The Republic by Plato Part 4 Page 66

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 a relation —

Yes, thirst is relative to drink.

And a certain kind of thirst is relative to a certain kind of drink; but thirst taken alone is neither of much nor little, nor of good nor bad, nor of any particular kind of drink, but of drink only?