"My mind seems to have become a kind of machine for grinding general laws out of large collections of facts."

"I am almost convinced that species are not (it is like confessing a murder) immutable."

"We are like a judge who has to sum up and deliver judgment, not on the evidence of witnesses, but on the arguments of counsel."

"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."

"The very essence of instinct is that it's followed independently of reason."