Introduction

Summary

In this introduction, I outline Proclus’ relationship with Aristotle and provide an overview of the state of the art. I discuss Proclus’ views on the so-called harmony of Plato and Aristotle and contrast it with the views of other, contemporary Neoplatonists, showing that Proclus stands out as more critical of Aristotle. I show that the concept of motion provides a perfect avenue for understanding how Proclus sees the tension between Plato and Aristotle. Lastly, I explain how Proclus differentiates distinct levels of motion which also structure my discussion in the monograph.

I.1 Proclus’ Ambiguous Relationship with Aristotle

Neoplatonists from Porphyry (234–305) onwards emphasise Aristotle’s supposed doctrinal proximity to Plato – if not outright agreement and harmony, sumphōnia (συμφωνία). This conviction was instrumental in shaping the perception of Aristotle’s authority for the rest of antiquity and beyond. The expression of this idea depends on each Neoplatonist and, in the case of the most significant Platonist after Plotinus (205–270) – the ‘founder’ of Neoplatonism – Proclus (412–485), it is questionable whether he upheld the doctrine of a συμφωνία between Plato and Aristotle in the first place. In fact, one aim of this book is to deny this supposition.

Proclus was an avid student of Aristotle. As is also the case for the earlier Neoplatonists, Aristotle’s philosophy was a constitutive element for the development of Proclus’ thought, shaping his views, for instance, in logic, natural philosophy but also metaphysics. Unlike his predecessor Syrianus (d. 437), Proclus wrote little on Aristotle’s works themselves, commenting only on the Organon, which was first among the works of Aristotle to be read by the students in the Neoplatonist schools.¹ Although these commentaries do not survive, he shows a remarkable use of Aristotle in various other treatises which are helpful in understanding his reception of Aristotle. Indeed, his move as a student from Alexandria to Athens seems already to have been motivated by finding a better environment to study Aristotle (Marinus, VP §10.1–10). There, he studied Aristotle’s works extensively first under Plutarch of Athens (d. 432) – the founder of the Athenian school of Neoplatonism² – and then under Syrianus. He completed the Aristotelian curriculum, which was regarded as preparatory for the study of Plato, in less than two years.³ The result is a fascinating mixture of appreciation and rejection of Aristotelian ideas; in fact, Proclus appears to be the most ardent Neoplatonist critic of Aristotle after Plotinus. Yet, unlike Plotinus,⁴ Proclus’ engagement with Aristotle has been little and only deficiently studied.

The aim of this monograph is to close this gap by offering an extensive discussion of Proclus’ use of Aristotle, especially his criticism of Plato. This is achieved by elucidating a concept which is central to Proclus and shows his far-reaching engagement with Aristotle: kinēsis (κίνησις), which I render henceforth as motion. This term is used by the Neoplatonists to refer to change generally and differs significantly from our own understanding, as I outline in Section I.4. Motion is of crucial importance for Proclus as he not only dedicates a separate treatise to it (Elements of Physics) but also elaborates on it throughout his oeuvre. Also, in this area Proclus’ approach to Aristotle and his harmonisation of Aristotle with Plato – or lack thereof – becomes most tangible. Thus, I do not aim to offer a full picture of the places where Proclus engages with Aristotle, since such a work would be of little philosophical value. Rather, my intention is to analyse Proclus’ reception of Aristotle in the broader system of his philosophy by focusing on this one specific issue. In this way it will become clearer how Proclus proceeds and to what degree he believes Aristotle agrees and disagrees with Plato. In presenting Proclus’ views on motion, I will not only elucidate his exegetical method but also his underlying philosophical views. As will emerge, many of the current discussions in scholarship on issues such as the nature of self-motion, the causality of the unmoved mover etc. were just as lively in antiquity as today. Because Proclus does not engage in the potentially straightjacketing harmonisation-project of his Neoplatonist contemporaries, he offers individual and philosophically worthwhile interpretations of Aristotle which have not been sufficiently studied.

There is ample reason for this undertaking. First, Proclus’ systematic outlook on philosophy and the richness of his oeuvre, which covers a wide range of topics, from ethical to metaphysical questions, allows us to trace back the impact of Aristotle’s thought. Secondly, his critical appreciation of Aristotle offers us the opportunity to look for the reasons behind this stance and to compare it with other Neoplatonists of his time. On many occasions in his work he makes explicit or implicit references to Aristotle and relates Aristotle’s views to Plato’s. Foremost among these is the introductory Elements of Physics which aims to prove more geometrico the existence of an unmoved mover through a meticulous analysis of motion in the physical world. His systematic Elements of Theology also contains a plethora of Aristotelian notions and terminology. Also significant is Proclus’ refutation of various Aristotelian criticisms targeting Plato’s Timaeus which can be found in the commentary on the Timaeus and were summarised in a lost work entitled Investigation of Aristotle’s Objections to the Timaeus.⁵ A similar work which forms an appendix to Proclus’ commentary on the Republic is his Investigation of Aristotle’s Objections to the Republic.⁶ A major concern for him was also his rejection of Aristotle’s criticism of Plato’s theory of forms.⁷ Additionally, one can reconstruct various objections to Aristotle’s theory of concept formation,⁸ nature,⁹ causality (Section 4.3.2), time,¹⁰ psychology,¹¹ intellect (Section 4.3), elemental constitution of the heaven (Section 1.2.3.1) and methodology¹².

