"Reasoning is a retrospective business—the judging of a present situation in the light of past experience."

“It is never entirely safe to laugh at the metaphysics of the 'man-in-the-street'. Basic ideas which have become enshrined in popular language cannot be wholly foolish or unwarranted. For that sort of canonization must mean, at least, that the notions in question have stood the test of numerous centuries and have been accorded unhesitating acceptance wherever speech has made its way.”

“Now, when we say of any occurrence that it is 'physical', we mean thereby that it is potentially describable in physical terms. So it is perfectly correct, to state that, in every happening with which our sensory nerves are associated, we find, after we have abstracted therefrom every known or imaginable physical component, certain categorically nonphysical residua.”

“We must live before we can attain to either intelligence or control at all. We must sleep if we are not to find ourselves, at death, helplessly strange to the new conditions. And we must die before we can hope to advance to a broader understanding.”

“We have now arrived within introductory range of that very meek-spirited creature known to modern science as the "Observer". It is a permanent obstacle in the path of our search for external reality that we can never entirely get rid of this individual. Picture the universe how we may, the picture remains of our making.”

“But the facts are unquestioned. The aeroplane does do these things, and if the theory does not give warranty for the practice, then it is the theory which is wrong.”