Hedonism (Greek, ἡδονή, "pleasure") is a term that refers to either of two distinct but related views, one a thesis in normative ethics, the other a generalization about human psychology.

Ethical Hedonism

The first view, called "ethical hedonism," affirms that only pleasure is intrinsically desirable and that only displeasure (or pain) is intrinsically undesirable. More fully stated, it is the thesis that only pleasant states of mind are desirable in themselves; that only unpleasant states of mind are undesirable in themselves; and that one state of affairs is more desirable in itself than another state of affairs if and only if it contains more (in some sense) pleasant states of mind than the other (the quantity of value in a state of affairs being measured by the quantity of pleasure in it).

This thesis has been defended by a distinguished line of philosophers from the early Greeks to the...