“By learning,” I replied. “But we must take care, my friend, that the sophist does not deceive us by praising what he sells, as those others do with respect to nutriment for the body, the merchant and the retailer. For neither do they themselves know which of the commodities in which they traffic are good or bad for the body, though they praise all that they sell, nor do those who buy from them, unless one happens to be a professor of gymnastics or a physician. In like manner, those who hawk about learning through cities, and who sell and retail it to every one that desires it, praise all that they sell, though perhaps some of these too, my excellent friend, may be ignorant which of the things they sell is good or bad for the soul; and this also may be the case with those that buy from them, unless some one happen to be skilled in the medicine of the soul. 13. If then you happen to know which of these is good or bad, you may safely buy learning from Protagoras or any one else; but if not, beware my good friend, that you do not hazard and imperil that which is most precious. For there is much greater danger in the purchase of learning than in that of food. For when one has purchased meat and drink from a retailer or merchant one may take them away in different vessels, and, before receiving them into one’s body by eating or drinking, one may set them down at home, and calling in some person who understands the matter, consult him as to what may be eaten and drunk, and what not, and how much and when; so that in this purchase there is no great danger. But it is not possible to carry away learning in a different vessel; but it is necessary, when one has paid the price, having received instruction in the soul itself and learnt it, to depart either injured or benefited. 14. Let us therefore consider these things with persons older than we are: for we are too young to decide on a matter of such importance. Now however, since we have made up our minds, let us go and hear the man, and after we have heard him, let us communicate with others. For not only is Protagoras there, but Hippias of Elis, and I think also Prodicus of Ceos, and many other wise men.”