Sayings of Socrates 23

So now, Athenian men, more than on my own behalf must I defend myself, as some may think, but on your behalf, so that you may not make a mistake concerning the gift of the god by condemning me. 

For if you kill me, you will not easily find another such person at all, even if to say in a ludicrous way, attached on the city by the god, like on a large and well-bred horse, by its size and laziness both needing arousing by some gadfly; in this way the god seems to have fastened me on the city, some such one who arousing and persuading and reproaching each one of you I do not stop the whole day, settling down all over. 

Thus such another will not easily come to you, men, but if you believe me, you will spare me; but perhaps you might possibly be offended, like the sleeping who are awakened, striking me, believing Anytus, you might easily kill, then the rest of your lives you might continue sleeping, unless the god caring for you should send you another.

—Plato, Apology 30e