire (pur) is different from a lantern (luchnos), the one having the power to give light (tēn tou phōtizein dunamin echon), and the other made to show the way (paraphainein) to those who need it, so also in this case the luminaries (phōstēres) have been prepared as a vehicle (ochēma) for that pure, clear, and immaterial light (tōi katharōtatōi ekeinōi kai eilikrinei kai aülōi phōti). (Hex. VI.2 GCS 91.1–6 tr. Way, amended)

⁶² It should be noted that in the tradition Empedocles was considered a Pythagorean and the Timaeus was interpreted as a Pythagorean document, see Burkert (1972), 53–66, 84–5 (on the Timaeus), and 111, 289–90, 292–3, 454 (on Empedocles). It should also be noted that in his critique of the ray theory, Aristotle treats the Empedoclean and the Timaean theory of vision as one theory, see De an. II.7 (418b14–16; 20–6) and De sensu 2 (437b10–14; 438a25–7). It is no surprise then that Gregory feels justified in assuming a common theoretical framework, from which he draws. That Gregory works with Aristotle’s classification in mind is clear from his introductory phrase on the theory of colour, which is a verbatim quotation from the De an. II.7 (418a.29), identifying colour as the special sensible of vision (to gar horaton chrōma esti). He immediately changes, however, to the Empedoclean-Timaean theory of aporroē in conjunction with the Pythagorean theory of colour– surface. ⁶³ See Tim. 58c5–d1 and the discussion that follows in this section. ⁶⁴ See Empedocles, fr. B84 DK (= 88 Wright) tanaōteron; Plato, Tim. 45c katharon; Aristotle, Top. 134b28–34 leptomeresteron. ⁶⁵ As also implied, a contrario, by Aristotle’s critique of the Empedoclean and Timaean ray theory, see De an. II.7 (418b20–6); cf. also Sens. 3 (446a20–b2). See also the note at the end of section 3.2.4.

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The example is meant to illustrate the difference between fire as such, whose natural capacity is to illuminate things, and a particular fire which, in order to shed its rays, needs to burn fuel, like the flame burning in a lantern. Seemingly innocuous, the example is but the celebrated analogy used by Empedocles in an ophthalmological context to argue that the mechanism of the eye is like that of a lantern.⁶⁶ Empedocles’ explanation of the physiology of the eye includes two different kinds of fire, the ‘flame of blazing fire’ (puros selas aithomenoio) that burns inside the lantern, and ‘the finer part of the light’ which ‘leaps out and shines across the threshold with its unyielding beams’ (phōs d’ exō diathrōskon, hoson tanaōteron ēen). It logically presupposes, though does not mention, some inflammable material (e.g. oil) that the flame burns in order to sustain itself, and the residue that is left by the burning process.⁶⁷ Plato, in the Timaeus, will distinguish between the various components of the mechanism of light as three different kinds of fire: the first species is the flame that consumes the fuel; the second species is the effluence of flame, i.e. the light beam or ray that brings light to the eyes; and the third species is what is left from the burning process, the residue of fire (58c5–d1).⁶⁸ Basil reprises the analogy of the lantern, distinguishes between two aspects, an internal and an external, and uses it to explain the

⁶⁶ Fr. 88 Wright = B 84 DK. See Sedley (1992). Here is the fragment in Sedley’s translation: From these divine Aphrodite made the unfailing eyes . . . And just as when someone planning a journey through the stormy night prepares a lamp (luchnon), a flame of blazing fire (puros selas aithomenoio), fitting to it lantern sides as shields against the various winds (anemōn lamptēras amorgous), and these scatter the blowing winds’ breath, but the finer part of the light leaps out (phōs d’ exō diathrōskon, hoson tanaōteron ēen) and shines across the threshold with its unyielding beams (lampesken kata bēlon ateiresin aktinessin); so at that time did she bring to birth the round-faced eye, primeval fire (ōgugion pur) wrapped in membranes and in delicate garments. These held back the sea of water that flowed around, but the finer part of the fire penetrated to the outside (pur d’ exō diïeskon hoson tanaōteron ēen). ⁶⁷ See e.g. Philo, Aet. 91. ⁶⁸ On the Timaean reception and modification of Empedocles’ simile see O’Brien (1970). The Timaean passage names only two out of three species of fire: ‘flame’ (flox) and ‘embers’ (diapura). The second species remains anonymous: it is, literally, ‘what-goes-away-from-flame’ (to apo tēs flogos apion), i.e. the light beam or ray. The tripartite division has a Homeric origin, see Plutarch, Facie 934b6–7 citing Iliad IX.212–13 in a variant version, see the note of Cherniss (1957), 135. According to the Homeric terminology, the second species of fire was named ‘fire’s bloom’ (puros anthos), a metaphor rather than a term, which the Platonists held on to, see Plotinus, Enn. II.1.7.26–30. Basil uses it as a term of art to denote the ray of the stars in a thoroughly Platonic context: tōn astrōn ta anthē (Hex. VII.1 GCS 111.5–6). In the later tradition we find that the proper term for the light ray was augē, see Philo, Aet. 86; Galen’s medical Com. Tim. fr. 18 (Larrain); Aëtius, Plac. IV.13.12–17. There is also a parallel terminology of the ray as aktis, see Plac. IV.13.1–11, with Presocratic resonances, see Plac. II.13.1–5 (atomism) and 6–7 (Empedocles). Both terms denote the fiery beam: augē = aktina purinos, see Plac. II.15.15–25. Aristotle in the Top. V.5 (100b21–3; 103b8–12) and the Sens. 2 (437b14–23), however, reverts to the older terminology of ‘light’ (phōs). This is in line with the tradition of Parmenides (B8.56 and B9.1,3) and Empedocles (B84 DK = 88 Wright), echoed in Tim. 39b4–5, which used the terms pur and phaos interchangeably, but is rather misleading in the context of Tim. 58c5–d1, which clearly distinguishes between the (anonymous) light ray, as a fiery beam and hence a species of fire, and ‘light’ (phōs), as the affection caused by the light ray to the eyes (phōs de tois ommasin parechei). In other words, Aristotle’s terminology obscures the fact that Plato in the Timaeus

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mechanism of celestial fire.⁶⁹ In Hex. III.7 he introduces the lantern simile in a meteorological context to illustrate the internal mechanism of celestial fire, namely how the flame of the planets and the stars (most notably the sun) fuels itself continuously through the consumption of moisture exhalations from the sublunary. In Hex. VI.2 he reiterates the simile, this time in an astronomical context, to illustrate the external mechanism of celestial fire, namely how the celestial flames of the planets and the stars emit rays of light down to earth. Gregory, following Basil, reprises the lantern simile in a meteorological context to illustrate at length the precise interaction of celestial fire with terrestrial water through the mediation of the hydrological cycle.⁷⁰ Later, he bases his entire exegesis of the creation of the heavenly bodies on Basil’s distinction between fire as such (day one) and the particular celestial fire of the planets and the stars (day four).⁷¹ Though he does not mention the lantern simile in this astronomical context, he clearly elaborates on the same physics of fire as Basil, as the identification of the heavenly bodies with celestial flames shows. If so, Gregory too conceives of the light ray in terms of the Timaean second species of fire, i.e. as an emanation or effluence (aporroē). Light travels. And it does so instantaneously.⁷² is already working out a distinction between radiant light (to apo tēs flogos apion) and affective light (phōs de tois ommasin parechei). Nevertheless, it seems that the terminology of ‘light’ for the Timaean second species of fire was accepted in Platonist parlance, which thus had two names for the Timaean light ray: phōs te kai augēn, see Galen, PHP VII.6.2 (= 629.2 de Lacy). The terminology of phōs for the light ray is also attested by Theophrastus in the De igne 3.3–5. Thus, for those who accepted the ray theory, ‘light’ became a standard terminology for the light ray, and it was in this way that the terminology was introduced in modern scholarship by Archer-Hind (1888), 211, followed by Taylor (1928), 410, and Cornford (1937), 247. The terminology obscures that Plato in Tim. 58c5–d1 distinguishes between the fiery light ray and light as an affection, a distinction which prepared the ground for Aristotle’s identification of affective light with ambient light in the De an. II.7 and the Sens. 3. The ancient proponents of the ray theory, however, had the terminology of augē or aktis at their disposal, allowing them to distinguish between ‘radiant’ and ‘ambient’ light. The distinction has been recently reintroduced by Kelsey (2018). I also make use of it for the purpose of the causal analysis of light, see section 3.3.3 below. ⁶⁹ For the lantern (luchnos) as archetypical model of illumination see Theophrastus, De igne §§12, 22, 23, 25, 27, 28, 50; Pliny, Nat. hist. II.8.6; Plutarch, Prim. frig. X (949A); Achilles, Isag. (De universo) IV.4 Di Maria 11.24–5; Bielfeldt (2016). In a hexaemeral context see Severian, Cosmog. I.5 PG 56:435. The imagery of the heavenly bodies as lamps Basil can derive directly from biblical exegesis/symbolism through a Philonian lineage, see Heres 218–22. In the hexaemeral tradition there is a parallel use of the lantern simile as archetypical model for the symbolism of light, see Aristobulus, fr. 5 (Eusebius PE XIII.12.9–16) and fr. 5a (Clement, Strom. VI.16 GCS 137.4–138.4): wisdom as lamp (lamptēr); cf. Philo, Migr. 40 and Spec. I.288: wisdom as light, further Opif. 31: the logos as light; Theophilus, Aut. II.13: the logos as lamp (luchnos); Severian, Cosmog. IV. PG 56: the logos qua Torah as lamp (luchnos) and light. See on the beginnings of this tradition Holladay (1995), 224–6; Walter (1964), 65–81. ⁷⁰ See In Hex. 39–40 GNO 51.8–52.19, pars pro toto argument (hoper en tōi merei touto kai peri tou pantos): what holds true for the physics of fire at the microscopic level of a lantern (luchnos) holds true universally, i.e. also for the physics of fire at a cosmic level. ⁷¹ See §§65–73. The pure fire of day one is the process of diakrisis of fire from the other elements. The heavenly bodies form individual physical systems of fuel, fire, and light through the process of sundromē of fire particles, for which the interaction with the other elements is required. ⁷² Explicitly so in Hex. II.7 GCS 10–12: the nature of aether is so rare and pliable (leptē kai diaphanēs) that the light passing through it (poreuomenon) needs no interval of time (mēdemias parataseōs chronikēs). The question of whether light travels acquires tremendous theological significance in the fourth-century trinitarian debates, see for example the celebrated Letter 38.7.17–20, of

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3.2.4 The Speed of Light We can stretch further the combined reading of Basil and Gregory’s ray theory. The Homilies and the Apology both admit that the light ray conveys thermal power. The identification of the light ray with the second species of Timaean fire explains the reason why. If light is a species of fire it must generate heat. The Timaeus insists, however, that light does not burn. Basil has an explanation for that: the heat of the ray diminishes as it travels because of the cool-down effect of the air that it traverses. That allows the light ray to convey thermal power at long distances, like that between the sun and the earth, yet without any (direct) caustic effects.⁷³ The combined reading of Basil and Gregory offers further helpful insights into the nature of the light ray. Gregory suggests that the light expands uniformly and symmetrically in space. At the end of the already quoted passage on the conical shadow of the earth we are told that if one were to pass from the shadow to light, one would certainly find oneself in light unbroken (mē diakoptomenōi) by darkness. (Hom. opif. XXI.3)

For light to be ‘unbroken by darkness’ it is necessary that there are no gaps in the light rays nor between the light rays. For the light ray to have no gaps in it, it needs to emanate as a continuous stream. For two adjacent rays to have no gaps between them, they need to emanate in continuous and uniform bundles.⁷⁴ If so, light is transmitted uniformly and symmetrically in space.⁷⁵ If we now turn to Basil, we get the justification for light’s symmetrical flow: it is because light is a simple and

disputed Basilian authorship and a recent strong tendency towards Gregorian attribution, see Zachhuber (2003); Silvas (2007), 247–9; Maspero, Espositi, and Benedetto (2014); Radde-Gallwitz (2009), 115–16. The author of the letter uses the classic ‘Timaean’ terminology of flox–augē–phōs (see above), which is a reference as clear as it can be to the ray (augē) as an emanation from flame (flox) in the sense of the second Timaean species of fire. Letter 38 confirms the picture: light flashed forth the moment fire was lit (homou te hē phlox anelampse kai sunapēugasthē to phōs). Light travels. ⁷³ The air has a cool-down effect depending on its exposure to fire and the presence of moisture in it, see Hex. III.7, III.8, IV.5, VI.10. Gregory expresses the same idea in 55 GNO 65.20–66.2 (see also §§29 and 41). In the context of the Aristotelian theory of the elements that Basil and Gregory follow, air is primarily humid and becomes cold with the departure of (the sun’s) heat, which results in the condensation of moisture into water, see Meteor. I.9–12 (347a–349a), II.9 (369a–b). Thus, in Aristotle’s biological writings, air has a natural cool-down effect next to water, see Part. anim. III.6 (669a). The same idea can also be maintained mutatis mutandis in the context of Stoic physics, according to which air is primarily cold, see Philo, Deus 79 (already discussed in Chapter 2). ⁷⁴ For the light rays forming a continuous bundle see Ptolemy, Optics II.50; Lindberg (1986), 16. For the Christian reception see Thaumaturgus (?), Ad Philagrium §7 (= PG 46, 1105 transmitted as Nyssen’s Letter 26 Ad Evagrium): potamēdon = like a flowing stream. ⁷⁵ This raises the question of the interaction of the ray particles with the particles of air or water present in space (the so-called ‘medium’, for which see section 3.3.1 below). The sources presuppose that the foreign particles do not create gaps in the ray nor do they affect its uniform expansion in space. But then where do the foreign particles go? For an answer see Appendix B.

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homoiomerous substance.⁷⁶ Being simple and homoiomerous, light expands symmetrically in all directions.⁷⁷ But not ad infinitum. The further crucial piece of information we get from the combined reading of Basil and Gregory is that light travels not in a vacuum but in a medium (air or water) with variable density, which affects the ability of light to travel. In his explanation of the first illumination Basil writes: The air was illumined (perielampeto de aēr), or rather, it held the whole light completely permeating it (egkekramenon heautōi holon diolou eiche to phōs), sending out dazzling rays in every direction (pantachou) to its uttermost bounds. It reached upward even to the aether itself and the heavens (aithera kai ouranon), and in extent it illuminated (katephōtize) in a swift moment of time (en oxeiai kairou rhopēi) all parts of the world (panta ta merē tou kosmou), north and south and east and west. For, such is the nature of aether, so rare (leptē) and transparent (diaphanēs), that the light passing through it needs no interval of time (hōste mēdemias parataseōs chronikēs prosdeisthai to phōs di’ autou poreuomenon). As it passes our glances (opseis) along timelessly (achronōs) to the objects at which we are looking, so also it receives the rays of light (tas tou photos prosbolas) on all its boundaries instantaneously (akariaiōs), so that one could not conceive a shorter moment of time (elattona chronou rhopē). (Hex. II.7 GCS 32.5–15 tr. Way, amended)

Basil tells us that the ray travels instantaneously (akariaiōs) in aether because of aether’s rare and transparent nature (phusis leptē kai diaphanēs). ‘Instantaneously’ here means the absence of any passage of time, as timelessness (achronōs) and non-extensionality (mēdemias parataseōs chronikēs) clearly indicate. But the language used is ambiguous, introducing at the end the notion of an infinitesimal length of time (en oxeiai kairou rhopē), conceivable only in thought (hōs oud’ an epinoēseie tis elattona chronou rhopē). This is possible only if light travels at infinite speed.⁷⁸

⁷⁶ See Hex. II.7 GCS 33.10–13. ⁷⁷ Unless of course light is obstructed by an opaque surface. Thus, the visual current projects conically because the anatomy of the eye leaves only a spherical cap of the eyeball without membranes, namely the cornea. The heavenly bodies as celestial lamps are not confined by opaque borders and are able to radiate the light uniformly in every direction. The principle is expressed in the optical fragments attributed to Geminus: ‘every part of the sun sheds forth light’ (Schöne 28.4). For its hexaemeral application see Hex. VI.9 GCS 104.16–17 (tr. Way): ‘the brightness poured forth from them [sc. the sun and the moon] suffices to light up the heavens and the air, and at the same time to extend to the earth and the sea’. ⁷⁸ The liminal temporality of light’s motion in space is a substantial aspect of Aristotle’s famous critique of the emanation theory of light in the De an. II.7 (418b20–6) and the Sens. 3 (440a20–31) and 6 (446a27–447a12). Behind it lies the concern about the coherence of actual infinity as developed in the third book of the Physics. Aristotle clearly applies the concern to the Empedoclean-Timaean theory of light and colours as aporroē denying the coherence of an instantaneous motion of the light ray, see De

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3.2.5 Introducing Field Theory Given that the ray travels at infinite speed, one would expect it to traverse any region of space until it reaches the extreme limits of the universe. This is not always the case. Basil gives us clear indications that the range of the ray varies according to the medium, i.e. the ‘stuff ’ that fills the intermediary space that the ray travels through. Aether, we just saw, allows the light to permeate it completely because of its fine and porous structure. Yet, we are told later, the denser parts of lower air generate more resistance, preventing a weak beam of light from travelling far.⁷⁹ Finally, water, which is even denser than air, prevents the light from fully penetrating the deep.⁸⁰ The examples suggest a field variable. Everything else being equal, the light should travel until it hits upon an opaque surface. But everything else is not equal. The resistance of the intervening space varies according to the density and purity of the medium (aether, air, water, and their admixtures). Thus, the resistance of the medium determines the ray length, i.e. the distance a ray is able to travel. There is another variable that co-determines the ray length: the size of the fire that generates it. Basil cites two examples: The light of sun is able to illuminate the whole sky and the atmosphere, while the light of the stars can barely reach the surface of the earth, weakened by the distance, in spite of the fact that the stars

an. 418b21–3: hōs pheromenou tou photos kai teinomenou pote metaxu tēs gēs kai tou periechontos, hemas de lanthanontos; Sens. 440a22: chronon anaisthēton. Since Aristotle too accepts light’s instantaneous transmission, but denies the possibility of instantaneous motion, he reconceptualizes light as an immaterial activity (energeia), which no longer requires time for its propagation, see Ross (1906), 21–2, 157, 211–14, 224–6. Later Peripatetic commentators also react strongly against the possibility of light having a corporeal nature and travelling at infinite speed, see Sambursky (1987), 113. In affirming light’s instantaneous motion, Basil sides with the Platonic tradition. The language of liminal temporality, seemingly ambiguous, simply reiterates Aristotle’s language of ‘imperceptible time’, itself contradictory on Aristotle’s account, showing that Basil falls, like any other Platonist, within the realm of the Peripatetic critique. Ambrose, Exam. I.9.33, retains the same language: momento temporis sine nulla conprehensione. Gregory attempts to clarify in what sense one may speak of instantaneous motion: comparably to the speed of thought (isa noēmati 14 GNO 25.4). Clearly, one may share Aristotle’s concerns about the implied notion of ‘infinite’ velocity underlying instantaneous transmission of particles in space. Yet the followers of the particle theory of light need only claim that, given instantaneous transmission, ‘imperceptible time’ denotes that the speed of light is defined by the limit (i.e. that it is only potentially infinite). The notion of the limit, however, seems rather controversial in post-Nicene theology as it could render support to the anti-Nicene position that ‘there was a time when [light] was not [transmitted]’; cf. Athanasius, C.Ar. II.31–5; Gregory (?) Adv. Ar. et Sab. GNO 74.8–19 and 76.5–8. Thus, regardless of the disputed question of its authorship, Letter 38 clearly states the pro-Nicene position that light travels in no interval of time: ou mēn paratasei tini diastēmatikē, hence, by inference, with ‘infinite’ speed, see Basil (?), Letter 38.7 = Gregory, Letter 35.7. From now on, I will assume that this is the Cappadocian standard position. ⁷⁹ See Hex. VI.9 GCS 105.7–12 as regards the visual ray. But the visual ray is akin to the light ray, only weaker, see Tim. 45b4–d5. ⁸⁰ See Hex. II.4 GCS 27.13–21. Basil qualifies twice the ability to see through water (pollakis, i.e. not always), which I take to imply penetration limits according to density and/or depth.

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are so numerous, sending uncountable rays to earth.⁸¹ Conversely, the light of the stars is able to reach the surface of the earth even though it does not have the power to illuminate the atmosphere. Yet the visual ray, i.e. the light of the eyes, is even weaker, unable to penetrate the air without the support of external light.⁸² There is a clear difference in the intensity of light which directly affects the distance a ray is able to travel. Basil’s explanation is that the difference is contingent upon the concentration of fire in the source: the bigger the fire, the greater the intensity of the light emitted.⁸³ But we already know that the light emits symmetrically as a homogeneous and continuous stream, which means that there can be no qualitative difference between one ray and another. And since the difference in intensity is quantifiable, the implication is that bigger fires emit stronger rays or thicker bundles. It turns out that the distance a ray is able to travel (‘ray length’) is a function of the compactness of the bundle and the compactness of the medium.⁸⁴ This explains why Gregory, in the Apology, can maintain that light travels instantaneously (euthus) in outer space (§10), and yet only a weak portion of the light of the stars reaches the earth (§70). Evidently, the ray behaves like a corpuscular entity of a special status. Being quasi-immaterial, light travels with infinite speed. And yet its impact factor is influenced by the medium. We must then concede that light’s kinetic behaviour is contingent upon the physical properties of the field.⁸⁵

⁸¹ See Hex. VI.9 GCS 104.14–21 and VI.10 GCS 106.9–21. Basil is here elaborating a general principle of ancient dynamics: the further radiating powers extend from their source, the weaker they become (quanto magis a principiis elongantur, tanto debiliores fiunt), see Ptolemy, Optics II.20 Lejeune 5–6. Light is a paradigmatic case, see Ptolemy, Optics II.17–18, 20, and III.21–2. The underlying metaphysical principle is that the cause is greater than its effect, see Lloyd, Phronesis 21 (1976), 146–56. ⁸² See Hex. VI.9 GCS 104.14–17 and 105.7–10. ⁸³ For the principle see Ptolemy’s Optics II.17–18. ⁸⁴ For the variant impact of the medium on the ray according to composition and density see e.g. Ptolemy, Optics V.30. For the notion of radiant intensity see Optics II.17–20. Ptolemy understands the ray as a quantifiable power (quantitate virtutum), which becomes ‘weaker’ as it moves away from the source: corrumpuntur (II.18); debiliores; radio minori in uirtute (II.20) etc. The language denotes that the ray ‘wears off ’, presumably in the sense of the bundle becoming thinner, see the following note. ⁸⁵ So far, I have sought to explain the motion of the ray by recourse to the laws of general dynamics and more specifically of projectile motion, following Gregory’s explicit analogy of the ray to a flying arrow, see In Hex. 14 GNO 25.1 and sections 3.2.3 and 3.3.1, see further for Ptolemaic optics Smith (1996), 76 nn.21 and 23, 78 n.29, expressing a general principle. General dynamics, however, cannot explain the constancy of light’s speed, which should vary as the ray travels through denser fields, see Smith (1996), 23–4 (‘weakening’ = ‘slowing down’). Yet I can find no indication in the Cappadocians, nor in any of their possible sources, that the speed of light varies. On the contrary, Heron, Catoptrica (= ps.-Ptolemy, De speculis) I.3–4 Jones 154 (= I.2 Nix/Schmidt 320.10–322.8), explicitly argues that the speed of light is constant (continua velocitate) and infinite (infinita), covering vast distances instantaneously. See also the 13th hypothesis of Damianus’ Optica (Schöne 16.11–12): hē tou hēliakou phōtos epektasis achronōs ginesthai doxeien. The Cappadocians too subscribe to the view that light travels instantaneously at infinite speed, regardless of radiant intensity and the resistance of the field. This prompts two remarks. As regards radiant intensity, it is clear that the Cappadocians take the light’s power to co-determine the ray length but not its speed. The bundle of light becomes thinner and thinner (‘weakens’) as the ray travels through space until it is completely wiped out reaching the end of

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3.3 The Metaxu of Light: A Metaphysical Note on the Medium 3.3.1 A Medium of Light? I have been talking about the effect of the medium on the light ray. A note is appropriate here as regards the effect of the light ray on the medium. The ray theory does not, strictly speaking, require a ‘medium’ as an intrinsic part of the mechanism of light. Light, as such, is the natural power of fire, an effluence that springs forth as a continuous stream from its fiery source. As already noted, however, the light ray does not travel in a vacuum. In ancient physics there is no conceptual space for an intra-cosmic void unless one is an atomist.⁸⁶ The Cappadocians expressly reject atomism, because of its materialistic metaphysical connotations, and with it the notion of ‘empty space’.⁸⁷ Since there is no empty space in the hexaemeral physics, there is always a metaxu of light, i.e. a mass or ‘stuff ’ (aether/air, water, and their admixtures, i.e. ‘exhalations’, clouds, smoke, etc.) that fills the space between a fiery source and the surface of things. And since the light ray is of a corporeal nature, as I have argued, there is a necessary physical interaction between the stuff of the medium and the ray that travels through. This does not make air a medium of light more than it makes air a medium of a flying stone, arrow, or spear. In all cases of projectile motion there is some kind of mass occupying the intermediate space, something (air, aether, etc.) that the ray, the stone, the arrow, or any flying object needs to pass through in order to reach its target. Only in the latter sense can one speak of a (local, i.e. external) medium of light in Cappadocian physics.⁸⁸ The medium is nothing other than the particles

its journey. The change happens as a continuous but instantaneous process due to the ray’s extreme speed. The ray’s extreme speed is, in turn, possible due to light’s liminal corporeality (see section 3.1.2 above). Both features (extreme speed and liminal corporeality) make the ray a singular phenomenon in the Cappadocian physical universe. As regards the resistance of the field, the Cappadocians understand it as the other co-determinant of the ray length (next to radiant intensity). This influence of the medium on the transmission of light suggests the existence of up to now unexplored undulatory (wavelike) properties. I feel that the issue requires further investigation. The analogous function of light and sound in ancient sources, such as Plato, Rep. 530d and Tim. 47c4–e2; Aristotle, De an. II.8 (419b28–33); Ptolemy, Harmonics III.3, could be fruitful in that respect. ⁸⁶ See Long/Sedley 6 with comments ad loc. ⁸⁷ See Basil, Hex. I.1 GCS 1.9–10 and I.2 GCS 4.7–17; Gregory, In Hex. 9 GNO 19.5–6 and 17 GNO 29.12–17, with the explicit rejection of the void. ⁸⁸ This is clear for Gregory, who only speaks of air as a medium of vision, not of light, see In Hex. 25 GNO 39.2–3: blepomen gar di’ autou. Vision, contrary to light, needs a medium to occur, see section 3.3.2 below. The case seems to be different with Basil, who speaks of the ability of the transparent air/ aether to receive (dechomenē, upodechetai) the ray and to send it along (parapempousa, parapempōn, parapempei), in a way analogous to the visual ray, see Hex. II.3 GCS 26.5–7 and II.7 GCS 32.5–15. A careful reading of the Basilian passages shows that there is no functional medium of light in Cappadocian physics, in the sense of the medium being part of light’s definition. There is only intermediate space filled with stuff, necessarily influencing and being influenced by light’s kinetic behaviour, yet only incidentally so. Basil uses a similar technical vocabulary as regards Aristotle’s other known medium, namely water. For Basil, waters not only receive the light letting the ray pass through

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occupying the space extending between a fiery source and the surface of things (‘ambient space’).

3.3.2 Transparency and Brightness The question is what happens to the medium when it receives a bundle of rays. To put it differently, what is it that allows a bundle of rays to travel through ambient space but not through an opaque, solid object? The answer is simple: it is the medium’s transparency. Basil speaks of transparency (diaphaneia) on three occasions, approaching it from two angles: as regards vision, transparency is what allows the medium (air) to ‘admit all the forms of visible objects and transmit them to the eyes of the spectators’ (Hex. II.3). As regards the nature of the medium (aether) itself, transparency is what allows ‘the light to pass through’ (Hex. II.7). In both cases Basil mentions transparency together with the rare (araia) or fine (leptē) nature of the medium, suggesting that dense materials do not have enough transparency to allow light to pass through.⁸⁹ If we now turn to Gregory, we find a more detailed analysis of the transparent nature of the medium. (dechomena tēn augēn) but also send some of it away (alla kai antipemponta), causing the phenomenon of reflection (kata tēn anaklasin). Thus para-pempō and anti-pempō denote two different modes of interaction of light with transparent substances (air and aether = diaphanēs, see Hex. II.3 and II.7) and translucent substances (water and crystals = diaugēs, see Hex. II.4 and III.4), respectively. While a transparent substance allows all of the light rays to pass through, a translucent substance does so only partially, reflecting the rest of the light rays. In this context, the proper range of meanings of parapempō is between ‘reflect’ and ‘allow to pass through’. Any rendering as ‘pass on’, ‘send along’, or ‘transmit’, etc. should be understood in terms of being permeated by light rather than as an active transmission, not even in the sense of antiperistasis, i.e. of the interchange of places between the air’s particles and the particles, as some thinkers had suggested; cf. Alexander Aphrodisias, De an. 29.15–27; Mantissa 128.31–129.7; Plotinus, Enn. IV.5.2.34–48. The Cappadocians seem to endorse a version of antiperistasis in general, see Risch (1999), 194–5 n.236, 195–6 n.238. But they do not apply it to light, nor could they in my view, since, contrary to rocks and missiles, the light ray is continuous and leaves no space behind it for the displaced air particles to fill in. The only possible physical interaction between the ray and the air, then, must be the continuous infiltration of air by the ray as it passes through, forming a continuous body, see Hex. II.7 GCS 32.6: the light is totally blended with air; Hex. VI.4 GCS 94.16–17: the air is not dispersed by the ray. The corpuscular ray excludes Aristotle’s theory of a functional medium (Aristotelian theory of the transparent). The absence of a tonic or pneumatic theory also rules out the Stoic theory of a sympathetic medium (theory of stretched air or Stead’s tasis model). That means that the Cappadocians work along the lines of a Platonic construction of the medium, the existence of which is often forgotten, but which is rightly coming back to attention through the study of Betancourt (2018), esp. 34–8. The exclusion of antiperistasis, together with the instantaneous transmission of light, prepares the ground for a significant later development in ancient physics by an author who follows closely in the footsteps of Cappadocian exegesis, namely Philoponus’ impetus theory of light, for which see Sambursky (1987), 74–6, 113–17; De Groot (2016). ⁸⁹ Between transparent (diaphanēs) and opaque objects there is the intermediate category of translucent objects (diaugēs), like liquids (esp. water) and crystals, see Hex. II.4 and III.4. Translucency is, apparently, transparency of a diminished degree. The conception of transparency, translucency, and opacity according to the permeability of substances to light and permeability according to the degree of a substance’s rarity and fineness seems to be a Platonist development of the notion of transparency, see Plotinus, Enn. II.1.7.43–9 (discussed in section 3.1.2 above). It takes Basil away from the Aristotelian definition of transparency according to surface boundaries or, in the

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Air is able to receive all things because of its supple and pliant nature, showing all things in itself, since it possesses no colour of its own, no shape (schēma), no surface, but takes its outline through foreign colours and shapes. It becomes bright (lampros) when light shines (tēi tou photos ellampsei) and it falls back into dark (kai palin melainetai) when shadowed. Air by itself is neither bright (lampros) nor dark (melas). It is surrounded by every shape and filled by every kind of colour. It accommodates every type of movement. (In Hex. 25 GNO 38.6–17 tr. McCambly, amended)

The passage does not mention ‘transparency’, but it clearly describes it: it is the property of the medium (air) ‘to receive all things because of its supple and pliant nature, showing all things in itself ’. But this property cannot be actualized without light, in the absence of which the air becomes dark. On the contrary, when light enters the medium, its transparency is activated, and it becomes bright. Transparency, then, becomes apparent as the ‘borrowed’ brightness of the medium, a quality not intrinsic to it, since ‘air by itself is neither bright nor dark’ but extrinsic. And since ambient space has no colour of its own but becomes bright when the light shines in it, brightness functions as a colour: it is the epiphenomenal colour of the medium qua transparent.⁹⁰ If we now ask, why is it that ambient space becomes bright in the presence of light, Basil gives us a further lead. He suggests that brightness is the intrinsic property of light, light’s own proper colour. Just as whiteness is an accidental quality whose bearer is predicated as ‘white’, so too is brightness an accidental quality, whose bearer is called ‘bright’.

case of air and water, according to the lack thereof, see De sensu 3 (439a17–b14). Unless, of course, one assumes that air and water exhibit a high degree of rarity in their particles, hence of transparency, precisely because they do not have determinate boundaries. ⁹⁰ On the transparency of the medium see Kalderon (2018); Ierodiakonou (2018). As already indicated, the Cappadocians expound a modified theory of the transparent medium, fusing Aristotelian insights with Platonic physics (ray theory). In bringing the two approaches together, the Cappadocians creatively emulate a widespread tendency in late antiquity, for which see Karamanolis (2006); Golitsis (2018). Aristotle already distinguished between ‘transparency’ as a property of the medium and (ambient) ‘light’ as the activity of fire that activates that property, see De an. II.7 (418b4–13); Sens. 3 (439a17–33). From then on ambient light is construed as an epiphenomenon in the later Platonist tradition (Plotinus), see Kalligas (2012), 56–8, and Gurtler (2018), 158–9; and as an extrinsic colour of the transparent medium in the Peripatetic tradition (Alexander of Aphrodisias), see Caston (2012), 164–6 (n.397 ad De an. 44.16). Ambient light is thus an example of a ‘Cambridge change’, as Burnyeat (1995) nicely showed (though Burnyeat did not refer to the colour of the ray since he was discussing the De an. II.7, which rejects the corpuscular ray theory). The transparency of air may also change due to additional factors, like moisture affecting its density and generating a redder colouration, even though the colour of the ray does not change, see Hex. VI.4 GCS 94.13–20. One must therefore distinguish between the colourless nature of the medium (‘transparency’) and its supervenient colouration (‘ambient light’). Ambient light is a supervenient affection of air in the sense of a change in colouration, not in colour, see further Appendix B. The difference between ambient light and the colouration of air when extra factors are added is like looking at the world through colourless and tinted glasses. It is only the colour of our spectacles that changes, not the colour of things.

     

143

Do not let what has been said seem to anyone to be beyond belief, namely, that the brightness of the light (tou photos hē lamprotēs) is one thing and the body that is the substrate of the light (to hupokeimenon tōi phōti sōma) another. First, because we divide all compounds (ta suntheta panta) into the bearing substance (tēn dektikēn ousian) and its accompanying quality (tēn episumbasan autēi poiotēta). Just as, therefore, whiteness (hē leukotēs) by nature is one thing, but a whitened body (to leleukasmenon sōma) something else, so also the things just mentioned, although different (diaphora) by nature, are brought together (hēnōtai) by the power of the Creator. (Hex. VI.3 GCS 91.12–92.1 tr. Way amended)

I have already discussed the context of this passage when I referred to Basil’s dependence on Origenian-apocryphal material (Chapter 3, section 3.1.1). The issue at hand is the difference between the light of the first day and the light of the stars on the fourth day. The gist of the argument is that the heavenly bodies, being the bearers of the purest form of light, are pre-eminently bright. Celestial fire, by inference, is the paradigmatic example of a bright substance in the hexaemeral physical world.⁹¹ If we now combine this passage on the brightness of celestial fire with the previous one on the brightness of ambient space, we realize that brightness has a double function: on the one hand, every fiery body, being inherently luminous, is bright by nature. On the other hand, the medium, having no colour of its own, becomes bright in the presence of light. Brightness as the perceptible aspect of luminosity is the colour of things that are or become luminous. Light is the agent that conveys the brightness of fire to ambient space and makes it bright. That turns light into the link that connects fire and the world.⁹² ‘Light’ as the intrinsic property of fire (in the sense that every fire is essentially luminous) is visible as pure brightness. ‘Light’ in this sense denotes the colour of fire. ‘Light’ as the natural power of fire (in the sense that every fire emits light) is what emanates from flame diffusing its brightness to ambient space. ‘Light’ in this sense denotes the ray. ‘Light’ as the external activity of fire (in the sense that every fire transmits light) is what transfers the brightness of fire to ambient space, affecting its colouration. ‘Light’ in this sense denotes illumination. ‘Light’ as illuminated space (in the sense that ambient space becomes bright) is the supervenient change in the phenomenal properties of the medium making it look bright. ‘Light’ in this sense denotes the colouration of space. As already explained, ⁹¹ This fits well with the Platonic theory of colours, if we regard brightness (lampron) or brilliance (stilbon) in Tim. 67e6–68a8 as the colour of extremely concentrated fire, like that of the heavenly bodies, most notably the sun, cf. 40a2–4. Thus, Plato calls the sun ‘bright’ (Theaet. 208d2; Rep. 616e9–10) and so too the light (Rep. 616b6). For Philo pure light is ‘brilliant and bright’ (Opif. 30), while the archetypical celestial luminosity out of which the stars are made is ‘all-brightness’ (Opif. 31). For Plotinus the sun is ‘most brilliant’, and the light is ‘brilliant’ (Enn. II.1.7). On the colour of light see further Appendix B. ⁹² Cf. Rep. 508a1: light as zugos (bond) between the eye and the coloured surfaces of things.

