In the world of letters, learning and knowledge are one, and books are the source of both; whereas in science, as in life, learning and knowledge are distinct, and the study of things, and not of books, is the source of the latter.

Oh devil! truth is better than much profit. I have searched over the grounds of my belief, and if wife and child and name and fame were all to be lost to me one after the other as the penalty, still I will not lie.

The best men of the best epochs are simply those who make the fewest blunders and commit the fewest sins.

That which endures is not one or another association of living forms, but the process of which the cosmos is the product, and of which these are among the transitory expressions.

God give me strength to face a fact though it slay me.

For these two years I have been gravitating towards your doctrines, and since the publication of your primula paper with accelerated velocity. By about this time next year I expect to have shot past you, and to find you pitching into me for being more Darwinian than yourself. However, you have set me going, and must just take the consequences, for I warn you I will stop at no point so long as clear reasoning will take me further.

The quarrels of theologians and philosophers have not been about religion, but about philosophy; and philosophers not unfrequently seem to entertain the same feeling toward theologians that sportsmen cherish toward poachers.