The optimist thinks this is the best of all possible worlds. The pessimist fears it is true.

Things which stimulate my curiosity are pretty far removed from the practical and therefore from classification.

Science is not everything, but science is very beautiful.

There must be no barriers for freedom of inquiry... There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors.

If we ask, for instance, whether the position of the electron remains the same, we must say 'no'; if we ask whether the electron's position changes with time, we must say 'no'; if we ask whether the electron is at rest, we must say 'no'; if we ask whether it is in motion, we must say 'no'.

Both the man of science and the man of action live always at the edge of mystery, surrounded by it.

In the material sciences these are and have been, and are most surely likely to continue to be heroic days.