Jean-Paul Sartre. Existentialism is a humanism (№ 409323)

Existentialists, on the other hand, are worried about the absence of God, since with God every opportunity to find any values in the intelligible world disappears. There can be no more good a priori, since there is no infinite and perfect mind that would think of it. And nowhere is it written that the good exists, that one must be honest, that one must not lie; and this is precisely because we are on a plain, and only people live on this plain.