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After stumbling upon this recent survey from 2020, it is interesting to see that the most popular position (apart from being undecided) is hidden variables at 21.94%. As a reminder, a hidden-variable theory is “a deterministic physical model which seeks to explain the probabilistic nature of quantum mechanics by introducing additional (possibly inaccessible) variables”.

Note that the next most popular interpretation is many worlds. Thus, it seems that the most popular position is still pretty strongly deterministic even though the common conception elsewhere is that quantum mechanics puts a dent on determinism.

What I find interesting is that this is in direct contrast to what physicists believe where the most popular position was the Copenhagen intepretation although it was taken more than a decade ago

Are philosophers over analyzing and trying to armchair their way into a field that is for physicists?

Or have most physicists just have not thought that much about various interpretations and implications of theories unlike philosophers and are more focused on doing practical experiments?

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  • Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Philosophy Meta, or in Philosophy Chat. Comments continuing discussion may be removed.
    – Geoffrey Thomas
    Commented Apr 14 at 11:54
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    The premise of the question false. "The most popular position" is not at all the same thing as "most philosophers believe". The survey referenced shows more philosophers undecided than accepting hidden variables, and close to three times as many accepting specific positions different from hidden variables. 22% accepting hidden variables is nothing like "most", and that's before we even come to whether the difference between that and some of the other positions is statistically significant for the survey. But we probably can conclude from it that most philosophers reject hidden variables. Commented Apr 14 at 14:27
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    @Ronald, even the combination of respondents accepting hidden variables or many worlds or "a combination of views" (which may or may not be deterministic) is till less than 50%. That's not remotely "most". Commented Apr 14 at 17:14
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    "As a reminder, a hidden-variable theory is “a deterministic physical model which seeks to explain the probabilistic nature of quantum mechanics by introducing additional (possibly inaccessible) variables”" - according to whom? Also, if such variables turn out not to be accessible, then in pragmatic terms I would say that is inherently not deterministic. Commented Apr 14 at 17:16
  • When I hear "physical" and "deterministic"... I know what I think... physical things... determining things... I could find no existing theory or sugestion that was either. I had to come up with my own. ![Physical deterministic model](i.sstatic.net/OPmUP.jpg) Image source: Me When all others, physicists, philosophers, thinkers, engineers, cosmologists, etc. discuss about: - Physical - Deterministic I really don't know which of humanities theories they are referring to, because other than the physical deterministic model I came up with... I am Commented Apr 14 at 22:30

9 Answers 9

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Most philosophers don't understand Quantum Physics the way actual physicists who specialize in that type of physics do. Their preference for "hidden variables" is based on reasonable intuitions, but if they haven't intensely studied the actual physics, the actual math, the actual experiments, then their preference for Hidden Variables can probably be broken down into this:

Hidden Variables can be simply stated as the naive view of the world. I know there are more ideas under the "hidden variables" banner, but most people arguing for hidden variables are arguing this:

The Newtonian view of the world says that all matter has, at any given time, a specific location, and a specific vector of velocity in some direction, and whatever other property you want to state about that piece of matter.

If I throw a ball, and I look away, the ball is still flying in a particular way, and continues along it's path the same way as it would if I were looking. Basic realism, right? Even when I'm not looking, that ball has a position and momentum at any given moment in time. This is what most of "hidden variables" ideas intuit, and this is what Quantum Mechanics forces us to question, at least when it comes to quantum objects like electrons and photons and etc.

If you don't study quantum mechanics intensely enough, you don't actually learn the reason why most experts in quantum mechanics entirely reject local hidden variables. Can most of the philosophers who are answering this survey honestly say they've understood Bell's Theorem and what it means for the operation of our universe? I'm not sure they can.

I care what philosophers think for questions that philosophers should be experts on. I care what physicists think for questions that physicists should be experts on. Philosophers probably have a better-than-average understanding of QM, but not better than experts in QM.

