The doctrine of the Kingdom of Heaven, which was the main teaching of Jesus, is certainly one of the most revolutionary doctrines that ever stirred and changed human thought.

My days I devote to reading and experiments in chemistry, and I spend many of the clear nights in the study of astronomy. There is, though I do not know how there is or why there is, a sense of infinite peace and protection in the glittering hosts of heaven. There it must be, I think, in the vast and eternal laws of matter, and not in the daily cares and sins and troubles of men, that whatever is more than animal within us must find its solace and its hope.

Human history in essence is the history of ideas.

Nature never appeals to intelligence until habit and instinct are useless. There is no intelligence where there is no need of change.

Adapt or perish, now as ever, is nature's inexorable imperative.

What a huge inaccessible lumber-room of thought and experience we amounted to, I thought; how much we are, how little we transmit.