I Instrumentalism and consistency

[Demystifier]

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

 

[bhobba]

Well I can't 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 can't 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:
https://www.quantamagazine.org/string-theorys-strange-second-life-20160915/

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

Thanks
Bill

 

[Fra]

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 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.

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:

/Fredrik

 

[ueit]

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.

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.

 

[Demystifier]

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.

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.

 

[Lord Jestocost]

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".

 

[ueit]

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.

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

https://arxiv.org/pdf/1311.5253.pdf

Fuchs, Mermin and Schack claim:

QBist quantum mechanics is local because its entire purpose is to enable any single agent to organize her own degrees of belief about the contents of her own personal experience. No agent can move faster than light: the space-time trajectory of any agent is necessarily timelike. Her personal experience takes place along that trajectory. Therefore when any agent uses quantum mechanics to calculate “[cor]relations between the manifold aspects of [her] experience”, those experiences can not be space-like separated. Quantum correlations, by their very nature, refer only to time-like separated events: the acquisition of experiences by any single agent. Quantum mechanics, in the QBist interpretation, cannot assign correlations, spooky or otherwise, to space-like separated events, since they cannot be experienced by any single agent. Quantum mechanics is thus explicitly local in the QBist interpretation.

I find such a view ridiculous but it seems that respectable physicist hold it.

 

[Demystifier]

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.

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!".

 

[akvadrako]

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.

 

[Fra]

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)

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.

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 won't even attempt to motivate why this in the thread, but let's 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.

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!".

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.

/Fredrik

 

[Demystifier]

@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.

 

[Lord Jestocost]

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".

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.

 

[AlexCaledin]

... only measurable things are meaningful and therefore physical.
... 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?

- 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".

 

[bohm2]

This is one problem with Quantum Bayesianism and relates to this thread:

The puzzle is this: if there are only subjective probabilities, if gathering data does not help us track the extent to which circumstances favour some event over another one (this is the denial of objective single case probability), then why does gathering data and updating our subjective probabilities help us do better in coping with the world (if, that is, it does so)? Moreover, why should it be expected to? Why, that is, should one even bother to look at data at all? It’s not as if it’s going to guide us in what the world will throw at us; it just leads us to a different subjective probability distribution. An unexplained gap opens up between the means of the enquiry and its ends. Put in terms of reasons and beliefs: if one’s reasons derive from the experiments one has performed then it is unclear how these could provide good reasons for belief that such-and-such is to be expected, or good reasons to act in such-and-such a way..

The Bayesian may try to avoid this but as Timpson points out, other problems follow:

There is an immediate reply to this, of broadly Darwinian stripe. That is: We just do look at data and we just do update our probabilities in light of it; and it’s just a brute fact that those who do so do better in the world; and those who don’t, don’t. Those poor souls die out. But this move only invites restatement of the challenge: why do those who observe and update do better? To maintain that there is no answer to this question, that it is just a brute fact, is to concede the point. There is an explanatory gap. By contrast, if one maintains that the point of gathering data and updating is to track objective features of the world, to bring one’s judgements about what might be expected to happen into alignment with the extent to which facts actually do favour the outcomes in question, then the gap is closed. We can see in this case how someone who deploys the means will do better in achieving the ends: in coping with the world. This seems strong evidence in favour of some sort of objective view of probabilities and against a purely subjective view, hence against the quantum Bayesian.

http://users.ox.ac.uk/~bras2317/qb_s.pdf

 

[Fra]

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:

http://users.ox.ac.uk/~bras2317/qb_s.pdf

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

/Fredrik

 

[Demystifier]

- but what's wrong/inconsistent with thinking in terms of such concepts??

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.

 

[Lord Jestocost]

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.

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.

 

[zonde]

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.

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.

 

[Fra]

This is one problem with Quantum Bayesianism and relates to this thread:

The puzzle is this: if there are only subjective probabilities, if gathering data does not help us track the extent to which circumstances favour some event over another one (this is the denial of objective single case probability), then why does gathering data and updating our subjective probabilities help us do better in coping with the world (if, that is, it does so)?

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.

