Finally, we get tot the meat of the Incarnation.
1 Now, to get at the solution of these objections, one must begin somewhat more fundamentally. Since Eutyches set it down that the union of God and man took place in nature; Nestorius, that it was neither in nature nor in person; but the Catholic faith holds this: that the union takes place in Person, not in nature—it seems necessary to know first what it is “to be made one in nature,” and what it is “to be made one in person.”
2 Grant, then, that nature is a word used in many ways: the generation of living things, and the principle of generation and of motion, and the matter and the form are all called nature. Sometimes, also, nature is said of the what-it-is of a thing, which includes the things that bear on the integrity of the species; in this way we say that human nature is common to all men, and say the same in all other cases. Those things, therefore, are made one in nature from which the integrity of a species is established; just as the soul and human body are made one to establish the species of the animal, so, universally, whatever the parts of a species are.
3 Of course, it is impossible that to a species already established in its integrity something extrinsic be united for the unity of its nature without losing the species. For, since species are like numbers, and in these any unity added or subtracted makes the species vary, if to a species already perfected something be added, necessarily it is now another species; thus, if to animate substance one adds only sensible, one will have another species, for animal and plant are different species.
It does happen, nonetheless, that one finds something which is not integral to the species; in an individual included under that species—white and dressed, for instance, in Socrates or in Plato, or a sixth finger, or something of the sort.
Hence, nothing prevents some things being made one in the individual which are not united in one integrity of species; thus, human nature and whiteness and music in Socrates; and things of this kind are united and are called “one by subject.” Now, the individual in the genus of substance is called hypostasis, and even in rational substances is called person; therefore, all things such as those mentioned are suitably said to be, united “in the hypostasis” or even “in the person.” Clearly, then, nothing prevents some things not united in nature from being united in hypostasis or person.
Notes Well, that is clever enough.
4 But when the heretics heard that in Christ a union of God and man took place, they approached the exposition of this point in contrary ways, but neglected the way of the truth. For some thought of this union after the mode of things united into one nature: so Arius and Apollinaris, holding that the Word stood to the body of Christ as soul or as mind, and so Eutyches, who held that before the Incarnation there were two natures of God and man, but after the Incarnation only one.
But this opinion entails an impossibility. It is clear that the nature of the Word is from eternity most perfect in its integrity, and cannot be corrupted or changed in any way. So it is impossible for anything extrinsic to the divine nature, such as a human nature or any part of it, to come into a union of nature with it.
5 But others, seeing the impossibility of this position, went off on a contrary road. Now, the things which accrue to one having a nature, but do not belong to the integrity of that nature, seem either to be accidents—say, whiteness and music; or to stand in an accidental relation—say, a ring, a garment, a house, and the like.
Of course, they weighed this: Since the human nature accrues to the Word of God without belonging to the integrity of His nature, it is necessary (so they thought) that the human nature have an accidental union with the Word. To be sure, it clearly cannot be in the Word as an accident: both because God is not susceptible to an accident (as was previously proved); and because human nature, being in the genus of substance, cannot be the accident of anything.
Hence there appeared to be this remaining: Human nature accrues to the Word, not as an accident, but as a thing accidentally related to the Word. Nestorius, then, held that the human nature of Christ stood to the Word as a kind of temple, so that only by indwelling was the union of the Word to the human nature to be understood. And because a temple possesses its individuation apart from him who dwells in the temple, and the individuation suitable to human nature is personality, this was left: that the personality of the human nature was one, and that of the Word another. Thus, the Word and that man were two persons.
6 To be sure, others wished to avoid this awkwardness. So, regarding the human nature they introduced a disposition such that personality could not be properly suitable to it. They said that the soul and the body, in which the integrity of human nature consists, were so assumed by the Word that the soul was not united to the body to establish any substance, lest they be forced to say that the substance so established fulfilled the account of person. But they held the union of the Word to soul and body to be like a union to things in an accidental relation, for instance, of the clothed to his clothes. In this they were somehow imitating Nestorius.
