trans. Jowett (1871)
Then I proceeded to say: Well, but are you aware of the danger which you are incurring? If you were going to commit your body to some one, who might do good or harm to it, would you not carefully consider and ask the opinion of your friends and kindred, and deliberate many days as to whether you should give him the care of your body? But when the soul is in question, which you hold to be of far more value than the body, and upon the good or evil of which depends the well-being of your all,-about this never consulted either with your father or with your brother or with any one of us who are your companions. But no sooner does this foreigner appear, than you instantly commit your soul to his keeping. In the evening, as you say, you hear of him, and in the morning you go to him, never deliberating or taking the opinion of any one as to whether you ought to intrust yourself to him or not;-you have quite made up your mind that you will at all hazards be a pupil of Protagoras, and are prepared to expend all the property of yourself and of your friends in carrying out at any price this determination, although, as you admit, you do not know him, and have never spoken with him: and you call him a Sophist, but are manifestly ignorant of what a Sophist is; and yet you are going to commit yourself to his keeping.
When he heard me say this, he replied: No other inference, Socrates, can be drawn from your words.
I proceeded: Is not a Sophist, Hippocrates, one who deals wholesale or retail in the food of the soul? To me that appears to be his nature.
And what, Socrates, is the food of the soul?
Surely, I said, knowledge is the food of the soul; and we must take care, my friend, that the Sophist does not deceive us when he praises what he sells, like the dealers wholesale or retail who sell the food of the body; for they praise indiscriminately all their goods, without knowing what are really beneficial or hurtful: neither do their customers know, with the exception of any trainer or physician who may happen to buy of them. In like manner those who carry about the wares of knowledge, and make the round of the cities, and sell or retail them to any customer who is in want of them, praise them all alike; though I should not wonder, O my friend, if many of them were really ignorant of their effect upon the soul; and their customers equally ignorant, unless he who buys of them happens to be a physician of the soul. If, therefore, you have understanding of what is good and evil, you may safely buy knowledge of Protagoras or of any one.