"It is not enough to possess a good mind; one must make good use of it."

"I desire to live in such a way that I can spend the rest of my life without having committed any fault."

"I am accustomed to sleep, and in my dreams to imagine the same things that lunatics do when awake."

"I consider that I possess no senses; I imagine that body, figure, extension, motion and place are but fictions of my mind."

"To be possessed of a vigorous mind is not enough; the prime requisite is rightly to apply it."