Commentaria in Summam contra Gentiles, Liber I

Just as it was shown that God is not the formal esse of all things, so in this chapter it is shown that He is the form of no thing ¹.

I. First proof. The divine esse cannot be the act of some other quiddity distinct from itself. But God is the divine esse itself. Therefore, etc.

Concerning this proposition, that the divine Esse cannot be the act of any other quiddity, a doubt is raised. For in Christ the human nature exists through the divine Esse ². Therefore the divine Esse is its act: because nothing else is meant by the actuality of being being the act of something than that it exists through such an actuality. Therefore the divine Esse is the act of some nature and quiddity distinct from itself.

It is said, granting the assumption, that the divine esse is not the act of the human nature: for it is not united to it formally as act to potency. Nor is it said to exist through the divine esse as though existing belonged to it first of all, for existing does not belong per se first to the nature, but to the supposit; but because it is really united to the supposit which exists formally through the divine esse.

Therefore the consequence is denied. — To the proof it is said that the assumption is true if that thing exists first and of itself through such actuality; but not if it exists as drawn toward the unity of a supposit.

It is said further, for the understanding of the proposition of Saint Thomas, that he does not take "quiddity" for the nature as distinguished from the supposit, but indifferently for every entity. For the sense is that the divine esse cannot be the formal act of any entity really distinct from itself.

It is said thirdly that, according to Hervaeus and others holding the mind of St. Thomas, the claim that there is not in Christ but one esse—unless we speak of supposital and personal esse—has been assumed falsely: for in Christ the human nature does not exist by the divine esse, but by its own esse.

II. Second. The form of a body is not esse, but a principle of being; God, however, is esse. Therefore, etc.

Third. Each part is compared to the composite whole as potency to act. But in God there is no potentiality. Therefore, etc.

Note that, although form is act in relation to matter, nevertheless the whole has the character of form in comparison with its parts; for, as is said in Physics II ³ and Metaphysics V ⁴, the parts are the matter of the whole; therefore form itself also, in comparison with the whole, has the mode of potency. Hence it is rightly said here that the part is related to the whole as potency to act.

Fourth. God is the most noble being, as it were the first cause of esse. Therefore, etc. — The consequence is proved. Because that which has esse of itself is nobler than that which has esse in another. But every form of a body has esse in another. Therefore, etc.

Fifth. Then the composite of God and body would be a self-mover, since God is the first mover. But a self-mover can be moved and not moved. Such a being does not have from itself the indeficiency of motion. Therefore there must be above it another first mover, which bestows perpetuity upon motion. And thus there would be some mover prior to God.

Saint Thomas adds, moreover, that the course of this argument is useful for those who posit the eternity of motion; but even if this is not posited, the same conclusion can be reached from the regularity of the motion of the heavens. For the uniformity of motion requires that there be some mover entirely immobile, which is not part of the self-mover: since a self-mover, just as it has in itself being moved and not being moved, so it has being moved more quickly or more slowly.

III. It is also confirmed by the authority of the Psalm, "He is exalted," etc.; and of Job 11, "Higher than heaven," etc.

Likewise the error of the idolatrous gentiles is excluded, who posited God to be the soul of the heavens, or even of the whole world; and on this account that divine worship was owed to the parts of the world, as having God within themselves as their form. Averroes makes mention of this error in Metaphysics XI⁵, comm. 41, saying that this position was the fall of the sages of the nation of the Sabians; and Augustine, Book IV of De Civitate Dei, c. xxxi, and Book VII, c. vi.