Commentaria in Summam contra Gentiles, Liber II

From the predetermined truth Saint Thomas excludes the error of those who said that the soul was of the divine substance. In regard to this he does two things: first, he proves the proposition; second, he shows whence that error had its origin ¹.

1. First, therefore, it is argued thus. Human souls did not exist before bodies, as has been shown. Therefore the soul is not of the divine substance. — The consequence is evident. Because the divine substance is eternal, as was proved above.

Note that the soul can be understood to be of the divine substance in two ways. In one way, as being of that substance in number which is God, as from matter, just as a potter makes some vessel from a portion of clay. In another way, because it is of the same species as God, in the manner in which we say that Socrates and Plato are of the same species. Whichever of these two ways it is understood, it is necessary that souls existed before bodies: for it belongs to the definition of the divine nature, whether it is taken in the manner of a singular or in the manner of a species, that it be eternal.

Second. The soul is a form. Therefore etc. — The consequence is evident, because God cannot be the form of any thing.

Third. The substance of God is not in potency to anything. Therefore, etc. — The consequence is evident, because everything from which something comes to be is in potency to that thing.

Fourth. God is altogether immobile. Therefore, etc. — The consequence is evident, because that from which something comes to be is in some way changed.

Fifth. The soul is varied according to knowledge and virtue and their opposites. Therefore it is not of the divine substance, which is altogether unchangeable.

Sixth. In the soul there is potency and act, namely the possible intellect and the agent intellect. Therefore etc. — The consequence is evident. For God is pure act, in which there is no potentiality.

Seventh. God is altogether impartible. Therefore the soul cannot be anything of him unless it be his whole substance. But this is impossible: for then there would be one soul of all men, since the divine substance cannot be other than one.

II. As to the second ², a threefold foundation is set forth from which the aforesaid error took its origin. The first is that all who posited a principle of things attributed it to the soul, as is clear in Book I of the De Anima. Some, however, positing that there is no incorporeal substance, held that the noblest of bodies—whether air, or fire, or whatever other principle they posited—was God. — From this root the error of the Manichaeans also sprouted, who thought God to be a certain light extended through infinite spaces, of which they said the soul was a certain particle.

But this foundation was rejected above, insofar as it posits that God and the soul are a body.

2. The second foundation is that some have held that there is one intellect for all men. The ancients, however, said that every separate substance is God. From this it followed that our intellect, or the human soul, belongs to the divine nature.

But this too has been disproved above.

3. The third is this: because understanding, which is considered most proper to God, seems to belong to no substance in the lower world except man, through the soul, which is also held to be immortal.

This seems to be favored by what is said in Genesis 1, where, after it is stated, "Let us make man to our image and likeness," there is added ³: "God formed man of the slime of the earth, and breathed into his face the breath of life."

But to this it is said first that that likeness, as regards understanding, does not show the soul to be of divine nature, since in understanding it suffers manifold defect.

It is said second, that the aforesaid inspiration demonstrates a process of life from God into man according to a certain likeness: but not according to unity of substance. This is evident, because one who blows bodily into someone's face—the source of the metaphor—drives air into his face, but does not emit into him any part of his own substance ⁴.

Nothing occurs concerning this conclusion that would create a difficulty, since it is entirely remote from all truth. Saint Thomas treats it, moreover, in the Prima Pars, q. 90, a. 1, and in the Second Book of the Sentences, d. 17, a. 1.