Summa Theologica, by St. Thomas Aquinas, [1947], at sacred-texts.com
We must now consider the assumption of the parts of human nature; and under this head there are four points of inquiry:
(1) Whether the Son of God ought to have assumed a true body?
(2) Whether He ought to have assumed an earthly body, i.e. one of flesh and blood?
(3) Whether He ought to have assumed a soul?
(4) Whether He ought to have assumed an intellect?
Objection 1: It would seem that the Son of God did not assume a true body. For it is written (Phil. 2:7), that He was "made in the likeness of men." But what is something in truth is not said to be in the likeness thereof. Therefore the Son of God did not assume a true body.
Objection 2: Further, the assumption of a body in no way diminishes the dignity of the Godhead; for Pope Leo says (Serm. de Nativ.) that "the glorification did not absorb the lesser nature, nor did the assumption lessen the higher." But it pertains to the dignity of God to be altogether separated from bodies. Therefore it seems that by the assumption God was not united to a body.
Objection 3: Further, signs ought to correspond to the realities. But the apparitions of the Old Testament which were signs of the manifestation of Christ were not in a real body, but by visions in the imagination, as is plain from Is. 60:1: "I saw the Lord sitting," etc. Hence it would seem that the apparition of the Son of God in the world was not in a real body, but only in imagination.
On the contrary, Augustine says (Qq. lxxxiii, qu. 13): "If the body of Christ was a phantom, Christ deceived us, and if He deceived us, He is not the Truth. But Christ is the Truth. Therefore His body was not a phantom." Hence it is plain that He assumed a true body.
I answer that, As is said (De Eccles. Dogm. ii). The Son of God was not born in appearance only, as if He had an imaginary body; but His body was real. The proof of this is threefold. First, from the essence of human nature to which it pertains to have a true body. Therefore granted, as already proved (Q[4], A[1]), that it was fitting for the Son of God to assume human nature, He must consequently have assumed a real body. The second reason is taken from what was done in the mystery of the Incarnation. For if His body was not real but imaginary, He neither underwent a real death, nor of those things which the Evangelists recount of Him, did He do any in very truth, but only in appearance; and hence it would also follow that the real salvation of man has not taken place; since the effect must be proportionate to the cause. The third reason is taken from the dignity of the Person assuming, Whom it did not become to have anything fictitious in His work, since He is the Truth. Hence our Lord Himself deigned to refute this error (Luke 24:37, 39), when the disciples, "troubled and frighted, supposed that they saw a spirit," and not a true body; wherefore He offered Himself to their touch, saying: "Handle, and see; for a spirit hath not flesh and bones, as you see Me to have."
Reply to Objection 1: This likeness indicates the truth of the human nature in Christ---just as all that truly exist in human nature are said to be like in species---and not a mere imaginary likeness. In proof of this the Apostle subjoins (Phil. 2:8) that He became "obedient unto death, even to the death of the cross"; which would have been impossible, had it been only an imaginary likeness.
Reply to Objection 2: By assuming a true body the dignity of the Son of God is nowise lessened. Hence Augustine [*Fulgentius] says (De Fide ad Petrum ii): "He emptied Himself, taking the form of a servant, that He might become a servant; yet did He not lose the fulness of the form of God." For the Son of God assumed a true body, not so as to become the form of a body, which is repugnant to the Divine simplicity and purity---for this would be to assume a body to the unity of the nature, which is impossible, as is plain from what has been stated above (Q[2], A[1]): but, the natures remaining distinct, He assumed a body to the unity of Person.
Reply to Objection 3: The figure ought to correspond to the reality as regards the likeness and not as regards the truth of the thing. For if they were alike in all points, it would no longer be a likeness but the reality itself, as Damascene says (De Fide Orth. iii, 26). Hence it was more fitting that the apparitions of the old Testament should be in appearance only, being figures; and that the apparition of the Son of God in the world should be in a real body, being the thing prefigured by these figures. Hence the Apostle says (Col. 2:17): "Which are a shadow of things to come, but the body is Christ's."
Objection 1: It would seem that Christ had not a carnal or earthly, but a heavenly body. For the Apostle says (1 Cor. 15:41): "The first man was of the earth, earthy; the second man from heaven, heavenly." But the first man, i.e. Adam, was of the earth as regards his body, as is plain from Gn. 1. Therefore the second man, i.e. Christ, was of heaven as regards the body.
