"I could show fight on natural selection having done and doing more for the progress of civilization than you seem inclined to admit."

"A scientific man ought to have no wishes, no affections – a mere heart of stone."

"The love for all living creatures is the most noble attribute of man."

"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."

"I have just finished my 'Origin,' and am now going to be a hermit for the rest of my life."