Commentaria in Summam contra Gentiles, Liber IV

After St. Thomas excluded errors concerning Christ's body, he wishes to exclude errors concerning his soul¹. And he excludes two: one in this chapter; the other in the following chapter.

I. The first error, then, which is excluded in this place, was that of Arius, who said that there was no soul in Christ, but that only flesh was assumed, to which the divinity stood in place of a soul. For since he wished to assert that the Son of God is a creature and less than the Father on the basis of those things which show weakness in Christ, lest anyone refute his testimonies by saying that these things belong to Christ according to human nature, he wickedly removed the soul from Christ, so that, since certain things cannot belong to a human body—such as that he marveled and the like—it would be necessary to refer such things to the lessening of the Son of God. Moreover, he took up in support of his error that which is said: The Word was made flesh, where mention is made of flesh alone, but not of the soul. — Apollinaris also followed Arius in this position.

II. But against this error it is argued. First. The Word of God is God. Therefore he cannot be the form of a body, since God cannot be the form of a body. Therefore etc.

This argument is useful not only against Apollinaris, who confessed the Word of God to be true God, but also against Arius, who denied this. For not only can God not be the form of a body, but neither can any of the supercelestial spirits, among whom Arius placed the Son of God as the highest; unless perhaps according to the opinion of Origen, who posits that human souls are of the same species as supercelestial spirits—which was refuted above.

Second. It follows that Christ was not a man: against the Apostle, 1 Tim. 2. For the soul pertains principally to the definition of man. But when that which pertains to the definition of man is removed, there cannot be a true man. Therefore etc.

Third. It follows that there was not true flesh in Christ, nor any of the parts of a man: because not only the definition of man, but also of each of his parts depends on the soul².

But this is contrary to what the Lord showed in the last chapter of Luke: A spirit does not have flesh, etc. Therefore etc.

It should be noted that, although flesh and bone and the other parts of a man differ from one another by accidental species, because the accidents of flesh are one thing and the accidents of bone another, nevertheless all are of the same substantial species, and all have the completion of their definition and species from the same form by which man is constituted in his species: for there is one substantial form of the whole and of all its parts, since parts do not exist through their own distinct acts of being, but through one act of being, which is the act of being of the whole primarily and per se, and secondarily the act of being of the parts. For this reason St. Thomas says that the definition of each of the parts of a man depends on the soul, which is the form of man.

III. Fourth. Christ would not be of the same species as other men: because things that differ according to form cannot be of the same species. Therefore he cannot be called the Son of the Virgin Mary, or that she is his mother. — The consequence is proved. Because that which is generated from a living being cannot be called its son unless it proceeds in the same species.

Fifth. It is expressly said in the Gospel that Christ had a soul: namely in Matt. 26 and John 12. Therefore etc.

If it be said that the Son of God himself is called the soul: — against this is what he himself says in John 10, I have the power, etc.; from which it is understood that there is something other than the soul in Christ that had the power of laying down his soul and taking it up. But it was not in the power of the body to be united to the Son of God or to be separated from him, since this exceeds even the power of nature. Therefore in Christ the soul must be one thing, and the divinity another, to which such power is attributed.

Sixth. In Christ there were anger and the like, which are passions of the sensitive soul, according to the Philosopher in the seventh book of the Physics. Therefore in Christ there was a sensitive soul. Therefore etc.

If it be said that these things are said of Christ metaphorically in the Gospels: — let something be taken which must be taken properly, namely to hunger. For just as other bodily things which the Evangelists recount concerning Christ are understood properly, so it must be understood properly that he ate, and consequently that he hungered. But to hunger belongs only to one having a sensitive soul, since hunger is an appetite for food. Therefore etc.