Quand celui à qui l'on parle ne comprend pas et celui qui parle ne se comprend pas, c'est de la métaphysique When he to whom a person speaks does not understand, and he who speaks does not understand himself, that is metaphysics.

The monster, fanaticism, still exists, and whoever seeks after truth will run the risk of being persecuted.

Every abuse ought to be reformed, unless the reform is more dangerous than the abuse itself.

If you wish to obtain a great name or to found an establishment, be completely mad; but be sure that your madness corresponds with the turn and temper of your age.

We are astonished at thought, but sensation is equally wonderful.

Nature has always had more force than education.

Those who can be made to believe absurdities can be made to commit atrocities.