# Summa Theologiae/Third Part/Question 19
## Treatise on the Incarnation
### Question. 19 - OF THE UNITY OF CHRIST'S OPERATION (FOUR ARTICLES)

We must now consider the unity of Christ's operation; and under this head there are four points of inquiry:
(1) Whether in Christ there was one or several operations of the Godhead and Manhood?
(2) Whether in Christ there were several operations of the human nature?
(3) Whether Christ by His human operation merited anything for Himself?
(4) Whether He merited anything for us by it?

#### Art. 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 (Q[7], A[1], ad 3; Q[8], A[1], ad 1; Q[18], A[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 (Q[17], A[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 (Q[18], A[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. the 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. Therefore in Christ the human nature has its proper form and power whereby it acts; and so has the Divine. Hence the human nature has its proper operation distinct from the Divine, and conversely. Nevertheless, the Divine Nature makes use of the operation of the human nature, as of the operation of its instrument; and in the same way the human nature shares in the operation of the Divine Nature, as an instrument shares in the operation of the principal agent. And this is what Pope Leo says (Ep. ad Flavian. xxviii): "Both forms" (i.e. both the Divine and the human nature in Christ) "do what is proper to each in union with the other, i.e. the Word operates what belongs to the Word, and the flesh carries out what belongs to flesh." But if there were only one operation of the Godhead and manhood in Christ, it would be necessary to say either that the human nature had not its proper form and power (for this could not possibly be said of the Divine), whence it would follow that in Christ there was only the Divine operation; or it would be necessary to say that from the Divine and human power there was made up one power. Now both of these are impossible. For by the first the human nature in Christ is supposed to be imperfect; and by the second a confusion of the natures is supposed. Hence it is with reason that the Sixth Council (Act. 18) condemned this opinion, and decreed as follows: "We confess two natural, indivisible, unconvertible, unconfused, and inseparable operations in the same Lord Jesus Christ our true God"; i.e. the Divine operation and the human operation.
Reply to Objection 1: Dionysius places in Christ a theandric, i.e. a God-manlike or Divino-human, operation not by any confusion of the operations or powers of both natures, but inasmuch as His Divine operation employs the human, and His human operation shares in the power of the Divine. Hence, as he says in a certain epistle (Ad Caium iv), "what is of man He works beyond man; and this is shown by the Virgin conceiving supernaturally and by the unstable waters bearing up the weight of bodily feet." Now it is clear that to be begotten belongs to human nature, and likewise to walk; yet both were in Christ supernaturally. So, too, He wrought Divine things humanly, as when He healed the leper with a touch. Hence in the same epistle he adds: "He performed Divine works not as God does, and human works not as man does, but, God having been made man, by a new operation of God and man." Now, that he understood two operations in Christ, one of the Divine and the other of the human nature, is clear from what he says, Div. Nom. ii: "Whatever pertains to His human operation the Father and the Holy Ghost no-wise share in, except, as one might say, by their most gracious and merciful will," i.e. inasmuch as the Father and the Holy Ghost in their mercy wished Christ to do and to suffer human things. And he adds: "He is truly the unchangeable God, and God's Word by the sublime and unspeakable operation of God, which, being made man for us, He wrought." Hence it is clear that the human operation, in which the Father and the Holy Ghost do not share, except by Their merciful consent, is distinct from His operation, as the Word of God, wherein the Father and the Holy Ghost share.
Reply to Objection 2: The instrument is said to act through being moved by the principal agent; and yet, besides this, it can have its proper operation through its own form, as stated above of fire. And hence the action of the instrument as instrument is not distinct from the action of the principal agent; yet it may have another operation, inasmuch as it is a thing. Hence the operation of Christ's human nature, as the instrument of the Godhead, is not distinct from the operation of the Godhead; for the salvation wherewith the manhood of Christ saves us and that wherewith His Godhead saves us are not distinct; nevertheless, the human nature in Christ, inasmuch as it is a certain nature, has a proper operation distinct from the Divine, as stated above.
Reply to Objection 3: To operate belongs to a subsisting hypostasis; in accordance, however, with the form and nature from which the operation receives its species. Hence from the diversity of forms or natures spring the divers species of operations, but from the unity of hypostasis springs the numerical unity as regards the operation of the species: thus fire has two operations specifically different, namely, to illuminate and to heat, from the difference of light and heat, and yet the illumination of the fire that illuminates at one and the same time is numerically one. So, likewise, in Christ there are necessarily two specifically different operations by reason of His two natures; nevertheless, each of the operations at one and the same time is numerically one, as one walking and one healing.
Reply to Objection 4: Being and operation belong to the person by reason of the nature; yet in a different manner. For being belongs to the very constitution of the person, and in this respect it has the nature of a term; consequently, unity of person requires unity of the complete and personal being. But operation is an effect of the person by reason of a form or nature. Hence plurality of operations is not incompatible with personal unity.
Reply to Objection 5: The proper work of the Divine operation is different from the proper work of the human operation. Thus to heal a leper is a proper work of the Divine operation, but to touch him is the proper work of the human operation. Now both these operations concur in one work, inasmuch as one nature acts in union with the other.

