Who God Is
Who God Is
Our discussion here will be limited, but it is possible to get to the heart of Thomas’s natural “theology proper.” In order to understand the doctrine of God, obtained through natural reason alone, according to Aquinas, the central focus must be on God’s simplicity. As a matter of fact, according to Eleonore Stump, the simplicity of God, for Aquinas, “is foundational for everything in Aquinas’s thought from his metaphysics to his ethics.”54
Thomas begins his discussion of God’s simplicity in this way:
When the existence of a thing has been ascertained there remains the further question of the manner of its existence, in order that we may know its essence. Now, because we cannot know what God is, but rather what He is not, we have no means for considering how God is, but rather how He is not. . . . Now it can be shown how God is not, by denying of Him whatever is opposed to the idea of Him—viz., composition, motion, and the like.55
There are eight aspects to God’s simplicity that Thomas wants to evaluate:
Concerning His simplicity, there are eight points of inquiry: (1) Whether God is a body? (2) Whether He is composed of matter and form? (3) Whether in Him there is composition of quiddity, essence or nature, and subject? (4) Whether He is composed of essence and existence? (5) Whether He is composed of genus and difference? (6) Whether He is composed of subject and accident? (7) Whether He is in any way composite, or wholly simple? (8) Whether He enters into composition with other things?56
In the interest of space, we will leave the more obvious aspects aside. Except for certain cults, few would affirm (1), (2), or (3) of God; each of them suppose that God is material in some way. We will briefly summarize (4), (5), (7), and (8). We will then lay out Thomas’s denial of (6), so that, in the “Critique” below, in the discussion of “Who God Is,” we may focus on some of its insufficiencies.
In (4), Thomas argues that God’s existence and essence are identical. Because, as we noted above, Thomas sees a real distinction between existence and essence, any essence that exists must have that existence caused by something else. “But this cannot be true of God; because we call God the first efficient cause.”57 In God, therefore, essence and existence must be identical.
In (5), Thomas then affirms that God is not contained in a category of “genus,” for three reasons. “First, because a species is constituted of genus and difference.”58 Here Thomas makes it clear that when we use the word “God,” we are not referring to one who is a specific instance of something more generic. If that were so, then God would be included in a category with others of the same genus.
Secondly, Thomas argues that if God were to be included in a genus, it would have to be the genus “being.” But the Philosopher has shown (Metaph. iii) that being cannot be a genus, for every genus has differences distinct from its generic essence. Now no difference can exist distinct from being, for nonbeing cannot be a difference. It follows then that God is not in a genus.59
Thirdly, God cannot be in a genus because then there would be both generic identity and essential differences. “For the existence of man and of horse is not the same; as also of this man and that man: thus in every member of a genus, existence and quiddity—i.e., essence—must differ.”60 It cannot be true of God, in other words, that his existence would be generically related to, though essentially different from, other things in a genus. This would deny the absolute uniqueness of God.
Though (7) and (8) contain some nuances of previous arguments, essentially they repeat the reasons why it must be the case that God is simple.
In (6), Thomas rightly argues that God cannot be composed of subject and accident, for the following reasons.61 First, if God were a subject composed of accidents, then he would not be complete in himself. He would need something else—something not essential to him—in order to be properly identified, “for a subject is in some sense made actual by its accidents. But there can be no potentiality in God.” Secondly, if God were composed of subject and accident, he would not be absolute. He would have something added to him in order to make him what he is. This, we can see, is similar to Thomas’s first reason. In this second reason, however, we should see that Thomas wants to deny that anything relative is added to God’s existence and character. Thirdly, says Thomas, God cannot have any essential accidents because such accidents would somehow have to be caused in God. But, as Thomas has argued, “There can be nothing caused in God, since He is the first cause. Hence it follows that there is no accident in God.”62
For Thomas, the simplicity of God follows from his absolute character. If God is a se, there can be nothing on which he depends in order to be who he is. To be independent and absolute means that God is complete in himself. He is, as Thomas puts it, pure actuality (actus purus). He is pure actuality because there can be no potentiality in God. If there were, then he would be in need of something else in order to be God.
This view of the simplicity of God is a central aspect of Thomas’s natural theology; it is the focus of natural reason’s demonstration of God’s character. For Thomas, it is central to everything else he teaches. We will reserve further discussion of it until our “Critique,” below, in the section on “Who God Is.”