I am a firm believer, that without speculation there is no good and original observation.

There is no fundamental difference between humans and the higher mammalsin their mental faculties

I suppose you are two fathoms deep in mathematics, and if you are, then God help you. For so am I, only with this difference: I stick fast in the mud at the bottom, and there I shall remain.

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...We behold the face of nature bright with gladness...We do not see, or we forget, that the birds which are idly singing round us mostly live on insects and seeds, and are thus constantly destroying life.

It is not the most intellectual of the species that survives; it is not the strongest that survives; but the species that survives is the one that is able best to adapt and adjust to the changing environment in which it finds itself.

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

The tree of life should perhaps be called the coral of life, base of branches dead; so that passages cannot be seen-this again offers contradiction to constant succession of germs in progress.