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:

here is an immediate reply to this, of broadly Darwinian stripe. That is: We just do look at data and we just do update our probabilities in light of it; and it’s just a brute fact that those who do so do better in the world; and those who don’t, don’t. Those poor souls die out. But this move only invites restatement of the challenge: why do those who observe and update do better? To maintain that there is no answer to this question, that it is just a brute fact, is to concede the point. There is an explanatory gap. By contrast, if one maintains that the point of gathering data and updating is to track objective features of the world, to bring one’s judgements about what might be expected to happen into alignment with the extent to which facts actually do favour the outcomes in question, then the gap is closed. We can see in this case how someone who deploys the means will do better in achieving the ends: in coping with the world. This seems strong evidence in favour of some sort of objective view of probabilities and against a purely subjective view, hence against the quantum Bayesian.

http://users.ox.ac.uk/~bras2317/qb_s.pdf

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, let's think of if as cosmological time. I don't 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.
https://www.amazon.com/dp/1107074061/?tag=pfamazon01-20

But as I've 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 realizes 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.

/Fredrik

 

[akvadrako]

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".

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?

 

[bhobba]

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

I may be dumb but as mentioned before a few stray photons from the CBMR is enough to give a dust particle an effective position. In that case what is the observer, indeed what is the system? What, purely in quantum terms, is an observation?

Thanks
Bill

 

[Lord Jestocost]

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.

That simply means: Instrumentalists are not so naive to mistake the map for the territory.

 

[bohm2]

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?

I guess I find it hard to believe that objective reality consists of just observers (conscious agents) or just points of view with nothing else. And the problem of indistinguishibility would seem unbridgeable. How could you possibly determine which is the correct picture? Having said that (and assuming I'm interpreting both yourself and Fra correctly) there is a cognitive scientist (Donald D. Hoffman) who does hold that view:
https://www.researchgate.net/publication/263704213_Objects_of_consciousness
His university page:
http://www.cogsci.uci.edu/~ddhoff/

 

[Daria K]

That simply means: Instrumentalists are not so naive to mistake the map for the territory.

@Lord Jestocost , I am curious, what is your opinion in this paper:
https://arxiv.org/pdf/1701.04081.pdf

The authors claim that they registered photons pre-measurement state and consider it as real wavefunction.

 

[akvadrako]

In that case what is the observer, indeed what is the system? What, purely in quantum terms, is an observation?

I was hoping to hear some others' answers to this, but I think the observer is any system with internal degrees of freedom, such that it can make records. This is what I was reminded of by Fra's post:

Quantum theory from questions
Philipp A Hoehn, Christopher Wever; Phys. Rev. A 95, 012102 (2017); arXiv:1511.01130

It is in a sense purely instrumentalist, since the main assumption is just that you can collect bits of information from your environment.

 

[Lord Jestocost]

@Lord Jestocost , I am curious, what is your opinion in this paper:
https://arxiv.org/pdf/1701.04081.pdf

The authors claim that they registered photons pre-measurement state and consider it as real wavefunction.

When reading the paper (https://arxiv.org/pdf/1701.04081.pdf), I already stumbled upon the following sentences:

“In contrast, the determinists (common-sense understanding) argue that the past of photons should be realistic and deterministic prior to the detection. To investigate when a photon’s nature is determined and whether there are ‘hidden variables’, a number of delayed-choice experiments have been proposed and conducted over the past several decades[5]. The results show that the detecting device always determines which nature of a photon can be observed—as a wave, a particle or even a wave-particle superposition[8-20]. Based on the thinking paradigm that the past can be deduced from time reversal of the observed phenomenon, these results lead to the time paradox of a choice made in the present to alter a photon’s past. Therefore, the Copenhagen interpretation has to deny the reality of wavefunctions and follows a creed that no elementary phenomenon is a phenomenon until it is a registered phenomenon, making quantum mechanics an epistemic theory.”

Let’s assume that there a quantum objects (quons) which we term “photons”. What delayed choice experiments really show is that quons don’t exist as particles or waves, but are truly “quantumstuff” which can “exhibit” particle and wave properties (both classical conceptions) in certain experiments. It is not true that a quon sometimes behaves like a wave and sometimes like a particle. It always behaves like itself, but we sometimes "choose" (how we think) to measure one property, sometimes another. A choice made in the present doesn’t alter a quon’s past, it’s only up to us how we “see” its past.