Methodologically, this book is guided by five concerns: (1) I believe extensive groundwork in Plato and Aristotle is crucial for understanding Proclus’ thought and his approach to Aristotle’s criticism of Plato. By focusing on these classical authors, ancient debates on motion are more clearly illuminated. I thus study Proclus both as an interpreter and as a philosopher in his own right; (2) This accounts for at times quite detailed discussions of Platonic and Aristotelian scholarship which shed light on the very similar concerns shared by Proclus and place his views in relation to modern scholarship; (3) In order to bring out more clearly Proclus’ individual views on Aristotle I make copious use of other late antique commentators, especially Syrianus and Simplicius (480–560). This allows me to contrast Proclus’ approach with those common at his time; (4) In my selection of texts, I focus on a wide range of passages that clearly demonstrate Proclus’ engagement with Aristotle. Primarily, these come from his commentaries on the Timaeus and the Parmenides as well as from the Elements of Theology and the Elements of Physics, but I also make extensive use of the Platonic Theology and the commentary on Euclid’s Elements; (5) Proximity to the text with an eye to the peculiarities of the Greek are central for my undertaking. On numerous occasions I offer close readings of the hitherto underexplored passages, thereby yielding innovative results and/or modifying established interpretations.

I.2 Status Quaestionis

As historical disciplines have increasingly turned towards the study of late antiquity in the last fifty years or so, the last few decades have also led in philosophy to a renaissance of Neoplatonist studies. While Plotinus was initially the primary focus, Proclus has recently garnered significant interest, as numerous editions and translations, for example, of his commentaries on the Timaeus and the Republic, as well as major publications providing overviews of his philosophy, demonstrate.¹³ Of great interest remain Proclus’ metaphysics, particularly his interpretation of Plato’s Parmenides and his systematic treatise Elements of Theology,¹⁴ as well as disciplines that are close to it, such as psychology¹⁵ and religion.¹⁶ Recently, scholars of Proclus have also focused on non-metaphysical topics such as natural philosophy, for example, Martijn (2010a), and Horn and Wilberding (2012), and ethics, for example, Coope (2020). Yet, certain issues have not been discussed sufficiently. Among these ranks also Proclus’ relation to Aristotle, of whom he makes extensive use throughout his oeuvre, and, more specifically, his view on Aristotle’s criticisms of Plato.

The most significant publications on the Neoplatonist harmonisation of Plato and Aristotle are the monographs by Gerson (2005), Karamanolis (2006) and Hadot (2015).¹⁷ Of these three, Karamanolis (2006) is not relevant for my concerns, as he deals only with the development of the harmony thesis up to Porphyry. The remaining two monographs have some severe flaws in their treatment of Proclus which I am going to address briefly. Of significance for Proclus’ views on Aristotle are the contributions by Steel (1987a), (2003), (2016), Opsomer (2009) and d’Hoine (2016) which are central for my project.¹⁸

The first major publication on the Neoplatonist doctrine of harmony of Plato and Aristotle was Gerson’s Aristotle and other Platonists in 2005. In light of his interest in this work to show the similarity between Plato and Aristotle Gerson prefers Neoplatonists with strong harmonist tendencies – an exception is Plotinus – simultaneously downplaying the more critical stances of Syrianus and Proclus.¹⁹ This sometimes obscures the distinction between views of specific philosophers and, more generally, between Athenian and Alexandrian positions on Aristotle. Gerson’s procedure is particularly prominent in his chapter on psychology where he maintains that for the Neoplatonists ‘Aristotle plainly makes large epistemological and psychological claims in De anima that are in harmony with Platonism’ (132). I do not believe this conclusion is warranted for the following reasons. First, Gerson primarily relies on the strongly harmonistic interpretation of De anima by Ps.-Simplicius, disregarding Hermias’ more balanced position in his commentary on the Phaedrus and Proclus’ outright critique of Aristotle’s views in, for example, his commentary on the Timaeus.²⁰ Hermias is not mentioned at all, while Proclus is cited only where it suits Gerson’s general interpretation. Secondly, Gerson does not take Aristotle’s critique of self-motion in De anima 1.3 seriously enough – unlike the late antique commentators. He dedicates only a paragraph to it, suggesting that it is not worthy of discussion, since for the Neoplatonists the ‘question is … the harmonization of two accounts of how immortal intellect is related to embodied soul’. In this monograph, I show that the case of Proclus goes against a unitary view of the dogma of harmony, which is supposedly shared by all Neoplatonists.²¹ Moreover, I argue that Aristotle’s criticism of Plato is constitutive for the development of certain psychological views in Proclus, and thus needs to be taken seriously (see Chapter 2).

