De Beauvoir taught high school while developing the basis for her philosophical thought between 1931 and 1943. Following in the tradition of the 18th century 'gadfly' philosophe's, De Beauvoir used her background in formal philosophy to voice her sentiments on feminism and existentialism. Jean-Paul Sartre and De beauvoir met after her studies in the Sorbonne, the beginning of a friendship which lasted until his death in 1980. She also draws heavily on his conception of human beings as creatures who are free. Freedom of choice, humanity's utmost value, is the criterion for morality and immorality in one's acts.
Good acts increase one's freedom, while bad ones limit that freedom.
No doubt, her linkage to Sartre was the reason that she received the unwanted title of existentialist. Her major thrust into philosophical analysis was due to her life-long friendship with Sartre. Using some of the ideas she worked with in Ethics and a few of the underpinnings of existentialism as described by Sartre, she went on to produce her famous work, The Second Sex. This was the definitive declaration of woman's independence. Her other works include a four part autobiography, a prize winning novel called The Mandarins, and a novel condemning society for its treatment of the elderly, The Coming of Age.