Reply to Objection 1: The beginning of the infusion of the soul may be considered in two ways. First, in regard to the disposition of the body. And thus, the beginning of the infusion of the soul into Christ's body was the same as in other men's bodies: for just as the soul is infused into another man's body as soon as it is formed, so was it with Christ. Secondly, this beginning may be considered merely in regard to time. And thus, because Christ's body was perfectly formed in a shorter space of time, so after a shorter space of time was it animated.
Reply to Objection 2: The soul requires due quantity in the matter into which it is infused: but this quantity allows of a certain latitude because it is not fixed to a certain amount. Now the quantity that a body has when the soul is first infused into it is in proportion to the perfect quantity to which it will attain by development: that is to say, men of greater stature have greater bodies at the time of first animation. But Christ at the perfect age was of becoming and middle stature: in proportion to which was the quantity of His body at the time when other men's bodies are animated; though it was less than theirs at the first instant of His conception. Nevertheless that quantity was not too small to safeguard the nature of an animated body; since it would have sufficed for the animation of a small man's body.
Reply to Objection 3: What the Philosopher says is true in the generation of other men, because the body is successively formed and disposed for the soul: whence, first, as being imperfectly disposed, it receives an imperfect soul; and afterwards, when it is perfectly disposed, it receives a perfect soul. But Christ's body, on account of the infinite power of the agent, was perfectly disposed instantaneously. Wherefore, at once and in the first instant it received a perfect form, that is, the rational soul.
Whether Christ's flesh was first of all conceived and afterwards assumed?
Objection 1: It would seem that Christ's flesh was first of all conceived, and afterwards assumed. Because what is not cannot be assumed. But Christ's flesh began to exist when it was conceived. Therefore it seems that it was assumed by the Word of God after it was conceived.
Objection 2: Further, Christ's flesh was assumed by the Word of God, by means of the rational soul. But it received the rational soul at the term of the conception. Therefore it was assumed at the term of the conception. But at the term of the conception it was already conceived. Therefore it was first of all conceived and afterwards assumed.
Objection 3: Further, in everything generated, that which is imperfect precedes in time that which is perfect: which is made clear by the Philosopher (Metaph. ix). But Christ's body is something generated. Therefore it did not attain to its ultimate perfection, which consisted in the union with the Word of God, at the first instant of its conception; but, first of all, the flesh was conceived and afterwards assumed.
On the contrary, Augustine says (De Fide ad Petrum xviii [*Written by Fulgentius]): "Hold steadfastly, and doubt not for a moment that Christ's flesh was not conceived in the Virgin's womb, before being assumed by the Word."
I answer that, As stated above, we may say properly that "God was made man," but not that "man was made God": because God took to Himself that which belongs to man---and that which belongs to man did not pre-exist, as subsisting in itself, before being assumed by the Word. But if Christ's flesh had been conceived before being assumed by the Word, it would have had at some time an hypostasis other than that of the Word of God. And this is against the very nature of the Incarnation, which we hold to consist in this, that the Word of God was united to human nature and to all its parts in the unity of hypostasis: nor was it becoming that the Word of God should, by assuming human nature, destroy a pre-existing hypostasis of human nature or of any part thereof. It is consequently contrary to faith to assert that Christ's flesh was first of all conceived and afterwards assumed by the Word of God.
Reply to Objection 1: If Christ's flesh had been formed or conceived, not instantaneously, but successively, one of two things would follow: either that what was assumed was not yet flesh, or that the flesh was conceived before it was assumed. But since we hold that the conception was effected instantaneously, it follows that in that flesh the beginning and the completion of its conception were in the same instant. So that, as Augustine [*Fulgentius, De Fide ad Petrum xviii] says: "We say that the very Word of God was conceived in taking flesh, and that His very flesh was conceived by the Word taking flesh."
From the above the reply to the Second Objection is clear. For in the same moment that this flesh began to be conceived, its conception and animation were completed.
Reply to Objection 3: The mystery of the Incarnation is not to be looked upon as an ascent, as it were, of a man already existing and mounting up to the dignity of the Union: as the heretic Photinus maintained. Rather is it to be considered as a descent, by reason of the perfect Word of God taking unto Himself the imperfection of our nature; according to Jn. 6:38 : "I came down from heaven."
Whether Christ's conception was natural?
Objection 1: It would seem that Christ's conception was natural. For Christ is called the Son of Man by reason of His conception in the flesh. But He is a true and natural Son of Man: as also is He the true and natural Son of God. Therefore His conception was natural.
Objection 2: Further, no creature can be the cause of a miraculous effect. But Christ's conception is attributed to the Blessed Virgin, who is a mere creature: for we say that the Virgin conceived Christ. Therefore it seems that His conception was not miraculous, but natural.
Objection 3: Further, for a transformation to be natural, it is enough that the passive principle be natural, as stated above (Q[32], A[4]). But in Christ's conception the passive principle on the part of His Mother was natural, as we have shown (Q[32], A[4]). Therefore Christ's conception was natural.
On the contrary, Dionysius says (Ep. ad Caium Monach.): "Christ does in a superhuman way those things that pertain to man: this is shown in the miraculous virginal conception."
I answer that, As Ambrose says (De Incarn. vi): "In this mystery thou shalt find many things that are natural, and many that are supernatural." For if we consider in this conception anything connected with the matter thereof, which was supplied by the mother, it was in all such things natural. But if we consider it on the part of the active power, thus it was entirely miraculous. And since judgment of a thing should be pronounced in respect of its form rather than of its matter: and likewise in respect of its activity rather than of its passiveness: therefore is it that Christ's conception should be described simply as miraculous and supernatural, although in a certain respect it was natural.
Reply to Objection 1: Christ is said to be a natural Son of Man, by reason of His having a true human nature, through which He is a Son of Man, although He had it miraculously; thus, too, the blind man to whom sight has been restored sees naturally by sight miraculously received.
Reply to Objection 2: The conception is attributed to the Blessed Virgin, not as the active principle thereof, but because she supplied the matter, and because the conception took place in her womb.
Reply to Objection 3: A natural passive principle suffices for a transformation to be natural, when it is moved by its proper active principle in a natural and wonted way. But this is not so in the case in point. Therefore this conception cannot be called simply natural.