SOCRATES: The possibility of error will be more distinctly recognised, if we put the question in reference to the whole class under which the good or expedient falls. That whole class has to do with the future, and laws are passed under the idea that they will be useful in after-time; which, in other words, is the future.
THEODORUS: Very true.
SOCRATES: Suppose now, that we ask Protagoras, or one of his disciples, a question:—O, Protagoras, we will say to him, Man is, as you declare, the measure of all things—white, heavy, light: of all such things he is the judge; for he has the criterion of them in himself, and when he thinks that things are such as he experiences them to be, he thinks what is and is true to himself. Is it not so?
THEODORUS: Yes.
SOCRATES: And do you extend your doctrine, Protagoras (as we shall further say), to the future as well as to the present; and has he the criterion not only of what in his opinion is but of what will be, and do things always happen to him as he expected? For example, take the case of heat:—When an ordinary man thinks that he is going to have a fever, and that this kind of heat is coming on, and another person, who is a physician, thinks the contrary, whose opinion is likely to prove right? Or are they both right?—he will have a heat and fever in his own judgment, and not have a fever in the physician's judgment?
THEODORUS: How ludicrous!
SOCRATES: And the vinegrower, if I am not mistaken, is a better judge of the sweetness or dryness of the vintage which is not yet gathered than the harp-player?
THEODORUS: Certainly.
SOCRATES: And in musical composition the musician will know better than the training master what the training master himself will hereafter think harmonious or the reverse?
THEODORUS: Of course.