“To pry into the secrets of this world, we must make experiments. But experiment is a clumsy instrument, afflicted with a fatal determinacy which destroys causality.”

But we must not underestimate the potency of the mathematical process of abstraction.

No longer was light analogous to the discharge of a blunderbuss, but rather to the pulsating flight of birds.

Every new discovery in science brings with it a host of new problems, just as the invention of the automobile brought with it gas stations, roads, garages, mechanics, and a thousand other subsidiary details.

A surprising variety of things happen to have both magnitude and direction and to combine according to the parallelogram law; and many of them are not at all reminiscent of journeys.