Existentialism isn't so atheistic that it wears itself out showing that God doesn't exist. Rather, it declares that even if God did exist, that would change nothing.
Shower on him every blessing, drown him in a sea of happiness, give him economic prosperity such that he should have nothing else to do but sleep, eat cakes, and busy himself with the continuation of the species, and even then, out of sheer ingratitude, sheer spite, man would play you some nasty trick.
The most pressing question on the problem of faith is whether a man as a civilized being can believe in the divinity of the Son of God, Jesus Christ, for therein rests the whole of our faith.
To a commonplace man of limited intellect, for instance, nothing is simpler than to imagine himself an original character, and to revel in that belief without the slightest misgiving.
I must have justice, or I will destroy myself. And not justice in some remote and infinite time and space, but here on Earth...I want to see with my own eyes the lamb lie down with the lion and the victim rise up and embrace his murderer. I want to be there when everyone suddenly understands what it has all been about. All the religions of the world are built on this longing, and I am a believer.
You cannot imagine what sorrow and anger seize one's whole soul when a great idea, which one has long and piously revered, is picked up by some bunglers and dragged into the street, to more fools like themselves, and one suddenly meets it in the flea market, unrecognizable, dirty, askew, absurdly presented, without proportion, without harmony, a toy for stupid children.
For, after all, you do grow up, you do outgrow your ideals, which turn to dust and ashes, which are shattered into fragments; and if you have no other life, you just have to build one up out of these fragments.
But men love abstract reasoning and neat systematization so much that they think nothing of distorting the truth, closing their eyes and ears to contrary evidence to preserve their logical constructions.