Man is condemned to be free; because once thrown into the world, he is responsible for everything he does. It is up to you to give [life] a meaning. - Jean-Paul Sartre

L'existentialiste, au contraire, pense qu'il est très gênant que Dieu n'existe pas, car avec lui disparaît toute possibilité de trouver des valeurs dans un ciel intelligible; il ne peut plus y avoir de bien a priori, puisqu'il n'y a pas de conscience infinie et parfaite pour le penser; il n'est écrit nulle part que le bien existe, qu'il faut être honnête, qu'il ne faut pas mentir, puisque précisément nous sommes sur un plan où il y a seulement des hommes.

When you live alone, you even forget what it is to tell a story: plausibility disappears at the same time as friends. You let events flow by too: you suddenly see people appear who speak and then go away; you plunge into stories of which you can't make head or tail: you'd make a terrible witness. But on the other hand, everything improbable, everything which nobody would ever believe in a cafe, comes your way.

If existence really does precede essence, there is no explaining things away by reference to a fixed and given human nature. In other words, there is no determinism, man is free, man is freedom. On the other hand, if God does not exist, we find no values or commands to turn to which legitimize our conduct. So, in the bright realm of values, we have no excuse behind us, nor justification before us. We are alone, with no excuses.