31 What, that all heretics exhort us to believe in Christ? Can they possibly be more opposed to themselves? And in this matter they are to be pressed in a twofold way. In the first place we must ask of them, where is the reason which they used to promise, where the reproof of rashness, where the assumption of knowledge? For, if it be disgraceful to believe any without reason, what do you wait for, what are you busied about, that I believe some one without reason, in order that I may the more easily be led by your reason?
What, will your reason raise any firm superstructure on the foundation of rashness? I speak after their manner, whom we displease by believing. For I not only judge it most healthful to believe before reason, when you are not qualified to receive reason, and by the very act of faith thoroughly to cultivate the mind to receive the seeds of truth, but altogether a thing of such sort as that without it health cannot return to sick souls. And in that this seems to them matter for mockery and full of rashness, surely they are shameless in making it their business that we believe in Christ.
Next, I confess that I have already believed in Christ, and have convinced myself that what He has said is true, although it be supported by no reason; is this, heretic, what you will teach me in the first place? Allow me to consider a little with myself, (since I have not seen Christ Himself, as He willed to appear unto men, Who is said to have been seen by them, even by common eyes,) who they are that I have believed concerning Him, in order that I may approach you already furnished beforehand with such a faith.
I see that there are none that I have believed, save the confirmed opinion and widely extended report of peoples and nations: and that the mysteries of the Church Catholic have in all times and places had possession of these peoples. Why therefore shall I not of these, in preference to others, inquire with all care, what Christ commanded, by whose authority I have been moved already to believe that Christ has commanded something that is profitable? Are you likely to be a better expounder to me of what He said, Whose past or present existence I should not believe, if by you I were to be recommended to believe thus?
This therefore I have believed, as I said, trusting to report strengthened by numbers, agreement, antiquity. But you, who are both so few, and so turbulent, and so new, no one doubts that you bring forward nothing worthy of authority. What then is that so great madness? Believe them, that you are to believe in Christ, and learn from us what He said. Why, I pray you? For were they to fail and to be unable to teach me any thing with much greater ease could I persuade my self, that I am not to believe in Christ, than that I am to learn any thing concerning Him, save from those through whom I had believed in Him.
O vast confidence, or rather absurdity! I teach you what Christ, in Whom you believe, commanded. What, in case I believed not in Him? You could not, could you, teach me any thing concerning Him? But, says he, it behooves you to believe. You do not mean, do you, that I am (to believe) you when you commend Him to my faith? No, says he, for we lead by reason them who believe in Him. Why then should I believe in Him? Because report has been grounded. Whether is it through you, or through others?
Through others, says he. Shall I then believe them, in order that you may teach me? Perhaps I ought to do so, were it not that they gave me this chief charge, that I should not approach you at all; for they say that you have deadly doctrines. You will answer, They lie. How then shall I believe them concerning Christ, Whom they have not seen, (and) not believe them concerning you, whom they are unwilling to see? Believe the Scriptures, says he. But every writing, if it be brought forward new and unheard of, or be commended by few, with no reason to confirm it, it is not it that is believed, but they who bring it forward.
Wherefore, for those Scriptures, if you are they who bring them forward, you so few and unknown, I am not pleased to believe them. At the same time also you are acting contrary to your promise, in enforcing faith rather than giving a reason. You will recall me again to numbers and (common) report. Curb, I pray you, your obstinacy, and that untamed lust, I know not what, of spreading your name: and advise me rather to seek the chief men of this multitude, and to seek with all care and pains rather to learn something concerning these writings from these men, but for whose existence, I should not know that I had to learn at all. But do you return into your dens, and lay not any snares under the name of truth, which you endeavor to take from those, to whom you yourself grant authority.
Source: On the Profit of Believing (New Advent)