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 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.
Illustrations. Then medicine does not consider the interest of medicine, but the interest of the body?
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 of the