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    @DikranMarsupial can you please point me to where I can read question 6? It's not obvious to me from the link in the OP how to see that.
    – TKoL
    Commented Apr 12 at 10:17
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    @Stella It isn't false. AIUI Bells inequality rules out locality of interactions with hidden variables, but that still leaves the loophole of non-local interactions with hidden variables. However that is a bit of a strain to accept, so I would be completely unsurprised if Bell's inequality was sufficient for >50% of the worlds quantum physicists to entirely reject hidden variables, even though Bell's inequality doesn't completely rule them out. Commented Apr 12 at 10:21
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    No, there is no “non deterministic” local theory. This is again a common misconception. Bell’s inequalities start from two assumptions for any theory that explains the correlations. A) Statistical independence. B) Locality. One of them has to go if there is a theory. See answer here that goes over this: physics.stackexchange.com/a/809782/399487Sadly, it was often claimed that one could get around Bell’s conclusion by simply allowing a theory with randomness, but fortunately those claims have subsided as of late Commented Apr 12 at 10:27
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    @Stella I've edited my post to say they reject local hidden variables. I was not paying enough attention to details.
    – TKoL
    Commented Apr 12 at 10:37
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    TKoL I agree with your assessment. Possibly one can add that philosophers in general have high esteem of Leibniz' principle of sufficient reason.
    – Jo Wehler
    Commented Apr 12 at 10:38
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Q14of the physics survey gives a pretty good answer to this question:

enter image description here

In the absence of evidence, beliefs/acceptance of competing interpretations is a matter of personal philosophical prejudice (or cognitive bias depending on how you view it). If you don't like the idea of not being able to know something or genuine randomness, then you are going to prefer deterministic interpretations. As the physics survey says, as we don't have empirical evidence to decide, it is down to personal philosophical prejudice.

It doesn't seem too surprising to me that physicists and philosophers have different cognitive biases or personal prejudices regarding these issues. From a scientific perspective you can live with "shut up and calculate" if there is no empirical or observational evidence that supports a particular interpretation of the calculation. Physicists tend to be much more focused on observable reality than philosophers, who may find the idea that there are things we can't know or understand completely unpalatable.

Also quantum physicists have studied quantum physics in more detail than philosophers, so it is unsurprising they may have different views - they have more information. There have also been studies of e.g. understanding of the science of climate change in climate scientists and in the general public. Believe it or not, there is a difference in the degree to which certain ideas are accepted or not based on expertise!

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Most physicists aren't interested in the interpretation controversy about quantum theory because of the common but false idea that different interpretations make the same predictions. This is a result of a misrepresentation of the interpretation controversy in most educational material about quantum theory.

There are equations that are taken for granted by physicists to make predictions using quantum theory. There is also a well known set of experiments whose results are predicted using quantum theory, e.g. - Bell correlations, single particle interference etc. There is a controversy over what is happening in reality to bring about the results of those experiments. There are three sets of accounts of what is happening.

(1) We don't care what's happening. We just want to make predictions. Trying to explain what's happening is heresy. Shut up. These theories, which include the Copenhagen and statistical interpretations, have problems with making any predictions because unless you have some idea of what's happening in reality during an experiment, there is no fact of the matter whether the experiment has been done correctly. This shut up policy also leads to a lack of attention to how predictions are made in most expository material:

https://arxiv.org/abs/1604.05973

There is a further problem which is that lack of any understanding of what quantum theory says about the world makes finding its replacement harder. For example, it is still common to see claims in the literature that quantum theory is non-local although that claim was refuted more than 20 years ago:

https://arxiv.org/abs/quant-ph/9906007

https://arxiv.org/abs/2304.14959

(2) Quantum theory's equations of motion are accurate as a description of reality and they imply the existence of a structure called the multiverse that looks a bit like a set of parallel universes in approximations that hold in everyday life: the many worlds interpretation (MWI).

(3) The multiverse is unacceptable for philosophical reasons and quantum theory must be replaced by another theory such the spontaneous collapse theory or pilot wave theory. These theories make different experimental predictions than quantum theory:

https://arxiv.org/abs/2310.14969

https://arxiv.org/abs/1906.10761

The philosophical objections say that the MWI can't explain probability or the basis in which the multiverse is divided into parallel universes:

https://arxiv.org/abs/0905.0624

David Wallace has argued that the MWI works about as well as any other physical theory so unless you want to ditch all of physics you should adopt it:

https://arxiv.org/abs/1111.2189

In addition, all of the alternatives in category 3 do not currently reproduce the vast bulk of the predictions of relativistic quantum field theories, i.e. - almost all of the predictions physicists actually make using quantum theory:

https://arxiv.org/abs/2205.00568

Both physicists and philosophers take more interest in understanding what quantum theory says about the world instead of trying to evade its implications.

