As the area of light expands, so does the perimeter of darkness.

The individual must not merely wait and criticize, he must defend the cause the best he can. The fate of the world will be such as the world deserves.

As to science, we may well define it for our purpose as "methodical thinking directed toward finding regulative connections between our sensual experiences".

A theory is the more impressive the greater the simplicity of its premises is, the more different kinds of things it relates, and the more extended is its area of applicability. Therefore the deep impression which classical thermodynamics made upon me. It is the only physical theory of universal content concerning which I am convinced that within the framework of the applicability of its basic concepts, it will never be overthrown.

Honestly, I cannot understand what people mean when they talk about the freedom of the human will. I have a feeling, for instance, that I will something or other; but what relation this has with freedom I cannot understand at all. I feel that I will to light my pipe and I do it; but how can I connect this up with the idea of freedom? What is behind the act of willing to light the pipe ? Another act of willing?

You are the only person I know who has the same attitude towards physics as I have: belief in the comprehension of reality through something basically simple and unified... It seems hard to sneak a look at God's cards. But that He plays dice and uses 'telepathic' methods... is something that I cannot believe for a single moment.

What use are socks? They only produce holes.