*341D* The circumstance that he sails in the ship is not to be taken into account; neither is he to be called a sailor; the name pilot by which he is distinguished has nothing to do with sailing, but is significant of his skill and of his authority over the sailors. Very true, he said. Now, I said, every art has an interest? Certainly. For which the art has to consider and provide? Yes, that is the aim of art. And the interest of any art is the perfection of it--this and nothing else? *341E* What do you mean? I mean what I may illustrate negatively by the example of the body. Suppose you were to ask me whether the body is self-sufficing or has wants, I should reply: Certainly the body has wants; for the body may be ill and require to be cured, and has therefore interests to which the art of medicine ministers; and this is the origin and intention of medicine, as you will acknowledge. Am I not right? *342A* Quite right, he replied. [Sidenote: Art has no imperfection to be corrected, and therefore no extraneous interest.] But is the art of medicine or any other art faulty or deficient in any quality in the same way that the eye may be deficient in sight or the ear fail of hearing, and therefore requires another art to provide for the interests of seeing and hearing--has art in itself, I say, any similar liability to fault or defect, and does every art require another supplementary art to provide for its interests, and that another and another without end? Or have the arts to look only *342B* after their own interests? Or have they no need either of themselves or of another?--having no faults or defects, they have no need to correct them, either by the exercise of their own art or of any other; they have only to consider the interest of their subject-matter. For every art remains pure and faultless while remaining true--that is to say, while perfect and unimpaired. Take the words in your precise sense, and tell me whether I am not right. Yes, clearly. [Sidenote: Illustrations.] *342C* Then medicine does not consider the interest of medicine, but the interest of the body? {20} True, he said. Nor does the art of horsemanship consider the interests of the art of horsemanship, but the interests of the horse; neither do any other arts care for themselves, for they have no needs; they care only for that which is the subject of their art? True, he said. But surely, Thrasymachus, the arts are the superiors and rulers of their own subjects? To this he assented with a good deal of reluctance. Then, I said, no science or art considers or enjoins the interest of the stronger or superior, but only the interest *342D* of the subject and weaker? He made an attempt to contest this proposition also, but finally acquiesced.