Existentialism seems to undermine the possibility of traditional morality.
Existentialism-is a philosophy that emphasizes the uniqueness and isolation of the individual experience in a hostile or indifferent universe, regards human existence as unexplainable, and stresses freedom of choice and responsibility for the consequences of one's acts (Dictionary.com).
Man is the only living creature that is conscious of its own existence. Sartre said that "existentialism is a humanism." By that he meant that the existentialists start from nothing but humanity itself. He also said that man's existence takes priority over whatever he might otherwise be. "Existence takes priority over essence." Man must therefore create himself; create his own nature or "essence", because it is not predetermined already before he is created. Sartre believed that man has no such eternal nature to fall back on. If one could just look in the Bible to find out how to live, it would be very practical. But we can't and we must decide for ourselves how to live. Therefore there isn't a traditional morality. Man must discover his own morality, and it shouldn't be forced onto him like a religion forces traditional morals. .
Sartre said that man feels alien in a world without meaning. Man's feeling of alienation creates a sense of despair, boredom, nausea, and absurdity. Man's freedom is a curse. "Man is condemned to be free," he said. We have not asked to be created as free individuals, and thus freedom forces us to make choices in our lives. There are no eternal values, morals, ethics, or norms we can adhere to, which makes our choices even more significant. When we act inappropriately, we cannot blame it on "the old Adam." We can't because he is merely an image that helps to avoid taking the responsibility for our own actions. Sartre believed that life must have meaning, and we ourselves must create this meaning in our own lives.