In philosophy, two different theories are labeled egoism: psychological egoism is the view that one is always motivated to act in one's own best interests, while ethical egoism is the view that one ought to always act that way.

Generally, the term egoism has been used with pejorative connotations; it has been applied to philosophers such as Bernard de Mandeville and to many other materialists of his generation, but none of them declared themselves as such. The first Western philosopher to apply the label of egoism to his or her own work was Max Stirner—although he did, in effect, re-invent the meaning of the term to suit his philosophy.

In eastern philosophy, the debate around equivalent terms has been somewhat broader, not merely questioning the ethical validity of "serving oneself", but questioning what the self is, and whether such an entity can be defined or presumed to exist. Debates of this kind span Hinduism, Buddhism, and Neo-Taoism . See: atman, anatman, pudgalavada.