He who fears dangers will not perish by them.

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

The eye which turns from a white object in the light of the sun and goes into a less fully lighted place will see everything as dark.

Just as eating against one's will is injurious to health, so studying without a liking for it spoils the memory, and it retains nothing it takes in.

He who does not understand the supreme certainty of mathematics is wallowing in confusion.

The truth of things is the chief nutriment of superior intellects.

Why does the eye see a thing more clearly in dreams than the imagination when awake?