The quantum state cannot be interpreted statistically?

[Ken G]

Ken G is advocating Idealism (when not beating around the bush), i.e. reality is fundamentally mentally constructed and a skepticism about the possibility of knowing any mind-independent thing, i.e. diametrically your position.

No. Once again you have failed to understand my point! Idealism is quite different from what I'm advocating, I'm actually advocating something more along the lines of "scientifically consistent realism." The difference between idealism and realism is simple-- idealism asserts that reality is fundamentally mind-constructed, so there is no reality outside the mind. This would also require I speak of my mind, because if there is no reality outside my mind, then your mind does not exist outside of my mind. I've never said any such thing, just look.

Indeed, scientists often find it useful to adopt realism, and I am no exception. Realism asserts that there is a reality outside our minds, and our minds are trying to figure it out. This is the stance I take. But here we must distinguish two brands of realism, which I would call "naive realism" (the idea that when we conceptualize reality, we hit it spot on, in complete contradiction with both the obvious limitations of our senses and our intelligence, and ignoring the clear evidence to the contrary from the history of our own physics), versus what I would call "scientifically consistent realism" (a realism that does not disregard that evidence).

So what am I actually saying? First of all, it's a bad idea to get my ideas interpreted through DevilsAvocado, because he always needs to replace them with something different so he can find some oversimplified objection to them. What I am actually saying is that given that physics changes all the time, and given that we only have our intelligence, historical experience, technology, and five senses to draw upon, the way we conceptualize reality is always going to be different from actual reality. Scientifically speaking, "reality" is the former, not the latter-- it is what we can say about reality, what our physics reveals about reality, but we have no coherent language for even talking about reality as it truly is. So there are no "true" ontologies in physics, there is just what we choose to regard as true, along with the reasons we choose to do that. These choices are contextual and provisional, and can vary in the same paragraph as we describe some physical phenomenon. This is as it should be-- we never had any other scientific relationship with reality, and we should not pretend we ever did or ever will. We simply confuse our own goals when we don't recognize what scientific realism actually is.

"So that is the sense that I am saying there is a crucial role of consciousness in quantum mechanics-- there simply is no such thing as quantum mechanics without it."​

Yes, that is what I am saying, but note there is nothing in that statement that represents idealism. All there is is the recognition of what quantum mechanics is, and the demonstrable fact that quantum mechanics is our attempt (one of many) to understand reality.

And sometimes "quantum mechanics" is everything there is, the whole world and the universe.

Again, your "interpretations" border on the ridiculous. All may be well assured that every time I say "quantum mechanics", I mean just one thing: the theory of quantum mechanics, like you can find in any textbook. I can't even imagine why anyone else would use the term to mean anything different.

 

[DevilsAvocado]

Again, your "interpretations" border on the ridiculous. All may be well assured that every time I say "quantum mechanics", I mean just one thing: the theory of quantum mechanics, like you can find in any textbook. I can't even imagine why anyone else would use the term to mean anything different.

Well, you tell me. The fact is that this is exactly what you do, from the thread "Quantum Eraser and Its Implications":

I'm pointing out that the fundamental weirdnesses associated with two-slit experiments are fundamentally about the role of the consciousness, for the simple reason that only a conscious being can perceive a nonunitary outcome.

This is not theory, this is an empirical experiment, and as usual "your consciousness" plays a fundamental role in this. I leave it to the reader to decide what’s ridiculous or not.

So what am I actually saying?

That’s what we are all wondering.

It seems like contradictions. Fredrik & my_wan has spent numerous posts on you, trying to sort things out, without success.

I hope you don’t blame me for this failure as well.

 

[Ken G]

Certainly in some cases we know we are working with a "useful fantasy", but to say that because we are fundamentally limited in our capacity to "know" entails that all such characterizations are factually "useful fantasies" tacitly oversteps what we can factually know, such a claim is a mind projection fallacy.

