To write brashly about some things, it is almost necessary not to know much about them.

One might call habit a moral friction: something that prevents the mind from gliding over things but connects it with them and makes it hard for it to free itself from them.

One of our forefathers must have read a forbidden book.

Man is a masterpiece of creation, if only because no amount of determinism can prevent him from believing that he acts as a free being.

It thunders, howls, roars, hisses, whistles, blusters, hums, growls, rumbles, squeaks, groans, sings, crackles, cracks, rattles, flickers, clicks, snarls, tumbles, whimpers, whines, rustles, murmurs, crashes, clucks, to gurgle, tinkles, blows, snores, claps, to lisp, to cough, it boils, to scream, to weep, to sob, to croak, to stutter, to lisp, to coo, to breathe, to clash, to bleat, to neigh, to grumble, to scrape, to bubble. These words, and others like them, which express sounds are more than mere symbols: they are a kind of hieroglyphics for the ear.

If there were only turnips and potatoes in the world, someone would complain that plants grow the wrong way.

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.