To succeed in the world it is not enough to be stupid, you must also be well-mannered.

Monsieur l'abbé, I detest what you write, but I would give my life to make it possible for you to continue to write.

There is an astonishing imagination, even in the science of mathematics. ... We repeat, there was far more imagination in the head of Archimedes than in that of Homer.

Beware of the words "internal security," for they are the eternal cry of the oppressor.

I have been a hundred times on the point of killing myself, but still was fond of life. This ridiculous weakness is perhaps one of our worst instincts. What can be more absurd than choosing to carry a burden that one really wants to throw to the ground? To detest, and yet to strive to preserve our existence? To caress the serpent that devours us, and hug him close to our bosoms till he has gnawed into our hearts?

Now, you receive all your ideas; therefore you receive your wish, you wish therefore necessarily. The word "liberty" does not therefore belong in any way to your will....The will, therefore, is not a faculty that one can call free. A free will is an expression absolutely void of sense, and what the scholastics have called will of indifference, that is to say willing without cause, is a chimera unworthy of being combated.

Which is more dangerous: fanaticism or atheism? Fanaticism is certainly a thousand times more deadly; for atheism inspires no bloody passion whereas fanaticism does; atheism is opposed to crime and fanaticism causes crimes to be committed.