Charles Darwin

"Such are the imperfections of our knowledge and such the uncertainty of all conjecture on this subject."

"I have throughout life been haunted by the feeling that I was playing a game without knowing the rules."

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

"To kill an error is as good a service as, and sometimes even better than, the establishing of a new truth or fact."

"It is impossible to conceive this immense and wonderful universe, as the result of blind chance or necessity."

"On the other hand, if we do not permit scientific truths to be questioned, we betray the very spirit of science."

"I'm an old man now, and perhaps have become more cautious and less inclined to new views."

"There seems to be some principle of improvement in all organic beings."

"The sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick."

"I would as soon be descended from an ape as from a clergyman."

"To suppose that the eye, with all its inimitable contrivances, could have been formed by natural selection, seems absurd."

"Extinction has only separated groups; it has by no means made them; for if every form which has ever lived on this earth were suddenly to reappear, not a single additional link would thereby be supplied."

"A moral being is one who is capable of reflecting on his past actions and on their motives, of approving of some and disapproving of others."

"The descent of man may be traced in the development of his moral sense."

"I have steadily endeavored to keep my mind free, so as to give up any hypothesis, however much beloved."

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

"It seems to me that nothing can be more improved than the moral sense of man."

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

"The fact that man can and does lose his reason, is no argument against the sacred nature of his intellect."

"Those who experience much, feel deeply."

"I have tried lately very hard to believe in the immortality of the soul."

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

"It is hardly an exaggeration to say that natural selection works solely by and for the good of each being."

"Great is the power of steady misrepresentation."

"I may safely affirm that not one of my critics can have read more carefully what I have written."

"The very lowest form of life is the monad."

"I have deeply regretted that I did not proceed far enough at least to understand the great leading principles of geology."

"One general law, leading to the advancement of all organic beings, namely, multiply, vary, let the strongest live and the weakest die."

"Almost every one who has written on the subject of animals, has noticed that they have great pleasure in play."

"The most important of my conclusions may be summed up as follows."