Hadot (2015) aims at continuing and expanding on Karamanolis’ work, while simultaneously building on her earlier influential studies on Alexandrian Neoplatonism.²² Her book discusses the different Neoplatonist approaches to Aristotle and the harmony thesis from Porphyry to Simplicius by looking at the Athenian and Alexandrian schools. My objections to her work focus on two aspects: (1) the idea that exegetical practices between Athens and Alexandria differ only in degree; (2) the lack of a serious discussion of Proclus. Regarding the latter, it is noteworthy that, although Hadot’s aim is to discuss the harmonising strategies of all Neoplatonists after Porphyry, her chapter on the most important late antique Platonist, Proclus, is exceedingly short, comprising only five pages, and fails to offer a satisfying overview of his stance on Aristotle. Her claim that Proclus ‘set[s] the most narrow limits to the tendency to harmonize the philosophies of Plato and Aristotle’ (125) is thus not sufficiently backed up and needs further discussion, since it is questionable whether Proclus maintained that their philosophies are in fundamental agreement at all. The chapter’s flaws are both in regard to the lack of primary texts mentioned as well as of secondary literature. She fails to point out the fundamental articles by Steel who greatly contributed to our understanding of Proclus’ relationship with Aristotle.²³ Unmentioned remains also Opsomer (2009) on Proclus’ Elements of Physics and its appropriation of Aristotle’s theory of motion. These shortcomings in the discussion of Proclus have consequences for my first objection, as Hadot is unable to assess accurately the differences between the Alexandrian and Athenian approaches to Aristotle without an extensive treatment of Proclus. Consequently, she holds on to the idea of a harmony-doctrine among all Neoplatonists after Plotinus which I will show to be fallacious.²⁴

Chiaradonna (2019a) emphasises that there were different expressions of the harmony thesis (385). Nevertheless, he seems to assume – like Gerson and Hadot – that it was universally accepted, as even Proclus is said to have ‘set the narrowest limit to the tendency to harmonise the philosophies of Plato and Aristotle’ (386).

While Gerson, Hadot, Chiaradonna and Sorabji²⁵ emphasise the pro-harmonist tendencies among all Neoplatonists, recently, a number of scholars such as Helmig (2009: 438–9 and 2012: 205–12), D’Ancona (2015: 382–4) and Golitsis (2018: 69) have started questioning precisely this universality, as Syrianus and Proclus do not seem to adhere to it in their criticisms of Aristotle. Instead, Golitsis (2018), for instance, distinguishes between an Alexandrian ‘concordist’ position and an Athenian ‘complementarist’ approach. In their entry on Proclus in the Stanford Encyclopedia of Philosophy, Helmig and Steel claim that Proclus ‘is certainly not an advocate of the “harmony of Plato and Aristotle”, which became the leading principle of the Alexandrian commentaries (of Ammonius and Simplicius)’. These approaches are much more sensible and seem to capture Proclus’ position on Aristotle more accurately. However, they require a more thorough foundation in Proclus’ texts.

The work of the last group of scholars can be linked to Steel’s fundamental research that focuses on Proclus’ deviation from the general conciliatory tone of other Neoplatonists. Steel has discussed Proclus’ negative attitude mainly in four papers about Proclus’ critique of efficient causality in Aristotle (1987a), his rejection of Aristotle’s criticism of Plato’s theory of forms (1996), his characterisation of Aristotelian philosophy as dependent and inferior to Plato’s (2003) and, most recently, his refutation of various Aristotelian criticisms against the Timaeus (2016). Building on these works, d’Hoine (2016) recently concluded in an overview of Syrianus’ and Proclus’ positions on Aristotle that ‘their attitude is no longer characterised by benign appraisal and tacit adaptation, but rather by critical appreciation’ (374).

My goal is to integrate these specific discussions into a broader and more inclusive framework in order to offer a fuller examination of Proclus’ negative as well as positive references to Aristotle which so far is not available. This study contributes to Neoplatonist studies in a way which makes it much easier to classify Proclus’ position beyond a simple binary opposition of ‘harmonist’ and ‘non-harmonist’. As it emerges, Proclus holds a wide range of beliefs about Aristotle while ultimately rejecting the idea that Aristotle is in fundamental agreement with Plato. Nevertheless, Aristotle is in complete agreement on some topics, even though he criticises Plato – mostly based on a misunderstanding of Plato’s text according to Proclus, as will be seen. Additionally, Aristotle is sometimes in disagreement doctrinally but with a few changes can be made to agree with Plato.