#### Art. 2 - Whether in Christ there are several human operations?

Objection 1: It would seem that in Christ there are several human operations. For Christ as man communicates with plants by His nutritive soul, with the brutes by His sensitive soul, and with the angels by His intellective soul, even as other men do. Now the operations of a plant as plant and of an animal as animal are different. Therefore Christ as man has several operations.
Objection 2: Further, powers and habits are distinguished by their acts. Now in Christ's soul there were divers powers and habits; therefore also divers operations.
Objection 3: Further, instruments ought to be proportioned to their operations. Now the human body has divers members of different form, and consequently fitted to divers operations. Therefore in Christ there are divers operations in the human nature.
On the contrary, As Damascene says (De Fide Orth. iii, 15), "operation is consequent upon the nature." But in Christ there is only one human nature. Therefore in Christ there is only one human operation.
I answer that, Since it is by his reason that man is what he is; that operation is called human simply, which proceeds from the reason through the will, which is the rational appetite. Now if there is any operation in man which does not proceed from the reason and the will, it is not simply a human operation, but belongs to man by reason of some part of human nature---sometimes by reason of the nature of elementary bodies, as to be borne downwards---sometimes by reason of the force of the vegetative soul, as to be nourished, and to grow---sometimes by reason of the sensitive part, as to see and hear, to imagine and remember, to desire and to be angry. Now between these operations there is a difference. For the operations of the sensitive soul are to some extent obedient to reason, and consequently they are somewhat rational and human inasmuch as they obey reason, as is clear from the Philosopher (Ethic. i, 13). But the operations that spring from the vegetative soul, or from the nature of elemental bodies, are not subject to reason; consequently they are nowise rational; nor simply human, but only as regards a part of human nature. Now it was said (A[1]) that when a subordinate agent acts by its own form, the operations of the inferior and of the superior agent are distinct; but when the inferior agent acts only as moved by the superior agent, then the operation of the superior and the inferior agent is one. And hence in every mere man the operations of the elemental body and of the vegetative soul are distinct from the will's operation, which is properly human; so likewise the operations of the sensitive soul inasmuch as it is not moved by reason; but inasmuch as it is moved by reason, the operations of the sensitive and the rational part are the same. Now there is but one operation of the rational part if we consider the principle of the operation, which is the reason and the will; but the operations are many if we consider their relationship to various objects. And there were some who called this a diversity of things operated rather than of operations, judging the unity of the operation solely from the operative principle. And it is in this respect that we are now considering the unity and plurality of operations in Christ. Hence in every mere man there is but one operation, which is properly called human; but besides this there are in a mere man certain other operations, which are not strictly human, as was said above. But in the Man Jesus Christ there was no motion of the sensitive part which was not ordered by reason. Even the natural and bodily operations pertained in some respects to His will, inasmuch as it was His will "that His flesh should do and suffer what belonged to it," as stated above (Q[18], A[5]). Much more, therefore, is there one operation in Christ, than in any other man whatsoever.
Reply to Objection 1: The operations of the sensitive and nutritive parts are not strictly human, as stated above; yet in Christ these operations were more human than in others.
Reply to Objection 2: Powers and habits are diversified by comparison with their objects. Hence in this way the diversity of operations corresponds to the divers powers and habits, as likewise to the divers objects. Now we do not wish to exclude this diversity of operations from Christ's humanity, nor that which springs from a diversity of time, but only that which regards the first active principle, as was said above. (St. Thomas gives no reply to OBJ[3]; some codices add: Hence may be gathered the reply to the third objection.)

