Summa Theologica, by St. Thomas Aquinas, [1947], at sacred-texts.com
We must now consider the order of the foregoing assumption, and under this head there are six points of inquiry:
(1) Whether the Son of God assumed flesh through the medium of the soul?
(2) Whether He assumed the soul through the medium of the spirit or mind?
(3) Whether the soul was assumed previous to the flesh?
(4) Whether the flesh of Christ was assumed by the Word previous to being united to the soul?
(5) Whether the whole human nature was assumed through the medium of the parts?
(6) Whether it was assumed through the medium of grace?
Objection 1: It would seem that the Son of God did not assume flesh through the medium of the soul. For the mode in which the Son of God is united to human nature and its parts, is more perfect than the mode whereby He is in all creatures. But He is in all creatures immediately by essence, power and presence. Much more, therefore, is the Son of God united to flesh without the medium of the soul.
Objection 2: Further, the soul and flesh are united to the Word of God in unity of hypostasis or person. But the body pertains immediately to the human hypostasis or person, even as the soul. Indeed, the human body, since it is matter, would rather seem to be nearer the hypostasis than the soul, which is a form, since the principle of individuation, which is implied in the word "hypostasis," would seem to be matter. Hence the Son of God did not assume flesh through the medium of the soul.
Objection 3: Further, take away the medium and you separate what were joined by the medium; for example, if the superficies be removed color would leave the body, since it adheres to the body through the medium of the superficies. But though the soul was separated from the body by death, yet there still remained the union of the Word to the flesh, as will be shown (Q[50], AA[2],3). Hence the Word was not joined to flesh through the medium of the soul.
On the contrary, Augustine says (Ep. ad Volusianum cxxxvi): "The greatness of the Divine power fitted to itself a rational soul, and through it a human body, so as to raise the whole man to something higher."
I answer that, A medium is in reference to a beginning and an end. Hence as beginning and end imply order, so also does a medium. Now there is a twofold order: one, of time; the other, of nature. But in the mystery of the Incarnation nothing is said to be a medium in the order of time, for the Word of God united the whole human nature to Himself at the same time, as will appear (Q[30], A[3]). An order of nature between things may be taken in two ways: first, as regards rank of dignity, as we say the angels are midway between man and God; secondly, as regards the idea of causality, as we say a cause is midway between the first cause and the last effect. And this second order follows the first to some extent; for as Dionysius says (Coel. Hier. xiii), God acts upon the more remote substances through the less remote. Hence if we consider the rank of dignity, the soul is found to be midway between God and flesh; and in this way it may be said that the Son of God united flesh to Himself, through the medium of the soul. But even as regards the second order of causality the soul is to some extent the cause of flesh being united to the Son of God. For the flesh would not have been assumable, except by its relation to the rational soul, through which it becomes human flesh. For it was said above (Q[4], A[1]) that human nature was assumable before all others.
Reply to Objection 1: We may consider a twofold order between creatures and God: the first is by reason of creatures being caused by God and depending on Him as on the principle of their being; and thus on account of the infinitude of His power God touches each thing immediately, by causing and preserving it, and so it is that God is in all things by essence, presence and power. But the second order is by reason of things being directed to God as to their end; and it is here that there is a medium between the creature and God, since lower creatures are directed to God by higher, as Dionysius says (Eccl. Hier. v); and to this order pertains the assumption of human nature by the Word of God, Who is the term of the assumption; and hence it is united to flesh through the soul.
Reply to Objection 2: If the hypostasis of the Word of God were constituted simply by human nature, it would follow that the body was nearest to it, since it is matter which is the principle of individuation; even as the soul, being the specific form, would be nearer the human nature. But because the hypostasis of the Word is prior to and more exalted than the human nature, the more exalted any part of the human nature is, the nearer it is to the hypostasis of the Word. And hence the soul is nearer the Word of God than the body is.
Reply to Objection 3: Nothing prevents one thing being the cause of the aptitude and congruity of another, and yet if it be taken away the other remains; because although a thing's becoming may depend on another, yet when it is in being it no longer depends on it, just as a friendship brought about by some other may endure when the latter has gone; or as a woman is taken in marriage on account of her beauty, which makes a woman's fittingness for the marriage tie, yet when her beauty passes away, the marriage tie still remains. So likewise, when the soul was separated, the union of the Word with flesh still endured.
Objection 1: It would seem that the Son of God did not assume a soul through the medium of the spirit or mind. For nothing is a medium between itself and another. But the spirit is nothing else in essence but the soul itself, as was said above (FP, Q[77], A[1], ad 1). Therefore the Son of God did not assume a soul through the medium of the spirit or mind.