I.3 The Harmony-Doctrine in Proclus

Roughly speaking, there are two types of harmony recognised among the Neoplatonists: (1) between Plato and certain theologians and (2) between Plato and Aristotle. This project of harmonisation was meant, among others, to counteract Christian hostilities and criticisms of pagan disunity.²⁶ Its formulation and expression depend on each Platonist, although we can draw more general distinctions between the schools in Athens and Alexandria, as I show.

I.3.1 The Harmony between Plato and the Theologians

Let us consider the first. Proclus believes in a common theological tradition shared by different thinkers and agreeing with Plato who is portrayed as being ‘most in agreement with the theologians’ (PT 5.16.133.14: τῶν θεολόγων συμφωνότατος).²⁷ An example for this tendency can be found in Proclus’ genealogical explanation of Plato’s thought:

It is necessary to show that every doctrine is in agreement (σύμφωνα) with Plato’s principles (ταῖς Πλατωνικαῖς ἀρχαῖς) and the mystical tradition of the theologians. For the whole of Greek theology is the offspring of Orphic mystagogy since first Pythagoras was taught by Aglaophemus the rites concerning the gods, then secondly Plato received the entire knowledge about these matters from Pythagorean and Orphic writings.

(PT 1.5.25.24–26.4; tr. mine)

Here Proclus maintains that the doctrines extracted from Plato’s dialogues have to be in agreement with his principles and with the thought of the theologians Orpheus, Aglaophemus and Pythagoras. Plato’s thought is presented as derived from the latter. According to Proclus, theology – in its Greek form – goes back entirely to Orpheus, who inspired Pythagoras through Aglaophemus and then Plato. Likewise, in On Providence §1.12–17 he shows that Plato is in accordance with the theologians (i.e., Orpheus and Pythagoras) as well as the Chaldaean Oracles.²⁸ Similarly, in his commentary on the Timaeus (2.173.1–175.9 [1.323.22–325.11]) he emphasises the agreement between Plato and Orpheus.

This type of συμφωνία is also reminiscent of Syrianus’ lost treatise ‘The Harmony of Orpheus, Pythagoras and Plato with the Chaldaean Oracles’ (Συμφωνία Ὀρφέως, Πυθαγόρου, Πλάτωνος πρὸς²⁹ τὰ λόγια) which consisted of ten books.³⁰ This work is attributed by the Suda both to Syrianus (Σ 1662 4.479.1–2) and Proclus (Π 2473 4.210.12–13). The misattribution to Proclus seems to be due to the notes Proclus added to Syrianus’ work.³¹ Regardless of this issue, it is crucial that Proclus holds Syrianus’ book in great esteem (PT 4.23.69.8–15) and follows his lead in further systematising the supposed agreement.³² This is also evidenced by Marinus who mentions Proclus’ effort to harmonise Greek and ‘Barbarian’ theology (VP §22.15–21). Since the fifth century Platonist Hierocles of Alexandria shares their commitment to the harmony of the theologians and Plato (ap. Phot. Bibl. 214.173a13–18) it can be assumed that this tendency goes back to Plutarch of Athens who taught all three.³³

I.3.2 The Harmony between Plato and Aristotle

While Proclus plainly maintains the agreement between Plato and the theologians, he nowhere refers to a general harmony between Plato and Aristotle – unlike many other post-Porphyrean Neoplatonists.³⁴ For instance, Hierocles reports that Ammonius Saccas was the first to ‘bring [Plato and Aristotle] into one and the same mind’ (ap. Phot. Bibl. 251.461a36: συνήγαγεν εἰς ἕνα καὶ τὸν αὐτὸν νοῦν). No explicit evidence of such a position can be found in Proclus, although he had the opportunity to defend it. The possible objection that none of his commentaries on Aristotle survived and, thus, his statements on this issue cannot be accessed is incorrect and, in fact, deceptive. For Proclus in the surviving works often mentions the doctrinal differences between Plato and Aristotle and rejects Aristotle’s criticism of Plato. Additionally, his critical position had been also noted by other Neoplatonists. These statements allow us to form a judgement on his views with some precision.

In his stance Proclus is similar to his teacher Syrianus.³⁵ However, Plutarch’s³⁶ other famous pupil, Hierocles, was committed to this harmony.³⁷ For, after he demonstrates in books 4–5 of On Providence Plato’s agreement with the theological tradition, he then shows in book 6 – in contrast to Syrianus and Proclus – the harmony of Plato and Aristotle (ap. Phot. Bibl. 214.173a5–40, esp. 18–32).³⁸ I thus believe that there is a clear break in the generation succeeding Plutarch with Hierocles, on the one hand, maintaining the fundamental agreement between Plato and Aristotle, and Syrianus and Proclus, on the other hand, rejecting it or, at the very least, shying away from making it a programmatic goal of their exegesis. This break is rarely acknowledged or sometimes even outright denied in scholarship, although it accounts for the differing approaches in Athens and Alexandria.