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  • The link for problems with Everett is highly relevant. Everett has multiple philosophical problems, the most critical being it removes any coherent meaning to "causation", and it puts the observer (non-realism) back centrally in resolving measurements. Your links pointing out that pilot wave (non-local variables) and spontaneous collapse are DIFFERENT theories, not just "interpretations" is also highly relevant, as the measurements of QM vs. them are trending toward QM (Coopenhagen). As your link shows, Everett appears to be an "interpretation", but one that is not coherent.
    – Dcleve
    Commented Apr 14 at 17:27
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    The Everett interpretation (EI) treats measurements in terms of interactions that produce records, which isn't observer centric. The EI also explains causality in terms of the relevant equations of motion: event 1 causes event 2 if the evolution described by the equations of motion and initial conditions say so just like other physical theories. The Copenhagen interpretation has no explanation of measurement or causality or anything else because it amounts to the blank assertion that one should use the equations of motion but give no explanation of what they imply.
    – alanf
    Commented Apr 14 at 20:25
  • MWI cannot explain causality, because every possible event happens in its drastically over populated "reality". The only reason our "records" do not include all of these other events is because we are "we", not all. This is an explicitly observer-centric resolution of Bell's inequality, and an assertion that our universe is not reality.
    – Dcleve
    Commented Apr 14 at 20:38
  • MWI isn't accurately summarised as an "everything possible happens" theory arxiv.org/abs/1508.02048 The reason we don't see all of the events is a result of patterns of information flow that apply to all physical systems capable of holding records not just us arxiv.org/abs/0903.5082
    – alanf
    Commented Apr 15 at 8:20
  • Alanf -- I am 20 pages into Deutch's paper, and the issues I have with it are becoming unmanageable. First, he takes Popperian falsifiability to be true, despite Popper himself repudiating it based on Quine's argument. Second, he cites a refutation of "anything happens" that relies upon a probability analysis (page 13, he does not note the probability, but it is implicit) then later claims that he is not using probabilities at all. And since all experiments rely upon probabilities of our method and tools, his denial of this (and rejection of methodology in science) is simply wrong.
    – Dcleve
    Commented Apr 16 at 0:14
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Quantum mechanics does not put a "dent" on determinism. Quantum mechanics has nothing to do with determinism. Determinism is a practical tool in classical physics only. It is pretty much useless everywhere else.

Determinism is not a valid philosophical standpoint. It does not describe reality, does not claim or explain anything about reality. There is no wisdom in assuming the nonexistence of randomness and free will.

Imagining hidden variables is a desperate attempt to "save" determinism by "explaining" randomness. No-one has ever explained what makes the hidden variables vary. Do they vary randomly or is someone deliberately adjusting them?

There is a mysterious illogical craving for determinism among philosophers. Some of these people believe in the absence of beliefs, some imagine the absence of imagination, some consider the absence of possibilities a possibility, some have simply misunderstood the whole concept.

These people don't want to read facts about determinism. They are more likely to downvote this answer into oblivion for no reason at all.

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    I think the reason your answers get downvoted (although I do not) is because your answers contain the very same baseless and assertion driven biases that you claim others have. Commented Apr 12 at 11:14
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    I'd argue that randomness equally doesn't describe reality or claim or explain anything about reality. Most uses of randomness in the macroscopic world is a mathematical model that allows us to deal with uncertain knowledge or an absence of knowledge regarding a deterministic system. There is nothing random about rolling a dice if you have full knowledge of the forces applied and the initial conditions, it is completely deterministic (in the sense that the same initial conditions and forces will give the same results every time). Commented Apr 12 at 11:19
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    @Stella What are these "baseless assertion driven biases"? I do have a strong bias for common sense against irrational beliefs. Is that what you are referring to? Commented Apr 12 at 13:13
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    Calling determinism not a valid position or saying that people don’t believe in free will is only an assertion (even though some think it is incoherent) is nothing more than your assertions Commented Apr 12 at 14:03
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    @Stella Determinism is by definition just an idea of an imaginary system with certain conditions. Not my assertion. Free will is a real or an imaginary thing depending on the definition. Believing in free will means that there is no proper definition, the believer does not know what free will is. Commented Apr 12 at 16:37
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I can't speak for philosophers, but as a physicist with a PhD in QM I would make the following commments:

As noted by Armand, the Copenhagen Interpretation is almost a blank page ontologically. It gives a recipe for performing calculations, but doesn't shed any deliberate light on what is 'really' happening.

