There Is No Reality Except In

From Existentialism Is a Humanism (1945, published 1946). Sartre makes this declaration in direct response to the criticism that existentialism encourages passivity and quietism. He argues the exact opposite: because existence precedes essence, a person is nothing but the ensemble of their actions — dreams, intentions, and potential count for nothing until they are realized in the world. This is also Sartre's answer to the question of what a human being is: not a fixed nature but an ongoing project, defined entirely by what it does rather than what it feels or imagines itself to be.