Nicene and Post-Nicene Fathers, Vol. IV:
Writings in Connection with the Manichæan Controversy.: Chapter 14

Chapter 14.—Manichæus Promises the Knowledge of Undoubted Things, and Then Demands Faith in Doubtful Things.

In the next place, if faith is what is required of me, I should prefer to keep to the Scripture, which tells me that the Holy Spirit came and inspired the apostles, to whom the Lord had promised to send Him.  You must therefore prove, either that what Manichæus says is true, and so make clear to me what I am unable to believe; or that Manichæus is the Holy Spirit, and so lead me to believe in what you cannot make clear.  For I profess the Catholic faith, and by it I expect to attain certain knowledge.  Since, then, you try to overthrow my faith, you must supply me with certain knowledge, if you can, that you may convict me of having adopted my present belief without consideration.  You make two distinct propositions,—one when you say that the speaker is the Holy Spirit, and another when you say that what the speaker teaches is p. 136 evidently true.  I might fairly ask undeniable proof for both propositions.  But I am not greedy and require to be convinced only of one.  Prove this person to be the Holy Spirit, and I will believe what he says to be true, even without understanding it; or prove that what he says is true, and I will believe him to be the Holy Spirit, even without evidence.  Could anything be fairer or kinder than this?  But you cannot prove either one or other of these propositions.  You can find nothing better than to praise your own faith and ridicule mine.  So, after having in my turn praised my belief and ridiculed yours, what result do you think we shall arrive at as regards our judgment and our conduct, but to part company with those who promise the knowledge of indubitable things, and then demand from us faith in doubtful things? while we shall follow those who invite us to begin with believing what we cannot yet fully perceive, that, strengthened by this very faith, we may come into a position to know what we believe by the inward illumination and confirmation of our minds, due no longer to men, but to God Himself.

18.  And as I have asked this writer to prove these things to me, I ask him now where he learned them himself.  If he replies that they were revealed to him by the Holy Spirit, and that his mind was divinely enlightened that he might know them to be certain and evident, he himself points to the distinction between knowing and believing.  The knowledge is his to whom these things are fully made known as proved; but in the case of those who only hear his account of these things, there is no knowledge imparted, but only a believing acquiescence required.  Whoever thoughtlessly yields this becomes a Manichæan, not by knowing undoubted truth, but by believing doubtful statements.  Such were we when in our inexperienced youth we were deceived.  Instead, therefore, of promising knowledge, or clear evidence, or the settlement of the question free from all uncertainty, Manichæus ought to have said that these things were clearly proved to him, but that those who hear his account of them must believe him without evidence.  But were he to say this, who would not reply to him, If I must believe without knowing, why should I not prefer to believe those things which have a widespread notoriety from the consent of learned and unlearned, and which among all nations are established by the weightiest authority?  From fear of having this said to him, Manichæus bewilders the inexperienced by first promising the knowledge of certain truths, and then demanding faith in doubtful things.  And then, if he is asked to make it plain that these things have been proved to himself, he fails again, and bids us believe this too.  Who can tolerate such imposture and arrogance?