Sartre regards existentialism as an optimistic philosophy because it treats human beings as completely free and self-determining. Because there is no such thing as a universal human nature and the individual is always free to make any choice he wishes, anyone can be anything he likes. Since there is no God, human beings have not been created in accordance with some essence that limits the horizon of their possibilities; furthermore, there is no a priori moral law, so human beings are free to decide for themselves what is good and evil and what they will be. The positive side of radical freedom is liberation from tradition, from historical forms of oppression, from trite and insincere moral platitudes, and from determinism based on one’s nature or one’s environment.

There is, however, a price to pay. Man is “condemned to be free—condemned, because he did not create himself, yet nonetheless free, because once cast into the world, he is responsible for everything he does” (29). The reverse side of liberation from determinism is having to take responsibility for one’s actions; as Sartre says, if I am a coward it is I who am to blame, rather than my circumstances or my “poor blood” (39).