Tertia Pars, Question 19 — Summa Theologiae
Article 1. Whether in Christ there is only one operation of the Godhead and Manhood?
Objection 1. It would seem that in Christ there is but one operation of the Godhead and the Manhood. For Dionysius says (Div. Nom. ii): “The most loving operation of God is made manifest to us by the supersubstantial Word having taken flesh integrally and truly, and having operated and suffered whatsoever befits His human and Divine operation.” But he here mentions only one human and Divine operation, which is written in Greek theandrike, i.e. God-manlike. Hence it seems that there is but one composite operation in Christ.
Objection 2. Further, there is but one operation of the principal and instrumental agent. Now the human nature in Christ was the instrument of the Divine, as was said above (III:7:1 ad 3; III:8:1 ad 1; k1 18, 1, ad 2). Hence the operations of the Divine and human natures in Christ are the same.
Objection 3. Further, since in Christ there are two natures in one hypostasis or person, whatever pertains to the hypostasis or person is one and the same. But operation pertains to the hypostasis or person, for it is only a subsisting suppositum that operates; hence, according to the Philosopher (Metaph. i, 1), acts belong to singulars. Hence in Christ there is only one operation of the Godhead and the Manhood.
Objection 4. Further, as being belongs to a subsisting hypostasis, so also does operation. But on account of the unity of hypostasis there is only one operation of the Godhead and the (III:17:2. Hence, on account of the same unity, there is one operation in Christ.
Objection 5. Further, as being belongs to a sub-operated there is one operation. But the same thing was operated by the Godhead and the Manhood, as the healing of the lepers or the raising of the dead. Hence it seems that in Christ there is but one operation of the Godhead and the Manhood.
On the contrary, Ambrose says (De Fide ii, 8): “How can the same operation spring from different powers? Cannot the lesser operate as the greater? And can there be one operation where there are different substances?”
I answer that, As was said above (III:18:1), the aforesaid heretics who placed one will in Christ placed one operation in Christ. Now in order better to understand their erroneous opinion, we must bear in mind that wherever there are several mutually ordained agents, the inferior is moved by the superior, as in man the body is moved by the soul and the lower powers by the reason. And thus the actions and movements of the inferior principle are things operated rather than operations. Now what pertains to the highest principle is properly the operation; thus we say of man that to walk, which belongs to the feet, and to touch, which belongs to the hand, are things operated by the man—one of which is operated by the soul through the feet, the other through the hands. And because it is the same soul that operates in both cases, there is only one indifferent operation, on the part of the thing operating, which is the first moving principle; but difference is found on the part of what is operated. Now, as in a mere man the body is moved by the soul, and the sensitive by the rational appetite, so in the Lord Jesus Christ the human nature is moved and ruled by the Divine. Hence they said that there is one indifferent operation on the part of the Godhead operating, but divers things operated, inasmuch as the Godhead of Christ did one thing by Itself, as to uphold all things by the word of His power—and another thing by His human nature, as to walk in body. Hence the Sixth Council [Third Council of Constantinople, Act. 10] quotes the words of Severus the heretic, who said: “What things were done and wrought by the one Christ, differ greatly; for some are becoming to God, and some are human, as to walk bodily on the earth is indeed human, but to give hale steps to sickly limbs, wholly unable to walk on the ground, is becoming to God. Yet one, i.e. Incarnate Word, wrought one and the other—neither was this from one nature, and that from another; nor can we justly affirm that because there are distinct things operated there are therefore two operating natures and forms.”
But herein they were deceived, for what is moved by another has a twofold action—one which it has from its own form—the other, which it has inasmuch as it is moved by another; thus the operation of an axe of itself is to cleave; but inasmuch as it is moved by the craftsman, its operation is to make benches. Hence the operation which belongs to a thing by its form is proper to it, nor does it belong to the mover, except in so far as he makes use of this kind of thing for his work: thus to heat is the proper operation of fire, but not of a smith, except in so far as he makes use of fire for heating iron. But the operation which belongs to the thing, as moved by another, is not distinct from the operation of the mover; thus to make a bench is not the work of the axe independently of the workman. Hence, wheresoever the mover and the moved have different forms or operative faculties, there must the operation of the mover and the proper operation of the moved be distinct; although the moved shares in the operation of the mover, and the mover makes use of the operation of the moved, and, consequently, each acts in communion with the other.