Sartre argues that man wills what he is, providing theory for radical freedom. He writes, "when operating on the level of complete authenticity, I have acknowledged that existence precedes essence, and that man is a free being who, under any circumstances, can only ever will his freedom, I have at the same time acknowledged that I must will the freedom of others."
In asserting that Existentialism is a Humanism Sartre means that it places the human being at the center of its attention and at the apex of its value hierarchy. Our ultimate goal should be to foster the freedom of the individual.
Sartre's famous lecture in October 1945 :
The talk started by proclaiming "existence precedes essence", he explained this meant that individuals create their own values because there is no moral order in the universe. This freedom is the ultimate value.