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!'

Science is nothing, but trained and organized common sense.

In matters of the intellect, do not pretend that conclusions are certain which are not demonstrated or demonstrable. That I take to be the agnostic faith, which if a man keep whole and undefiled, he shall not be ashamed to look the universe in the face, whatever the future may have in store for him.

Agnosticism, in fact, is not a creed, but a method, the essence of which lies in the rigorous application of a single principle. ... Positively the principle may be expressed: In matters of the intellect, follow your reason as far as it will take you, without regard to any other consideration. And negatively: In matters of the intellect, do not pretend that conclusions are certain which are not demonstrated or demonstrable.

My business is to teach my aspirations to confirm themselves to fact, not to try and make facts harmonize with my aspirations.

If every man possessed everything he wanted, and no one had the power to interfere with such possession; or if no man desired thatwhich could damage his fellow-man, justice would have no part to play in the universe.

Of moral purpose I see no trace in Nature. That is an article of exclusively human manufacture and very much to our credit.