The world will not be inherited by the strongest, it will be inherited by those most able to change.

On your life, underestimating the proclivities of finches is likely to lead to great internal hemorrhaging.

There is no fundamental difference between man and the higher mammals in their mental faculties...The difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind.

When I view all beings not as special creations, but as the lineal descendants of some few beings which lived long before the first bed of the Cambrian system was deposited, they seem to me to become ennobled.

I am not apt to follow blindly the lead of other men

...I feel most deeply that the whole subject is too profound for the human intellect. A dog might as well speculate on the mind of Newton.— Let each man hope & believe what he can.—

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