Objection 2: Further, it is said (1 Cor. 15:50): "Flesh and blood shall not [Vulg.: 'cannot'] possess the kingdom of God." But the kingdom of God is in Christ chiefly. Therefore there is no flesh or blood in Him, but rather a heavenly body.
Objection 3: Further, whatever is best is to be attributed to God. But of all bodies a heavenly body is the best. Therefore it behooved Christ to assume such a body.
On the contrary, our Lord says (Lk. 24:39): "A spirit hath not flesh and bones, as you see Me to have." Now flesh and bones are not of the matter of heavenly bodies, but are composed of the inferior elements. Therefore the body of Christ was not a heavenly, but a carnal and earthly body.
I answer that, By the reasons which proved that the body of Christ was not an imaginary one, it may also be shown that it was not a heavenly body. First, because even as the truth of the human nature of Christ would not have been maintained had His body been an imaginary one, such as Manes supposed, so likewise it would not have been maintained if we supposed, as did Valentine, that it was a heavenly body. For since the form of man is a natural thing, it requires determinate matter, to wit, flesh and bones, which must be placed in the definition of man, as is plain from the Philosopher (Metaph. vii, 39). Secondly, because this would lessen the truth of such things as Christ did in the body. For since a heavenly body is impassible and incorruptible, as is proved De Coel. i, 20, if the Son of God had assumed a heavenly body, He would not have truly hungered or thirsted, nor would he have undergone His passion and death. Thirdly, this would have detracted from God's truthfulness. For since the Son of God showed Himself to men, as if He had a carnal and earthly body, the manifestation would have been false, had He had a heavenly body. Hence (De Eccles. Dogm. ii) it is said: "The Son of God was born, taking flesh of the Virgin's body, and not bringing it with Him from heaven."
Reply to Objection 1: Christ is said in two ways to have come down from heaven. First, as regards His Divine Nature; not indeed that the Divine Nature ceased to be in heaven, but inasmuch as He began to be here below in a new way, viz. by His assumed. nature, according to Jn. 3:13: "No man hath ascended into heaven, but He that descended from heaven, the Son of Man, Who is in heaven."
Secondly, as regards His body, not indeed that the very substance of the body of Christ descended from heaven, but that His body was formed by a heavenly power, i.e. by the Holy Ghost. Hence Augustine, explaining the passage quoted, says (Ad Orosium [*Dial. Qq. lxv, qu. 4, work of an unknown author]): "I call Christ a heavenly man because He was not conceived of human seed." And Hilary expounds it in the same way (De Trin. x).
Reply to Objection 2: Flesh and blood are not taken here for the substance of flesh and blood, but for the corruption of flesh, which was not in Christ as far as it was sinful; but as far as it was a punishment; thus, for a time, it was in Christ, that He might carry through the work of our redemption.
Reply to Objection 3: It pertains to the greatest glory of God to have raised a weak and earthly body to such sublimity. Hence in the General Council of Ephesus (P. II, Act. I) we read the saying of St. Theophilus: "Just as the best workmen are esteemed not merely for displaying their skill in precious materials, but very often because by making use of the poorest . . . lay and commonest earth, they show the power of their craft; so the best of all workmen, the Word of God, did not come down to us by taking a heavenly body of some most precious matter, but shewed the greatness of His skill in clay."
Objection 1: It would seem that the Son of God did not assume a soul. For John has said, teaching the mystery of the Incarnation (Jn. 1:14): "The Word was made flesh"---no mention being made of a soul. Now it is not said that "the Word was made flesh" as if changed to flesh, but because He assumed flesh. Therefore He seems not to have assumed a soul.
Objection 2: Further, a soul is necessary to the body, in order to quicken it. But this was not necessary for the body of Christ, as it would seem, for of the Word of God it is written (Ps. 35:10): Lord, "with Thee is the fountain of life." Therefore it would seem altogether superfluous for the soul to be there, when the Word was present. But "God and nature do nothing uselessly," as the Philosopher says (De Coel. i, 32; ii, 56). Therefore the Word would seem not to have assumed a soul.
Objection 3: Further, by the union of soul and body is constituted the common nature, which is the human species. But "in the Lord Jesus Christ we are not to look for a common species," as Damascene says (De Fide Orth. iii, 3). Therefore He did not assume a soul.
