CLE [III, Q. 2, Art. 10]

Whether the Union of the Incarnation Took Place by Grace?

Objection 1: It would seem that the union of the Incarnation did not
take place by grace. For grace is an accident, as was shown above
(I-II, Q. 110, A. 2). But the union of the human nature to the Divine
did not take place accidentally, as was shown above (A. 6). Therefore
it seems that the union of the Incarnation did not take place by
grace.

Obj. 2: Further, the subject of grace is the soul. But it is written
(Col. 2:9): "In Christ [Vulg.: 'Him'] dwelleth all the fulness of the
Godhead corporeally." Therefore it seems that this union did not take
place by grace.

Obj. 3: Further, every saint is united to God by grace. If,
therefore, the union of the Incarnation was by grace, it would seem
that Christ is said to be God no more than other holy men.

_On the contrary,_ Augustine says (De Praed. Sanct. xv): "By the same
grace every man is made a Christian, from the beginning of his faith,
as this man from His beginning was made Christ." But this man became
Christ by union with the Divine Nature. Therefore this union was by
grace.

_I answer that,_ As was said above (I-II, Q. 110, A. 1), grace is
taken in two ways:--first, as the will of God gratuitously bestowing
something; secondly, as the free gift of God. Now human nature stands
in need of the gratuitous will of God in order to be lifted up to
God, since this is above its natural capability. Moreover, human
nature is lifted up to God in two ways: first, by operation, as the
saints know and love God; secondly, by personal being, and this mode
belongs exclusively to Christ, in Whom human nature is assumed so as
to be in the Person of the Son of God. But it is plain that for the
perfection of operation the power needs to be perfected by a habit,
whereas that a nature has being in its own suppositum does not take
place by means of a habit.

And hence we must say that if grace be understood as the will of God
gratuitously doing something or reputing anything as well-pleasing or
acceptable to Him, the union of the Incarnation took place by grace,
even as the union of the saints with God by knowledge and love. But
if grace be taken as the free gift of God, then the fact that the
human nature is united to the Divine Person may be called a grace,
inasmuch as it took place without being preceded by any merits--but
not as though there were an habitual grace, by means of which the
unio