Thomas’s Trinitarian Apologetics

I was struck in this reading by the simultaneously traditional and apologetic quality of Aquinas’s defence of Trinitarian doctrine.  This responds to an Islamic criticism of the Christian doctrine of Christ’s generation which criticized the Christian doctrine of the Trinity on the grounds that it entailed God’s having a wife.  Aquinas relies on the so-called “psychological analogy” first developed by Augustine to establish a doctrine of divine generation which is “intellectual” rather than “fleshly.” In human beings, the act of understanding “conceives” a concept which is expressed as an audible word and exists interioly as a “word of intellect.”  In God, this “word of intellect” is neither distinct from His being, since this is its source, nor is it accidental to his being, for God is simple. A similar argument applies to the act of Love, which is identified with the second procession, the Holy Spirit. Thus, Aquinas judges he has offered an account of the Trinity of persons which does not compromise the divine substance.

To my eyes, this argument avoids several of the pitfalls of other approaches to Trinitarian apologetics we have thus far encountered and offers an additional challenge to unitarian monotheism. It emphasizes a logic of relationality — there are two principle mental acts, understanding and will, which proceed from the origin — as opposed to simply trying to find the number three in God and thus rendering the persons imperfect; and precisely by this logic, it avoids attributing some divine attributes to one person and some to another.  

Is this an apt summary of the points toward which Thomas is driving?  How far is the argument “apologetic” — demonstrating the coherence of a claim that unity can be trinity — as opposed to constructive, offering further insight into the Christian doctrine of the Trinity?  If these are Thomas’s aims with this interior account of the Trinity, how would they be controverted? The most obvious response, it seems to me, would be to claim that “understanding” and “love” do not sufficiently escape the trouble of attributing particular attributes to particular persons and thereby depriving, for instance, the Holy Spirit of understanding.  Furthermore, there seems to be an implicit “offensive” argument in Thomas’s argument, inasmuch as it stakes out a claim that a God who has the capacity either to know or to love must have a hypostatic word and love.  Does this argument find itself fleshed out more in later polemics?  What are the likely responses to Thomas’s defensive and offensive arguments?