In what way is Proclus more critical of Aristotle? He assumes – unlike many later Neoplatonists but similar to Syrianus (e.g., In Met. 80.4–81) – that (1) Aristotle intends to criticise what Plato actually meant and not just what Aristotle believes to be a superficial reading of Plato that was brought forward by other interpreters.³⁹ Thus, Aristotle often misunderstands Plato in Proclus’ view. Most importantly (2), Aristotle deviates doctrinally from Plato. In this regard, Aristotle is clearly in disagreement with his teacher. The evidence for (1) is discussed especially in Chapter 3 where I show how Proclus’ engagement with Aristotle’s criticism of Plato’s concept of self-motion deviates from Ps.-Simplicius’ and Philoponus’ (490–570). As proof for (2), I discuss in Chapter 4 how Proclus criticises Aristotle for eliminating the Platonic One and for reducing the intellect’s causality to final causality. What is significant though, is that neither (1) nor (2) prevent a possible rapprochement between Plato and Aristotle. Regarding (1) I show in Chapter 3 how Proclus in fact believes that Plato and Aristotle agree on the nature of self-motion, but Aristotle just misunderstood Plato. Regarding (2) I demonstrate in Chapter 4 that Proclus actually shows how Aristotle’s premises force him to accept the intellect’s efficient causality – although Aristotle actually did not draw this conclusion. However, this rapprochement has its limits: it is not possible in regard to Aristotle’s ontological hierarchy.

Proclus provides a reason for some of Aristotle’s mistakes and departures from Plato: he kept away from theology and focused too much on natural philosophy (In Tim. 2.133.3–4 [1.295.25–6]: τῶν μὲν θεολογικῶν ἀρχῶν ἀφιστάμενος, τοῖς δὲ φυσικοῖς λόγοις πέρα τοῦ δέοντος ἐνδιατρίβων).⁴⁰ Due to his lack of insight – or interest – in theology, his natural philosophy is also compromised, as Proclus makes clear in a well-known passage from his proem in his commentary on the Timaeus.⁴¹ There, Proclus characterises Aristotle as an emulator of Plato, showing why Aristotle falls behind his master. Two aspects in this critique are relevant for my current purposes: (1) Aristotle’s physical works are an imitation of Plato’s; (2) Aristotle spent too much time studying the physical realm and focusing on matter. Proclus’ interpretation of Aristotle contains representative elements of the Neoplatonist reception of Aristotle, although its tone is more critical.

Let us look at (1):

It seems to me that the incredible (δαιμόνιος) Aristotle was also emulating (ζηλώσας) Plato’s teaching to the best of his ability when he arranged his whole treatment of physics like this. He saw there were common factors in all things that have come to exist by nature: form, substrate, the original source of motion, motion, time and place – things which Plato too has taught about here, [talking of] distance, time as image of eternity coexisting with the heavens, the various types of motion, and the auxiliary causes (συναίτια) of natural things – and that other things were peculiar to things divided in substance.

(1.9.14–10.1 [1.6.21–30])

It must be noted that Aristotle receives the epithet daimonios (δαιμόνιος) which marks his inferior status towards the ‘divine’ (θεῖος) Plato.⁴² Aristotle is then portrayed as an imitator or rival (ζηλώσας) of Plato who tried to emulate his teacher as much as possible. This expression accentuates the condescending tone of the passage towards Aristotle and is not used as a neutral term here, as has been assumed.⁴³ According to Proclus, Aristotle is concerned in his Physics with the same matters as Plato in his Timaeus where we already find a complete exposition of the natural world. Proclus lists several topics which roughly correspond to the first four books of the Physics (9.16–18 [6.24–6]). This strategy of backdating, whereby philosophical insights of a successor of Plato are attributed to him, is quite common among the Neoplatonists.⁴⁴

Proclus continues (2):

The first of these were what belonged to the heaven (τὰ τῷ οὐρανῷ προσήκοντα) – in agreement (συμφώνως) with Plato insofar as he made the heaven ungenerated and composed of the fifth essence; for what is the difference between calling it a fifth element and calling it a fifth cosmos and a fifth shape as Plato did? The second were what was common to all the realm of coming to be, an area where one can admire Plato for the great detail in which he studied both their real natures and their properties, correctly preserving both their harmony and their polarities. As for what concerns coming to be, part belongs to things in the skies, whose principles Plato has accounted for, while Aristotle has extended their teaching beyond what was called for; but part extends to the study of animals, something which Plato has given a detailed explanation of with regard to all their causes (κατὰ πάσας τὰς αἰτίας διήρθρωται), including the final causes and the auxiliary causes, while in Aristotle’s work they have only with difficulty and in a few cases (μόγις καὶ ἐν ὀλίγοις) been studied in relation to form (εἶδος).