 

[mikeyork]

It seems to me that the distinction between an objective reality and an observer's context of a collection of observables and a frame of reference is implicit in the Hilbert space formalism. $|\psi>$ represents the objective state $\psi$ and the eigenbasis in a given frame of reference represents the observer's context.

 

[vanhees71]

It's $|\psi \rangle \langle \psi|$ that represents the state, not $|\psi \rangle$ itself. Further, whenever you talk about an eigenbasis you have to specify about which linear operator you are talking.

 

[Fra]

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 le??ft. And the only initial rules are about the limits of acquisition of information. Is that about it?

The summary you attempt here, is a non-physical one in the sense that an inside observer can not compute this. You will both run out of memory and on out time. You can not claim to have an exhaustive list of observers or anything like that, for several reasons: first they are not static, second you need the "hardware" to encode and compute this list. From the point of view of a given observer the environment is a black box, but there view of the black box is constraind by the observers complexity. So the simpler observer - simpler does the picture of the universe look like (but very unpredictable). Thus all the different observers does not a priori agree upon their common environment.

However it is not forbidden that they DO effectively agree in the sense that all the observsers "truncated" pictures do not fight each other. IF they do then to a certain extent the solipsist game has reached a kind of equilibrium point. Not equilibrium in the sense that nothing happens, but equilibrium in the sense of a rought agreement on their commonn environment.

This works only for the special case where a dominant classical observer studies a small subsystem. Such as is the case for a typical HEP accelerator experiment. Then yes, the human populated Earth based laboratory will see an effective "observer invariant" objectivity. Our job is then to find these observer invariants. this is possible becase we can "repeat" the experiments and no matter what the results are, it will not threaten the Earth lab. But the problem is still to FIND the laws.

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

A system where all the subsystem observers happen to be in a stable agreement about some of their differing views, in the sense that i think you suggest, will be interpreted as a kind of equilbrium state where the dynamics takes place in a stable configuration space with stable laws and a stable "population" of observers. Ie a stable eco system that does not change over cosmological time.

But in the general case, the observers might be in disagreement not only about their "states" but even about the rules of interaction and the structure of their common environment. This is the process where the population of observers and its speices evolve. As long as we do not have a stable system of observers, and evolving laws, it is s sign of that there is no observer invariant reality. My point is in fact that this is supposed to EXPLAIN the emergence of stable laws. And they key here is to take deeply seriously, the idea that action of each obserers depends only upon its own state, which in turn encodes its information about its environment. This is a key to the epistemological solipsist picture, and suggest that the behaviour of systems follows from a random scrambling of its own state. And the trick is to develop a structure/code so that the random scramling actually turns out non-random.

The main advantage of the idea here (or so is the conjecture) is that it may help us explain WHICH the various effective obeserver invariants are, and how they have come into beeing. Ie. we have the possibility here (as per the epistemoligical solipsism) to understand the "information mechanics" behind WHY the laws of nature are what they are. Current standard model is far less ambitious as it was constructed ontop of an old heritage of empirical facts, and classical mechanics. No wonder what we have is a patchwork of working theories with the lack of conherent reasoning from start to end. I argue that this will not do if we seek to understand things deeper and hope to unify forces.

/Fredrik

 

[AlexCaledin]

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.

- why is it unnatural? We know that there are the observable events, connected by some objective mathematics (which might well be some unimaginable algorithm of "the Great Transcendent Computer" simulating/generating the whole physical aspect of reality). The best theorists did their best to get the useful ideas about that mathematics; so now it's quite natural - because we've got nothing better - to think in terms of / according to those mathematical ideas until better ideas are discovered.

"... we needn’t take our best theory to be true. It’s simply the best ladder we have to our next theory."
- Donald D. Hoffman

 

[mikeyork]

It's $|\psi \rangle \langle \psi|$ that represents the state, not $|\psi \rangle$ itself.