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      

this is no real change. What looks like transparent brightness is merely the colour of the luminous ray as it travels through colourless space.⁹³

3.3.3 Light Semantics as Key to Light Hermeneutics If my analysis is correct, the term ‘light’ is revealed to be a pollachōs legomenon. In one sense, it denotes the luminous source, i.e. a particular instance of fiery nature in the world, a bright flame (phōs = pur/phlox). In another sense, it denotes the productive power of fire, i.e. the bright emission that comes out from flame, a ray of light (phōs = augē/aktis). In a third sense, it denotes the illuminating activity of fire, i.e. the action of the ray in ambient space causing it to become bright (phōs = phausis). In a fourth sense, it denotes the external product of fire, i.e. the change caused in ambient space by the activity of the ray, the most typical example of which is daylight (phōs = hēmera). The combined action of the first three, active and causal, senses of light (i.e. the luminous source, its power, and its activity) results in the manifestation of the fourth (i.e. the illumination of space). It is in the latter, passive and caused, sense that light becomes a visible phenomenon in the world, activating the perceptual faculty of phantasia. This is a further, stretched, sense of ‘light’, indicating that phenomenality (phainesthai) is the derivative outcome of the concurrence of the three active senses of ‘light’ (phōs as pur/ phlox, augē/aktis, phausis) and the converse side of the fourth passive sense (phōs as hēmera).⁹⁴ While the triptych of the luminous substance–power–activity denotes the active aspect of light as causal event, the illumination of the medium denotes the passive aspect, light as the phenomenal product of the active. This polysemy of the language of light can lead to misunderstandings if the different senses and the corresponding causal stages are not clearly distinguished by conceptual analysis. Thus, ‘light’ might appear as both cause and effect, but it will not be the same respect that ‘light’ denotes as cause and as effect.⁹⁵ Similarly, one may speak of ‘light’ as cause of ‘illumination’, and yet one will still need to ⁹³ There is thus a clear chain of causality: space becomes bright because of the brightness of the ray, which is itself bright because it is the luminous power of a fiery substance. Luminosity, as the essential property of fire, is the causally prior property and the explanans of the intrinsic colour of fire and the supervenient colour of the medium, see the discussion at the end of Chapter 2, sction 2.3.2. Though luminosity as essential property remains unknowable, it reveals its nature through its illuminating power (‘radiant light’). And since the illuminating power of fire is what causes the illumination of space (‘ambient light’) and the illumination of space is, in fact, the brightness of the ray filling it, luminosity manifests itself as brightness. See further Appendix B and Appendix C. ⁹⁴ For the widespread ancient etymology of phenomenal reality (phainomenon) and its perception (phantasia) from light (phōs/phaos), see Chapter 1, section 1.4.3. ⁹⁵ A chain of causal events can be predicated in more than one way, even though the chain remains numerically one. Light is a case in point. The emission of light (‘radiant light’) and the illumination of space (‘ambient light’) are one and the same reality in the world, namely the activity of the ray in the medium, though they differ in definition (logos) and in being (to einai). It is like the road from Thebes to Athens and from Athens to Thebes, to reprise Aristotle’s example of showing how the actuality of the

     

145

clarify that the one event of the propagation of light involves three conceptual stages, namely a luminous source (the flame), its power (the ray), and its activity (illumination of space), that are one inseparable unity in the physical world but are distinguishable in thought.⁹⁶ What the various senses of ‘light’ have in common is that they express different meanings of luminosity or brightness (lamprotēs): luminosity as the essential property of fire (essential light); luminosity as a property of the ray emitted from flame (radiant light) and transmitted to ambient space as brightness (ambient light); finally, brightness as the epiphenomenal colour of illuminated space (affective light).⁹⁷ If the above attribution of senses to references is correct, it reveals a comprehensive linguistic and conceptual framework of light, aiming to capture the luminous phenomenon from a holistic perspective. Neither the framework nor the language is new: the causal connection between luminosity and phenomenality is already laid out in the Timaeus (31b5), together with a rich and variegated vocabulary of light and colours, its explanatory principles, and the different modes of manifestation of lamprotēs (39b2–c2, 45b2–46c6, 58c5–d1, 67c4–68d7, and more generally 55d7–61c2). But the systematic framework is novel, or at least it is the product of a long process of mutual interactions and discussions between the schools that lead to the synthesis of elements that are still disconnected in the Platonic or the Aristotelian corpus and the Stoic fragments. The Cappadocians bear witness to this grand synthesis, which appears to give rise to a table of correspondences between the language of light, the physics of light, and the metaphysics underlying the causal chain of events that explains the manifestation of light in the world. Table 3.1 depicts the successive stages of transmission of a property from a fiery nature or substance to its environment. A fiery substance is a concentration of fire particles, typically experienced as flame. The property transferred is luminosity or brightness. The conductor is the light ray, the effluence from flame. When a flame

motion of an agent (e.g. teaching) is the same as the actuality of the patient being moved (e.g. learning), see Phys. III.3; similarly for production (building) and its product (being built), see Metaph. IX.8; Bradshaw (2004), 16, 91. Applied to light, Aristotelian causality means that the emission of light and the illumination of space are, in fact, one reality predicated in two different respects. This prevents any logical confusion between light as productive power and light as product. Though the two signify the same reality (illumination), they describe it differently: ‘radiant light’ from cause to effect, as the productive power of fire, and ‘ambient light’ from effect to cause, as a change in the colouration of the medium. This does not signify different causal chains. Illumination is one event in the phenomenal world. ⁹⁶ The triple causality of light acquires particular theological significance through the two analogies of light that we find in early Christian literature: i) the sun and its radiance (substance–power–activity model), and ii) a light kindling another light or three suns (triple co-agency model), for which see Katsos (forthcoming). In both models, illumination is the external product and joint event of three equally necessary agents, indicating the equipollent causal agency of the divine persons in the world. Conversely, the explanatory priority of the first to the second and the third agents indicates the internal causal hierarchy of the divine persons. ⁹⁷ For the double sense of lamprotēs as ‘luminosity’ and ‘brightness’ see Appendix B.

146

      

Table 3.1 Light as a pollachōs legomenon (different senses of light)⁹⁸ semantics

phōs (= pur)

phōs (= aktis)

phōs (= phausis)

phōs (= hēmera)

physics metaphysics

fire nature/substance

ray power

illumination activity

illuminated product

appears in the medium it transmits its luminosity to the surrounding space through its ray. The transmission effects a change in the phenomenal properties of the medium, whose colouration now becomes bright. The illuminated medium is perceived by a percipient agent as visibility of space and everything contained therein.⁹⁹ The three causal factors, namely the luminous substance, its power of illumination, and its illuminating activity, coexist and work together externally as a triple agency producing light as a perceptible phenomenon in the physical world. Internally, however, the properties of the ray and the impact of its activity are determined by the kind of flame that produces them (see Chapter 2, section 2.3.2 and Chapter 3, sections 3.1.2 and 3.1.4). Thus, the ray and its motion are the proximate causes of external illumination, while the flame that produces them is the ultimate source of the causal change. Both internally and externally, there is no ⁹⁸ The table follows Barnes (2001), esp. 303, who suggests the following explanatory scheme for the Cappadocian metaphysics of power causality: nature (phusis)–power (dunamis)–activity (energeia)– product (ergon). I here expand the causal scheme and apply it to light. The causal scheme is attested in a variety of Christian and non-Christian sources, including Philo, Galen, Origen, Hilary of Poitiers, Marius Victorinus, Iamblichus, Julian, Eunomius, Gregory Nazianzus, Ambrose, and Gregory of Nyssa, see Barnes (2001), 15–17, 98–9, 159, 168, 189–95, 239 n.69, 297–305, see also Barnes (1993). Its standard expression is ousia–dunamis–energeia (‘essence/substance–power–activity’). In that form it is accepted by Platonists, Philo, and the Church Fathers, see Bradshaw (2004), 57–9, 62–4, 136 (adding Porphyry to the list), 239 (reaching down to Gregory Palamas). Athanasius, Ad Serapionem I.30.33–5, gives us the correspondence to scriptural light terminology: light (phōs)–radiance (apaugasma)– activity (hē toutou energeia)–luminous gift (augoeidēs charis). The scheme is unpacked differently in different schools. I here take it to refer to the predicative functions of ‘light’ mentioned at the end of Chapter 2, section 2.3.2. This yields the following equations: ousia = fire particles as instances of luminous essence, experienced as flame at the source and as ray in space (predicated as ‘light’ essentially—essential light); dunamis = the penetrative power of fire particles, experienced as the ray emanating from the source (predicated as ‘light’ peculiarly—radiant light); energeia = the action of the ray particles on the particles of the medium through which the ray travels (predicated as ‘light’ accidentally—ambient light); ergon = the end product of the activity of the ray on the medium resulting in the qualification of space as ‘luminous’ or ‘bright’ (predicated as ‘light’ also accidentally—affective light). For the full table of correspondences see Table 3.2. For the action of ray particles on the medium see Appendix B. For the theological applications see Appendix C and in detail Katsos (2022) and Katsos (forthcoming). ⁹⁹ Illumination is therefore the archetypical case of what Lloyd (1976), 146, has called the ‘transmission theory of causation’, i.e. ‘a notion of causation as the transferring or transmitting of some property from one thing to another’. The theory implies that causes are either identical or similar to their effects, see Metaph. XII 1071a27–9 and Gen. anim. 734a30–2; further, that the causes have the property transmitted to the highest degree, see Metaph. 993b24–6 and An. post. 72a29–30. The theory explains why illumination is the transmission of luminosity or brightness from fire to ambient space. Not only that, but also why fire is intrinsically, i.e. essentially, luminous and the brightest natural substance.

   :   

147

flame without ray, no ray without motion, and no ray motion which does not illuminate the part of space a ray moves in. The external phenomenal unity of the triptych flame–ray–motion is the subject matter of the physics of light. The internal conceptual separation of source–power–activity is the subject matter of the metaphysics of light. Ultimately, however, physics and metaphysics are just two aspects of one and the same event of illumination in the world. Physics and metaphysics capture the causal chain of analysis of one and the same light of the world conceived in its external unity and in its internal diversity (see Table 3.2).

3.4 The Metaphysics of Light: A Hermeneutical Coda 3.4.1 A Dual Aspect Interpretation The two parallel axes of the Cappadocian contemplation of light, the physical and the metaphysical, take us back to the bigger hermeneutical issues at hand when dealing with the hexaemeral narrative. The double analysis requires a double textual support, if it is to be a hexaemeral analytics of light at all and not the whimsical display of Cappadocian erudition, as ancient and modern critics complain. Basil provides the textual basis needed by distinguishing between the light of the first and the light of the fourth day of creation. Day one entails the metaphysics of light: an approach to light from an abstract-theoretical perspective, light as such. Day four on the other hand elaborates on the physics of light: light as part of a physical system, like the particular light of the heavenly bodies or the lantern. Basil gradually develops this dual hermeneutics of light in two passages. The first passage introduces the double approach (day one–day four): Now, henceforth, after the creation of the sun [sc. day four], it is day when the air is illuminated by the sun shining on the hemisphere above the earth, and night is the darkness of the earth when the sun is hidden. Yet, it was not at that time [sc. day one] according to solar motion, but it was when that first created light was diffused and again drawn in according to the measure ordained by God, that day came and night succeeded. (Hex. II.8 GCS 34.6–10 tr. Way)

The second passage explains why this double approach is needed. I have already quoted and commented on different parts of this ambiguous passage, preparing the ground for its final discussion. I can now quote it again, this time in full. See, therefore, whether He does not make sufficiently clear what He wished by the word phauseōs [sc. Gen. 1:14]; instead of ‘illumination’ (phōtismos) He said ‘lighting’ (phausis). This does not conflict with what has been said about ‘light’ (phōs). In fact, at that time [sc. day one] the very nature of light (tou phōtos hē

Table 3.2 Table of causal analysis of the different senses of light sense

‘light’

‘light’

‘light’

‘light’

reference in nature in Genesis 1 in Timaeus

flame phōs, phōstēr phōs, pur, phlox

motion ray diachōrizein, phausin, phainein phōs (op. skotos) phōs (hēmeron), pur, to apion parechein (phōs)

illuminated space (kalein to phōs) hēmera (methēmerinon) phōs

explanatory priority causal agency

source agent/efficient cause (active and causal)

power conductor/instrumental cause (internally: caused by flame externally: active and co-causal)

activity transmission/action (internally: caused by flame externally: active and causing)

product effect/end product (passive and caused)

qualification

essential light

radiant light

ambient light

affective light

predication

essential

accidental

accidental

prepositional metaphysics

from (ek)

peculiar (Porphyrian proprium) through (dia)

in (en)

[that for the sake of which (hou heneka)]

Note: The term ‘prepositional metaphysics’ goes back to Theiler (1930), 17–34, and denotes the use of prepositional phrases as expressions of causal relationships in Middle and Neoplatonism. It is introduced into scriptural metaphysics by Philo, see Runia (1986), 171–4; Dillon (1996), 135–9, 160–1, 164, and enters the New Testament canon through the Johannine and the Pauline literature, see Sterling (1997); Sterling (2005), 126–9; McFarland (2017). The use of prepositional metaphysics is therefore normative and canonical for the early Christian authors, who develop their own version thereof, see Dörrie (1969); Pépin (1964), 348–55; McFarland (2015). The most important discussion of the metaphysical use of prepositions in a liturgical and doxological context is Basil’s De Spiritu Sancto, see Robertson (2003). Athanasius’ first letter to Serapion makes extensive use of the doxological formula ‘from (ek) the Father through (dia) the Son in (en) the Holy Spirit’ to stress, through the use of prepositions, the synergistic unity of the divine persons, see Ad Serap. I.14.27–8, 20.26, 24.23–4, 30.39–40, and passim. It is in direct connection to this prepositional formula that Athanasius unpacks the triptych of light–radiance–activity, see Ad Serap. I.20.9–10, 20.19, 20.29–33, 30.33–5. We find the same prepositional metaphysics in Nyssen, see Ad Abl. GNO 47.24–48.8; Adv. Maced. GNO 100.7–11, once more exemplified by the sun/ray model, see C.Eun. I.532. It is therefore no surprise that Nazianzen applies the standard prepositional formula ek–dia–en directly to light in his famous formula ‘light (the Son) from light (the Father) in light (the Holy Spirit)’, see Orat. 31.3.20–1, opposing the

Eunomian interpretation of the same, see Orat. 31.20.13–19. Behind the different constructions of prepositional metaphysics hide different theories of causation. The main thrust of the use of prepositions in late antique Platonism is the fusion of the Aristotelian theory of the four causes with transcendental participatory metaphysics, see Steel (2003). I here depict this harmonization tendency by matching the flame to the efficient cause, the ray to the instrumental cause, the motion of the ray in space to the action affecting the change, and the illumination of space to the end product of light as a natural process. As regards the end product, i.e. ‘that for the sake of which’ a causal process is initiated, Aristotelian (local) teleology identifies it with the final cause (while Platonic global teleology identifies the end of all creation with divine goodness). In natural processes, like the propagation of light, the end product is not external to the cause (like a house is to a builder) but internal, see Metaph. VII.7, XII.3. This explains why in natural substances, like fire, the three out of four Aristotelian causes ‘coincide’, see Phys. II.7 198a25–9. Since illumination is not a real property of the medium but only an epiphenomenal change, the end product of the propagation of light as a natural process is the transmission of light in space. Illumination is pure activity. We must not therefore confuse incidental external changes, like the rearrangement of air particles in space as the ray passes through resulting in the change of atmospheric temperature or the activation of visual perception, with the end product of the propagation of light, i.e. the motion of the ray in space. It is this motion which appears to the senses as illumination (affective light). The eyes perceive the fire particles of the ray, not the particles of the medium; for an explanation of how and why see Appendix B. That means that the final cause of illumination is pure activity, the motion of the ray in space. As regards the instrumental cause, i.e. the organ ‘through which’ a thing is made, this is typically signified with the preposition dia and identified at cosmological level with the logos. Imperial and later Platonism incorporates instrumentality into its theory of causes but regards it as inferior (auxiliary and subordinate) to efficient, paradigmatic, and final causality; see Philo, Cher. 124–30; Proclus, Elements §75; Steel (2002), 77–8. The particularity of pro-Nicene metaphysics is to fuse three out of six Neoplatonic causes into one, identified with the logos, namely: the formal cause relating to immanent forms, like Aristotelian eidē, for which see the next section; the paradigmatic cause relating to transcendent forms, typically identified in Middle Platonism with the ‘thoughts in the mind of God’; last but not least the instrumental cause, that through which the world, and everything in it, was made. Clearly, the apple of discord in fourth-century trinitarian debates is the relation of the logos as instrumental cause to the Father as efficient cause. For example, while the pro-Nicenes (‘homoousians’) argue for hierarchical equipollence following the (Origenian) identification of the instrumental cause (logos) with the paradigmatic cause (sophia); see Origen DP II.1, the anti-Nicenes (‘heterousians’) prefer the language of subordination, remaining closer to mainstream Platonism. The table neutrally depicts the ray as the instrumental cause of illumination. In terms of ‘metaphysics of light’, the efficient (flame), the instrumental (ray), and the final (motion) cause of illumination correspond to the Father, the Son, and the Holy Spirit as three different causal expressions of the one divine reality. One will unpack the metaphysics of light depending on how one understands the relation of the three causes. I have here argued for synergistic co-agency as the typically pro-Nicene interpretation that we find in Athanasius and the Cappadocians.

150

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phusis) was introduced, but now this solar body (to hēliakon touto sōma) has been made ready to be a vehicle (ochēma) for that primordial light (tōi prōtogonōi phōti). Just as fire (pur) is different from a lantern (luchnos), the one having the power to generate light (tēn tou phōtizein dunamin echon), and the other made to light the way ahead (paraphainein) for those who need it, so also in this case the luminaries (phōstēres) have been prepared as a vehicle (ochēma) for that pure, clear, and immaterial light (tōi katharōtatōi ekeinōi kai eilikrinei kai aülōi phōti) . . . Do not let what has been said seem to anyone to be beyond belief, namely, that the brightness of the light (tou photos hē lamprotēs) is one thing and the body that is the substrate of the light (to hupokeimenon tōi phōti sōma) another. First, because we divide all compounds (ta suntheta panta) into the bearing substance (tēn dektikēn ousian) and its accompanying quality (tēn episumbasan autēi poiotēta). Just as, therefore, whiteness (hē leukotēs) by nature is one thing, but a whitened body (to leleukasmenon sōma) something else, so also the things just mentioned, although different (diaphora) by nature, are brought together (hēnōtai) by the power of the Creator. (Hex. VI.2–3 GCS 90.22–91.18 tr. Way, amended)

The passage touches upon a hermeneutical issue that is notoriously ambiguous, namely the question of whether the primordial light should be understood as a physical entity or not. In the context of Gregory studies, some scholars have opted for a spiritual interpretation (primordial light = intelligible light), while others have argued for a physicalist interpretation (primordial light = physical light).¹⁰⁰ I have already discussed the physicalist interpretation when I explained Gregory’s notion of the ‘immateriality’ (aülon) of light in the Apology (§66). It is now time that I present (my version of) its spiritual interpretation. A careful reading of Basil’s passage reveals that behind the two narratives of light lies the fundamental distinction between the physics of light (day four) and the metaphysics that ground it (day one). Day four speaks clearly of the light of the stars as part of a physical chain of causation, instantiated par excellence in the heavenly fire of the stars, for which the celebrated lantern simile serves as an explanatory model. Day one, however, approaches light from a metaphysical perspective. The references to ‘the nature of light’ (tou phōtos hē phusis) in the opening part of the passage, ¹⁰⁰ For the spiritualist interpretation see Hübner (1974), 79–81: ‘alle einzelne Lichter in ihren Prinzipien’; for the physicalist interpretation see Risch (1999), 155 n.136, 200 n.256, 222 nn.350–1: ‘Es wurde also ein anderes als das noetische Licht geschaffen’. Both authors discuss this as part of Gregory’s so-called theory of ‘simultaneous creation’, which is, in my view, misleading. The reference to the seminal study of Hans Meyer (1914), 108–19, is also misleading. Hübner cites Meyer to suggest that the light of the first day is the immanent form of light (‘Summe aller Lichtelemente’, p. 81), while Risch cites Meyer to argue that the spermatic creation of the world does not take place in the mind of God (‘die reale Grundlegung der Welt außerhalb Gottes’, p. 222). Both references are confusing because Meyer regards the elements as material (‘materiel’, pp. 113–14), while he is interested in immanence only as regards the spermatic prefiguration of all things by the divine logos (pp. 109–11). I try to clarify the situation a bit in the following footnotes.

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together with the distinction between matter (hupokeimenon sōma; dektikēn ousian) and form (poiotēta) in the closing part, denote that the exegesis of day one is about light as a property (tou photos hē lamprotēs), as productive power (tēn tou phōtizein dunamin), and as activity (phausis), while the exegesis of day four is about light as a hylomorphic compound (sōma; ochēma; suntheton).¹⁰¹ If indeed there is a reading of Genesis 1:3–5 that allows for light as causal property, as Basil is suggesting, clearly this notion of light cannot be physical but purely immaterial (aülōi phōti). Primordial light (prōtogonōi phōti) means no longer ‘first’ in terms of temporal succession, but ‘first’ in terms of ontological procession. Primordiality signifies, in this interpretation, what light is primarily, principally, i.e. light as such. This is nothing other than a reference to the ideal and eidetic aspect of light, the species of light present in creation, the immanent form or the logos of light.¹⁰²

¹⁰¹ In his remarkable paper, Radde-Gallwitz (2017) comes very close to my analysis but practically denies such a dual aspect interpretation. Radde-Gallwitz argues, correctly in my opinion, that the four elements ‘in their pure form are never perceptible’ (207–8) and that the light of the first day refers to ‘quality without substance’ (210), by which he means, again correctly, light without any ‘originating body’ (211). Radde-Gallwitz, however, assumes that there is no room for a purely elemental, hence imperceptible, light in Basil’s exegesis: ‘it is the phenomenal elements rather than the pure ones that Basil finds in Genesis’ (208). On that view, Basil espouses the ‘oddity’ of a ‘sunless light’, ‘a visible light with no sun’ (210, my emphasis). And since this is fanciful physics, Radde-Gallwitz concludes that ‘Basil is going too far simply in order to save the textual sequence’ (211). One could here pause and ask: if pure elements find no place in Basil’s physical exegesis, why does Basil take so much interest in them (see Hex. II.2, II.3, IV.5)? Or again: if pure elements are not part of Basil’s hexaemeral exegesis, but noetic-angelic creation (or at least an aspect of it) is (see Hex. I.5, II.5), where do pure elements belong, exegetically speaking, in Basil’s scriptural metaphysics? Instead, I believe there is a more charitable interpretation of Basil, one which allows him to remain a consistent thinker and a skilful exegete. This is the dual aspect interpretation, according to which visible light manifests in the universe only on day four. The light of day one is imperceptible to the senses, a metaphysical entity ‘visible’ only to the mind’s eye, see further Appendix B. On this interpretation, Basil’s language of perceptibility in Hex. II.7 refers, strictly speaking, to light’s mechanical and immaterial properties (diffusion, reflection, and refraction), causally explained by the elemental nature of light (photos phusis), which is the sole work of day one, and for which see the following notes. ¹⁰² To be absolutely clear, Basil and Gregory identify the light of the first day with the illuminating power of pure elemental fire, see Basil, Hex. II.7 (photos phusin), VI.2 (tou photos hē phusis); Gregory, In Hex. §§10 (tou puros hē augē), 14 (tou puros tēn phusin), 12, and 65–6 (phōtistikē dunamis). Elemental fire, like all the elements, belongs to the material universe, see Hex. I.7, II.2; In Hex. §14 (aisthēton de to pur). ‘As such’ (auto hekaston; eph’ heautou), each element exists in a simple and unmixed state, see Hex. IV.5; In Hex. §31. The material universe, however, is made up entirely from composite substances, see Hex. IV.5; In Hex. §5, so that ‘none of the visible and perceptible objects is absolutely unique and simple and pure’ (Hex. IV.4). That means that there is no physical instantiation of the four elements in their pure state, i.e. of the four elements as such. That is the reason why Basil clarifies that the four elements in their unmixed state exist only in thought: hōs prōta stoicheia tōi logismōi theōreitai (Hex. IV.5). In the physical universe, each element exists only in some form of admixture with the other elements, which is the reason for the communicatio idiomatum between neighbouring elements, see Hex. IV.5; In Hex. §55. Basil and Gregory make quite explicit, however, that from a metaphysical perspective elemental fire should be theorized in a pure and unmixed state, see Hex.VI.2; In Hex. §§10, 65, though they both clarify that from the perspective of physics there could never have been such an unmixed state in the material universe, see Hex. II.7 (egkekramenon); In Hex. §12 (ton aera tē flogi kataugazousa). This compels the intelligent reader to enquire after the ontological status of elemental fire as such, following a path of enquiry first initiated in Tim. 51b6–52d4. Clearly, fire as such cannot be a transcendent form, because it belongs to material creation. But it cannot be a material entity either, since the elements are never found in their pure, unmixed state in the physical

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Gregory, following Basil’s lead, expounds the same spiritualist interpretation (§65) right before the physicalist interpretation (§66) of the immateriality of light. §65 of the Apology is a reflection on the different uses of the biblical language of light: Gen. 1:3–5 speaks of one light (hen phōs) in the singular (tēi enikēi phōnēi), to denote light ‘in the general sense’ (tōi genikōi logōi), i.e. ‘the whole of light’ (to pan phōs); Gen. 1:14–19 speaks of many lights (phōta) to denote the phenomenal light (ta phainomena), which is characterized by great variety (diaphoran). The language of the one and the many, identity and difference, the general and the particular, is a clear indication that Gregory too subscribes to the double hermeneutics of hexaemeral light: a metaphysical interpretation of the light of day one as the first (hierarchically) immanent form of creation; and a physicalist interpretation of the light of day four as the manifestation of the first immanent form in the material universe.¹⁰³

universe. The only possible alternative is that the four elements in their pure, unmixed state are forms immanent in creation. These ontological entities are known under various names, like ‘enmattered forms’ (enula eidē) or ‘forms-in-matter’ (eidē epi tēi hulēi), to stress their mixed ontological status, as logoi to stress their role as rational-formative principles, and as ‘seminal reasons or causes’ (spermatikoi logoi) to stress their dynamic manifestation in time, see comprehensively (albeit the overstressed Anaxagorean lens) Tzamalikos (2016), 542–54, 649–90, 750–81, 933–54, 1254–8, 1401–10. As regards their ontological function, immanent forms inhere in the material substratum that they act upon and configure into a sensible object. They are thus ontologically inseparable from their particular spatiotemporal instantiations, but epistemologically separable from them (as the form of every hylomorphic compound). That means that immanent forms are separable from the matter that underlies them only in thought, a feature that distinguishes them from transcendent forms, see Chiaradonna (2007); Karamanolis (2009). Immanent forms as the spermatic logoi of things should not be confused with the universal spermatic logos of creation permeating the whole nature and guiding creation to its end, see In Hex. §§9–11, 16, nor with the primordial opposite pairs of qualities that are the conceptual ingredients of the idealist theory of matter, see In Hex. §§7, 17. Elemental fire as the formative principle of all fires in the universe is the first particular manifestation of the universal logos immanent in creation, arranging the conceptual ingredients of materiality (shape, volume, weight, density, etc.) in a particular way, according to the spatio-temporal conditions that fire finds itself in. The arrangement according to the surrounding spatio-temporal conditions is the process described by Gregory as the diakrisis and sundromē of fire in the universe in the three days that precede the appearance of the heavenly bodies, see In Hex. §65–7, while the particular arrangement of fire in every case reveals the particular logos of every fiery body, see In Hex. §§69–71. ¹⁰³ Sections §§65–74 of the Apology expound on the difference between the creation of light as elemental ‘power’ (hē purōdēs kai phōtistikē dunamis tēs ktiseōs) or ‘nature and power’ (he phōtistikē phusis kai dunamis) in day one, and the manifold partition (diairesis)—viz. instantiation—of this power in the phenomenal world in day four (ei de pros ta phainomena blepoi tis, pollen tēs phōtistikēs dunameōs diaphoran en tois ousi katopsetai). Light as elemental power is an immaterial entity, see Porphyry, Sentent. 42 Lamberz 53.9, namely a property of varying intensity, see Pritchard (1990), 190–1; Zeyl (2000), xxxix, able to produce a physical change in the world, see Chiaradonna 2007, 48. This is exactly the same as Basil’s doctrine of primordial light as property. Hence Gregory’s adherence to the dual aspect interpretation: from a unitary-metaphysical perspective (phōs), the work of day one is the creation of the eidetic aspect of light (phōtistikē ousia, logos), light as pure power (phōtistikē dunamis), §§10–12; from the perspective of its manifold instantiations (phōta), light forms autonomous physical systems, namely the heavenly bodies (asteres), occupying different places in the physical universe (oikeian thesin), radiating light in different intensities (pollēn diaphoran; apeirous diaphoras), §§66–74. The transition from the metaphysical to the physical aspect of light occurs in §65. From then on, Gregory’s contemplation becomes temporal, indicated by the katarchas in the opening sentence of §66 GNO 73.23.

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3.4.2 Back to Origen This dual hermeneutics of light is, of course, so subtle and suggestive that it would entirely elude the untrained multitude. Not so with the erudite. A dual approach to light, both metaphysical and physical, would be totally in accord with Basil’s blending of exegesis with advanced philosophical material for the sake of the few. It would also be eagerly anticipated and favourably received by Gregory’s learned audience. If one feels that the spiritualist interpretation maybe comes too close to the allegorical tradition, one would not have been deceived. There is strong textual evidence to suggest that the dual aspect interpretation has its roots in PhilonicOrigenian exegesis. The first piece of evidence concerns the apparent narrational anomaly of light shining in the world before the material bodies that generate it were introduced—a point raised by Petrus, echoing, as we saw, the voice of Celsus, Galen, and, in all likelihood, Julian. In a passage from the De principiis preserved by the Cappadocians in the Philocalia, Origen gives several examples of allegorical interpretation of Genesis, the first of which aims to answer the aforementioned narrative challenge. For who possessed of understanding will suppose that the first and the second and the third day, evening and morning, happened without a sun and moon and stars? And that the first day was as it were without a sky? And who is so foolish as to suppose that God, after the manner of a human farmer, planted a paradise in Eden towards the east, and placed it in a visible perceptible tree of life, so that one tasting of the fruit by bodily teeth would obtain life, and again that one could partake of good and evil by chewing what was received from the tree there? And if God is said to walk in the paradise in the afternoon, and Adam to hide himself behind the tree, I do not think that anyone doubts that these figuratively indicate, through apparent narratives and through things that did not happen bodily, certain mysteries. (DP IV.3.1 tr. Behr, italics in original)

Origen’s solution to the hermeneutical challenge is prima facie unsatisfactory. He appears to disregard entirely the narrative sequence of the text by directly contesting that there could ever be meaningful talk of ‘day’, ‘evening’, and ‘morning’ without the existence of the sun, the moon, and the stars that cause them. This is an embarrassing stance, to say the least, for an exegete who has built his whole career on the role of textual accuracy and the principle of akolouthia as the fundamental guideline for the interpretation of Scripture.¹⁰⁴ Alternatively, there is something else going on in the background, something that proves Origen to be

¹⁰⁴ As already noted, the principle of akolouthia goes back to Stoic hermeneutics and is given hexaemeral expression in Philo, Opif. 28. The widespread view that Alexandrian exegesis is indifferent to the text relies on a superficial reading of the source material. On Origen’s strong commitment to the

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consistent with his own exegetical principles. This something could be, precisely, an interpretative approach that understands the events of the first three days in a non-physicalist manner and the events from the fourth day onwards in a physicalist manner. In this scenario, there would be no physical day, evening, and morning, before the creation of the heavenly bodies. The meaning of the words would have to be different, signifying, for example, tropes of time measurement, a purely metaphysical enquiry. Since we do not have the relevant part from Origen’s lost Commentary on Genesis this suggestion remains speculative. But not every speculation is unwarranted. If we allow ourselves to read the Cappadocian exegesis back into the Origenian passage, it is possible to maintain that Origen interprets the light of the creation narrative in a dual perspective: day one denotes the intelligible aspect of light; day four its physical instantiation. What grounds do we have for such a retrospective projection of Cappadocian interpretation? We have compelling evidence from the newly discovered Munich collection of Origen’s Homilies on the Psalms that the Cappadocian metaphysics of light goes back to Origenian material. We simply need to recall that the hermeneutical foundation of Basil’s dual approach is the key distinction between the primordial light of day one (prōtogonon phōs) as pure substance (phusis), power (dunamin), and activity (phausis) and the luminaries of day four that are its bodily bearers (phōstēres). Recall further that this distinction is a direct adaptation of Origen’s exegesis of Psalm 73:16, where Origen distinguishes between the primordial light of day one (prōtotokon phōs) as a pure activity (phausis) and the intelligible cause of sensible light (ontōs phōtos; hoper epoiēse tōi kosmōi phōs), and the creation of the sun (hēlios) and the heavenly bodies on day four as the physical bearers of this light (phōstēres).¹⁰⁵ That clearly shows what I have already alluded to multiple times, namely that the Basilian metaphysics of light is a later adaptation of a genuinely Origenian exegetical theme. It also means that the projection of Basilian exegesis back into Origen is no anachronistic interpretation at all. It is a mere interpretative strategy that helps us perceive the lost link between the passage from the De principiis and the Homilies on the Psalms. The missing link is the dual interpretation of hexaemeral light, an interpretation that must have been the subject matter of the Commentary on Genesis and which can still be recovered in its basic outlines from the mark it left on Cappadocian exegesis.¹⁰⁶

exact interpretation of the letter of the text in the specific context of hexaemeral hermeneutics see Hom. Ps. 73, III.2–3 GCS 253–6; on the principle of akolouthia in the same context see Hom. Gen. I.1 Baehrens 1.14–15. ¹⁰⁵ See Hom. Ps. 73, III.2–3 in GCS 255–6 and section 3.1.1 above. ¹⁰⁶ In a fascinating introduction to Origen’s De principiis, Behr (2017) has recently argued for the dual aspect interpretation (sub specie aeternitatis–sub specie temporis) as the hermeneutical key that unlocks Origen’s work on first principles. If my argument is correct, it concurs with Behr’s thesis and finds further support in it.