How can you tell in which cases we are working with a "useful fantasy" about the reality and which cases we are working with the actual reality? To even make this language internally inconsistent, we must accept that even fantasies have a sliding scale of connection to reality, which is just what I mean by "usefulness", but never cross a line into being something fundamentally different from a fantasy-- all that demonstrably changes is the usefulness of the fantasy. Yes, in standard language, we don't call something a fantasy any more if it has demonstrable usefulness, but this is sheer convenience-- we do not need to lose sight of the fact that the same basic process occurs with a useful fantasy and a pure fantasy, they are both mental pictures we adopt to achieve some purpose. All that changes is the purpose, and the standard of usefulness that is applied. My use of the term "fantasy" is not designed to suggest that science is pure fantasy, it is designed to place scientific thinking into its demonstrably proper place: inside our head, where it quite clearly does indeed occur.

To some realist your opinion as stated does not even constitute realism.

Indeed, and this is the central point. I'm not trying to divert this thread into a discussion of my personal philosophical opinions, this issue is right at the heart of just exactly what it is that PBR has proved about valid interpretations of quantum mechanics. PBR have adopted a very narrow view of what realism is, too narrow to be able to claim that they are using "only mild assumptions." Their version of realism is indeed often adopted by scientists, but I claim that it is internally inconsistent with science.

Now, I will admit that it is typical for scientists to adopt a view of scientific ontology that is perfectly convenient but rather naive, and is not really consistent with either the historical trajectory of science, nor to what scientists actually do. In particular, nothing in the history of physics, nor in the actions of any physicist, actually require any such thing as a concept of a true physical ontology (including the concept of "properties" that drive the logic of the PBR argument). In history, and in practice, all physical ontologies are borrowed from mathematics, and have no formal status within physics itself. They are contextual, provisional, and goal-oriented, a fact that is perfectly demonstrable by considering any standard physics curriculum. Thus, there is no basis for claiming that "realism" involves regarding physics as something that it has never been and likely never will be. None of this has anything to do with my personal philosophical choices, it is all just demonstrable truths about what physics is, not what we might like it to be. So I am arguing that the "realism" that PBR regards as a "mild assumption" in their proof is not only highly unrealistic, it is an example of the mind projection fallacy. Or should I say, the mind projection fantasy!

In other words it makes no sense to define the world in which we directly interact "the physical world" while also denying that the actual constituents from which the world is derived are not physical. Like denying atoms are not real, but hurricanes are. In a sense that is trying to have your cake and eat it to. So I'm not objecting to either an ontic or epistemic foundational characterization. I'm simple saying that if you label it one way at the experiential level then denying those same labels at a different level is incongruent.

And I would say the simple path that avoids any such incongruences is simply recognizing that any ontological statements we choose to make, whether they be about hurricanes or atoms or any physical "properties" of our world, are all going to be effective and useful pictures that we are choosing to borrow from conceptual structures like mathematics or everyday experience, and have no separate "existence" in the real world-- they exist only in the conceptual structures that we borrow them from. Same for properties-- so we can use properties within the context that they serve us, but we cannot prove things from using them, we cannot let a picture drive our logic that tells us what kinds of interpretations of quantum mechanics are possible, unless we allow that our proof only applies to those who would enter into our picture, and make our "mild" assumptions.

For instance, you state the opinion that it is natural that real ontic entities are not the foundational basis of the universe. If I applied you judgement of Jaynes to this statement couldn't I insist that you are not a realist, and that calling yourself so constitutes a mind projection fallacy ostensibly to justify the [real]ity of your own opinion?

The issue here is, which should we regard as the "null hypothesis": that the ontic entities we create in our language about reality really are the foundational basis of the universe, or that they really are only what we can demonstrate them to be (ideas we create in our language and our mathematical theories, which are then transplanted from the conceptual structures in which they demonstrably exist and used in physical contexts where they do not demonstrably exist). All I am saying is this: the true realist must adopt the latter, not the former, as their null hypothesis, because to do otherwise is a basic category error. It is fully realistic to notice category errors, that's not a mind projection fallacy. Ironically, the mind projection fallacy is an identification of a particular type of category error, and I claim that my approach is the one that avoids mind projection fallacies.

How does this differ from the hurricane analogy?