Objection 2: Further, what is the medium of the assumption is itself more assumable. But the spirit or mind is not more assumable than the soul; which is plain from the fact that angelic spirits are not assumable, as was said above (Q[4], A[1]). Hence it seems that the Son of God did not assume a soul through the medium of the spirit.
Objection 3: Further, that which comes later is assumed by the first through the medium of what comes before. But the soul implies the very essence, which naturally comes before its power---the mind. Therefore it would seem that the Son of God did not assume a soul through the medium of the spirit or mind.
On the contrary, Augustine says (De Agone Christ. xviii): "The invisible and unchangeable Truth took a soul by means of the spirit, and a body by means of the soul."
I answer that, As stated above (A[1]), the Son of God is said to have assumed flesh through the medium of the soul, on account of the order of dignity, and the congruity of the assumption. Now both these may be applied to the intellect, which is called the spirit, if we compare it with the other parts of the soul. For the soul is assumed congruously only inasmuch as it has a capacity for God, being in His likeness: which is in respect of the mind that is called the spirit, according to Eph. 4:23: "Be renewed in the spirit of your mind." So, too, the intellect is the highest and noblest of the parts of the soul, and the most like to God, and hence Damascene says (De Fide Orth. iii, 6) that "the Word of God is united to flesh through the medium of the intellect; for the intellect is the purest part of the soul, God Himself being an intellect."
Reply to Objection 1: Although the intellect is not distinct from the soul in essence, it is distinct from the other parts of the soul as a power; and it is in this way that it has the nature of a medium.
Reply to Objection 2: Fitness for assumption is wanting to the angelic spirits, not from any lack of dignity, but because of the irremediableness of their fall, which cannot be said of the human spirit, as is clear from what has been said above (FP, Q[62], A[8]; FP, Q[64], A[2]).
Reply to Objection 3: The soul, between which and the Word of God the intellect is said to be a medium, does not stand for the essence of the soul, which is common to all the powers, but for the lower powers, which are common to every soul.
Objection 1: It would seem that the soul of Christ was assumed before the flesh by the Word. For the Son of God assumed flesh through the medium of the soul, as was said above (A[1]). Now the medium is reached before the end. Therefore the Son of God assumed the soul before the body.
Objection 2: Further, the soul of Christ is nobler than the angels, according to Ps. 96:8: "Adore Him, all you His angels." But the angels were created in the beginning, as was said above (FP, Q[46], A[3]). Therefore the soul of Christ also (was created in the beginning). But it was not created before it was assumed, for Damascene says (De Fide Orth. iii, 2,3,9), that "neither the soul nor the body of Christ ever had any hypostasis save the hypostasis of the Word." Therefore it would seem that the soul was assumed before the flesh, which was conceived in the womb of the Virgin.
Objection 3: Further, it is written (Jn. 1:14): "We saw Him [Vulg.: 'His glory'] full of grace and truth," and it is added afterwards that "of His fulness we have all received" (Jn. 1:16), i.e. all the faithful of all time, as Chrysostom expounds it (Hom. xiii in Joan.). Now this could not have been unless the soul of Christ had all fulness of grace and truth before all the saints, who were from the beginning of the world, for the cause is not subsequent to the effect. Hence since the fulness of grace and truth was in the soul of Christ from union with the Word, according to what is written in the same place: "We saw His glory, the glory as it were of the Only-begotten of the Father, full of grace and truth," it would seem in consequence that from the beginning of the world the soul of Christ was assumed by the Word of God.
On the contrary, Damascene says (De Fide Orth. iv, 6): "The intellect was not, as some untruthfully say, united to the true God, and henceforth called Christ, before the Incarnation which was of the Virgin."
I answer that, Origen (Peri Archon i, 7,8; ii, 8) maintained that all souls, amongst which he placed Christ's soul, were created in the beginning. But this is not fitting, if we suppose that it was first of all created, but not at once joined to the Word, since it would follow that this soul once had its proper subsistence without the Word; and thus, since it was assumed by the Word, either the union did not take place in the subsistence, or the pre-existing subsistence of the soul was corrupted. So likewise it is not fitting to suppose that this soul was united to the Word from the beginning, and that it afterwards became incarnate in the womb of the Virgin; for thus His soul would not seem to be of the same nature as ours, which are created at the same time that they are infused into bodies. Hence Pope Leo says (Ep. ad Julian. xxxv) that "Christ's flesh was not of a different nature to ours, nor was a different soul infused into it in the beginning than into other men."
Reply to Objection 1: As was said above (A[1]), the soul of Christ is said to be the medium in the union of the flesh with the Word, in the order of nature; but it does not follow from this that it was the medium in the order of time.
Reply to Objection 2: As Pope Leo says in the same Epistle, Christ's soul excels our soul "not by diversity of genus, but by sublimity of power"; for it is of the same genus as our souls, yet excels even the angels in "fulness of grace and truth." But the mode of creation is in harmony with the generic property of the soul; and since it is the form of the body, it is consequently created at the same time that it is infused into and united with the body; which does not happen to angels, since they are substances entirely free from matter.
