In this book on post-Chalcedonian theology in the East, Johannes Zachhuber goes beyond the pioneering work of Cardinal Grillmeier and his editorial team, led by Theresia Hainthaler, to be found in the several parts of volume ii of Christ in Christian tradition (4 parts so far, 1987–2013, in the English translation), which opened up the world of post-Chalcedonian Christology. The monumental work of Grillmeier and Hainthaler (increasingly the latter as the volumes continued after the cardinal's death in 1994) was organised geographically, volumes ii–iv dealing with the three principal Eastern patriarchates – Constantinople, Antioch and Alexandria (volume v will deal with Rome and the West) – perhaps somewhat obscuring a debate about Chalcedon, the course of which was not determined by geography. The great theologians, and some lesser folk, are given careful attention, but the arrangement makes it difficult to trace the course of the debate (not altogether a disadvantage, as there was no linear development). Zachhuber's book is quite different: it traces a particular debate – about the development of the technical terminology that had been introduced (almost unwittingly) by Chalcedon in its Christological settlement: no ‘settlement’, but rather the cause of a fundamental division in the Christian Church which still exists after more than a millennium and a half. In speaking of Christ as uniting two natures in one person/hypostasis, the council drew on the distinction between nature/essence and person, physis/ousia and hypostasis, that had been used by Basil and Gregory of Nyssa to articulate the doctrine of the Trinity, in which three hypostaseis were united in a single physis/ousia. By introducing a Trinitarian distinction into Christology, Chalcedon took a distinction that had been used in one way (using ousia to express the unity of the Godhead) to express almost the opposite (so that it was now hypostasis that expressed the unity of Christ): a point already recognised by Gregory of Nazianzus (in non-technical language: ep. ci). Furthermore, this move could be seen as taking terminology fashioned in a discussion concerned with theology, theologia, into what was understood by many to be a quite separate realm, that of oikonomia, the ‘economy’, that is, God's dealings with the created order, pre-eminently the incarnation – or, if you like, confusing the realms of theologia and oikonomia.

Zachhuber presents his discussion by beginning, in part i, with the development of the philosophical terminology used to express, first of all, the doctrine of the Trinity in the wake of Nicaea, which had expressed the unity of the Trinity (or the Father and the Son) with the term homoousios, ‘of one essence’ (not further defined) – beginning and ending with the Alexandrian theologians, Athanasius and Cyril, with most attention paid to the Cappadocian Fathers (with clear acknowledgment of their differences). Zachhuber, rightly, pays attention to the detail of the texts, which means that this reviewer has to say that you need to read the book, as it is the detail that is most important. There follows part ii, concerned with the dominant theology in the wake of Chalcedon, namely those who rejected it, whom the Orthodox called ‘monophysite’, because of their insistence on the ‘one nature/mia physis’ formula (‘one Incarnate nature of God the Word’) to express the reality of Christ, a formula of which Cyril seems to have been increasingly fond, but for the same reasons called increasingly by modern scholars, including Zachhuber, ‘miaphysites’ (a barbarous Greek construction, which could be alleviated by the addition of a hyphen: viz., mia-physites). Only very gradually did the ascendancy of mia-physite theology yield to supporters of Chalcedon, and even so it can be argued that theological agenda continued to be determined by the mia-physites, such as Severus of Antioch, even long after their death. Part ii, then, deals with Severus, John Philoponus and the mia-physite anti-tritheists, Damian of Alexandria and Peter of Callinicus (opposing the so-called tritheism into which John Philoponus had fallen). Part iii deals with Chalcedonian reaction in John the Grammarian and Leontius of Byzantium, and their successors in the late sixth or even seventh century, Pamphilus, Theodore of Raïthu and Leontius of Jerusalem, before coming to the truly great defenders of Chalcedon, Maximus the Confessor and, in the eighth century, John Damascene. Zachhuber guides us carefully through a tangled and, in many respects, obscure story. Obscure for two reasons: much of the debate was of little interest to the later Byzantine Church as it concerned the ‘heretical monophysites’; consequently though Severus, John Philoponus, Damian of Alexandria and Peter of Callinicus all wrote in Greek (though Peter knew Syriac and other works of his survive in that language), their works survive in Syriac translation, which entails the necessary indirection of reading them, and in particular trying to discern their innovative use of philosophical Greek, through the veil of translation. Even with the Chalcedonian theologians, much survives in fragmentary form (and at least twice, Zachhuber finds himself dealing with recently discovered, and therefore little discussed, treatises). So there are two fundamental problems in interpreting all this: having to rely on Syriac translations of an originally Greek debate, combined with the need to rely on often fragmentary evidence. To some extent this is due to the success in the Byzantine realm of the last two theologians Zachhuber discusses: Maximus the Confessor and John Damascene. For although they were influenced by the sixth- and early seventh-century discussion, so ably illuminated by Zachhuber, they largely bypassed the detail of the discussion, reaching back to make a more robust defence of Chalcedon (for all that Maximus is aware of some at least of the theologians discussed, his explicit opponent is generally the long-deceased Severus).

