Summa Theologica, Part III (Tertia Pars) / From the Complete American Edition

by Saint Aquinas Thomas

Reply Obj. 3: There are two principles of corporeal life: one the effective principle, and in this way the Word of God is the principle of all life; the other, the formal principle of life, for since "in living things to be is to live," as the Philosopher says (De Anima ii, 37), just as everything is formally by its form, so likewise the body lives by the soul: in this way a body could not live by the Word, Which cannot be the form of a body. _______________________

SIXTH ARTICLE [III, Q. 2, Art. 6]

Whether the Human Nature Was United to the Word of God Accidentally?

Objection 1: It would seem that the human nature was united to the Word of God accidentally. For the Apostle says (Phil. 2:7) of the Son of God, that He was "in habit found as a man." But habit is accidentally associated with that to which it pertains, whether habit be taken for one of the ten predicaments or as a species of quality. Therefore human nature is accidentally united to the Son of God.

Obj. 2: Further, whatever comes to a thing that is complete in being comes to it accidentally, for an accident is said to be what can come or go without the subject being corrupted. But human nature came to Christ in time, Who had perfect being from eternity. Therefore it came to Him accidentally.

Obj. 3: Further, whatever does not pertain to the nature or the essence of a thing is its accident, for whatever is, is either a substance or an accident. But human nature does not pertain to the Divine Essence or Nature of the Son of God, for the union did not take place in the nature, as was said above (A. 1). Hence the human nature must have accrued accidentally to the Son of God.

Obj. 4: Further, an instrument accrues accidentally. But the human nature was the instrument of the Godhead in Christ, for Damascene says (De Fide Orth. iii, 15), that "the flesh of Christ is the instrument of the Godhead." Therefore it seems that the human nature was united to the Son of God accidentally.

On the contrary, Whatever is predicated accidentally, predicates, not substance, but quantity, or quality, or some other mode of being. If therefore the human nature accrues accidentally, when we say Christ is man, we do not predicate substance, but quality or quantity, or some other mode of being, which is contrary to the Decretal of Pope Alexander III, who says (Conc. Later. iii): "Since Christ is perfect God and perfect man, what foolhardiness have some to dare to affirm that Christ as man is not a substance?"

I answer that, In evidence of this question we must know that two heresies have arisen with regard to the mystery of the union of the two natures in Christ. The first confused the natures, as Eutyches and Dioscorus, who held that from the two natures one nature resulted, so that they confessed Christ to be "from" two natures (which were distinct before the union), but not "in" two natures (the distinction of nature coming to an end after the union). The second was the heresy of Nestorius and Theodore of Mopsuestia, who separated the persons. For they held the Person of the Son of God to be distinct from the Person of the Son of man, and said these were mutually united: first, "by indwelling," inasmuch as the Word of God dwelt in the man, as in a temple; secondly, "by unity of intention," inasmuch as the will of the man was always in agreement with the will of the Word of God; thirdly, "by operation," inasmuch as they said the man was the instrument of the Word of God; fourthly, "by greatness of honor," inasmuch as all honor shown to the Son of God was equally shown to the Son of man, on account of His union with the Son of God; fifthly, "by equivocation," i.e. communication of names, inasmuch as we say that this man is God and the Son of God. Now it is plain that these modes imply an accidental union.

But some more recent masters, thinking to avoid these heresies, through ignorance fell into them. For some conceded one person in Christ, but maintained two hypostases, or two supposita, saying that a man, composed of body and soul, was from the beginning of his conception assumed by the Word of God. And this is the first opinion set down by the Master (Sent. iii, D, 6). But others desirous of keeping the unity of person, held that the soul of Christ was not united to the body, but that these two were mutually separate, and were united to the Word accidentally, so that the number of persons might not be increased. And this is the third opinion which the Master sets down (Sent. iii, D, 6).