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I Instrumentalism and consistency

  1. Sep 26, 2017 #1


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    One approach to deal with interpretations of quantum mechanics is instrumentalism, known also as logical positivism. According to this doctrine, only measurable things are meaningful and therefore physical. All other concepts such as reality, ontology, hidden variables or many worlds, i.e. things which are supposed to be there even if we don't measure them, are not measurable and hence are meaningless.

    There are many physicists who claim to think that way, but is there any living physicist who really thinks that way? In other words, is there any physicist who is consistent in such a way of thinking, without ever thinking in terms of concepts which are supposed to be there even when we don't measure them? In my experience, there is no such physicist.

    Here is an example:
    Regarding consciousness causing wavefunction collapse
    Last edited: Sep 26, 2017
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  3. Sep 26, 2017 #2


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    Well I cant speak for anyone but myself, but for me positivism type interpretations ie saying all their is is what instruments read are 'silly'. For example you need more than that to give a fully quantum definition of observation. A few stray photons are enough to decohere a dust particle and give it an effective postion - regardless of it is observed instrumentally or not.

    I remember when I posted a lot on sci.physics.relativity one guy who was a philosopher queried us with since positivism is very much in decline in philosophy these days does this affect the basic foundations of relativity. I had to carefully explain to him, and his professor who also got into the act, that these days it not about positivism - its more about symmetry. What you would call that philosophically beats me. Personally I think the same about QM - its more about what symmetry means when applied to QM - it does so much more than classically - there is something very strange going on here - I don't know what it is - but IMHO it's definitely not positivist. As one person says the standard model has some parts of dazzling beauty (that's the symmetry bit) and other parts an ugly kludge (that's the parameters you need to put in by hand). It's inconceivable (to me anyway) you can have the beauty without something much deeper going on and the ugly parts disappearing.

    I think someone mentioned to Einstein he once used positivist type arguments and if I remember correctly he said something along the lines - you cant do the same joke twice. That's pretty much my view as well. It may have been important at the start of relativity and QM but it's well worn out now. As Feynman says if you once used a trick to make progress it doesn't really work again because everyone would try it and progress wouldn't be stopped.

    What's the next big leap - my guess is some startling hidden symmetry - but who knows. String theory was a flop, at least for its intended purpose, but did seem to spawn many interesting areas that still are being investigated in a sort of second life:

    Maybe that will produce something startling - who knows. But I don't think positivism will make a comeback - still one never knows.

    Last edited: Sep 26, 2017
  4. Sep 26, 2017 #3


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    short answer: I think you are right.

    short version of a long answer:

    I am not sure. In my own the are physicsl "ontologies" but i think of them as forged by subjective interaction history in the physical sense (ie i am not talking about brains).

    So i would say ontologies are an essential reference for judging the present observations. It even defines the observer. BUT these ontologies does not come from nowhere, they are rather explained in the code that retains the instrumentalist inputs.

    If you think this makes no sense then see short answer:

  5. Sep 26, 2017 #4
    It is important to specify what do you mean by "measurable things". I would say that the gravitational field is measurable just like the electric and magnetic fields. Or, at least the effects of those fields on massive/charged particles are measurable. But in this case everything in the universe is measurable since any mass/energy produces gravitational fields and almost all matter (electrons and quarks) produces electric and magnetic fields.

    I guess that if you put it this way there should be a lot of positivist physicists out there.
  6. Sep 26, 2017 #5


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    Maybe, but a typical example of a positivist I am having in mind is a positivist who uses this positivism to argue that quantum mechanics is local.
    Last edited: Sep 26, 2017
  7. Sep 26, 2017 #6
    Well, I can't speak for anyone but myself, too: My thinking is highly influenced by Arthur Stanley Eddington's "THE NATURE OF THE PHYSICAL WORLD". I have no idea whether he can be called an "instrumentalist".
  8. Sep 26, 2017 #7
    I think that Q-bists would hold such a view. But in their case they also assume that "measured" entities are just concepts in their minds. It is a really bad argument, full of holes, but there are physicists believing it.

