Republic

Let no one then, said I, disconcert us when off our guard with the objection that everybody desires not drink but good drink and not food but good food, because (the argument will run) all men desire good, and so, if thirst is desire, it would be of good drink or of good whatsoever it is; and so similarly of other desires. Why, he said, there perhaps would seem to be something in that objection. But I need hardly remind you, said I, that of relative terms those that are somehow qualified are related to a qualified correlate, those that are severally just themselves to a correlate that is just itself. I don’t understand, he said. Don’t you understand, said I, that the greater is such as to be greater than something? Certainly. Is it not than the less? Yes. But the much greater than the much less. Is that not so? Yes. And may we add the one time greater than the one time less and that which will be greater than that which will be less? Surely. And similarly of the more towards the fewer, and the double towards the half and of all like cases, and again of the heavier towards the lighter, the swifter towards the slower, and yet again of the hot towards the cold and all cases of that kind, does not the same hold? By all means. But what of the sciences? Is not the way of it the same? Science which is just that, is of knowledge which is just that, or is of whatsoever we must assume the correlate of science to be. But a particular science of a particular kind is of some particular thing of a particular kind. I mean something like this: As there was a science of making a house it differed from other sciences so as to be named architecture. Certainly. Was not this by reason of its being of a certain kind such as no other of all the rest? Yes. And was it not because it was of something of a certain kind that it itself became a certain kind of science? And similarly of the other arts and sciences? That is so. This then, said I, if haply you now understand, is what you must say I then meant, by the statement that of all things that are such as to be of something those that are just themselves only are of things just themselves only, but things of a certain kind are of things of a kind. And I don’t at all mean that they are of the same kind as the things of which they are, so that we are to suppose that the science of health and disease is a healthy and diseased science and that of evil and good, evil and good. I only mean that as science became the science not of just the thing of which science is but of some particular kind of thing, namely, of health and disease, the result was that it itself became some kind of science and this caused it to be no longer called simply science but with the addition of the particular kind, medical science. I understand, he said, and agree that it is so.