Reasoning is a retrospective business—the judging of a present…

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 …

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 …

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.

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 …

The ability to imagine relations is one of the most indispensable conditions of all precise thinking. No subject can be named, in the investigation of which it is not imperatively needed; but it can nowhere else be so thoroughly acquired …

In science the credit goes to the man who convinces the world, not to the man to whom the idea first occurs. Not the man who finds a grain of new and precious quality but to him who sows it, reaps it, grinds it and feeds the world on it.