To try to be happy is to try to build a machine with no other specification than that it shall run noiselessly.

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'.

Pragmatism is an intellectually safe but ultimately sterile philosophy.

It is a profound and necessary truth that the deep things in science are not found because they are useful; they are found because it was possible to find them.

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

Optimists think that this is the best of all possible worlds; pessimists fear they are right.

Discovery follows discovery, each both raising and answering questions, each ending a long search, and each providing the new instruments for a new search.