I consider that I understand an equation when I can predict the properties of its solutions, without actually solving it.

The fundamental laws necessary for the mathematical treatment of a large part of physics and the whole of chemistry are thus completely known, and the difficulty lies only in the fact that application of these laws leads to equations that are too complex to be solved.

There is in my opinion a great similarity between the problems provided by the mysterious behavior of the atom and those provided by the present economic paradoxes confronting the world.

A physical law must possess mathematical beauty.

I learnt to distrust all physical concepts as the basis for a theory. Instead one should put one's trust in a mathematical scheme, even if the scheme does not appear at first sight to be connected with physics. One should concentrate on getting interesting mathematics.

Scientific progress is measured in units of courage, not intelligence.

The methods of theoretical physics should be applicable to all those branches of thought in which the essential features are expressible with numbers.