Aquinas on the Trinity - Compendium of Theology Questions 36-42, and 50-56

 Aquinas on the Trinity

In this lesser known work of St. Thomas, he spends a decent amount of time laying out some things which can be properly said about the Christian belief in God as a trinity. Here's what he says: 

                First, St. Thomas points out that the idea of the trinity is something which exceeds the bounds of philosophy insofar as we cannot come to know this truth on our own with our natural powers. We can come to know that God exists, but not that he is a trinity of persons. This is something given in revelation. But, being given this, we can seek to try to understand it more through the use of reason. 1 A second starting point he makes is mentioning that intellectual beings not only generate concepts of other things, but they turn that power of intellectualization upon themselves as well and generate themselves in a conceptual manner. 2 Now an analogy can be made here between natural and intellectual generation and the generation of the Father, Son, and Holy Spirit. In natural generation, there is of course a distinct father and mother who generate a distinct subject, their offspring. In intellectual generation (when we create ideas) the object itself that we are creating an idea of acts as a sort of active principle, a father, the mind which receives that impression, the mother, and the concept generated, the offspring. Where it gets interesting, though, is that when we consider the conception of oneself, it is slightly different. Since the object is ourselves which is impressed in our own intellect and generates a concept of ourselves, we are father, mother, and have the offspring within us as the concept. 3

                Turning to God here, things also become slightly different. God's essence and his existence are the same, perfectly actual, maximal, and infinite. Therefore, every characteristic of God is perfectly actual, maximal, and infinite. There's no distinction between God and his perfections or the perfections from one another. We only generate distinctions from our perspective when we speak analogously of God, otherwise we wouldn't understand at all. Since this is the case, that which God understands and wills also take on these God-like characteristics insofar as he wants them to. (This if, of course, how God creates us into being - simply by thinking them- and thus all things share in God's eternity by the fact that he thought us into being) Therefore, for God to comprehend himself means that not only does this thought take on substantial form (like creation), but since the thought is of God himself it takes on the substance of God himself. Thus, God's thought of himself generates the substance of himself. Thus, like natural generation which gives existence to a new substance, a physical offspring, and like intellectual generation which gives existence to an idea (not a substance) we have something similar to both. God generates an idea of himself which is also a substance. 4

Since natural existence and the action of understanding are distinct in us, we should note that a word conceived in our intellect, having only intellectual existence, differs in nature from our intellect, which has natural existence. In God, however, to be and to understand are identical. Therefore the divine Word that is in God, whose Word He is according to intellectual existence, has the same existence as God, whose Word He is. Consequently the Word must be of the same essence and nature as God Himself, and all attributes whatsoever that are predicated of God, must pertain also to the Word of God. 5

The same thing is true also of God's willing (loving) and therefore God's knowledge and willing of himself is at the same time a generation of himself into three persons. 6 Now, for those who are more familiar with philosophy, though, an objection arises which seems problematic. If God is supposed to be totally simple (without parts of distinctions) and all of his attributes to be equivocal with his existence, then how is it that God could be Father, Son, and Holy Spirit, something that introduces distinctions into his being? 7

The answer that Aquinas goes to is one in which he lays out the role of the potency as an individuating principle in things. He talks about the different types of beings, from material, to sensual, to intellectual, to those abstracted from matter altogether. The main point is that distinctions and parts come about because distinctions that are made between things. For material beings, of course, these distinctions are a result of the matter that makes them unique. For intellectual concepts and for the soul, it is the matter in which they are individuated. For the angels it is the distinction between their formal being and their limited natures which introduces a uniqueness to them and thus a distinction between them and others. Now, as is clear, as one becomes further and further abstracted from matter and the individuating process of distinction between essence and form/existence, then there's a unity that comes about. In God then there is a perfect unity of his being and everything that he is. 8 Thus, as we have already said, God and his conception and willing of himself are not distinct in their being, they are of the same substance. The only difference that Aquinas mentions is that of "procession," in that the Word is eternally generated by God's act of knowing himself and the Spirit is eternally generated by God's act of loving himself. This procession is a type of relation of one to the others, which Aquinas says is a real relation, not just a mental, accidental, or relative one. 9 Thus, there are truly three substantial persons within one nature of God. 10

But the divine intellect has this exclusive perfection: since God’s understanding is His existence, His intellectual conception, which is the intelligible likeness, must be His substance; and the case is similar with affection in God, regarded as loving. Consequently the representation of the divine intellect, which is God’s Word, is distinct from Him who produces the Word, not with respect to substantial existence, but only according to the procession of one from the other. And in God considered as loving, the same is true of the affection of love, which pertains to the Spirit. 11


1 - ch 36

2 - ch 37 

3 - ch 39

4 - ch 41-42

5 - ch 41

6 - ch 50

7 - ch 51 

8 - ch 52 

9 - ch 53- 54

10 - ch 55

11 - ch 52