Commentaria in Summam contra Gentiles, Liber IV

After St. Thomas has determined concerning those things that belong to the divine Trinity, he begins to determine concerning the Incarnation of the divine Word, and concerning those things that follow upon it¹. Around this, moreover, he does two things: first, he determines concerning the Incarnation of the Word; second, concerning the effects of the incarnate Christ in us, in ch. LVI. — Around the first he does two things: first, he shows that God is incarnate; second, he shows the fittingness of the Incarnation, in ch. L. — Around the first he does two things: first, he shows that God is incarnate; second, he raises certain doubts against the Incarnation itself, in ch. XL.

Around the first he does two things: first, he shows the proposition by the authority of Sacred Scripture; second, he excludes errors concerning this Incarnation, in the following chapter.

I. As to the first, he premises, in order to intimate the order of the doctrine, that because it was said above that certain things belong to the Son of God, the Lord Jesus Christ, according to the divine nature, and certain things according to the human nature, which He willed to be incarnate by assuming in time: it remains to speak of the mystery of the Incarnation itself.

He premises secondly that the Incarnation, among divine works, especially exceeds reason. And because this is the most wondrous among all things, it follows that all other wondrous works² are ordered to the belief of this most wondrous thing: since that which is greatest in each genus seems to be the cause of the others.

II. It must be noted first that the Incarnation is posited by St. Thomas as the miracle of all miracles, III Sent., d. III, q. II, a. 2; IV Sent., d. XI³; and de Pot., q. VI, a. 2, ad 9: on the ground that it is both of the first order of miracles, namely of those which God alone can do, and holds the supreme grade in that order, because this is most remote from the power of nature, in accordance with those things that were determined above in the Third Book, where miracles were treated⁴. And therefore it is said here that it especially exceeds reason, and that it is the most wondrous work. For the more something is above the power of nature and the further it departs from it, the more we wonder at it, and the less we are able to grasp it by our reason, because our reason receives knowledge from sensible and natural things.

It must be noted secondly, from the Qq. de Pot., where cited above, that other miraculous works induce belief in this very miracle of the Incarnation; for it is not unfitting for one miracle to induce belief in another. Therefore it is said here that all other wondrous works are ordered to the belief of this miracle.

III. Having presupposed these things, he proves his intent. First, from the authority of John 1, where it is said, And the Word was made flesh etc.

Secondly, from the authority of the Apostle, Phil. II, where he says, Who being in the form of God etc.

Thirdly, from the words of the Lord Jesus Christ Himself, who sometimes spoke lowly things of Himself, which belong to Him according to the assumed humanity, but sometimes sublime and divine things, which it is certain belong to Him according to the divine nature.

Fourthly, from the deeds of the Lord Himself: of which certain ones pertain to His humanity, as that He feared, etc.; but certain ones to His divinity, as that He healed the sick by His own power, etc.

It must be observed that St. Thomas posited that Christ's miracles show His divinity because He performed them by His own power. Because working miracles by a participated divine power can belong even to men; but working miracles by one's own power belongs to God alone. For it is of the nature of a miracle that God alone can do them, namely by His own power: either as to the substance of the deed, or as to the manner of doing it.