The Perfectly Simple Triune God: Aquinas and His Legacy by D. Stephen Long (review)

This important monograph offers an intellectual history of the idea of the perfectly simple triune God, focusing on the fates of the doctrines of simplicity and trinity in modern theology. Long commences with a judicious exposition of the first forty-three questions of the Summa Theologiae, a segment of Thomas's opus which, at least since Cajetan but especially following the European enlightenment, has been perceived as having two parts—de deo uno (on the One God; questions one through twenty-six) and de deo trino (on the Triune God; twenty-seven through forty-three). Long convincingly demonstrates that, for Thomas, the first forty-three questions in fact constitute a single doctrine of God, according to which "de deo uno must be read from the perspective of de deo trino, and de deo trino must be read from the perspective of de deo uno" (xxii). Correspondingly, Thomas is shown as having held together reason and faith, philosophy and theology, rational knowledge of God and practical divinity, metaphysical speculation and experiential knowledge, and so on. Furthermore, Long makes the case that Thomas's grand summary of the doctrine of God lies just beyond the mid-point of a continuity of thought stretching backward to Scripture and the patristic era and forward through the reformation, Protestant scholasticism, and pietism. As such, it is demonstrable that the classical approach to the doctrine of God, which dominated the history of Christian thought up to the early eighteenth century, does not pit divine simplicity against the divine trinity, but acknowledges God as perfectly simple and triune.

In the second half, Long encapsulates in five questions the eclipse of the idea of the perfectly simple triune God following the enlightenment. It is an ambitious reading of the modern project, using the themes of simplicity and trinity to taxonomize distinct theological trajectories. Since, for the sake of space, Long is forced to make quick work of a host of interlocutors and movements, one wonders whether his analysis goes far and deep enough. Still, he helpfully identifies why certain strands of modern theology opt for trinity and economy over simplicity.

In Long's reading, process theology chides classical theism and the "substance metaphysics" putatively undergirding it for positing a relation of direct causality between God and the world. This problematizes the question of theodicy, as it becomes difficult to avoid the conclusion that God causes pain, suffering, and evil. So-called "open" theism attacks the classical model on the grounds that it allegedly eradicates human freedom. Once again, the God who sovereignly causes and controls creatures becomes the foil of the God who loves, where here the idea of human moral autonomy is prioritized and made the measure of the right approach to the question of God's identity. The relatively recent trend of "analytic theology" finds fault with the warrants and logical coherency of the classical model, thus objecting to the mystery of God as perfectly simple and triune. Theologians from various quarters raise cultural and political challenges to classical theism, arguing that the doctrine of the perfectly simple triune God is wedded to unjust theological structures which, in turn, recurrently have been invoked to rationalize oppression, colonialism, and racial, hierarchical, and heteronormative and cisgender hegemonies. Finally, a number of modern theologians have objected to the classical doctrine of God on the grounds that it fails to take the biblical witnesses seriously and radically enough, emphasizing the metaphysically aloof deity of Hellenized Christianity instead of the Bible's representation of God as the one who suffers and dies to redeem creation.

While Long is attuned to some of these concerns, he worries that even greater difficulties will emerge for theology if, on the basis of these objections to the classical model, the doctrines of simplicity and trinity are situated as alternatives. Indeed, the force of the book's second half is to establish divine simplicity as a deeply rooted theological claim bearing significant...