This book is a revision of Ip's Cambridge dissertation, which was overseen by Rowan Williams, the author of the book's foreword. It nuances the doctrine of divine simplicity for modern systematic and philosophical theology, where simplicity is often understood in pro-Nicene/Augustinian or Aristotelian-Thomistic terms, by elucidating its historical development from Plato's Republic through Origen. The two chief insights of this historical study are, first, that divine simplicity came to be formed and accepted in Christian theological discourse as a doctrine with ethical as well as metaphysical significance, and, second, that while modern commentators have seen the doctrine as inevitably leading to modalism, its historical development was in fact in opposition to the analogous third-century theology, Monarchianism.
This book's seven chapters have a tripartite structure, covering the philosophical background of divine simplicity (chapters 1–2), simplicity and trinitarian theology (here specifically, ‘the nature of the Father-Son relation’ rather than ‘“fully Trinitarian” theologies’ [p.49]) before Origen (chapters 3–4) and finally, Origen's theology (chapters 5–7). Chapter 1 is a narrow but able discussion of simplicity in Plato, focusing on the locus classicus of divine simplicity in Plato's corpus, which Ip maintains is Republic 380d–383c, and 475e–480a. These passages provide the building blocks for the development of divine simplicity insofar as they present simplicity as an ethical category entailing divine self-consistency (including especially the lack of qualities such as deceitfulness that would contradict the goodness of a god), use that principle to regulate theological discourse, and (in 475e–480a) describe a metaphysical first principle, the Good.
In chapter 2, Ip demonstrates that Philo uses simplicity as does Plato in the Republic: to regulate theological discourse and scriptural exegesis. First, however, Ip narrates the marriage of divine simplicity and the notion of a metaphysical first principle in Alcinous. According to Ip, the latter's Didaskalikos 10 expands the implications of Republic 380e–381e (which Ip suggests informs Didaskalikos 10.7), by means of other Platonic passages (Parmenides’ first hypothesis; Phaedrus 78b–81a), resulting in a first principle that is partless, incomposite, immutable, motionless and incorporeal. Crucially, this step provides the basis for the ensuing narration to treat simplicity in terms of its logical correlates, including indivisibility and ideas less obviously synonymous, including incorporeality and immutability, rather than reducing the doctrine to the notion of pure partlessness.
Chapter 3 demonstrates that Irenaeus uses simplicity and its correlates (here, inseparability/indivisibility, consubstantiality and contemporality) to critique the Valentinian account of divine generation as emission or projection. In so doing, Ip demonstrates that simplicity functions in the emergence of trinitarian theology as it does in Plato and Philo: as a rule of theological grammar. Chapter 4 introduces Monarchianism and complicates modern claims that simplicity logically entails modalism by demonstrating that Monarchianism emerged as the solution to prosopological exegesis, an issue distinct from the metaphysical concerns of divine simplicity and its function in regulating theological grammar. Moreover, Ip maintains that in Tertullian we find an account of the generation of the Son from the Father that both avoids Monarchianism and Valentinian emission theology while also being compatible with simplicity. These points demonstrate that historically, Monarchianism and simplicity do not go hand in hand.
After chapter 5 defines Origen's doctrine of simplicity in both metaphysical and ethical terms, emphasising especially the correlates of incorporeality and immutability and Origen's use of both philosophical and exegetical arguments to support them, chapters 6–7 build on chapters 3–4 by demonstrating that Origen uses simplicity to create a ‘via media’ (p. 165) between Valentinian and Monarchian trinitarian theology. In so doing, Ip demonstrates again that simplicity historically understood is both a richer doctrine than it is often presented to be, and that it is also a doctrine that entered the Christian tradition not only independently of, but also in contradiction to, modalistic theologies. The book ends with an epilogue offering some prospective narrative of Origen's fourth-century legacy and the codification of simplicity as an axiom of patristic theology.
The attentive reader will find in these pages persuasive, careful arguments based on detailed analyses of the relevant texts. Even when one may wish to quibble with Ip's readings of individual passages, the broader conclusions and insights of the book remain no less engaging and significant. In fact, Anthony Briggman's God and Christ in Irenaeus (Oxford: OUP, 2019), which appeared after this study had already been written and substantially revised, opens the possibility of holding that Irenaeus held a positive view of the Son's generation from the Father that he saw as compatible with divine simplicity. If this is the case Ip's point that the earliest Christian theologians reconciled the Father–Son distinction with simplicity would be confirmed. Ip's emphasis on the ethical dimensions of simplicity in ancient theology is illuminating, and Ip's refusal to exclude the exegetical dimension of Origen's thought even in a study of the philosophical elements of Origen's theology is commendable. This study, along with Ip's article on simplicity in Athenagoras (Studia Patristica 100 [2020], pp. 61–70), is as useful as an introduction to ancient philosophical theology and methods of its study as it is as a contribution to scholarly understandings of the numerous individual passages, figures and broader narratives it engages.
