And I daresay you are referring to my instance of a moment ago, the man who knows all that is to come, the prophet. Do you refer to him or to someone else? Yes, I refer to him, he said, and someone else too. Whom? I asked. Is it the sort of person who might know, besides what is to be, both everything that has been and now is, and might be ignorant of nothing? Let us suppose such a man exists: you are not going to tell me, I am sure, of anyone alive who is yet more knowing than he. No, indeed. Then there is still one more thing I would fain know: which of the sciences is it that makes him happy? Or does he owe it to all of them alike? By no means to all alike, he replied. But to which sort most? One that gives him knowledge of what thing, present, past or future? Is it that by which he knows draught-playing? Draught-playing indeed! he replied.Well, reckoning? By no means. Well, health? More likely, he said. And that science to which I refer as the most likely, I went on, gives him knowledge of what? Of good, he replied, and of evil. Vile creature! I said, you have all this time been dragging me round and round, while concealing the fact that the life according to knowledge does not make us do well and be happy, not even if it be knowledge of all the other knowledges together, but only if it is of this single one concerning good and evil. For, Critias, if you choose to take away this science from the whole number of them, will medicine any the less give us health, or shoemaking give us shoes, or weaving provide clothes, or will the pilot’s art any the less prevent the loss of life at sea, or the general’s in war? None the less, he replied. But, my dear Critias, to have any of these things well and beneficially done will be out of our reach if that science is lacking. That is true. And that science, it seems, is not temperance, but one whose business is to benefit us; for it is not a science of sciences and lack of sciences, but of good and evil: so that if this is beneficial, temperance must be something else to us. But why, he asked, should not it be beneficial? For if temperance is above all a science of the sciences, and presides too over the other sciences, surely she will govern this science of the good, and so benefit us. And give us health also? I asked: will she, and not medicine, do this? And will the several works of the other arts be hers, and not the particular works of each art? Have we not constantly protested that she is only knowledge of knowledge and of lack of knowledge, and of nothing else? Is not that so? Apparently it is. Then she will not be a producer of health? No, indeed.