"What goes up must come down."

"I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier sh…"

"The best way to understand is by examples."

"No great discovery was ever made without a bold guess."

"The way to chastity is not to struggle directly with incontinent thoughts but to avert the thoughts by some employment, or by reading, or by meditating on other things."