Reply to Objection 3: Of the fulness of Christ all men receive according to the faith they have in Him; for it is written (Rom. 3:22) that "the justice of God is by faith of Jesus Christ unto all and upon all them that believe in Him." Now just as we believe in Him as already born; so the ancients believed in Him as about to be born, since "having the same spirit of faith . . . we also believe," as it is written (2 Cor. 4:13). But the faith which is in Christ has the power of justifying by reason of the purpose of the grace of God, according to Rom. 4:5: "But to him that worketh not, yet believeth in Him that justifieth the ungodly, his faith is reputed to justice according to the purpose of the grace of God." Hence because this purpose is eternal, there is nothing to hinder some from being justified by the faith of Jesus Christ, even before His soul was full of grace and truth.
Objection 1: It would seem that the flesh of Christ was assumed by the Word before being united to the soul. For Augustine [*Fulgentius] says (De Fide ad Petrum xviii): "Most firmly hold, and nowise doubt that the flesh of Christ was not conceived in the womb of the Virgin without the Godhead before it was assumed by the Word." But the flesh of Christ would seem to have been conceived before being united to the rational soul, because matter or disposition is prior to the completive form in order of generation. Therefore the flesh of Christ was assumed before being united to the soul.
Objection 2: Further, as the soul is a part of human nature, so is the body. But the human soul in Christ had no other principle of being than in other men, as is clear from the authority of Pope Leo, quoted above (A[3] ). Therefore it would seem that the body of Christ had no other principle of being than we have. But in us the body is begotten before the rational soul comes to it. Therefore it was the same in Christ; and thus the flesh was assumed by the Word before being united to the soul.
Objection 3: Further, as is said (De Causis), the first cause excels the second in bringing about the effect, and precedes it in its union with the effect. But the soul of Christ is compared to the Word as a second cause to a first. Hence the Word was united to the flesh before it was to the soul.
On the contrary, Damascene says (De Fide Orth. iii, 2): "At the same time the Word of God was made flesh, and flesh was united to a rational and intellectual soul." Therefore the union of the Word with the flesh did not precede the union with the soul.
I answer that, The human flesh is assumable by the Word on account of the order which it has to the rational soul as to its proper form. Now it has not this order before the rational soul comes to it, because when any matter becomes proper to any form, at the same time it receives that form; hence the alteration is terminated at the same instant in which the substantial form is introduced. And hence it is that the flesh ought not to have been assumed before it was human flesh; and this happened when the rational soul came to it. Therefore since the soul was not assumed before the flesh, inasmuch as it is against the nature of the soul to be before it is united to the body, so likewise the flesh ought not to have been assumed before the soul, since it is not human flesh before it has a rational soul.
Reply to Objection 1: Human flesh depends upon the soul for its being; and hence, before the coming of the soul, there is no human flesh, but there may be a disposition towards human flesh. Yet in the conception of Christ, the Holy Ghost, Who is an agent of infinite might, disposed the matter and brought it to its perfection at the same time.
Reply to Objection 2: The form actually gives the species; but the matter in itself is in potentiality to the species. And hence it would be against the nature of a form to exist before the specific nature. And therefore the dissimilarity between our origin and Christ's origin, inasmuch as we are conceived before being animated, and Christ's flesh is not, is by reason of what precedes the perfection of the nature, viz. that we are conceived from the seed of man, and Christ is not. But a difference which would be with reference to the origin of the soul, would bespeak a diversity of nature.
Reply to Objection 3: The Word of God is understood to be united to the flesh before the soul by the common mode whereby He is in the rest of creatures by essence, power, and presence. Yet I say "before," not in time, but in nature; for the flesh is understood as a being, which it has from the Word, before it is understood as animated, which it has from the soul. But by the personal union we understand the flesh as united to the soul before it is united to the Word, for it is from its union with the soul that it is capable of being united to the Word in Person; especially since a person is found only in the rational nature
Objection 1: It would seem that the Son of God assumed the whole human nature through the medium of its parts. For Augustine says (De Agone Christ. xviii) that "the invisible and unchangeable Truth assumed the soul through the medium of the spirit, and the body through the medium of the soul, and in this way the whole man." But the spirit, soul, and body are parts of the whole man. Therefore He assumed all, through the medium of the parts.
Objection 2: Further, the Son of God assumed flesh through the medium of the soul because the soul is more like to God than the body. But the parts of human nature, since they are simpler than the body, would seem to be more like to God, Who is most simple, than the whole. Therefore He assumed the whole through the medium of the parts.
