CONCEPT
Existence Precedes Essence
Sartre's foundational thesis: the human being appears in the world first and only afterward, through freely made choices, acquires the properties that constitute what she is.
The most famous formula of existentialist philosophy reverses the essentialist tradition that runs from Plato through Aquinas to the Enlightenment. Where the essentialist holds that each being has a nature — a defining set of properties and purposes — that precedes and explains its concrete existence, Sartre insists that for human beings the order is reversed. The human being is not manufactured according to a design, does not discover a predetermined purpose, does not inherit a fixed nature. She exists first. Only then, through the accumulated weight of her choices, does she acquire an essence — a specific configuration of character, commitments, and capabilities that makes her the particular person she has become. The essence is never final; it is always being constituted through ongoing choice.
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The formula compresses a philosophical revolution. Western thought from Aristotle through medieval theology treated human beings as creatures with a determinate nature — rational animals, imago Dei, bearers of a specific telos. Even Enlightenment