And he who would enquire into the nature of medicine must pursue the enquiry into health and disease, and not into what is extraneous? True. And he who judges rightly will judge of the physician as a physician in what relates to these? He will. He will consider whether what he says is true, and whether what he does is right, in relation to health and disease? He will. But can any one attain the knowledge of either unless he have a knowledge of medicine? He cannot. No one at all, it would seem, except the physician can have this knowledge; and therefore not the wise man; he would have to be a physician as well as a wise man. Very true. Then, assuredly, wisdom or temperance, if only a science of science, and of the absence of science or knowledge, will not be able to distinguish the physician who knows from one who does not know but pretends or thinks that he knows, or any other professor of anything at all; like any other artist, he will only know his fellow in art or wisdom, and no one else. That is evident, he said. But then what profit, Critias, I said, is there any longer in wisdom or temperance which yet remains, if this is wisdom? If, indeed, as we were supposing at first, the wise man had been able to distinguish what he knew and did not know, and that he knew the one and did not know the other, and to recognize a similar faculty of discernment in others, there would certainly have been a great advantage in being wise; for then we should never have made a mistake, but have passed through life the unerring guides of ourselves and of those who are under us; and we should not have attempted to do what we did not know, but we should have found out those who knew, and have handed the business over to them and trusted in them; nor should we have allowed those who were under us to do anything which they were not likely to do well; and they would be likely to do well just that of which they had knowledge; and the house or state which was ordered or administered under the guidance of wisdom, and everything else of which wisdom was the lord, would have been well ordered; for truth guiding, and error having been eliminated, in all their doings, men would have done well, and would have been happy. Was not this, Critias, what we spoke of as the great advantage of wisdom--to know what is known and what is unknown to us? Very true, he said. And now you perceive, I said, that no such science is to be found anywhere. I perceive, he said.