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, Matt. 26:38: "My soul is sorrowful even unto death"; and John 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 (Isa. 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 Obj. 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 Isa. 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 Obj. 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 Obj. 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. _______________________
FOURTH ARTICLE [II-II, Q. 5, Art. 4]
Whether the Son of God Assumed a Human Mind or Intellect?
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.
Obj. 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 John 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.
Obj. 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 (Luke 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 (John 17): 'I lay down My soul [Douay: 'life'] that I may take it again.' And He proves that He has an intellect, saying (Matt. 11:29): 'Learn of Me, because I am meek and humble of heart.' And God says of Him by the prophet (Isa. 52:13): 'Behold my servant shall understand.'"