Whether each of the Divine Persons could have assumed human nature?
Objection 1: It would seem that no other Divine Person could have assumed human nature except the Person of the Son. For by this assumption it has been brought about that God is the Son of Man. But it was not becoming that either the Father or the Holy Ghost should be said to be a Son; for this would tend to the confusion of the Divine Persons. Therefore the Father and Holy Ghost could not have assumed flesh.
Objection 2: Further, by the Divine Incarnation men have come into possession of the adoption of sons, according to Rom. 8:15: "For you have not received the spirit of bondage again in fear, but the spirit of adoption of sons." But sonship by adoption is a participated likeness of natural sonship which does not belong to the Father nor the Holy Ghost; hence it is said (Rom. 8:29): "For whom He foreknew He also predestinated to be made conformable to the image of His Son." Therefore it seems that no other Person except the Person of the Son could have become incarnate.
Objection 3: Further, the Son is said to be sent and to be begotten by the temporal nativity, inasmuch as He became incarnate. But it does not belong to the Father to be sent, for He is innascible, as was said above (FP, Q 32, A 3; FP, Q 43, A 4). Therefore at least the Person of the Father cannot become incarnate.
On the contrary, Whatever the Son can do, so can the Father and the Holy Ghost, otherwise the power of the three Persons would not be one. But the Son was able to become incarnate. Therefore the Father and the Holy Ghost were able to become incarnate.
I answer that, As was said above (AA 1,2,4), assumption implies two things, viz. the act of the one assuming and the term of the assumption. Now the principle of the act is the Divine power, and the term is a Person. But the Divine power is indifferently and commonly in all the Persons. Moreover, the nature of Personality is common to all the Persons, although the personal properties are different. Now whenever a power regards several things indifferently, it can terminate its action in any of them indifferently, as is plain in rational powers, which regard opposites, and can do either of them. Therefore the Divine power could have united human nature to the Person of the Father or of the Holy Ghost, as It united it to the Person of the Son. And hence we must say that the Father or the Holy Ghost could have assumed flesh even as the Son.
Reply to Objection 1: The temporal sonship, whereby Christ is said to be the Son of Man, does not constitute His Person, as does the eternal Sonship; but is something following upon the temporal nativity. Hence, if the name of son were transferred to the Father or the Holy Ghost in this manner, there would be no confusion of the Divine Persons.
Reply to Objection 2: Adoptive sonship is a certain participation of natural sonship; but it takes place in us, by appropriation, by the Father, Who is the principle of natural sonship, and by the gift of the Holy Ghost, Who is the love of the Father and Son, according to Gal. 4:6: "God hath sent the Spirit of His Son into your hearts crying, Abba, Father." And therefore, even as by the Incarnation of the Son we receive adoptive sonship in the likeness of His natural sonship, so likewise, had the Father become incarnate, we should have received adoptive sonship from Him, as from the principle of the natural sonship, and from the Holy Ghost as from the common bond of Father and Son.
Reply to Objection 3: It belongs to the Father to be innascible as to eternal birth, and the temporal birth would not destroy this. But the Son of God is said to be sent in regard to the Incarnation, inasmuch as He is from another, without which the Incarnation would not suffice for the nature of mission.
III · Q. 3, Art. 6: Whether several Divine Persons can assume one and the same individual nature?
Whether several Divine Persons can assume one and the same individual nature?
Objection 1: It would seem that two Divine Persons cannot assume one and the same individual nature. For, this being granted, there would either be several men or one. But not several, for just as one Divine Nature in several Persons does not make several gods, so one human nature in several persons does not make several men. Nor would there be only one man, for one man is "this man," which signifies one person; and hence the distinction of three Divine Persons would be destroyed, which cannot be allowed. Therefore neither two nor three Persons can take one human nature.
Objection 2: Further, the assumption is terminated in the unity of Person, as has been said above (A 2). But the Father, Son, and Holy Ghost are not one Person. Therefore the three Persons cannot assume one human nature.
Objection 3: Further, Damascene says (De Fide Orth. iii, 3,4), and Augustine (De Trin. i, 11,12,13), that from the Incarnation of God the Son it follows that whatever is said of the Son of God is said of the Son of Man, and conversely. Hence, if three Persons were to assume one human nature, it would follow that whatever is said of each of the three Persons would be said of the man; and conversely, what was said of the man could be said of each of the three Persons. Therefore what is proper to the Father, viz. to beget the Son, would be said of the man, and consequently would be said of the Son of God; and this could not be. Therefore it is impossible that the three Persons should assume one human nature.
On the contrary, The Incarnate Person subsists in two natures. But the three Persons can subsist in one Divine Nature. Therefore they can also subsist in one human nature in such a way that the human nature be assumed by the three Persons.
I answer that, As was said above (Q 2, A 5, ad 1), by the union of the soul and body in Christ neither a new person is made nor a new hypostasis, but one human nature is assumed to the Divine Person or hypostasis, which, indeed, does not take place by the power of the human nature, but by the power of the Divine Person. Now such is the characteristic of the Divine Persons that one does not exclude another from communicating in the same nature, but only in the same Person. Hence, since in the mystery of the Incarnation "the whole reason of the deed is the power of the doer," as Augustine says (Ep. ad Volusianum cxxxvii), we must judge of it in regard to the quality of the Divine Person assuming, and not according to the quality of the human nature assumed. Therefore it is not impossible that two or three Divine Persons should assume one human nature, but it would be impossible for them to assume one human hypostasis or person; thus Anselm says in the book De Concep. Virg. (Cur Deus Homo ii, 9), that "several Persons cannot assume one and the same man to unity of Person."
Reply to Objection 1: In the hypothesis that three Persons assume one human nature, it would be true to say that the three Persons were one man, because of the one human nature. For just as it is now true to say the three Persons are one God on account of the one Divine Nature, so it would be true to say they are one man on account of the one human nature. Nor would "one" imply unity of person, but unity in human nature; for it could not be argued that because the three Persons were one man they were one simply. For nothing hinders our saying that men, who are many simply, are in some respect one, e.g. one people, and as Augustine says (De Trin. vi, 3): "The Spirit of God and the spirit of man are by nature different, but by inherence one spirit results," according to 1 Cor. 6:17: "He who is joined to the Lord is one spirit."
Reply to Objection 2: In this supposition the human nature would be assumed to the unity, not indeed of one Person, but to the unity of each Person, so that even as the Divine Nature has a natural unity with each Person, so also the human nature would have a unity with each Person by assumption.
Reply to Objection 3: In the mystery of the Incarnation, there results a communication of the properties belonging to the nature, because whatever belongs to the nature can be predicated of the Person subsisting in that nature, no matter to which of the natures it may apply. Hence in this hypothesis, of the Person of the Father may be predicated what belongs to the human nature and what belongs to the Divine; and likewise of the Person of the Son and of the Holy Ghost. But what belongs to the Person of the Father by reason of His own Person could not be attributed to the Person of the Son or Holy Ghost on account of the distinction of Persons which would still remain. Therefore it might be said that as the Father was unbegotten, so the man was unbegotten, inasmuch as "man" stood for the Person of the Father. But if one were to go on to say, "The man is unbegotten; the Son is man; therefore the Son is unbegotten," it would be the fallacy of figure of speech or of accident; even as we now say God is unbegotten, because the Father is unbegotten, yet we cannot conclude that the Son is unbegotten, although He is God.