Commentaria in Summam contra Gentiles, Liber IV

The second error, close to the preceding one, was that of Valentinus, who said that Christ did not have an earthly body, but brought it from heaven; and that He took nothing from His mother, but passed through her as through an aqueduct. Moreover, he confirmed his error by the authority of Sacred Scripture: John 3, No man hath ascended etc.; and John 6, I came down etc.; and 1 Cor. 15, The first man etc.

Now this proceeded, just like the preceding one, from a single false root: namely, because they believed that all earthly things were created by the devil. For since the Son of God appeared for this purpose, that He might destroy the works of the devil, as is said in 1 John 3, it was not fitting for Him to take a body from the creature of the devil, since it is also said in 2 Cor. 6, What fellowship etc.

II. But against this error it is argued first, because that which followed from the error of Manichaeus follows here too: namely, that Christ was not a true man, but an apparent one, etc. — The consequence is proved, assuming that for each species there are determinate essential principles, namely matter and form, from which the intelligible structure of a material species is constituted. For if the body of Christ was not earthly, there was not in Him true flesh and true bone, which are the proper matter of man, since fire, air, water, earth, and the like, are their proper matter. Therefore etc.

Second. It was not fitting that the Son of God should drag down the dignity of the assumed nature to something worse, but rather that He should exalt it. But a heavenly body is incorruptible according to nature, and inalterable, and cannot be transferred outside its own place. Therefore He did not bring this down to lower things, but rather made what was earthly and passible to be incorruptible and heavenly.

Third. The body of David was earthly. Therefore the body of Christ was as well: since, according to the Apostle, the Son of God was made of the seed of David according to the flesh.

Fourth. The Son of God is said to be made and born of Mary: Gal. 4, and Matt. 1. But this would not be said if He had passed through her as through a pipe, assuming nothing from her. Therefore etc.

Fifth. Mary could not be called the Mother of Jesus. Therefore etc.

Sixth. It follows that we are not of one with Him; and consequently neither can we be called His brethren. Nor did He Himself partake of flesh and blood: since these are composed of the lower elements. But this is contrary to the things that are said in Heb. 2. Therefore etc.

III. Now to the things on which they rely, it is said first, that Christ did not descend from heaven according to His body or His soul, but according to the fact that He is God. This is shown because, when He had said, No man etc., He added, the Son of man, who is in heaven, in which He shows that He so descended from heaven that He nevertheless did not cease to be in heaven: which is proper to the Godhead, according to that of Jer. 23, I fill heaven and earth.

It is said second, that this descent of the Son of God is not understood according to local motion: but according to the fact that He joined an earthly substance to Himself.

2. It must be noted that, since we understand divine things under the similitudes of bodily things, in order to signify a new mode of God's being on earth, Scripture uses the word descent, not indeed understanding by this word local motion, by which a body, in approaching one place, withdraws from another; but only a new mode of being on earth, namely through the assumption of an earthly substance. For although God, before the Incarnation, was in heaven and on earth, He was not, however, in this mode such that human nature was joined to Him in unity of person. And on this account He is said to have descended from heaven, because He joined and united to Himself human nature, which is not heavenly but earthly.

Now to the root of the position it is said that it is false: as was shown above in the second Book.