Agere Sequitur Esse

Unity and Multiplicity in Christ

Since there are in Christ one person and two natures, we have to examine the relationship between them to determine what is to be spoken of as one, and what is to be spoken of as multiple in Him.

Whatever is multiplied in accord with the diversity of Christ’s natures, must be acknowledged to be plural in Him. -In this connection we must consider, first of all, that nature is received by generation or birth. Consequently, as there are two natures in Christ, there must also be two generations or births: one that is eternal, whereby He received divine nature from His Father, and one that occurred in time, whereby He received human nature from His mother. Likewise, whatever is rightly attributed to God and man as pertaining to nature, must be predicated of Christ in the plural. To God are ascribed intellect and will and their perfections, such as knowledge or wisdom, and charity, and justice. These are also attributed to man as pertaining to human nature; for’ will and intellect are faculties of the soul, and their perfections are wisdom, justice, and the like. Therefore we must acknowledge two intellects in Christ, one human and one divine, and likewise two wills, as well as a double knowledge and charity, namely, the created and the uncreated.

But whatever belongs to the suppositum or hypostasis, must be declared to be one in Christ. Hence if existence is taken in the sense that one suppositum has one existence, we are forced, it appears, to assert that there is but one existence in Christ. Of course, as is evident, when a whole is divided, each separate part has its own proper existence; but according as parts are considered in a whole, they do not have their own existence, for they all exist with the existence of the whole. Therefore, if we look upon Christ as an integral suppositum having two natures, His existence will be but one, just as the suppositum, too, is one.

Since actions belong to supposita, some have thought that, as there is but one suppositum in Christ, so there is only one kind of action in Him. But they did not rightly weigh the matter. For many actions are discerned in any individual, if there are many principles of activity in him. Thus in man the action of understanding differs from the action of sense perception, because of the difference between sense and intellect. Likewise in fire the action of heating differs from the action of soaring upward, because of the difference between heat and lightness. Nature is related to action as its principle. Therefore it is not true that Christ has only one kind of activity because of the one suppositum. Rather, there are two kinds of action in Him, because of the two natures, just as, conversely, there is in the Holy Trinity but one activity of the three persons because of the one nature.

Nevertheless the activity of Christ’s humanity has some part in the activity proper to His divine power. For of all the factors that come together in a suppositum, that which is the most eminent is served by the rest in an instrumental capacity, just as all the lesser faculties of man are instruments of his intellect. Thus in Christ the human nature is held to be, as it were, the organ of His divine nature. But it is clear that an instrument acts in virtue of the principal agent. This is why, in the action of an instrument, we are able to discern not only the power of the instrument, but also that of the principal agent. A chest is made by the action of an axe, but only so far as the axe is directed by the carpenter. In like manner the activity of the human nature in Christ received a certain efficacy from the divine nature, over and above its human power. When Christ touched a leper, the action belonged to His human nature; but the fact that the touch cured the man of his leprosy, is owing to the power of the divine nature. In this way all the human actions and sufferings of Christ were efficacious for our salvation in virtue of His divinity. For this reason Dionysius calls the human activity of Christ “theandric,” that is, divine-human, because actions of this sort proceeded from His human nature in such a way that the power of the divinity was operative in them.

A doubt is raised by some theologians concerning sonship, whether there is only one filiation in Christ because of the oneness of the suppositum, or two filiations because of the duality of His nativity. It may seem that there are two filiations; for when a cause is multiplied the effect is multiplied, and the cause of sonship is nativity. Since, therefore, there are two nativities of Christ, the consequence may seem to follow that there are also two filiations.

This view is not rejected by the fact that filiation is a personal relation, that is, that it constitutes a person. In the case of Christ, this is true of the divine filiation; the human filiation does not constitute a person, but comes to a person already constituted as such. In the same way there is no reason why one man should not be related to his father and mother by a single filiation; he is born of both parents by the same nativity. Wherever the cause of a relation is the same, the relation is in reality but one, even though it may have many respects. There is nothing to prevent a thing from having a reference to another thing, even though no relation is really in it. Thus the knowable is referred to knowledge, although no relation exists in it. So, too, there is no reason why a single real relation should not have a number of respects. just as a relation depends on its cause for its existence as a certain thing, so it also depends on its cause for the fact that it is one or multiple. Therefore, since Christ does not proceed from His Father and His mother by the same nativity, there may seem to be in Him two real filiations because of the two nativities.

But there is one reason why several real filiations cannot be attributed to Christ. Not everything that is generated by another can be called a son; only a complete suppositum can be called a son. Not a man’s hand or foot, but the whole individual, Peter or John, is called son. Hence the proper subject of filiation is the suppositum itself. But we have shown that the only suppositum in Christ is the uncreated suppositum, which cannot receive any real relation beginning in time; as we intimated above, every relation of God to creatures is purely mental. Consequently the filiation whereby the eternal suppositum of the Son is related to His virgin mother cannot be a real relation, but must be a purely mental relation.

However, this does not prevent Christ from being really and truly the Son of His virgin mother, because He was truly born of her. In the same way God is really and truly the Lord of His creatures, because He possesses real power to coerce them; yet the relation of dominion is attributed to God only by a mental operation. Of course, if there were several supposita in Christ, as some theologians have taught, there would be nothing to keep us from admitting two filiations in Christ, for in that case the created suppositum would be subject to temporal sonship.

Reference

St. Thomas Aquinas. (1265-1274). Compendium Theologiae: Unity and Multiplicity in Christ, trans. by Cyril Vollert. St. Louis & London: B. Herder Book Co., 1947