7 Now, with these accounts set aside by the foregoing, it must be laid down that the union of the Word and the man was such that one nature was not breathed together out of two; and that the union of the Word to the human nature was not like that of a substance—a man, say—to those externals which are accidentally related to him, like a house and a garment. But let the Word be set down as subsisting in a human nature as in one made His very own by the Incarnation; and in consequence that body is truly the body of the Word of God, and the soul in like manner, and the Word of God is truly man.
8 And although to explain this union perfectly is beyond man’s strength, nonetheless, in accord with our measure and power, we will try to say something “for the upbuilding of the faith” (cf. Eph. 4:29), so that concerning this mystery the Catholic faith may be defended from the infidels.
9 Now, in all created things nothing is found so like this union as the union of soul to body. And the likeness would be greater, as Augustine also says, in Against Felician, if there were one intellect in all men. So some have held, and according to them one ought to say that the pre-existing intellect is in such wise united anew to a man’s conception that from each of these two a new person is made, just as we hold that the pre-existing Word is united to the human nature in a unity of person. Accordingly, and by reason of the likeness of these two unions, Athanasius says in the Creed: “as the rational soul and flesh are one man, so God and man are one Christ.”
10 However, since the rational soul is united to the body both as to matter and as to an instrument, there cannot be a likeness so far as the first mode of union is concerned, for thus from God and man one nature would be made, since the matter and the form properly establish the nature of a species. Therefore, what is left is to look upon the likeness so far as the soul is united to the body as an instrument. With this, also, there is the concordance of the ancient Doctors, who held that the human nature in Christ was “a kind of organ of the divinity,” just as the body is held to be an organ of the soul.
11 Now, the body and its parts are the organ of the soul in one fashion; external instruments in quite another. For this axe is not the soul’s very own instrument, as this hand is, for by an axe many can operate, but this hand is deputy to this soul in its very own operation. For this reason the hand is an instrument of the soul united to it and its very own, but the axe is an instrument both external and common.
This is the way, then, in which even the union of God and man can be considered. For all men are related to God as instruments of a sort, and by these He works: “for it is God who works in you both to will and to accomplish according to His good will” (Phil. 2:3), as the Apostle says. But other men are related to God as extrinsic and separated instruments, so to say; for God does not move them only to operations which are His very own, but to the operations common to every rational nature, to understand the truth, for example, to love the good, to do what is just.
But the human nature in Christ is assumed with the result that instrumentally He performs the things which are the proper operation of God alone: to wash away sins, for example, to enlighten minds by grace, to lead into the perfection of eternal life. The human nature of Christ, then, is compared to God as a proper and conjoined instrument is compared, as the hand is compared to the soul.
12 Nor is there departure from the course of natural things because one thing is by nature the proper instrument of another, and this other is not its form. For the tongue, so far as it is the instrument of speech, is the intellect’s very own organ; and the intellect is nevertheless, as the Philosopher proves, not the act of any part of the body.
In like manner, too, one finds an instrument which does not pertain to the nature of the species, which is, nevertheless, on the material side fitted to this individual; a sixth finger, for example, or something of the sort. Therefore, nothing prevents our putting the union of the human nature to the Word in this way: that the human nature be, so to speak, an instrument of the Word—not a separated, but a conjoined, instrument; and the human nature, nonetheless, does not belong to the nature of the Word, and the Word is not its form; nevertheless the human nature belongs to His person.
13 But the examples mentioned have not been set down so that one should look in them for an all-round likeness; for one should understand that the Word of God was able to be much more sublimely and more intimately united to human nature than the soul to its very own instrument of whatever sort, especially since He is said to be united to the entire human nature with the intellect as medium. And although the Word of God by His power penetrates all things, conserving all, that is, and supporting all, it is to the intellectual creatures, who can properly enjoy the Word and share with Him, that from a kind of kinship of likeness He can be both more eminently and more ineffably united.