Journal of the History of Philosophy

“It would take a book to work through all the literature in detail,” observes Michael Gorman on the question of how to interpret Thomas Aquinas’s views on whether Christ had a single esse or two, “and it would be one of the most tedious books ever written” (102). To the nonspecialist, the details of how a medieval theologian thought the divinity and humanity of Christ relate to each other in terms drawn from Aristotelian metaphysics must rank as one of the most obscure, not to mention uninteresting, problems in the history of philosophy. Sometimes it can seem like that to the specialist, too.

Luckily, Gorman’s authoritative and engaging book not only avoids the tedium of the volume he imagines, it makes an excellent case for the philosophical value of its subject. For Gorman, Aquinas “truly is a philosopher and theologian of genius, someone from whom anyone has a lot to learn” (6). His purpose is to explain Aquinas’s understanding of the hypostatic union —the union in a single hypostasis (or substance) of Christ’s divinity and humanity. But in so doing, he must engage at a wider level with Aquinas’s metaphysics, which has to provide a reasonable philosophical account of reality in general while also providing conceptual space for theological doctrines that seem, on the face of it, to contradict that account. Gorman navigates the sometimes tortuous thought processes with a sure touch, making Aquinas a credible dialogue partner for modern philosophers.

This approach is evident from the first chapter, which provides an exceptionally clear explanation of the metaphysical concepts Aquinas employs in his christology. The account is nuanced and sensitive to Aquinas’s own ambiguity (we learn, for example, that Aquinas was much more explicit about the meaning of ‘substance’ than he was about ‘nature’), and is particularly helpful in comparing Aquinas’s metaphysics to that of modern writers. We encounter such names as Kit Fine, Michael Della Rocca, and Jonathan Schaffer.

In chapter 2, we learn how Aquinas uses his metaphysical concepts in articulating the doctrine of incarnation, according to which Christ is one person with two natures, and what this allows Aquinas to say about him. But how it is the case that Christ can be one person with two natures, and how these natures relate to each other, remain obscure. Gorman fleshes out Aquinas’s account of the hypostatic union in subsequent chapters by framing it in terms of solutions to a series of problems, some of which Aquinas has clear answers to, and some of which he does not. As the book progresses, Gorman wades further into ever murkier exegetical waters, requiring him to do more and more constructive work of his own to suggest what Aquinas might have said and, at times, to go beyond it. For example, in chapter 4—on the perennial question of why Christ’s human nature does not ground a human person distinct from the divine person—Gorman offers a modified definition of ‘nature,’ according to which it is something that could ground a supposit rather than (as Aquinas himself suggests) something that actually does so.

Gorman’s writing is a model of clarity and readability. Non-specialists in medieval philosophy or theology need have no fear here: everything is explained straightforwardly, without presupposing any knowledge beyond the common stock of modern analytic philosophy. At the same time, Gorman’s analysis has much to offer the specialist. Analytic theologians and others interested in incarnation as a philosophical problem will find particular food for thought in chapter 6, on the meaning of reduplicative statements such as “Christ is impassible qua divine and passible qua human.” And throughout, Gorman’s attention to terminological precision leads him to make distinctions not commonly found either in the literature on Aquinas or on incarnation more generally. He distinguishes, for example, between a “human nature” (what makes something a human being) and a “human reality” (the human nature plus the various accidents that any particular...