g 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.

And it has this particular quality because it has an object of a
particular kind; and this is true of the other arts and sciences?

Yes.

Now, then, if I have made myself clear, you will understand my original
meaning in what I said about relatives. My meaning was, that if one term
of a relation is taken alone, the other is taken alone; if one term
is qualified, the other is also qualified. I do not mean to say that
relatives may not be disparate, or that the science of health is
healthy, or of disease necessarily diseased, or that the sciences of
good and evil are therefore good and evil; but only that, when the term
science is no longer used absolutely, but has a qualified object which
in this case is the nature of health and disease, it becomes defined,
and is hence called not merely science, but the science of medicine.

I quite understand, and I think as you do.

Would you not say that thirst is one of these essentially relative
terms, having clearly