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3.4.3 Philonic Beginnings Does the dual interpretation of hexaemeral light originate with Origen or can we trace it further back in the tradition? I would suggest Philo as the original source of inspiration. In the De opificio we are told that the primordial light (day one) is the intelligible paradigm of the physical light of the heavenly bodies (day four). The light of the sun, the moon, and the stars is, in other words, the visible image of the archetypical, intelligible light of creation (§§29–33, 55). We have here the first instance of the double hermeneutics of hexaemeral light, metaphysical and physical. In the exegesis of day one we are given a metaphysical analysis of light: it is the type–token relation that connects the intelligible light and its sensible instantiations.¹⁰⁷ In the exegesis of day four the same type–token relation is repeated, but the emphasis is now on the physicality of light:¹⁰⁸ light is the most excellent of all sensible beings (tōn ontōn ariston); it is, further, the guiding principle (organon), necessary condition (chreios ho ophthalmos phōtos), and most beautiful object of vision (pagkalōi kai theoeidestatōi), triggering philosophical and scientific investigation (hupo tou photos anō parapemphteisa hē horasis); it is finally the substance of the stars (phusin asterōn) causing illumination (tou phōsphorein), producing the measures of time (metra chronou), and generating number (arithmou phusin).¹⁰⁹ True, the Opif. does not give us the Philonic physics of light. It adopts a metaphysical approach to creation, echoing strongly the Timaean approach to the physical world, while the physics of light needs to be retrieved from the rest of the Philonic corpus through laborious study.¹¹⁰ But the principle of light’s hexaemeral exegesis is already established here: day one denotes light’s intelligible aspect and day four its sensible aspect.¹¹¹ The Opif. also gives a further hint, though this is a more suggestive one. The metaphysics of light appears to unfold on a double plane. On the one hand, the intelligible light fulfils a type function as the archetypical light of creation (§29 noēton paradeigma). On the other hand, it also gives a token function as the image, itself, of the intelligible logos (§31 theiou logou eikōn), who is, in turn, the

¹⁰⁷ See Opif. 29 (asōmaton kai noēton paradeigma); 30, 33 (noēton phōs); 31 (pēgē tōn aisthētōn asterōn). ¹⁰⁸ See Opif. 55 (pros dē tēn tou noētou photos idean ekeinēn apidōn . . . edēmiourgei tous aisthētous asteras). ¹⁰⁹ See Opif. 53–5. ¹¹⁰ See, on this, the programmatic (but alas unfinished) study of Valentin Nikiprowetzky (1989). There is still no systematic study of the physics of light in Philo. As things stand, the best entryway are the comments of Runia (2001), ad loc. (§§29–35, 53–62). ¹¹¹ See Nikiprowetzky (1989), 9–10, 13–14. As Kugel (1998), 72, notes, a similar interpretative approach is also found in other Jewish authors (Jubilees 2:2 and the Qumran Hymn to the Creator 11QPsa), who tried ‘to resolve the apparent contradiction between the creation of light on the first day and the creation of the sun and the moon on the fourth by suggesting the first day’s creation of light was more theoretical than actual’. Runia (2001), 135, remarks that these parallel interpretations come ‘strikingly close to what Philo intends with his “intelligible cosmos” ’ (with reference to Jubilees 2:2).

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realm of noetic archetypes or ideas (§20 oud’ ho ek tōn ideōn kosmos allon echei topon ē ton theion logon; §24 noēton kosmon ē theou logon). The double classification of primordial light as token (of the logos) and type (of all sensible light) has troubled Philonic exegesis, which regards Philo’s move as a hermeneutical curiosum.¹¹² If, however, the Cappadocian dual interpretation is a distant echo of a hermeneutical tradition initiated by Philo and continued by Origen, the curiosum might finally find its proper explanation. One only needs to understand primordial light as the first manifestation of an immanent form in a Platonic ontological universe in order to allow for light’s dual ontological status as both type (since form) and token (since image of a transcendent paradigm).¹¹³ An indirect confirmation of this suggestion comes from the parallel exegesis of the double creation of the human being (§§25, 67–76, 134–5). From the viewpoint of Gen. 1, the human being is approached in its intelligible aspect (§69 nous). Gen. 1:26–7 denotes the creation of the generic human being (§76 to genos anthrōpon), i.e. the human being in its noetic-eidetic aspect (§134 idea tis ē genos ē sphragis, noētos, asōmatos, aphthartos phusei). According to a prevalent view, Philo here means the human species or humanity at large.¹¹⁴ From the viewpoint of Gen. 2, however, the human being is approached in its sensible aspect (§134 aisthētos). Gen. 2:7 denotes the creation of the particular human being (§135 epi merous anthrōpou) as a hylomorphic entity (suntheton), composed of form and matter (ek te geōdous ousias kai pneumatos theiou) or of mind (psuchēn, dianoian) and body ¹¹² See Runia (2001), 168 (on §31), who decides to play the joker card: ‘Perhaps the text is corrupt.’ ¹¹³ Since the ontological status of light is directly dependent on the ontological status of the logos, Philo’s doctrine of the logos holds, here, the key to solving the puzzle. This is where the distinction of Wolfson (1962) between (transcendent) ideas ‘in the mind of God’ and (created) ideas ‘outside the mind of God’ comes in handy, especially since created ideas are understood as ‘species’ (eidē) and ‘the genera of the particular objects’, i.e. immanent forms (pp. 204–17). The former (transcendent forms) are theorized as intelligible paradigms (ideai) of things, the latter (immanent forms) as intelligible causes (dunameis) of things (pp. 217–26). To these two aspects of Philonic intelligible objects correspond two aspects of the Philonic logos: the totality of the intelligible paradigms is the (uncreated) transcendent logos, while the totality of the intelligible causes is the (created) immanent logos. The latter stands in a relation of ‘image’ or token to the former (pp. 226–40). Though the methodology of Wolfson has been questioned—see Runia (1984)—his grand systematization between the two aspects of the logos, transcendent and immanent, still stands, see Runia (2001), 142–3. Dillon (1996), 159, repeats the same systematization by distinguishing between (immanent) ‘ideas in activity’ and (transcendent) ‘ideas at rest’. The ideas in activity function as the ‘creative principles of the physical world’ and are compared to the Stoic spermatic logoi. The dual ontological scheme of transcendence and immanence holds, in my view, the answer to the question of the ambiguous relation of light to logos. The light of the first day is the image or token of the transcendent logos, while the same light is the manifestation par excellence of the immanent logos. Thus, the identification of the light of the first day with the first immanent form (hence, by extension, with the first power of the logos and thus, synecdochically, with the immanent logos itself) solves the tensions as regards the relation of light to logos in the Philonic corpus. Interestingly, Wolfson (1962), too, understands the primordial light as the immanent form of light, including the light of the first day, in his examples of Philonic universals (p. 211). As van Kooten (2005a) has shown, the connection between intelligible light and the doctrine of the logos together with the dual interpretation of light, intelligible and sensible, can be also traced in the Johannine literature. If so, Origen and his students derived the hexaemeral hermeneutics of light from a reading of Genesis 1 through Philonic and Johannine premises. ¹¹⁴ See Runia (2001), 242–3 (§76) and the overview of interpretations in pp. 322–3.

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(sōma). Gen. 1:26–7 then refers to the human eidos immanent in creation and Gen. 2:7 to every particular physical instantiation of the human species. And since the human being of Gen. 1:26–7 is at the same time the image of the image, i.e. of the divine logos, and the archetype of every individual human being, it enjoys the same dual ontological status of the light of the first day as the token of the logos and the type (or immanent logos) of the members of its class. Philo gives us a further hint that he theorizes the human being of Gen. 1:26–7 in terms of an eidetic universal or immanent form: he uses the technical jargon of genus and species (§76 genos—eidē, §134 idea tis ē genos).¹¹⁵ I may be here striding a bit too fast over a series of delicate discussions in Philonic hermeneutics.¹¹⁶ Be that as it may, the hard fact remains that there is an undeniable analogy between the double ontological status of light and that of the human being in the Opif., an analogy that places light and the human species in a token relation to the logos and a type relation to their particular physical instantiations.¹¹⁷ It is the same relation that we also find in the Cappadocian exegesis.¹¹⁸ If my readings of Philo and Origen are plausible, we can establish a common thread of hexaemeral hermeneutics of light from Philo to Gregory through Origen and Basil. Initially faintly visible, a certain theme surfaces gradually as the hexaemeral exegesis proceeds over the centuries. It is the theme of light as the immanent manifestation of the logos in creation, the light of the logos as it is revealed in and through the material world. Throughout the first four centuries of Jewish-Christian hexaemeral exegesis the idea was preserved that the light of the first day is a lux intelligibilis. Not, however, as a transcendent idea separate from the physical world, but as an immanent form distinguishable from its physical ¹¹⁵ See the helpful discussion and further evidence by Tobin (1983), 112–17, with the necessary corrective of Runia (2001), 242–3 (§76), however, that the genus–species relation does not mirror the distinction between (transcendent) eidos and (immanent) idos, as Tobin thinks (p. 117), but belongs to the same ontological class of immanent species. ¹¹⁶ For the hermeneutical difficulties see the already mentioned works of Tobin (1983) and Runia (2001). For my interpretation of these ambiguous passages, I have followed as hermeneutical guideline the metaphysical scheme provided in Heres 231: Gen. 1:27 signifies the individuated human intellect (ton kath’hekaston hēmōn noun), which is the image of the image (ouchi eikona theou alla kat’eikona), i.e. a first ontological remove from the universal logos (archetupon [logon] ton huper hēmas) and a second remove from the supreme divine intellect (triton tupon apo tou pepoiēkotos). My reading of the Opif. in light of the Heres presupposes a unitary reading of the Philonic corpus which seems opposed to the recent thesis of Niehoff (2018), according to which Philo changed his philosophical language when he visited Rome, turning from the Platonism of the Allegorical Commentary (in which the Heres belongs) to the Stoicism of the Exposition of the Law (in which the Opif. belongs). Such a thesis does not harm my argument. All I am claiming here is the Philonic lineage of an immanentist metaphysics of creation. Niehoff (2018), 93–108, forcefully argues in favour of my claim. ¹¹⁷ Reinforced by the explicit ontological similarity between the luminous stars and the human being, who according to Opif. 73 both belong to the class of rational animals (zōia noera). The analogy of light with the human being is the main theme of Origen’s first (hexaemeral) Homily on Genesis. It remains constantly in the subtext of the hexaemeral literature, emerging as an explicit hermeneutical theme in texts directly influenced by Basilian exegesis, see the third of the hexaemeral homilies appended to Basil’s Hexaemeron, the De Paradiso GNO 75–84; Severian, Cosmog. I.5–6 PG 56:436. ¹¹⁸ Maintaining the Philonic dual scheme not only for the creation of light and the world but also for the creation of the human being, as thoroughly argued by Zachhuber (2014), esp. 145–74, 239–41.

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manifestations only in thought. This conceptual distinction cum ontological connection between intelligible and sensible light is what the dual interpretation of day one and day four of the creation narrative aims to express. The Cappadocian language of the ‘immateriality’ of light captures precisely this duality of hylomorphic metaphysics as hermeneutical ambiguity, allowing for a spiritualist and a physicalist interpretation of the light of creation. Behind this dual interpretative strategy hides more than just an apologetic response to erudite critics of Scripture contesting the logic of the creation narrative. On the one hand, the hexaemeral physics of light defends the coherence of the scriptural narrative and puts the entire ancient scientific arsenal at the service of biblical exegesis. On the other hand, however, the hexaemeral metaphysics of light pushes forward an agenda of its own, insisting on a particular approach to light that is intrinsically incarnational. From Philo to Gregory, hexaemeral exegetes suggest that the study of physical light reveals something about the nature of the logos at work in the world. If this logos loves to hide and at the same time disclose itself through its works, the metaphysics of light shows that the works of the logos are never cut off from the physical world. Sure, the formative logos of light is an intelligible nature. But it is the beauty of its physical manifestation, the plain beauty of light shining in the world, that captures our imaginative attention and kindles the spark of genuine enquiry in our hearts. We may truly know light only in its intelligible form, as a lux intelligibilis. But light creates that primal sense of wonder in the first place only because its logos is embodied, since immanent forms are qualifiers of matter and therefore always inhere ‘in’ bodies. The lux intelligibilis of creation is the light of the first day in its intelligible aspect, the primordial manifestation of the logos in nature. This is not merely an individual logos but first and foremost an individual manifestation of the universal logos of nature, since creation, the whole of it, is the place of the disclosure of the logos. The enquiry into the nature of light teaches us that if light’s innate logos is always embodied, its disclosure must be inherently incarnational. This incarnational metaphysics of light is the particular theological grammar of light’s hexaemeral hermeneutics.

Conclusions ‘He was the true light that enlightens every man coming into the world’—yes, the Father. ‘He was the true light that enlightens every man coming into the world’—yes, the Son. ‘He was the true light that enlightens every man coming into the world’—yes, the Spirit. These are three subjects and three verbs—he was and he was and he was. But a single reality was. There are three predicates—light and light and light. But the light is one, God is one. This is the meaning of David’s prophetic vision: ‘In thy light we shall see light.’ We receive the Son’s light from the Father’s light in the light of the Spirit. (Gregory Nazianzen, Or. 31.3 tr. L. Wickham and F. Williams) ‘What is light?’ This is the question that the classic debate over the ‘metaphysics of light’ curiously failed to ask and that this book set out to explore regarding early hexaemeral literature. One can imagine several reasons for this gap. Almost contemporaneous with the ‘linguistic turn’ in twentieth-century philosophy, the term ‘metaphysics of light’ was used from its conception as an effort to restate traditional metaphysics in linguistic terms. Instead of pursuing the question of the nature of light from a historical perspective, twentieth-century scholars focused on the meaning of light as a classical analogy of being in traditional metaphysics, culminating in the talk of God as light from Plato and Plotinus to Scripture, especially, but not exclusively, Johannine literature and its Jewish-Christian mystical and metaphysical exegesis. The debate was doomed to a standstill, of which both sides of the debate were by no means unwarned: in dividing themselves over the use of light language (literal, analogical, or metaphorical?) in traditional theological metaphysics, modern scholars forgot to investigate the conceptual foundation of all metaphysical light language, the concept of light itself. To remedy the mistake of the past, this book has focused on a particular body of early Christian literature, the so-called ‘hexaemeral’ tradition from Philo and Origen to the Cappadocian brothers Basil of Caesarea and Gregory of Nyssa. The choice of source material was justified by a twofold rationale: first, this body of literature belongs to an ancient tradition that understands the Torah, with the biblical creation narrative at its head, as the most perfect articulation of natural philosophy. In this tradition, known for pedagogical purposes as ‘Alexandrian’, the hexaemeral narrative of Gen. 1 contains in a nutshell the most fundamental axioms of Moses’ philosophy of nature, comparable to the Platonic Timaeus,

The Metaphysics of Light in the Hexaemeral Literature: From Philo of Alexandria to Gregory of Nyssa. Isidoros C. Katsos, Oxford University Press. © Isidoros C. Katsos 2023. DOI: 10.1093/oso/9780192869197.003.0005

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which was regarded by many ancient philosophers, and is still regarded by many today, as containing in a nutshell the basic principles of Plato’s philosophy of nature. Secondly, the legacy of Philo and Origen in the hexaemeral writings of Basil and Gregory was due to become tremendously influential in the subsequent patristic and scholastic tradition through the mediation of the works of the anonymous author known as ‘Dionysius the Areopagite’, Maximus the Confessor, and John of Damascus in the byzantine East, and Ambrose, Augustine, and Eriugena in the Latin West, reaching down to the two medieval pillars of Eastern and Western theology, Gregory Palamas and Thomas Aquinas. Whatever the meaning of ‘light’ in Christian theological metaphysics, it hinges upon the concept of light of Gen. 1, which lays the foundation of all scriptural light language, whether literal, analogical, or metaphorical. For this reason, in the introductory part of this book I chose to redefine the term ‘metaphysics of light’ much more modestly than before, hence therapeutically. For the purposes of my enquiry, the proper subject matter of the metaphysics of light is the answer to the question: ‘what is light?’ in a scientifically informed (namely physical or metaphysical) historical context. Only after the metaphysics of light in its proper sense has been explored may one enquire meaningfully into the ‘metaphysics of light’ in an extended sense, i.e. into the use of the term ‘light’ in an implied (analogical, metaphorical, or catachrestic) sense. In redefining the research question, the primary aim of this book has been to bring the historical quest for the meaning of light back to its basics. There are reasons why one might want to resist the return of the metaphysics of light to its basics. One might in fact claim that the enquiry into the nature of light makes little sense in a premodern context, more precisely that the nature of light is to serve merely a functional purpose and that therefore the premodern mindset has no interest in, let alone the conceptual apparatus for, an investigation into the nature of light for the sake of understanding light itself. The key influence behind this approach to ancient sources is Aristotle’s argument for the discussion of light in the De anima II.7, which goes like this: Vision is moved by colour as its special object; Colour is not visible without light; Hence, the enquiry into the nature of vision requires a preliminary enquiry into the nature of light. (418a11–15; 418a24–b4)

Aristotle’s approach, which was never meant as a general enquiry into the nature of light but was clearly limited by the scope of his enquiry into the nature of perception as the primary objective of the De anima, gave rise to a spurious dilemma in the modern history of science. Comparing ancient and modern optics, historians of science came to distinguish between premodern ocular theories,

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which approached light as a merely functional element of vision, exploring how light renders things visible, and modern physical theories, which study the basic properties that light exhibits as it interacts with physical objects (especially reflection and refraction). While the ocular theories subordinate light to sight and are therefore ‘oculocentric’, the physical theories examine the physical properties of light independently of their effect on vision for the sake of understanding how light interacts in nature and are therefore called ‘luminocentric’. This distinction between ancient oculocentric and modern luminocentric or physical optics became mainstream in contemporary textbook and historiographical approaches, culminating in the view that the history of optics, as scientific discipline, can be captured by a grand narrative of the passage ‘from sight to light’. The turning point in this narrative is the dawn of modern science in the seventeenth century, which thus signifies the passage not only from premodern natural philosophy to modern science but also to a broader paradigm change in the Kuhnian sense. Needless to stress that the premodern (pseudo-?)scientific paradigm comprised the classical literature of the ‘metaphysics of light’ (in the extended sense), including the patristic corpus. If this interpretation is correct, the debate over the ‘metaphysics of light’ did not miss much in eschewing the enquiry into the nature of light. Instead, it precluded from the discussion a question that would have been misleadingly anachronistic if asked directly and unqualifiedly. The question that was justifiably excused was: ‘what is light?’ This would have been an ingenious response to the research question of this book, one that would actually make the rest of this study redundant. It would also align perfectly the traditional debate over the ‘metaphysics of light’ with the prevalent view in current historiography of light for a perfect match of two complementary narratives in the history of philosophy and science. The only issue is that this seemingly perfect match comes with three—not at all tiny— wrinkles. As Aristotle himself makes explicit in the De anima II.7 and in the De sensu 2, his ‘oculocentric’ approach to light, if indeed we may call it such, is opposed to the model of Empedocles and of the Timaeus. If Aristotle’s model can be called ‘oculocentric’, the Timaean model would classify as ‘luminocentric’ because the eye is explained as a function of light and by analogy to a lamp. In this model, vision is the result of the interaction of two fires (the internal fire of the eye and the external fire of any source of illumination, most notably the sun) and their comingling light rays (sunaugeia model). In subsuming ancient theories of light to the explanatory principles of Aristotle’s oculocentric model, the modern narrative marginalized, if not entirely neglected, the opposing luminocentric principles of the Timaean model and the literary tradition that followed them. First gap. Secondly and crucially, one textual tradition that followed the luminocentric approach of the Timaean model is the hexaemeral tradition. From Philo to Origen and the Cappadocians, we observe the formation of a (Jewish-)Christian community of readers that use the book of Genesis and the Timaeus. This should

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not be understood as a slavish incorporation of Timaean doctrines in scriptural exegesis, nor as a creative reinterpretation of the Timaeus in a scriptural context. If one suggested to Philo or an early Christian thinker that they followed Plato in their reading of Scripture, they would retort that it was the exact opposite: Plato borrowed his doctrines from Moses. We might find this form of ancient historiography curious, but we do not need to dismiss it as entirely absurd. We can understand it, charitably, as a form of acknowledgement on the part of early hexaemeral exegetes that they shared with the Platonists several (though not all) metaphysical intuitions about the world. One such fundamental intuition was that vision is causally explained by fire and its light. In entirely ignoring the hexaemeral tradition, modern historiography neglected not only the luminocentric model of mainstream Platonism but also that of mainstream Christianity. Second gap. Thirdly and finally, even Aristotle’s account of vision understands light as causally independent of vision and colours. Light is a power of fire, which comes and goes together with the presence of fire (or aether) in the transparent medium (De an. 418b13–19; Sensu 439a21–2). In subordinating light to sight, the narrative ‘from sight to light’ failed to take into consideration Aristotle’s most important hint about the nature of light: that it is connatural with fire. It therefore failed to notice the existence of a superabundant physics of light in the ancient sources, which is, as a careful reading of Aristotle also indicates, the physics of fire. Third gap. Being swayed by the premises of seventeenth-century science, the modern oculocentric narrative failed to grasp the most fundamental principle of ancient theories of light, namely that in the ancient world light was theorized as a natural power or property of fire and that therefore in order to understand the ancient concept of light we need to start with the nature and properties of the fire that produces it. Fire, however, is one of the four elements and as such plays a fundamental role in the elemental physics of every ancient school of thought. In limiting the scope of ‘luminocentrism’ to modern physical optics, i.e. to how light interacts with physical objects through reflection and refraction, the modern textbook approach lost sight of how the ancients understood the question: ‘what is light?’ They understood it first and foremost as an enquiry into the nature and properties of light as such, i.e. as an enquiry into the nature of fire as a physical substance and its natural property of illumination. Light’s optical properties of reflection and refraction depend upon (emerge from) fire’s basic natural properties. In challenging the oculocentric narrative of modern historiography and in situating the ancient physics of light in its proper historical context, I argued in the first chapter of this book that it is absolutely essential to ask the question ‘what is light?’ with regard to the ancient sources. In eschewing the question, the debate over the ‘metaphysics of light’ was built on shaky grounds. The most important contribution of the return to the metaphysics of light in its proper sense is to become once more aware that the answer to the question ‘what is light?’ in premodern thought lies in the ancient physics of fire. This raises two

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further questions for hexameral literature: first, why would a reader of Scripture bother with ancient physics at all? Second, how does the ancient physics of fire help explain the nature of light? I discussed the two questions in order in the second chapter of this book. Regarding the first question, many contemporary readers of Scripture would find it at least odd to employ relativity theory or quantum physics in explaining the creation of light and the stars according to the book of Genesis. That is not to say that a contemporary scientist may not (privately) believe that God created the universe and (professionally) theorize light according to the latest state of knowledge in contemporary physics. But such a scientist would not also think that Moses already shared the basic intuitions of relativity and/or quantum theory, nor would a fellow theologian make recourse to the latest scientific state of knowledge in order to understand the biblical creation narrative, let alone defend it to erudite critiques of Scripture. Echoing Barth and Bultmann, contemporary scientists and theologians prefer to keep their business separate and open up shop in different corners of the academic market. It was not so with early Christian thinkers, who felt quite at ease in merging science with scriptural exegesis. It is important to understand why. The first thing to note is that hexaemeral authors are embedded in a cultural milieu which, as already mentioned, thinks there is a perfect correspondence between Scripture and philosophy. This ancient practice was certainly nurtured by the Hellenistic curriculum, also continued in late antiquity, which understood the encyclical studies, logic, physics, and ethics as organic parts of a comprehensive and continuous body of knowledge culminating in theological metaphysics. Philo’s treatise De congressu and Origen’s third section of the Prologue to his Commentary on the Song of Songs are two textual witnesses of this tradition, which is omnipresent in the Alexandrian school of thought. This reading practice, however, only tells us that ancient readers of Scripture used physics in their hexaemeral exegesis. It does not tell us why. We begin to understand why, once we situate hexaemeral exegesis in the broader context of late antique cosmological discussions. We then observe a fierce critique by eminent Platonists, such as Galen and Celsus, aimed directly at the biblical creation narrative and its exegesis. The gist of this critique was that the Jewish-Christian metaphysics of creation, albeit a better option than material atheism, was deficient compared to its Platonic counterpart with its elevation of matter to the rank of a causal principle. Behind the attack lay a critique of the Christian signature doctrine of the creatio ex nihilo: if the world is the product of an omnipotent biblical creator God, the recourse to material causality as explanatory principle of the world became redundant. Material causality, however, was absolutely essential from a Platonic perspective in order to safeguard the divine Demiurge from any responsibility for natural causes of evil. In other words, in several versions of late antique Platonism, material causality was a necessary corollary of absolute divine goodness coming at the expense of divine omnipotence. Judging from the force of Porphyry’s and Julian’s anti-Christian critique, we

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may easily understand why Origen, Basil, and Gregory expended so much effort in defending the role of a material principle in hexaemeral metaphysics. Since the debate was about the role of matter as causal principle, the Christian defence had to produce a theory of material causation. Since light was the first work of creation, the Christian theory of causation had to start with light. For the hexaemeral authors there can be no causal principle other than God. This is a theme that remains constant from Philo to Basil. It must have been Origen who first came up with a full Christian response to the Platonist charge: God did not create the world randomly, as a manifestation of an arbitrary divine will. The world exhibits regular patterns, the natural kinds and the laws that govern them, which betray a causal structure behind the sensible phenomena. God is utterly immaterial, but matter is not a principle independent from God precisely because it enables the manifestation of the regularity that makes the world a wellfunctioning whole. While Platonists chose to keep matter apart from God to exonerate the divine Demiurge from natural evil, the Christians chose to drive matter back to God to attribute to the divine Demiurge the order and beauty of the visible world. Since matter could not be theorized anymore as an independent causal principle, Origen came up with the ingenious suggestion, of indirect Platonic inspiration, that matter could nevertheless function as an auxiliary cause, a necessary instrument that enabled the divine Demiurge to manifest his creative genius, his logos. It is the artistic divine logos that chooses the ingredients of the world, the sensible qualities, in order to produce out of infinite possible combinations this universe as the best possible functioning whole. The heart of the hexaemeral anti-Platonist defence is this: contemplation of nature is contemplation of the divine logos at work. This work starts with the simplest elements of nature and culminates in the human being as the most complex work of nature. But this is precisely the narrative order of the biblical creation narrative. Genesis 1 then contains in the narrative form of ‘six days of creation’, the hexaemeron, Moses’ contemplation of nature. If the purpose of the hexaemeron is contemplation of nature and contemplation of nature reveals the demiurgic divine intelligence, the logos of God at work, each day of creation manifests a demiurgic aspect of the divine logos. The creation of light being first, light is the first manifestation of the divine logos at work. In exploring the nature of light, the scriptural readers contemplate God qua Creator. Reading Scripture is contemplative reading and Scripture starts with the hexaemeral contemplation of nature. Without a deep appreciation of the laws of physics, we cannot even begin to understand God as Creator. This is why Scripture begins with Moses’ contemplation of the physical world, the first object of which is light. The natural elements were theorized as constituent components of the physical world in ancient physics. Hexaemeral physics produces its own version of the theory of the four elements (fire, air, water, and earth) and their natural properties. It is a theory of Timaean inspiration, based on a ‘scientific’ reading of the biblical

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creation narrative. The starting point of hexaemeral physics is that the four elements were in an initial chaotic state, mutually blocking each other’s properties through their contrary attributes. This is the meaning of the scriptural tohu wa-bohu of Gen. 1:2. The consecutive days of creation describe the successive separation of each element from the initial mass of indeterminate qualities on days one to three (diakrisis cosmogony) followed by the formation of complex bodies on days four to six. The elements as simple bodies are the manifestation of causation at the most basic level of material structure. At this level, material causation manifests through the interaction of elemental properties: as primary qualities, such as weight, volume, subtlety, and mobility, which are real and independent of any observer other than God; as secondary-affective qualities, such as colours and sounds, which in the hexaemeral world are also inherent properties of things existing independently of any observer, but in the presence of an observer are experienced privately, viz. subjectively; and as epiphenomenal qualities, such as looking at a wall through tinted glasses, which corresponds to no change in the properties of the wall. What is fascinating about light, and responsible for much ambivalence in the ancient sources, is that light can be theorized as a primary, a secondary, and an epiphenomenal quality. Hexaemeral physics endorses a version of the ancient corpuscular theory of light (see Appendix B). This is made explicit by Gregory of Nyssa but is a substantial part of all hexaemeral exegesis of the Timaean style, from Philo and Origen to Basil and Gregory. According to the Timaean model, light particles are fire particles. All qualities of light/fire particles are ultimately reducible to two primary qualities, their (pyramidal) shape and (variable) size. They both determine a particular fire particle’s luminosity. I introduced the notion of luminosity as the essential property of fire in the second chapter of the book, while I discussed its primary, secondary, and epiphenomenal effects in Chapter 3. The basic insight of the hexaemeral physics of light is that there is no essential difference between fire particles, whether they are perceived as ‘fire’ burning at a source or as ‘light’ illuminating space (‘consubstantiality’ of fire and light). Light is just that: the presence of luminous fire particles in space. There is no other causal power of illumination than the luminosity of fire particles (‘power causality’). Illumination, despite appearances, is no real change in the properties of the medium but merely an epiphenomenal one: it is how the luminosity of fire particles makes the particle of the medium (air or water) appear bright. Fire particles at the source of ignition form a sparkle, which may become a flame if it is given enough burning material. ‘Flame’ is the first species of fire, the causal agent of illumination. Fire particles that are emitted from a flame in space form bundles of light rays. The ray or ‘radiant light’ is the second species of fire, the instrumental cause of illumination. The projectile motion of the ray through a transparent (air) or translucent (water) medium causes the luminosity of fire particles to diffuse in space. The motion of the ray in space is ‘ambient light’, the final cause of illumination. It is perceived by

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the eye as an epiphenomenal change in the colouration of space (‘affective light’). The latter is the causal explanans of vision but is itself only the end of a causal chain of production that originates with the ignition of an inflammable material. Thus, ‘flame’, ‘radiant light’, ‘ambient light’, and ‘affective light’ are just different ways of expressing fire’s luminosity through primary, secondary, and epiphenomenal properties. These properties are independent of vision and its causal explanans. That means that the primary, secondary, and epiphenomenal properties of fire are necessary explanantia of sight, while the properties of the eye have no explanatory power over fire particles, just as they have no explanatory power over air, water, or earth particles. Plato conceived of this causal order as a fundamental axiom in his construction of the phenomenal (Tim. 31b) and the noumenal (Rep. 507d–508c) world. Fire then has causal and natural priority over sight. Since fire is light, light has causal and natural priority over sight, not the other way around. This is the crucial detail that the oculocentric narrative missed, resulting in a misguided inversion of the chain of causality, subordinating the cause (fire qua light) to its effect (sight). Hexaemeral luminocentrism helps us get the facts right. Once the causal-explanatory priority of light over sight has been restored, we may finally answer the initial research question: ‘what is light?’ In the early hexaemeral literature, light is the motive force of fire (radiant light) that explains the propagation of fire particles in space (ambient light). Since our answer presupposes a theory of elemental substances, their properties, and their interactions, it requires a fully developed theory of material causation. As a result, the hexaemeral physics of light entails a complete Christian response to the charge laid by late antique Platonists against the biblical metaphysics of creation. It also leads us to the heart of Moses’ philosophy of nature. In studying the causal principles that explain the nature of light, we study the principles that govern elemental fire as the first building block of the sensible world. The logos of light, light’s explanatory principle, is our first insight into nature’s laboratory, the workshop of divine craftmanship. The contemplation of the logos of light is our first contemplation of the logos of God at work. We have just answered clearly and unambiguously the question: ‘what is light?’ Upon closer inspection, however, the answer betrays that the question itself is highly ambiguous. As we just saw, ancient corpuscular physics theorized light in at least two different respects. With regard to the emission of fire particles from their luminous source, corpuscular theories conceptualized light as ‘ray’. The corpuscular ray theory construed light as a stream of fire particles extending in a straight line (more precisely: a bundle of straight lines) from the source. Characteristically, the Stoic sources spoke of the ray as an ‘extension’ (ektasis) or ‘stretch’ (tasis) of flame into the surrounding space. With regard to the motion of the ray in space, the corpuscular theory postulated that light particles travel at extreme velocities, filling space instantaneously. The assumption that light travels at extreme speed, whether actually infinite or conceivable at the limit, conforms

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with the basic intuition of our senses that illumination is an event that takes place instantaneously. Aristotle, however, could not accept infinite magnitudes, as he explained in the third book of his Physics. He thus contested the corpuscular ray theory in his psychological writings, on the basis that light particles cannot travel instantaneously, hence at infinite speed (De an. 418b20–5; Sensu 438a26–9, 446a27–447a12). Instead, he chose to conceptualize light as an immaterial activity (energeia) of fire, arguably in the sense of a relative change in the colouration of the medium, as Alexander of Aphrodisias taught (Mantissa 143.4–18; In De sensu 134.11–19). Light as immaterial activity could now affect an instantaneous change in the visible properties of the medium without breaching Aristotle’s concerns about infinite magnitudes. Crucially, Aristotle’s discussion of light in the De anima II.7 and the De sensu 2, 3, and 6 did not object to the notion of radiant light as such but only to the notion of a corpuscular radiant light that is transmitted instantaneously. This is often forgotten in modern scholarship, which struggles to justify Aristotle’s explicit endorsement of the ray theory in several works (see Appendix A). The problem is easily solved if we realize that in his psychological writings Aristotle merely talks about ambient light, i.e. the epiphenomenal change of the medium in the presence of fire. Thus, there are at least two different notions of ‘light’ in the ancient sources, radiant light and ambient light. The two should not be confused, which means that the research question ‘what is light?’ is ambiguous because the term ‘light’ is equivocal. The equivocity of the term ‘light’ in the ancient sources is the second major discovery of this study. It also explains why the debate over the ‘metaphysics of light’, just like the oculocentric narrative, has been misled about the subject matter of their enquiry. In assuming one univocal concept of light, they failed to grasp that ‘light’ is in fact spoken of in many ways in the ancient sources. A better way to understand the intellectual history of light would have been to start with the multiple meanings of the term ‘light’ in premodern sources. In a way, the history of light is the history of the disambiguation of its multiple possible senses. The latter are actually four: radiant light and ambient light are two different ways of speaking about light particles. But light particles are, according to the corpuscular theory, fire particles emitted from a flame. Light particles are thus fire particles. This explains why the terms ‘fire’ and ‘light’ are used interchangeably in the ancient sources. Sometimes the terms denote a flame; sometimes the rays of a flame; and sometimes the motion of these rays in ambient space. ‘Fire’ and ‘light’ are terms potentially coextensive in the ancient sources. This is then the key that unlocks the ancient physics of light: light is another term for elemental fire. The ancient physics of light is a substantial part of the ancient theories of the four elements. The physics of light is the physics of elemental fire. The hexaemeral exegesis of light is built on this identification, conceptualizing the light of the first day as the manifestation in the world of the fiery element and its power of illumination.

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The answer to the research question ‘what is light?’ is, then, not at all straightforward. Our initial response should not be of the type: ‘light is X’, but of the type: ‘what do you mean when you speak of “light”? Do you mean “light” as elemental fire, as substantial flame, as radiant power, or as ambient activity?’ The answer to this question is, of course, ‘All of them!’ In other words, we should abstain from projecting onto the premodern sources the modern concept of light and its reference in the physical world. If we do so, we limit the subject matter of our enquiry and we risk missing what the sources have to say. Instead, we should approach the ancient sources with the sole purpose of decoding how they understand light in all its possible senses and variations. The hexaemeral literature with its extensive contextual and intertextual evidence helps us penetrate the ancient terminological barrier and start unravelling the meaning of light in its various senses. In the remainder of the third chapter of this book, I explored how this can be done. The careful reflection upon the use of words and the meaning of language is the doorstep to ancient metaphysics. This is also the case with the meaning of ‘light’, whose analysis reveals a full causal chain of material production, from light’s ignition to how light affects changes in the world. Light as fire denotes the first elemental substance in its generic aspect, fire as a natural kind. Light as flame denotes how fire materializes in the world, how it acquires concrete subsistence, giving rise to fire’s first species. In the celebrated terminology of fourth-century Christian metaphysics, flame corresponds to the first ‘hypostasis’ of light. This makes radiant light, the particles emitted from the flame, the second fiery species, light’s second ‘hypostasis’. The instantaneous transmission of fire’s particles in space, ambient light, is light’s third ‘hypostasis’. This is because the motion of the ray in space is perceived by the eye as light and by the skin as heat. Basil and Gregory make quite explicit that heat too is a property of the ray (Hex. VI.8 GCS 103.2–3; In hex. 33 GNO 46.15–16). In the corpuscular theory, affective light and heat are merely two different ways by which the sensory organs perceive the essential properties of fire particles, their shape and size. Heat is associated with life, while light is associated with cognition. In his celebrated sun simile at the end of book 6 of the Republic, Plato distinguished between two powers of the sun, light and vital heat. As he further explained in the Timaeus, fire particles interact with the larger air and water particles, penetrating them and breaking them up, causing air and water to become mobile (58a2–61c2). This change in the kinetic condition of the particles of the medium is perceived as light by the eye and as heat by the skin (45b2–46c6; 61d5–62a5; 64a2–c4). Affective light and heat are thus epiphenomenal properties of the medium, caused by a real change in its kinetic state due to the motion of light particles in it. While the emission of fire particles from flame was theorized as radiant light, light’s second ‘hypostasis’, the change the fire particles bring in the kinetic condition of the medium was theorized as light’s third (and final) ‘hypostasis’.

