In my experience, the best creative work is never done when one is unhappy.

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.

You cannot prepare for war and peace at the same time.

Everything has changed, except our way of thinking.

I have not eaten enough of the tree of knowledge, though in my profession I am obligated to feed on it regularly.

You cannot simultaneously prevent and prepare for war.

I cannot then believe in this concept of an anthropomorphic God who has the powers of interfering with these natural laws. As I said before, the most beautiful and most profound religious emotion that we can experience is the sensation of the mystical. And this mysticality is the power of all true science.