The dead are invisible, but they are not absent.

The greatest inventions are those which most directly meet the wants of mankind.

"La historia no se repite, pero rima."

The person who tries to live alone will not succeed as a human being. His heart withers if it does not answer another heart. His mind shrinks away if he hears only the echoes of his own thoughts and finds no other inspiration.

In mathematics, you don't understand things. You just get used to them.