A man who has no assured and ever present belief in the existence of a personal God or of a future existence with retribution and reward, can have for his rule of life, as far as I can see, only to follow those impulses and instincts which are the strongest or which seem to him the best ones

Animals manifestly enjoy excitement, and suffer from annul and may exhibit curiosity.

Nevertheless so profound is our ignorance, and so high our presumption, that we marvel when we hear of the extinction of an organic being; and as we do not see the cause, we invoke cataclysms to desolate the world, or invent laws on the duration of the forms of life!

Disbelief crept over me at a very slow rate, but at last it was complete.

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

As for a future life, every man must judge for himself between conflicting vague probabilities.

The main conclusion here arrived at ... is that man is descended from some less highly organized form.