21 This, you will say, is ridiculous, whereas all profess to hold and teach this: all heretics make this profession, I cannot deny it; but so, as that they promise to those whom they entice, that they will give them a reason concerning matters the most obscure: and on this account chiefly charge the Catholic [Church], that they who come to her are enjoined to believe; but they make it their boast, that they impose not a yoke of believing, but open a fount of teaching.
You answer, What could be said, that should pertain more to their praise? It is not so. For this they do, without being endued with any strength, but in order to conciliate to themselves a crowd by the name of reason: on the promise of which the human soul naturally is pleased, and, without considering its own strength and state of health, by seeking the food of the sound, which is ill entrusted save to such as are in health, rushes upon the poisons of them who deceive. For true religion, unless those things be believed, which each one after, if he shall conduct himself well and shall be worthy, attains unto and understands, and altogether without a certain weighty power of authority, can in no way be rightly entered upon.
Source: On the Profit of Believing (New Advent)