1) Post-World War II Europe was in a state of despair over the human costs of war and revelations of Nazi atrocities. 2) This disillusionment led many to turn to existentialist philosophy, like that of Jean-Paul Sartre, which proclaimed that without God, humans must define their own existence. 3) Sartre rejected the idea of a predefined human essence or nature, arguing that through our choices and actions, we invent ourselves.