On the contrary, Augustine says (De Agone Christ. xxi): "Let us not hearken to such as say that only a human body was assumed by the Word of God; and take 'the Word was made flesh' to mean that the man had no soul nor any other part of a man, save flesh."
I answer that, As Augustine says (De Haeres. 69,55), it was first of all the opinion of Arius and then of Apollinaris that the Son of God assumed only flesh, without a soul, holding that the Word took the place of a soul to the body. And consequently it followed that there were not two natures in Christ, but only one; for from a soul and body one human nature is constituted. But this opinion cannot hold, for three reasons. First, because it is counter to the authority of Scripture, in which our Lord makes mention of His soul, Mat. 26:38: "My soul is sorrowful even unto death"; and Jn. 10:18: "I have power to lay down My soul [animam meam: Douay: 'My life']." But to this Apollinaris replied that in these words soul is taken metaphorically, in which way mention is made in the Old Testament of the soul of God (Is. 1:14): "My soul hateth your new moons and your solemnities." But, as Augustine says (Qq. lxxxiii, qu. 80), the Evangelists relate how Jesus wondered, was angered, sad, and hungry. Now these show that He had a true soul, just as that He ate, slept and was weary shows that He had a true human body: otherwise, if these things are a metaphor, because the like are said of God in the Old Testament, the trustworthiness of the Gospel story is undermined. For it is one thing that things were foretold in a figure, and another that historical events were related in very truth by the Evangelists. Secondly, this error lessens the utility of the Incarnation, which is man's liberation. For Augustine [*Vigilius Tapsensis] argues thus (Contra Felician. xiii): "If the Son of God in taking flesh passed over the soul, either He knew its sinlessness, and trusted it did not need a remedy; or He considered it unsuitable to Him, and did not bestow on it the boon of redemption; or He reckoned it altogether incurable, and was unable to heal it; or He cast it off as worthless and seemingly unfit for any use. Now two of these reasons imply a blasphemy against God. For how shall we call Him omnipotent, if He is unable to heal what is beyond hope? Or God of all, if He has not made our soul. And as regards the other two reasons, in one the cause of the soul is ignored, and in the other no place is given to merit. Is He to be considered to understand the cause of the soul, Who seeks to separate it from the sin of wilful transgression, enabled as it is to receive the law by the endowment of the habit of reason? Or how can His generosity be known to any one who says it was despised on account of its ignoble sinfulness? If you look at its origin, the substance of the soul is more precious than the body: but if at the sin of transgression, on account of its intelligence it is worse than the body. Now I know and declare that Christ is perfect wisdom, nor have I any doubt that He is most loving; and because of the first of these He did not despise what was better and more capable of prudence; and because of the second He protected what was most wounded." Thirdly, this position is against the truth of the Incarnation. For flesh and the other parts of man receive their species through the soul. Hence, if the soul is absent, there are no bones nor flesh, except equivocally, as is plain from the Philosopher (De Anima ii, 9; Metaph. vii, 34).
Reply to Objection 1: When we say, "The Word was made flesh," "flesh" is taken for the whole man, as if we were to say, "The Word was made man," as Is. 40:5: "All flesh together shall see that the mouth of the Lord hath spoken." And the whole man is signified by flesh, because, as is said in the authority quoted, the Son of God became visible by flesh; hence it is subjoined: "And we saw His glory." Or because, as Augustine says (Qq. lxxxiii, qu. 80), "in all that union the Word is the highest, and flesh the last and lowest. Hence, wishing to commend the love of God's humility to us, the Evangelist mentioned the Word and flesh, leaving the soul on one side, since it is less than the Word and nobler than flesh." Again, it was reasonable to mention flesh, which, as being farther away from the Word, was less assumable, as it would seem.
Reply to Objection 2: The Word is the fountain of life, as the first effective cause of life; but the soul is the principle of the life of the body, as its form. Now the form is the effect of the agent. Hence from the presence of the Word it might rather have been concluded that the body was animated, just as from the presence of fire it may be concluded that the body, in which fire adheres, is warm.
Reply to Objection 3: It is not unfitting, indeed it is necessary to say that in Christ there was a nature which was constituted by the soul coming to the body. But Damascene denied that in Jesus Christ there was a common species, i.e. a third something resulting from the Godhead and the humanity.
