4 One is shocked at your wild fancies about this First Man changing the elements which he brought, that he might conquer his enemies by pleasing them. So you make what you call the kingdom of falsehood keep honestly to its own nature, while truth is changeable in order to deceive. Jesus Christ, according to you, is the son of this First Man. Truth springs, forsooth, from your fiction. You praise this First Man for using changeable and delusive forms in the contest. If you, then, speak the truth, you do not imitate him.
If you imitate him, you deceive as he did. But our Lord and Saviour Jesus Christ, the true and truthful Son of God, the true and truthful Son of man, both of which He testifies of Himself, derived the eternity of His godhead from true God, and His incarnation from true man. Your First Man is not the first man of the apostle. "The first man," he says, "was of the earth, earthy; the second man is from heaven, heavenly. As is the earthy, such are they also that are earthy; as is the heavenly, such are they also that are heavenly.
As we have borne the image of the earthy, let us also bear the image of the heavenly." The first man of the earth, earthy, is Adam, who was made of dust. The second man from heaven, heavenly, is the Lord Jesus Christ; for, being the Son of God, He became flesh that He might be a man outwardly, while He remained God within; that He might be both the true Son of God, by whom we were made, and the true Son of man, by whom we are made anew. Why do you conjure up this fabulous First Man of yours, and refuse to acknowledge the first man of the apostle?
Is this not a fulfillment of what the apostle says: "Turning away their ears from the truth, they will give heed to fables?" According to Paul, the first man is of the earth, earthy; according to Manichæus, he is not earthy, and is equipped with five elements of some unreal, unintelligible kind. Paul says: "If any one should have announced to you differently from what we have announced let him be accursed." Therefore lest Paul be a liar, let Manichæus be accursed.
Source: Reply to Faustus the Manichaean (New Advent)