(1.10.1–16 [1.6.30–7.13])

Proclus divides the study of the physical realm between the eternal celestial beings (10.1–2 [6.30–1]) and the sublunary realm (10.5–6 [7.2–3]). Regarding the former, he goes on to minimise the difference between Plato and Aristotle concerning the cosmos’ eternity and the fifth element, which is simply identified by Proclus with Plato’s fifth body (10.2–3 [6.30–2]). Proclus here omits mentioning that Aristotle takes Tim. 28b7 literally and criticises Plato in DC 1.10–12 for his view that the cosmos is generated, although he is well aware of Aristotle’s objection. This harmonising approach towards Aristotle is an exception in this otherwise disparaging text. Indeed, if we look at later passages which deal with the two issues more extensively Proclus’ more critical views become manifest.⁴⁵ The passage does not, as Hadot (2015: 124) states, ‘culminate’ in this assimilation of Aristotle but rather in the criticism of his account of causality a few lines further down.

The sublunary realm again is divided in two parts. One concerns the skies (7.8) where Proclus, in reference to Aristotle’s more specialist works like Meteor., states that Aristotle ‘has extended the teaching beyond what was called for’ (10.12 [7.9]), a kind of ‘pseudo-scientific pedantry’. The other part deals with zoology (10.12–13 [7.10]). Plato excels here as well by providing a complete causal explanation, including the final cause,⁴⁶ whereas Aristotle treats this topic deficiently and barely in reference to the formal cause (10.15–16 [7.12–13]). The reference here is to enmattered forms since eidos (εἶδος) is used by Proclus in contrast to the separate paradeigma (παράδειγμα) which Aristotle does not recognise.

Proclus concludes that ‘in most cases [Aristotle] stops at the point of matter, and by pinning his explanations of physical things on this he demonstrates to us just how far he falls short of the teaching of his master’ (1.10.16–18 [1.7.13–16]). Plato’s metaphysical and theological outlook on nature is contrasted with Aristotle’s method of doing natural philosophy. Plato seeks the divine and transcendent cause(s) of nature (efficient, paradigmatic and final), whereas Aristotle starts from the sensible things and focuses on the auxiliary causes of matter and form.⁴⁷ In this way, however, Aristotle’s natural philosophy remains deficient and requires a substantial reformation. In my opinion Gerson (2005) is again too optimistic in claiming that Proclus ‘incidentally provides the rationale for the harmony between the two. So long as an Aristotelian realizes that physical science cannot be explanatorily exhaustive, its ambit is secure’ (111). An Aristotelian would need to recognise first of all the misguided conception of causality which is intrinsic to Aristotle’s natural philosophy.

Simplicius, who is primarily associated with Alexandria but studied also in Athens, seems to offer an implicit refutation of Proclus’ views on natural philosophy in his introduction to his commentary on the Physics by portraying Aristotle’s achievements quite differently (6.31–8.15).⁴⁸ This ultimately culminates in his claim that ‘Aristotle surpassed (διήνεγκεν) both Plato and all those before Plato alike’ (7.27–8; tr. Menn) in the study of natural philosophy. Simplicius thus clearly differs from Proclus’ views on Aristotle’s physics and generally attributes a much more positive role to him. Elsewhere Simplicius also acknowledge Aristotle’s focus on physics but – crucially – without portraying it as a negative characteristic:

[Aristotle] always refuses to deviate from nature; on the contrary, he considers even things which are above nature according to their relation to nature, just as, by contrast, the divine Plato, according to Pythagorean usage, examines even natural things insofar as they participate in the things above nature.

(In Cat. 6.27–30; tr. Chase)

Simplicius here describes two different methodologies without making a value judgement as Proclus does. For him both are clearly compatible and even in agreement (see In Phys. 1359.5–8). Plato and Aristotle therefore differ only in approach and the language they use: the conflict is over words (onomata/ὀνόματα) not reality (pragmata/πράγματα), as Simplicius often maintains.⁴⁹ Similarly, David/Elias claims that ‘Aristotle always when he does theology engages in the study of nature (θεολογῶν φυσιολογεῖ), just as Plato always when he engages in the study of nature does theology (φυσιολογῶν θεολογεῖ), introducing everywhere the doctrine of the forms’ (In Cat. 124.21–3; tr. mine).⁵⁰

Proclus thus differs from other Neoplatonists in his reading of Aristotle, as he maintains there is a disagreement over πράγματα and not just ὀνόματα.⁵¹ In fact, Proclus’ tendency is already remarked upon by Simplicius and by Philoponus, who was also active in Alexandria. The former states that

Alexander of Aphrodisias does not understand Plato’s doctrines as Aristotle understood them, nor does he accept that their views are in agreement, but having from the outset, so it seems, treated Plato’s views as suspect (ὑπόπτως), just as shortly before our time some people (ὀλίγον πρὸ ἡμῶν τινες) [did with] Aristotle’s.

