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Are QM interpretations physics or philosophy?

I asked a question on physics.stackexchange, and was told they were philosophy. Does anyone disagree?

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    I can see why they would fall under the philosophy heading, but then so would most of string theory, yet those physicists would have been happy to answer those questions. – Alexander S King Apr 18 '16 at 17:06
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    I don't see how string theory is the same. It is a mathematical reformulation of a theory. Quantum interpretations are about 'making sense' in a completely different way than finding a new model that makes exactly the same predictions. – user9166 Apr 18 '16 at 17:53
  • It depends on what sort of question it was. An interpretation could have some philosophical definition questions or possiblities but also interpretations which are more based on dry facts. But the border stays indeed a bit arbitrair. – Marijn Apr 18 '16 at 18:14
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    N.b. the responser on Physics SE may have intended a colloquial interpretation of the term "philosophy". – Dave Apr 18 '16 at 20:12
  • well then, pseudo philosophy? – user6917 Apr 18 '16 at 20:38
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Of course also philosophers are interested in the interpretation of quantum mechanics. But in general, there task is to collect and to survey the interpretations developed by physicists. E.g., see the book by the philosopher of science Esfeld, Michael: La philosophie des sciences. Une introduction (2009)

Well known interpretations of QM have been developed by working physicists like Bohr, Heisenberg, Everett or Rovelli. I do not know about a non-physicist who developed a new and important interpretation of QM - even Hans Reichenbach is no counter example. All of them considered their interpretation part of their work in physics.

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  • again could use a reference for "all of them considered their interpretation part of their work in physics", it being the meat of what you say – user6917 Apr 18 '16 at 22:08
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    @MATHEMETICIAN I confess I did not scan the papers of the physicists I named. But I assume the best reference would be simply to classify the journals where they regularly published. In addition one can check their own CV. – Jo Wehler Apr 18 '16 at 22:21
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As long as a (specific) QM interpretation still contains physical misunderstandings, it should stay firmly in the realm of physics. So if David Deutsch would claim that the many world interpretation is the only possible interpretation of QM, and that a quantum computer proves his point, because it gets its strength by computing in all those many worlds simultaneously, then it is the job of other physicists to point out that he is perpetuating physical misunderstandings. Or if Gerard't Hooft would claim that Feynmann diagrams represent pathes of virtual particles, then physicists must decide whether this can be a valid interpretation at all from a physical point of view. And if Dieter Zeh would claim that the density matrix is just an auxiliary mathematical construction which should under no circumstances be used a part of an interpretation of QM, then this is again a question which can be answered by physicists without the help of a philosopher.

On the other hand, what about discussing whether the currently used pragmatic interpretation of QM still has anything to do with Niels Bohr's interpretation of QM, or whether those interpretation disagree with the Copenhagen interpretation? Since neither the methods used to investagate such question, nor the answers themselves are of any interest to physics, one could say that they belong to philosophy (or maybe sociology).


Also many technical details of the many world interpretation require physical answers (not philosophy). For example, Everett gave a justification of the Born rule in the context of the relative state formulation of quantum mechanics, which was later extended by Gleason and related to a mathematical theorem. To me as an outside observer, this sounds like: "If there is a probability measure on the many worlds, then it must follow Born's rule". It is the job of the physicists to work out those details and their conclusions. Another technical question would be which interpretations of quantum mechanics require a quantized version of general relativity, and which ones are compatible with an unmodified theory of general relativity.

A question better suited for philosophy would be whether the many worlds of an interpretation must really exists, or whether their potential existence is enough. A fictional realism were they all exist might be the most convenient setting for doing actual physics, and an untrained investigator might be led into believing that one must accept their existence. But philosophers are well trained to know that very few things must really exist, and are more likely to spot the holes through which one can wiggle out of such a definite conclusion.

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