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‘Light’ then reveals itself to be a pollachōs legomenon, a term of many senses. The different meanings of ‘light’ are no chance equivocity, since they are all related to each other through a clear explanatory-causal chain. Each sense of ‘light’ denotes a different part of the first causal chain of material production. In its generic sense, light denotes the fiery nature. In its specific senses, light denotes fire’s substantial existence as flame, its radiant power of light and heat hypostasized in the ray, and the ambient light and heat that activate our senses through the motion of the ray in space. Light then reveals a triadic structure of nature. Fire, as the first instance of qualified matter, manifests itself as substance (flame), power (ray), and activity (motion), a triadic causal scheme that is widespread in late antique Christian and Platonist sources. The causal scheme means that the explanatory principle of light, its logos, manifests itself in a trinitarian fashion. We do not know why this is so, why the logos of light manifests through a triadic chain of causation as substance, power, and activity. We do not have an explanation for the explanatory principle of light itself other than how we see light operate in nature. From what we see, and through careful reflection, we perceive that the logos of light is the first and simplest manifestation of the divine logos at work. From the fact that the logos of light expresses itself in a trinitarian fashion, and the fact that fire is the simplest form of bodily structure in the material universe, while Scripture uses the language of ‘light’ also to denote elemental fire, we infer the triadic causal structure of the material world. The causal nature of light reveals the causal nature of the sensible world. Light contains the code of material creation. Every material structure is ultimately analysable into substances, their natural powers, and their physical activities. The hexaemeral metaphysics of light reveals the trinitarian pattern of the intelligible structure of the world. Every sensible being, starting with light, manifests itself as a triadic causal unity. It is here that the craft analogy acquires its full force. If light is part of the world, and the world is (like) a work of art; further, if the work of art reveals the creative genius of its craftsman, then the metaphysics of light tells us something about the nature of the world and the divine mind that conceived it. First, the metaphysics of light teaches us that the triadic structure is the ultimate causal explanans of the order and beauty that we see in the world. The four elements exhibit the same causal structure as the logos of fire, which produces each element through a different configuration of the same primary constituent components (properties). In turn, complex bodily structures, such as minerals, plants, and animals, have as their constituent components the simple bodies of the four elements in different admixtures. They thus exhibit the same triadic structure as the logos of their constituent elements, expressed at a higher order of complexity. This brings us to the human being, the apex of earthly bodily structures according to the biblical creation narrative. In contemplating the logos of light, the human mind grasps the metaphysical pattern of the world that it inhabits. The human being as part of this

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world is crafted according to the same pattern. In contemplating the logos of light, the human mind grasps the triadic metaphysical pattern of sensible being, therefore the triadic causal nature of the human logos itself. By inviting the readers to immerse themselves in the text, the biblical creation narrative actually invites the readers to immerse themselves in themselves. In the eyes of the contemplative reader, the hexaemeron is transformed from a cosmological narrative into a literary mirror of the world in which the human mind can contemplate its own reflection. We begin reading Scripture with the creation of light on day one. But we start our life’s journey as creatures of day six. By reading Scripture, we contemplate the reality we inhabit in six narrative steps that lead from the light of the world to the emergence of the human species. In retracing those steps, we contemplate, on the literary canvas that Moses set before us, the stages of formation of the human self. Every divine fiat, every literary act of divine creative repetition, invites us to a reflective journey at the end of which we will meet with our own nature. In the eyes of the contemplative reader, Moses’ account of creation is transformed into an account of creation of the human self. The world is the reader. Cosmogenesis is self-making. As Basil put it, in the work that holds the key to fourth-century hexaemeral hermeneutics, ‘if you are attentive to yourself . . . you will see in yourself, as if in a kind of small ordered world, the great wisdom of the Creator’ (Hom. 319.7). As the work of the sixth day encounters the work of day one, the human mind encounters its own image in the reflective mirror of the soul. You, the reader, are the world. Mind is light. Mind exhibits the radiant power of its thoughts through the demiurgic activity of its creative genius. Substance–power–activity is the code that explains the nature of light as well as the nature of mind. The light–mind analogy, which is the essence of the onto-theological light language of the Platonic and the Aristotelian traditions (the much debated ‘metaphysics of light’), finds in the hexaemeral contemplation of nature (the metaphysics of light properly speaking) its full rational justification. In the immortal words of Severian of Gabala, expressing the heart of all early hexaemeral exegesis in the Alexandrian style: Since light was God’s first work and the human being God’s final work, God first makes the light with a word and later the human being with an action, completing light with light. To learn how a human being is also light, listen carefully. Light shows what is in existence; the human being is the light of the world, and at his entrance he showed you a light of artifice, a light of knowledge. The light showed grain, intelligence made bread; the light showed grapes of the vine, the light of understanding showed the wine in the grapes; the light showed wool, the human’s being light showed clothing; the light showed a mountain, the light of understanding showed stonecutting. This is the reason why the Savior also calls the apostles light in saying, ‘You are the light of the world’ [Matt. 5:14]. (Cosmog. I.6 PG 56:436 tr. Hill)

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If mind is (like) light, the research question ‘what is light?’ has tremendous ramifications for the realm of anthropology and general metaphysics. Plato’s sun simile in the Republic matched the visual capacity of the eye to catch the light with our cognitive capacity to know the truth. He also told us that the light is the illuminative power of the sun. In the Timaeus, however, he further explained that the eye is able to catch the light because of the light that it itself emits (like-tolike principle; sunaugeia model). He thus told us that just as the light of the sun is the product of celestial fire, so too is there an internal fire in the eye that produces the light of the visual current. Reading the sun simile of the Republic and the account of vision of the Timaeus together, we come to realize the intellective nature of being itself. If the sun is analogous to the Good and the light of the sun analogous to intellection, then our mind is analogous to the Good, which must be, by force of the analogy, a supra-intellective nature. This explains Aristotle’s mind– light analogy in the De anima III.5, but also the (otherwise curious) Middle Platonic emendation of Rep. 509b which stipulates that the Good is not merely beyond essence (epekeina tēs ousias) but beyond intellect and essence (epekeina nou kai ousias). Read in this context, the difference between the ‘metaphysics of light’ in an extended sense and the metaphysics of light in a proper sense collapses. If in the introduction and throughout this book it was deemed pedagogically necessary to distinguish between the theological use of light language and the concept of light as such in order to understand the meaning of the premodern onto-theological light language, we can let go of the distinction once we realize the light–mind analogy that is operative in the sources. If mind operates triadically like light, the nature of light reveals the nature of mind. Much more than that, light and mind together reveal a perfect relation of correspondence between the intelligible and sensible aspect of being. In contemplating the light of the world, we contemplate the double nature of reality, sensible and intelligible. This is the beating heart of Moses’ philosophy of nature, hidden behind a double hermeneutical strategy: light’s metaphysical structure is described on day one, while light’s physical operation is described on day four. This double vision of light, as lux intelligibilis (day one) and lux sensibilis (day four), is a substantial part of the Alexandrian hexaemeral project and its Cappadocian legacy. It is therefore necessary to retrieve Basil and Gregory from an ancient but rather misleading interpretative tradition which puts them in opposition to Augustine’s spiritual exegesis of primordial light. The study of light requires a careful distinction between light’s noumenal causal structure (a logos account) and its phenomenal properties (susceptible to sense perception). The distinction between the noumenal and the phenomenal aspect of being is the cornerstone of ancient epistemology. Origen has already implied that the epistemological distinction was scripturally attested through the paradoxical opposition of light and luminaries in the creation narrative (DP IV.3.1; Hom. Ps. 73, III.2–3). In dispelling the paradox (light without luminaries?) through the

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synchronical exegesis of days one and four of the creation narrative (no light without luminaries, yet causal priority of light’s luminosity over its sensible properties), the Cappadocian brothers carried forward the Origenian suggestion, adding an epistemological layer to the cosmological narrative. There are no two stages in the creation of light, only two modes of cognition: light in its intelligible (day one) and light in its sensible aspect (day four). The metaphysics of light is inextricably intertwined with the epistemology of light. The distinction between metaphysics and physics corresponds to the distinction between knowing and perceiving. It is through light’s sensible properties that we are able to see the world. And it is by grasping the logos of light that we grasp the causal structure of the world. Perceiving the light is perceiving the world—knowing the light is knowing the world. The epistemological distinction between the intelligible and the sensible aspect of creation is thus a substantial part of the Cappadocian hexaemeral project in general and of the exegesis of light in particular. If the later tradition typified the two aspects of light, intelligible/noumenal and sensible/ phenomenal, as respectively Latin-Augustinian and Greek-Basilian, as we find for example in the third book of Eriugena’s Periphyseon, this had more to do with cultural rather than exegetical or metaphysical considerations. For this reason, I have argued throughout this book for a double vision of creation, physical and metaphysical, culminating in the internal dialectics of day one and day four of the creation narrative in the Alexandrian hermeneutical tradition. This double vision of creation, indispensable for our cognition of the world we inhabit, fatally vanishes if, by reversing the order of causality, we subsume the intelligible cause to its sensible effect and instead of using light as the ultimate explanans of vision (luminocentrism) we use vision as the ultimate explanans of light (oculocentrism). It is for this reason that in this book I took so much pain in refuting the oculocentric approach to the ancient theories. As the hexaemeral contemplation of light ends, new insights begin. The light– mind analogy, together with the craft analogy, leads us beyond the realm of the work of art to the internal world of the artist. In contemplating the world, we may know only one aspect of the divine mind that conceived it, namely the demiurgic aspect of its logos. Yet, if we are minds in the image and likeness of the divine artist, as Gen. 1:26 suggests; and our minds are like light, as Severian suggests, following a genuinely Origenian exegetical trope; then the nature of light discloses something about the nature of the divine artist. In contemplating the light, we learn not only about the nature of our mind but also about the nature of mind itself. It is the nature of mind, whether human or divine, to think and act triadically. The trinitarian metaphysics of light reveals the triadic nature of pure intellective activity, hence the triadic nature of intellective reality. If God is light (1 John 1:5), Johannine literature expands on the same trinitarian metaphysics that is the ontological foundation of Moses’ philosophy of nature. If, in addition, the logos is God (John 1:1), Johannine literature carries further Moses’ trinitarian

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vision of being as intellective reality. The identification of pure being with intellection, first made explicit in the history of Western thought through Parmenides, runs like a thread from the first chapter of the book of Genesis to the ingenious Johannine combination of the logos doctrine with the Wisdom literature. In its scriptural guise, and through an Origenian legacy that uncovers it, the identification of being with thought reaches the fourth-century trinitarian debates, acquiring its permanent Christian articulation through the celebrated Nicene formula ‘light from light’. We rarely approach the Creed from a hexaemeral perspective today. Light, however, is a scriptural term whose meaning is firmly grounded in the hexaemeral narrative. The same theologians who debated over the nature of Christ’s divinity also produced some of the deepest reflections on the creation of the world. From a hexaemeral perspective, light, like mind, is trinitarian in nature. The conceptual ingredients of the Nicene formula are exactly the same as those of Plato’s sun simile, capturing in the scriptural equivocal language of ‘light’ and ‘light’ the causal relation of fire to its radiance as perennial metaphysical analogy of the nature and operation of being (see Appendix C). Behind the Nicene formula hides, in coded form, the trinitarian metaphysics of the mind qua light of the early Church. The hexaemeral metaphysics of light thus holds the key to early Christian trinitarian doctrine. But the key serves only to unlock a door which leads through anthropology to trinitarian theology. The hexaemeral literature can never be isolated from the broader theological project to which it belongs, and which includes the anthropological dimension of the hexameral writings (call it the De opificio hominis literature) and the exegetical foundations of early Christian trinitarian doctrine (call it the De Trinitate or De fide literature). A final remark: the hexaemeral light–mind analogy assumes that the simplest and the most complex bodily creatures, fire and the human being, exhibit the same internal causal structure, that the human logos and the logos of light manifest through the same trinitarian causal scheme. Clearly, this would be a mistaken assumption if it were to be understood in the sense that complex bodies exhibit the same or analogous properties to the properties of the simple bodies that constitute them. A cookie tastes very different from its ingredients unbaked and unmixed. Similarly, the human body has different properties than the four elements that constitute it, while different quantities and mixtures of the four elements result in very different organic bodies, such as plants, animals, and humans. Why would hexaemeral authors assume that the explanatory principles of natural kinds, namely all the logoi of creation, exhibit the same internal structure? The answer is easy: it assumes the possibility of a parsimonious account of the world. This possibility may be contested. But it is a viable possibility in the context of hexaemeral thought. Already Plato in the Timaeus reduced all material causation to the inherent and emergent properties of a geometrical structure, the right-angled triangle (53b5–54b5). On the Timaean account, different kinds of right-angled triangles in

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different sizes and combinations result in the infinite variety of simple and complex bodies in nature (57c8–d6). Triangularity is thus the Timaean equivalent to the internal structure of a hexaemeral logos. In postulating the same causal structure of all logoi of nature, the hexaemeral authors applied the same principle of parsimony as Plato, assuming that all bodily structures are deducible from a single explanatory scheme, regardless of their degree of complexity. While for the students of Plato the explanatory scheme was a mathematical model (the right-angled triangle), for the students of Moses it was an ontological model (substance–power–activity). According to both schools of thought, the explanatory scheme was triadic in nature. The triad, then, is the explanatory principle of all logoi of creation. An explanatory principle, however, presupposes the subject matter of its explanation. In searching for the logoi of things we must never forget that we are the ultimate subject matter of our investigation. But we are bodily creatures. Our understanding of the world has to start from the body, just as our perception of the self starts with the body. Later on, once we have learned to distinguish between intelligible and sensible objects, we might end up revising the starting point of our investigation. But we can never abandon it, if indeed to be human is to be minds embodied. Capitalizing on the light–mind analogy to the fullest, the metaphysics of light is inherently embodied metaphysics. This is the contribution of the hexaemeral literature to the ongoing ancient and modern debate. The hexaemeral literature construes the logos of light as the first manifestation of a triadic causal scheme that ultimately explains all sensible phenomena of this world. Yet this is a material world, a world made up not only of intelligible causes but also of sensible effects. Material reality requires always embodied logoi, causal accounts that explain why concrete bodies act and react in this way or another. The world as we know it is a hylomorphic reality. The logoi of nature are always embodied logoi. The logos of light may be triadic and because of that it may lead the students of nature to the contemplation of a trinitarian divine mind as the author of this world. It may also exhibit the exemplary causal structure of this world, since hexaemeral light is the simplest and most form-like (‘immaterial’) bodily structure of the material universe. As such, it may lead the students of nature to the contemplation of their own self, the logos that explains human experience. Yet human experience, the awareness of the self, is mediated through the body. Human mind is embodied mind. In contemplating the logos of light, the hexaemeral readers contemplate themselves as an embodied logos, the logos that contains in itself the universal code of bodily existence. It is the trinitarian code of the primordial logos of light. In contemplating in themselves the primordial logos, the hexaemeral readers contemplate the universal logos of nature, the logos of the divine Demiurge in its endless manifestations though its works. To the Christian readers, this is a vision of Christ as the heart of creation, the vision upon which hinge the law and the prophets. The aim of the metaphysics of light in the early hexaemeral literature is the attainment of a vision of Christ, the embodied logos, as the metaphysical foundation of Moses’ philosophy of nature.

APPENDIX A

Response to a Critic, or What Is the History of Optics Really About? For it is from the sun that both the daylight and the generative heat in animals and plants derive; furthermore, the archē of our terrestrial and burning fire can be produced through this. Many people, at any rate, while igniting fire actually suppose that its light comes from the sun. (Theophrastus, De igne §5 tr. Raalte) A central theme of this book has been the investigation of the early Christian physics of light, the existence of which is currently disputed by a major school of thought in the history of science. In the first chapter, I explained the reasons for this dispute and why my argument had to explore a new path. Meanwhile, a paper of mine was published, which contained an early version of the argument presented in this book (see Katsos 2019). In that paper I argued for the first time for the existence of a genuine physics of light in the ancient sources. Focusing on the Platonic Timaeus, I showed that such an enquiry is possible and needs to be added to current textbook approaches to the history of optics, which remain eminently oculocentric. Instead of rejecting oculocentrism tout court, I suggested, developing an argument first presented by Lindberg (1976), x, that luminocentrism and oculocentrism are two complementary approaches to ancient theories of light, vision, and colour. I also assumed that there was conceptual space in A. Mark Smith’s oculocentric narrative for a luminocentric chapter, as implied by Smith’s own qualification that premodern optics was aimed ‘primarily’ not at light but at sight (see Smith 2015, ix). At the same time, a rejoinder to my paper was published by Smith (2019). In his riposte, Smith defended the thesis of his book From Sight to Light (2015) that there is no physics of light before the emergence of the modern scientific paradigm. He also made three important clarifications, which took his thesis a bit further. First, he argued that the key passage that unlocks the Timaean theory of light is Plato’s discussion of reflection in 46a–c (p. 287). That makes the Timaean theory ‘fundamentally oculocentric in that it focuses on what is seen on the mirror’s surface, not on how light interacts physically with it’ (p. 288). Secondly, Smith clarified that he fully adheres to Simon’s view, according to which ‘in no way central among the preoccupations of the ancients is the propagation of a ray but, rather, the locating of an image’ (p. 289, italics in the original). Finally, Smith contended that there is some conceptual space for an ancient physics of light in the sources. This is limited, however, to ‘the study of burning mirrors (and, later, burning lenses)’, which goes back at least to the early Hellenistic period. ‘Light, as an agent of heat, is the sole focus of this study, so it is absolutely viewer independent and therefore seems to fit perfectly within the category of physical optics as we understand it today. But this is an exception that proves the rule’ (p. 289). Smith’s paper offers a generous, if heated, refutation of my argument with the exception of the case of burning mirrors (not discussed in my original paper). It also narrows down considerably the scope of the debate by making even more apparent the set of questions that are implicit in the discussion and which are, I believe, of interest to a general audience: if the subject matter of modern optics is the physics of light (i.e. the study of the nature and

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properties of light), is the history of optics co-extensive with the history of the physics of light or not? If it is, is the ancient physics of light limited to the literary genre called ‘optics’ or can we also trace it back to other sources? If we can, ought we not also to include these other sources to the history of optics? These questions can be summarized under the general heading: ‘what is the history of optics really about?’ The issue at stake is methodological and hermeneutical at the same time. It concerns the sources that are relevant for the study of light in the history of science, their classification, and their interpretation. It is for this reason that I decided to address the issue in a separate appendix. Let me start by taking Smith’s last point first. It is really helpful that we now have an explanation of what the qualifier ‘primarily’ means in the oculocentric reading of the sources. According to Smith’s own clarification, it means that ancient theories of light were interested in the study of sight not light, with the exception of light as an agent of heat in the case of burning mirrors (and, later, burning lenses). The reader who has been patient enough to follow my argument up to now will perceive that, in my reading of the sources, early Christian thinkers treat of light as an agent of illumination in exactly the same viewerindependent way that Smith accepts for light as an agent of heat. My argument for the early Christian physics of light is therefore based on exactly the same premises as Smith’s exception for burning mirrors and, later, burning lenses. It is therefore clear that we both agree that the epistemic foundations of a genuine physics of light can be traced back to the ancient sources even if we diverge regarding the scope of application: Smith limits the ancient physics of light to the agency of heat; I extend it to light’s proper and natural agency of illumination. The point of contention, then, is whether the premises accepted by Smith exceptionally for light as an agent of heat apply more generally also to light as an agent of illumination (in which case the ‘exception’ would turn out to be no exception at all, with further consequences for the oculocentric narrative, see Zemplen 2020). This raises a hermeneutical question which I find fascinating: how is it that Smith and I read the same sources, but deviate so much in their interpretation that we arrive at the exact opposite conclusions? I find the question fascinating, not the least because it contains a lesson in epistemic humility: what seems the natural way of reading a text to me is not necessarily the same for someone else. The latter remark paves the way to answering the question. I understand the debate about the ‘luminocentric vs. oculocentric’ reading of the ancient sources to be an illustration of a well-known problem in hermeneutics: our sense-making of a text as a whole relies on our sense-making of its parts and how we relate each part to the others. In turn, our sense-making of the parts depends on the assumptions (‘prejudices’) that we necessarily bring with us and our fore-expectations of the meaning of a given text as a whole. By constantly questioning our assumptions we suspend illegitimate expectations, letting the internal unity of a text guide us into how to recollect its parts into a meaningful whole (the so-called ‘hermeneutic circle’, see Gadamer 2004, 268–382). When Smith and I read an ancient text, we clearly approach it with different hermeneutical assumptions, leading us to relate its parts differently, unavoidably resulting in a different understanding of the text as a whole. The text in question is the Platonic Timaeus. It is therefore interesting to show, albeit briefly, in what way Smith’s ‘oculocentric’ reading of the Timaeus differs from my ‘luminocentric’ one. Let me begin by rehearsing the cluster of the main passages relevant to light in the Timaeus: 1) 45b–46a on the eye and the mechanism of vision; 2) 46a–c on catoptrics, discussing mirror images and reflection; 3) 55d–58d on the formation of the four elements, their properties and particles; and 4) 67c–68d on sensible qualities and colours as the proper sensibles of vision. Smith’s oculocentric reading aims to show that ‘Plato’s account was not on the physics of light but, rather, on the functioning of sight’ (p. 283). To derive

        ? 177 this from the text, Smith follows a complex hermeneutical strategy: first, he adopts a subjectivist reading of the theory of colours (67c–68d): ‘at bottom colour, as defined by redness, yellowness, greenness, or blueness, exists subjectively in the psyche, not objectively in external reality’ (p. 286). Secondly, he finds the passages on the physics of light (55d–58d and 67c–68d) as largely uninformative: ‘About how daylight diffuses through the air Plato has nothing to say, so we know nothing about the physics of its propagation other than that its tiny constituent particles are tetrahedral’ (p. 287). ‘About colour radiation . . . we know more . . . As with daylight, however, so with this light, we know nothing about how or whether it interacts physically with anything other than the particles of ocular light’ (p. 287). Thirdly, he opposes ocular light to external light and colours based on Plato’s discussion of the formation of mirror images: ‘But which of the two kinds [sc. of light, the one emitted by objects or the other by the eye] forms the basis of the supposed luminocentricity of the Timaean account? To answer this, we should look back at Plato’s discussion of reflection in Timaeus 46a–c’ (p. 287). ‘What is addressed [sc. in Tim. 46a–c] is how images are formed on the surfaces of mirrors and, more to the point, why they may appear reversed or inverted’ (p. 288). Based on the above hermeneutical choices Smith derives the following conclusions: 1) ‘Plato’s analysis of reflection is fundamentally oculocentric in that it focuses on what is seen on the mirror’s surface, not on how light interacts physically with it’ (p. 288); 2) ‘the light at the centre of this analysis is not the external daylight or the light consisting of colour particles streaming from the face but the light from the eyes’ (p. 288); 3) there are two kinds of light, fundamentally different: the light that radiates from luminous or illuminated objects such as the sun and the light from the eye. ‘The two kinds of light thus differ fundamentally in their physical effects, the one being to illuminate and sometimes to heat, the other being to establish visual contact’ (p. 289). According to this reading, the inner logic of the Timaeus follows the explanatory scheme: catoptrics (46a–c) → theory of vision (45b–46a) → theory of colours (67c–68d). With this explanatory scheme is juxtaposed the external light (55d–58d) as the subject matter of physical optics. In other words, if we follow Smith, the Timaeus adopts the explanatory order: formation of images → visual reception → subjective sensible properties ≠ [i.e. fundamentally different from] objective properties. And since we perceive the world through sensible properties, we perceive the world subjectively. As a result, the disjunction of ocular light and our subjective experience of colours from external light and its objective physical properties leads to the disjunction of phenomenal from real properties, hence of the world as we perceive it from the world as it is. Alternatively, it leads to a denial of objective properties, hence to the conclusion that the world is just what we perceive. These are the epistemological and metaphysical consequences of Smith’s reading of the Timaean theory of light, if indeed ‘in no way central among the preoccupations of the ancients is the propagation of a ray but, rather, the locating of an image’. I find this a strange reading of the Timaeus, for two reasons: first, it disjoints what the text explicitly conjoins, namely external and internal light. In 45b–46a, sun light and ocular light are called ‘akin’ (adelphon, suggenous), and it is in virtue of this kinship (homoion pros homoion) that they are able to coalesce (sumpages) and produce the visual body. If we postulate, with Smith, that sun light and ocular light are ‘fundamentally different’, then there is no room for an application of the like-to-like principle and the whole Timaean theory of vision collapses. Secondly, the subjectivist reading of the Timaean theory of colours eradicates entirely the existence of colours (and with them, the special object of vision) from the external world. This sounds to me like bringing Plato dangerously close to either Democritean atomism (if we accept an external reality) or Protagorean relativism (if all reality exists in the way we perceive it). I say ‘dangerously’, because, according to the

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interpretation I follow, Plato was opposed to both (see Ierodiakonou 2005b, 229–32). For these reasons, I opt for a different reading of the Timaeus, one that respects the integrity of the text; searches, charitably, for the inner unity and strongest version of Plato’s argument; and does not make the Timaeus contradict basic Platonic tenets (without precluding, however, the possibility of a developmental reading of the Platonic corpus). The basic tenet of the Timaean theory of light is, on my reading, the causal/explanatory priority of light over sight (31b5). What this means is that one cannot adequately explain the process of visual perception without having explained first something about the nature and propagation of light, while one can explain the nature and propagation of light without the need to explain anything about the process of visual perception (see Chapter 2, section 2.3.2). The purpose of my paper (2019) was precisely to show that the causal priority of light over sight allows us to reconstruct the inner logic of the Timaeus in the following explanatory order: physics of light (55d–58d) → colours (67c–68d) → visibility of bodies (31b), which in the presence of a perceiving subject activates the mechanism of vision (45b–46c) resulting in sense perception (64d–e). This is tantamount to the explanatory order: [objective] elemental properties → sensible properties → sensible objects + vision → [subjective] formation of images. On this reading, light and colours are streams of fire particles with similar elemental structure (since all fire particles have the same shape: Tim. 58c), without precluding the variety of light and colours (since different fire particles have the same shape but different size: Tim. 67c–68d). As kinds of fire, light and colours interact with the other elements in the way fire does (Tim. 56d–57c). In addition, every stream of fire particles exhibits objective properties (namely the shape and size of its particles), albeit the fact that the way we perceive these properties is contingent on our visual apparatus. Light and colours then exist independently of the existence of any sentient being, even though, from a local teleological perspective, the visual apparatus of a sentient being codetermines how light and colours are perceived by it. Existence is not the same as perception, however, and this is where my reading of the Timaeus fundamentally differs from the oculocentric reading. Thus, behind the two readings lie diametrically opposed epistemological and metaphysical assumptions about Plato’s understanding of the worldas-it-is and the world-as-it-appears. If only it were just Plato. Smith is tempted to extend his hermeneutical strategy to the rest of the ancient sources. To this purpose, he limits the importance of the Timaeus ‘to a single case study’ (p. 284); he emphasizes, in passing, how ‘patently absurd’ a luminocentric reading of Aristotle’s De anima II.7 would be (p. 286 n. 13) and complains, based on the authority of Simon, that a luminocentric reading of Ptolemy’s Optics would result in ‘an anachronistic and therefore misleading interpretation of ancient ray theory’ (p. 288). This is a further exciting application of the different possible constructions of hermeneutical part– whole relations mentioned above (‘hermeneutical circle’), which now apply not only to a single text but also to a whole range of ancient sources: it is not just the Platonic paradigm which is oculocentric; it is also the Aristotelian and the Ptolemaic, namely three of the most important late antique optical traditions. The Timaeus, the De anima, and the Optics become parts of a grand premodern narrative of the passage ‘from sight to light’. Here, too, I am forced to make different hermeneutical choices. First, I am a bit reluctant to subscribe to a single uniform narrative applicable to all ancient sources on light. Second, and precisely for that reason, my paper (2019) focused only on one tradition, the Timaean, in exploring ancient luminocentrism. As I have argued in this book, the early hexaemeral literature was also part of that tradition. Stoic adaptations, Aristotelian modifications, and scriptural strictures did not change the fact that the hexaemeral authors shared the same Timaean intuitions about light and colours, reinterpreting them to fit a late antique biblical

        ? 179 worldview. In arguing so, I merely followed a mainstream interpretation of the early hexaemeral sources, exemplified in the writings of Runia, Köckert, and others, which I advanced to include the case of light. The lasting influence of the Timaeus upon several communities of readers, including the early hexaemeral literature, renders ancient luminocentrism relevant to a much wider array of sources than ‘a single case study’. Third, regarding the Aristotelian tradition, I can only offer a brief remark in passing: I am very happy that Smith now also perceives that the theory of light in the De anima II.7 is visionindependent (p. 286 n.13). From this it does not follow, however, that ‘Aristotle must have been engaged in what amounts to modern physical optics’ (p. 286 n.13), because the subject matter of Aristotle’s investigation in the De anima II.7 is visual perception and not the physics of light nor reflection or refraction. Aristotle discusses in this context the nature of ambient light, and this only incidentally, as far as it is needed for his analysis of visual perception. If one wants to learn more about Aristotle’s thoughts on the nature and physical properties of light, his discussion of the composition of the stars and how they emit light and heat is a very good place to start (see Thorp 1982). The question is not whether Aristotle is a precursor of modern physical optics, which would be quite an anachronistic question to ask, but whether he is able to theorize light as an agent of illumination in nature (and not merely as an agent of vision). That is precisely what he does in the astronomical context of the De caelo II.7. Given this textual evidence, the talk of an Aristotelian physics of light is not so ‘patently absurd’ as Smith thinks (p. 286 n.13). Having said that, a comprehensive treatment of the Aristotelian physics of light would have to take into consideration many different aspects of Aristotle’s discussion of light. In addition to the production of ambient light in De anima II.7 and the dynamic principles of light’s emission in De caelo II.7, such different aspects include: • reflection in the De an. II.8 (419b28–33) and the Meteor. III.2–4 (see Lindberg 1976, 217–18 n.39; Johansen 1997, 48–9 and 58–9); • the explanation of lightning in the Meteor. II.9; • the relation of mathematical to physical optics in the Phys. II.2; • light and colour as objective sensible qualities in the Sens. 3 (see Ierodiakonou 2018); • light as cause and principle in the Metaph. XII.4; • the role of the corpuscular ray theory in the Aristotelian corpus (see Top. V.5; Problem. XI.33; De coloribus 1). Aristotle’s physics of light is therefore situated at a hermeneutical nexus, which still awaits its proper treatment. This is no reason, however, to dismiss the astronomical discussion of the physics of light as irrelevant. On the contrary, even in his psychological writings, Aristotle affirms the same explanatory priority of fire over light and of light over sight as Plato, irrespective of the presence of any sentient being, as Smith also concedes (see De an. II.7: 418a31–b4, 418b11–13, 419a22–5; Sens. 3: 439a19–21; Ross 1906, 20–1). Interestingly, it is the same explanatory priority of light over sight that is the fundamental tenet of Smith’s own account of the modern optical paradigm. Fourth, a similar remark can be made, again only in passing, as regards the nature of Ptolemy’s Optics. The issue here is that the first book of the Optics, which evidently contained the key to the relation of light and sight (see Optics II.1 [= Preface.2]), is now lost. To the extent that the key is lost together with the book, all judgement about how Ptolemy framed his project remains speculative. Smith, as an expert, professes its oculocentrism (p. 288). But one could also side with other experts who prefer to profess agnosticism, especially since several ancient

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testimonies to Ptolemy’s Optics relate to questions about the physics of light—the very subject matter of the now lost book (see Lejeune 1989, 13–14, 18–19, 271; Netz and Squire 2016, 73–4 and n.19). Thus, even if Smith is right and the Optics was originally written with the sole aim of explaining visual phenomena, several ancient testimonia approach it with an interest in the physicality of light. If not Ptolemy, at least some of his readers were genuinely interested in the physics of light. It should be quite clear by now that behind the two different readings of the sources stand different hermeneutical assumptions about the relation of the world-as-it-is and the world-as-it-appears. The oculocentric reading prioritizes phenomenal properties, the image, the world as it is perceived through the senses. Light in this view is instrumental to visual perception. By contrast, the luminocentric reading prioritizes the world as it is, as a given or, from a theological perspective, as a gift. The focus here is on light’s objective properties, the physicality of light as explanans of what the senses receive, light as it exists in the world and interacts with other physical bodies. Both readings are possible, but for the reasons I have stated above both readings are not equally valid. In my view, the hermeneutical lens of the oculocentric approach is too narrow, because it clings to a certain canon of texts and a certain reading of passages with quasi-reverential piety. Every piece of contrary evidence has to be accommodated to this canon and its prescribed reading practices. In this book, however, I have discussed a number of late antique sources that do not belong to the canon of the textbook approach to the history of optics. Surely, the focus of the hexaemeral literature was not physical optics. Even if they are non-optical treatises, however, several hexaemeral texts discuss extensively and profoundly light as a physical agent in the world, its nature and its interaction with the physical elements, independently of vision. They do so out of a genuine interest to understand why and how light is the first manifestation of orderly structure in the sensible world, why luminosity is the first sensible property, and how all sensible reality, the world as a phainomenon, emerges with it. This enquiry can only be achieved through a genuine discussion of the physics of light. If such physics of light really existed, as I have argued in this book, then it is the task of historians to include it in their narrative, even if the physics of light is not to be found under the heading of a treatise entitled ‘optics’. This is because, in my opinion, the historian of science should be interested in the history of the subject matter (here: the enquiry into the nature and properties of light) and not merely in the history of a literary genre (here: ‘optics’), no matter how valuable the latter enquiry might be in itself. My argument is not against the history of the genre, which might be excellently portrayed from an oculocentric perspective (see now Smith 2018). My argument is against obscuring the history of the subject matter for the sake of the history of the genre. Strictly speaking, my argument is meta-optical. Plato or Aristotle left behind no treatise on ‘optics’, yet this does not stop us from enquiring how they theorized light in their physical, psychological, and metaphysical writings. Why should it be any different with the rest of our sources? The luminocentric approach aims to broaden the hermeneutical lens through which we approach premodern sources. Its aim is to make the historically sensitive reader aware that the ‘history of light’ ought to be about the history of the enquiry into the nature of light regardless of the label of the sources that contain such an enquiry (‘optics’, ‘physics’, ‘cosmology’, ‘psychology’, etc.). The hexaemeral literature is a case in point.

