It strikes me that all our knowledge about the structure of our Earth is very much like what an old hen would know of the hundred-acre field in a corner of which she is scratching.

Nothing is easier than to admit in words the truth of the universal struggle for life, or more difficult--at least I have found it so--than constantly to bear this conclusion in mind.

Intelligence is based on how efficient a species became at doing the things they need to survive.

It is not the most intellectual of the species that survives; it is not the strongest that survives; but the species that survives is the one that is able best to adapt and adjust to the changing environment in which it finds itself.

In my most extreme fluctuations I have never been an atheist in the sense of denying the existence of a God ... I think that generally (& more and more so as I grow older) but not always, that an agnostic would be the most correct description of my state of mind.

...for the shield may be as important for victory, as the sword or spear.

But when on shore, & wandering in the sublime forests, surrounded by views more gorgeous than even Claude ever imagined, I enjoy a delight which none but those who have experienced it can understand.