4. Plato makes the true and subtle remark that the physician had better not be in robust health; and should have known what illness is in his own person. But the judge ought to have had no similar experience of evil; he is to be a good man who, having passed his youth in innocence, became acquainted late in life with the vices of others. And therefore, according to Plato, a judge should not be young, just as a young man according to Aristotle is not fit to be a hearer of moral philosophy. The bad, on the other hand, have a knowledge of vice, but no knowledge {lii} of virtue. It may be doubted, however, whether this train of reflection is well founded. In a remarkable passage of the Laws (xii. 950 B) it is acknowledged that the evil may form a correct estimate of the good. The union of gentleness and courage in Book ii. at first seemed to be a paradox, yet was afterwards ascertained to be a truth. And Plato might also have found that the intuition of evil may be consistent with the abhorrence of it (cp. infra, ix. 582). There is a directness of aim in virtue which gives an insight into vice. And the knowledge of character is in some degree a natural sense independent of any special experience of good or evil. 5. One of the most remarkable conceptions of Plato, because un-Greek and also very different from anything which existed at all in his age of the world, is the transposition of ranks. In the Spartan state there had been enfranchisement of Helots and degradation of citizens under special circumstances. And in the ancient Greek aristocracies, merit was certainly recognized as one of the elements on which government was based. The founders of states were supposed to be their benefactors, who were raised by their great actions above the ordinary level of humanity; at a later period, the services of warriors and legislators were held to entitle them and their descendants to the privileges of citizenship and to the first rank in the state. And although the existence of an ideal aristocracy is slenderly proven from the remains of early Greek history, and we have a difficulty in ascribing such a character, however the idea may be defined, to any actual Hellenic state--or indeed to any state which has ever existed in the world--still the rule of the best was certainly the aspiration of philosophers, who probably accommodated a good deal their views of primitive history to their own notions of good government. Plato further insists on applying to the guardians of his state a series of tests by which all those who fell short of a fixed standard were either removed from the governing body, or not admitted to it; and this 'academic' discipline did to a certain extent prevail in Greek states, especially in Sparta. He also indicates that the system of caste, which existed in a great part of the ancient, and is by no means extinct in the modern European world, should be set aside from time to time in favour of merit.