It doesn't, it's just another such analogy taken from physics. The hurricane analogy serves admirably, it is a perfect example of what I mean when I say that scientific ontologies are contextual, provisional, and goal-oriented, and that is also the reason that if we wish to imagine that systems have "properties", we should not use that picture to drive a logical necessity that these properties must determine the behavior of the system. That is actually reverse logic-- the usefulness of properties stems solely from the behaviors of the systems, not the other way around, and the usefulness of the property concept is contextual, provisional, and goal-oriented, but not unique and not logically closed. It should never appear in any proof of anything general, and it should never be viewed as a "mild" assumption, but rather, it is the assumption that colors everything that results from it. Not recognizing the import of what has been assumed is always the source of circular reasoning.

First off to say atoms are real does not entail that they are strictly independent, any more than a real hurricane is independent from the atmosphere, a white dwarf star is not independent of the mass it contains, etc.

True, but if atoms are real, and dependent on other things for that reality, then we must also assert what those other things are or else we cannot coherently talk about what an atom is. Again, the escape from this paradox is simple-- there is no need at all to regard atoms, or hurricanes, as real, so we can talk about them the way we should be talking about them: as concepts and pictures that we evoke for some specific and contextual purpose. That's just exactly what they are, why on Earth should we need to pretend they are something different to be able to call ourselves realists? Why do we need to be unrealistic to count ourselves realists? I say the realist is the person who does not fool themself.

Hence saying we should be able to tell if a white dwarf is a kind of atom is like saying if pool balls are real independent entities we should be able to say if pool balls are a type of triangle because they form a triangle in the raked position.

Yes, that's right, that's the problem with true ontologies! They just don't lead to coherent and internally consistent language, that's why it is a fantasy to imagine that a pool ball is a real thing, and not what it quite demonstrably is: a picture we borrow from some conceptual structure (generally geometrical or mathematical in nature) because it serves various purposes for us to so borrow it. But serving some purposes does not require it serve all purposes, whereas if a pool ball was "really real", then it must serve all purposes. How can something be real but break down in some context? For example, if a pool ball is real, does it have a surface, or doesn't it? Is the pool ball real, but its surface is not real? You can see the dilemmas one gets into if one insists on making the mind projection fallacy that objects that have demonstrable existence only in some conceptual structure also have existence in the "real world."

That is why symmetries take center stage in modern physics. It's the only thing we can both know and is not subject to choice, such as ontological opinions are. It is also what makes theorems, such as PBR, possible and meaningful in constraining possible models or interpretations of QM.

Yet the stated assumptions of PBR are not "let us assume the following symmetry." Instead, their assumption was that systems have properties that determine what happens to the system. Nothing in physics requires this to be true, and nothing in realism requires it either, unless a naive version of both is in use.

Though you are right that we cannot assume a priori determinism determines what happens in the usual sense, neither can we assume it doesn't in spite of contrary opinions.

Nothing in my logic requires that determinism is wrong, just like nothing in the mind projection fallacy requires that what the mind is projecting is wrong. It only requires that it is not known to be right, and thinking it must be right is then the fallacy-- the same fallacy applied by the PBR assumptions.

How we codify causal connections in science almost certainly is a construct of how we think. Yet the symmetries these causal connections entail are not.

I would label that as a mind projection fantasy-- the idea that we can tell the difference between when our codifications are a construct of how we think, and when they are not. We just don't have that ability, it's logically impossible. Symmetries also come from our mind, they are concepts that demonstrably exist in a mathematical or geometrical structure only. Applying them in the real world is just as contextual, provisional, and goal-oriented as any other scientific ontology, and thinking they are something "more real" than that is a mind projection fallacy.

If one model gives property set A and another equally valid model gives property set B, then set A can be mapped onto set B and visa versa, else the two models would not be equally valid.

I agree with that but I'm not sure I see the relevance-- models are always going to invoke properties, that's just what they do. But the models never cause reality to do what the model does, so there is never any reason to imagine that the reality involves "hidden variables" that are not in the model. If the properties are not in the model, they are not "hidden", they are simply nonexistent for that model (and reality never has them). We can imagine some other model that does use those properties, but we cannot say those properties caused the system in question to behave the way it did, no model can claim to involve a "complete set of properties" the way the PBR proof invokes (unless "completeness" is defined in the provisional sense of "sufficient to get the predictions of the theory", but all theories do that, the properties are then just the states).

