Egoism is a philosophy concerned with the role of the self, or ego, as the motivation and goal of one's own action. Different theories of egoism encompass a range of disparate ideas and can generally be categorized into descriptive or normative forms. That is, they may be interested in either describing that people do act in self-interest or prescribing that they should. Other definitions of egoism may instead emphasise action according to one's will rather than one's self-interest, and furthermore posit that this is a truer sense of egoism.