(In DC 297.1–5; tr. Hankinson)

I take the reference ὀλίγον πρὸ ἡμῶν τινες to imply Proclus, as Steel (2016: 329) has conclusively shown. In another passage from the same commentary (640.21–32), Simplicius alludes to Proclus’ refutation of Aristotle’s objections to the Timaeus, before referring again to his own harmonistic views. Clearly, this adjacent exposition of the harmony-doctrine is meant to contrast with Proclus’ approach to Aristotle. In general, Proclus and Simplicius have different approaches to Aristotle and the wider ‘wisdom tradition’.⁵² In consequence, Simplicius often wants to correct Proclus’ view on these issues. This emerges clearly when he states :

But since the Lycian philosopher, [Proclus], says that this opinion about motion is the one and only disagreement between Aristotle and Plato, the former stating that there is no change beyond things and refuting the view that motion is a genus, the latter that motion is a single genus of being as are existence and identity and otherness, it would be more seemly to demonstrate agreement in the apparent disagreement (τὴν ἐν τῇ δοκούσῃ διαφωνίᾳ συμφωνίαν) if at all possible.

(In Phys. 404.16–22; tr. Urmson)

Likewise, Proclus’ attitude did not escape Philoponus: ‘[t]hus even Proclus himself has explicitly conceded the disagreement (διαφωνίαν) between the [two] philosophers, or rather, demonstrated it from Aristotle’s own [writings]. This being so, one might well be amazed at the gross effrontery of those who have tried to show that Aristotle and Plato are in agreement even on this point [i.e., theory of forms]’ (De aet. 32.8–13; tr. Share). In consequence, Proclus is not included in the group of exegetes which Philoponus describes here and elsewhere as being too harmonistic in their approach to Aristotle.⁵³ Philoponus probably targets his teacher Ammonius son of Hermias (435/445–517/526) and his other pupils where we encounter the tendency described by him.⁵⁴ It is noteworthy that Philoponus himself had changed his stance on the harmony between Plato and Aristotle.⁵⁵

Since Proclus’ anti-harmonist stance clearly differed from Ammonius’ and Simplicius’ views, certain trends can be distinguished between the Athenian (Syrianus, Proclus) and Alexandrian schools (Hierocles, Ammonius, Simplicius, early Philoponus).⁵⁶ Although this has been questioned by Hadot (2015), there remain strong reasons for following this traditional interpretation which was first brought forward by Praechter (1909; 1910) and is nowadays supported by D’Ancona (2015) and Steel (2016).⁵⁷ This last group of scholars maintains that there is a fundamental difference in the approach to and appreciation of Aristotle between the schools of Athens and Alexandria. Most probably this difference is rooted in divergent philosophical convictions. After Ammonius, the school in Alexandria abandoned the study of the Parmenides as a theological text and simplified its metaphysical system (which presumably culminated in the intellect and not the One, as was usual among their Athenian contemporaries as well as earlier Neoplatonists).⁵⁸ Connected to this is a stronger focus on Aristotle. This accounts for the difference between Proclus on the one hand and other Neoplatonists associated with or inspired by the Alexandrian school on the other.

I.4 Motion in Proclus and the Structure of the Book

Proclus brings together – consciously or unconsciously – Platonic and Aristotelian views on motion. However, his account of motion differs significantly from Aristotle. In order to make sense of Proclus’ position on motion, one needs to be aware of a fundamental distinction in the Neoplatonist and, particularly, Proclean concept of kinēsis (κίνησις). Unlike Aristotle who offers us a definition of motion as the ‘actuality of what is potentially, as such’ (Phys. 3.1.201a11), Neoplatonists like Proclus do not have one unifying definition of motion.⁵⁹ Instead, starting with Plotinus, one can fundamentally differentiate between (1) non-physical and (2) physical motion, that is, motion related to the incorporeal and non-spatial intelligible realm and motion pertaining to physical objects bound by space and time.⁶⁰ In Plotinus ‘motion does not have the same definition when it is related to the sensible world, to the soul, or to the Forms and intellect’, as noted by Michalewski (2020: 55). This dichotomy is partly grounded in and achieved through an exegesis of Plato⁶¹ and Aristotle whose agreement on the nature of motion remained a matter of debate in late antiquity.⁶² It is ultimately guided by the Platonic motivation to trace back sensible qualities to their intelligible paradigm. In this way, all types of motion are ultimately grounded in intelligible motion.⁶³

Non-physical motion is then divided – in Proclus at least – into intelligible (1.1), intellectual (1.2), and psychic motion (1.3). In each case motion refers either to the μέγιστον γένος (‘highest kind’) (1.1), or to the atemporal contemplation of the intellect (1.2), or to soul’s activity per se, living, and its other activities such as discursive thinking, willing etc. (1.3). These non-physical types of motions are based on an exegesis of certain passages in Plato, especially the Sophist and Laws 10.⁶⁴ Next to these three types, there is another, more fundamental type of metaphysical motion which refers to the process of causation and the relation between cause and effect (1.4). I call this causal motion. This type of motion seems to be, for the most part, an innovation of Neoplatonism.⁶⁵

