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.

It is easier to contend with evil at the first than at the last.

Inequality is the cause of all local movements.

Poor is the pupil who does not surpass his master.

Just as iron rusts from disuse, and stagnant water putrefies, or when cold turns to ice, so our intellect wastes unless it is kept in use.

The eye is the window of the human body through which it feels its way and enjoys the beauty of the world.

There is no higher or lower knowledge, but one only, flowing out of experimentation.