Commentaria in Summam contra Gentiles, Liber IV

Having excluded false opinions concerning the Incarnation of Christ, St. Thomas concludes what must be held according to the Catholic faith¹. Concerning this, moreover, he does two things: first, he shows what was proposed; second, he infers a certain corollary².

I. As to the first, he posits this conclusion: According to the tradition of the Catholic faith, in Christ there is a perfect divine nature and a perfect human nature; and these two natures are united in Christ, not by indwelling alone, nor in an accidental manner, nor in a personal relation alone (as the last opinion stated, to be sure³); but according to one hypostasis and one supposit.

It is proved. In this way alone can those things be preserved which are said in the Scriptures concerning the Incarnation. Therefore etc.

II. The assumption is proved. Sacred Scripture attributes without distinction the things that belong to God to that man, and the things that belong to that man to God, as is clear from what was set down before. Therefore, it is necessary that he of whom both are said be one and the same; and that that according to which they are predicated of Christ be one thing and another. — Therefore, it is necessary that in Christ there be two natures unconfused and unmixed, and that Christ be one hypostasis and one supposit of human nature and divine nature.

2. He does not prove the first part of the first consequence, but leaves it manifest. For unless that man were the same as God, divine things would not be predicated of him; and unless God were the same as that man, human things would not be predicated of him; because divine things are not predicated except of him who is God, and human things are not predicated except of him who is man. — But he proves the second part thus. The divine and human things that are said of Christ have an opposition, such as suffered and impassible, dead and immortal. But opposites cannot truly be said of the same subject according to the same respect. Therefore, it is necessary that divine and human things be said of Christ according to one thing and another.

3. But he proves the second consequence, as to its first part indeed, thus. Natural properties are predicated of each thing according to its nature: just as to be borne downward is predicated of this stone according to the nature of heaviness. If therefore that according to which divine and human things are predicated of Christ is one thing and another, it is necessary to say that there are in Christ two natures unconfused and unmixed. — But as to the second part, he proves it thus. That of which natural properties are predicated according to a proper nature belonging to the genus of substance is the hypostasis and supposit of that nature. Therefore, if that of which human and divine things are predicated concerning Christ is one and undivided, it is necessary to say that Christ is one hypostasis and one supposit. From which it is concluded that divine things are thus truly and properly predicated of that man according as that man conveys the supposit, not only of the human nature, but also of the divine; and conversely, human things are predicated of the Word of God inasmuch as he is the supposit of the human nature.

III. Concerning the proof of the second consequence, it must be considered that nothing is called a natural property of anything except because it follows upon its nature; for natural is named from nature. But the nature must be predicated of that whose nature it is prior to its natural properties, which follow upon the nature. Therefore nature is the reason why natural properties belong to anything. On this account St. Thomas rightly assumed, for the proof of the first part of the consequence, that natural properties are predicated of each thing according to the nature of that whose natural properties they are: it being assumed as true that certain divine things said of Christ are as it were his natural properties according to our mode of understanding, such as impassible; and likewise that certain human things said of him are his natural properties, such as passible.

It must be considered secondly, that the name of hypostasis and supposit is said only of an individual of substance, but not of an individual of accident, as St. Thomas says in III Sent., d. VI, q. 1⁴. Therefore, in the proof of the second part of the consequence, he did not say absolutely that that of which natural properties are predicated according to a proper nature is a hypostasis and supposit, because in that way even an individual of accident, of which its natural properties are predicated according to its nature, would be a hypostasis and supposit; but he added, belonging to the genus of substance, in order to give to understand that the name of hypostasis and supposit is said only in substances.

IV. As to the second point⁵, St. Thomas infers this corollary: that, although the Son is incarnate, nevertheless it is not necessary that the Father or the Holy Spirit be incarnate. — It is proved. Because the Incarnation was not made according to union in nature, in which the three Persons agree, but according to supposit and hypostasis, according as the three Persons are distinguished.

It should be noted, from the doctrine of St. Thomas, in the Third Book, d. 1, q. II, a. 1, that when some things agree in something and are distinguished in something, it is necessary that if one is joined with something, the other also is joined with it when the conjunction is made according to that in which they communicate, but not when it is made according to that in which they are distinguished. Just as man and donkey communicate in animal; therefore, with whatever a donkey communicates in genus, a man also communicates. But because man and donkey are distinguished by specific differences, it is not necessary that whatever agrees with a donkey in specific difference should in the same way agree with a man. Since, therefore, the three divine Persons indeed agree in nature, but are distinguished in personality, if something were united to the Son in nature, it would of necessity be united to the Father and to the Holy Spirit; but if something is united to the Son in person, it is not necessary that it be united to the other persons. And therefore, because in the Incarnation the union was not made in nature, namely so that one should come to be from the divine and human nature, but only in the person of the Son, so that there is one person of the Son subsisting in humanity and divinity; it is not necessary, if the Son is incarnate, that the other divine persons be incarnate. And this is the foundation of the reason for this corollary.

V. For the evidence of that which has been said very often, namely, that in Christ there are not several persons, nor several hypostases, or several supposits, but only one person, one hypostasis, and one supposit: it must be considered, from the doctrine of St. Thomas in the Third Part, q. II, a. 2, ad 3, that person, which is the same as hypostasis and supposit in a rational nature, is not entirely the same as an individual and singular substance, but adds above it the character of subsisting per se. For not every individual of the genus of substance is a person, but only that which subsists per se. Hence the hand of Socrates, although it is a certain individual of substance, is not nevertheless a person, because it does not subsist per se, but exists in something more perfect, namely in its whole.

2. It must be considered secondly, that since personality is the ultimate actuality of a singular thing subsisting per se, and its ultimate substantial complement, it is incompatible with it to be assumed into the unity of another person: for if it were assumed by another into unity of person, it would no longer be the ultimate complement, because it would be completed through the assumption by another. It is conceded, therefore, that Christ assumed an individual substance according as individual substance is taken for a substance that is singular—for he did not assume a universal humanity separated from all singulars, but this humanity—yet it is not conceded that he assumed a human person or hypostasis, because that humanity of Christ did not have everything that belongs to the character of person and hypostasis, but was anticipated by the divine supposit. Hence Christ indeed assumed whatever belongs to the intrinsic essence of this singular humanity, namely this soul and this body and the humanity composed of them; nevertheless he did not assume whatever belongs to the character of person inasmuch as it is a person. And therefore in him there are not two persons or two hypostases, although there are in him two singular natures.

3. From which it is clear that the arguments of Scotus, in the place cited above⁶, by which he shows that person adds nothing positive above an individual, do not proceed against the mind of St. Thomas. For they prove that person adds nothing above an individual that belongs intrinsically to the essence of the person, such as that it exists; which indeed we concede. But they do not prove that it in no way adds something that belongs to a person as its ultimate actuality, with which it is incompatible to be united to something more complete than itself. For not everything that belongs in any way to human nature is capable of being assumed to the unity of a divine person, but only that which is part of the nature or its property. But the complement itself of the supposit is not capable of being assumed into such a unity of person, for the reason that it cannot be united to something more perfect, but only to that which is compared to it as potency to act. Hence also we say that the human nature in Christ does not have its own esse. But it would have it if it were dismissed by the Word: because it lacks its own esse for no other reason than that it lacks its own personality, as having been anticipated by the divine supposit.