I have just finished my sketch of my species theory. If as I believe that my theory is true & if it be accepted even by one competent judge, it will be a considerable step in science. I therefore write this, in case of my sudden death, as my most solemn & last request, which I am sure you will consider the same as if legally entered in my will, that you will devote 400£ to its publication & further will yourself, or through Hensleigh [Wedgwood], take trouble in promoting it.

...for the shield may be as important for victory, as the sword or spear.

Nothing is easier than to admit in words the truth of the universal struggle for life, or more difficult--at least I have found it so--than constantly to bear this conclusion in mind.

It is certain that there may be extraordinary mental activity with an extremely small absolute mass of nervous matter: thus the wonderfully diversified instincts, mental powers, and affections of ants are notorious, yet their cerebral ganglia are not so large as the quarter of a small pin's head. Under this point of view, the brain of an ant is one of the most marvelous atoms of matter in the world, perhaps more so than the brain of a man.

Only picture to yourself a nice soft wife on a sofa with good fire, & books & music.

I shall always feel respect for every one who has written a book, let it be what it may, for I had no idea of the trouble which trying to write common English could cost one—And alas there yet remains the worst part of all correcting the press.

This preservation of favourable variations and the destruction of injurious variations, I call Natural Selection, or the Survival of the Fittest. Variations neither useful nor injurious would not be affected by natural selection and would be left a fluctuating element.