That seems to me to be a distinction without a difference since $|\psi \rangle \langle \psi|$ has menaing only because of $|\psi \rangle$.

Further, whenever you talk about an eigenbasis you have to specify about which linear operator you are talking.

That's what the observer does.

 

[Fra]

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.

A problem appears when we use terminology that really comes from "human philosophy" rather thab phyics and thus by logical positivism one ofter refers to _human understanding_ and consciuous brains.

The kind of discrimination i make is that both direct and indirect observations are fine as "observable". Indirect observations are i think sometimes called analytical in old philosophy but my point is that for a given observer there are physial limits on the "analytical power" or computational capacity that renders some complex observations non observable _to that observer_ and thus the action of this observer should be invariant with respect to this.

One of the most common fallacy imo is for a human scientist to come up with complex ideas and project that down to a Planck scale observer.

The trick is that that Planck scale physics looks complex only from the low energy limit! But the naked interactions can not be this complex for infromation processing reasons.

/Fredrik

 

[Lord Jestocost]

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.

Why is instrumentalism naive? And what are “non measurable things“? Can one say any more about the physical world others than about “linkages of pointer readings with pointer readings”? That's the "physical world".

 

[bahamagreen]

Perhaps instrumentalists are being naive and inconsistent to the degree that despite certainly knowing that everything we perceive is an internal phenomenological mental construction, the instrumentalist attaches an external objective naive realism upon his internal mental phenomenological construction of a dial pointer.

 

[Demystifier]

- why is it unnatural? We know that there are the observable events, connected by some objective mathematics (which might well be some unimaginable algorithm of "the Great Transcendent Computer" simulating/generating the whole physical aspect of reality). The best theorists did their best to get the useful ideas about that mathematics; so now it's quite natural - because we've got nothing better - to think in terms of / according to those mathematical ideas until better ideas are discovered.

"... we needn’t take our best theory to be true. It’s simply the best ladder we have to our next theory."
- Donald D. Hoffman

I mean "unnatural" in a different sense.

 

[Fra]

I mean "unnatural" in a different sense.

I think that it is indeeed natural for humans to try to create a mental picture of the "reailty" out there, that exists when we close our eyes. In fact its how we navigate, relying on our map.

I do not see any contradiction between the empirical solipsism and the naturalness for humans to seek realism. On the contrary do i think they are a perfect match because it is the "strive" of all observers to understand the reality in the black box that eventually creates the effective reality. And i think of the reason for this is that is becomea sometimes the "best approximation" given than a simple observer can not endcode a complex map.

If i understand demystifier right i agree that it is unnatural in this sense.

/Fredrik

 

[Demystifier]

Yes, that's what I meant.

 

[Demystifier]

That simply means: Instrumentalists are not so naive to mistake the map for the territory.

That's true, and that's a good thing about instrumentalists. But they are naive in a different sense. They are naive when they think that they never mistake the map for the territory.

Realists, on the other hand, are aware that it can be cognitively useful to think of map as a territory. Therefore they make maps which look more realistic and much better resemble the territory.

 

[zonde]

Perhaps instrumentalists are being naive and inconsistent to the degree that despite certainly knowing that everything we perceive is an internal phenomenological mental construction, the instrumentalist attaches an external objective naive realism upon his internal mental phenomenological construction of a dial pointer.

I would say that the level of certainty with which instrumentalist attaches realism to internal mental construction is naive. As Demystifier said we attach reality to certain mental constructs, but this attachment is not absolute, just useful. Sometimes this attachment is so useful that there is not much point questioning it any more. But anyways this happens over time when we develop more useful models that relay on particular concept.

 

[Lord Jestocost]

That's true, and that's a good thing about instrumentalists. But they are naive in a different sense. They are naive when they think that they never mistake the map for the territory.

Realists, on the other hand, are aware that it can be cognitively useful to think of map as a territory. Therefore they make maps which look more realistic and much better resemble the territory.

