“Philosophy, as I shall understand the word, is something intermediate between theology and science.”

“Science is what you know, philosophy is what you don't know”

“The search for something permanent is one of the deepest of the instincts leading men to philosophy.”

“Understanding human nature must be the basis of any real improvement in human life. Science has done wonders in mastering the laws of the physical world, but our own nature is much less understood, as yet, than the nature of stars and electrons. When science learns to understand human nature, it will be able to bring a happiness into our lives which machines and the physical sciences have failed to create.”

“I have been accused of a habit of changing my opinions. I am not myself in any degree ashamed of having changed my opinions. What physicist who was already active in 1900 would dream of boasting that his opinions had not changed during the last half century? In science men change their opinions when new knowledge becomes available; but philosophy in the minds of many is assimilated rather to theology than to science. The kind of philosophy that I value and have endeavoured to pursue is scientific, in the sense that there is some definite knowledge to be obtained and that new discoveries can make the admission of former error inevitable to any candid mind. For what I have said, whether early or late, I do not claim the kind of truth which theologians claim for their creeds. I claim only, at best, that the opinion expressed was a sensible one to hold at the time when it was expressed. I should be much surprised if subsequent research did not show that it needed to be modified. I hope, therefore, that whoever uses this dictionary will not suppose the remarks which it quotes to be intended as pontifical pronouncements, but only as the best I could do at the time towards the promotion of clear and accurate thinking. Clarity, above all, has been my aim.”

“Philosophy, for Plato, is a kind of vision, the 'vision of truth' ... Everyone who has done any kind of creative work has experienced, in a greater or less degree, the state of mind in which, after long labour, truth or beauty appears, or seems to appear, in a sudden glory – it may only be about some small matter, or it may be about the universe ... I think most of the best creative work, in art, in science, in literature, and in philosophy, has been the result of such a moment.”

“A good social system is not to be secured by making people unselfish, but, by making their own vital impulses fit in with other peoples. This is feasible. Those who have produced stoic philosophies have all had enough to eat and drink.I feel I shall find the truth on my deathbed and be surrounded by people too stupid to understand—fussing about medicines instead of searching for wisdom.I hate being all tidy like a book in a library where nobody reads – prison is horribly like that.”