A grand and almost untrodden field of inquiry will be opened, on the causes and laws of variation, on correlation of growth, on the effects of use and disuse, on the direct actions of external conditions, and so forth.

The following proposition seems to me in a high degree probable—namely, that any animal whatever, endowed with well-marked social instincts, the parental and filial affections being here included, would inevitably acquire a moral sense or conscience, as soon as its intellectual powers had become as well, or nearly as well developed, as in man. For, firstly, the social instincts lead an animal to take pleasure in the society of its fellows, to feel a certain amount of sympathy with them, and to perform various services for them.

Our descent, then, is the origin of our evil passions!! The devil under form of Baboon is our grandfather.

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.

Thus disbelief crept over me at a very slow rate, but at last was complete. The rate was so slow that I felt no distress, and have never since doubted even for a single second that my conclusion was correct.

Natural selection acts solely by accumulating slight successive favorable variations, it can produce no great or sudden modification; it can act only by very short steps.

Worms have played a more important part in the history of the world than humans would at first suppose.