Instrumentalism is a non-realist approach to quantum mechanics:
“From the early days of quantum mechanics, there has been a strain of thought that holds that the proper attitude to take towards quantum mechanics is an instrumentalist or pragmatic one. On such a view, quantum mechanics is a tool for coordinating our experience and for forming expectations about the outcomes of experiments.“ (from https://plato.stanford.edu/entries/qt-issues/)

Why should an instrumentalist ever mistake the map for the territory? What territory?

 

[Demystifier]

Why should an instrumentalist ever mistake the map for the territory? What territory?

Ideal persistent and consistent instrumentalist would never make such a mistake. But such an ideal instrumentalist does not exist in human species. Perhaps you could program an ideal computer instrumentalist, but there is no ideal human instrumentalist.

 

[Demystifier]

Let me use a simple analogy. Suppose that you watch your computer screen on which two windows are open, window 1 and window 2. And suppose that you see only window 1. Why don't you see window 2? A natural intuitive explanation is that window 2 must be behind window 1. And really, when you move window 1, you start to see window 2. There is nothing more intuitive for a human than to think that window 2 was there, behind window 1, even before you moved window 1. On the other hand, if you know something about how computer and monitor really work, you know that it isn't true. In reality, window 2 was "made" on the monitor at the moment when you moved window 1, it was not there before. And yet, even if you are a computer expert, even if you programed the computer that way yourself, you will still find cognitively natural and useful to think that window 2 was there all the time.

That's a hidden variable, or realist, interpretation. Even though there is no window 2 before you see it, you interpret that it is there even when you don't see it. And even though this interpretation is wrong, it is a very useful interpretation for a human.

In the same sense, a hidden variable interpretation of QM, such as Bohmian mechanics, can be useful as a thinking tool, even if Bohmian trajectories don't exist in reality. The point of Bohmian mechanics is not to restore determinism. Its point is to restore realism, that is the view that things are there even when we don't observe them.

 

[vanhees71]

Well, Window 2 "was there" in some sense already. Although not shown on the screen, the information provided by it was stored in "bits and bytes" in the Computer's memory (no matter, how this works in all technical detail). So in a sense the picture in Window 2 has been there. Of course, it's built up on the screen only at the moment you shift away Window 1, but in the sense of information it has been there before in the computer's memory.

I think this metaphor elucidates very well, the meaning of quantum states as providing (probabilistic) information about a system due to preparation, but that's again interpretation, and maybe provokes heated debates about "epistemic vs. ontic" interpretations.

 

[Fra]

(Apologies in advance for not linking to demystifiers papers.. typing this in from the phone and physicsforums app)

if you programed the computer that way yourself, you will still find cognitively natural and useful to think that window 2 was there all the time.
...
That's a hidden variable, or realist, interpretation. Even though there is no window 2 before you see it, you interpret that it is there even when you don't see it. And even though this interpretation is wrong, it is a very useful interpretation for a human.
...
Its point is to restore realism, that is the view that things are there even when we don't observe them.

I can't avoid observing that there is an abstraction here that makes realism as per Demystfier suspiciously alike what i call "rationality". Rationality that can be furher used in the inferential picture to explain the expected evolution.

This connection is even more interesting if you think of future possible ways to distinguish demystifiers solipsist hidden variables from regular QM.

The conceptual argument is that an observer (which we should think of as a PLAYER in an enviromment that offers both opportunities and dangers) that is behaving rationally will places his bets - according to his map - anything else is simply irrational, EVEN if the map is wrong as per another perspective. And in the exampl above we can argue that the best guess is indeed that the other window is below.

So what if what demystifyers "useful" interpretation" is simply a "rational expectation"?

Of course tere needs to be a formalism behind this, but i see a hope in the future discrimination D mentions in his solipsist paper. Namely that if we take this seriously (ie that alice actions depends only on her HV (to stick to D's terminology) and Bobs only on his. Then consider Observer3 that is bigger atr more domimant... observing/interacting with the "alice and bob interacting"-system... now in this pictute i see the chance for these ideas to distinguish themselves from just an interpretation by requiring that in O3's observers "rational expectaion" of composite Alice-Bob system the "internal interactions" between alice and bobs reflects this logic.

Thus this impacts unification! We are no longer "only" making reinterpretations.