Let me say it like this: if one believes that ontic elements actually underpin a theory that does not refer to them, then one must hold that any statistical interpretation of the states of the theory must be built from ensembles of those ontic elements. But if the theory does not actually construct its states that way, it would be quite a coincidence if it could be interpreted that way. The key point is, wave functions can still be viewed as epistemic (as I do) if one simply asserts the very realist attitude that the epistemic states of any theory are always going to be the same as the ontic states of that theory (because the latter doesn't really exist independently of the former, there is no such thing as ontic states of a theory that could ever be distinguished from the epistemic states of that theory). No properties, no proof.

I think that you appear to be undervaluing the immutability of symmetries on the grounds that these symmetries can be contextualized in a myriad of different ways. In it's simplest form the true reality that some people chase is equivalent to arguing over whether the car was doing 70 mph or the ground was doing 70 mph under it. In more complex circumstances this non-physical coordinate attribute vastly changes the character and even apparent identity of what reality is. Even your "dressed atoms" is simply a regrouping of coordinates such that variable sets are regrouped as fewer sets of different variables.

Absolutely, that's the point-- we must not reify our coordinates, it would be an example of the mind projection fallacy. But that's just the coordinate projection fallacy-- the mind projection fallacy goes much deeper. It must extend to everything the mind is doing, because as soon as we think we can use our mind to tell the difference, we are committing the mind projection fallacy. We cannot have it both ways, which is just what Jaynes appears to do-- if he disagrees with something, it is the mind projection fallacy, but if he agrees with it (like "atoms are real"), then he thinks his mind can tell the difference between when it is projecting and when it isn't. I cannot imagine how he thinks he can navigate that core logical inconsistency.

 

[Ken G]

Well, you tell me. The fact is that this is exactly what you do, from the thread "Quantum Eraser and Its Implications":

Well, that might be what your incorrect interpretation of my statements is doing, but it is certainly not what I did. I don't understand why you can't get this: when we perceive an outcome to an experiment, to label that as a "nonunitary outcome", we must apply the concept of unitarity. This is an ontological entity borrowed entirely from a conceptual framework (the mathematics of linear maps of the Hilbert space, with whatever mathematical detail one wishes to get into). What I am saying is the thing that borrows ontological elements from mathematical frameworks is called the conscious intelligence of the human mind. I hardly find that controversial, yet somehow you cannot seem to admit this basic fact to yourself. I am left to wonder why you find it so important to block that knowledge, I usually associate that reaction with less scientific circles, but I guess it goes to show that scientists are humans too.

 

[my_wan]

How can you tell in which cases we are working with a "useful fantasy" about the reality and which cases we are working with the actual reality? To even make this language internally inconsistent, we must accept that even fantasies have a sliding scale of connection to reality, which is just what I mean by "usefulness", but never cross a line into being something fundamentally different from a fantasy-- all that demonstrably changes is the usefulness of the fantasy.

We can only clarify the empirical data such that more of our "useful fantasies" are known to be so. So yes, they do have a sliding scale. The scale just doesn't and never will go far enough to prove what reality is. Even a seemingly perfect unification theory or TOE can't do that. I'll get to what your missing wrt immutable facts shortly.

Indeed, and this is the central point. I'm not trying to divert this thread into a discussion of my personal philosophical opinions, this issue is right at the heart of just exactly what it is that PBR has proved about valid interpretations of quantum mechanics. PBR have adopted a very narrow view of what realism is, too narrow to be able to claim that they are using "only mild assumptions." Their version of realism is indeed often adopted by scientists, but I claim that it is internally inconsistent with science.

So what if it did take a narrow view? That just means it was successful in putting constraints on what is and isn't, within that narrow view, valid interpretations and extended modeling attempts of QM. Yet within that narrow view it did succeed in placing those constraints, i.e, established a symmetry that all future models, ontic or epistemic, must deal with. Even if it becomes moot in a deeper theory it must still deal with it in the domain in which it was defined.

And I would say the simple path that avoids any such incongruences is simply recognizing that any ontological statements we choose to make, whether they be about hurricanes or atoms or any physical "properties" of our world, are all going to be effective and useful pictures that we are choosing to borrow from conceptual structures like mathematics or everyday experience, and have no separate "existence" in the real world-- they exist only in the conceptual structures that we borrow them from. Same for properties-- so we can use properties within the context that they serve us, but we cannot prove things from using them, we cannot let a picture drive our logic that tells us what kinds of interpretations of quantum mechanics are possible, unless we allow that our proof only applies to those who would enter into our picture, and make our "mild" assumptions.

