Today’s Aquinas: The Trinity is no Accident

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 54, “Relations in God Not Accidental”.

Thomas has explained that the Father, Son, and Holy Spirit are distinguished from each other by their relations with each other. The Father is the begetter, the Son the begotten; the Holy Spirit proceeds from the Father and the Son, and not the other way around. Now he goes on to explain that these relations are subsistent rather than accidental, that is, they are part of what it is to be the Trinity rather than something added to the Trinity:

These relations cannot inhere in God accidentally, because the operations on which the relations follow directly are the very substance of God, and also because, as was shown above there can be no accident in God. Hence, if the relations are really in God, they cannot be accidentally inherent, but must be subsistent. How it is that what is an accident in other things, can exist substantially in God, is clear from the doctrine previously set forth.

Consider my relation to my father. He is the begetter and I the begotten son. But while it is part of being human to be the son of a mother and father, it isn’t part of being human to be the son of my particular father. There are lots of humans who have other fathers. Thus, my relation to my father is accidental rather than subsistent.

But in God there can be no accidents in this sense; and more than that Thomas has shown that the Trinity indeed flows from the very substance of God. So these relations are no accident.

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