"I have been a fool, but I have learned from my folly."

"I confess that I have often erred in my youth, but I have always corrected my errors."

"I was measuring the heavens, now I must measure the shadows of the Earth. Though my soul was from the heavens, the shadow of my body lies here."

"I much prefer the sharpest criticism of a single intelligent man to the thoughtless approval of the masses."

"Mathematics is the alphabet with which God has written the universe."