Never do anything against conscience even if the state demands it.

Whether or not you can observe a thing depends upon the theory you use. It is the theory which decides what can be observed.

One can only continue to expect to be read if one omits everything that is unimportant.

I don't teach my students, I provide the circumstances in which they can learn.

When a man points a finger at someone else, he should remember that three of his fingers are pointing at himself. Do not worry about your difficulties in mathematics; I can assure you that mine are still greater.

All these constructions and the laws connecting them can be arrived at by the principle of looking for the mathematically simplest concepts and the link between them.

Live with purpose. Don't let people or things around you get you down.