What is meant here by saying that existence precedes essence? It means first of all, man exists, turns up, appears on the scene, and, only afterwards, defines himself. If man, as the existentialist conceives him, is indefinable, it is because at first he is nothing. Only afterward will he be something, and he himself will have made what he will be.
Jean-Paul Sartre, Existentialism Is a Humanism
existentialism