Objection 3: Further, the whole results from the union of parts. But the union is taken to be the term of the assumption, and the parts are presupposed to the assumption. Therefore He assumed the whole by the parts.
On the contrary, Damascene says (De Fide Orth. iii, 16): "In our Lord Jesus Christ we do not behold parts of parts, but such as are immediately joined, i.e. the Godhead and the manhood." Now the humanity is a whole, which is composed of soul and body, as parts. Therefore the Son of God assumed the parts through the medium of the whole.
I answer that, When anything is said to be a medium in the assumption of the Incarnation, we do not signify order of time, because the assumption of the whole and the parts was simultaneous. For it has been shown (AA[3] ,4) that the soul and body were mutually united at the same time in order to constitute the human nature of the Word. But it is order of nature that is signified. Hence by what is prior in nature, that is assumed which is posterior in nature. Now a thing is prior in nature in two ways: First on the part of the agent, secondly on the part of the matter; for these two causes precede the thing. On the part of the agent---that is simply first, which is first included in his intention; but that is relatively first, with which his operation begins---and this because the intention is prior to the operation. On the part of the matter---that is first which exists first in the transmutation of the matter. Now in the Incarnation the order depending on the agent must be particularly considered, because, as Augustine says (Ep. ad Volusianum cxxxvii), "in such things the whole reason of the deed is the power of the doer." But it is manifest that, according to the intention of the doer, what is complete is prior to what is incomplete, and, consequently, the whole to the parts. Hence it must be said that the Word of God assumed the parts of human nature, through the medium of the whole; for even as He assumed the body on account of its relation to the rational soul, so likewise He assumed a body and soul on account of their relation to human nature.
Reply to Objection 1: From these words nothing may be gathered, except that the Word, by assuming the parts of human nature, assumed the whole human nature. And thus the assumption of parts is prior in the order of the intellect, if we consider the operation, but not in order of time; whereas the assumption of the nature is prior if we consider the intention: and this is to be simply first, as was said above.
Reply to Objection 2: God is so simple that He is also most perfect; and hence the whole is more like to God than the parts, inasmuch as it is more perfect.
Reply to Objection 3: It is a personal union wherein the assumption is terminated, not a union of nature, which springs from a conjunction of parts.
Objection 1: It would seem that the Son of God assumed human nature through the medium of grace. For by grace we are united to God. But the human nature in Christ was most closely united to God. Therefore the union took place by grace.
Objection 2: Further, as the body lives by the soul, which is its perfection, so does the soul by grace. But the human nature was fitted for the assumption by the soul. Therefore the Son of God assumed the soul through the medium of grace.
Objection 3: Further, Augustine says (De Trin. xv, 11) that the incarnate Word is like our spoken word. But our word is united to our speech by means of "breathing" [spiritus]. Therefore the Word of God is united to flesh by means of the Holy Spirit, and hence by means of grace, which is attributed to the Holy Spirit, according to 1 Cor. 12:4: "Now there are diversities of graces, but the same Spirit."
On the contrary, Grace is an accident in the soul, as was shown above (FS, Q[110], A[2]). Now the union of the Word with human nature took place in the subsistence, and not accidentally, as was shown above (Q[2], A[6]). Therefore the human nature was not assumed by means of grace.
I answer that, In Christ there was the grace of union and habitual grace. Therefore grace cannot be taken to be the medium of the assumption of the human nature, whether we speak of the grace of union or of habitual grace. For the grace of union is the personal being that is given gratis from above to the human nature in the Person of the Word, and is the term of the assumption. Whereas the habitual grace pertaining to the spiritual holiness of the man is an effect following the union, according to Jn. 1:14: "We saw His glory . . . as it were of the Only-begotten of the Father, full of grace and truth"---by which we are given to understand that because this Man (as a result of the union) is the Only-begotten of the Father, He is full of grace and truth. But if by grace we understand the will of God doing or bestowing something gratis, the union took place by grace, not as a means, but as the efficient cause.
Reply to Objection 1: Our union with God is by operation, inasmuch as we know and love Him; and hence this union is by habitual grace, inasmuch as a perfect operation proceeds from a habit. Now the union of the human nature with the Word of God is in personal being, which depends not on any habit, but on the nature itself.
Reply to Objection 2: The soul is the substantial perfection of the body; grace is but an accidental perfection of the soul. Hence grace cannot ordain the soul to personal union, which is not accidental, as the soul ordains the body.
Reply to Objection 3: Our word is united to our speech, by means of breathing [spiritus], not as a formal medium, but as a moving medium. For from the word conceived within, the breathing proceeds, from which the speech is formed. And similarly from the eternal Word proceeds the Holy Spirit, Who formed the body of Christ, as will be shown (Q[32], A[1]). But it does not follow from this that the grace of the Holy Spirit is the formal medium in the aforesaid union.