Make your faces so that they do not all have the same expression, as one sees with most painters, but give them different expression, according to age, complexion, and good or bad character.

Given the cause nature produces the effect in the briefest manner that it can employ.

Those who are in love with practice without knowledge are like the sailor who gets into a ship without rudder or compass and who never can be certain whether he is going. Practice must always be founded on sound theory, and to this Perspective is the guide and the gateway; and without this nothing can be done well in the matter of drawing.

Obstacles cannot crush me. Every obstacle yields to stern resolve. He who is fixed to a star does not change his mind.

The human being, creature of eyes, needs the image.

The light and heat of the universe comes from the sun, and its cold and darkness from the withdrawal of the sun.

It's easier to resist at the beginning than at the end.