What you seem to miss is the fact that once a valid conceptual structure is established then any deeper model that uses an entirely different conceptual structure must still either conform to those symmetries within the domain they were supplied or demonstrate where they are wrong. Yes, same for properties. If theory A uses property set A and a deeper theory B uses property set B then theory B must provide for property set A within the domain of theory A. Exactly because valid symmetries are immutable, unlike to the conceptual structures you seem to think everybody is stuck on.

The issue here is, which should we regard as the "null hypothesis": that the ontic entities we create in our language about reality really are the foundational basis of the universe, or that they really are only what we can demonstrate them to be (ideas we create in our language and our mathematical theories, which are then transplanted from the conceptual structures in which they demonstrably exist and used in physical contexts where they do not demonstrably exist).

All I am saying is this: the true realist must adopt the latter, not the former, as their null hypothesis, because to do otherwise is a basic category error.

So a true realist must adopt the null hypothesis that nothing real exist. Well, I guess you already know what a true Scotsman must adopt don't you.

It is fully realistic to notice category errors, that's not a mind projection fallacy. Ironically, the mind projection fallacy is an identification of a particular type of category error, and I claim that my approach is the one that avoids mind projection fallacies.

So if we adopt this null hypothesis then there is really no point in defining no-go theorems, it is settled. Only then we wouldn't have constraints, that may be mooted but will never go away in any theoretical structure, as theoretical tools for deriving a more "useful fantasy". Whatever category error you think may be involved in fact produced constraints on any model, ontic or epistemic, that is very useful to theorist. The null hypothesis is that we don't know, but we'll push every possibility to see where anyone of them breaks. Taken your form of the null hypothesis involves invalidating possibly extremely valuable theoretical constructs.

It doesn't, it's just another such analogy taken from physics. The hurricane analogy serves admirably, it is a perfect example of what I mean when I say that scientific ontologies are contextual, provisional, and goal-oriented, and that is also the reason that if we wish to imagine that systems have "properties", we should not use that picture to drive a logical necessity that these properties must determine the behavior of the system.

So how we contextualize the description a hurricane changes something about what the hurricanes properties? So let's make them go away, just define them out of existence. More seriously, your null hypothesis does in fact properly define some very serious limits on science. But you are over generalizing the consequence of those limits. So much so that you are effectively ruling out a priori some potentially "useful fantasies" of immense power and usefulness. All the scientist i know are well aware of the limits you null hypothesis entails. But you appear to be taking it to such extremes, while apparently accusing scientist of making claims with their analogies they are not making.

That is actually reverse logic-- the usefulness of properties stems solely from the behaviors of the systems, not the other way around, and the usefulness of the property concept is contextual, provisional, and goal-oriented, but not unique and not logically closed.

Of course it's not unique. Do you think Susskind actually intended to say there was a airplane propellers around black holes? No. It was to illustrate a symmetry, and a valid symmetry is not provisional. It is ONLY provisional if you think he was really talking about airplane propellers around black holes!

It should never appear in any proof of anything general, and it should never be viewed as a "mild" assumption, but rather, it is the assumption that colors everything that results from it.

So airplane propellers around black holes colors our presumptions about what's around black holes? That's how much sense you make when you limit yourself to the particular context under which a symmetry is defined, such as the PBR theorem. Nor does your claim of what the paper said, or how your claim it is interpreted by scientist, have anything to do with how scientist think about the details of what the paper claimed.

True, but if atoms are real, and dependent on other things for that reality, then we must also assert what those other things are or else we cannot coherently talk about what an atom is.

No. Just as the hurricane analogy illustrated you don't even have to know atoms exist to describe it just as well. Simply use classical thermodynamics instead of statistical mechanics. Oh, by the way, the PBR paper title used the term statistical in the sense it was used in the development of classical thermodynamics, not the sense it was used in developing statistical mechanics. At one time they were thought to be indistinguishable theories differing only in ontologies, until Einstein came along with his paper on Brownian motion. Do you want the whole world to adopt your null hypothesis and forget even thinking Brownian motion, or it's modern equivalent?

