‘Patristic philosophy’: not too long ago this expression might have left philosophers and theologians alike puzzled as to what it refers to. Z.'s splendid new book takes valiantly forward a recent but fast-growing research programme that investigates the thought of the Christian writers of late antiquity as putting forward a philosophy of their own. The significance of the rise of Patristic philosophy, as distinctive and discontinuous in relation to what preceded it, is that it marks, according to Z., ‘the end of ancient metaphysics’ (p. 9), which gets replaced by ‘a Christian metaphysic, an understanding of being specifically designed to underwrite the tenets of the Church's doctrine’ (p. 16). Z.'s claims are essentially an appeal to direct our philosophical attention to a body of thought, by the early Christian thinkers, that ought to be studied in its own right, and not (primarily) for how it relates to ancient philosophy.

Within this novel research programme Z.'s approach departs from the mainstream: ‘Those scholars who have treated Patristic thought as part of the history of philosophy have usually seen it as one or, at least, as converging towards one unified vision in line with the supposed unity of Christian doctrine emerging during this historical epoch’ (p. 4). By contrast, Z. argues that there is an ever-evolving plurality of philosophical views being developed by early Christian thinkers.

However, within this plurality of which we should not lose sight, there are patterns of development to be discerned. Z. focuses mainly on the pattern that leads from ‘Cappadocian philosophy’ to ‘Chalcedonean philosophy’, namely from the philosophical views originally put forward by the Cappadocians, via the establishment of a ‘classical theory’ version of their views upon which Christian theology raises, to what Z. calls ‘Chalcedonean transformations of the Classical theory’, which ultimately result in ‘Chalcedonean philosophy’.

Z. expertly guides us through this ‘pattern’ with an impressive mastery of the material, lucidity of thought and clarity of exposition. Following the pattern Z. traces across centuries and varieties of Christian thinkers is extremely fascinating – Z. draws our attention to several thinkers who are by no means widely known and guides us through understanding their key ideas and texts in a way that is enriching and stimulating.

Within the limits of this review, I will concentrate mainly on the starting point of Z.'s extraordinary intellectual feat, that is, his interpretation of what he calls ‘Cappadocian philosophy’. What is distinctive of Z.'s interpretation is not only its systematicity (according to him the Cappadocians’ philosophy is the result of an ‘organic’ and quite ‘harmonious’ development of ideas from Basil to Gregory of Nyssa via Gregory of Nazianzus), but its approach, according to which ‘[t]he Cappadocian theory is presented in the writings of these thinkers in two versions, which will here be called abstract and concrete’ (p. 10) – a ‘duality of perspectives’: ‘grammatical and physical or logical and metaphysical’ respectively (p. 66). What are these two versions? Z. writes

Z. calls this account ‘abstract’ because ‘[t]he “particular” is here described by means of its individual property (ἰδίωμα), while the universal is expressed through a common formula (λόγος)’ (p. 40, my emphasis). That is to say, it is an account ‘with epistemic concerns at its heart’ (p. 41). Z. presents Basil as holding that ‘As much as the unity of ousia is expressed by shared predicates, the individual distinction of the hypostasis … has its corresponding mark, the individual property’ (p. 35, my emphasis); so, if the concern is not ontological, we should assume that the unity (i.e. oneness) of nature among the Persons of the Trinity is not explained but only described by their shared predicates. Yet, from the perspective of Patristic philosophy, Z. argues, ‘the … element [of this abstract account] that is the most intriguing [is] the analogy between ousia and hypostasis in the Trinity and the relationship between the common item (τὸ κοίνον) and the particular (τὸ ἴδιον)’, i.e. ‘between universal and particular created being’ (p. 38). This seems to be an ontological claim. Z. comments that here ‘we get a first glimpse of the momentous project that I call Cappadocian philosophy’ (p. 40). But how are we to understand the philosophically significant idea introduced with Basil's analogy?

In explicating the relation between the ‘common item’ and ‘the particular’ as a relation between ‘universal and particular created being’, Z. appears to assume that according to the Cappadocian abstract account, divinity is instantiated in the Trinity in several ways; divinity is an (immanent) universal of which the three Persons of the Trinity are instances (like Peter, Paul and Mark are instances of the universal human being). I see a difficulty here between particularity and differentiation. A simple way to present the difficulty might be this: my desk has different properties on the left side than on the right; but it is a single desk that possesses different properties. My question is: what explains that the Trinity is not a single particular entity, possessing all the particular properties of the Trinity, just as my desk is a single item and possesses the properties of its right and left sides? What distinguishes the Trinity from an example such as the desk? How is the Trinity three concrete Persons while also being one, ‘not in terms of the abstract unity of a common formula of being, but as real, concrete being’ (p. 57) with varying particular properties? Why and how is the ousia of divinity instantiated three times in the Trinity and not only once? What is needed, over and above the theory of particularity, is a theory of the individuality of the Persons, which their common ousia cannot give them.

There is an obvious ontological difference between the Trinity and physical objects, namely, the Persons of the Trinity are not physical and enmattered – they are constituted of the common properties and the particular properties, making up a bundle of properties each. Z. explains: ‘Note that the latter [the individual properties] are, per se, universal too. They are particular only in the sense that only some individuals of a class possess them’ (p. 313). The account tells us that the particular properties ground the instantiation of the Persons in the Trinity, and that these properties are universal, too, rather than physical matter, but it does not explain why this entails multiple instantiation rather than multiple qualification of a single divinity. What is therefore needed from the Cappadocian abstract account is a fuller explanation of the multiple instantiation of the ousia of divinity. If this could be given, their philosophical project would be built on firmer ground than what it appears.

Gregory of Nyssa, according to Z., gives the concrete version of the Cappadocian theory, thus: ‘The relationship between universal being and its instantiations can be described in terms of a whole (ὅλον, πᾶν, τὰ πάντα, πλήρωμα) and its constituent parts’ (p. 58). The whole is one, as Z. presents Gregory's view,

But now ousia has its instances as its effects, which are parts of it because originally ‘contained’ in it (in the sense in which a cause is said to contain its effects). While I cannot explore things further here, I want to argue that the Cappadocian ‘abstract’ and ‘concrete’ accounts thus described appear to be both metaphysically committed and offer two different metaphysical views, rather than a ‘duality of perspectives’ (p. 66) on the same view. How to think of their relation is a challenge that cannot be addressed here.

Z.'s deeply philosophical book will be of enduring significance for historians of philosophy and theologians alike as well as scholars interested in the historical period from the perspectives of classical studies and ancient history.