Just as iron rusts from disuse... even so does inaction spoil the intellect.

To be a winner you must want to win but must know of the chance of losing and must not fear of it.

Demetrius was wont to say that there was no difference between the words and speech of the unskilled and ignorant and the sounds and rumblings caused by the stomach being full of superfluous wind. This he said, not without reason, for, as he held, it did not in the least matter from what part of them the voice emanated, whether from the lower parts or the mouth, since the one and the other were of equal worth and importance.

If a man has a tent made of linen of which the apertures have all been stopped up, and be it twelve bracchia across (over twenty-five feet) and twelve in depth, he will be able to throw himself down from any height without sustaining injury. [His concept of the parachute.]

Everything comes from everything, and everything is made out of everything, and everything returns into everything.

How painting surpasses all human works by reason of the subtle possibilities which it contains.

Wherever good fortune enters, envy lays siege to the place and attacks it; and when it departs, sorrow and repentance remain behind.