Explanation of this quote
This is the conclusion of Sartre in Being and Nothingness: man, as a for-itself which always escapes to him, wants to be in-itself, to give him a nature, in love and lines of bad faith and he wants to coincide with himself, found his being, he wants to be God: a being in-itself-for-itself.
Man, that God in power
However, this human tendency to want to be his own base, to deny the facticity and the fear of freedom is impossible to satisfy: consciousness will always be a void, ever be full. This is why Jean Paul Sartre launches somewhat provocative: “Man is a useless passion.”
Ontologically justified, especially since it is the conclusion of Being and Nothingness, Sartre means the ire of critics who criticize him despair of men to defend an existentialist anti-humanist. Of course, this is wrong: the conference Existentialism is a humanism responds point by point to the criticisms that have been addressed to the book’s release.