    In this paper:

    An Introduction to QBism with an Application to the Locality of Quantum Mechanics
    Am. J. Phys., Vol. 82, No. 8, August 2014, 749-754


    Fuchs, Mermin and Schack claim:

    I find such a view ridiculous but it seems that respectable physicist hold it.
  9. Sep 26, 2017 #8


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    They say they believe it, but I don't believe they really believe it. If they really believed that then they would be solipsists, and no one of them wants to go that far to say "Yes, I am a solipsist!".
  10. Sep 26, 2017 #9
    A dedicated instrumentalist couldn't even claim the Earth orbits the Sun, because that's not a measurable thing. It's just a good model which predicts when the next sunrise will happen. Basically they have no model of the outside world at all. I don't know how many physicists the group includes, but "believers" of the simulation hypothesis seem to fit the bill.
  11. Sep 26, 2017 #10


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    This is hard to discuss for a couple of reasons and i hesitate to butt in, first there are many flavours of these ways of thinking, second I am not sure if this is a quantum physics question? I do not personally mind at all, but give the rules on here... (also they way I see this, its again a btsm question; because in my view, consistency brings more than pure QM into the picture)
    When you phrase it like this, and ueit brings up bayesian QM etc I do feel guilty.

    I think you somehow think that these people that seem to hold the flag of instrumentalism as a kind of "high standard" are not really consistent in their reasoning? Thats a valid critique indeed.

    And I actually agree with that in the specific sense that I personally think that one can not consistently hold this view, and just pretend that this as an "interpretation" of standard QM. There are so many ugly inconsistencies that if you go there, why not go all the way? I would say consistency alone suggest a reconstruction of "quantum mechanics"! And its in quotes because the resulting reconstruction will be mathematically different, but corresponding to QM just as an correspondence principle in the case of a classical and dominant observer (which IS the factual case in all HEP).

    I wont even attempt to motivate why this in the thread, but lets just say it has been a long journey, and while there are also qbists that argue for this, i have never so far found a published route that i can subscribe to. I have my own specific ideas, but certainly some of the qbist thinking is partly right up this alley. I am certainly working on what one can call a reconstruction of "quantum theory", but early insights is that consistency again requires us to consider the "code" where the information is stored. Here "matter" enters the picture, because is this is physics the interacting observerrs are certainly not interacting brains, it is interacting matter. All these things immediately suggests this is NOT just quantum physics, the suggestions take us righ into BTSM. Although its currently a formal speculation.
    Words are confuing there, some defitions of solipsism are just too stupid even for me - for example ontological solipsism that "only i exist". It should be clear that its very speculative and a fallacy.

    They kind of solipsism I can adhere to is a kind of epistemological view in the context of risk analysis. The way I estimate the outcomes of the future, depends only upon MY OWN information, this in turn reflects my own actions towards my environment. This indeed has a built-in kind of locality - the action of a system, described from the system itself, depends only upone locally coded information.

    This is an extreme form of empirical solipsism put into the perspective of a kind of risk taking game (which we can just call reality;-).

    I am not ashamed of this view, and i do not feel inconsistent. But as for everyday life, i also relay on ontologies of realism, but this is in cases
    where i due to my knowledge of my environment KNOW that this "model" works flawlessly in this domain.

    This is a very special form of solipsism, but its more than an interpretation, and i am not sure if you would could me in as a solipsist or not? If you call me a solipsist i will not be offended in any case.

    Sorry for this possibly unreadable comment. Go figure why i hesitated.

  12. Sep 27, 2017 #11


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    @Fra your "epistemological solipsism" is a rather soft version of solipsism, which is not the kind of solipsism I had in mind. I think your solipsism is consistent and not controversial at all.
  13. Sep 27, 2017 #12
    I had to rechek "THE NATURE OF THE PHYSICAL WORLD" by Arthur Stanley Eddington. He says:

    There is always the triple correspondence:

    (a) a mental image, which is in our minds and not in the external world;

    (b) some kind of counterpart in the external world, which is on inscrutable nature;

    (c) a set of pointer readings, which exact science can study and connect with other pointer readings.
  14. Sep 27, 2017 #13
    - but what's wrong/inconsistent with thinking in terms of such concepts?? They are not physical because they are purely mathematical. They are chosen (arbitrarily to some extent) to be the mathematical objects/methods in our calculations; and after that choice physicists cannot help thinking in terms of them. In the calculations, they come in between the observable events - and only in such mathematical way they are "supposed to be there".
    Last edited: Sep 27, 2017
  15. Sep 27, 2017 #14
    This is one problem with Quantum Bayesianism and relates to this thread:
    The Bayesian may try to avoid this but as Timpson points out, other problems follow:
  16. Sep 28, 2017 #15


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    Thats a valid and importat point indeed. Ie how do we explanim the apparent factual objectivity when starting from sunbective views?

