Man selects only for his own good: Nature only for that of the being which she tends.

Natural selection, also, leads to divergence of character; for more living beings can be supported on the same area the more they diverge in structure, habits, and constitution.

Man in his arrogance thinks himself a great work.

In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation. Light will be thrown on the origin of man and his history.

I believe that animals have descended from at most only four or five progenitors, and plants from an equal or lesser number.

I believe man . . . in the same predicament with other animals.