John Stewart Bell

"It can be argued that in trying to see behind the formal predictions of quantum theory we are just making trouble for ourselves. Was not precisely this the lesson that had to be learned before quantum mechanics could be constructed, that it is futile to try to see behind the observed phenomena?"

"Bohr was inconsistent, unclear, willfully obscure and right. Einstein was consistent, clear, down-to-earth and wrong."

"The theorem tells you that maybe there must be something happening faster than light, although it pains me even to say that much. The theorem certainly implies that Einsteins concept of space and time, neatly divided up into separate regions by light velocity, is not tenable. But then, to say that theres something going faster than light is to say more than I know."

"1 + P(b, c) ≥ |P(a, b) － P(a, c)|"

"I agree with them about that: ORDINARY QUANTUM MECHANICS (as far as I know) IS JUST FINE FOR ALL PRACTICAL PURPOSES. Even when I begin by insisting on this myself, and in capital letters, it is likely to be insisted on repeatedly in the course of the discussion. So it is convenient to have an abbreviation for the last phrase: FOR ALL PRACTICAL PURPOSES = FAPP."

"Surely, after 62 years, we should have an exact formulation of some serious part of quantum mechanics? By exact I do not of course mean exactly true. I mean only that the theory should be fully formulated in mathematical terms, with nothing left to the discretion of the theoretical physicist . . . until workable approximations are needed in applications. By serious I mean that some substantial fragment of physics should be covered. Nonrelativistic particle quantum mechanics, perhaps with the inclusion of the electromagnetic field and a cut-off interaction, is serious enough."

"The first charge against measurement, in the fundamental axioms of quantum mechanics, is that it anchors there the shifty split of the world into system and apparatus. A second charge is that the word comes loaded with meaning from everyday life, meaning which is entirely inappropriate in the quantum context."

"The concepts system, apparatus, environment, immediately imply an artificial division of the world, and an intention to neglect, or take only schematic account of, the interaction across the split. The notions of microscopic and macroscopic defy precise definition. So also do the notions of reversible and irreversible."

"Einstein said that it is theory which decides what is . I think he was right—observation is a complicated and theory-laden business. Then that notion should not appear in the formulation of fundamental theory. Information? Whose information? Information about what? On this list of bad words from good books, the worst of all is measurement. It must have a section to itself."

"The idea that elimination of coherence, in one way or another, implies the replacement of and by or, is a very common one among solvers of the measurement problem. It has always puzzled me."

"The orthodox approaches, whether the authors think they have made derivations or assumptions, are just fine FAPP — when used with the good taste and discretion picked up from exposure to good examples."

"The concept of measurement becomes so fuzzy on reflection that it is quite surprising to have it appearing in physical theory at the most fundamental level... does not any analysis of measurement require concepts more fundamental than measurement? And should not the fundamental theory be about these more fundamental concepts?"