Again, the escape from this paradox is simple-- there is no need at all to regard atoms, or hurricanes, as real, so we can talk about them the way we should be talking about them: as concepts and pictures that we evoke for some specific and contextual purpose.

We do. That's exactly why QM doesn't make such ontological claims one way or the other, and contains no contextual model at all that is empirically distinguishable. If we had just one then we could contextualize it any way we want because of how symmetries work. But we don't even have one, outside the math. And here you are telling us we shouldn't even look for one. Einstein shouldn't have looked at Brownian motion by such standards!

Since the limiting truth buried in your over-generalizations are is nearly universal among the scientist I know, with varying degrees of leaning towards those generalizations as their guide, I seeing this debate as moot. But the day science is no longer allowed to look for Brownian motion, which is what PBR symbolically did, due to a universal null hypothesis I wouldn't even call it science anymore. Science by definition ask questions in every possible context, not just those deemed worthy by a philosophical null hypothesis. As long as the debate is moot I see no more reason to continue.

 

[bohm2]

Just to add the newest paper on PBM. The authors also cite Leifer's blog:

Completeness of quantum theory implies that wave functions are physical properties

http://arxiv.org/PS_cache/arxiv/pdf/1111/1111.6597v1.pdf

 

[Ken G]

What you seem to miss is the fact that once a valid conceptual structure is established then any deeper model that uses an entirely different conceptual structure must still either conform to those symmetries within the domain they were supplied or demonstrate where they are wrong.

I'm not missing that, I'm well aware of it. Indeed, it's pretty much what I'm saying--we should always expect our new theories to mostly trash the ontological entities of our old theories, yet also explain why the old theories worked in the domain that they worked. So it has always been, so it will likely always be in physics. So what this means is, don't take the ontological elements of any theory too seriously-- they are ultimately all epistemic, yet somehow we need constant reminding of this, and don't seem to really get it until the next theory does come along.

Yes, same for properties. If theory A uses property set A and a deeper theory B uses property set B then theory B must provide for property set A within the domain of theory A. Exactly because valid symmetries are immutable, unlike to the conceptual structures you seem to think everybody is stuck on.

The problem with what your saying is in the word "immutable." I would simply say that an approximate symmetry is just that-- an approximate symmetry. It might even be quite an accurate approximation in most contexts, but the next theory will always show the context where it is not so accurate. I don't see anything "immutable" there, I just see that good theories remain good theories when better ones come along. So it will be with quantum mechanics-- but there will still never be a theory with a "complete set of properties" that determine what happens. Instead, indeterminacy will be our constant companion, because that's just how science works, and always has-- even when we pretended to ourselves that it was not working that way (as in classical mechanics and the concept of an exact position and momentum).

So a true realist must adopt the null hypothesis that nothing real exist.

No, that would certainly not be realism. Realism, is by definition, the idea that something real does exist. I am a realist. But what I am saying is that saying something real exists, and giving it properties, are two completely different things. What is "realistic" is to recognize that giving reality properties is always going to be useful, contextual, and goal-oriented behavior-- but it's never going to be the truth. That's just not what science has ever done-- it has always borrowed its ontologies from mathematical patterns, that it finds useful to include in some theory or other. What I don't get is, when it is perfectly demonstrably clear that this is what science does, why should we feel we need to pretend we are doing something different?

So if we adopt this null hypothesis then there is really no point in defining no-go theorems, it is settled.

Not so. No-go theorems are fine, but they are only as good as their assumptions. What better example of that was there but von Neumann's no-go hidden variable theorem? It sure didn't stop Bohm, and now we have a host of members on this very forum who are interested in Bohmian hidden variables. So much for no-go theorems! What a no-go theorem actually does is point to the assumptions you need to relax to avoid the theorem, but in the case of PBR, since they adopt the assumption that a complete set of properties determines all outcomes, it's pretty clear what assumption can be dropped for those seeking epistemic interpretations of quantum mechanics.

The null hypothesis is that we don't know, but we'll push every possibility to see where anyone of them breaks. Taken your form of the null hypothesis involves invalidating possibly extremely valuable theoretical constructs.

