Thomas Aquinas, Compendium of Theology

Photinus emptied the mystery of the Incarnation of all meaning by denying Christ's divine nature. The Manichaean did the same by denying Christ's human nature. He held that the whole of material creation was the work of the devil and that the Son of the good God could not becomingly take to Himself a creature of the devil. Therefore he taught that Christ did not have real flesh but only phantom flesh. Consequently he asserted that everything narrated in the Gospel as pertaining to the human nature of Christ, was done in appearance only and not in very truth.

This theory plainly gives the lie to Sacred Scripture, which relates that Christ was born of the Virgin, that He was circumcised, that He was hungry, that He ate, and that He had other experiences common to the nature of human flesh. Hence in recording such things of Christ, what is written in the Gospels would be false.

Besides, Christ says of Himself: "For this was I born, and for this came I into the world, that I should give testimony to the truth" (John 18:37). If He had displayed in Himself what really did not exist, He would have been a witness not of truth but rather of error; especially since He foretold that He would suffer that which He could not suffer without a body, namely, that He would be betrayed into the hands of men, that He would be spat upon, scourged, and crucified. Accordingly, to say that Christ did not have true flesh and that He suffered such indignities not in truth but only in appearance, is to accuse Him of lying.

Furthermore, to banish true conviction from men's minds is the act of a liar. Christ did expel a certain notion from the minds of His disciples. After His resurrection He appeared to the disciples, who thought that He was a spirit or a specter. To banish suspicion of this kind from their hearts, He said to them: "Handle and see: for a spirit hath not flesh and bones, as you see Me to have" (Luke 24:39). On another occasion, when He was walking on the sea, to the consternation of His disciples who thought He was an apparition, our Lord said: "It is I, fear ye not" (Matt. 14:27). If the opinion entertained by the disciples about a spectral body is true, we have to concede that Christ was deceitful. But Christ is the Truth, as He testified of Himself. Therefore the Manichaean theory is false.