Q. Demystifier, does this realism ~ rationality analogy make sense in conjuction with your journey?

(Hope this gets readable. Typing a lot on the phone is not ideal)

/Fredrik

 

[Demystifier]

I think this metaphor elucidates very well, the meaning of quantum states as providing (probabilistic) information about a system due to preparation, but that's again interpretation, and maybe provokes heated debates about "epistemic vs. ontic" interpretations.

The debates are heated when people discuss which interpretation is "right". What I propose here is that emphasis should not be on which interpretation is right, but on how various interpretations are useful as thinking tools. You often complain that you don't see how Bohmian view is useful (let alone true), and the analogy above should explain that. And just because Bohmian view is useful (at least for some users) doesn't mean that some more standard view is less useful.

 

[Demystifier]

Q. Demystifier, does this realism ~ rationality analogy make sense in conjuction with your journey?

I guess it does.

 

[vanhees71]

The debates are heated when people discuss which interpretation is "right". What I propose here is that emphasis should not be on which interpretation is right, but on how various interpretations are useful as thinking tools. You often complain that you don't see how Bohmian view is useful (let alone true), and the analogy above should explain that. And just because Bohmian view is useful (at least for some users) doesn't mean that some more standard view is less useful.

BM is ok for non-relativistic QT. It's at least not contradicting any fundamental laws. I personally consider it useless, because it doesn't provide any further insight compared to minimally interpreted standard QT. It's also hard to say, which interpretation is "right". It's, however, easy to say, which interpretational pieces are definitely wrong, among them the assumption of an instantaneous collapse in relativistic QFT. Then there is the category of interpretational items that are simply not testable within the realm of natural sciences as the assumption of a classical-quantum cut. At least so far there's no evidence for such a thing.

 

[Lord Jestocost]

Ideal persistent and consistent instrumentalist would never make such a mistake. But such an ideal instrumentalist does not exist in human species. Perhaps you could program an ideal computer instrumentalist, but there is no ideal human instrumentalist.

If I understand you correctly: Of course, even an instrumentalist has – as a human being – the feeling that there is “some reality” or “some territory”. But the feeling that there is “some reality (territory)” emerges merely from the usefulness of our “mental concepts (map)”; the usefulness for finding our ways, for our thinking and for our communicating with others. The more useful the map the stronger is the feeling that we are really wandering through “some territory”. To my mind, however, the map isn’t able to tell us finally what the “TERRITORY” is: There are mental images, which are in our minds and not in the external world, and there is some kind of “counterpart” in the external world which is of inscrutable nature.

 

[Demystifier]

If I understand you correctly: Of course, even an instrumentalist has – as a human being – the feeling that there is “some reality” or “some territory”. But the feeling that there is “some reality (territory)” emerges merely from the usefulness of our “mental concepts (map)”; the usefulness for finding our ways, for our thinking and for our communicating with others. The more useful the map the stronger is the feeling that we are really wandering through “some territory”. To my mind, however, the map isn’t able to tell us finally what the “TERRITORY” is: There are mental images, which are in our minds and not in the external world, and there is some kind of “counterpart” in the external world which is of inscrutable nature.

Yes, you explained it very well!

The only thing I would add is this. Since those mental images can be very useful, science should not strive to avoid them. Just the opposite, in addition to making testable predictions (which is what pure instrumentalists tend to do), theoretical science should also strive to develop good mental images. To answer whether some mental image is "true" or not, it can be left to philosophers. But the construction of useful mental images is too important to be left to philosophers.

 

[akvadrako]

To answer whether some mental image is "true" or not, it can be left to philosophers. But the construction of useful mental images is too important to be left to philosophers.

I would like to add that I see something in between philosophically true and useful. Newtonian gravity and GR are both useful and perhaps Newtonian is even more so, depending on the use case. But I would say the question of which is more true also lies within science, not just philosophy.

I'm not sure of the precise criteria, but I can see some trends. When theory B is strictly a limiting case of theory A, we should say A is more true. Or when A has strictly less assumptions than B. Or when A is applicable in more general cases. I suppose finding exactly what criteria to use is part of the philosophy of science, because science can't be self-defining. But I don't think the search for truth can be left to philosophy.