No it doesn't, nothing I say invalidates even a single theoretical construct. I'm fine with theoretical constructs, I just call them by their true names-- borrowed ontologies from mathematical patterns. I say the construct exists in one place: the realm of mathematics. Again, I'm amazed it is so common for people to reject that and want the constructs to jump over into absolute truths about the real world (like "atoms are real" and so on).

So how we contextualize the description a hurricane changes something about what the hurricanes properties? So let's make them go away, just define them out of existence.

But that's just it-- we don't need to define them out of existence, they never existed in the first place, anywhere except where they are already defined: as conceptual patterns, often mathematical in nature, sometimes merely descriptive-- but never anything but conceptual patterns, that's what I mean by useful fantasies. A hurricane is a useful fantasy, an atom is a useful fantasy. Langauge is labeling the labors of our minds. To claim anything else is nothing other than the mind projection fallacy, Jaynes is hoisted on his own petard.

So much so that you are effectively ruling out a priori some potentially "useful fantasies" of immense power and usefulness.

How is recognizing that something is a useful fantasy "ruling it out"? It's a useful fantasy, that's why we use it. Nothing ruled out at all, just calling it by its true name to avoid fooling ourselves (given that, as Feynman said, we are the easiest ones to fool).

All the scientist i know are well aware of the limits you null hypothesis entails.

Then why are you objecting to it? The fact is, scientists have a very had time with those limits, they treat it as a bitter pill they would rather not swallow. But it isn't so bitter, it's just the truth. PBR assumed that a complete set of properties determines everything that quantum mechanics is trying to describe and predict. Useful fantasies are fine, but you cannot prove things from them.

It was to illustrate a symmetry, and a valid symmetry is not provisional.

Yes it is, in science a valid symmetry is provisional. Everything is provisional, the concept of "valid" is provisional. Symmetries were made to be used, then broken, then used again. It's all provisional, science is the art of manipulating provisions. It always is, this is just constantly seen.

Nor does your claim of what the paper said, or how your claim it is interpreted by scientist, have anything to do with how scientist think about the details of what the paper claimed.

I'm not sure what you are claiming here, so I just have one question: did PBR, or did they not, assume that there is some "complete set of properties" that determine everything that happens to the systems that quantum mechanics is trying to predict and understand? Did they, or did they not, make this assumption about how the systems could behave, above and beyond how the quantum mechanical state treats their behavior, in order to learn something about how to interpret those states?

Do you want the whole world to adopt your null hypothesis and forget even thinking Brownian motion, or it's modern equivalent?

I don't understand what your asking, nothing in my null hypothesis requires ignoring the useful fantasy of the causes of Brownian motion that are invoked in any particular theory. Is it possible you think I'm advocating that science stop participating in useful fantasies? No, I never said it should do that, that has been the stuff of scientific progress for thousands of years. What I am saying is that we should stop pretending that we have been doing something else. You tend to agree with me, then turn around and say I'm wrong! Perhaps you are simply misinterpreting what I'm saying to make it wrong?

We do. That's exactly why QM doesn't make such ontological claims one way or the other, and contains no contextual model at all that is empirically distinguishable.

This is what I mean-- you are agreeing with me. Then you say my approach doesn't allow Einstein to try to explain Brownian motion? That doesn't make any sense, it is perfectly correct for good science to look for useful fantasies. What is wrong is imagining they are absolute truths instead-- like "atoms are real." Mind projection fallacies.

 

[Ken G]

Just to add the newest paper on PBM. The authors also cite Leifer's blog:

Completeness of quantum theory implies that wave functions are physical properties

http://arxiv.org/PS_cache/arxiv/pdf/1111/1111.6597v1.pdf

Here's a quote from that abstract: "...function represents
incomplete (subjective) knowledge about some underlying physical properties. Recently, Pusey et al. [arXiv:1111.3328, 2011] showed that the latter, subjective interpretation would contradict certain physically plausible assumptions, in particular that it is possible to prepare multiple systems such that their (possibly hidden) physical properties are uncorrelated."

There it is folks, clear as a bell: these authors interpret the PBR result as referring to ramifications of physical properties. Who said that any such thing as a physical property even exists? Note they are not talking about just elements of some theory.

 

[Fredrik]

There it is folks, clear as a bell: these authors interpret the PBR result as referring to ramifications of physical properties. Who said that any such thing as a physical property even exists? Note they are not talking about just elements of some theory.

