Commentaria in Summam contra Gentiles, Liber IV

Having seen that we confess the Incarnation of God by divine authority, St. Thomas wishes to exclude the errors that have arisen concerning the Incarnation itself ¹. Concerning this, however, he does two things: first, he excludes the errors that are concerning those things which are united in this Incarnation; second, those that are concerning the union itself, ch. xxxiv.

Concerning the first he does three things: first, he excludes the errors concerning the divinity of Christ; second, concerning the body, the following chapter; third, concerning the soul, ch. xxxii.

As to the first, he says that Ebion, Cerinthus, and later Paul of Samosata and Photinus, confess only a human nature in Christ; but they fabricate that his divinity was not by nature, but through a certain excellent participation in divine glory, which he had merited through works.

Against this error, however, besides those things which were said against it above ² while treating of the divinity of the Son, St. Thomas argues because this position takes away the mystery of the Incarnation.

For it follows, first, not that God assumed flesh so that he might become man, but rather that a carnal man was made God, against what John says, The Word was made flesh: for thus, rather conversely, flesh would have been made the Word.

It follows, second, that emptying or descending would not belong to the Son of God, but rather glorification and ascending to man: against that saying of the Apostle, Who, though he was in the form of God, etc.

It follows, third, that it is not true what the Lord says, I came down from heaven: against what is said in John 3, No man hath ascended, etc.; and Ephesians 4, He that descended, etc.

It follows, fourth, that the Son was not sent by the Father, nor that he went out from him to come into the world, but only that he went to the Father: against that saying in John 16, I go to him, etc.