And when we speak of “abandonment” – a favorite word of Heidegger – we only mean to say that God does not exist, and that it is necessary to draw the consequences of his absence right to the end. The existentialist is strongly opposed to a certain type of secular moralism which seeks to suppress God at the least possible expense.

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The existentialist… finds it extremely embarrassing that God does not exist, for there disappears with Him all possibility of finding values in an intelligible heaven. There can no longer be any good a priori, since there is no infinite and perfect consciousness to think it. It is nowhere written that “the good” exists, that one must be honest or must not lie, since we are now upon the plane where there are only men. Dostoevsky once wrote “If God did not exist, everything would be permitted”; and that, for existentialism, is the starting point… For if indeed existence preceeds essence, one will never be able to explain one’s action by reference to a given and specific human nature; in other words, there is no determinism – man is free, man is freedom.

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…To choose an adviser is nevertheless to commit oneself by that choice… You are free, therefore choose – that is to say, invent. No rule of general morality can show you what you ought to do: no signs are vouchsafed in this world. The Catholics will reply, “oh, but they are!” Very well; still, it is I myself, in every case, who have to interpret the signs.

While I was imprisoned, I made the acquaintance of a somewhat remarkable man, a Jesuit, who had become a member of that order in the following manner. In his life he had suffered a succession of rather severe setbacks. His father had died when he was a child, leaving him in poverty, and he had been awarded a free scholarship in a religious institution, where he had been made continually to feel that he was accepted for charity’s sake, and, in consequence, he had been denied several of those distinctions and honours which gratify children. Later, about the age of eighteen, he came to grief in a sentimental affair; and finally, at twenty-two – this was a trifle in itself, but it was the last drop that overflowed his cup – he failed in his military examination. This young man, then, could regard himself as a total failure: it was a sign – but a sign of what? He might have taken refuge in bitterness or despair. But he took it – very cleverly for him – as a sign that he was not intended for secular successes, and that only the attainments of religion, those of sanctity and of faith, were accessible to him.

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Existentialism is not atheist in the sense that it would exhaust itself in demonstrations of the non-existence of God. It declares, rather, that even if God existed that would make no difference from its point of view. Not that we believe God does exist, but we think that the real problem is not that of His existence; what man needs is to find himself again and to understand that nothing can save him from himself, not even a valid proof of the existence of God. In this sense existentialism is optimistic. It is a doctrine of action, and it is only by self-deception, by confusing their own despair with ours that Christians can described us as without hope.

– Jean-Paul Sartre