Plato, Republic

[342a] “Correct,” he said. “But how about this? Is the medical art itself defective or faulty, or has any other art any need of some virtue, quality, or excellence—as the eyes of vision, the ears of hearing, and for this reason is there need of some art over them that will consider and provide what is advantageous for these very ends—does there exist in the art itself some defect and does each art require another art to consider its advantage and is there need of still another for the considering art and so on ad infinitum, or will the art look out for its own advantage? [342b] Or is it a fact that it needs neither itself nor another art to consider its advantage and provide against its deficiency? For there is no defect or error at all that dwells in any art. Nor does it befit an art to seek the advantage of anything else than that of its object. But the art itself is free from all harm and admixture of evil, and is right so long as each art is precisely and entirely that which it is. And consider the matter in that precise way of speaking. Is it so or not?” “It appears to be so,” he said. “Then medicine,” said I, [342c] “does not consider the advantage of medicine but of the body?” “Yes.” “Nor horsemanship of horsemanship but of horses, nor does any other art look out for itself—for it has no need—but for that of which it is the art.” “So it seems,” he replied. “But surely,¹ Thrasymachus, the arts do hold rule and are stronger than that of which they are the arts.” He conceded this but it went very hard. “Then no art considers or enjoins² the advantage of the stronger but every art that of the weaker [342d] which is ruled by it.” This too he was finally brought to admit though he tried to contest it. But when he had agreed—“Can we deny, then,” said I, “that neither does any physician in so far as he is a physician seek or enjoin the advantage of the physician but that of the patient? For we have agreed that the physician, 'precisely' speaking, is a ruler and governor of bodies and not a moneymaker. Did we agree on that?” He assented. “And so the 'precise' pilot is a ruler of sailors, [342e] not a sailor?” That was admitted. “Then that sort of a pilot and ruler will not consider and enjoin the advantage of the pilot but that of the sailor whose ruler he is.” He assented reluctantly. “Then,” said I, “Thrasymachus, neither does anyone in any office of rule in so far as he is a ruler consider and enjoin his own advantage but that of the one whom he rules and for whom he exercises his craft, and he keeps his eyes fixed on that and on what is advantageous and suitable to that in all that he says and does.”