To be told, you are responsible for the period of history that you are living in. You have not only the right to choose, but the duty to choose and if you are now surrounded by poverty, by war, by oppression, by cruelty – that is what you have chosen. Sartre was the leading advocate of atheistic existentialism in France but he was also interested in the novel, drama, literary criticism and politics.He is best remembered for his philosophical works and his idea of communistic existentialism which he expressed in novels and plays such as his debut novel Nausea (1939), which depicted man adrift in a godless universe, hostage to his own freedom. He had a long term affair with the feminist philosopher, Simone de Beauvoir, and together they were at the center of French intellectual life from the late 1920s onwards. His great philosophical work is Being and Nothingness (1956). Like Kierkegaard and Heidegger, Sartre emphasized the burden of individual personal freedom: that although we can’t escape the fact of our situation, we are free to change it. He drew a distinction between the unconscious and the conscious.
After the Second World War, during which he fought for the Resistance, he became increasingly interested in Marxism and his involvement with the French Communist party was part of his desire to overcome the economic and social “structures of choice” which he found restricting. His main contribution to Marxism is Critique of Dialectical Reason (1960). Sartre refused the 1964 Nobel Prize in literature on “personal grounds”, but is later said to have accepted it.
(Excerpt from bbc.co.uk)