Jean-Paul Sartre's life and work were significant in philosophy, particularly in developing existentialism. His experiences during World War II and his exploration of freedom and responsibility influenced his major works, including "Being and Nothingness." Sartre's assertion that "existence precedes essence" challenged traditional philosophical doctrines, emphasizing individual choice and authenticity. His ideas not only shaped existential thought but also resonated throughout literature, politics, and social movements in the 20th century, making Sartre a monumental figure.