Of the original phenomena, light is the most enthralling.

While I thought that I was learning how to live, I have been learning how to die.

No human investigation can claim to be scientific if it doesn't pass the test of mathematical proof.

Beyond a doubt truth bears the same relation to falsehood as light to darkness.

Perspective is a most subtle discovery in mathematical studies, for by means of lines it causes to appear distant that which is near, and large that which is small.

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

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.