#### Art. 3 - Whether the human action of Christ could be meritorious to Him?

Objection 1: It would seem that the human action of Christ could not be meritorious to Him. For before His death Christ was a comprehensor even as He is now. But comprehensors do not merit: because the charity of the comprehensor belongs to the reward of beatitude, since fruition depends upon it. Hence it does not seem to be the principle of merit, since merit and reward are not the same. Therefore Christ before His passion did not merit, even as He does not merit now.
Objection 2: Further, no one merits what is due to him. But because Christ is the Son of God by nature, the eternal inheritance is due to Him, which other men merit by their works. And hence Christ Who, from the beginning, was the Word of God, could not merit anything for Himself.
Objection 3: Further, whoever has the principle does not properly merit what flows from its possession. But Christ has the glory of the soul, whence, in the natural course, flowed the glory of the body, as Augustine says (Ep. ad Dios cxviii); though by a dispensation it was brought about that in Christ the glory of the soul should not overflow to the body. Hence Christ did not merit the glory of the body.
Objection 4: Further, the manifestation of Christ's excellence is a good, not of Christ Himself, but of those who know Him. Hence it is promised as a reward to such as love Christ that He will be manifested to them, according to Jn. 14:21: "He that loveth Me, shall be loved of My Father, and I will love him and will manifest Myself to him." Therefore Christ did not merit the manifestation of His greatness.
On the contrary, The Apostle says (Phil. 2:8,9): "Becoming obedient unto death . . . For which cause God also hath exalted Him." Therefore by obeying He merited His exaltation and thus He merited something for Himself.
I answer that, To have any good thing of oneself is more excellent than to have it from another, for "what is of itself a cause is always more excellent than what is a cause through another," as is said Phys. viii, 5. Now a thing is said to have, of itself, that of which it is to some extent the cause. But of whatever good we possess the first cause by authority is God; and in this way no creature has any good of itself, according to 1 Cor. 4:7: "What hast thou that thou hast not received?" Nevertheless, in a secondary manner anyone may be a cause, to himself, of having certain good things, inasmuch as he cooperates with God in the matter, and thus whoever has anything by his own merit has it, in a manner, of himself. Hence it is better to have a thing by merit than without merit. Now since all perfection and greatness must be attributed to Christ, consequently He must have by merit what others have by merit; unless it be of such a nature that its want would detract from Christ's dignity and perfection more than would accrue to Him by merit. Hence He merited neither grace nor knowledge nor the beatitude of His soul, nor the Godhead, because, since merit regards only what is not yet possessed, it would be necessary that Christ should have been without these at some time; and to be without them would have diminished Christ's dignity more than His merit would have increased it. But the glory of the body, and the like, are less than the dignity of meriting, which pertains to the virtue of charity. Hence we must say that Christ had, by merit, the glory of His body and whatever pertained to His outward excellence, as His Ascension, veneration, and the rest. And thus it is clear that He could merit for Himself.
Reply to Objection 1: Fruition, which is an act of charity, pertains to the glory of the soul, which Christ did not merit. Hence if He merited by charity, it does not follow that the merit and the reward are the same. Nor did He merit by charity inasmuch as it was the charity of a comprehensor, but inasmuch as it was that of a wayfarer. For He was at once a wayfarer and a comprehensor, as was said above (Q[15], A[10]). And therefore, since He is no longer a wayfarer, He is not in the state of meriting.
Reply to Objection 2: Because by nature Christ is God and the Son of God, the Divine glory and the lordship of all things are due to Him, as to the first and supreme Lord. Nevertheless a glory is due to Him as a beatified man; and this He has partly without merit, and partly with merit, as is clear from what has been said.
Reply to Objection 3: It is by Divine appointment that there is an overflow of glory from the soul to the body, in keeping with human merit; so that as man merits by the act of the soul which he performs in the body, so he may be rewarded by the glory of the soul overflowing to the body. And hence not only the glory of the soul, but also the glory of the body falls under merit, according to Rom. 8:11: "He . . . shall quicken also our [Vulg.: 'your'] mortal bodies, because of His Spirit that dwelleth in us [Vulg.: 'you']." And thus it could fall under Christ's merit.
Reply to Objection 4: The manifestation of Christ's excellence is His good as regards the being which it has in the knowledge of others; although in regard to the being which they have in themselves it chiefly belongs to the good of those who know Him. Yet even this is referred to Christ inasmuch as they are His members.

