I have had no regular disciples: but if anyone likes to come and hear me while I am pursuing my mission, whether he be young or old, he may freely come. Nor do I converse with those who pay only, and not with those who do not pay; but anyone, whether he be rich or poor, may ask and answer me and listen to my words; and whether he turns out to be a bad man or a good one, that cannot be justly laid to my charge, as I never taught him anything. And if anyone says that he has ever learned or heard anything from me in private which all the world has not heard, I should like you to know that he is speaking an untruth.

33a–b - Plato - Apology