Existentialism is a school of philosophical thought and artistic practice which developed in Europe during the 19th and 20th centuries. It explores the nature of human existence, especially focused on its meaning, purpose, and value. It flourished increasingly in the aftermath of World War II, as European intellectuals struggled to make sense of a world destroyed by war and genocide; a seemingly absurd world without clear meaning. As at Nuremberg Nazi leaders denied responsibility for the Holocaust, deflecting culpability to those above them, intellectuals sought philosophies which emphasized interpersonal accountability, freedom of choice, and individual responsibility. In France, existentialism became a prominent intellectual and cultural movement.

Two main figures of this new existentialism were the philosophers (and life partners) Jean-Paul Sartre and Simone de Beauvoir. Sartre and Beauvoir believed that, although humans are all born into a meaningless world, they should not become nihilists (people who believe in the meaningless and futility of life). Instead, they argued that humans have a duty to create a meaningful life through the projects they pursue, to befit themselves and others. Honoring this responsibility—what Sartre called living authentically or in good faith—brings freedom in this philosophy. Human projects are fragile because there is no absolute authority guaranteeing their meaning, and this existential precarity drives some people to seek a sense of security in a higher authority—such as the Nazi Party—or to avoid projects altogether lest they fail.