Commentaria in Summam contra Gentiles, Liber IV

Having set down the objections against the mystery of the Incarnation, St. Thomas sets forth certain points beforehand for their solution, in order that the solution itself may become more evident ¹.

I. The first point that he sets forth beforehand ² is how one must understand the incarnation of the Son of God as to its being made in person, against Nestorius; and not in nature, against Eutyches.

And he says first that, since the name "nature," besides other meanings, is said of the what-a-thing-is, containing those things that pertain to the integrity of the species, those things are united in nature from which the integrity of some species is constituted; just as soul and human body are united to constitute the species of animal, and universally whatever are parts of a species.

He says secondly that it is indeed impossible for anything extraneous to be united into the unity of nature with any species already constituted in its integrity, unless the species is destroyed: because species are like numbers, in which any unit added or subtracted changes the species, as is evident if sensible is added to animate substance. It happens nevertheless that that which is not of the integrity of the species is found in another individual contained under that species: such as white and clothed in Socrates, or a sixth finger, and the like. Whence nothing prevents certain things from being united in an individual that are not united in one integrity of a species. And because an individual in the genus of substance is called a hypostasis, while in rational substances it is called a person, suitably all things of this sort are said to be united according to hypostasis, or also according to person. From which it is clear that nothing prevents certain things not united according to nature from being united according to hypostasis or person.

It must be noted that the integrity of a species is twofold: namely, essential and quantitative. And therefore something is said in two ways not to be of the integrity of the species: either, namely, because it is not of its essence; or because it does not pertain to its quantitative perfection. So that St. Thomas may encompass both integrities, he gives the example of white and clothed in Socrates, which are not of the essential integrity of man; and of a sixth finger on the hand, which does not pertain to the quantitative integrity of man.

II. He says thirdly that the heretics, hearing that the union of God and man had been made in Christ, set out on contrary paths to explain this. For Arius and Apollinaris, estimating this union after the manner of those things that are united into one nature, said that the Word of God was to the body of Christ in place of a soul or in place of a mind. Eutyches, on the other hand, posited two natures indeed of God and man before the incarnation, but one after the incarnation. Against them is the fact that, since the nature of the Word is most perfect in its integrity from eternity, nor can it be corrupted or changed at all, it is impossible for anything extrinsic to come to it into its unity.

Others, however, seeing the impossibility of this position, since human nature comes to the Word of God and does not pertain to his integrity, thought that human nature had an accidental union indeed with the Word, yet was not in him as an accident: both because God is not receptive of an accident, and because human nature, since it is of the genus of substance, can be the accident of nothing. On account of which Nestorius posited that human nature is related to the Word as a kind of temple: and consequently, because a temple has its individuation separately from the one who inhabits the temple, while the individuation proper to human nature is its personality (understand this of the individuation of a singular subsisting substance), it remained that there was one personality of the human nature and another of the Word. — Wishing to avoid this unfitting consequence, others said that in Christ there was not some substance constituted from soul and body, lest they be forced to say that it had the character of a person; but they posited the union of the Word to the soul and body as to things that are accidentally related, for instance, of one clothed to clothing, imitating Nestorius in a certain manner in this.

It must be noted that St. Thomas does not say that they simply imitate Nestorius, but in a certain manner, that is, as to something. For although they imitated Nestorius in this, that they said the Word of God was united to soul and body in an accidental manner, they differed from him in this, that they did not posit that some nature was constituted from soul and body, whereas Nestorius posited this.

III. He says fourthly that in such a union of the Word of God and man, one nature was neither blended out of two natures; nor was the Word united to the human nature as to a substance accidentally related to him: but he is posited to subsist in it, so that that body is truly the body of the Word of God, and similarly the soul, and the Word of God is truly man.

He says fifthly that, although this union cannot be explained by man, yet, that it may be spoken of according to our manner and capacity, nothing is found in all created things so like to this thing as the union of the soul to the body. And the likeness would be greater, as Augustine says, Contra Felicianum, if there were one intellect in all men, as certain thinkers have posited. For the pre-existing intellect would have to be newly united to the conceived man in such a way that one person would be made from both, just as we posit that the Word pre-existing to the human nature is united into one person. On account of this Athanasius says in the Creed: As from the soul, etc.

It must be noted that the likeness of that union would therefore be greater if there were one intellect in all men than it is in the union of the soul to the body, because in the latter one thing is not united to another pre-existing thing, as happens in the union of the Word with human nature; but indeed, if there were one intellect of all men, one thing would be united to another pre-existing thing.

It must be observed secondly that, if there were one intellect in all men, one person of intellect and man would therefore be made through the union of the intellect to the conceived man, because the operation of the intellect would be attributed to the man. For the man would be said to understand from the union with such an intellect. Which surely could not be unless there were one person of the man and the intellect: for the proper operation of one person cannot be attributed to another person, just as the proper operation of Socrates cannot be attributed to Plato.

IV. He says sixthly that, since the rational soul is united to the body both as to matter and as to an instrument, there cannot be a likeness as to the first mode of union: because thus one nature would be made from God and man, as from matter and form. But there is a likeness as to the second mode. With which the sayings of the ancient Doctors also agree, who say that the human nature in Christ is an organ of the divinity, just as the body also is posited as an organ of the soul.

He says seventhly that, just as the body and its parts are an organ of the soul in one way, and external instruments in another way—for through this pickaxe many can work, but this hand is assigned to the proper operation of this soul—so, although all men are compared to God as instruments by which he works, as is clear from the Apostle, Phil. 2, yet other men are as it were separate instruments, since they are moved by God not to operations proper to themselves alone, but to operations common to every rational nature, such as to understand truth, to love good things, and the like; whereas the human nature in Christ is a conjoined instrument of God, and was assumed so that it might operate instrumentally those things that are the proper operations of God alone, such as to cleanse sins, to illumine minds through grace, and the like.

