Now, although Christ is said to be conceived of the Holy Spirit and of the Virgin, one cannot for all that say that the Holy Spirit is the father of Christ in the human generation as the Virgin is His mother.
 For the Holy Spirit did not produce the human nature of Christ out of His substance, but by His power alone operated for its production. It cannot, therefore, be said that the Holy Spirit is the father of Christ in His human generation.
 It would, furthermore, be productive of error to say that Christ is the son of the Holy Spirit. Plainly, God’s Word has a distinct Person in that He is the Son of God the Father. If, then, He were in His human nature called the son of the Holy Spirit, one would have to understand Christ as being two sons, since the Word of God cannot be the son of the Holy Spirit. And thus, since the name of sonship belongs to a person and not to a nature, it would follow that in Christ there are two Persons. But this is foreign to the Catholic faith.
 It would be unsuitable, also, to transfer the name and the authority of the Father to another. Yet this happens if the Holy Spirit is called the father of Christ.
Next - CONTRA GENTILES: BOOK FOUR: SALVATION - Chapter 48 THAT CHRIST MUST NOT BE CALLED A CREATURE