APPENDIX B

What Is the Colour of Light? Light he describes as exceedingly beautiful, for the intelligible [light] surpasses the visible in brilliance (lamproteron) and brightness (augoeidesteron) just as much, I believe, as sun surpasses darkness . . . (Philo, Opif. 30 tr. Runia) In a notoriously difficult section of his sixth hexaemeral homily, Basil theorizes sensible light as the hylomorphic composite of matter and quality (Hex. VI.2–3 GCS 91.1–93.6). In this book, I have more than once commented on the exegetical value of this passage, which is the key to Basil’s dual hermeneutics of light, distinguishing between light’s ideal aspect as the work of day one and its sensible aspect as the work of day four (see Chapter 3, sections 3.1.3, 3.3.2, 3.4.1). The hermeneutical distinction has significant metaphysical bearing. The exegesis of the light of day one as an intelligible creation, i.e. fire in its generic, pure elemental, or eidetic aspect, preserves the Origenian programme, though not the exegetical method, shifting the hexaemeral narrative from the purely physical to the metaphysical aspect of creation. The eidetic aspect of fire becomes the first instantiation of causality, hence of order in the world. The triptych substance–power–activity reveals the internal structure of fire as the causal explanans of light’s mechanical properties (see Chapter 3, section 3.3.3). Thus, the dual aspect interpretation entails the explanatory and causal priority of the metaphysics of light (day one) over the physics of light (day four). As regards physical light, Basil theorizes it as a power (dunamis) and activity (energoun) of fire (VI.3 GCS 92.1–5). A visible fire is, in turn, a hylomorphic compound (suntheton), further analysable into a receptive ousia and its accompanying quality (episumbasa poiotēta, VI.3 GCS 91.14–15). The term ousia here means ‘underlying body’ (hupokeimenon sōma), following Aristotle’s terminology in the Physics and the Metaphysics (see Edwards (2019), 117), while the accompanying quality is lamprotēs, which can be translated either as ‘luminosity’ or as ‘brilliance’, but which I prefer to leave untranslated for a while. In virtue of this quality, a fiery substance is a naturally luminous body. This is an application of the general principle announced earlier in the homilies that everything created is a composite of form and matter (II.3 GCS 25.9–12; cf. Aristotle, Phys. I.7 and II.2; De an. II.1). Together with the insight announced at the outset that the world is comparable to the production of a work of art (I.7 GCS 12.1–20; cf. Aristotle, Metaph. VI.1 1025b18–28 and VII.7), Basil’s hylomorphic metaphysics of creation entails the basic tenets of Aristotelian natural philosophy, modified to fit scriptural tenets, most notably the creatio ex nihilo (II.2–3 GCS 23.6–25.18; see also Chapter 1, section 1.3.3 and Chapter 2, section 2.2.3). In the subtext of Basil’s homilies, then, we find operative the basic Aristotelian schemes of potentiality– actuality and of matter–privation–form. If we now identify, with Aristotle, matter with potentiality and form with actuality (Phys. II.1 193b6–8; De an. II.1 412a9–10; Metaph. IX.6 1048a25–b9), we gain the full picture of Basil’s dual hermeneutics of light: the narrative sequence (akolouthia) from day one to day four reflects the temporal chain of material production from potentiality to actuality. At the same time, the creation of light in its formal–eidetic aspect on day one preceding the creation of light in its sensible–material aspect on day four upholds Aristotle’s basic metaphysical axiom that actuality precedes

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potentiality (Metaph. IX.8 1049b5). To show that the explanatory principles of Aristotelian natural philosophy are already inscribed in the biblical creation narrative, and to provide a robust account of material causality, Basil emphasizes the necessity of a material substratum for sensible light to occur: it is precisely this substratum (to hupokeimenon Hex. II.2 GCS 24.4, II.3 GCS 25.13) which requires the synergistic action of the four elements, and which thus requires the passage of three hexaemeral days, as Gregory explains, before light becomes actually visible (see Chapter 2, section 2.3.1 and Chapter 3, sections 3.1.5, and 3.4.1). Light thus manifests in an exemplary way how the Platonic power causality and the Aristotelian natural causality are brought ‘in agreement’ within the framework of the hexaemeral metaphysics of creation. Basil’s combined reading of Plato and Aristotle is in tune with a broader harmonization tendency in late antique philosophy explored in detail by Karamanolis (2006). Basil confirms this tendency, with two caveats: 1) while a late antique Platonist turns to Aristotle to discover and elucidate Plato’s doctrines, as Karamanolis has shown, the scriptural exegete turns to Plato to elucidate Moses’ philosophy and to Aristotle to elucidate Plato; 2) the harmonization of Platonic and Aristotelian with Mosaic doctrines includes the explanatory principles of natural philosophy but not all fields of physics, as the rejection of the Aristotelian concept of aether clearly demonstrates (see Chapter 2, section 2.3.1 and Chapter 3, section 3.1.2). The harmonization thus involves both stages of ‘agreement’ distinguished by Golitsis (2018), an initial eclectic or ‘complementarist’ stage, in which certain doctrines of different schools are brought together, and a subsequent unifying or ‘concordist’ stage, in which the selected doctrines are harmonized with each other. The harmonization thesis is thus, in disguised form, the old ‘theft of philosophy’ argument, according to which all Greek philosophy is borrowed, ultimately and rather illegitimately, from Moses (see Sterling 2009; 2014). Applied to natural philosophy, the theft argument means that the principles of both Platonic and Aristotelian physics derive, ultimately, from Moses’ hexaemeral narrative. In dividing the principles of the Mosaic philosophy of nature between themselves, the philosophical schools distorted the vision of a unified account of nature, which is the aim of true philosophy. It is this unified vision that Moses gradually helps his reader regain (see Hex. III.8 GCS 53.5–20). Through the dual exegesis of light, Basil revives the Philonic project of a philosophical reading of Genesis but without the recourse to allegory. This is tantamount to implicitly claiming for the Cappadocian school the role of the mediator between Alexandrian spiritual exegesis and Antiochene anti-allegorism. To the educated reader Basil reveals himself to be a true master of biblical philosophy (see Nazianzen, Orat. 43.67; Nyssen, In Hex. 1 and 4). Basil’s dual exegesis of light becomes the linchpin of his hexaemeral philosophy of nature. It stumbles, however, upon a serious possible objection. In order to explain in what way lamprotēs is a quality of a fiery substance, Basil suggests an analogy with the colour white: just as whiteness is different from a white body, so is lamprotēs different from light’s underlying body. In both cases, Basil suggests, we must distinguish between a quality as such and its particular instances (VI.3 GCS 91.15–18). Implicit in this analogy is that a quality is an intelligible, hence invisible, universal. Only particular instances of a quality are accessible to the sense organs. We never see whiteness with our bodily eyes, only white objects. The analogy suggests that lamprotēs is, in itself, invisible. We only perceive an instance of lampron as the qualification, viz. the colour, of a fiery body. The analogy illustrates well the difference between the intelligible and the sensible aspect of light: the universal lamprotēs belongs to the work of day one while its particular instances belong to the work of day four. But the analogy also leads to a horrible dilemma: if lamprotēs is like whiteness and belongs to the category of colour, it must be an accidental attribute of light, hence not part of its essential logos, which is the work of day one. Conversely, if lamprotēs is

      ? 183 an essential property of light and as such belongs to the work of day one, it cannot also be an accidental attribute of light, hence part of the work of day four. For one cannot theorize a quality as both essential and accidental property of the same item without committing a fundamental category mistake. Basil’s analogy of lamprotēs with whiteness, then, is exposed to a notorious difficulty regarding the status of qualities in ancient philosophy: the problem of their possible double attribution as essential and as accidental predicates, an ambiguity widely discussed by late antique thinkers (see Simplicius, In Cat. 209.7–10; Radde-Gallwitz (2009), 164–5; Lloyd (1990), 93–4). For instance, Plotinus is happy to accept lamprotēs and whiteness as essential properties (sumplērōtikon ousias: ‘complement of substance’), yet not of the same item of which they are accidental properties (see Enn. II.6.1). He then takes this double attribution, sometimes essential and sometimes accidental, as evidence against the cogency of the Aristotelian system of categories: if all predicates are either substances or attributes, where do substantial attributes (‘complement of substances’) belong, into the category of substance or the other nine? (See Enn. II.6.2 and the discussion of Kalligas (2014), 336–56.) Porphyry too distinguishes between the essential and accidental attribution of the same quality in different items. He is less prepared than Plotinus, however, to do away with the Aristotelian categories. He thus identifies ‘complements of substances’ with ‘essential qualities’ (poiotēs oisiōdēs), a hybrid concept combining the notion of substance and qualifier (In Cat. 94.29–96.2). At the same time, he makes it clear that traditional examples of Aristotelian qualities, such as colours, do not fall into that hybrid: whiteness can never be an essential quality (96.14–22). It appears that Basil wants to have it both ways. If lamprotēs is part of the work of day one, hence of light’s intelligible aspect and essential logos, then lamprotēs is an essential property of light, a complement of its substance. If, however, lamprotēs is part of the work of day four, hence of light’s sensible aspect as its colour, then lamprotēs is an accidental property of light. The outcome of Basil’s exegetical strategy seems to be a combination that neither Plotinus nor Porphyry would allow, namely the conceptualization of a quality as both essential and accidental attribute of the same item—a conjuctium oppositorum. If so, the analogy of lamprotēs with whiteness obfuscates instead of elucidating the dual interpretation of light it aims to explain. In other words, it is a mistaken analogy. Or is it? To decipher Basil’s riddling analogy, we need to understand the relation of light and colours in the corpuscular ray theory to which the Cappadocians fully adhere. In this book, I have shown how the Cappadocian ray theory can be reconstructed if situated in the context of the Timaean explanatory framework and its reception history (see Chapter 3, section 3.2). I now suggest that we go back to the Timaean model in order to understand the relation of light and colours in the corpuscular theory. We can then apply the results to Basil. The basic contention of the corpuscular theory is that light is a fiery beam (augē) emanating from a light source. The beam can be theorized geometrically as a bundle of rays (aktines) or physically as a stream of fire particles (aporroē; see Aëtius, Plac. IV.13.1–17, IV.15.15–25, and my discussion in Chapter 3, section 3.2.3). In its Timaean version, the ray is a stream of pyramidal fire particles emanating from flame (Tim. 45b–d, 53c–56c, 58c). Similarly, colours are streams of fire particles (flox aporreousa), commensurate with light particles (summetra moria), emanating from the surfaces of things (67c–d; see also In Hex. 16 GNO 28.1–3). That means that light and colours consist of streams of fire particles with the same (pyramidal) atomic shape. The only difference between light and colours is the size of their respective particles: the smaller the size of the particles, the brighter the colour; the bigger the size, the darker the colour; particles of equal size with atmospheric light particles are neither brighter nor darker but transparent. It appears, then, that in the corpuscular theory colours represent grades of brightness, with the most brilliant bright (lampron te kai

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stilbon) defining the palette of colours at its extreme, the transparent (diaphanes) at the middle, and white and black at the two sides of the transparent (see Archer-Hind (1888), 248–9 n. 8; Cornford (1937), 277–8; Brisson (1997), 172; Struycken (2003), 275–6, 296–303; Ierodiakonou (2005b), 224–7; Sassi (2020), 25–7). On this account, brightness is a colour and so is transparency, for they are both streams of fire particles emanating from a body and producing a distinctive visual experience. Brilliant bright is the colour of pure fire, and transparency is the colour of ambient light (Tim. 67c–68c; see further Rep. 616e9–10 and Theaet. 208d2 on the brightness of the sun).¹ At this point, it should be noted that the Timaean model posits as criterion for the taxonomy of colours the particles of the ocular ray (opsis). But the ocular ray is light properly speaking: the ocular ray and the light ray are akin in source (adelphon) and alike in structure (homoion pros homoion), mixing homogeneously with each other (sumpages genomenon, hen sōma 45b–d). In terms of particle theory, the similarity entails that ocular light and sunlight have exactly the same atomic structure (shape and size). The identical structure explains why daylight is transparent (67d5). The qualitative identity also allows the reader to replace the ocular ray with the light ray as equivalent criterion for the taxonomy of colours. It therefore makes no difference if one theorizes colours by reference to the ocular ray or any other light ray. In both cases, one theorizes colours by reference to light. This explains the tendency in later interpreters either to subsume light and colours under the same genus (Ptolemy, Optics II.23) or to regard colours as species of light (Plotinus, Enn. I.6.3.24–8; II.4.5.10–11; Emilsson (1988), 53). By the time of the Cappadocians, the corpuscular ray theory has come to assume that light and colours consist of elemental particles of the same type differing only in size. Translated into logical predicates, this means that the identical shape of fire particles delimitates their common genus, while their variable size distinguishes between various species. Shape (genus) and size (differentia) of fire particles are the definitional properties of light and colours as species of fire. Further translated into hexaemeral physics, the corpuscular theory means that the work of day one is the creation of the ideal fire particle. Basil’s ‘nature of light’ (phōtos phusis II.7 GCS 32.1, VI.2 GCS 91.1–2) and Gregory’s ‘fiery and illuminating power’ (purōdēs kai phōtistikē dunamis 65 GNO 72.20), ‘illuminating nature’ (phōtistikē phusis 65 GNO 73.5), and ‘illuminating substance’ (phōtistikē ousia 69 GNO 75.13) are the hexaemeral equivalent to the Timaean pyramidal fire particle (54d–55a) together with its primary properties (56a–b). What is counterintuitive to the modern reader is that, in this account, colour is a fiery substance (‘flame flowing forth’), just like light (‘effluence from flame’). It is this peculiarity that makes Basil’s language of lamprotēs as both essential property (day one) and colour (day four) appear problematic. From within Basil’s metaphysical assumptions, however, there is no category mistake in this regard: the lamprotēs of

¹ The current tendency in scholarship is to doubt whether Plato constructs transparency as a colour in the Timaeus because transparent particles are ‘imperceptible’ (67d5). It would probably be better to say that transparency is colour-like. Transparent fire particles fully comply with the definition of colour given in Tim. 67c6–7, with the twist that they are not directly perceptible, since they do not cause any dilation or contraction of the visual current (hence ‘imperceptible’). Yet transparent particles are indirectly perceptible, being experienced as the illuminated medium (e.g. air or water) through which things appear. Aristotle expresses the same idea, and the same ambivalence, when he speaks of (ambient) light as ‘colour-like’ (hoion chrōma) in the De an. II.7 (418b11), but later drops the qualifier, speaking plainly of the ‘colour’ (chrōma) of the transparent medium, yet only incidentally so (kata sumbebēkos) in the Sens. 3 (439a18–19); see Caston (2012), 163–5 nn.395–9. Aristotle’s notion of light aims to capture the same visual phenomenon as Plato’s transparent light particles that fill the medium illuminating it. The Cappadocians too subscribe to the perceptibility of the transparent: the air becomes bright when illuminated and falls back into darkness in the absence of light (Hex. II.5 GCS 29.22–4; II.8 GCS 34.5–10; VI.9 GCS 103.14–18; In Hex. 25 GNO 38.6–17).

      ? 185 light is light’s differentia from other colours as fiery substances. The problems with this account lie elsewhere. For if colours are substances, how can they also be accidental properties of substances? Hence the first challenge: does the corpuscular theory intend to move colours from the list of accidental to the list of essential properties? Moreover, we have just seen that in the corpuscular theory daylight is transparent, while lampron is the colour of pure fire. Hence the second challenge: why does Basil speak of the lamprotēs (and not of the transparency) of light? I will answer the two questions in turn.

1. As regards the first question, the corpuscular theory of light and colours does not require the displacement of colours from accidental properties. On the contrary, if colours are fiery substances, bodies can very well have colours by having fire particles. That is indeed the doctrine we find in Tim. 31b: all bodies are characterized by two sensible properties, visibility and tangibility. Visibility is the peculiar characteristic of fire and tangibility of earth. All bodies are visible due to (and in the measure of) the presence of fire particles in their constitution, just as they are tangible due to the presence of earth particles. Since visibility is the capacity of fire particles to affect the visual current of a sentient being, and fire particles are perceived by the eye as colour, the premises of Tim. 31b and 67c–68c entail the basic principle that colour is the special sensible of vision (see Aristotle, De an. II.6 418a11–17). Visibility is therefore the consequence of colour and colour is the presence of fire particles in a particular thing’s bodily constitution (see Ierodiakonou (2005b), 223). That makes colour the sensible property of a particular thing qua body, not qua substance. Hence the seemingly paradoxical construction of colour as a necessary accidental property. The paradox disappears once we realize that in the corpuscular theory, what becomes sensible to the eyes as colour quality is in fact substances inhering in bodies (on the underlying Anaxogerean echoes see Denyer (1983); Barnes (2001), 54–7; Marmodoro (2017), 24, 42–3; for the patristic reception history see the voluminous study of Tzamalikos (2016)). With this caveat, the accidental predication of colour holds perfectly within the corpuscular theory. There is, however, one possible objection regarding the colour of fire particles themselves as a limiting case. For fire particles are bodies (sōmata 53c4–5), and qua bodies they ought to have colour (tōn sōmatōn hekastōn 67c5–6). But fire particles seem to be colour, since their atomic structure defines the genus (shape) and differentia (size) of light and colours. Hence the logical conundrum: do fire particles emit further fire particles—does colour produce colour, and with it an infinite regress? Or do the rules of predication collapse in the case of fire particles in the sense that they are and have colour at the same time and in the same respect, eradicating the difference between essential and accidental properties? Clearly, there is no regress. Fire particles are just that, namely (perceptible as) colour. But what about the possible collapse of the rules of predication? Here too nothing of the sort happens, but to see why we need to supply certain implied premises of the corpuscular theory. Theorizing fire particles as colour presupposes the identity of colour with fire particles. The identity can be further refined. Colour is defined as ‘a flame flowing forth from bodies’ (Tim. 67c6–7). A flame is an aggregate of fire particles. The properties of an aggregate include but are not identical to the properties of its members. In the case of flame, or any aggregate of fire particles for that matter, the essential properties of the aggregate are determined by the atomic structure of its fire particles. But there are also other properties of the aggregate which are determined by accidental factors, such as the homogeneity and

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the quantity of its constitutive fire particles. That homogeneity (or admixture as its opposite) co-determines colour properties is clear from the account of mixed colours (Tim. 68b5–d7). That quantity co-determines colour properties is clear from the difference of the illuminating power of the sun compared to the rest of the heavenly bodies (Tim. 39b6–7, 45c2–4, and d3–6; see also Rep. 508c4–9, 514a1–517a7, 532a1–c4; see also Hex. VI.9). Implicit in the Timaean account of colours is then the assumption that, if colour properties are streams of fire particles, colours are not determined by the atomic structure of each fire particle individually, but by the structure of the stream of fire particles emitted as a whole. To the structure of the whole belong also the number and the multiple possible kinds of particles emitted by a body. If we now ask how atomic structure, quantity, and homogeneity of fire particles determine our visual experience of colour, we may arrive at the following answer: the atomic structure of homogeneous fire particles determines colour purely according to degrees of luminosity/opacity (hues of primary colours, e.g. white, red); the number of fire particles determines the intensity of colour (colour saturation, e.g. a fainter or stronger red); and the admixture of fire particles determines mixed colours and the purity of hues (e.g. yellow, purple; a red leaning towards yellow or towards purple). If we further ask what determines the size, quantity, and homogeneity of fire particles, we may reasonably assume that the answer lies in the material composition of the underlying body (cf. Theophrastus De igne 30–1). We thus gain the following picture: the particular colour of a body is the result of the atomic structure of the fire particles it emits, due to the presence of fire in it. While fire is part of a body’s material composition, the quantity and uniformity of fire particles that a body emits is determined by the co-presence of the other three elements in it. In the case of fire, the determining body is its underlying burning material (see Chapter 3, section 3.1.4). If we accept the above premises (or equivalent), we have all we need to distinguish between essential and accidental properties of fire particles qua colours. The atomic structure of fire particles determines their lamprotēs in the sense of luminosity. Luminosity is how the essential properties (shape and size) of the fire inhering in a body become visible. At the same time, the material composition of the underlying body determines the intensity and purity of the stream of fire particles it emits. The intensity and purity of luminosity is how the accidental colour properties of the fire inhering in a body become visible. The (essential) luminosity together with the (accidental) intensity and purity of a stream of fire particles become visible as colour, the most acute instance of which is the lampron te kai stilbon, now in the sense of the bright brilliant colour of pure fire. On this reading of the Timaean model, and with the prevailing view, colour is defined by the size of fire particles that a body emits (differentia). But going beyond the prevailing view, colour also depends on the quantity and homogeneity of the fire particles that a body emits (accidental properties). With these qualifications, the distinction between essential and accidental predication holds perfectly even for the limiting case of the colour of fire. Much more than that, we are now able to understand more fully Basil’s notions of lamprotēs and lampron. In the sense of ‘luminosity’, lamprotēs is the essential property of light and colours and belongs to the work of day one. In the sense of ‘brilliancy’, lamprotēs is the colour of a particular flame, namely the pure flame of the heavenly bodies, most notably the sun, as the combined product of the luminosity, intensity, and purity of the flame’s particles. The individualization of the latter properties depends on the underlying body (hupokeimenon sōma), which provides a flame with the necessary burning material. Since fire cannot feed on fire, the burning material requires the combined presence of the other three elements. This explains why the underlying body has to be the work of day four, as the first work of the combined activity of the four elements.

      ? 187 To sum up, the deciphering of Basil’s dual function of lamprotēs requires us to go beyond the surface of the Timaean explanatory model and supply its implied premises. Though every reconstruction of the Timaean atomic physics relies on some reasonable amount of speculation, we do not need to assume that the above premises are necessarily implied by the Timaean model itself. We only need to assume that these are the premises supplied by the Cappadocians when they apply the corpuscular theory of light and colours to their hexaemeral exegesis. With these premises, Basil’s double construction of lamprotēs as essential luminosity and accidental brilliancy is coherent and consistent with his dual hermeneutics of light: lamprotēs as the essential luminosity of fire is the work of day one; lamprotēs as the accidental bright colour of heavenly fire and its light is the work of day four. The analogy of lamprotēs with whiteness now yields its full explanatory power: if colour is the proper sensible of vision, and if fire acquires a particular colour only after it has obtained a material substratum on day four, the fire of day one cannot yet be seen by bodily eyes—it can only be contemplated by the mind’s eye. This is indeed the case of the ideal fire particle. It is the ideal fire particle, the beauty of paradigmatic light, that is the sole object of intellective vision. Basil hints at this kind of vision through his exegesis of Gen. 1:4: God contemplates the beauty of light (Hex. II.7), surely not with bodily eyes (cf. Hex. III.2 by analogy to God’s speech). The hexaemeral tradition makes the same point by stressing the role of angel-sight in creation: the angels, being intellective creatures, contemplate creation with intellective eyes (see Chapter 1, section 1.3.1). They contemplate light metaphysically, i.e. light as the condition of perceptibility of the world as a phenomenal reality (phantasia– phainomenon, see Chapter 1, section 1.4.3). This is the work of day one.

2. I have just argued that the essential property of fire is luminosity, which varies according to the size, number, and diversity of fire particles emitted by the underlying body. The difference in degrees and kinds of luminosity becomes visible as the variety of light and colours that we see in nature. On this interpretation, the most brilliant case of brightness is the colour of pure fire, which in a late antique universe corresponds to the fire of the heavenly bodies. Light too is a species of fire (Tim. 58c5–7; Hex. II.7 GCS 32.1–2 and VI.2 GCS 91.1–11; In Hex. 12 GNO 22.15–20 and 65–7 GNO 72.16–74.20; and my discussion in Chapter 3, section 3.2.3). As such, it exhibits the luminosity and colour of fire. More specifically, since light is the effluence of flame, it shares in the particular luminosity and colour of the flame that produces it (Tim. 58c6, 67c6–7). The basic colours of fire in the Timaean model are brilliant bright, white and red (and, in a sense, black). These are indeed the basic colours of light that we see in nature: the bright light of the sun in midday, its reddish light during sunset, or the white light of the moon (and the deep black of the aether of the night sky). Then again, the planets and the stars in the night exhibit light in different colours, according to the composition of their underlying material, correlative to the place they occupy in the universe (see Chapter 3, section 3.1.4). Yet beams of light in themselves are usually perceived as bright white, as when for example the rays of the sun break through dark clouds or when a beam enters through a window in a dark room (the example becomes canonical in the study of the properties of light; see Marcus Aurelius, Meditat. VIII.57; Origen, DP I.1.6 GCS 20.24–21.5; Gregory, In Hex. 48 GNO 61.8–15). Apart from the Timaean account, there are numerous other examples of the association of light with a bright white in ancient physics, especially in Democritus and the Aristotelian corpus (see Struycken (2003), 279, 285, 287, 298–9, 301–2). We also find the same association in the

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Gospel narratives of the transfiguration (Matt. 17:2; Mark 9:3; Luke 9:29) and of the empty tomb (Matt. 28:3; Mark 16:5; Luke 24:4; John 20:12). The association of light with the colour white is therefore normative for the hexaemeral authors. To the above should also be added that daylight is perceived neither as brilliant bright nor as bright white but as bright transparent. This too is clearly documented in the sources (see Tim. 45b4–d3 and 67d4–5; De an. II.7 418b4–13; Sens. 3 439a17–27 and 439b1–2). We thus have a variety of colours of light: brilliant bright at the source, bright white in the ray, and bright transparent in the air. This is important: in drawing the analogy between brilliancy (lamprotēs) and whiteness (leukotēs), Basil is not drawing a chance analogy between the colour of light and another colour. He is drawing an analogy between two different phenomenal aspects of the colour of light: the colour of light at the source and the colour of light in the ray. The variety in light’s phenomenal colour properties requires a rational explanation: is light really changing colour according to its surrounding conditions or does light merely appear to change colour, while its proper colour remains the same? The question brings us to the second challenge raised above regarding the colour of light. Clearly, the difference between the brilliant, the white, and the transparent colour of light is to be explained in terms of the size of its fire particles: fire particles at the source are smaller in size, greater in number, and unmixed. Conversely, the size of fire particles becomes bigger, weaker in intensity, and mixed with other particles the further away a ray travels from the source. That means that the difference in light’s phenomenal colour properties is reducible to the atomic structure, intensity, and purity of its particles, according to the rule of ‘division’ (diakrisis) and ‘compression’ (sugkrisis) underlying the Timaean theory of colour (67d2–e6) but also the Timaean theory of elemental transformations (56e7–57b7, 58b7; see Ierodiakonou (2005b), 225–6). The rule can sufficiently explain why a beam of light that enters a dark space through an opening appears bright white: as a new stream of fire particles penetrates an area of dim light, that area acquires a large quantity of bright fire particles, becoming more luminous. At the same time, the bigger air particles present in the illuminated area compress the smaller fire particles of the beam, forcing them to recombine into bigger particles, which is the reason why the colour of a beam of light is bright white rather than the brilliant bright of the source. The rule of division and compression can explain the change from brilliant to white and transparent as a change in the size of the light particles. But it cannot explain transparency itself. For air particles are octahedral, while fire particles are pyramidal. The air particles of an area filled with light should normally interrupt the visual current, not being commensurate with it. The rule of division and compression tells us how the size of fire particles changes according to the presence of air particles, not how air particles change into fire particles. It is therefore not sufficient to explain how we can see through an area filled with light. What the Timaean theory of the transparent still needs is an account of how air particles acquire the same shape and size as the fire particles of the visual current, without however turning into fire particles (or there would be no air left to breathe in daylight). Let me here suggest without further proof that there is a geometrical solution that satisfies these requirements. All we need to do is postulate that the pyramidal particles of the ray mingle with the octahedral particles of air in such a way as to produce a supervenient polyhedral structure in the shape of two interlocking pyramids of double the size of the original fire particles (so-called ‘stellated octahedron’ or ‘star tetrahedron’). This explanation fits well with the explanatory principles of the Timaean atomic theory, which reduces all interactions of the four elements to the interactions of the five Platonic solids. It also satisfies the conditions of the Timaean theory of vision, light, and colours. What it means is that when a light ray travels through an area with air illuminating it, the fire particles of the ray and the air particles in that

      ? 189 area mingle with each other in such a way as to fulfil the requirements of (Timaean) transparency. On this explanation, the atomic structure of both fire and air particles is preserved, while the octahedral air particles are now enclosed or ‘clouded in’ a tetrahedral, hence luminous, shape. The result is that the air ‘takes on’ the colour of light. In more technical language, the transparent colour of illuminated air is the epiphenomenal colour of the ray in the medium (see Chapter 3, section 3.3.2). The difference between the ray’s real and epiphenomenal colour properties presupposes a helpful distinction, introduced recently by Kelsey (2018) and employed often in the argument of this book (see especially Chapter 3, section 3.3), namely the distinction between ‘radiant’ and ‘ambient’ light. The ray is radiant light. Illuminated space is ambient light. Radiant light is intrinsically brilliant bright; ambient light is bright transparent. Radiant light is more or less brilliant, according to the degree of luminosity of its source. As it travels through space, radiant light becomes more or less transparent, according to the ability of the particles of the medium to mingle with the ray. At the same time the ray illuminates the medium without, however, suffering any real change in the atomic structure of its particles. The result is ambient light as the epiphenomenal colour of the medium in the presence of radiant light. The distinction between radiant and ambient light is implicit in both Plato’s and Aristotle’s theory of light. In the Timaean account of the species of fire, Plato describes the ray as ‘the effluence from flame which, while it does not burn, gives light to the eyes’ (58c6–7). The effluence (to apion, literally: ‘what proceeds’) from flame is the ray, the light radiated from a luminous source. It is this radiant light that is the agent of vision bringing ‘light’ (phōs) to the eyes. The ‘light’ that the ray brings about is ambient light, the illuminated space that enables vision, the ‘daylight’ of Tim. 45b4–d3. This allows us to understand a peculiarity of the Timaean account of light: radiant light and ambient light are both ‘light’ but in a different sense. To avoid the problem of equivocity, Plato only names ambient light in 45b4–d3 and 58c6–7, leaving radiant light anonymous and referring to it by its genus (fire). Aristotle exploits the ambiguity to the full. His account of light as ‘the actualization of the transparent’ in the De anima II.7 is an account of ambient light— the very same for which Plato used the name ‘light’ in the Timaeus. At the same time, his criticism of the Empedoclean-Timaean theory of light in the De anima II.7 and the De sensu 2 is a criticism against the corpuscular notion of radiant light. Yet, elsewhere, Aristotle expounds on his own notion of radiant light, in order to account for reflection (Meteor. III.2–4). The distinction between radiant and ambient light is therefore another implied premise of the corpuscular theory of light and colours. This time it is a genuine premise of the Timaean theory itself, one that has often escaped attention, but one which yields tremendous explanatory power when it comes to understanding the connection between the Platonic and the Aristotelian theory of light. As one would expect, it is also a distinction underlying the Cappadocian exegesis of light. In the Cappadocian scheme, Gen. 1:3–4a refers to the appearance of radiant light in the world as the power of fire, equivalent to the Timaean ‘effluence from flame’ (Hex. II.3 GCS 26.3–5; VI.2–3 GCS 91.1–92.9). By contrast, Gen. 1:4b–5 refers to the separation of light from darkness and of day from night in the sense of ambient light, equivalent to the Timaean and the Aristotelian ‘light’ (Hex. II.8 GCS 34.5–10; VI.9 GCS 103.17). We may thus conclude that Basil’s radiant light is per se brilliant bright (lampron). When it fills the air, however, it is perceived as bright transparent, allowing the perception of colours to occur (see Chapter 3, section 3.3.2). Gregory further clarifies Basil’s doctrine. Many sections of the later part of the Apology are dedicated to the explanation of the distinction between the genus and the species of light (In Hex. 65–73 and my discussion in Chapter 3, section 3.4.1). The work of day one is the creation of ‘universal and generic light’ (72 GNO 78.2). The work of day four is the

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emergence of ‘all the species of luminous substances, including the sun and the moon’ (73 GNO 79.16–17). These luminous substances are the planets and the stars, which are allocated to their natural places in the heaven: the sphere of the infinite fixed stars at the outskirts of the universe (72 GNO 78.11–13); and the seven circuits of the planets in the vast regions of space covering the distance between the sphere of the fixed stars and the earth (66 GNO 74.10–11; 72 GNO 78.8–22). The allocation occurs according to a process of division of the genus fire into its numerous subspecies: each subspecies consists of kindred fire particles; each collection of kindred fire particles forms a luminous substance, i.e. a heavenly body (65 GNO 73.2–4; 66–7 GNO 74.11–16; 72 GNO 78.8–12). The closer a heavenly body is to the earth the more it consists of heavier, non-fiery particles (66 GNO 74.2–67 GNO 74.19; 70 GNO 77.6–13; 72 GNO 78.1–22). This too is fully in accord with Basil’s theory that the luminosity of a fiery body depends on its material composition. As already explained, the underlying premise is that fire particles acquire different size according to their interaction with air, water, and earth particles either as natural elements or in the composition of bodies. That explains further the nature of the ideal fire particle as the work of day one: if fire particles acquire their particular size as they interact with the other elements, quantifiable size is not part of the logos of fire. In other words, the ideal fire particle has no particular size. It is only a mathematical abstraction expressed in pure ratios, namely the proportions of its sides (see Pohle (1971), 46; Drummond (1982), 65–6). The ideal fire particle is a pure ratio and, in that sense literally, the logos of fire. It acquires quantifiable size as the result of fire being part of the composition of bodies. Bodily composition is, in turn, a function of the natural place of the four elements in the universe and the necessary displacement caused by the interaction of the elements with each other, so that all bodies have a part of all four elements but in different proportions. The passage from the ideal fire particle to its quantifiable physical instances is the passage from day one to day four of creation (65 GNO 73.2–9; 73 GNO 79.15–17).

