[Ernest Rutherford is]...a second Newton.

How do I work? I grope.

Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.

Knowledge is dead; the school, however, serves the living.

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.

We must be prepared to make the same heroic sacrifices for the cause of peace that we make ungrudgingly for the cause of war.

I never think of the future. It comes soon enough. When visiting the U.S. from Germany for a winter academic stay.