Plato Apology 21

[21] You know Chaerephon, I fancy. 21a He was my comrade from a youth and the comrade of your democratic party, and shared in the recent exile and came back with you. And you know the kind of man Chaerephon was, how impetuous in whatever he undertook. Well, once he went to Delphi and made so bold as to ask the oracle this question; and, gentlemen, don’t make a disturbance at what I say; for he asked if there were anyone wiser than I. Now the Pythia replied that there was no one wiser. And about these things his brother here will bear you witness, since Chaerephon is dead. 21b But see why I say these things; for I am going to tell you whence the prejudice against me has arisen. For when I heard this, I thought to myself: What in the world does the god mean, and what riddle is he propounding? For I am conscious that I am not wise either much or little. What then does he mean by declaring that I am the wisest? He certainly cannot be lying, for that is not possible for him. And for a long time I was at a loss as to what he meant; then with great reluctance I proceeded to investigate him somewhat as follows.
  I went to one of those who had a reputation for wisdom, 21c thinking that there, if anywhere, I should prove the utterance wrong and should show the oracle This man is wiser than I, but you said I was wisest. So examining this man—for I need not call him by name, but it was one of the public men with regard to whom I had this kind of experience, men of Athens —and conversing with him, this man seemed to me to seem to be wise to many other people and especially to himself, but not to be so; and then I tried to show him that he thought 21d he was wise, but was not. As a result, I became hateful to him and to many of those present; and so, as I went away, I thought to myself, I am wiser than this man; for neither of us really knows anything fine and good, but this man thinks he knows something when he does not, whereas I, as I do not know anything, do not think I do either. I seem, then, in just this little thing to be wiser than this man at any rate, that what I do not know I do not think I know either. From him I went to another of those who were reputed 21e to be wiser than he, and these same things seemed to me to be true; and there I became hateful both to him and to many others.
  After this then I went on from one to another, perceiving that I was hated, and grieving and fearing, but nevertheless I thought I must consider the god’s business of the highest importance. So I had to go, investigating the meaning of the oracle, to all those who were reputed to know anything.