APPENDIX C

‘Light from Light’, or What Is the Meaning of Doxa and Apaugasma? For she is a breath of the power of God, and a pure emanation (aporroia) of the glory (doxēs) of the Almighty; therefore nothing defiled gains entrance into her. For she is a reflection (apaugasma) of eternal light (photos aidiou), a spotless mirror of the working of God, and an image of his goodness. (Wis. 7:25–6 RSV) For she is the brightness (apaugasma) of eternal light (photos aidiou), and the unspotted mirror of God’s majesty, and the image of his goodness. (Wis. 7:26 DRA) He is the radiance (apaugasma) of the glory (doxēs) of God and the exact imprint (charaktēr) of his nature . . . (Heb. 1:3 ESV) He is the reflection (apaugasma) of God’s glory (doxēs) and the exact likeness of his being . . . (Heb. 1:3 ISV) who being the brightness (apaugasma) of His glory (doxēs) and the express image of His person . . . (Heb. 1:3 NKJV) There is one glory (doxa) of the sun, and another glory of the moon, and another glory of the stars; for star differs from star in glory (en doxēi). (1 Cor. 15:41 ESV) The sun has one kind of splendor (doxa), the moon another and the stars another; and star differs from star in splendor (en doxēi). (1 Cor. 15:41 NIV) Appendix B helps us decipher an enigmatic term used by Gregory to describe different degrees of brilliancy of the heavenly bodies, i.e. their doxa. The glory (doxa) of the sun, says the Apostle, is different from the glory of the moon, which is different from the glory of the stars. For one star differs from another in glory (diaferei en doxēi) so that there is indeed a great variety (diafora) of light. (65 GNO 73.12–14) The use of the term doxa in this context is scriptural, and more precisely Pauline (1 Cor. 15:41). Its common translation as ‘glory’ indicates that it is not the Platonic doxa (‘opinion’) that Gregory here invokes. Yet the juxtaposition of the genus of light created in day one and the phenomenal variety of the starlight of day four also evokes the poikilia (variety) of the Platonic heavenly realm, which despite being the most harmonious and beautiful part of the

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sensible realm of doxa is still characterized by diversity (Tim. 40a2–7), hence lack of perfection (in the sense of lack of absolute brilliancy; see Philo in Opif. 30) compared to the realm of ideas (Rep. 404e3–5, 529c6–530b5). Thus, the language of doxa is scriptural but its cosmological connotations are Platonic: Gregory’s term diaphora has the same meaning as the Platonic poikilia and the beauty of the heavenly realm consists in the brilliancy of its light. Doxa then denotes the particular degree of luminosity of each heavenly body, i.e. its distinctive brilliance. This interpretation goes back at least to Origen, who in his hexaemeral homily already works out the direct connection between the ‘glory’ language of 1 Cor. 15:41 and the exegesis of Gen. 1:16–19, for the purposes of an analogy between the various degrees of brilliance of the heavenly stars and the degrees of brilliance of the saints (Hom. Gen. I.7). The subtext is clearly that of the luminous theophanies of the glory of God, the Kabod Jahwe (‫)כבוד יהוה‬, which in early rabbinic Judaism gave rise to the idea of the Shekinah (‫ )שכינה‬as light (Kohler and Blau (1905), 259; Goldberg (1969), 468–70; Chilton (1983), 69–77; Urbach (1987), 44–7; Putthoff (2017), 164–6). Like the targumists but following Paul, Origen identifies the doxa of Wis. 7:25 and Heb. 1:3 with the ‘eternal light’ of Wis. 7:26, in a clear indication that he understands the scriptural references to the glory of God as references to light (see Hom. Jer. 9.4 GCS 70.17–28 [= Fürst/Lona 264.1–12]; DP I.2.9–12; and the fragments from the Commentary on Hebrews in Pamphilus’ Apology §§50, 97, 99, to which §§60 [= DP I.2.11] and 64 [= Hom. Jer. 9.4] are added). Origen’s identification indicates the broader hermeneutic principle, shared by several biblical scholars today, that passages in the Apocrypha and New Testament which mention or imply radiance, and in which the Greek text reads doxa (e.g. Mark 8:38; Luke 2:9, 9:32; John 1:14, 12:16; 2 Cor. 4:4; Heb. 1:3 etc.), import the old theophanic theme of the divine presence as radiant light in a Greek linguistic context, applying it to Christ (see Bourke (1961a); (1961b), 496–7; (1961c), 185, 195–7; DeConick (2011), 308–11; Orlov (2019), 79–189). Similarly, the vision of God’s Kabod/glory as brilliant and radiant light is a theme prominent in the early Christian mystical tradition inherited by the Jewish apocalyptic literature (Orlov and Golitzin (2001); Stroumsa (2006); DeConick (2006); Giulea (2010)). Following a different trail, Werner Beierwaltes concluded his doctoral dissertation on the ancient metaphysics of light with an incisive Appendix on the semantic connection between doxa and light in Scripture and in the Greek patristic corpus (Beierwaltes (1957), 107–110). Beierwaltes argued that the meaning of doxa is ‘Lichtglanz’, i.e. radiant or brilliant light, and concluded that it is in this sense that the term figures in Heb. 1:3 describing the Son as the apaugasma tēs doxēs tou patros (110). Thus, through a fascinating thread of parallel Jewish and Greek associations we come to the meaning of doxa in Heb. 1:3, one of the key passages discussed in the fourth-century trinitarian debates. As we just saw, Gregory clearly indicates that doxa means brilliance, the equivalent to Basil’s lamprotēs. In terms of the corpuscular theory, doxa denotes the colour of pure fire/light. Besides doxa, Heb. 1:3 introduces another light term from Wisdom literature, i.e. the notorious apaugasma of Wis. 7:26, which would become the apple of discord in the fourthcentury trinitarian debates. Modern translations of the term are split between an active sense of ‘radiance’ out from the luminous source and a passive sense of ‘brightness’ as a reflection back to the source, with the precise attribution in each context remaining ambivalent (see Bauer (1988), ad loc.; O’Collins (2012), 114). The ambivalence is justified by the Greek language, since the root word augē denotes in general ‘sunlight’, which can mean either radiant light (as e.g. in Plato, Phdr. 250c4) or ambient light (as e.g. in Aristotle, Sens. 439b2). Indeed, the Alexandrian lexicographer Hesychius in his Lexicon preserves the sense of apaugasma as hēliou feggos, i.e. ‘sunshine’, which means, like augē, either the sun’s radiant light or the sun’s brightness. As already explained, radiant light is the light ray

        ? 193 emanating from the luminous source (hence the identification in many sources of augē with the ray), while ambient light is the change in the epiphenomenal colour of the medium from dark into bright. In the latter sense, augē and apaugasma denote the brightness of the illuminated medium caused, for those following the corpuscular/ray theory, by the motion of the ray in it. Thus, in both senses (radiant and ambient light) the apaugasma of Wis. 7:26 and Heb. 1:3 denotes the transmission of the doxa, viz. brightness, of the luminous source in space. In the case of radiant light, the emphasis is on the emission of brightness through the ray. In the case of ambient light, the emphasis is on the illumination of space. As already shown in Chapter 3, section 3.3.3, from the point of view of physics the emission of light and the illumination of space are one and the same reality in the world, namely the activity of the ray in the medium. From the point of view of metaphysical causality, however, radiant and ambient light predicate the same reality differently: radiant light describes the propagation of light from cause to effect, as the productive power of fire, while ambient light describes the same causal change from effect to cause, as the product of the activity of fire’s power. Thus, both senses are possible, equally valid, and metaphysically important. But only one sense is recorded in the later sources. The byzantine lexicographical and hagiographical tradition typically identifies the apaugasma only with the light ray, i.e. with radiant light (hē aktis tou hēliou, see ps.-Zonaras, Lexicon, ad loc.; Nikephorus (?), Vita Andreae 36.3168 (Rydén 216); Bryennius, Orat. IV.76–7). Tellingly, the later byzantine lexicon of Suida records only the sense of apaugasma as radiant light: he eklampsis (‘the shining forth’). As will be shown in the remainder of this Appendix, the elimination of the alternative sense of ambient light from literary memory seems to happen during the fourth-century trinitarian debates for theological reasons. Let us first go back to Gregory and see how he uses the term. In his anti-Eunomian writings, Gregory clarifies that the apaugasma has the meaning of physical emanation (hulikēs aporroias), like odour and breath (CE III.6.37, 39). He clearly has the meaning of radiant light in mind linking Wis. 7:25 (aporroia tēs doxēs) with Wis. 7:26 (apaugasma photos aidiou), which he approaches as an interpretative unity following Origen’s lead. He also provides a further clarification, which should be quoted in full: Furthermore, as the glow of light (hē tou photos lampēdōn) radiates (apaugazetai) from the whole solar disc (for one part of the disc does not shine while another remains dim), just so the whole glory (doxa), which is the Father, radiates all round (periaugazetai) with the radiance it emits (tōi apaugasmati), that is, with the true Light; and as the ray (aktis) comes from the sun (for there would be no ray if there were no sun), yet the sun is not thought of by itself without its radiated ray (apaugazomenēs aktinos), so in communicating the bond and eternity of the existence of the Only-begotten from the Father the Apostle calls the Son ‘radiance of glory’ (apaugasma tēs doxēs). (CE III.6.14, tr. Hall, modified) The passage is extremely informative: Gregory regards the glow or sparkle of light (lampēdon) as equivalent to the ‘doxa, which is the Father’. Stuart Hall (2014), 115, translates hē tou photos lampēdōn in this context directly as ‘the brilliance of light’. Gregory thus confirms that Kabod/doxa denotes the brilliant bright colour of light, which is transmitted in ambient space through the ray. As explained in Appendix B, however, there is a gradual shift from brilliant bright to bright transparent in light’s phenomenal properties as the ray travels through space: the closer the ray is to the source, the purer and more intense its radiation, giving off a luminous aura, whose brilliance turns to transparency the farther away the ray travels from the source. That luminous aura is the disc of light surrounding the sun and the stars, known as the corona, aureole, or halo of a luminous

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body (see e.g. Aristotle, Meteor. III.2 371b22–6; Seneca, NQ I.1.2). While in the Peripatetic tradition the halo is regarded as an optical phenomenon due to the reflection of vision from the moisture which condenses round the luminous source (Meteor. III.3 372b12–373a31), in the corpuscular theory the halo is theorized as a real phenomenon, due to the interaction of light with air particles (see Taub (2003), 164). Clearly, the ancient corpuscular theory fuses several natural phenomena into one: the diffraction corona (or aureole) with the refraction halo, which are parhelic phenomena of the upper atmosphere (see the brilliant discussion of Stothers (2009)); and the stellar corona, i.e. the aura of plasma that surrounds the sun and other stars and may extend millions of kilometres into outer space. While the aureole and the halo are mere optical appearances, the stellar corona is a real physical phenomenon, most easily seen in a total solar eclipse. Ancient authors do not seem to distinguish between these phenomena. They regard the radiant disc of light surrounding a luminous body as a continuous phenomenon. It is precisely this phenomenon of gleaming light emanating like a circle or disc from the source that is the reference of Gregory’s periaugazetai. That makes the apaugasma the aura of the light source. This interpretation can be traced back to Philo (Somn. I 239), who uses the analogy of the logos to the stellar corona (anthēlios augē) and the halo of the moon (tas peri selēnēn halōs). Dölger (1929), 273, rightly intuits that the same imagery is denoted by the term apaugasma in Opif. 146, following the terminology of Wis. 7:26 and anticipating that of Heb. 1:3. If so, the apaugasma is the total sum of light rays emanating from the source (apaugazomenēs aktinos), visible as the luminous aura surrounding any natural light source, like the sun and the stars, or as the gentle halo of a simple candlestick burning in the dark. In the corpuscular theory, this aura is spatially connected to the light source giving the visual impression of a physical effluence of flame, theorized either as an emanation (Platonist model) or an extension (Stoic model) of the fiery source in its surrounding space. If we now approach the fourth-century trinitarian debates with this insight in mind, we may understand something of the dialectical subtlety of the controversy over the meaning of apaugasma. Before the Arian controversy started, in the often quoted but mistranslated passage of DE IV.3.1–9 GCS 152.20–153.25, Eusebius of Caesaria entertains both meanings of apaugasma as radiant and ambient light. As radiant light, the apaugasma denotes the ray (aktina) that fills and illuminates everything (ta panta plērousan kai katalampousan). As ambient light, it denotes brightness (augē), light’s colour as the necessary accidental complement of light’s essence (sumplērōtikē tis ousa autou; kata ti de tēs ousias sumbebēkos achōriston). Eusebius can entertain both senses because, as already mentioned, the ray and illumination of space are two equally valid though causally different ways of predicating one and the same illuminating activity of the luminous source. Eusebius knows his metaphysics of light well: ‘brightness occupies the place of light’s activity’ (photos hē augē chōran energeias epechei). It is interesting to read some of Arius’ passages with Eusebius’ double interpretation in mind (see for the passages Stead (1978), 25–38; Williams (2002), 95–116). In the second chunk of the Thalia that Athanasius preserves in the Synodis 15, Arius is reported as predicating the Son as apaugasma and phōs. The two terms are commonly translated as ‘radiance’ and ‘light’. But why assume that apaugasma and phōs mean radiant light here? Hanson (1988), 15, by contrast, translates apaugasma in the passive sense as ‘reflection.’ His intuition is on the right track. In fact, it would be much more consistent with Arius’ premises to assume that apaugasma in this context denotes ‘brightness’ and phōs denotes ‘ambient light’. Several hints strongly suggest that the Son is indeed understood as equivalent to ambient light in Arius’ interpretation of Wis. 7:26 and Heb. 1:3) the Son as the product (ktisma in Urk. VI.2) of the Father’s will (theou thelēsei in the second chunk of the Thalia in Synodis 15) resembles ambient light as the product of the

        ? 195 activity of the ray; 2) the distinction between two senses of ‘light’, radiant and ambient, perfectly matches Arius’ doctrine of two Words (logon heteron) and two Wisdoms (duo sophias) reported in the first part of the Thalia (C.Ar. I.5); 3) Arius’ seemingly ambivalent phrases in C.Ar. II.19 ‘creature (ktisma), but not one of creatures’; ‘product (poiēma) . . .’ etc.; ‘offspring (gennēma) . . .’ etc., actually are very accurate descriptions of the double function of ambient light as the product of the activity of the luminous source and a cause itself of the visibility of colours. Ambient light is itself a cause because it enables colours to be seen. It is also something caused, being the product of the presence of fire in the medium. In Aristotle’s tripartite scheme of physical causality, it occupies a median position: if fire is the first potentiality of visibility, and colours are the second actuality, ambient light is the second potentiality and first actuality. As second potentiality it resembles fire and belongs to the side of causes. As first actuality it resembles colours and belongs to the side of products. In that sense, one can speak of ambient light as a-cause-and-not-a-cause; aproduct-and-not; and as the beginning and principle of production (archē tōn genētōn, Thalia v.6 apud Synodis 15). Colours delineate surfaces and thus describe particular beings. If colours are analogous to particulars, ambient light analogous to Christ, and fire analogous to God, then ambient light offers a perfect analogy for what we know of Arius’ median role of Christ between God and creatures. Arius’ metaphysics of light is not wrong. It is only one-sided, describing the chain of causation bottom-up, from effect to the cause. Athanasius on the other hand, describes the chain of causation from the opposite side, i.e. top-down, from cause to effect. On Athanasius’ predication of the causal chain, the apaugasma of Wis. 7:26 and Heb. 1:3 can only denote radiant light. Predicated top-down (from cause to effect), the illuminating activity is the emission of the ray as the power of the luminous source (radiant light). Predicated bottom-up (from effect to cause), the illuminating activity is the change in the colouration of the medium as the product of the ray’s presence (ambient light). Radiant and ambient light describe the same reality in two different respects. We find both respects still present in Eusebius’ interpretation of Wis. 7:26 and Heb. 1:3, written before the Arian controversy broke out. After the controversy started, the different camps exploited the double predication of the chain of causality for their own theological purposes. Non-Nicene and anti-Nicene theologians understood the analogy of Christ to light bottom-up, from creation to God. From their perspective, the apaugasma was rightly identified with ambient light as an explanans of Christ’s double status as caused and cause. By contrast, Nicene and pro-Nicene theologians understood the analogy of Christ to light top-down, from God to creation. From their perspective, the apaugasma was rightly identified with radiant light as an explanans of Christ’s double status as caused and cause. It is the latter identification that is recorded in the catenist tradition (see the texts quoted on Heb. 1:3 and 1:8 from the Cod. Par. 238 in Cramer VII.300.15–305.34 and 342.34–363.23), which also sets the tone for the byzantine literary tradition. The latter perpetuates the (pro-)Nicene interpretation of the scriptural apaugasma passages, while it passes over in silence the alternative interpretation, now considered as ‘heretical’. Both interpretations describe the same reality from opposite starting points, resulting, by way of analogy, in opposite theological positions. Both interpretations are from their own premises correct. Both interpretations are, however, one-sided, each obscuring the validity of the premises of the other. In that respect, they are both wrong. The polemics over the interpretation of the apaugasma becomes a fine example of how the fourth-century trinitarian debates exploited the internal dialectics between the physics, the metaphysics, and the scriptural hermeneutics of light to serve the needs of a theological controversy (see also Dölger (1929), 284–5; further Stead (1976); Anatolios (2006); and Katsos [forthcoming]).

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Going beyond the theological polemics, the idea that a light source is surrounded by its light is quite common in the ancient sources. The vocabulary of periaugazō and periaugē in the sense of ‘surrounding light’ is widely attested, to which the vocabulary of perilampō and perilampsis should be added as synonyms. It is interesting to notice how the idea is shaped in Plotinus. In Enn. V.3.9, Plotinus speaks of the Soul as an image of Intellect ‘like the light of the sun which shines around and out of it (to peri autēn kai ex autēs lampon), beyond its spherical mass’. Elsewhere, he gives the following description of natural illumination: For there is something like a centre, and in addition to it a circle shining from it, and in addition to these another circle, light coming from light (phōs ek phōtos). (Enn. IV.3.17) The passage is traditionally considered to contain an analogy from light for the three Plotinian hypostases, the ‘One’, the ‘Intellect’, and the ‘Soul’. This is correct, but the analogy presupposes some physical phenomenon. Given that Plotinus dematerializes the images that he uses from the physical world in his anagogical thought experiments of being according to the technique described in Enn. II.9.17, V.8.9, VI.4.7, etc., it is possible to reconstruct the physical model underlying the passage by reversing the process of dematerialization. Applied to the sun, the analogy yields the solar disc as a luminous sphere extending around an invisible centre and surrounded by the sun’s luminous aura (see V.1.6.28–30, V.3.9.8–15, and VI.4.7.22–47). If so, the Plotinian formula ‘light from light’ (phōs ek photos: IV.3.17.13–14 and VI.4.9.26–7) corresponds to the apaugasma of Heb. 1:3, namely the luminous aura surrounding the sun. As we saw, the image of apaugasma lies also in the subtext of the Nicene formula ‘light from light’. It appears, then, that in the Platonist and the Christian tradition the expressions apaugasma photos/apaugasma doxēs and phōs ek phōtos denote the same thing (as already intuited by Stead (1976), 35 and intimated by Ayres (2004), 23). If so, the formula ‘light from light’ referred to the physical emanation of the ray from a light source but acquired a quite technical sense. ‘Light from light’ denoted the irradiation surrounding a light source. It is in this latter sense that light could justify both the active notion of an emanation from the source and the passive notion of an image of the source (Wis. 7:25–6) or a characteristic imprint, viz. quality, of it (Heb. 1:3).

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Epitome doctrinae Platonicae sive Didaskalikos

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Urkunde

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De Genesi contra Manichaeos De Genesi ad Litteram Retractationes

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Basil of Caesarea Ad adulescentes

Oratio ad adolescentes de legendis antiquorum seu gentilium libris

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Homiliae in hexaemeron

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Homilia in illud: Attende tibi ipsi

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Homilia quod deus non est auctor malorum

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Cicero DND

De natura deorum

Plasberg, Otto, and Wilhelm Ax (eds), M. Tulli Ciceronis scripta quae manserunt omnia, Fasc. 45: De natura deorum, ed. stereotypa editionis secundae (1933) (Berlin: De Gruyter, 2014) [= Bibliotheca Teubneriana 1221]. Orat. De oratore Kumaniecki, Kazimierz F. (ed.), M. Tulli Ciceronis scripta quae manserunt omnia, Fasc. 3: De oratore (Berlin: in aedibvs B.G. Tevbneri, 1969; rev. ed. 1995) [= Bibliotheca scriptorum Graecorum et Romanorum Teubneriana 1171]. Wilkins, A. S. (ed.), M. Tulli Ciceronis Rhetorica, Vol. 1: De Oratore Libri Tres (Oxonii: e typographical Clarendoniano, 1902; repr. 1961) [= Oxford Classical Texts].



201

Clement Ecl. Eclogae propheticae Strom. Stromateis Stählin, Otto, Ludwig Früchtel, and Ursula Treu (eds), Clemens Alexandrinus, Vol. 2: Stromata Buch I–VI, 4th ed. (Berlin: Akademie Verlag, 1985) [= Die griechischen christlichen Schriftsteller der ersten Jahrhunderte 52]. Stählin, Otto, Ludwig Früchtel, and Ursula Treu (eds), Clemens Alexandrinus, Vol. 3: Stromata Buch VII und VIII: Excerpta ex Theodoto—Eclogae propheticae quis dives salvetur—Fragmente, 2nd ed. (Berlin: Akademie Verlag, 1970) [= Die griechischen christlichen Schriftsteller der ersten Jahrhunderte 17].

Cleomides Caelest.

Caelestia (Meteora)

Todd, Robert (ed.), Cleomedis Caelestia (Meteora) (Leipzig: Teubner, 1990) [= Bibliotheca scriptorum Graecorum et Romanorum Teubneriana].

Didymus Com. Gen. Commentary on Genesis Nautin, Pierre, and Louis Doutreleau (eds), Didyme l’Aveugle, Sur la Genèse: Texte inédit d’après un papyrus de Toura (Introduction, édition, traduction et notes), 2 vols (Paris: Éditions du Cerf, 1976–8) [= Sources Chrétiennes 233 and 244].

Diodore of Tarsus See Catenae (Collectio Coisliniana)

Diogenes Laertius Vitae

Vitae Philosophorum

Dorandi, Tiziano (ed.), Diogenes Laertius: Lives of Eminent Philosophers (Cambridge: Cambridge University Press, 2013) [= Cambridge Classical Texts and Commentaries 50]. Marcovich, Miroslav, and Hans Gärtner (eds), Diogenes Laertius: Vitae Philosophorum, 3 vols, Vol. I: Libri I–X; Vol. II: Excerpta Byzantina; Vol. III: Indices (Stuttgardiae et Lipsiae: in aedibus B.G. Teubneri, 1999–2002) [= Bibliotheca scriptorum Graecorum et Romanorum Teubneriana].

Empedocles Wright, M. R. (ed.), Empedocles: The Extant Fragments; Edited, with an Introduction, Commentary and Concordance (New Haven, CT: Yale University Press, 1981).

Eriugena Periphyseon Periphyseon (De Divisione Naturae) Jeauneau, Édouard (ed.), Iohannis Scotti seu Eriugenae Periphyseon, 5 vols (Turnholti: Typographi Brepols Editores Pontificii, 1996–2003) [= Corpus Christianorum, Continuatio Mediaevalis 161–5]. Sheldon-Williams, I. P., et al. (eds), Iohannis Scotti Eriugenae Periphyseon (De Divisione Naturae), 4 vols (Dublin: Dublin Institute for Advanced Studies, 1968–95) [= Scriptores Latini Hiberniae 7, 9, 11, 13].

202



Euclid Optics

Optica

Heiberg, J. L. (ed.), Euclidis opera omnia, Vol. 7: Euclidis Optica, Opticorum recensio Theonis, Catoptrica, cum scholiis antiquis (Leipsiae: in aedibus B.G. Teubneri, 1895).

Eusebius DE

Demonstratio evangelica

Heikel, Ivar A. (ed.), Die demonstratio evangelica (Leipzig: Hinrich, 1913) [= Die Griechischen Christlichen Schriftsteller der ersten Jahrhunderte, Eusebius Werke 6]. PE

Praeparatio evangelica

Mars, Karl, and Édouard des Places (eds), Die praeparatio evangelica, 2 vols, 2nd ed. (Berlin: Akademie Verlag, 1982–3) [= Die Griechischen Christlichen Schriftsteller der ersten Jahrhunderte, Eusebius Werke 8/1 and 2].

Galen Com. Tim.

Commentary on the Timaeus

Larrain, Carlos J. (ed.), Galens Kommentar zu Platons Timaios (Stuttgart: Teubner, 1992). PHP

De placitis Hippocratis et Platonis

Müller, Iwan von (ed.), De placitis Hippocratis et Platonis libri novem (Lipsiae: in aedibus B. G. Teubneri, 1874). Tremor. De tremore Agnelli, Sara (ed.), Galen On Tremor, Rigor, Palpitation and Spasm: A Critical Edition (Diss. University of Florida, 2016). Kühn, Karl Gottlob (ed.), Galeni de tremore, palpitatione, convulsione et rigore liber, in (Leipsiae: Prostat in officina libraria Car. Cnoblochii, 1824), 584–642. [= Claudii Galeni Opera Omnia VII]. Usu

De usu partium

Helmreich, Georg (ed.), Γαληνοῦ Περὶ χρείας μορίων IZ’ = Galeni De usu partium libri XVII (Lipsiae: in aedibus B.G. Teubneri, 1907).

Geminus Schöne, Richard (ed.), Damianos Schrift über Optik mit Auszügen aus Geminos: Griechisch und Deutsch (Berlin: Reichsdruckerei, 1897).

Gregory of Nazianzus Orat.

Orationes

Bernardi, Jean (ed.), Grégoire de Nazianze, Discours 42–43: Introduction, texte critique, traduction et notes (Paris: Éditions du Cerf, 1992) [= Sources Chrétiennes 384]. Galay, Paul, and Maurice Jourjon (eds), Grégoire de Nazianze, Discours 27–31: Introduction, texte critique, traduction et notes (Paris: Éditions du Cerf, 1978) [= Sources Chrétiennes 250]. Moreschini, Claudio, and Paul Gallay (tr.), Grégoire de Nazianze, Discours 38–41: Introduction, texte critique et notes (Paris: Éditions du Cerf, 1990) [= Sources Chrétiennes 358].



203

Gregory of Nyssa Ad Abl. Adv. Maced. Adv. Ar. et Sab.* An. et res. Apology C.Eun. In Hex. Infant. Ref. Eun. Trid. spat. Virg. Vit. Mos.

Ad Ablabium, Quod non sint tres dei [GNO 3/1] Adversus Macedonianos, De spiritu sancto [GNO 3/1] Adversus Arium et Sabellium [GNO 3/1] De anima et resurrectione [GNO 3/3] Apologia in Hexaemeron (= In Hex.) [GNO 4/1] Contra Eunomium [GNO 1–2] Apologia in Hexaemeron (= Apology) [GNO 4/1] De infantibus praematura abreptis [GNO 3/2] Refutatio Confessionis Eunomii [GNO 2/2] De tridui inter mortem et resurrectionem domini nostri Iesu Christi spatio, vulgo in Christi Resurrectionem oratio I [GNO 9/1] De virginitate [GNO 8/1] De vita Mosis [GNO 7/1]

Jaeger, Wernerus, et al., Gregorii Nyseni Opera, 10 vols and supplement (Leiden: Brill, 1960–2014). Creat. hom. De creatione hominis† (see Basil) Hom. opif. De hominis opificio Forbes, G. H., Sancti Gregorii Episcopi: De hominis conditione, in Sancti patris nostri Gregorii Nysseni Basilii Magni fratris quae supersunt omnia, Vol. 1, Fasc. 1–2 (E typographeo de Pitsligo, 1855), 96–319. Letter 26† (see Gregory Thaumaturgus, Ad Philagrium) Letter 35* (see also Basil, Letter 38) Silvas, Anna (ed.), Gregory of Nyssa: The Letters—Introduction, Translation and Commentary (Leiden: Brill, 2007), 247–59.

Gregory Thaumaturgus (?) Ad Philagrium

(vel Ad Evagrium)

Migne, J. P. (ed.), Epistola 26: Ad Evagrium monachum, de Divinitate, in S.P.N. Gregorii Episcopi Nysseni Opera quae reperiri potuerunt omnia, Vol. 4 (Parisiis: ex typis Migne, 1863), 1101–108 [= Patrologia Graeca 46]. Slusser, Michael, To Philagrius [Evagrius], on Consubstantiality, in St Gregory Thaumaturgus: Life and Works (Washington, DC: The Catholic University of America Press, 1998), 174–8 [= Fathers of the Church 98].

Heron Catoptrica

(vel Ptolemei De speculis)

Jones, Alexander, ‘Pseudo-Ptolemy De Speculis’, Sciamus (2001), 145–86. Schmidt, Guilelmus, [Claudii Ptolemei] De speculis, in L. Nix and W. Schmidt (eds), Heronis Alexandrini opera quae supersunt omnia, Vol. II, Fasc. 1: Mechanica et catoptrica, accedunt quaedam excerpta (Lipsiae: in aedibus B.G. Teubneri, 1900), 301–99.

Hesiod Works

Opera et dies (Works and Days)

Solmsen, Friedrich (ed.), Hesiodi Theogonia, Opera et Dies, Scutum, 3rd ed. (Oxford: Clarendon Press, 1990) [= Oxford Classical Texts].

204



Iamblichus De mysteriis Des Places, Édouard (ed. and tr.), Jamblique Les Mystères d’Égypte: Texte établi et traduit (Paris: Belles Lettres, 1966) [= Collection Budé 174]. Saffrey, Henri Dominique, and Alain-Philippe Segonds, Jamblique Réponse à Porphyre (De mysteriis): Texte établi et traduit (Paris: Belles Lettres, 2013) [= Collection Budé 496].

Ibycus Page, D. L., Poetae melici Graeci (Oxford: Clarendon Press, 1962). Bergk, Theodorus (ed.), Poetae Lyrici Graeci, 3 vols, 4th ed. (Lipsiae: in aedibus B. G. Teubneri, 1878–82).

John Chrysostom Hom. Gen.

Homiliae in Genesim

Migne, J. P. (ed.), Homiliae in Genesim, in S.P.N. Joannis Chrysstomi Opera omnia quae exstant, Vol. 4.1–2 (Parisiis: ex typis Migne, 1862), 21–580 [= Patrologia Graeca 53–4]. Serm. Gen. Sermones in Genesim Brottier, Laurence (ed.), Jean Chrysostome, Sermons sur la Genèse: Introduction, texte critique, traduction et notes (Paris: Éditions du Cerf, 1998) [= Sources Chrétiennes 433]. Migne, J. P. (ed.), Sermones IX in Genesim, in S.P.N. Joannis Chrysstomi Opera omnia quae exstant, Vol. 4.2 (Parisiis: ex typis Migne, 1862), 581–630 [= Patrologia Graeca 54].

John Damascene De fide

De fide orthodoxa

Kotter, Bonifatius (ed.), Die Schriften des Johannes von Damaskos, Vol. 2: Expositio Fidei (Berlin: De Gruyter, 1973) [= Patristische Texte und Studien 12].

Josephus Bryennius Orat.

Orationes

Boulgares, Eugenios (ed.), Orations, in Ἰωσὴφ μοναχοῦ τοῦ Βρυεννίου τὰ Εὐρεθέντα, Vol. 1 (Leipzig, 1768; repr. 1991).

Julian Contra Galileos Bouffartigue, Jean, Marie-Odile Boulnois, and Pierre Castan (eds), Cyrille d’Alexandrie, Contre Julien II (Paris: Éditions du Cerf, 2016) [= Sources Chrétiennes 582]. Burguière, Paul, and Pierre Évieux (eds), Cyrille d’Alexandrie, Contre Julien I: Introduction, texte critique, traduction et notes (Paris: Éditions du Cerf, 1985) [= Sources Chrétiennes 322]. Kinzig, Wolfram, and Thomas Brüggemann (eds), Kyrill von Alexandrien I Gegen Julian, Teil 2: Buch 6–10 und Fragmente (Berlin: De Gruyter, 2017) [= Die Griechischen Christlichen Schriftsteller der ersten Jahrhunderte, Neue Folge 21]. Masaracchia, Emanuela (ed.), Giuliano Imperatore Contra Galileos (Rome: Edizioni dell’ Ateneo, 1990). Riedweg, Christoph, et al. (ed.), Kyrill von Alexandrien I Gegen Julian, Teil 1: Buch 1–5 (Berlin: De Gruyter, 2016) [= Die Griechischen Christlichen Schriftsteller der ersten Jahrhunderte, Neue Folge 20].



205

Justin Martyr [pseudo-] Ad gentiles

Quaestiones Christianorum ad gentiles

Otto, J. C. T. (ed.), Quaestiones Christianorum ad gentiles, in Corpus apologetarum Christianorum saeculi secundi, Vol. 5, 3rd ed. (Jena: Mauke, 1881; repr. Wiesbaden: Martin Sändig, 1969), 246–326.

Libanius Orat.

Orationes

Foerster, Richard (ed.), Libanii Opera, 12 vols (Leipsiae: in aedibus B.G. Teubneri, 1903–27) [= Bibliotheca scriptorum Graecorum et Romanorum Teubneriana].

Marcus Aurelius Meditat.

Meditationes

Farquharson, A. S. L. (ed.), The Meditations of the Emperor Marcus Aurelius, Vol. 1: Text and Translation (Oxford: Oxford University Press, 1944).

Nemesius DNH

De natura hominis

Morani, Moreno (ed.), Nemesii Emeseni De natura hominis (Leipzig: Teubner, 1987) [= Bibliotheca scriptorum Graecorum et Romanorum Teubneriana].

Nikephorus (?) Vita Andreae

Vita sancti Andreae sali

Rydén, Lennart (ed.), Vita sancti Andreae Sali, in The Life of St. Andrew the Fool: Text, Translation and Notes, Vol. 2 (Uppsala: Acta Universitatis Upsaliensis, 1995) [= Studia Byzantina Upsaliensia 4].

Origen Com. Gen.

In Genesim (Commentary on Genesis)

Metzler, Karin (ed.), Die Kommentierung des Buches Genesis (Berlin/Freiburg: De Gruyter/ Herder, 2010) [= Origenes: Werke mit deutscher Übersetzung 1/1]. Commentary on Hebrews In epistulam ad Hebreos Amacker, René, and Éric Junod (eds), Pamphile—Eusèbe de Césarée, Apologie pour Origène, suivi de Rufin d’Aquilée, Sur la falsification des livres d’Origène: Texte critique, traduction et notes, Vol. 1 (Paris: Éditions du Cerf, 2002) [= Sources Chrétiennes 464]. Commentary on the Song of Songs In Canticum Canticorum Baehrens, W. A. (ed.), Origenes Werke: Homilien zu Samuel I, zum Hohelied und zu den Propheten, Kommentar zum Hohelied in Rufins und Hieronymus’ Übersetzungen (Leipzig: Hinrich, 1925) [= Die Griechischen Christlichen Schriftsteller der ersten Jahrhunderte, Origenes 8]. Brésard, Luc, Henri Crouzel, and Marcel Borret (eds), Origène, Commentaire sur le Cantique des Cantiques, texte de la version latine de Rufin, introduction, traduction et notes, 2 vols (Paris: Éditions du Cerf, 1991–2) [= Sources Chrétiennes 375 and 376]. Fürst, Alfons, and Holger Strutwolf (eds), Der Kommentar zum Hohelied (Berlin: De Gruyter, 2016) [= Origenes: Werke mit deutscher Übersetzung 9/1].

206

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CC

Contra Celsum

Koetschau, Paul, Origenes Werke: Die Schrift vom Martyrium; Buch I–IV Gegen (Leipsig: Hinrich, 1899) [= Die Griechischen Christlichen Schriftsteller der Jahrhunderte, Origenes 1]. Koetschau, Paul, Origenes Werke: Buch V–VIII Gegen Celsus; Die Schrift vom (Leipsig: Hinrich, 1899) [= Die Griechischen Christlichen Schriftsteller der Jahrhunderte, Origenes 2]. Marcovich, M. (ed.), Origenes: Contra Celsum Libri VIII (Leiden: Brill, [= Supplements to Vigiliae Christianae 54]. DP

Celsus ersten Gebet ersten 2001)

De principiis

Behr, John (ed. and tr.), Origen: On First Principles, 2 vols (Oxford: Oxford University Press, 2017) [= Oxford Early Christian Texts]. Koetschau, Paul, Origenes Werke: De Principiis (Περὶ Ἀρχῶν) (Leipsig: Hinrich, 1913) [= Die Griechischen Christlichen Schriftsteller der ersten Jahrhunderte, Origenes 5]. Hom. Gen.

Homiliae in Genesim (Homilies on Genesis)

Baehrens, W. A. (ed.), Origenes Werke: Homilien zum Hexateuch in Rufins Übersetzung, Teil 1: Die Homilien zu Genesis, Exodus und Leviticus (Leipsig: Hinrich, 1920) [= Die Griechischen Christlichen Schriftsteller der ersten Jahrhunderte, Origenes 6]. Habermehl, Peter (ed.), Die Homilien zum Buch Genesis (Berlin: De Gruyter, 2011) [= Origenes Werke mit deutscher Übersetzung 1.2]. Habermehl, Peter (ed.), Origenes VI: Homilien zum Hexateuch in Rufins Übersetzung, Teil 1: Die Homilien zu Genesis (Homiliae in Genesin), 2nd ed. (Berlin: De Gruyter, 2012) [= Die Griechischen Christlichen Schriftsteller der ersten Jahrhunderte, Neue Folge 17]. Hom. Ezek.

Homiliae in Ezechielem

Baehrens, W. A. (ed.), Origenes Werke: Homilien zu Samuel I, zum Hohelied und zu den Propheten, Kommentar zum Hohelied in Rufins und Hieronymus’ Übersetzungen (Leipsig: Hinrich, 1925) [= Die Griechischen Christlichen Schriftsteller der ersten Jahrhunderte, Origenes 8]. Hom. Jer.

Homiliae in Ieremiam

Fürst, Alfons, and Horacio E. Lona (eds), Die Homilien zum Buch Jeremia (Berlin: De Gruyter, 2018) [= Origenes Werke mit deutscher Übersetzung 11]. Klostermann, Erich, and Pierre Nautin (eds), Origenes Werke: Jeremiahomilien, Klageliederkommentar, Erklärung der Samuel- und Königsbücher, 2nd ed. (Berlin: Akademie Verlag, 1983) [= Die Griechischen Christlichen Schriftsteller der ersten Jahrhunderte, Origenes 3]. Hom. Ps.

Homiliae in Psalmos (Homilies on Psalms)

Perrone, Lorenzo, et. al. (eds), Origenes Werke 13: Die neuen Psalmenhomilien—Eine kritische Edition des Codex Monacensis Graecus 314 (Berlin: De Gruyter, 2015) [= Die Griechischen Christlichen Schriftsteller der ersten Jahrhunderte, Neue Folge 19].

Philo of Alexandria Abr Aet. Cher. Conf.

De Abrahamo De aeternitate mundi De Cherubim De confusione linguarum

 Congr. Decal. Deus Gig. Heres Migr. Opif. Plant. QG Somn. Spec.

207

De congressu quaerendae eruditionis gratia De Decalogo Quod Deus sit immutabilis De Gigantibus Quis rerum divinarum heres De migratione Abrahami De opificio mundi De plantatione Quaestiones et Solutiones in Genesim De somniis De specialibus legibus

Cohn, Leopold, Paul Wendland, et al. (eds), Philonis Alexandrini Opera Quae Supersunt, Editio Maior, 7 vols (Berlin: Reimer, 1896–1930; repr. De Gruyter, 1962–3).

Plato Crat. Cratylus Epinomis† Laws Leges Meno Phaedo Phdr. Phaedrus Rep. Respublica (Republic) Statesman Politicus Theaet. Theaetetus Tim. Timaeus Duke, E. A., et al. (eds), Platonis Opera, Tomus I, Tetralogias I–II Continens (Oxford: Clarendon Press, 1995). Burnet, Ioannes (ed.), Platonis Opera, 5 vols (Oxford: Clarendon Press, 1900–7) [= Oxford Classical Texts].

Pliny Nat. Hist.

Naturalis historia

Jan, Ludwig von, and Karl Mayhoff (eds), C. Plini Secundi Naturalis historiae libri XXXVI, 6 vols (Lipsiae: in aedibus B.G. Teubneri, 1875–1906) [= Bibliotheca scriptorum Graecorum et Romanorum Teubneriana].

Plotinus Enn.

Enneades

Henry, Paul, and Hans-Rudolf Schwyzer (eds), Plotini opera, Editio minor, 3 vols (Oxonii: e typographeo Clarendoniano, 1964–82).