For all the detail, which will be of enduring interest, it seems to me that this book is haunted by two more general themes: the first is there in the title, The rise of Christian theology and the end of ancient metaphysics, suggesting that the debates over theology led to the demise of classical metaphysics and its replacement by something Christian; the second is what I see as the long shadow of the late nineteenth-century German theologian, Loofs's, notion of ‘enhypostasia’, that is, the idea that post-Chalcedonian Christology introduced a fundamentally new idea that in the Incarnation the Word of God ‘enhypostatized’ the human nature of Christ, a notion (of which I am never entirely clear) that the Word of God either absorbed the human hypostasis into itself, or (more likely, I think) provided the hypostasis for the incipient human nature – a process known as (en-)hypostatisation.

Let us start with Loofs's long shadow, which turns on the use in the sixth century of the adjective, enypostatos, by defenders of Chalcedon against the Monophysite charge that, if Christ had only one hypostasis, then the human nature of Christ is anypostatos, that is, non-existent: in other words, the Christology of the council is docetic – Christ only appears to be human. The Chalcedonian response, from John the Grammarian onwards, was that, on the contrary, the human nature of Christ is enypostatos, the en- prefix being used, as in other words, to affirm what is denied by the alpha privative (an- before a vowel). That was not how Loofs took the adjective enypostatos, for him en- had locative significance, that is, the human nature had its hypostasis ‘in’ the Word. The error of such a derivation was pointed out by Brian Daley in a paper (still unpublished, though circulating as samizdat), given at the patristic conference in Oxford in 1979. Zachhuber accepts Daley's interpretation, but maintains, as do other scholars, that later on enypostatos acquired the meaning of ‘subsisting in’. This seems to me unnecessary; what happens rather is that one of the ways in which nature can have real, ‘concrete’ existence is by existing ‘in’ something else that really exists, that is, a hypostasis. However, the danger with Loofs's interpretation is that the notion of ‘enhypostatization’ acquires a life of its own: in the Incarnation Christ ‘enhypostatizes’ human nature; some even hold that it makes sense to speak of Christ ultimately ‘enhypostatizing’ the cosmos. There is nothing of that in Zachhuber, but he does speak of ‘hypostatisation’ (for example, in the heading of section 7.1.3: ‘Hypostatization and the notion of insubsistence’). But enypostatos is simply an adjective, describing a condition; it is not a participle, describing a process. There may be a process whereby something acquires a hypostasis, but the use of the mere adjective, enypostatos, is not evidence that there is. So I find myself wondering whether the long shadow of Loofs is not to be detected here (as it can certainly be in much twentieth-century Orthodox theology, where the notion has acquired a strange popularity, made stranger by the fact that the uses to which ‘enhypostatisation’ is put are too various even to be regarded as analogical).

My reference to Orthodox theology might seem wide of the mark in reviewing a book by a Lutheran theologian, but in the very introduction to his book, Zachhuber mentions ‘the claim of Eastern Orthodox thinkers … that Patristic thinkers brought about an ontological revolution while articulating the doctrine of the Trinity in particular’ (p. 5, cf. p. 70). Zachhuber cites Vladimir Lossky and John Zizioulas (the mention of Lossky seems to me mistaken: Lossky was wary of mixing up theology and metaphysics, and on the page cited he is simply arguing for a distinction between Plotinus’ apophaticism, which is down to the essential unrelatedness of the One, and Dionysius’ apophaticism is based on God's radical incomprehensibility, an entailment of creation ex nihilo), and goes on to assert that ‘the revolutionary philosophy is not the fourth-century system …; rather, it was the Christological controversy that led Christian thinkers to the adoption of increasingly innovative intellectual assumptions’ (ibid.). Zizioulas was right, then, only he got the century wrong: not the fourth, but the sixth. Elsewhere the change in metaphysical paradigm is characterised as a move from a substance-accident dualism to an ontology based on the duality of ousia and hypostasis (see p. 237). I suspect that it is still premature to speak of the ‘end of ancient metaphysics’: a substance-accidents ontology does not fade away; the continued importance of Porphyry's Isagoge, both in East and West, would seem evidence to the contrary. The distinction between person and nature, both in Trinitarian theology and Christological thought, opens up a conceptual space which the notion of the individual or the person can occupy (notions which are, however, radically distinguished by Zizioulas, despite their apparent identity in, say, John Damascene).

But the importance of this book lies in the patient teasing out of the debate about seeking to understand the reality of Christ, sparked off by the introduction of a distinction originally made in the realm of theology, in the strict sense, into the realm of what the Greeks, especially, called the oikonomia. In the course of this, Zachhuber – drawing on his careful reading of texts written in a Greek with little grace of style, and often surviving in Syriac translations of varying reliability, if they survive at all, as well as his command of a growing secondary literature, often very demanding in its nature (alas, the index is woefully inadequate) – provides invaluable help in understanding a period of debate in Christian theology, the importance of which has only recently been perceived, as well as raising important questions about what was achieved in refining the conceptual apparatus used to capture what were essentially new ideas.