But in the satisfaction of the animal appetites that which is active is not that part of our faculties 204 or of our nature which is in want, but that part which is in its normal state; for there are pleasures which involve no previous pain or appetite, such as those of philosophic study, wherein our nature is not conscious of any want.

This is corroborated by the fact that while our natural wants are being filled we do not take delight in the same things which delight us when that process has been completed: when the want has been filled we take delight in things that are pleasant in themselves, while it is being filled in their opposites; for we then take delight in sharp and bitter things, none of which are naturally pleasant or pleasant in themselves. The pleasures, then, which these things give are not real pleasures; for pleasures are related to one another as the things that produce them.