If a man loves a woman for her beauty, does he love her? No; for the smallpox, which destroys her beauty without killing her, causes his love to cease. And if any one loves me for my judgment or my memory, does he really love me? No; for I can lose these qualities without ceasing to be.

If you want to be a real seeker of truth, you need to, at least once in your lifetime, doubt in, as much as it's possible, in everything.

What a chimaera then is man, what a novelty, what a monster, what chaos, what a subject of contradiction, what a prodigy! Judge of all things, yet an imbecile earthworm; depository of truth, yet a sewer of uncertainty and error; pride and refuse of the universe. Who shall resolve this tangle?

Contradiction is not a sign of falsity, nor the lack of contradiction a sign of truth.

Can anything be stupider than that a man has the right to kill me because he lives on the other side of a river and his ruler has a quarrel with mine, though I have not quarrelled with him?

Nothing is so insufferable to man as to be completely at rest, without passions, without business, without diversion, without study. He then feels his nothingness, his forlornness, his insufficiency, his dependence, his weakness, his emptiness. There will immediately arise from the depth of his heart weariness, gloom, sadness, fretfulness, vexation, despair.

The sum of a man's problems come from his inability to be alone in a silent room.