How many emperors and how many princes have lived and died and no record of them remains, and they only sought to gain dominions and riches in order that their fame might be ever-lasting.

O sleepers! what a thing is slumber! Sleep resembles death. Ah, why then dost thou not work in such wise as that after death thou mayst retain a resemblance to perfect life, when, during life, thou art in sleep so like to the hapless dead?

Learning never exhausts the mind.

He who cannot establish dominion over himself will have no dominion over others.

The painter who draws merely by practice and by eye, without any reason, is like a mirror which copies every thing placed in front of it without being conscious of their existence.

Iron rusts from disuse; water loses its purity from stagnation... even so does inaction sap the vigor of the mind.

But to me all sciences seem vain and full of error that are not born of experience, mother of all certainty, and do not terminate in an actual experience.