But against this statement of the Catholic faith many difficulties come together, and by reason of these the adversaries of the faith attack the Incarnation.
 We showed in Book I that God is neither a body nor a power in a body. But, if He assumed flesh, it follows either that He was changed into a body or that He was a power in a body after the Incarnation. It seems, then, impossible that God was incarnate.
 Again, whatever acquires a new nature is subject to substantial change; for in this is a thing generated, that it acquires a nature. Then, if the hypostasis of the Son of God becomes a subsistent anew in human nature, it appears that it was substantially changed.
 Furthermore, no hypostasis of a nature extends outside that nature; rather, indeed, the nature is found outside the hypostasis, since there are many hypostases under the nature. If, then, the hypostasis of the Son of God becomes by the Incarnation the hypostasis of a human nature, the Son of God—one must conclude—is not everywhere after the Incarnation, since the human nature is not everywhere.
 Once again; one and the same thing has only one what-it-is, for by this one means a thing’s substance and of one there is but one. But the nature of any thing at all is its what-it-is, “for the nature of a thing is what the definition signifies.” It seems impossible, then, that one hypostasis subsist in two natures.
 Furthermore, in things which are without matter, the quiddity of a thing is not other than the thing, as was shown above. And this is especially the case in God, who is not only His own quiddity, but also His own act of being. But human nature cannot be identified with a divine hypostasis. There, fore, it seems impossible that a divine hypostasis subsist in human nature.
 Once again; a nature is more simple and more formal than the hypostasis which subsists therein, for it is by the addition of something material that the common nature is individuated to this hypostasis. If, then, a divine hypostasis subsists in human nature, it seems to follow that human nature is more simple and more formal than a divine hypostasis. And this is altogether impossible.
 It is, furthermore, only in matter and form composites that one finds a difference between the singular thing and its quiddity. This is because the singular is individuated by designated matter, and in the quiddity and nature of the species the latter is not included. For, in marking off Socrates, one includes this matter, but one does not in his account of human nature. Therefore, every hypostasis subsisting in human nature is constituted by signate matter. This cannot be said of the divine hypostasis. So, it does not seem possible that the hypostasis of God’s Word subsist in human nature.
 Furthermore, the soul and body in Christ were not less in power than in other men. But in other men their union constitutes a supposit an hypostasis, and a person. Therefore, in Christ the union of soul and body constitutes a supposit, hypostasis, and person of the Word of God; this is eternal. Therefore in Christ there is another supposit, hypostasis, and person beside the supposit, hypostasis, and person of the Word of God. Or so it seems.
 There is more. Just as soul and body constitute human nature in common, so this soul and this body constitute this man, and this is the hypostasis of a man. But this soul and this body were in Christ. Therefore, their union constitutes an hypostasis, it seems. And we conclude exactly as before.
 Again, this man who is Christ, considered as consisting of soul alone and body, is a certain substance; not, of course, a universal one; therefore, a particular one. Therefore, it is an hypostasis.
 Moreover, if the supposit of the human and the divine nature in Christ is identified, then in one’s understanding of the man who is Christ there ought to be a divine hypostasis. Of course, this is not in one’s understanding of other men. Therefore, man will be said equivocally of Christ and others. Hence, He will not belong to the same species with us.
 In Christ, what is more, one finds three things, as is clear from what was said: a body, a soul, and divinity. The soul, of course, since it is nobler than the body, is not the supposit of the body, but its form. Neither, then, is what is divine the supposit of the human nature; it is, rather, formally related to that nature.
 Furthermore, whatever accrues to something after its being is complete accrues to it accidentally. But, since the Word is from eternity, plainly the flesh assumed accrues to Him after His being is complete. Therefore, it accrues to Him accidentally.
Next - CONTRA GENTILES: BOOK FOUR: SALVATION - Chapter 41 HOW ONE SHOULD UNDERSTAND THE INCARNATION OF THE SON OF GOD