Protagoras

“…knowledge is the food of the soul; and we must take care, my friend, that the sophist does not cheat us when he praises the goods he is hawking, like the wholesalers and retailers who sell the food for the body; for they praise indiscriminately all their goods, without knowing which are really beneficial or harmful; and neither do their customers know, with the exception of a trainer or doctor who may happen to buy some of them.“

“For there is far greater peril in buying knowledge than in buying food or drink: the latter you buy from the wholesale or retail dealer, and carry away in independent containers, and before you take them into your body as food or drink you can bring them home and call in any experienced friend who knows what is good to be eaten or drunk, and what not, and how much, and when; and then the danger of purchasing them is not so great. But you cannot buy the wares of knowledge and carry them away in an independent container; when you have paid for them, you must receive them into your soul and go your way, either harmed or benefited; and therefore we should deliberate and get the advice of our elders; for we are still young — too young to decide such a matter.“

“…those who are present at such discussions ought to be impartial hearers of both the speakers; remembering, however, that impartiality is not the same as equality, for both sides should be impartially heard, and yet an equal prize should not be assigned to both of them; but to the wiser a greater should be given, and a lower to the less learned.“

“Now bad men, when [a frustration] befalls them, view it with malignant joy, and gleefully censure and expose and denounce the wickedness of their parents or their country, under the idea that the rest of mankind will be less likely to criticize themselves and accuse them of the neglect of which they are guilty; and in consequence they exaggerate their parents’ (or country’s) defects beyond what they deserve, and add optional animosities over and above the compulsary ones.“

“Now isn’t ignorance to have a false opinion and to be deceived about important matters?

To this they also unanimously assented.

Then, I said, no man voluntarily purstes evil, or what he thinks to be evil. To prefer what he believes evil to d good, it appears, is not in human nature; and when compelled to choose one of two evils, no one will choose the greater when it is possible to have the lesser.”