Thomas Aquinas, Compendium of Theology

This mystery of the divine Incarnation, Photinus set aside, so far as he could. Following Ebion, Cerinthus, and Paul of Samosata, he asserted that our Lord Jesus Christ was no more than a man and that He did not exist before the Virgin Mary, but earned the glory of divinity by the merit of a blessed life and by patiently enduring death; and thus He was called God, not on account of His nature, but by the grace of adoption. In this event no union of God with man would have been effected; only a man would be deified by grace. Elevation of this sort is not peculiar to Christ, but is common to all the saints, although some may be considered more highly endowed with such grace than others.

This error contradicts the authority of Sacred Scripture. In John 1:1 we read: "In the beginning was the Word." Shortly after the Evangelist adds: "And the Word was made flesh." Hence the Word that in the beginning was with God assumed flesh. But Scripture does not say that a man who lacked previous existence was deified by the grace of adoption. Likewise, in John 6:38 the Lord says: "I came down from heaven, not to do My own will, but the will of Him that sent Me." According to the error of Photinus, Christ could not come down from heaven, but could only go up to heaven. Against him is the Apostle, who says in Ephesians 4:9: "That He ascended, what is it but because He also descended first into the lower parts of the earth?" This enables us to understand clearly that the Ascension would have no place in Christ unless His descent from heaven had preceded.