Plutarch Curios. De curiositate Def. or. De defectu oraculorum Facie De facie in orbe lunae Is. et Os. De Iside et Osiride Prim. frig. De primo frigido Pyth. or. De Pythiae oraculis Quaest. conv. Quaestiones convivales

208



Pohlenz, Max, et al. (eds), Plutarchi Moralia (Leipzig: in aedibus B.G. Teubneri, 1925–78) [= Bibliotheca scriptorum Graecorum et Romanorum Teubneriana].

Plutarch [pseudo-] Homer.

De Homero

Hillgruber, Michael (ed.), Die pseudoplutarchische Schrift De Homero, Teil 1: Einleitung und Kommentar zu den Kapiteln 1–73 (Leipzig: Teubner, 1994) [= Beiträge zur Altertumskunde 57]. Kindstrand, Jan Fredrik (ed.), [Plutarchi] De Homero (Leipzig: Teubner, 1990) [= Bibliotheca scriptorum Graecorum et Romanorum Teubneriana].

Porphyry Gaur.

Ad Gaurum

Kalbfleisch, Karl (ed.), ‘Die neuplatonische, fälschilch dem Galen zugeschriebene Schrift Πρὸς Γαῦρον περὶ τοῦ πῶς ἐμψυχοῦνται τὰ ἔμβρυα: Aus der Pariser Handschrift zum ersten Male herausgegeben’, in Abhandlungen der königlichen Akademie der Wissenschaften zu Berlin; Philosophische-historische Klasse, Abhandlung 1 (Berlin: Reimer, 1895), 1–80. Contra Christianos Ramos Jurado, Enrique A., et al. (eds), Porfirio de Tiro, Contra los Cristianos: Recopilación de fragmentos, tradución, introdución y notas (Cadiz: Publicaciones de la Universidad de Cádiz, 2006). von Harnack, Adolf (ed.), Porphyrius, Gegen die Christen, 15 Bücher: Zeugnisse, Fragmente und Referate, in Abhandlungen der königlichen preussischen Akademie der Wissenschaft 1916; Philosophisch–historische Klasse 1 (Berlin: Reimer, 1916). In Cat.

In Categorias

Busse, Adolf (ed.), Porphyrii in Aristotelis categorias expositio per interrogationem et responsionem, in Porphyrii isagoge et in Aristotelis categorias commentarium (Berolini: Typis et impensis Georgii Reimer, 1887), 53–142 [= Commentaria in Aristotelem Graeca 4.1]. Sentent.

Sententiae

Lamberz, Erich (ed.), Porphyrii Sententiae ad intelligibilia ducentes (Leipzig: Teubner, 1975). Muscolino, Giuseppe (ed.), Porfirio Contro I cristiani: Nella raccolta di Adolf von Harnack con tutti i nuovi frammenti in appendice (Milan: Bompiani, 2009).

Posidonius Commentary on the Timaeus* Edelstein, L., and I. G. Kidd (eds), Posidonius, Vol. I: The Fragments, 2nd ed. (Cambridge: Cambridge University Press, 1989) [= Cambridge Classical Texts and Commentaries 13]

Ptolemy De speculis (see Heron) Harmonics Harmonica Düring, Ingemar (ed.), Die Harmonielehre des Klaudios Ptolemaios (Göteborg: Elanders boktr. aktiebolag, 1930; reprint: New York, NY: Garland Publishing, 1980).



209

Solomon, Jon, Ptolemy Harmonics: Translation and Commentary (Leiden: Brill, 2000) [= Mnemosyne, Supplements 203]. Optics

Optica

Lejeune, Albert (ed.), L’Optique de Claude Ptolémée dans la version latine d’après l’arabe de l’émir Eugène de Sicile: Édition critique et exégétique augmentée d’une traduction française et de compléments (Leiden: Brill, 1989).

Priscian Answers to Chosroes

Solutiones ad Chosroen

Bywater, Ingram (ed.), Prisciani Lydi Solutiones ad Chosroen, in Supplementum Aristotelicum, Vol. 1, Pars 2: Prisciani Lydi quae extant (Berolini: Typis et impressis Georgii Reimeri, 1886), 40–104. Huby, Pamela, Sten Ebbesen, David Langslow, Donald Russell, Carlos Steel, and Malcolm Wilson (ed. and tr.), Priscian: Answers to King Khosroes of Persia (London: Bloomsbury, 2014) [Ancient Commentators on Aristotle].

Proclus Elements

Institutio theologica (Elements of Theology)

Boese, H. (ed.), Proclus, Elementatio Theologica, translata a Guillielmo de Moerbecca (Louvain: Louvain University Press, 1987) [= Ancient and Mediaeval Philosophy—De Wulf-Mansion Centre, Series 1.5] Dodds, E. R. (ed.), The Elements of Theology: A Revised Text with Translation, Introduction, and Commentary, 2nd ed. (Oxford: Clarendon Press, 1963). Onnasch, E. O., and B. Schomakers (eds), Proklos Theologische Grundlegung: GriechischDeutsch; Übersetzt und mit einer Einleitung sowie einem durchgängigen erläuternden Kommentar versehen (Hamburg: Felix Meiner Verlag, 2015). [= Philosophische Bibliothek 562]. In Tim.

In Platonis Timaeum

Diehl, Ernestus (ed.), Procli Diadochi in Platonis Timaeum commentaria (Lipsiae: in aedibus B.G. Teubneri, 1903–6) [= Bibliotheca scriptorum Graecorum et Romanorum Teubneriana].

Scholia anonyma In Genesim

Schol. in Basil. Orat. περὶ γενέσεως

Cramer, J. A. (ed.), Anecdota Graeca e codd. Manuscriptis bibliothecarum Oxoniensium, Vol. 3 (Oxonii: e typographeo academico, 1836) [Cod. Barocc. 85 fol. 118].

Seneca NQ

Naturales quaestiones

Hine, Harry M. (ed.), Lucius Annaeus Seneca Opera: Naturalium quaestionum libri (Lipsiae: in aedibus B.G. Teubneri, 1996) [= Bibliotheca scriptorum Graecorum et Romanorum Teubneriana 182].

Severian of Gabala Cosmog.

In cosmogoniam

Migne, J. P. (ed.), Severiani Gabalorum Episcopi In mundi creationem, in S.P.N. Joannis Chrysstomi Opera omnia quae exstant, Vol. 6 (Parisiis: ex typis Migne, 1862), 429–500 [= Patrologia Graeca 56].

210

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Simplicius In Cael.

In Aristotelis de caelo

Heiberg, Johann Ludwig (ed.), Simplicii in Aristotelis de caelo commentaria (Berolini: Typis et impensis Georgii Reimeri, 1894) [= Commentaria in Aristotelem Graeca 7]. In Cat.

In Aristotelis categorias

Kalbfleisch, Karl, Simplicii in Aristotelis categorias commentarium (Berolini: Typis et impensis Georgii Reimeri, 1907) [= Commentaria in Aristotelem Graeca 8]. In Phys.

In Aristotelis physicorum

Diels, Hermannus (ed.), Simplicii in Aristotelis physicorum libros quattuor priores commentaria (Berolini: Typis et impensis Georgii Reimeri, 1882) [= Commentaria in Aristotelem Graeca 9].

Socrates Scholasticus Hist. Eccles.

Historia ecclesiastica

Hansen, Günther Christian (ed.), and Manja Širinjan, Sokrates Kirchengeschichte (Berlin: Akademie Verlag, 1995) [= Die griechischen christlichen Schriftsteller der ersten Jahrhunderte, Neue Folge 1]

Stobaeus Ecl.

Eclogae physicae

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Tertullian Apol.

Apologeticus

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Theodoret Quest. in Gen.

Questiones in Genesim

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Theophilus Autol.

Ad Autolycum

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Theophrastus De igne Coutant, Victor (ed.), De igne: A Post-Aristotelian View of the Nature of Fire (Assen: Van Gorcum, 1971).

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De sensu

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Index of Passages Notes: The index includes all passages mentioned in the text and key passages discussed in the footnotes. Tables are indicated by an italic “t”, following the page number. For the benefit of digital users, indexed terms that span two pages (e.g., 52–53) may, on occasion, appear on only one of those pages.

The Bible Genesis 1 15–16, 19–21, 27–8, 34–5, 47n.106, 73n.34, 79n.64, 80n.66, 148t, 156–7, 156n.113, 159–60, 164 1:1 17, 79–81, 84–8, 84n.84, 87n.98, 90n.111, 94–6 1:1–2 71–2, 87n.96, 106n.155 1:1–5 18, 66–7 1:2 164–5 1:2a 79–81, 84–8, 84n.84, 85n.92, 87n.98, 123, 132–3 1:2b 35n.67 1:3 79–81, 80n.67, 104–6, 109–12 1:3a, 3b, 5b 18n.2 1:3–4 98 1:3-4a 189 1:4b-5 189 1:3–5 17–18, 21–2, 53–4, 106n.155, 150–2 1:4 17–20, 27, 42–3, 187 1:7 79–81 1:8 79–81 1:9–10 87n.98 1:14 29–30, 33, 38–9, 42–3, 47–8, 110–12 1:14–15 38–9 1:14–19 38–9, 53–4, 152 1:15,17 38–9 1:16–19 191–2 1:26 30, 172–3 1:26–27 156–7 1:26–28 53–4 1:27 157n.116 1:28 40n.80 1:28–30 38–9 2 156–7 2:4 66–7 2:7 156–7 Exodus 3:2 120

Deuteronomy 4:9 44–5 4:24 120, 122n.39 9:3 120 15:9 44–5 Job 38:7 17, 30–1, 31n.51 Psalms 18:2 31n.51 73:16 153–4 104:4 120 Wisdom 7:25 191–3 7:25–26 196 7:26 191–5 11:20 74n.38 Jeremiah 5:14 120 Matthew 3:9 68 5:14 170 17:2 187–8 28:3 187–8 Mark 9:3 187–8 16:5 187–8 Luke 3:8 68 9:29 187–8 24:4 187–8 John 1 47n.106 1:1 90n.111, 172–3 1:1–18 47n.106 20:12 187–8 Romans 12:11 120

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1 Corinthians 15:41 191–2 2 Corinthians 12:2 79–81 Ephesians 3:10 35n.67 3:14–21 35n.67 Colossians 2:19 36n.68 Hebrews 1:3 191–6 1:7 120 1:14 33n.56 12:29 120 1 John 1:5 172–3

Ancient and Premodern Works Anonymous Prayer of Joseph 29n.42 Alexander of Aphrodisias De anima 52n.119, 140n.88 In De sensu 166–7 Mantissa 140n.88, 166–7 Aristotle De anima 57–8, 160–2, 166–7, 171, 178–9, 189 De caelo 178–9 De generatione et corruptione 113–14 Metaphysica 86nn.94–95, 179, 181–2 Meteorologica 179 Physica 17–18, 166–7, 179, 181–2 De sensu 161–2, 166–7, 179, 189 Arius Thalia 194–5 Athanasius Orationes contra Arianos 194–5 De synodis 194–5 Augustine De Genesi ad litteram 79–81, 80n.67 Basil of Caesarea Homiliae in Hexaemeron 11–12, 20, 35n.65, 42–3, 47–8, 64–5, 78, 108–10, 134–6 Homily 319 44–6 Calcidius Commentary on the Timaeus 32–3, 52, 71–2 On Matter (De silva) 71–2 Celsus True Doctrine 67

Damianos Optica 138–9 Didymus the Blind Commentary on Genesis 41–2 Dionysius the Areopagite (pseudo-) Mystical Theology 7–8 Eriugena, John Scotus Periphyseon 107, 171–2 Eusebius of Caesarea Praeparatio Evangelica 71–2 Galen On the Usefulness of Parts 67–8 Gregory Nazianzen Orationes 148, 159 Gregory of Nyssa De anima et resurrectione 129–30, 129n.50 Apologia in Hexaemeron 64–5, 75–96, 100–1, 105–6, 108–10, 112–14, 118–19, 124–7, 129–31, 136, 138–9, 150–2, 189–90 De creatione hominis 44–5 De hominis opificio 44–5, 76–8, 127–8 Grosseteste, Robert De luce 1 Hesychius Lexicon 192–3 John of Damascus De fide orthodoxa 61 Origen Contra Celsum 71–2 Homiliae in Genesim 41 Homiliae in Psalmos 110–12, 153–4 In Genesim 29–30, 71–2, 153–4 In Canticum Canticorum 162–4 Philocalia 153 De principiis 71–2, 119–20, 123, 153–4 Philo of Alexandria De congressu quaerendae eruditionis gratia 162–4 De opificio mundi 15–16, 39, 155–7, 193–4 Plato Cratylus 31n.51 Phaedo 75–6 Republic 3, 5–7, 9–10, 31n.51, 47–8, 51–3, 57–8, 168, 171 Statesman 33n.56

   Timaeus/Timaean 27–8, 32–6, 39, 41n.83, 45n.99, 47–53, 55–7, 68–73, 75–8, 79n.64, 81n.68, 83n.81, 84–8, 90n.111, 93n.119, 94–7, 104nn.152–153, 115–18, 132–6, 137n.78, 145, 148t, 155, 159–62, 164–6, 171, 173–9, 183–9 Plotinus Enneads 52 Posidonius Commentary on the Timaeus 77–8 Proclus Commentary on the Timaeus 35–6, 116–18 Ptolemy Optics 178–80 Theodore of Mopsuestia Ad Genesin 1:1 (from the Catenae) 17, 31n.50

Theodoret of Cyprus The Questions on the Octateuch 30–1 Questiones in Genesis 30–1 Theophrastus De igne 96–7, 120, 123–4 Witelo/Adam Pulchrae Mulieris Liber de intelligentis 2n.7, 3

Modern Works Lindberg, David Theories of Vision from AlKindi to Kepler 22 Lloyd, G.E.R Polarity and Analogy 5–7 Ronchi, Vasco Storia della luce 22 Smith, A. Mark From Sight to Light 175–6

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Index of Persons and Names Notes: The index includes the names mentioned in the text and the key names discussed in the footnotes. Cognates, including schools of thought, are mentioned with the original name (e.g. ‘Aristotelian’ and ‘Peripatetic’ with ‘Aristotle’; ‘Plotinian’ with ‘Plotinus’; but ‘Middle Platonism’ and ‘Neoplatonism’ with ‘Plato’). Cognates and schools named after cities (e.g. ‘Alexandrian’; ‘Antiochene’) are mentioned with the cities in the subject index. For reasons of consistency, ‘Stoic(s)’ and ‘Stoicism’ are included in the present index. Tables are indicated by an italic “t”, following the page number. For the benefit of digital users, indexed terms that span two pages (e.g., 52–53) may, on occasion, appear on only one of those pages. Alcinous 51 Alexander of Aphrodisias 52n.119, 85n.92, 104n.153, 166–7 Alexandre, Monique 79n.64 Alhacen 27n.33 Ambrose 31n.51, 37–8, 37n.71, 46, 119n.27, 137n.78, 146n.98 Ammonius Saccas 29n.41 Anaxagoras/Anaxagorean 39–40, 93n.119 Anaximenes 115n.19 Apuleius 33n.56 Aristobulus 73n.34 Aristotle/Aristotelian/Peripatetic 17–18, 39–40, 42–3, 52n.119, 57–8, 69n.17, 83n.77, 84–8, 85n.92, 86n.94, 92–4, 92–3nn.117–119, 96–7, 97n.131, 101n.141, 104n.153, 113–16, 114n.15, 116n.21, 120–2, 121nn.29,32, 122n.35, 124, 132n.60, 133n.62, 134n.68, 136n.73, 137n.78, 140n.88, 141n.89, 142n.90, 144n.95, 145, 148–9t, 160–2, 166–7, 169–71, 178–83, 184n.1, 187–9, 193–5 Arius/Arian 194–5 Athanasius 146n.98, 148–9t Augustine 3–5, 20–1, 62–4, 79–81, 80nn.66–67, 171–2 Baeumker, Clemens 2–5, 9n.28, 13–14 Barnes, Michel René 11–12, 100n.137, 146n.98 Barth, Karl 62–3 Berryman, Sylvia 54n.122

Basil of Caesarea/Basilian 7–8, 11–12, 19–22, 21n.6, 34–8, 35nn.65,67, 42–8, 52–3, 64–70, 65n.4, 76–81, 76n.43, 78nn.54,62, 80–1nn.66–68, 82n.75, 84–91, 86n.94, 87nn.96,98, 90n.111, 93n.119, 96–7, 100n.137, 101, 102n.144, 104–6, 104n.152, 106n.155, 109–12, 110n.2, 111nn.9,11, 117–19, 117n.23, 119n.27, 122–3, 126–8, 132–9, 134–5nn.68–69,72, 136n.73, 137n.78, 138n.80, 139n.81, 140n.88, 141–4, 141n.89, 147–54, 148–9t, 151nn.101–102, 153n.103, 157–8, 157n.117, 164–6, 168–72, 181–5, 187–92 Behr, John 46n.105, 155n.106 Beierwaltes, Werner 4–5, 9n.28, 13–14, 191–2 Boyancé, Pierre 8–10, 9n.27, 12 Blamont, Jacques 27n.34 Bouteneff, Peter 78–9 Brayford, Susan 18n.2 Brooke, John Hedley 62–4 Bultmann, Rudolph 63–4 Burnet, Thomas 62–3 Calabi, Francesca 32n.52 Calcidius 32–5, 33–4nn.56,57, 39n.77, 52–3, 79n.64, 85n.92, 128 Celsus 65–7, 66n.6, 67–72, 75–6, 75n.42, 76n.43, 79–81, 80n.66, 125n.44, 153 Chrysippus 57, 114–15, 120–2, 121n.34, 124–5 Cicero 96–7 Clark, Stephen 38n.72 Cleanthes 120–2, 121n.34

     Clement of Alexandria 74n.40 Cleomedes 130nn.52,53 Corsini, E. 77–9, 78nn.54,62 Costache, Doru 35n.65, 70n.19, 78–9, 78n.62, 79n.64 Daniélou, Jean 83n.77 DelCogliano, Mark 11–12 DeMarco, David 78n.62 Democritus 187–8 Didymus the Blind 31n.51, 41–2, 106n.155 Diodore of Tarsus 31n.50 Dionysius the Areopagite 3–8, 77n.48, 159–60 Dölger, Franz Joseph 193–4 Drecoll, Volker Henning 12, 21n.6 Edwards, Mark 73n.35 Einstein, Albert 55–7, 56n.133 Empedocles 104n.152, 132–5, 133n.62, 134n.68, 137n.78, 161–2 Endo, Masanobu 47n.106 Epicurus/Epicurean 67–8, 82n.74 Eriugena, John Scotus 77n.48, 159–60 Euclid 24n.16, 54n.122 Eunomius 11–12, 65n.4, 99n.134, 146n.98, 148–9t, 193 Eusebius of Caesarea 194–5 Ferwerda, Rein 4–5 Galen 67–73, 68n.11, 69nn.14,16–17, 73n.34, 75–6, 75n.42, 76n.43, 79–81, 80n.66, 84–9, 98–9, 125n.44, 146n.98, 153 Geminus 128, 137n.77 Gregory Nazianzus 3–4, 146n.98, 148–9t Gregory of Nyssa/Nyssen 7–8, 11–12, 35n.67, 45n.99, 52–3, 58n.137, 62, 64–7, 70–1, 70n.19, 73n.35, 75–106, 75n.42, 76n.43, 78nn.54,62, 79n.64, 80–1nn.66–68, 82n.75, 83nn.77,80, 84n.87, 85n.92, 86n.94, 87nn.97,98, 88nn.101–103, 89nn.106,108, 90n.111, 92n.117, 93n.119, 96n.124, 97nn.130–131, 99n.134, 100n.136, 101n.139, 102n.144, 103n.146, 104n.153, 106n.155, 109–10, 110n.2, 112–19, 117n.23, 119n.27, 123–39, 129–30nn.50–52, 132n.57, 133n.62, 135n.72, 136n.73, 137n.78, 139n.85, 140n.88, 141–2, 146n.98, 150–3, 150n.100, 151n.102, 153n.103, 157–8, 165–6, 168, 171–2, 181–5, 189–94 Gregory Thaumaturgus 117n.23

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Gronau, Karl 45n.99, 77–9, 79n.64 Grosseteste, Robert 1–2, 56n.133 Hahm, David 49–50 Harrison, Peter 40n.80 Henke, Rainer 111n.9 Heraclitus/Heraclitean 91–2, 118–22 Hesiod 33n.56 Hesychius 192–3 Hiebert, Robert 18n.2 Hilary of Poitiers 146n.98 Homer/Homeric 35–6, 35n.65, 116n.21, 134n.68 Hübner, Reinhard 151n.100 Iamblichus 81n.68, 117n.23, 146n.98 Ierodiakonou, Katerina 56n.133, 177–8, 185, 188–9 Irenaeus of Lyons 68n.11 Johansen, Thomas 50–1 John Chrysostom 31–2, 46 John of Damascus 77n.48, 159–60 John the Evangelist, Johannine 47n.106, 148–9t, 156n.113, 172–3 Julian 80n.66, 81n.68, 146n.98, 153 Justin 69n.16 Kalligas 29n.41, 35n.65 Karamanolis, George 181–2 Kepler, Johannes 25–6, 55n.130 Kidd, I.G. 130n.52 Klein, Franz-Norbert 4–5, 8–9 Köckert, Charlotte 56n.132, 71–2, 79n.64, 84n.87, 87n.98 Kugel, James L. 156n.111 Kuhn, Thomas 26, 54, 160–1 Lindberg, David 1–2, 22–7, 175–6 Lloyd, G.E.R 5–7, 5n.15, 85n.92 Long, A. A., and David Sedley 121n.34 Lollar, Joshua 78n.62 Lovejoy 46–7 Ludlow, Morwenna 88n.103 Mackenzie, Iain 56n.133 Macrobius 130n.52 Mani/Manichaeans 2–3, 35n.67 Marcus Aurelius 131n.55, 132n.57 Marinescu, Adrian 12 Marius Victorinus 146n.98 Marmodoro, Anna 100n.137 Martens, Peter 81n.68 Maximus the Confessor 159–60

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    

May, Gerhard 75n.42 McEvoy, James 2 Meyendorff, John 46n.105 Meyer, Hans 151n.100 Mihai, Adrian 35n.65 Newton, Isaac 55–7, 55n.130, 56n.133 Niehoff, Maren 81n.68, 157n.116 Nikiprowetzky, Valentin 59n.143 Nussbaum, Martha 57 O’Brien, Carl Séan 78n.62 Origen/Origenian 7–8, 29–30, 29n.43, 31–3, 35n.67, 38n.72, 41–5, 41n.83, 45n.99, 46–7nn.105–106, 62, 65–7, 66n.6, 70–6, 70n.19, 73nn.31,34,35, 74n.40, 75–6nn.41–43, 78–9, 79n.64, 81n.68, 84–91, 87nn.98,103, 90n.111, 93n.119, 96n.124, 104–5, 110–12, 111nn.9,11, 117n.23, 119–25, 143–4, 146n.98, 148–9t, 153–8, 156n.113, 157n.117, 161–6, 171–3, 181–2, 191–3 Parmenides 104n.152, 134n.68, 172–3 Paul, Apostle/Pauline 35n.67, 79–82, 82n.72, 91–2, 93n.119, 148–9t, 191–2 Pelikan, Jaroslav 56n.132 Peter, Bishop of Sebastia 79–84, 81n.69, 82n.72, 91–2 Petrus 153 Philo of Alexandria/Philonic 4–5, 7–9, 15–16, 32n.52, 33n.56, 34–5, 39–45, 39n.77, 40n.80, 40n.81, 45n.99, 47–8, 52–3, 69n.16, 70–1, 70n.19, 75nn.41–42, 79n.64, 83n.77, 84n.87, 87n.98, 90n.111, 93n.119, 117n.23, 121n.34, 122, 124–5, 135n.69, 146n.98, 148–9t, 153, 154n.104, 155–8, 156n.113, 157nn.116–117, 161–4, 193–4 Philoponus 140n.88 Plato/Platonic/Platonism 1–10, 11n.34, 12, 27–8, 31n.51, 32n.52, 33–8, 35n.65, 39n.77, 42–3, 48n.108, 50–4, 56nn.132–133, 57–8, 60n.145, 65–8, 69n.17, 73n.34, 75–8, 81n.68, 84–8, 97n.126, 102n.145, 104–5, 111n.9, 115, 117–18, 131n.55, 132–5, 137n.78, 139n.85, 140n.88, 141n.89, 142n.90, 143n.91, 145, 146n.98, 147–50, 157–66, 157n.116, 168–82, 184n.1, 188–9, 191–4, 196 Middle Platonic/Platonism 33, 34n.59, 43n.93, 60n.145, 117n.22, 118–19, 148–9n.171 Neoplatonic/Neoplatonism 3–4, 9n.27, 34–5, 117nn.22–23, 118–19, 122–5, 148–9n. Plotinus/Plotinian 4–5, 29n.41, 34n.57, 35n.65, 52–3, 52n.119, 73n.35, 75n.41, 85n.92,

87n.97, 92n.117, 102n.144, 104n.153, 115–22, 116n.21, 117n.23, 121nn.28–29, 122n.39, 182–3, 196 Plutarch 33n.56, 121nn.31,34, 129n.51 Porphyry 81n.68, 98–9, 100n.137, 101n.139, 102n.144, 182–3 Posidonius/Posidonian 45n.99, 51–3, 77–8, 78nn.55,62, 129n.50, 130n.52 Proclus 35–8, 116–18, 117n.23 Protagoras/Protagorean 177–8 Ptolemy 52n.119, 139n.84, 178–80 Pythagoras/Pythagorean 132–3, 132n.60, 133n.62 Radde-Gallwitz, Andrew 11–12, 76n.43, 151n.101 Rasmussen, Adam 73n.35 Risch, Franz Xaver 78n.62, 79n.64, 81–2, 87n.98, 92n.117, 129n.50, 130n.52, 151n.100 Rist, John 117n.23 Ronchi, Vasco 22–4, 26–7 Rousseau, Philip 35n.65 Rowett, Catherine 83n.81 Runia, David 45n.99, 47–8, 48n.108, 52–3, 155–6nn.111–112, 157n.115 Savage, John 37n.71 Scott, Alan 35n.67 Sedley, David 39–40, 40n.80, 68, 73n.34 Severian of Gabala 30–2, 31nn.50–51, 117n.23, 169–70, 172–3 Simon, Gérard 24–7, 27n.34 Sinai 9–10, 82–4 Smith, A. Mark 25–7, 27nn.33–34, 52n.119, 54, 55n.130, 56n.133, 129n.51, 175–80 From Sight to Light, 175–6 Socrates (the philosopher) 22–3, 39–40, 75–6 Socrates Scholasticus (the historian) 76–7 Stead, Christopher 12, 131n.55 Stoic(s)/Stoicism 2–3, 9n.27, 12, 18, 34–6, 39–40, 42n.91, 49–50, 57, 79–81, 83n.77, 85n.92, 92–3nn.117–119, 104n.153, 114–16, 118–22, 124–5, 129nn.49,51, 131n.55, 136n.73, 140n.88, 145, 154n.104, 156n.113, 157n.116, 166–7, 178–9, 193–4 Tabor 9–10 Tertullian 69n.16, 131n.55 Thebes 144n.95 Theodore of Mopsuestia 31n.50 Theodoret of Cyprus 30–2, 31n.51 Theokritoff, Elizabeth 46n.105 Theophilus of Antioch 68n.11, 75n.42, 79n.64

     Theophrastus 69n.17, 96–7, 121n.28, 123–4, 134n.68 Thomas Aquinas 3–5, 5n.16 Tieleman, Teun 68, 69nn.14,16–17, 75n.42 Tobin, Thomas 157n.115 van Kooten, George 35n.67, 47n.106, 156n.113 von Balthasar, Hans Urs 87n.97

Walmsley, Ian 56n.133 Way, A. C. 35n.67 White, Lynn 40n.80 Williams, Rowan 46n.105 Witelo/Adam Pulchrae Mulieris 2 Wolfson, Harry 156n.113 Zachhuber, Johannes 146n.118

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Subject Index Notes: The index includes the main themes, terms and places mentioned in the text and footnotes. The glosses can be read individually and in combination (e.g. ‘hermeneutics’ + ‘scriptural’ –> ‘scriptural hermeneutics’). Tables are indicated by an italic “t ”, following the page number. For the benefit of digital users, indexed terms that span two pages (e.g., 52–53) may, on occasion, appear on only one of those pages. Abyss 18–20 Activity 35n.67, 72–3, 75n.41, 90n.111, 91–2, 102–3, 102n.144, 104n.153, 116n.21, 117n.23, 120, 123–4, 127, 137n.78, 142n.90, 143–7, 146t, 146n.98, 148–9t, 148–9n., 150–1, 153–4, 156n.113, 166–70, 172–4, 181–2, 185–6, 192–5 Aether 61, 71n.23, 92–6, 101n.141, 114–15, 120–2, 124–6, 135n.72, 137–8, 140–1, 161–2, 181–2, 187–8 Affection/affective 50–1, 55–7, 85n.92, 100n.137, 101–2, 131n.55, 132–3, 134n.68, 136–9, 142n.90, 143–4, 164–8, 185 Agile/agility 96–8, 130, 132–3 Alexandria(n) 7–8, 9n.27, 58, 67, 73–5, 73n.34, 122n.39, 154n.104, 159–60, 162–4, 169–72, 181–2, 192–3 Allegory 3, 20, 21nn.5–6, 28–9, 32, 40n.80, 41, 47n.106, 59n.143, 66–7, 71n.20, 76n.43, 80n.67, 81n.68, 104–5, 121n.34, 153, 181–2 of cave, see cave Ambient light, see light (ambient) space 131n.55, 140–5, 146n.98, 166–7, 193–4 Analogy 1–13, 12n.50, 29–30, 44–5, 51n.117, 53, 57–8, 71–3, 81n.68, 83n.81, 89n.106, 90n.111, 100n.137, 111n.9, 120–3, 130n.53, 131, 134–5, 139n.85, 140n.88, 145n.96, 156–7, 159–62, 169–74, 182–5, 187–8, 191–6 Anatomy 23, 137n.77 Angel(s) 17, 27–35, 37–8, 40n.81, 41n.83, 45–7, 49, 53, 120, 122n.39, 151n.101, 187 Angelic 28–30, 32–3, 40n.81, 46–7, 49, 53, 122n.39, 151n.101 Anthropocentrism 39–49, 61 Anthropomorphism 90n.111, 96 Antioch/Antiochene/Antiochean 30–2, 181–2 Archetype 3–7, 24–6, 122n.39, 135n.69, 143n.91, 150n.99, 155–7 Astral/cosmic religion 2–3, 27–8

Astral/aethereal/luminous/spiritual body 29–30, 53, 93n.119, 110–12, 117n.23 Athens 42n.90, 93n.119, 144n.95 Atom(s)/atomism 21–2, 67–70, 82n.74, 134n.68, 140–1, 177–8, 183–9 Aura 102–3, 193–4, 196 Aureole 193–4 Beam 102–3, 104n.153, 134–5, 138, 183–5, 187–9 Being(s) angelic 37–8, 46–7 celestial/heavenly 27–8, 32–6, 46–7, 110 corporeal 94–5 human 31, 33, 38–40, 40n.81, 42–7, 84–8, 156–7, 164, 169–70, 173–4 intelligible 4–5 living 32–3, 35–6, 40 particular 89, 106n.155, 194–5 rational 41n.83, 46–7 spiritual 30n.46, 32, 34–5, 37–8 Black 183–5, 187–8 Blending 96–7, 130n.52, 140n.88 Blue 24–5, 176–7 Body of the universe 35–6, 84–8, 90n.111, 94–5 see also astral body, heavenly bodies, spiritual (body) Brahman 2–3 Brilliance 102–5, 109–10, 112–13, 114n.15, 123–4, 143n.91, 181–9, 191–4 Bright/brightness 43–4, 52n.119, 92n.117, 102–3, 109–10, 112–13, 115–16, 122–5, 127, 131n.55, 132–3, 136–7, 141–50, 165–6, 181, 183–9, 191–5 Burn/burning 50–1, 61, 94, 106n.155, 115–17, 119–23 Burning bush 9–10, 120, 122–4, 124n.43, 133–6, 165–6, 175–6, 185–6, 189, 193–4

  Cambridge change 142n.90 Cappadocian(s) 7–8, 11–12, 32–3, 42–5, 52–3, 58, 62, 70–1, 81n.68, 90n.112, 93n.119, 101nn.139,141, 102n.145, 103n.148, 108–9, 111n.9, 117nn.22–23, 118–19, 122, 122n.35, 137n.78, 139n.85, 140–1, 142n.90, 145, 146n.98, 147, 148–9n., 153–62, 171–2, 181–5, 187, 189 Causal 5–7, 10n.32, 29–30, 35n.67, 51, 52n.119, 57–8, 69n.14, 73n.34, 75–6, 84–9, 96n.124, 100–6, 108–9, 123–4, 134n.68, 144–7, 144n.93, 148–9t, 148–9n., 150–1, 161–6, 168–74, 177–8, 181–2, 192–5 Causality/Causation 1–2, 68–70, 73n.31, 83n.80, 84n.82, 89, 100–1, 102n.144, 104–5, 123–4, 144, 144nn.93,95, 145n.96, 146n.99, 148–9n., 150–1, 162–6, 169, 171–2, 181–2, 192–5 material 68–72, 75–6, 78–9, 125–6, 162–6, 173–4, 181–2 mechanical 68–71, 73–5, 79–81, 98–9 power 11–12, 102–4, 105n.154, 106n.155, 146n.98, 165–6, 181–2 Cause(s) 9n.28, 11–14, 18, 25–6, 29–30, 48–9, 52, 57–8, 67–70, 73–6, 73n.34, 79–81, 84–9, 90n.111, 95–7, 101, 104n.153, 107, 134n.68, 139n.81, 144–7, 144n.93, 148–9t, 148–9n., 152n.102, 153–4, 156n.113, 162–6, 168, 171–4, 179, 184n.1, 189–90, 192–5 Cave (allegory of ) 3, 5–7 Celestial 24n.16, 27–8, 31–2, 35–9, 42–3, 46–7, 49, 53, 64–5, 92–4, 100n.136, 109–26, 128, 133–5, 137n.77, 143–4, 171 see also beings (celestial) Chaldean 35–6 Change (physical) 17–18, 57–8, 61, 75n.41, 89n.108, 91–6, 100n.137, 101, 103–4, 107, 119n.27, 125–6, 131n.55, 139n.85, 142n.90, 143–7, 148–9n., 152, 164–8, 188–9, 192–5 Christ 3–4, 41, 46–7, 111n.11, 173–4, 191–2, 194–5 Christocentrism 41, 46–7, 60n.145, 61, 76n.43 Colour 43–4, 50–1, 52n.119, 54, 55n.130, 56n.133, 84–8, 102n.145, 112–13, 115–16, 124–5, 129–30, 132–3, 137n.78, 142–7, 160–2, 164–5, 175–9, 181, 191–5 Colouration 142n.90, 143–7, 144n.95, 165–7, 194–5 Combustion 12, 124 Concept 9–16, 21–2, 24–5, 27n.34, 54–7, 61, 84–8, 92n.117, 93n.119, 119n.27, 159–62, 166–8, 171, 181–3 Conception 83n.77, 114–15, 141n.89, 159–60 Conceptual/conceptualize 13, 21–2, 26, 84–8, 137n.78, 140–1, 144–7, 152n.102, 157–60, 166–7, 172–3, 175–6, 182–3