QM in practice is a lash-up of different mathematical techniques and approximations, which treats some particles as quantum entities while representing others as a source of classical potentials. Given that it is so obviously a model, the interpretations of it seem misguided. It's rather as if I used a perfect sphere as a model to figure out the volume of an orange, and people then developed competing speculative interpretations about the implications of oranges being perfectly round, missing the point that they aren't and that the roundness is an artefact of the model.

I know enough about QM to tell that a lot one reads about it outside physics journals is misleading or plain wrong. QM is fiercely complicated so the chance of a breakthrough in understanding coming from a non-specialist is remote. I do suppose that QM will be replaced by something better at some point.

As for many worlds, one problem is that there are so many different accounts of it, none of which has ever struck me as coherent.

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  • Upvoted, but I think that you're repeating some tropes and memes. In particular, how can a theory which coarse-grains to QM be ontic? Any fine-tuned regime of an epistemic theory is also epistemic; at best, we only know its ontic nature up to (possibly unique) isomorphism, as a consequence of having so tightly nailed down categorical axioms for Hilbert-space-like generalizations of probability.
    – Corbin
    Commented Apr 14 at 17:52
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    @Corbin cheers! If I am repeating tropes and memes it is a coincidence. I've arrived at my conclusions independently- I'm certainly not regurgitating what others have said (at least, not consciously!). Commented Apr 14 at 19:19
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There is no "deterministic formulation of quantum mechanics". The indeterminism is its defining characteristic. People who think the world is deterministic do not think quantum mechanics describes it properly. They would like to see a theory which amends or replaces it so that it becomes something different.

And yes, I mean this as dismissive as it sounds: It is the denial of reality as we know it. I don't mean that the current state of physics is "true" in an absolute sense of the word, or that there are no more significant revelations about nature in store. Far from it: My gut feeling is that such a belief is naive and, paradoxically, typically precedes revolutionary new revelations, as it did in the late 19th century. It's just that there is currently no sign whatsoever at all that the quantum theory with its inherent indeterminism is wrong in the sense that there are contradicting observations.

Deal with it.

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  • +1, but, I would suggest using the word un- or non- deterministic, than indeterministic. Commented Apr 14 at 17:49
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When 70% of the philosophers answering the question are determinists -- https://survey2020.philpeople.org/survey/results/4838, their preference for deterministic solutions to QM is at least consistent with their other worldview preferences.

Of the options presented for QM -- only hidden variables and many worlds are plausibly "deterministic", hence the preference for those two views among the philosophers surveyed.

MWI is often described as a deterministic theory, but it has significant issues that make it difficult to actually rate it as "deterministic". MWI does not deny the Heisenberg Uncertainty Principle, so the "state of the world" is intrinsically not knowable, ether for a starting condition, or an outcome, and both are generally assumed to be knowable in determinism vs. probabilistic/stochiometric views of the world.

Additionally, MWI cannot make any predictions -- its stoichiometry is introduced by the splitting of worlds at the time of an interaction (measurement) -- which gets around Bells Inequality by adopting non-realism ("which observer" is used to distinguish worlds, while realism as Bell defined it is observer independence).

In addition to the above two issues that make MWI both non-deterministic and non-realist, MWI also cannot allow a coherent view of causation, as pointed out in one of alanf's answers excellent links. In non-physics terms, per MWI, I could continue to complete this answer, abandon it to play video games instead for the day, or walk next door and kill the neighbor's annoyingly barking dog, and them as well, then drive off to get a drink. All of these worlds are among the MWI continuum branching from my prior paragraph, hence all are equally characterizable as "caused" by the prior state of the world at the end of my last paragraph, AND each of these produces an infinity of their own "caused" branches -- making "caused" conceptually invalid in MWI.