Concerning what was said, that other men are moved by God only to operations common to every rational nature, but not to those that are proper to God, a doubt arises. For to perform miracles is proper to God; and yet this belongs to other men instrumentally, as was shown above ³. Therefore, etc.

It can be answered to this that the statement of St. Thomas is understood to mean that other men are not moved to operations that are proper to God through a divine power existing in them by way of a habit, but only by way of a transient passion, as was said where the operation of miracles was treated ⁴. But the human nature of Christ is moved to perform divine works from a divine power conjoined to it as it were in a habitual manner, that is, permanently, and not only by way of something transient: just as the power of the soul is always conjoined to the hand in some manner.

He says eighthly that it does not disagree with the custom of natural things that something should naturally be the proper instrument of something, which yet is not its form: as is clear of the tongue with respect to the intellect. Some instrument is also found that does not pertain to the nature of the species, and yet on the part of matter is fitting to this individual: such as a sixth finger on the hand. Thus therefore nothing prevents human nature from being as it were a conjoined instrument of the Word, and yet neither pertaining to the nature of the Word, nor the Word being its form, yet pertaining to his person.

He says lastly that an all-embracing likeness must not be required in the aforesaid examples: because it must be understood that the Word of God could be united much more sublimely and intimately to human nature than the soul to any proper instrument whatever: especially since he is said to be conjoined to the whole human nature through the mediation of the intellect. And although by his power he penetrates all things, yet to intellectual creatures, who can fully enjoy him and be partakers of him, he can be united more eminently and ineffably.

V. Concerning that proposition, the Word of God is said to be conjoined to the whole human nature through the mediation of the intellect, it must be noted that by "whole human nature" St. Thomas understands only the totality of Christ's humanity according to perfection, but not the totality of humanity according to the universality of predication. But the Word is said to be conjoined to it through the mediation of the spirit, according to the mind of Augustine, in the book De Agone Christiano ⁵, and of Damascene, in Book III ⁶, by reason indeed of dignity, inasmuch as among the other parts of the soul it is higher, and more worthy, and more like to God, on account of which the intellect is said to be a medium according to dignity between the Word of God and the soul as it has other inferior powers; but by reason of congruity, because the soul is not assumable according to congruity except through this, that it is capable of God, existing according to his image, which belongs to it through the intellect; for the Word is said to be united to it through the mediation of the intellect in this way, because human nature does not have congruity to being assumable by the Word before other natures, except because it has an intellect. St. Thomas thoroughly treats of this in Tertia, q. 6, a. 2; and in Third Book of the Sentences, d. 2, q. 2, a. 1. For he wishes to argue here that the Word of God could be united much more sublimely to human nature than the soul to any instrument whatever, by this reason: that, since he is united to human nature through the mediation of the intellect, and is more particularly united to intellectual substances than to other creatures, it is also not unfitting if he can be united in a certain more excellent mode to human nature.

VI. Concerning what was said ⁷, that the Word is united to human nature as to a conjoined instrument, a doubt arises. For it does not appear how he is conjoined to human nature so that it can be said to be a conjoined instrument of the Word, if neither the Word is the form of the human nature; nor conversely the human nature of the Word; nor does it even pertain to the nature of the Word. For a conjoined instrument of something must be united with it in something: for the tongue, which is the proper instrument of the intellect, is united with it in the soul, inasmuch as the intellect is rooted in the essence of the soul, and the soul is the form of the tongue. But it is not apparent in what human nature is united with the Word, if the aforesaid modes of union are excluded.

2. It is answered, and said first, that these must indeed be united and undivided in something, if one ought to be the conjoined instrument of the other. Nevertheless it is most difficult for this union to be explained by us, since nothing altogether like it is found in creatures, from which we receive cognition.

It is said secondly, in accordance with the aforesaid points ⁸, that the divine and human nature are united and undivided in one person, inasmuch as one person, existing most simple, subsists in each nature. Nor is it necessary that of those things that are united in one person, one be the form of the other: as is clear of music and logic, which are united in Socrates. But the human nature and the person are united, and are undivided, in one esse, inasmuch as the human nature is drawn to the esse of the divine person, so that there is the same esse both of the divine person and of the human nature. Nor is it even necessary that things that are undivided in one esse be so related that one is the form of the other: for the hand and foot of Socrates agree in one esse, and yet neither is the form of the other. Similarly, when a foot previously separated is drawn to the esse of an animal through conjunction, the animal does not inform the foot, but rather the form giving esse to the animal informs the supposit of the foot.

3. But if it is argued, as Aureoli argues, in Capreolus, Third Book of the Sentences, d. 6 ⁹, because esse is the act of essence; but the divine esse does not actuate the human nature; and thus it does not seem that the human nature and the divine person are united in the one esse of the divine supposit: — it is said, as was also said above ¹⁰, that esse is not the act of essence as of that which formally exists, but as of that in which something exists; but it is the act of the supposit as of that which formally exists. Whence it is not necessary that the divine esse actuate the human nature per se and primarily, in order for it to be undivided with the person of the Word in that esse: but it suffices that the divine supposit be the supposit of the human nature; because then the divine esse primarily and per se actuates the supposit; but secondarily and through another it is said to actuate the human nature, inasmuch as it actuates its supposit, which subsists in that human nature; nor does this detract in any part from the divine esse.