Chapter 26.—The Manicheans Do Not Receive All the Books of the Old Testament, and of the New Only Those that They Choose.
But wherefore is “the case of infants not allowed,” as you write, “to be alleged as an example for their elders,” by men who do not hesitate to affirm against the Pelagians that there is original sin, which entered by one man into the world, and that from one all have gone into condemnation? 3613 This, the Manicheans, too, do not receive, who not only reject all the Scriptures of the Old Testament as of authority, but even receive those which belong to the New Testament in such a manner as that each man, by his own prerogative as it were, or rather by his own sacrilege, takes what he likes, and rejects what he does not like,—in opposition to whom I treated in my writings on Free Will, whence they think that they have a ground of objection against me. I have been unwilling to deal plainly with the very laborious questions that occurred, lest my work should become too long, in a case which, as opposed to such perverse men, I could not have the assistance of the authority of the sacred Scriptures. And I was able,—as I actually did, whether anything of the divine testimonies might be true or not, seeing that I did not definitely introduce them into the argument,—nevertheless, by certain reasoning, to conclude that God in all things is to be praised, without any necessity of believing, as they would have us, that there are two co-eternal, confounded substances of good and evil.
See the Letter of Hilary in Augustins Letters, 226, ch. 8.