Progress has been much more general than retrogression

The lower animals, like man, manifestly feel pleasure and pain, happiness and misery. Happiness is never better exhibited than by young animals, such as puppies, kittens, lambs, &c., when playing together, like our own children.

The fact of evolution is the backbone of biology, and biology is thus in the peculiar position of being a science founded on an improved theory, is it then a science or faith?

Even the humblest mammal's strong sexual, parental, and social instincts give rise to 'do unto others as yourself' and 'love thy neighbor as thyself'.

Building a better mousetrap merely results in smarter mice.

Much love much trial, but what an utter desert is life without love.

I fully agree with all that you say on the advantages of Spencer's excellent expression of 'the survival of the fittest.' This, however, had not occurred to me till reading your letter. It is, however, a great objection to this term that it cannot be used as a substantive governing a verb; and that this is a real objection I infer from H. Spencer continually using the words, natural selection.