The Doctrine of Catholic Faith concerning the Incarnation

ACCORDING to the tradition of Catholic faith we must say that in Christ there is one perfect divine nature, and a perfect human nature, made up of a rational soul and human flesh; and that these two natures are united in Christ, not by mere indwelling of the one in the other, or in any accidental way, as a man is united with his garment, but in unity of one person. For since Holy Scripture without any distinction assigns the things of God to the Man Christ, and the things of the Man Christ to God, He must be one and the same person, of whom both varieties of attributes are predicable. But because opposite attributes are not predicable of one and the same subject in the same respect, and there is an opposition between the divine and human attributes that are predicated of Christ, -- as that He is passible and impassible, dead and immortal, and the like, -- these divine and human attributes must be predicated of Christ in different respects. If we consider that of which these opposite attributes are predicated, we shall find no distinction to draw, but unity appears there. But considering that according to which these several predications are made, there we shall see the need of drawing a distinction.* Since that according to which divine attributes are predicated of Christ is different from that according to which human attributes are predicated of Him, we must say that there are in Him two natures, unamalgamated and unalloyed. And since that of which these human and divine attributes are predicated is one and indivisible, we must say that Christ is one person, and one suppositum, supporting a divine and a human nature. Thus alone will divine attributes duly and properly be predicated of the Man Christ, and human attributes of the Word of God.

Thus also it appears how, though the Son is incarnate, it does not follow that the Father or the Holy Ghost is incarnate: for the incarnation does not have place in respect of that unity of nature wherein in the three Persons agree, but in respect of person and suppositum, wherein the three Persons are distinct. Thus as in the Trinity there is a plurality of persons subsisting in one nature, so in the mystery of the Incarnation there is one person subsisting in a plurality of natures.

4.36 : Of the Error of Macarius of Antioch, who posited one Operation only and one Will only in Christ
4.41 : Some further Elucidation of the Incarnation