Enough philosophers seem to have understood these issues for MWI to have make hidden variables a barely more popular view, and at least one version of non-local hidden variables, Bohmian mechanics, has at least not yet been refuted by physics. But the trend line is negative for Bohmian Mechanics vs QM. https://settheory.net/Bohm

I agree with TKol's point that the philosophers surveyed probably do not understand the physics problems for their preferred views.

Note, for physicists actual views, this much larger and more recent survey https://arxiv.org/pdf/1612.00676.pdf gives significant differences from the one linked in the OP. Here is a summary of the results from that survey:

enter image description here

Note that, if one classifies MWI as non-deterministic, the only deterministic view among physicists that has measurable support is Bohm at 2%. All the other "solutions" have probabilistic processes explicit in their description. There is an effective consensus among physicists that quantum phenomena are non-deterministic -- held tentatively, as Bohm is not yet definitively refuted.

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What a provocative question…

It’s undeniable philosophers have contributed to quantum physics. Typically not by forcing their way in, but filling gaps which physicists have had ample time to try to fill.

Bohr was the most prolific proponent of quantum mechanics in the first half of the 20th century. His writings confused everyone. It’s why von Nuemann famously was wrong about his theorem hidden variables couldn’t explain QM.

John Bell is adored by philosophers for being the most clear headed writer on quantum mechanics post Bohr-era. He confirmed von Nuemann was incorrect and gave a positive example of a hidden variables theory. This finally upended Bohr’s reign in a sense.

Knowing physicists had been wrong many times, and that they were unwilling to give more than a “recipe” rather than an ontology, philosophers continued the work of the clear headed Bell, which finally gave them enough concrete writing to work from.

Physicists were still not as interested in the ontology as philosophers. Bell was a hidden variables proponent, and pilot wave theory had an ontology closer to what past ontologies looked like, e.g. a physical ontology in space and time, not something like saying “everything is the wave function” as the WF is much more abstract of an ontology.

Also keep in mind, physics and philosophy of physics overlap heavily at the highest levels, evidenced by David Albert.

Bell was not the first to disprove von Nuemann nor discovered a hidden variable theory of his own outright but old habits died hard, and he championed them and put pieces together with undeniably clear methods.

The first person to get Bell’s preprint was Abner Shimony according to Matt Leifer. He was a philosopher and physicist, teaching essentially the only classes on quantum foundations at the time. He instantly recognized the importance of it. Physicists needed until Bell to trust hidden variables were not ruled out even though multiple pieces proved they were possible 30-40 years earlier. This is really when important, lasting philosophy on QM interpretations began, and it was out of the work of a hidden variables proponent.

Remember, Copenhagen was not a physical collapse theory (except for a few minority “physical” proponents). Earlier physics was highly regarded philosophically in part for having clear ontologies, e.g. Newton’s work. Copenhagen was seen in part as a step backwards in this respect. Hidden variables restored some of that past insistence on ontology, to philosophy’s delight.

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Because most "philosophers" do not feel good in an un-deterministic world. Generally speaking, "professionals" want to feel certain about their world, just as businessmen: more value (money) can be extracted out of a certain world, than from an uncertain one. (sorry for my cynicism).

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    @Ronald, I did not used the word indeterminism. However there are things in nature that occur without a cause ex radioactive decay. Well, some find the cause in the definition itself... Commented Apr 14 at 17:11
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    @Ronald That is a bold statement. Our lives and the world around us are full of coincidences and random events that don't have a discernible cause. The weather, what we dream or think of at any given moment, chance encounters, rogue waves that kill people and sink ships. Children are conceived, or not. Resemble their mother, or father, or not. Die from an infectious disease, or not. Die later of cancer, or not. A tree that falls on a lumberjack or just misses him. A shark attack (or none). I think you are thinking wishfully. Commented Apr 14 at 17:13
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    @Ronald, by the way, Heisenberg did not believe in any of the deterministic interpretations, read his book for reference. Commented Apr 14 at 17:14
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    @Ronald In fact, the idea that the world is predictable, works like an intricate clockwork and would in principle be as predictable (if we only knew enough!) is as new as clockworks, i.e. emerged in Baroque times. For hundreds of thousands of years before that, and for many people even today, nature's workings were ascribed to gods. It's part of our civilizational delusion to think we have everything under control. We don't. Commented Apr 14 at 17:17
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    Looks as if Ronald withdrew his comment. Commented Apr 14 at 17:33

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