God does not care about our mathematical difficulties. He integrates empirically.

Physics is an attempt conceptually to grasp reality as something that is considered to be independent of its being observed. In this sense one speaks of physical reality.

A theory can be proved by experiment; but no path leads from experiment to the birth of a theory.

The American lives even more for his goals, for the future, than the European. Life for him is always becoming, never being.

[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.

[When asked "Dr. Einstein, why is it that when the mind of man has stretched so far as to discover the structure of the atom we have been unable to devise the political means to keep the atom from destroying us?"] That is simple, my friend. It is because politics is more difficult than physics.

Our defense is not in our armaments, nor in science, nor in going underground. Our defense is in law and order.