"The difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind."

"Ignorance more frequently begets confidence than does knowledge."

"If I had my life to live over again, I would have made a rule to read some poetry and listen to some music at least once every week."

"I am not apt to follow blindly the lead of other men."

"I feel most deeply that the whole subject is too profound for the human intellect. A dog might as well speculate on the mind of Newton."