Reply Obj. 1: From these words nothing may be gathered, except that the Word, by assuming the parts of human nature, assumed the whole human nature. And thus the assumption of parts is prior in the order of the intellect, if we consider the operation, but not in order of time; whereas the assumption of the nature is prior if we consider the intention: and this is to be simply first, as was said above.
Reply Obj. 2: God is so simple that He is also most perfect; and hence the whole is more like to God than the parts, inasmuch as it is more perfect.
Reply Obj. 3: It is a personal union wherein the assumption is terminated, not a union of nature, which springs from a conjunction of parts. _______________________
SIXTH ARTICLE [III, Q. 6, Art. 6]
Whether the Human Nature Was Assumed Through the Medium of Grace?
Objection 1: It would seem that the Son of God assumed human nature through the medium of grace. For by grace we are united to God. But the human nature in Christ was most closely united to God. Therefore the union took place by grace.
Obj. 2: Further, as the body lives by the soul, which is its perfection, so does the soul by grace. But the human nature was fitted for the assumption by the soul. Therefore the Son of God assumed the soul through the medium of grace.
Obj. 3: Further, Augustine says (De Trin. xv, 11) that the incarnate Word is like our spoken word. But our word is united to our speech by means of breathing (spiritus). Therefore the Word of God is united to flesh by means of the Holy Spirit, and hence by means of grace, which is attributed to the Holy Spirit, according to 1 Cor. 12:4: "Now there are diversities of graces, but the same Spirit."
On the contrary, Grace is an accident in the soul, as was shown above (I-II, Q. 110, A. 2). Now the union of the Word with human nature took place in the subsistence, and not accidentally, as was shown above (Q. 2, A. 6). Therefore the human nature was not assumed by means of grace.
I answer that, In Christ there was the grace of union and habitual grace. Therefore grace cannot be taken to be the medium of the assumption of the human nature, whether we speak of the grace of union or of habitual grace. For the grace of union is the personal being that is given gratis from above to the human nature in the Person of the Word, and is the term of the assumption. Whereas the habitual grace pertaining to the spiritual holiness of the man is an effect following the union, according to John 1:14: "We saw His glory . . . as it were of the Only-begotten of the Father, full of grace and truth"—by which we are given to understand that because this Man (as a result of the union) is the Only-begotten of the Father, He is full of grace and truth. But if by grace we understand the will of God doing or bestowing something gratis, the union took place by grace, not as a means, but as the efficient cause.