The value of life itself cannot be estimated.

Out of damp and gloomy days, out of solitude, out of loveless words directed at us, conclusions grow up in us like fungus: one morning they are there, we know not how, and they gaze upon us, morose and gray. Woe to the thinker who is not the gardener but only the soil of the plants that grow in him.

There would be no sunshine in society if the born flatterers, I mean the so-called amiable people, did not bring it in with them.

That which does not kill us makes us stronger.

There is not enough religion in the world even to destroy religion.

We have no organ at all for knowledge, for truth: we know (or believe or imagine) precisely as much as may be useful in the interest of the human herd, the species: and even what is here called usefulness is in the end only a belief, something imagined and perhaps precisely that most fatal piece of stupidity by which we shall one day perish.

Sleep is no mean art.