Although, of course, every divine operation by which something is accomplished in creatures is common to the entire Trinity (as has been shown in the points made above), the formation of Christ’s body, which was perfected by the divine power, is suitably ascribed to the Holy Spirit although it is common to the entire Trinity.
 Now, this seems to be in harmony with the Incarnation of the Word. For, just as our word mentally conceived is invisible, but is made sensible in an external vocal expression, so the Word of God in the eternal generation exists invisibly in the heart of the Father, but by the Incarnation is made sensible to us. Thus, the Incarnation of God’s Word is like the vocal expression of our word. But the vocal expression of our word is made by our spirit, through which the vocal formation of our word takes place. Suitably, then, it is through the Spirit of the Son Of God that the formation of His flesh is said to have taken place.
 This is also in harmony with human generation. The active power which is in the human seed, drawing to itself the matter which flows from the mother, operates by the spirit, for this kind of power is founded on the spirit, and by reason of its control the seed must be cloudy and white. Therefore, the Word of God taking flesh to Himself from the Virgin is suitably said to do this by His Spirit—to form flesh by assuming it.
 Ths also helps to suggest a cause moving to the Incarnation of the Word. And this could, indeed, be no other than the unmeasured love of God for man whose nature He wished to couple with Himself in unity of person. But in the divinity it is the Holy Spirit who proceeds as love, as was said. Suitably, then, was the task of Incarnation attributed to the Holy Spirit.
 Sacred Scripture, too, is accustomed to attributing every grace to the Holy Spirit, for what is graciously given seems bestowed by the love of the giver. But no greater gift has been bestowed on man than union with God in person. Therefore, suitably is this work marked as the Holy Spirit’s own.
Next - CONTRA GENTILES: BOOK FOUR: SALVATION - Chapter 47 THAT CHRIST WAS NOT THE SON OF THE HOLY SPIRIT IN THE FLESH