The book under review is the latest issue of the series Ancient Commentators on Aristotle, directed by R. Sorabji and M. Griffin. The volume contains an annotated translation of John Philoponus’ commentary on chapters 6–15 of Aristotle's Categories. The first part of Philoponus’ commentary (on chapters 1–5) has been edited in a previous issue of the same series (R. Sirkel, M. Tweedale, J. Harris, D. King [trans.], Philoponus: On Aristotle Categories 1–5 with Philoponus: a Treatise Concerning the Whole and the Parts [2015]). Within the Ancient Commentators on Aristotle series other commentaries by Philoponus have already been published, namely those dedicated to Aristotle's Physics, On Coming to Be and Perishing, On the Soul, Meteorology and Posterior Analytics. Finally, texts in the series regarding Aristotle's Categories include the commentaries composed by Ammonius, Dexippus, Porphyry and Simplicius.

Some introductory remarks may be useful in order to contextualise the theme in question and its premises. Philoponus’ writing is placed within the context of late antique Neoplatonism, which dedicated significant attention to the Categories, as the commentaries that are preserved demonstrate. ‘The extant ancient commentaries on the Categories, apart from those of Ammonius and Philoponus himself, are Porphyry's brief question and answer commentary and those of Dexippus, Boethius, Simplicius, Olympiodorus, and David’ (p. 8). The Categories, and more generally the Organon, were among the first works of Aristotle discussed by the Platonic tradition after the rediscovery of the esoteric writings of the Stagirite in the first century bce. In the early Imperial age Aristotelian logic was considered in a critical way by Platonic authors, but in later centuries there was a gradual deepening and appreciation of Aristotle's works, which were progressively integrated in the Neoplatonic curriculum of studies. During the spreading process of Aristotelian philosophy between the second and the third centuries ce a key role was played by Alexander of Aphrodisias: though an Aristotelian commenting on the works of the Stagirite, he also exercised a notable influence in the Neoplatonic schools. Alexander considered it necessary to integrate the logic of Aristotle into his metaphysics and argued that the ontological priority of the form was affirmed by Aristotle not only in metaphysics but above all in logic (see Metaph. 4). Among the Neoplatonists Porphyry was the first philosopher who consistently harmonised Platonism and Aristotelianism, especially in his Isagoge, with regard to logic, which had an introductory function with respect to the study of the other sciences, especially physics and metaphysics. During this process of reception of Aristotelian logic in the Neoplatonic schools, in late antiquity a crucial role was played by Ammonius and his successor Philoponus, who were leaders of the School of Alexandria. Philoponus is of particular interest because he was Christian and, as such, he not only received aspects of Aristotle's thought in his Neoplatonic background, but he also sought to harmonise classical philosophy with his Christian faith.

Philoponus’ commentary on the Categories is based on an anonymous record of the seminars conducted by Ammonius on Aristotle's treatise. In fact, while some of Philoponus’ commentaries on Aristotle are notes from the lectures given by his master, in this case there is an (anonymous) intermediary between Ammonius and Philoponus. Whereas the previous issue of the series presents Philoponus’ commentary on the first five chapters of the Categories, with special attention to the notion of substance, the present volume tackles, in order, the categories of quantity, relatives, qualified/quality, acting and be-affected (the reference to the categories of rest, where and when is negligible). Within this context Philoponus highlights the theme of opposites, the concepts of priority, simultaneity, motion and the category of having. As the text shows, in logical terms Aristotle considers the being in itself with regard to the ten categories, namely the predicates of being. The category of substance is the one to which all other categories refer, as to their unitary substratum. Substance is then the category of which all other accidents are predicated or in which they inhere. In physics, then, for Aristotle the substance is the concrete subject, a sensible being subject to generation and to corruption. The individual substance, therefore, is the object of natural science, and it is the only one to possess the true essence, while species and genera are secondary substances. Commenting on the Aristotelian sentences, in the first place Philoponus debates with his master Ammonius, at times agreeing with his arguments, at times refuting them. In the second place Philoponus interprets Aristotle through his own Neoplatonic mind, partially correcting also the theses of Aristotle.

S. explores in detail the points of contact between the commentary of Ammonius – as it is transmitted in an indirect way – and that of Philoponus. In light of a previous work by C. Luna (Commentaire sur les Catégories d'Aristote [2001]), S. provides a broad comparison between the two texts, pointing out their affinities and differences. Along with a detailed philological analysis, the introduction highlights the aspects of originality contained in Philoponus’ commentary. Of particular interest is the reflection on the (physical) concept of motion, which has also logical implications and of which Aristotle identified six species: generation, destruction, increase, diminution, qualitative change, change of place (Cat. 15a13–14). Clarifying and completing the argument of Ammonius, Philoponus introduces a different classification of the species of motion, considering the change of place – or locomotion – as divided into rectilinear motion and rotation. In this regard, with reference to the Physics, Philoponus argues that generation and destruction are not motions: for ‘in the Categories, he says, Aristotle is talking as a logician and to beginners rather than as a natural scientist’ (p. 7). Logic, therefore, is used in an instrumental and propaedeutic way with respect to physics as well as the other sciences, and this very intention is attributed to Aristotle himself. This text, as S. observes (see p. 14), also occurs in Simplicius (427, 11–28). In continuity with Simplicius, commenting on Cat. 14a19–20, according to which all contraries must either be in the same genus or in contrary genera or be genera themselves, Philoponus discusses the nature of good and bad as genera. Whereas Aristotle claims that some contraries, such as good and bad, are not in a genus but they themselves are genera, Philoponus maintains that good and bad are not contraries at all, but they are opposed as possession and privation. Therefore, whereas each of a pair of contraries must have a defined nature, the bad does not, because it is a kind of disproportion, and disproportion does not have a definite form. As a Platonist, Philoponus affirms that the bad is just a privation, and the absence of possession has no definitive nature itself (p. 123).

The volume has the merit of rendering accessible to the modern reader a Greek text that, until now, was not available in translation. Along with the departures from A. Busse's edition, the book offers some useful tools to the reader: an English–Greek glossary, a Greek–English index and a subject index. The rich apparatus of notes elucidates some of the semantic choices of the author and, above all, addresses the nodal aspects of the commentary of Philoponus from a philological point of view. The observations proposed in the notes are, in part, anticipated in the introduction, which provides an outline of the parallels between Philoponus and Ammonius, Porphyry, Simplicius, Olympiodorus, David and, more generally, other interpreters of the Aristotelian Categories. In this way, S. effectively reconstructs the motifs of continuity and debt in Philoponus with respect to the Neoplatonic tradition, contextualising Philoponus’ commentary on the Categories in the complex process of recovery of logic and the philosophy of Aristotle that began in the late Hellenistic age.