"The greatest happiness is to know the source of unhappiness."

"Man is a creature that can get accustomed to anything, and I think that is the best definition of him."

"Pain and suffering are always inevitable for a large intelligence and a deep heart. The really great men of action, for example, must, I believe, have great sadness on earth."

"It is not the brains that matter most, but that which guides them—the character, the heart, generous qualities, progressive ideas."

"Talking nonsense is the sole privilege mankind possesses over the other organisms. It's by talking nonsense that people reach the truth."