My reflection, when I first made myself master of the central idea of the 'Origin', was, 'How extremely stupid not to have thought of that!'

The improver of natural knowledge absolutely refuses to acknowledge authority, as such. For him, skepticism is the highest of duties; blind faith the one unpardonable sin.

I took thought, and invented what I conceived to be the appropriate title of 'agnostic'.

There is the greatest practical benefit in making a few failures early in life.

Do what you can to do what you ought, and leave hoping and fearing alone.

Follow humbly wherever and to whatever abyss Nature leads, or you shall learn nothing.

God give me strength to face a fact though it slay me.