Objection 1: It would seem that the Son of God did not assume a human mind or intellect. For where a thing is present, its image is not required. But man is made to God's image, as regards his mind, as Augustine says (De Trin. xiv, 3,6). Hence, since in Christ there was the presence of the Divine Word itself, there was no need of a human mind.
Objection 2: Further, the greater light dims the lesser. But the Word of God, Who is "the light, which enlighteneth every man that cometh into this world," as is written Jn. 1:9, is compared to the mind as the greater light to the lesser; since our mind is a light, being as it were a lamp enkindled by the First Light (Prov. 20:27): "The spirit of a man is the lamp of the Lord." Therefore in Christ Who is the Word of God, there is no need of a human mind.
Objection 3: Further, the assumption of human nature by the Word of God is called His Incarnation. But the intellect or human mind is nothing carnal, either in its substance or in its act. for it is not the act of a body, as is proved De Anima iii, 6. Hence it would seem that the Son of God did not assume a human mind.
On the contrary, Augustine [*Fulgentius] says (De Fide ad Petrum xiv): "Firmly hold and nowise doubt that Christ the Son of God has true flesh and a rational soul of the same kind as ours, since of His flesh He says (Lk. 24:39): 'Handle, and see; for a spirit hath not flesh and bones, as you see Me to have.' And He proves that He has a soul, saying (Jn. 10:17): 'I lay down My soul [Douay: 'life'] that I may take it again.' And He proves that He has an intellect, saying (Mat. 11:29): 'Learn of Me, because I am meek and humble of heart.' And God says of Him by the prophet (Is. 52:13): 'Behold my servant shall understand.'"
I answer that, As Augustine says (De Haeres. 49,50), "the Apollinarists thought differently from the Catholic Church concerning the soul of Christ, saying with the Arians, that Christ took flesh alone, without a soul; and on being overcome on this point by the Gospel witness, they went on to say that the mind was wanting to Christ's soul, but that the Word supplied its place." But this position is refuted by the same arguments as the preceding. First, because it runs counter to the Gospel story, which relates how He marveled (as is plain from Mat. 8:10). Now marveling cannot be without reason, since it implies the collation of effect and cause, i.e. inasmuch as when we see an effect and are ignorant of its cause, we seek to know it, as is said Metaph. i, 2. Secondly, it is inconsistent with the purpose of the Incarnation, which is the justification of man from sin. For the human soul is not capable of sin nor of justifying grace except through the mind. Hence it was especially necessary for the mind to be assumed. Hence Damascene says (De Fide Orth. iii, 6) that "the Word of God assumed a body and an intellectual and rational soul," and adds afterwards: "The whole was united to the whole, that He might bestow salvation on me wholly; for what was not assumed is not curable." Thirdly, it is against the truth of the Incarnation. For since the body is proportioned to the soul as matter to its proper form, it is not truly human flesh if it is not perfected by human, i.e. a rational soul. And hence if Christ had had a soul without a mind, He would not have had true human flesh, but irrational flesh, since our soul differs from an animal soul by the mind alone. Hence Augustine says (Qq. lxxxiii, qu. 80) that from this error it would have followed that the Son of God "took an animal with the form of a human body," which, again, is against the Divine truth, which cannot suffer any fictitious untruth.
Reply to Objection 1: Where a thing is by its presence, its image is not required to supply the place of the thing, as where the emperor is the soldiers do not pay homage to his image. Yet the image of a thing is required together with its presence, that it may be perfected by the presence of the thing, just as the image in the wax is perfected by the impression of the seal, and as the image of man is reflected in the mirror by his presence. Hence in order to perfect the human mind it was necessary that the Word should unite it to Himself.
Reply to Objection 2: The greater light dims the lesser light of another luminous body; but it does not dim, rather it perfects the light of the body illuminated---at the presence of the sun the light of the stars is put out, but the light of the air is perfected. Now the intellect or mind of man is, as it were, a light lit up by the light of the Divine Word; and hence by the presence of the Word the mind of man is perfected rather than overshadowed.
Reply to Objection 3: Although the intellective power is not the act of a body, nevertheless the essence of the human soul, which is the form of the body, requires that it should be more noble, in order that it may have the power of understanding; and hence it is necessary that a better disposed body should correspond to it.