The celebrated painter Gainsborough got as much pleasure from seeing violins as from hearing them.

Why does a suppurating lung give so little warning and a sore on the finger so much?

The pleasures of the imagination are as it were only drawings and models which are played with by poor people who cannot afford the real thing.

Brevity: To say at once whatever is to be said.

Doubt everything at least once, even the sentence "Two times two is four."

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 often takes more courage to change one's opinion than to stick to it.