Abstract

In lieu of an abstract, here is a brief excerpt of the content:Dominus Deus Noster Deus Unus Est:Aquinas on Divine UnityArchbishop Rowan Williams"The Lord our God is one LORD," says the Shema (Deut 6:4), echoed by Christians and Muslims alike. "We believe in one God," the Nicene Creed announces; and the Shahada's "There is no deity but God" affirms the same. But at first sight, Christian theology looks like the outlier here, as St. Thomas obliquely acknowledges when, early in his discussion of the Trinity (Summa theologiae [ST] I, q. 30, a. 1, obj. 1 and ad 1), he quotes Boethius: "That [alone] is truly one in which there is no numeration" (obj. 3). If there is a plurality of relation in God, there is something that can be enumerated, says Thomas. This objection is duly met by distinguishing between "absolute" plurality and the mutually definitory relations of the Trinitarian life which rule out any "composition" in God. But, for this fully to make sense, we must return to Thomas's explicit discussion of divine unity (ST I, q. 11). The present essay attempts a brief examination of how divine unity is understood in this quaestio, in the hope of clarifying an aspect of Aquinas's Trinitarian thought, and also of suggesting ways of developing an implicit theme of some significance for contemporary theology.It is still a textbook commonplace that "Western" Trinitarian theology begins from the divine unity and treats the distinction of the divine persons only in the light of this prior reality. The eloquent polemic of Orthodox theologians like Vladimir Lossky has played a major role in canonizing this supposed opposition. He writes, for example, that Western Trinitarianism treats the relationships of the divine hypostases as "a system of relationships within the one essence: something logically posterior to the essence," with [End Page 555] the distinguishing "relations of origin" (originary fatherhood, generatedness, procession) as "more or less swallowed up in the nature or essence."1 Examples could be multiplied, from Lossky and many others, and from Western theologians influenced by this characterization.2 The very structure of Aquinas's Summa theologiae, with the quaestiones de Deo uno preceding those de Trinitate, is sometimes adduced in support of this analysis of the ambiguities and inadequacies of Thomist Trinitarianism, and of a general Western resistance to the radical personalism of authentic patristic theology.But, polemic apart, what is Aquinas actually saying in his treatment of divine unity, primarily in ST I, q. 11? The four articles of the quaestio deal with whether saying that something is "one" actually tells us anything beyond the postulation of something as a coherent subject/substance; with whether unity and plurality are simply opposed and incompatible notions; with whether it is right to say that God is one, and if so, whether he is maxime unus, one in a unique and unsurpassable sense. Basic to his argument, as we shall see, is something touched on briefly in ST I, q. 30, a. 1, where his response (ad 3) to the Boethian formulation associates divine unity with simplicity—that is, with non-composition:3 affirming the divine unity is, crucially, denying the applicability of certain kinds of discourse in theology. But, as we shall see, part of the abiding importance of Aquinas's discussion is, perhaps unexpectedly, to open the door to a new ontological perspective in which laying out the difference between different senses of "unity" allows for the development of a more systematically relational metaphysics. Related to this is the distinction drawn (especially in ad 2 of [End Page 556] a. 3) between "mathematical" and "metaphysical" unity; one of the problems with a good deal of modern criticism of Western Trinitarianism is a failure to reckon with the diversity of ways in which "unus est" might be used, and St. Thomas is in fact abundantly clear about the senses that must be ruled out in theology—including any sense that would oppose an "individual" essence to "multiple" hypostases, as if the divine essence were itself a sort of numerically identified individual.The ground for this is laid in the first article. If we say that something is "one," we are surely offering a determination of it, specifying one way of...