Today’s Aquinas: Intellectual Abstraction

We’re blogging through St. Thomas Aquinas’ Compendium Theologiae, sometimes called his Shorter Summa. Find the previous posts here.

Today’s post is from Chapter 61, “Dependence of the Hypostases on the Personal Properties”.

I'm afraid that things will continue to be difficult and technical for another half-dozen chapters, before we conclude with the Trinity and move on to (very slightly) less lofty concerns.

We've been talking about the personal properties that distinguish the Divine Persons from one another: paternity, filiation, and procession. Each of these properties denotes a particular relation in God; and indeed, the Divine Persons are these subsistent relations. Thomas continues,

This makes it clear that if we were to remove the personal properties by intellectual abstraction, the hypostases could not remain.

Intellectual abstraction: what's this? And what are hypostases? The Greek word hypostasis is same word we usually translate into English as "substance", a thing that exists on its own. In Christian theology, though, it most commonly pops up when we speak of the persons of the Trinity, or of Christ who unites in one hypostasis two natures, divine and human. (We call this the hypostatic union.) I suspect Thomas uses the Greek word here as a technical theological term, to emphasize that he is referring specifically to the Divine Persons rather than to substances in general.

In normal English, abstraction is when we consider just some aspect of a thing, apart from the rest of the thing. If I think of an orange's shape, I'm abstracting its shape from the actual fruit in front of me. Abstraction is the way we analyze a thing, considering each of its aspects in turn:

If a form is removed by intellectual abstraction, the subject of the form remains. Thus if whiteness is removed, the surface remains; if the surface is removed, the substance remains; if the form of the substance is removed, prime matter remains. But if the subject is removed, nothing remains.

I can consider the orange's color; then, leaving that aside I can consider the orange's shape and size; then, leaving that aside then, leaving that aside, I can consider the orange's pebbly surface and internal structure; and then, ultimately, I can consider the orange purely as what it is: the fruit of an orange tree. At this point there is nothing left to abstract. We've gotten to the heart of the matter; if you take away anything else, you're no longer contemplating anything at all. There will be nothing left of the orange.

Now, I can quite happily contemplate an orange without worrying about whether it has seeds or a navel. But it seems that I can't abstract away the personal properties from God and still be contemplating the Triune God.

In the case of God, the personal properties are the subsisting persons themselves. They do not constitute the persons in the sense that they are added to pre-existing supposita; for in the Godhead nothing that is predicated absolutely, but only what is relative, can be distinct. Therefore, if the personal properties are removed by intellectual abstraction, no distinct hypostases remain.

The non-personal notions of innascibility and common spiration, however, are not essential in the same way: