From this it is also clear that the assumption of human nature was outstanding in—suitability to the person of the Word. For, if the assumption of human nature is ordered to the salvation of men, if the ultimate salvation of man is to be perfected in his intellective part by the contemplation of the First Truth, it should have been by the Word who proceeds from the Father by an intellectual emanation that human nature was assumed.
 There especially seems to be, furthermore, a kind of kinship of the Word for human nature. For man gets his proper species from being rational. But the Word is kin to the reason. Hence, among the Greeks “word” and reason” are called logos. Most appropriately, then, was the Word united to the reasonable nature, for by reason of the kinship mentioned the divine Scripture attributes the name “image” to the Word and to man; the Apostle says of the Word that He is “the image of the invisible God” (Col. 1:15); and the same writer says of man that “the man is the image of God” (1 Cor. 11:7).  The Word also has a kind of essential kinship not only with the rational nature, but also universally with the whole of creation, since the Word contains the essences of all things created by God, just as man the artist in the conception of his intellect comprehends the essences of all the products of art. Thus, then, all creatures are nothing but a kind of real expression and representation of those things which are comprehended in the conception of the divine Word; wherefore all things are said (John 1: 3) to be made by the Word. There, fore, suitably was the Word united to the creature, namely, to human nature.
Next - CONTRA GENTILES: BOOK FOUR: SALVATION - Chapter 43 THAT THE HUMAN NATURE ASSUMED BY THE WORD DID NOT PRE-EXIST ITS ASSUMPTION, BUT WAS ASSUMED IN THE CONCEPTION ITSELF