Plato: The Republic

4. BOOK IV (continued)

But here a confusion may arise; and I should wish to guard against an opponent starting up and saying that no man desires drink only, but good drink, or food only, but good food; for good is the universal object of desire, and thirst being a desire, will necessarily be thirst after good drink; and the same is true of every other desire.

Yes, he replied, the opponent might have something to say.

Nevertheless I should still maintain, that of relatives some have a quality attached to either term of the relation; others are simple and have their correlatives simple.

I do not know what you mean.

Well, you know of course that the greater is relative to the less?

Certainly.

And the much greater to the much less?

Yes.

And the sometime greater to the sometime less, and the greater that is to be to the less that is to be?

Certainly, he said.

And so of more and less, and of other correlative terms, such as the double and the half, or again, the heavier and the lighter, the swifter and the slower; and of hot and cold, and of any other relatives;--is not this true of all of them?

Yes.

And does not the same principle hold in the sciences? The object of science is knowledge (assuming that to be the true definition), but the object of a particular science is a particular kind of knowledge; I mean, for example, that the science of house-building is a kind of knowledge which is defined and distinguished from other kinds and is therefore termed architecture.

Certainly.

Because it has a particular quality which no other has?

Yes.