Test knowledge through experience, be prepared to make mistakes, and be persistent about it.

The good painter must paint two things: a person and the essence of his soul.

First study the science, and then practice the art which is born of that science.

Never make heads straight on the shoulders, but turn them aside to the right or to the left, even though they look down, or upward, or straight ahead, because it is necessary for them to look lively and awake and not asleep. And do not depict the front or rear half of the whole person so that too much straightness is displaced, one half above or below the other half; and if you should wish to use stiff figures, do so only in portraying old people.

When counting, try not to mix chickens with blessings.

The men of experiment are like the ant; they only collect and use. But the bee...gathers its materials from the flowers of the garden and of the field, but transforms and digests it by a power of its own.

King of the animals — as thou hast described him — I should rather say king of the beasts, thou being the greatest — because thou hast spared slaying them, in order that they may give thee their children for the benefit of the gullet, of which thou hast attempted to make a sepulchre for all animals; and I would say still more, if it were allowed me to speak the entire truth.