The thoughts written on the walls of madhouses by their inmates might be worth publicizing.

To be content with life or to live merrily, rather all that is required is that we bestow on all things only a fleeting, superficial glance; the more thoughtful we become the more earnest we grow.

A good method of discovery is to imagine certain members of a system removed and then see how what is left would behave: for example, where would we be if iron were absent from the world: this is an old example.

It is said that truth comes from the mouths of fools and children: I wish every good mind which feels an inclination for satire would reflect that the finest satirist always has something of both in him.

We often have need of a profound philosophy to restore to our feelings their original state of innocence, to find our way out of the rubble of things alien to us, to begin to feel for ourselves and to speak ourselves, and I might almost say to exist ourselves.

I ceased in the year 1764 to believe that one can convince one’s opponents with arguments printed in books. It is not to do that, therefore, that I have taken up my pen, but merely so as to annoy them, and to bestow strength and courage on those on our own side, and to make it known to the others that they have not convinced us.

Everyone is perfectly willing to learn from unpleasant experience - if only the damage of the first lesson could be repaired.