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Concurrence 84–8, 112–13, 128, 144–5 Connatural 100–1, 161–2 Contemplation of nature 32–5, 44n.98, 46–7, 59n.140, 60n.145, 81–4, 89, 109, 164, 169–70 of the heavens 39–42, 43n.93, 126–7 of the logos 89–91, 164–6 of the light 109–10 of the self 44–5 of the world 42–9, 91–2, 110–12, 164 Consubstantiality 61, 100–1, 104–6, 108, 165–6 Corona 102–3, 193–4 Correlation 72–3, 83n.77, 112–13, 117–18, 124–5, 187–8 Cosmic 2–3, 19–20, 27–8, 27n.34, 35–7, 37n.71, 40–2, 46–7, 58, 61, 89–92, 109–10, 114–15, 125–6, 135n.70 Cosmogenesis/cosmogony 27–8, 56n.132, 58–60, 64, 66, 68–70, 73–5, 81–2, 81n.68, 89n.107, 97n.131, 104–5, 114–15, 126–7, 164–5, 169–70 Cosmology/cosmological 19–20, 27n.35, 37–8, 42n.91, 46n.105, 55–60, 63–5, 70–1, 78, 83n.77, 93n.119, 114–16, 124–5, 148–9n., 162–4, 169–72, 180, 191–2 cosmological argument/proof 48–9, 73n.31, 82–4 Cosmopolitanism 35–6 Cosmos 34–7, 41–2, 46–9, 51n.117, 55–8, 73–5, 82–8, 95–6, 110–12, 126–7, 156n.111 see also universe Daemon(s) 27–8, 30n.46, 32–5, 40n.81, 41n.83 Dark/darkness 7–8, 10n.32, 13–14, 18–20, 50–1, 79–81, 97–8, 128, 132, 136–7, 142, 147, 181, 183–5, 187–9, 192–4 Day 33, 37–9, 41–2, 45–6, 50–1, 66, 79–81, 147, 153–4 Day(s) of creation 18–20, 27–8, 38–40, 44–5, 58–61, 65–7, 77n.48, 79–84, 87n.98, 89–91, 96, 99–101, 103–6, 109–13, 123, 125–7, 130, 133–5, 143–4, 147–58, 164–7, 169–72, 181–7, 189–92 Daylight 50–1, 144–5, 175–7, 183–5, 187–9 Dazzle/dazzling 24–5, 137 Diffraction 25–6, 193–4 Divine command(s) 19, 66–70, 79–81, 89n.110, 91n.115, 95–6, 97n.131, 98–9, 120 Earth 9–10, 18–20, 30–1, 35nn.65,67, 37–9, 40n.80, 41–2, 45–7, 46n.103, 57, 58n.137, 63, 66–7, 79–82, 85n.92, 87n.98, 90n.111, 92–7, 115–17, 120, 124–8, 132–3

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Effluence 49–50, 131n.55, 132–5, 140–1, 145–7, 183–5, 187–9, 193–4 Egyptian 35–6 Element(s) 11–12, 19–22, 31–2, 55–7, 61, 78–82, 87n.98, 89, 90n.111, 92–100, 100n.137, 101–2, 105–6, 108, 112–16, 117n.23, 118–27, 130–1, 135n.71, 136n.73, 145, 150n.100, 151nn.101–102, 153n.103, 161–2, 164–70, 173–4, 176–8, 180–6, 188–90 Emanation 3–4, 5n.15, 37–8, 51, 102–3, 104n.153, 131n.55, 132–7, 143–4, 146n.98, 183–5, 191–4, 196 Encomium (of sight and/or light) 39–40, 42–3, 46n.103, 47–8, 52–3, 109–10, 126–7 Entailment 98–101, 104–5 Epiphenomenal/epiphenomenon 142, 144–5, 148–9n., 164–8, 188–9, 192–3 Equivocity 99–102, 104–5, 116n.21, 122n.39, 166–7, 169, 172–3, 189 Eye(s) 1–2, 19–20, 27, 31–3, 35–8, 43–4, 46–60, 67, 90n.111, 103–4, 132n.56, 134–5, 137n.77, 138–9, 141, 143n.92, 148–9n., 151n.101, 161–2, 165–6, 168–71, 176–7, 182–3, 185, 187, 189 Eye-like 51 Essence/essential properties 3–4, 63–102, 92n.117, 102n.145, 120, 121n.34, 127, 143–5, 148–9t, 150n.99, 161–6, 168–71, 182–8, 194–5 Exegesis 7n.23, 10n.32, 15–16, 19–21, 21n.8, 27–30, 34n.57, 39–43, 44n.98, 47–8, 56n.132, 58, 59n.139, 62, 64–5, 68n.11, 70–5, 75n.42, 76n.43, 77–82, 84–92, 95n.120, 99–101, 104–15, 119n.27, 122n.39, 123, 125–8, 130, 133–5, 140n.88, 150–1, 153–67, 169–73, 181–3, 187, 189, 191–2 Explanation(s)/explanatory 13–14, 20, 27n.34, 46n.102, 53, 56n.133, 57–8, 61, 70–1, 73–6, 80n.67, 81n.68, 82n.75, 84–8, 92–4, 96–7, 101–4, 110–13, 121nn.28–29, 128, 133–9, 145, 145n.96, 146n.98, 148–9t, 148–9n., 150–1, 155–6, 161–6, 169, 173–4, 176–85, 187–90 Extension 84–8, 123–4, 131–3, 156n.113, 166–7, 193–4 Extensionality 108, 119n.27, 137 Field 27n.34, 132, 138–40 Fire see flame; heavenly fire; physics of fire; propagation (of fire particles); ray (of fire) see also phaos; phlox; phōs; pur Flame 93n.119, 98, 115–17, 120–5, 131n.55, 132–5, 143–7, 146n.98, 148–9t, 148–9n., 165–9, 183–9, 193–4

Form(s) 1–2, 5–7, 43n.93, 82–8, 90n.111, 107, 109, 111n.9, 114–15, 141, 143–4, 148–9n., 150–2, 155–8, 161–2, 181–2 Form-like 113, 173–4 Fuel 12, 114–15, 120, 121nn.28,31, 123–6, 132, 134–5 Glow 97–8, 102–3, 115, 120, 129–30, 193–4 Gods 27–8, 32–3, 51 Good (the)/goodness 5–7, 9–12, 48–9, 72–3, 90n.111, 110n.2, 148–9n., 162–4, 171, 191 Grass 20–1 Green 24–5, 124, 176–7 Halo 193–4 Heat 11–12, 92–4, 100n.137, 102–4, 115, 118–20, 121nn.28–29, 122n.39, 124–5, 132–3, 136, 168–9, 175–9 vital 121nn.28–29, 122n.39, 168 Heaven(s)/heavenly realm 17–20, 29–40, 40n.81, 41–2, 43n.93, 46–7, 53, 58n.137, 66–7, 77n.48, 79–82, 90n.111, 91–2, 93, 94–6, 110–20, 121n.34, 125–7, 137, 189–92 Heavenly bodies 21–2, 35n.67, 38–9, 39n.77, 52–3, 65, 78–9, 81–2, 93nn.118–119, 108–13, 114n.15, 115, 116n.21, 118–19, 124–6, 133–5, 137n.77, 143–4, 147, 152n.102, 153–5, 153n.103, 185–92 Heavenly fire 9–12, 79–82, 114–15, 118, 120–2, 150–1, 187 Hermeneutic(s) 4–7, 14–18, 28n.36, 31–2, 34–5, 37–8, 46–7, 49, 52–3, 58–61, 63–4, 66–7, 71–2, 75–6, 79–91, 104–6, 108–12, 118–19, 122–7, 147–58, 169–72, 175–82, 187, 191–2, 194–5 Hesperus 21–2 Hexaemeron 19, 42–3, 46–9, 58–60, 82–4, 89–91, 108, 164, 169–70 Hexaemeral physics 15–16, 18, 34–5, 55–7, 61–3, 71–6, 78–9, 81–2, 84–9, 102–9, 114–15, 119n.27, 125n.44, 140–1, 157–8, 164–6, 183–5 Historiography 14–15, 22–3, 26–7, 61, 160–2 Homogeneous 112–13, 124–5, 138–9, 183–6 Homoiomerous 136–7 Hydrological cycle 92–4, 118–19, 123, 125–6, 134–5 Hypostasis 168–9, 196 Ignition 165–6, 168, 175 Illuminate/illuminating/illuminative 9–10, 13–14, 19–20, 38–9, 41–2, 94–101, 100n.137, 104n.152, 106n.155, 108, 112–13, 122, 128–30, 131n.55, 134–5, 137–9, 143–7, 146t, 148–9t, 152n.102, 165–6, 171, 176–7, 183–6, 188–9, 192–5

  Illumination 7–8, 10–11, 13–14, 17–18, 24, 51, 96–7, 99–100, 99n.134, 104nn.152–153, 108–12, 129, 131n.55, 132–3, 135n.69, 136–7, 143–50, 146t, 148–9n., 155, 161–2, 165–7, 176, 178–9, 194–6 Immanence 2–3, 2n.8, 91–2, 108, 111n.9, 148–9n., 150–2, 155–8 Imperceptible 97–8, 137n.78, 151n.101, 184n.1 Incorporeal 29n.43, 85n.92, 104n.153, 113, 115, 116n.21, 117n.23 Infinite 112–13, 136–9, 164, 166–7, 173–4, 185, 189–90 Infinitesimal 131n.55, 137 Inflammable 123–4, 134–5, 165–6 Instant/instantaneous 67–8, 68n.11, 84–8, 98–9, 131–5, 137–9, 140n.88, 166–8 Intellect/intellection/intellective 5–9, 37–40, 45–6, 57–60, 62, 64, 70–1, 71n.22, 75n.42, 80n.66, 81–2, 84–8, 105n.154, 157n.116, 166–7, 171–3, 187, 196 Intelligible 2–9, 18, 24–6, 29–30, 31n.50, 57–8, 78, 80n.67, 81n.68, 82n.72, 84nn.82,87, 87n.97, 90n.111, 109, 113, 117n.23, 119, 131, 150–1, 153–8, 169, 171–4, 181–3 Intensity 100n.137, 112–13, 123–4, 127, 132, 138–9, 153n.103, 185–6, 188–9 Intension/intentionality 38–9, 54–5, 77–8, 84–8 Interval 84–8, 110–12, 125–6, 131–2, 135n.72, 137, 137n.78 Intra-cosmic 121n.34, 140–1 Invisible 18–20, 34–5, 35n.65, 42n.91, 59n.141, 96–8, 116–17, 121n.34, 132–3, 196 Irradiance 124–5 Kindle/kindling 17, 96–7, 110–12, 116n.21, 121n.34, 145n.96, 157–8 Lamp 53n.121, 124, 134n.66, 135n.69, 137n.77, 161–2 Lantern/lantern simile 104n.152, 106n.155, 124n.43, 133–5, 147–51 Laws of allegory 20 of change 125–6 of general dynamics (projectile motion) 56n.133, 129–30, 139n.85 of nature 98–9, 108 of physics 10n.32, 125–6, 164 Lichtmetaphorik 4–5, 9–11 Lichtmetaphysik 2, 4–5, 9–10 Light affective 134n.68, 144–5, 146n.98, 148–9t, 148–9n., 165–6, 168 ambient 104n.153, 108–9, 131n.55, 134n.68, 142n.90, 144–5, 144n.93, 146n.98, 148–9t, 165–9, 178–9, 183–5, 189, 192–5

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coalescence of 50–3, 177 ‘from sight to light’ 17–18, 24–7, 160–2, 175–6, 178–9 ‘let there be light’ 18–19, 89–92, 96, 98, 107 ‘light from light’ 9–10, 172–3, 196 physicality of 102–6, 108–9, 129n.49, 155, 179–80 primordial 2, 17–23, 27, 31–2, 37–8, 40, 96–7, 105–6, 110–12, 114–15, 117–18, 133, 147–51, 153–8, 153n.103, 171–4 radiant 104n.153, 108–9, 131n.55, 134n.68, 144–5, 144n.93, 146t, 148–9t, 165–9, 189, 191–5 ‘what is light?’ 13–14, 17–18, 23, 52n.119, 98, 159–68, 171 see also contemplation (of the light); daylight; encomium; metaphysics of light; physics of light; propagation (of light/ray); ray (of light); theology (of light) see also apaugasma; augē; lampēdōn; lux; periaugē; perilampsis; phaos; phōs; phōsphoros; pur; sunaugeia Liminal 108–9, 137n.78, 139n.85 Limit (mathematical) 137n.78, 166–7 Limit of material/sensible world 58n.137, 94–5, 102, 108–9, 113–14, 124–5, 138 Linguistic cosmology 83n.81 Linguistic turn 13, 159–60 Literal interpretation/language 13–14, 19–21, 27, 29–30, 32, 34–5, 37–8, 64–5, 67n.7, 71n.20, 76–7, 79–81, 104–5, 108, 159–60 Luminaries 37n.71, 41, 41n.83, 43n.95, 53, 99–100, 110–12, 133, 147–50, 153–4, 171–2 Luminocentrism 51–4, 55n.130, 58, 160–2, 165–6, 171–2, 175–80 Luminosity/luminousness 101–3, 112–13, 115–16, 122n.39, 124–7, 129–30, 143–7, 165–6, 171–2, 180–2, 185–92 Luminous 19, 37–8, 51–3, 58, 79–81, 93n.119, 98–9, 100n.137, 101–5, 106n.155, 108–13, 115–16, 117n.23, 125–6, 131n.55, 143–7, 157n.117, 165–7, 176–7, 181–2, 188–90, 192–6 Macrocosm/microcosm 42–7, 42n.86, 53–4 Mass 79–81, 92n.117, 93n.119, 118–19, 125–6, 140–1, 164–5, 196 Meaning 2, 5–14, 20, 24–5, 42–3, 52–3, 58–60, 63–7, 70–2, 81n.68, 82–4, 86n.95, 89–91, 102–9, 113, 131–2, 140n.88, 144–5, 153–4, 159–60, 164–9, 171–3, 176, 191–5 Mediation 2n.8, 3, 26, 27n.33, 35n.67, 54, 118–19, 134–5 Medium 12n.48, 46–7, 100n.137, 104n.152, 108–9, 127, 136–47, 146n.98, 148–9n., 161–2, 165–8, 184n.1, 188–9, 192–5

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Metaphor/figurative language/speech 1–11, 11n.34, 13–14, 19–20, 29–30, 35n.65, 80n.67, 84n.82, 87n.97, 91–2, 111n.11, 134n.68, 153, 159–60 Metaphysics of light 1–10, 13–15, 57n.136, 58–60, 145–7, 148–9n., 153–64, 166–7, 169–74, 181–2, 191–2, 194–5 Mobile/mobility 94–5, 98–9, 130, 164–5, 168 Moon 3–4, 17, 33, 35–40, 41n.83, 45–6, 53, 110n.3, 127, 129–30, 137n.77, 153–5, 187–91, 193–4 Motion 19–20, 39, 49–50, 52–3, 58–60, 75n.41, 81–2, 90n.111, 96–7, 112–13, 115–16, 120, 121n.32, 130–2, 130n.54, 137n.78, 139n.85, 140–1, 144n.95, 145–7, 148–9t, 148–9n., 165–9, 192–3 Mystical/mysticism 1, 7–10, 35–8, 53n.120, 58–60, 91–2, 111n.11, 159–60, 191–2 Natural philosophy 34–5, 53–4, 71–2, 83n.80, 95–6, 104n.152, 159–61, 165–6, 171–4, 181–3 Narrative creation (biblical/hexaemeral) 15–16, 18–20, 21n.6, 27–30, 34–5, 41–2, 46–8, 58–60, 62–72, 75–92, 94–6, 103–5, 106n.155, 107–12, 125–6, 147, 150–1, 153–4, 157–60, 162–5, 169–73, 181–2 chain 83n.77, 95–6 coherence of 66–7, 79–84, 157–8 consistency of 68–70, 79–84, 105–6 dual interpretation 84–8, 147–53, 181–3, 187 episodes of 82–4, 89–91 form 89–91, 95–6, 164 inner dialectics of 81n.68, 171–2 logic 14–15, 41n.85, 70–1, 82–4, 109–12, 125–6, 157–8, 176–8 oculocentric 26–7, 46–7, 161–2, 165–7, 175–6 order 78, 82–4, 95–6, 125–6, 164 purpose 58–60, 58n.137, 82–8 sequence 41–2, 58–60, 66–7, 82–4, 84n.87, 94–6, 125–6, 151n.101, 153–4, 181–2 steps 58–60, 125–7, 169–70 structure 82–4 time 58–60 Nicaea(n) Anti-Nicene 137n.78, 148–9n., 194–5 Nicene 9–10, 11n.34, 14–15, 18n.1, 172–3, 194–6 Non-Nicene 194–5 Post-Nicene 3–4, 9–10, 75–6, 124–5, 137n.78 Pro-Nicene 148–9n., 194–5 see also light (‘light from light’) Night 18–20, 33, 38–9, 41–2, 41n.83, 50–1, 79–81, 112–13, 134n.66, 147, 187–9

Noumenal 13–14, 57–60, 165–6, 171–2 Noumenon 58–60 Objective 26–7, 54–7, 160–1, 176–80 Ocular/ocularism/ocularist 27, 29–30, 32, 37–8, 58, 160–1, 176–8, 183–5 Oculocentrism/oculocentric 14–15, 25–7, 31–2, 37–40, 46–50, 52–8, 61–2, 160–2, 165–7, 171–2, 175–80 see also narrative (oculocentric) Opacity/opaque 129–30, 137n.77, 138, 141, 185–6 Optics 1–2, 17–18, 22–7, 49–50, 53–5, 57, 128, 129n.49, 130n.54, 132n.56, 137n.77, 139n.85, 160–2, 175, 193–4 see also paradigm (optical/visual); reflection Paradigm Aristotelian 178–9 cultural 53–4 forms as 85n.92 hexaemeral 53–4, 58 intelligible 57–8, 155, 156n.113, 187 Newtonian 55–7 optical/visual 18, 26, 27n.33, 53–7, 179–80 Platonic 42–3, 53–4, 178–9 Ptolemaic 178–9 scientific 54–7, 160–1, 175–6 shift 17–18, 25–7, 54 Stoic 42n.91 transcendent 155–6 Participation 2n.8, 3–8, 55, 116–17, 129, 148–9n. Particles 21–2, 55–7, 100n.136, 112–13, 124–5, 135n.71, 136n.75, 137n.78, 140–1, 141n.89, 145–7, 146n.98, 148–9n., 165–8, 176–8, 183–90, 193–4 Pedagogy 4–5, 9–10, 28–9, 42–3, 58–60, 65–7, 159–60, 171 Perceive/perception 17–18, 23, 25–7, 27n.33, 29n.43, 30n.46, 35–7, 45–9, 51, 52n.119, 53–8, 58n.137, 61, 84n.82, 103–4, 107, 126–7, 130–1, 143–7, 148–9n., 160–1, 165–6, 168–9, 171–4, 176–80, 182–3, 185, 187–9 Perceptible 49–50, 130–1, 143–7, 151nn.101–102, 153, 184n.1, 185, 187 Performance/performative 52, 58–60, 64, 67n.7, 109 Phenomenal 13–14, 18, 27n.34, 57–60, 84–9, 91–2, 94–5, 96n.124, 102, 108–9, 143–7, 151n.101, 152, 165–6, 171–2, 176–7, 180, 187–9, 191–4 Phenomenology 13–14, 55, 57–8, 58nn.137–138 Phenomenon 82–4, 89, 92–4, 102–4, 108–9, 131n.55, 139n.85, 140n.88, 144–7, 164, 173–4, 179–80, 184n.1, 193–4, 196 Photon 55–7

  Physical world 9–10, 18, 21–2, 55–7, 63–4, 82n.72, 89–92, 102–3, 108–9, 113, 117n.23, 125–6, 143–7, 155, 156n.113, 157–8, 164–5, 168, 196 Physicalism 2–5, 29–30, 49, 104–6, 108, 150–4, 157–8 Physics of light 1–2, 8–18, 24–5, 27, 52n.119, 53–4, 56n.133, 57–65, 70–1, 75–6, 78–81, 91–2, 96–7, 102–9, 111n.11, 112–13, 117–18, 122n.39, 124–7, 129, 132–3, 145–7, 150–1, 155, 157–8, 161–2, 165–7, 175–82 Physics of fire 12, 106n.155, 112–13, 120, 122n.35, 134–5, 161–4 Physiology 23, 25–6, 134–5 Planet(s) 19–22, 35n.67, 81–2, 93n.119, 124–5, 134–5, 187–90 Pneumatic 140n.88 Power(s) 11–12, 28–30, 31n.51, 32, 34–5, 35n.67, 46–7, 72–5, 75n.42, 84–9, 90n.111, 94–106, 108, 110, 112–13, 115–16, 117n.23, 119, 122–5, 122n.39, 127–30, 132–3, 136, 138–41, 143–51, 146t, 148–9t, 153–6, 153n.103, 161–2, 165–71, 173–4, 181–7, 189, 191–5 Pre-cosmic 55–7, 121n.34 Prepositional metaphysics 148–9t, 148–9n. Propagation of light/ray 18, 23–4, 49–50, 131n.55, 137n.78, 144–5, 148–9n., 175–8, 192–3 of fire particles 165–6 Proprium 11–12, 24–5, 100n.137, 101–2, 101n.139, 148–9t Property 8–12, 14–15, 52n.119, 53–7, 61, 68–73, 73n.35, 85n.92, 89, 92n.117, 94–5, 98–107, 112–13, 115–16, 121n.29, 125–7, 129–30, 138–9, 142–7, 148–9n., 150–1, 160–2, 164–74, 176–89, 193–4 Purity 114n.15, 116–18, 123–5, 127, 138, 185–6, 188–9 Quality 35n.67, 56n.133, 73–5, 84–9, 90n.111, 92–6, 97n.130, 102–5, 108, 113, 119n.27, 123–5, 132, 142–3, 147–50, 151nn.101–102, 164–6, 179–85, 196 Qualitative 56n.133, 108–9, 120–2, 138–9 Radiance/radiant 37, 98–9, 102–3, 104n.153, 109–10, 112–13, 123–4, 127, 139nn.84–85, 145n.96, 146n.98, 148–9n., 168–70, 172–3, 191–5 see also light (radiant) Ray ocular/visual 24, 24n.16, 51, 53, 54n.122, 132n.61, 138–9, 138n.79, 140n.88, 183–5 of fire 102–3

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of light 24, 27n.34, 50–1, 53, 54n.122, 108–9, 127–41, 143–7, 146t, 148–9t, 148–9n., 161–2, 165–9, 183–5, 187–9, 192–5 propagation of, see propagation (of light/ray) theory 104n.153, 127, 131n.55, 133nn.62,65, 134n.68, 136, 140–1, 142n.90, 166–7, 178–9, 183–5, 192–3 Reception history 5–8, 22–3, 34–5, 42n.89, 50, 76–7, 88n.102, 103n.147, 107, 134n.68, 136n.74, 183–5 Reader(s) effect/response 9–10, 13, 18–22, 27–9, 32, 37, 41–2, 46–7, 54–5, 58–60, 63, 68, 70–1, 73n.35, 75–6, 79–84, 91–2, 100n.136, 103n.146, 105–7, 109–12, 123, 125–6, 125n.44, 127–8, 152n.102, 161–4, 169–70, 173–4, 179–85 community of 81n.68, 161–2, 178–9 Red 24–5, 185–8 Reflection (optics) 25–6, 27n.33, 129–30, 151n.101, 160–2, 175–9, 189, 191–5 Refraction 25–6, 27n.33, 55n.130, 151n.101, 160–2, 178–9, 193–4 Relativity 104n.153, 131, 162–4, 166–7 Relativism 177–8 Rome 67, 157n.116 Scripture 3–4, 7–8, 14–15, 18, 20–2, 21n.6, 28–9, 32n.52, 41–2, 58–72, 73n.35, 75–6, 80n.67, 81n.68, 82–4, 89–92, 94–7, 96n.124, 105–13, 125–7, 125n.44, 153–4, 157–64, 169–70, 191–2 Scriptural 3–4, 9–10, 13–15, 25n.23, 35n.67, 36n.68, 59n.139, 64–7, 70–1, 76–84, 79n.64, 94–5, 101, 108–12, 117n.23, 119–22, 125n.44, 146n.98, 148–9n., 151n.101, 157–65, 171–3, 178–9, 181–2, 191–2, 194–5 Semantic(s) 5–10, 13, 103n.146, 108, 144–7, 191–2 Sensible 3–5, 9n.28, 29–30, 42n.91, 57, 59n.141, 73–5, 78, 84–9, 84n.82, 91–5, 102–5, 108, 113, 133n.62, 152n.102, 153–8, 164–6, 169–74, 176–83, 185, 187, 191–2 Separation 18, 31, 38–9, 41–2, 65, 89, 96–9, 110–15, 122–5, 127, 130, 145–7, 164–5, 189 Sign/signification 10n.32, 13, 21–2, 29–30, 32–3, 41, 53n.120, 148–9n. Sight 5–7, 17–18, 22–7, 29–30, 32–3, 39–40, 43–4, 43n.93, 46–57, 61, 103–4, 160–2, 165–6, 175–80, 187 see also vision Simple 43–4, 85n.92, 109–10, 114, 136–7, 152n.102, 164, 169–70, 173–4 Simplicity 12, 58–60 Solar theology 112n.12

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Spirit 18–20, 35n.67, 81n.68, 120, 123, 148–9n., 159 Spiritual 28–9 beings, see beings (spiritual) body 29n.43, 110–12 exercise 58–60 interpretation 29n.39, 80n.67, 81n.68, 150–3, 157–8 senses 29–30 world 28–31 Star(s) 17, 19–22, 27–33, 35–44, 41n.83, 45–7, 53–4, 81–2, 92–6, 99–100, 102–3, 109–10, 111n.9, 112–13, 115–16, 120–2, 124–7, 134–5, 138–9, 143–4, 150–1, 153–5, 157n.117, 162–4, 178–9, 187–94 Subjective 54, 164–5, 176–8 Sublunary 40n.81, 41–3, 41n.83, 46–7, 92–4, 114–16, 118–26, 134–5 Supralunary 35n.65, 41n.83, 42–3, 46–7, 46n.103, 92–4, 114–16, 118–20, 122n.35, 123–6 Substance(s) 11–12, 31n.50, 33, 84–8, 90n.111, 92–106, 108–10, 112–14, 116n.21, 117n.23, 118, 120, 121nn.29,34, 124–7, 129–30, 136–7, 140n.88, 141n.89, 143–50, 146t, 148–9n., 151nn.101–102, 153–5, 161–2, 165–6, 168–70, 181–5, 189–90 Subtext 28–9, 82–8, 91–2, 157n.117, 181–2, 191–2, 196 Sun 3–7, 9–14, 17, 33, 35–41, 45–6, 51–4, 57–8, 65–6, 68–70, 79–81, 92–4, 100n.136, 101–3, 104n.152, 110–12, 110n.3, 115–16, 118–19, 122, 124, 127–30, 131n.55, 134–6, 137n.77, 138–9, 143n.91, 145n.96, 147, 148–9n., 151n.101, 153–5, 161–2, 168, 171, 175–8, 181, 183–94, 196 Sun simile (Plato’s) 3, 5–8, 5n.16, 51, 57–8, 168, 171–3 Sunlike 51–3 Synecdoche 19, 99–100, 104–5, 156n.113 Tangibility/tangible 57, 94–5, 113n.14, 185 Teleology/teleological 38–43, 45n.99, 46–9, 53–4, 61, 67–70, 148–9n., 177–8 Telescope 21–2 Temporal/temporality 33, 73–5, 84n.87, 131, 131n.55, 137n.78, 150–1, 153n.103, 181–2 Theocentrism 46–7 Theology and economy 3–4

mystical, see mystical natural 28–9, 34–5, 42n.89, 59n.140, 68–70, 84n.82 of light 1–2, 11–12, 18n.1 philosophical 9n.27, 17–18, 70–1, 100n.137 Time 19–20, 41–2, 46–7, 55–8, 87n.97, 94–5, 99nn.133–134, 125–6, 131–3, 134n.66, 135n.72, 137, 147–50, 152n.102, 153–5 Transmission 53, 75n.41, 131–2, 136–7, 137n.78, 139n.85, 140n.88, 141, 143–7, 148–9t, 148–9n., 166–8, 192–4 Transcendence 2n.8, 3–8, 148–9n., 152n.102, 155–8 Transparency/transparent 93n.119, 94–5, 104n.153, 116, 121n.34, 137, 140n.88, 141–4, 161–2, 165–6, 183–5, 187–9, 193–4 Truth(s) 1–2, 5–7, 171 Type–token 5–7, 155–7 Universe 2–7, 32, 34–5, 35n.67, 41–2, 41n.83, 43n.93, 46–7, 53, 68–70, 72–5, 79–84, 87n.98, 89–96, 98–100, 102–3, 108–9, 112–15, 117–20, 124–6, 128, 130–1, 138, 139n.85, 151nn.101–102, 152, 155–6, 162–4, 169, 173–4, 187–90 see also cosmos Venus 21–2 Visibility/visible 5–7, 13–14, 24–5, 27n.34, 28–31, 31nn.50–51, 37, 39, 42n.91, 46–7, 52n.119, 53n.120, 57, 58n.137, 59n.141, 61, 65, 80n.67, 94–5, 129n.51, 141, 143–7, 151nn.101–102, 153, 155, 157–8, 160–1, 164, 166–7, 177–8, 181–3, 185–8, 193–5 Vision 1–2, 9–10, 14–15, 17–20, 22–7, 29–30, 30n.46, 31–2, 35–9, 40n.81, 42–3, 46–54, 57–61, 81–2, 89–91, 103–4, 107, 114–15, 126–7, 133n.62, 134n.68, 140n.88, 141, 155, 159–62, 171–82, 185, 187–94 see also sight Visual/visualize 19–20, 23–4, 26, 27n.34, 32, 43–4, 48–9, 53–4, 58, 61, 107, 137n.77, 148–9n., 171, 176–80, 183–6, 188–9, 193–4 see also paradigm (optical/visual); ray (ocular/visual) White/whiteness 52n.119, 142–3, 147–50, 182–9 Yellow 176–7, 185–6

Glossary Notes: The glossary includes key Greek, Latin and Hebrew terms together with their translations, as they are used in the text and footnotes. Tables are indicated by an italic “t”, following the page number. For the benefit of digital users, indexed terms that span two pages (e.g., 52–53) may, on occasion, appear on only one of those pages. agathon (the Good) 5–7, 23 aisthēsis/aisthēton (sensation; sensible; of perceptible nature) 30n.46, 58n.137, 93n.119, 113, 152n.102, 155, 156–7 aition (explanatory cause) 13–14, 51, 95–6 akataskeuastos (unformed) 19 aktis (ray) 93n.119, 127–9, 131n.55, 132–3, 134nn.66,68, 144–5, 146t, 183–5, 192–5 analogon (analogous) 5–7, 57–8 antiperistasis (interchange of places) 140n.88 antiphōtismos (reflection of light rays) 129–30 aoratos (invisible) 19 apaugasma (radiant or ambient light; sunshine; brightness) 98–9, 102–3, 146n.98, 191 aporroē (emanation) 131n.55, 132–5, 137n.78, 183–5 archē (beginning; principle) 19, 42n.91, 58–60, 175, 194–5 augē (bright beam) 97–8, 102–3, 120–2, 130n.52, 131n.55, 134n.68, 135n.72, 140n.88, 144–5, 152n.102, 183–5, 192–5 chroa (colour) 116 chusis (pouring forth) 131n.55, 132n.57 dianoia (reason/reasoning; meaning) 79n.64, 83n.78, 110n.5, 156–7 diastema (interval; extension) 84–8, 137n.78 diaugēs (transluscent) 140n.88, 141n.89 diakrisis (separation) 89, 96, 112–15, 135n.71, 152n.102, 164–5, 188–9 didaskalia /didaskaleion (teaching; teaching ground) 42–3, 65, 79n.64 doxa (opinion; brilliance) 112–13, 191–4 dunamis (power; property; capacity) 35n.67, 84–8, 89n.106, 90n.111, 91n.113, 95–101, 96n.122, 100n.137, 106n.155, 111n.6, 112–13, 122–3, 125–6, 129, 133, 146n.98, 147–51, 153–4, 153n.103, 156n.113, 181–5

eikon (image) 5–7, 90n.111, 155–6, 157n.116 energeia (activity; actuality) 35n.67, 84–8, 117n.23, 137n.78, 146n.98, 166–7, 194–5 epekeina tēs ousias (beyond being) 5–7, 9–10, 171 homoousion (consubstantial) 101–2, 148–9n. homoion (akin; similar) 50–1, 177–8, 183–5 homoiotēta (similarity) 22–3 hulē/hulikos (matter; material) 84–8, 92n.117, 106n.155, 114, 120, 152n.102, 193 hupokeimenon (substrate) 84–8, 120, 143, 147–51, 181–2, 185–6 Kabod Jahwe (glory of God) 191–4 kataugazein (shine upon; illuminate) 152n.102 kataphōtizein (fill with light) 137 lampēdōn (luminescent glow) 193–4 lamptēr (lamp) 134n.66, 135n.69 logos (word; reason; account; definition; instrumental cause; immanent principle) 14–15, 35n.67, 42n.91, 46–9, 51, 58–60, 65, 73–5, 84–92, 96–8, 101–2, 108–13, 116, 122–3, 125–7, 135n.69, 144n.95, 148–9n., 150–2, 155–8, 164–6, 169–74, 182–3, 189–90, 193–5 luchnos (lantern; lamp) 106n.155, 124, 133, 134n.66, 135nn.69–70, 147–50 lux (light) 19–22, 91n.115, 157–8, 171–2 metaxu (between; medium) 140–1 ochēma (vehicle) 35n.67, 110–12, 133, 147–51 ousia (being; essence; substance; underlying body) 5–7, 9–10, 13–14, 84–8, 90n.111, 93nn.118–119, 97–101, 113, 113n.14, 116n.21, 143, 146n.98, 147–52, 156–7, 171, 181–5, 194–5 opsis (ocular ray) 51, 183–5 ophthalmos (eye) 38n.72, 84–8, 155

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paradeigma (model; example) 11n.34, 155–6, 155n.107 periaugazein/periaugē (to shine around; surrounding light) 193–4, 196 perilampein/perilampsis (to light around; shining around) 98, 196 phainomenon (appearance; sensible; perceptible; phenomenal) 57–60, 144n.94, 152, 180, 187 phainomenos (visible) 65 phainesthai (to appear; phenomenality) 57, 144–5 phantasia (impression; perception) 57, 144–5, 187 phaos (light; fire) 57, 104n.152, 134n.68, 144n.94 phausis (kindling of light; lighting) 110–12, 144–5, 146t, 147–51, 148–9t, 153–4 phlox (flame) 93n.119, 115–17, 120–2, 124, 135n.72, 144–5, 148–9t phōs (light; fire) 6n.17, 21–2, 24, 50–3, 57, 93n.119, 98–101, 104n.152, 106n.155, 110–13, 115–18, 117n.23, 122–3, 128, 133–5, 137, 137n.78, 139n.85, 142–5, 146t, 146n.98, 147–55, 148–9t, 183–5, 189, 191, 193–6 phōsphorein (to bear or bring light; to shine) 155 phōsphoros (light-bringing) 50–1 phōstēr (luminary; star) 99–100, 110–12, 133, 147–50, 148–9t, 153–4 phōtismos (illumination) 147–50 phōtistikos (illuminating) 96n.122, 97–101, 106n.155, 112–13, 129, 153n.103, 183–5 phōtizein (illuminate) 124, 133, 147–51 phōtoeidēs (luminous) 51, 93n.119 phusikē idiotēs (natural property) 100–1 phusikē theōria (contemplation of nature) 58–60, 75–6, 79n.64, 81–2

phusis (nature; pure substance) 13–14, 84n.87, 93n.119, 94–6, 101, 106n.155, 113, 120, 129, 133, 137, 146n.98, 147–51, 153–4, 153n.103, 183–5 pneuma/pneumata (spirit(s); angel(s); finer substance) 12, 33n.56, 49–50, 121n.29, 156–7 poiotēs (quality; form) 87n.98, 88n.100, 90n.111, 96n.122, 101n.139, 143, 147–51, 181–3 pollachōs legomenon (a term of many senses) 144–5, 146t, 169 psuchagōgia (pedagogy of the soul) 65 psuchē (soul) 35n.67, 111n.9, 156–7 pur (fire; light) 51, 93n.119, 96n.122, 97–8, 100n.136, 104n.152, 106n.155, 113–14, 113n.14, 116n.21, 117n.23, 120, 124, 129n.51, 133–5, 134n.66, 134n.68, 144–5, 146t, 147–50, 148–9t, 152n.102, 153n.103, 184n.1 stoicheion (element) 93n.118, 117n.23, 152n.102 sundromē (concurrence) 84–9, 112–13, 135n.71, 152n.102 suntheton (compound) 143, 147–51, 156–7, 181–2 sugkrasis (blending; mixture) 129n.50, 130nn.52–53 sugkrisis (compression) 188–9 sunaugeia (coalescence/comingling of light rays) 161–2, 171 sunkatabasis (condescension; consideration) 28–9, 31–2 tasis (stretch) 131n.55, 140n.88, 166–7 theoprepōs (in a sense worthy of God; befitting God) 96 tohu wa–bohu (without form and void; in a chaotic state; all in all) 97n.130, 114–15, 164–5