A problem cannot be solved at the level of consciousness in which it occurs.

Conventional words or other signs have to be sought for laboriously only in a second stage, where the associative play already referred to is sufficiently established and can be reproduced at will.

The relativity principle in connection with the basic Maxwellian equations demands that the mass should be a direct measure of the energy contained in a body; light transfers mass. With radium there should be a noticeable diminution of mass. The idea is amusing and enticing; but whether the Almighty is laughing at it and is leading me up the garden path -- that I cannot know.

If we knew what it was we were doing, it would not be called research, would it?

The consequence was a positively fanatic [orgy of] freethinking coupled with the impression that youth is being deceived by the state through lies; it was a crushing impression

In the shadow of the atomic bomb it has become even more apparent that all men are, indeed, brothers.

I do not believe in the God of theology who rewards good and punishes evil. My God created laws that take care of that. His universe is not ruled by wishful thinking, but by immutable laws.