The merit of painting lies in the exactness of reproduction. Painting is a science and all sciences are based on mathematics. No human inquiry can be a science unless it pursues its path through mathematical exposition and demonstration.

We must doubt the certainty of everything which passes through the senses, but how much more ought we to doubt things contrary to the senses, such as the existence of God and the soul.

Old age takes in part savoury wisdom for its food - see to that your old age will not lack in nourishment.

Common Sense is that which judges the things given to it by other senses.

He who wishes to see how the soul inhabits the body should look to see how that body uses its daily surroundings. If the dwelling is dirty and neglected, the body will be kept by its soul in the same condition, dirty and neglected.

When you look at a wall spotted with stains...you may discover a resemblance to various landscapes, beautiful with mountains, rivers, rocks, trees. Or again, you may see battles and figures in action, or strange faces and costumes, and an endless variety of objects which you could reduce to complete and well-drawn figures.

Just as courage is the danger of life, so is fear its safeguard.