[From Latin existentialis: pertaining to existence.]
(ethics) An influential movement in 20th-century ethics holding that values are not universal but instead that each person must create his or her own values as a result of living life. Its guiding phrase, formulated by Jean-Paul Sartre (1905-1980), was "existence precedes essence". Although existentialism was a form of individualism, it was also very much a kind of pessimism and opposed to any attempt at ethical naturalism since it held that there is no stable human nature and therefore that there are no common human values. Some existentialists reveled in the unplanned, haphazard character of experience and therefore could be characterized as proponents of irrationalism or even nihilism. Existentialists were also opponents of eudaimonism, since they thought that the quest for happiness is a bourgeois pursuit showing "bad faith".