#### Art. 4 - Whether Christ could merit for others?

Objection 1: It would seem that Christ could not merit for others. For it is written (Ezech. 18:4): "The soul that sinneth, the same shall die." Hence, for a like reason, the soul that meriteth, the same shall be recompensed. Therefore it is not possible that Christ merited for others.
Objection 2: Further, of the fulness of Christ's grace we all receive, as is written Jn. 1:16. Now other men having Christ's grace cannot merit for others. For it is written (Ezech. 14:20) that if "Noe and Daniel and Job be in the city [Vulg.: 'the midst thereof'] . . . they shall deliver neither son nor daughter; but they shall only deliver their own souls by their justice." Hence Christ could not merit anything for us.
Objection 3: Further, the "reward" that we merit is due "according to justice [Vulg.: 'debt'] and not according to grace," as is clear from Rom. 4:4. Therefore if Christ merited our salvation it follows that our salvation is not by God's grace but by justice, and that He acts unjustly with those whom He does not save, since Christ's merit extends to all. On the contrary, It is written (Rom. 5:18): "As by the offense of one, unto all men to condemnation; so also by the justice of one, unto all men to justification of life." But Adam's demerits reached to the condemnation of others. Much more, therefore, does the merit of Christ reach others.
I answer that, As stated above (Q[8], AA[1],5), grace was in Christ not merely as in an individual, but also as in the Head of the whole Church, to Whom all are united, as members to a head, who constitute one mystical person. And hence it is that Christ's merit extends to others inasmuch as they are His members; even as in a man the action of the head reaches in a manner to all his members, since it perceives not merely for itself alone, but for all the members.
Reply to Objection 1: The sin of an individual harms himself alone; but the sin of Adam, who was appointed by God to be the principle of the whole nature, is transmitted to others by carnal propagation. So, too, the merit of Christ, Who has been appointed by God to be the head of all men in regard to grace, extends to all His members.
Reply to Objection 2: Others receive of Christ's fulness not indeed the fount of grace, but some particular grace. And hence it need not be that men merit for others, as Christ did.
Reply to Objection 3: As the sin of Adam reaches others only by carnal generation, so, too, the merit of Christ reaches others only by spiritual regeneration, which takes place in baptism; wherein we are incorporated with Christ, according to Gal. 3:27, "As many of you as have been baptized in Christ, have put on Christ"; and it is by grace that it is granted to man to be incorporated with Christ. And thus man's salvation is from grace.