A note on the terminology. In the following, I render motion that does not pertain to the sensible realm as ‘non-physical’ and not ‘spiritual’, although the latter term is more common in scholarship (e.g., Opsomer 2009) which follows Gersh’s seminal work on the subject, Κίνησις Ἀκίνητος: A Study of Spiritual Motion in the Philosophy of Proclus (1973). The term ’spiritual’ is deceiving since it presupposes a ‘spiritual realm’ to which it refers.⁶⁶ But this sphere is usually rendered in (Neo-)Platonist scholarship as ‘intelligible’ which is a preferable translation of nous (νοῦς), noētos (νοητός) and their derivates. However, since ‘intelligible’ and ‘noetic’ in Proclus characterise only a specific aspect of the intelligible realm, as Gersh (1973: 1) correctly remarks, and since the motion of soul should be also included, this term is best avoided. Therefore, I choose to use the broader term of ‘non-physical motion’.

Thus, depending on the level of reality motion has a different meaning. In its true sense motion is intelligible since it is a paradigm for all the other types of motion – intellectual, psychic or physical – which it causes. Physical motion is thus only an image of intelligible motion. Since the relationship of intelligible and sensible motion is one of paradigm and image, as well as cause and effect, motion is predicated of them homonymously, not synonymously. This is in line with the tendency among late Neoplatonists to regard the relation of form and particular as homonymous due to their essential differences such as forms being eternal and particulars perishable. They distinguish between different types of homonymy, one of them being the homonymy of paradigm and image, as can be seen in Syrianus, In Met. 114.35–115.3.⁶⁷ Thus, non-sensible and sensible motion differ significantly, as is made clear by Syrianus: ‘for there is motion among incorporeal entities as well as shape and size, but they are not the same as in the sensible realm’ (In Met. 95.26–8: ἔστι γὰρ καὶ κίνησις ἐν ἀσωμάτοις καὶ σχῆμα καὶ μέγεθος, οὐ τοιαῦτα δὲ οἷα ἐν τοῖς αἰσθητοῖς).⁶⁸

Physical motion is quite similar to the Aristotelian understanding. In contrast, non-physical motion differs drastically from the former, as it does not describe a dynamic process in space and time but rather the activities and the causal relationship of non-physical and intelligible entities. Thus, on the one hand it refers to the soul’s and intellect’s activities such as thinking, willing etc. as motions. Most importantly, it denotes the act of soul’s self-causation, as will become clear in Chapter 3. And on the other, intelligible motion also describes on a higher metaphysical level the causal relationship between the One, intellect and soul which the Neoplatonists outlined with the dynamic triad monē (μονή) – proodos (προόδος) – epistrophē (ἐπιστροφή).⁶⁹ While this concept of non-physical motion might strike the modern reader as odd – indeed, even in antiquity this seemed to be the case –⁷⁰ it proved to be very influential for the further history of philosophy, as it is particularly relevant for the discussion of motion in Proclus and then found its way into medieval and Renaissance philosophy. The two different senses of motion create a paradoxical situation since from a physical perspective the intelligible realm is completely unmoved. Yet, in an intelligible sense, when referring to thinking or causation, non-physical entities can be described as being in motion.

From this condensed overview it is evident that concepts of motion differ drastically between Neoplatonists and Aristotle. While the former emphasise its autonomous existence as form-like genus, which manifests itself in the physical realm, the latter seems even to struggle to define motion as something real and actual.⁷¹

This book deals with different types of motion. Chapter 1 focuses on physical motion and Proclus’ discussion in the Elements of Physics. Chapter 2 asks about the origin of motion in the cosmos (including physical motion) and shows how Proclus combines Plato’s and Aristotle’s account on this issue. Chapter 3 focuses on the motion of soul. Chapter 4 deals with Proclus’ critique of the causality of Aristotle’s prime mover which he regards as an efficient cause and not just as a final one. The structure aims to show in an increasing order Proclus’ distance from Aristotle: Chapter 1 shows Proclus’ proximity to Aristotle, while Chapter 4 presents Proclus at his most critical. In the first chapter, I show how in the Elements of Physics Proclus largely endorses Aristotelian kinematics and leaves out more controversial issues. The second chapter focuses on Proclus’ adoption of the intellect as prime unmoved mover which he portrays as Platonic. Nevertheless, Proclus makes significant use of Aristotelian vocabulary and arguments. In the third chapter I demonstrate how Proclus rejects Aristotle’s criticism of Plato’s concept of self-motion, while emphasising that Proclus makes productive use of Aristotle’s objections. In the final chapter, I show that, according to Proclus, Plato and Aristotle do not agree on the nature of the highest principle and on the causality of the intellect.