    I will throw in my reply to this later when i havem more time

  17. Sep 28, 2017 #16


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    You missed my point. Such a thinking by itself is not inconsistent. But it is unnatural for humans to really think that way, so in practice there is no human physicist who always thinks that way.
  18. Sep 28, 2017 #17
    You cannot avoid to think - to use your words - in terms of one “concept” which cannot be measured and must not be measured because we ourselves know about.
  19. Sep 29, 2017 #18


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    I would say that instrumentalism is naive. There is no strict borderline between measurable (observable) things and non measurable things. There are just concepts that taken as real make our reasoning much simpler.
  20. Sep 29, 2017 #19


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    Just to make sure we arent disagreeing upon words here:

    When i say objective, I mean specifically "observer invariant".You can also include here superficially observer dependent observations that happen to be related by a known objective time indepedent transformation, typically a symmetry group.

    With subjective i then mean that the observation is fundamentally defined within the contex of a given observer, and there exists no a priori symmetry that magically can "scale" or "transform" our obsevations to an arbitrary observer.

    For certain groups, this problem is solved. But you can go figure that there are MANY more ways to scale observers than just by say poincare transformations of special relativity, then the main problem is not just that of curved space time and diffeomorphism but the bigger problem is the mass and internal structure of the observer. Renormalization of observational scale, is sniffing also ontoi this.This is a deep problem and open problem. If you are really consistent about the inferential and subjective view, you see how many open wires there is in current theories. And it all more or less cleantly suggests that a reconstruction of this "meaurement theory".

    I remember reading the introduction of Carlo Rovellis LQG book fir the first time, and for quote some time his reasoning was brillaint, but quote soon he made a logical mistake imo, that lost my interest. The mistake was not to insist that the subjective view is somehow fundamental. The mistake was to assume that there exists a well defined ubersymmetry group. I think this is a fallacy, and also is the reason matter is separated from LQG.

    I can close the gap by considering an emergent and evolving objectivity.It is clear what even without an "effective objectivit" we would see just subjective solipsist chaos, ie. completeley unstable and divergent. This is now how the world looks like.

    The next step is hard to explain unfortunately as its an open issue, but i willtry to give the concept:
    Instead the observer learns about its environment, but the environment is not static, its composed of a sea of fellow observers that are in the same situation. So what happens is that we have a chaotic interacting mess of subjective observers, and their interactions means they are learning about each other. And this alone brings them together and creates stability. Even the very RULES of the interaction game are developed here, so this connects also to one resolution to Smolings Evolution of law. You may think that this is a circular reasoning, that that is kind of right, but the circular process here has a physical meaning - this is just time. Or to not confuse with clocks, lets think of if as cosmological time. I dont expect you all to get the idea from a simple explanation, but i would say that this is very complex and nonlinear indeed and i wish itwas simpler, but consistency ismply has led me to this conclusion.

    These ideas of eternal objectively real supersymmetry that will seal together are forces in a timeless structure, are a fallacious way of thinking. This is explain in many ways in smolins and roberto unders various books, like this one.

    But as ive read this i do not think smolin has the right final resolution to the metalaw dliemma.

    IMHO, this is conceptually quite clear to me and has been for a some years, but what is the hard part is to find the right mathematical formalism that realises this, in a practical way. But somehow the starting point is a reconstruction of the basics. Due to the computational comlpexity it is also probably impossible to simulate a sea of interacting observers, as it woudl effectively be a sea of interacting "computing devices". If we from such a simulation could see that the emergent interactions rules, match the standard model, SR and GR, that woudl be the goal.

    And I kind of see this vision as an extermal version of epistemological solipsism, where objectivity is emergent, rather than timeless and static.So its not that we do not have any effective objectivity at all, its just that its not "an ontological timeless matematical observer independent truth",

    Edit: I just see how tricky it is to explain. what i argue for above is that even given the initial solipsist chais, there will be a self organisation due to evolution of observers that persist. And with this we should think of the the prototype observers as the elementary particles. So i envision that 99% of these negotiations took place in the first fractions of the second after big bang. So i am not envisioning this as interacting brains.

    Last edited: Sep 29, 2017
  21. Sep 29, 2017 #20
    Let me see if I understand what you are saying. So for each observer (or system) there is a real outside world which consists of all the other observers. And if you take into account the subjective view of every observer, there is nothing left. And the only initial rules are about the limits of acquisition of information. Is that about it?

    If so, how do you distinguish it physically from having a single objective (observer invariant) reality where each observer is replaced with elementary systems?
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