Thomas Aquinas

“ Since the Divine Person is infinite, no addition can be made to it: Hence Cyril says [*Council of Ephesus, Part I, ch. 26] : "We do not conceive the mode of conjunction to be according to addition"; just as in the union of man with God, nothing is added to God by the grace of adoption, but what is Divine is united to man; hence, not God but man is perfected. ”

“ 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. ”

“ 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. ”

“ Secondly, the intellect stands towards God, not indeed as knowing God as He is, but in its own way, i.e. understanding manifoldly and separately what in God is one: and in this way our intellect can understand the Divine goodness and wisdom, and the like, which are called essential attributes, without understanding Paternity or Filiation, which are called Personalities. And hence if we abstract Personality by our intellect, we may still understand the Nature assuming. ”

“ 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. ”

“ But two human natures cannot be wholly united together, inasmuch as the soul of one would be united to the body of the other; and, again, two bodies would be together, which would give rise to confusion of natures. Therefore it is not possibly for one Divine Person to assume two human natures. ”

“ There is nothing which human malice cannot abuse, since it even abuses God's goodness, according to Rom. 2:4: "Or despisest thou the riches of His goodness?" Hence, even if the Person of the Father had become incarnate, men would have been capable of finding an occasion of error, as though the Son were not able to restore human nature. ”

“ But after the Incarnation the Father can still assume a human nature distinct from that which the Son has assumed; for in nothing is the power of the Father or the Son lessened by the Incarnation of the Son. Therefore it seems that after the Incarnation the Son can assume another human nature distinct from the one He has assumed. ”

“ 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. ”

“ And hence, if the Divine Person were to assume two human natures, He would be called, on account of the unity of suppositum, one man having two human natures. Now many men are said to be one people, inasmuch as they have some one thing in common, and not on account of the unity of suppositum. So likewise, if two Divine Persons were to assume one singular human nature, they would be said to be one man, as stated (A [6] , ad 1) , not from the unity of suppositum, but because they have some one thing in common. ”

“ I answer that, The intellect stands in two ways towards God. First, to know God as He is, and in this manner it is impossible for the intellect to circumscribe something in God and leave the rest, for all that is in God is one, except the distinction of Persons ”

“ Further, person is constituted by nature. But it is repugnant that the thing constituted should assume the constituent, since the effect does not act on its cause. Hence it is not befitting to a Person to assume a nature. ”

“ 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. ”

“ Hence just as we now say three Persons, on account of holding three personal properties, so likewise if we mentally exclude the personal properties there will still remain in our thought the Divine Nature as subsisting and as a Person. And in this way It may be understood to assume human nature by reason of Its subsistence or Personality. ”

“ Because in God "what is," and "whereby it is," are one, if any one of the things which are attributed to God in the abstract is considered in itself, abstracted from all else, it will still be something subsisting, and consequently a Person, since it is an intellectual nature. ”

“ Consequently, in order to judge of a word's signification or co-signification, we must consider the things which are around us, in which a word derived from some form is never used in the plural unless there are several supposita. For a man who has on two garments is not said to be "two persons clothed," but "one clothed with two garments" ”

“ A created nature is completed in its essentials by its form, which is multiplied according to the division of matter. And hence, if the composition of matter and form constitutes a new suppositum, the consequence is that the nature is multiplied by the multiplication of supposita. But in the mystery of the Incarnation the union of form and matter, i.e. ”