Jean-Paul Charles Aymard Sartre was a French philosopher, playwright, novelist, screenwriter, political activist, biographer, and literary critic. He was one of the key figures in the philosophy of existentialism and phenomenology, and one of the leading figures in 20th-century French philosophy and Marxism. His work has also influenced sociology, critical theory, post-colonial theory, and literary studies, and continues to influence these disciplines.
Sartre was also noted for his open relationship with prominent feminist and fellow existentialist philosopher and writer Simone de Beauvoir. Together, Sartre and de Beauvoir challenged the cultural and social assumptions and expectations of their upbringings, which they considered bourgeois, in both lifestyles and thought. The conflict between oppressive, spiritually destructive conformity and an "authentic" way of "being" became the dominant theme of Sartre's early work, a theme embodied in his principal philosophical work Being and Nothingness. Sartre's introduction to his philosophy is his work Existentialism Is a Humanism, originally presented as a lecture.