Plato, Protagoras

[313a] I then went on to say: Now tell me, are you aware upon what sort of hazard you are going to stake your soul? If you had to entrust your body to someone, taking the risk of its being made better or worse, you would first consider most carefully whether you ought to entrust it or not, and would seek the advice of your friends and relations and ponder it for a number of days: but in the case of your soul, which you value much more highly than your body, and on which depends the good or ill condition of all your affairs, according as it is made better or worse, would you omit to consult first with either your father [313b] or your brother or one of us your comrades,—as to whether or no you should entrust your very soul to this newly-arrived foreigner; but choose rather, having heard of him in the evening, as you say, and coming to me at dawn, to make no mention of this question, and take no counsel upon it—whether you ought to entrust yourself to him or not; and are ready to spend your own substance and that of your friends, in the settled conviction that at all costs you must converse with Protagoras, whom you neither know, as you tell me, nor have ever met in argument before, [313c] and whom you call “sophist,” in patent ignorance of what this sophist may be to whom you are about to entrust yourself?

When he heard this he said: It seems so, Socrates, by what you say.

Then can it be, Hippocrates, that the sophist is really a sort of merchant or dealer in provisions on which a soul is nourished? For such is the view I take of him.

With what, Socrates, is a soul nourished?

With doctrines, presumably, I replied. And we must take care, my good friend, that the sophist, in commending his wares, does not deceive us, as both merchant and dealer do in the case of our bodily food. [313d] For among the provisions, you know, in which these men deal, not only are they themselves ignorant what is good or bad for the body, since in selling they commend them all, but the people who buy from them are so too, unless one happens to be a trainer or a doctor. And in the same way, those who take their doctrines the round of our cities, hawking them about to any odd purchaser who desires them, commend everything that they sell, and there may well be some of these too, my good sir, who are ignorant which of their wares is [313e] good or bad for the soul; and in just the same case are the people who buy from them, unless one happens to have a doctor's knowledge here also, but of the soul. So then, if you are well informed as to what is good or bad among these wares, it will be safe for you to buy doctrines from Protagoras or from anyone else you please: but if not, take care, my dear fellow, that you do not risk your greatest treasure on a toss of the dice.