A mathematician is a blind man in a dark room looking for a black cat which isn't there.

After my return to England it appeared to me that by following the example of Lyell in Geology, and by collecting all facts which bore in any way on the variation of animals and plants under domestication and nature, some light might perhaps be thrown on the whole subject.

Often a cold shudder has run through me, and I have asked myself whether I may have not devoted myself to a fantasy.

I see no good reasons why the views given in this volume should shock the religious views of anyone.

I have deeply regretted that I did not proceed far enough at least to understand something of the great leading principles of mathematics, for men thus endowed seem to have an extra sense.

Your words have come true with a vengeance that I shd [should] be forestalled ... I never saw a more striking coincidence. If Wallace had my M.S. sketch written out in 1842 he could not have made a better short abstract! Even his terms now stand as Heads of my Chapters.

Language is an art, like brewing or baking.... It certainly is not a true instinct, for every language has to be learnt.