32 But if they say that we are not even to believe in Christ, unless undoubted reason shall be given us, they are not Christians. For this is what certain pagans say against us, foolishly indeed, yet not contrary to, or inconsistent with, themselves. But who can endure that these profess to belong to Christ, who contend that they are to believe nothing, unless they shall bring forward to fools most open reason concerning God? But we see that He Himself, so far as that history, which they themselves believe, teaches, willed nothing before, or more strongly than, that He should be believed in: whereas they, with whom He had to do, were not yet qualified to receive the secret things of God.
For, for what other purpose are so great and so many miracles, He Himself also saying, that they are done for no other cause, than that He may be believed in? He used to lead fools by faith, you lead by reason. He used to cry out, that He should be believed in, you cry out against it. He used to praise such as believe in Him, you blame them. But unless either He should change water into wine, to omit other (miracles), if men would follow Him, doing no such, but (only) teaching; either we must make no account of that saying, “Believe ye God, believe also Me;” or we must charge him with rashness, who willed not that He should come into his house, believing that the disease of his servant would depart at His mere command. Therefore He bringing to us a medicine such as should heal our utterly corrupt manners, by miracles procured to Himself authority, by authority obtained Himself belief, by belief drew together a multitude, by a multitude possessed antiquity, by antiquity strengthened religion: so that not only the utterly foolish novelty of heretics dealing deceitfully, but also the inveterate error of the nations opposing with violence, should be unable on any side to rend it asunder.
Source: On the Profit of Believing (New Advent)