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.

[Herschel and Humboldt] stirred up in me a burning zeal to add even the most humble contribution to the noble structure of Natural Science. No one or a dozen other books influenced me nearly so much as these two. I copied out from Humboldt long passages about Teneriffe and read them aloud on one of [my walking excursions].

It is a fatal fault to reason whilst observing, though so necessary beforehand and so useful afterwards.

I have watched how steadily the general feeling, as shown at elections, has been rising against Slavery. What a proud thing for England if she is the first European nation which utterly abolishes it! I was told before leaving England that after living in slave countries all my opinions would be altered; the only alteration I am aware of is forming a much higher estimate of the negro character.

You ask about my opinion on vivisection. I quite agree that it is justifiable for real investigations on physiology; but not for mere damnable and detestable curiosity.

My books have sold largely in England, have been translated into many languages, and passed through several editions in foreign countries. I have heard it said that the success of a work abroad is the best test of its enduring value. I doubt whether this is at all trustworthy; but judged by this standard my name ought to last for a few years.

From my early youth I have had the strongest desire to understand or explain whatever I observed. ... To group all facts under some general laws.