[Kepler] had to realize clearly that logical-mathematical theoretizing, no matter how lucid, could not guarantee truth by itself; that the most beautiful logical theory means nothing in natural science without comparison with the exactest experience. Without this philosophic attitude, his work would not have been possible.

I do not believe that civilization will be wiped out in a war fought with the atomic bomb. Perhaps two-thirds of the people of the earth will be killed.

This is what the painter, the poet, the speculative philosopher, and the natural scientists do, each in his own fashion.

To have security against atomic bombs and against the other biological weapons, we have to prevent war, for if we cannot prevent war every nation will use every means that is at their disposal; and in spite of all promises they make, they will do it. At the same time, so long as war is not prevented, all the governments of the nations have to prepare for war, and if you have to prepare for war, then you are in a state where you cannot abolish war.

But love brings much happiness - much more so than pining brings pain.

One must take what nature gives as one finds it.

As far as the laws of mathematics refer to reality, they are not certain, and as far as they are certain, they do not refer to reality.