5 Faustus tells us that he has good grounds for concluding that these Scriptures are unworthy of credit. And yet he speaks of not using arguments. But the argument too shall be refuted. The end of the whole argument is to bring the soul to believe that the reason of its misery in this world is, that it is the means of preventing God from being deprived of His kingdom, and that God's substance and nature is so exposed to change, corruption, injury, and contamination, that part of it is incurably defiled, and is consigned by Himself to eternal punishment in the mass of darkness, though, when it was in harmless union with Himself, and guilty of no crime, He knowingly sent it where it was to suffer defilement.
This is the end of all your arguments and fictions; and would that there were an end of them as regards your heart and your lips, that you might sometime desist from believing and uttering those execrable blasphemies! But, says Faustus, I prove from the writings themselves that they cannot be in all points trustworthy, for they contradict one another. Why not say, then, that they are wholly untrustworthy, if their testimony is inconsistent and self-contradictory? But, says Faustus, I say what I think to be in accordance with truth.
With what truth? The truth is only your own fiction, which begins with God's battle, goes on to His contamination, and ends with His damnation. No one, says Faustus, believes writings which contradict themselves. But if you think they do this, it is because you do not understand them; for your ignorance has been manifested in regard to the passages you have quoted in support of your opinion, and the same will appear in regard to any quotations you may still make. So there is no reason for our not believing these writings, supported as they are by such weighty testimony; and this is itself the best reason for pronouncing accursed those whose preaching differs from what is there written.
Source: Reply to Faustus the Manichaean (New Advent)