Yes, it's clear that they think of the term "physical property" as a primitive. (The term means the same thing to them as it does to a person who doesn't know mathematics or physics. That's not necessarily a bad thing, but it's something we need to keep in mind when we read the rest of their comments). The end of the article makes this even clearer.

These conclusions were reached under two assumptions, which we argue are necessary. The first is that quantum theory is correct (if this would not hold, the question of whether the quantum state is a physical property does not make sense)​

A similar interpretation of the mathematical part of the PBR article would say that if QM is correct, and the probabilities of measurement results are determined by physical properties (i.e. the ontic state in the ontological model represents physical properties), then state vectors are physical properties. (I would still say that this is an interpretation of the PBR result, not the actual result).

I haven't studied the details of Colbeck & Renner's arguments, but I looked at the article they keep referencing all the time (link) because they're using the result they found there. Maybe it's just me failing to understand what they're doing, but the claim in that article looks extremely trivial to me. They assume that the probability assignments of QM are correct, and then argue that there can't exist any additional information (in addition to the quantum state) "that is useful to predict the outcome". I don't really see how the assumption is different from what they're trying to prove.

I find it really weird to assume that QM is correct. There are infinitely many quantum theories, but we seem to be talking about just one of them. So now we're assuming that there's an ontological model for that theory, and that the ontic states in that ontological model represent physical properties. These are some really huge assumptions. Not entirely implausible, but still huge.

 

[Len M]

No, that would certainly not be realism. Realism, is by definition, the idea that something real does exist. I am a realist. But what I am saying is that saying something real exists, and giving it properties, are two completely different things. What is "realistic" is to recognize that giving reality properties is always going to be useful, contextual, and goal-oriented behavior-- but it's never going to be the truth. That's just not what science has ever done-- it has always borrowed its ontologies from mathematical patterns, that it finds useful to include in some theory or other. What I don't get is, when it is perfectly demonstrably clear that this is what science does, why should we feel we need to pretend we are doing something different?

I’m not wishing to detract from the theme of the thread, or invoke a side discussion into the philosophical definition of realism, so strictly just for my interest only, a clarification of the kind realism that you invoke would be of interest to me.

I think of the strict definition of realism in a philosophical sense as consisting of two parts:

1. A notion of “reality” conceived of as totally independent of our possible means of knowing it, along with the hypothesis that we do have access to the said reality, at least in the sense that we can say something “true” about it.

We can not prove the hypothesis in the way that we empirically verify scientific models, so the “true” element of that statement is a philosophical statement, in the sense that it may be correct or it may not be – we will never know, all we can do is to believe in it, in the sense of having a "faith" that we can say something "true" without ever knowing that to be the case.

2. A representation of mind independent reality worked out from the phenomena, i.e. from human experience. This representation, in science, is constructed without any need to include mind independent realty as a necessary ingredient in this process of representation.

The representation is used to impart the something “true” about mind independent reality, but the “true” element is a philosophical statement, again in the sense that it may be correct or it may not be – we will never know.

So a realist (of any of the usual flavours) to my mind would, firstly admit that the notion is a philosophical one, but secondly “believe” that the notion is correct, though it can’t be proven.

Now you seem to be saying that one can be a realist without adopting a “belief” that the said realist can say something "true" about mind independent reality.

I’m just, how shall I say, uneasy over your definition. I’m not saying its wrong; it just seems different to how I understand realism. As best as I can infer, you would say that the properties of physics are a useful means in which to do physics rather than implying that those properties are a “true” (“true” in the sense in which I would expect a philosophically aware realist to use the term) representation of mind independent reality. I would say that you make no reference at all to mind independent reality in terms of these properties – you don’t see it as any issue.

Now actually I agree with that, but I would never think of myself as a realist, I would say I am much closer to idealism. I do believe (strongly) that there “exists” a mind independent reality, but equally strongly, I can’t see how we are ever going to penetrate this reality through science. So whilst I consider that I adopt a stance of idealism, it is not radical idealism, I do actually consider that our reality “emerges” (and I use the word "emerge" here in no way to impart any kind of familiar usage, I just can't think of any other way to say it) in some manner from mind independent reality and that that "emergence" gives rise (in an undefined manner) to the consistencies inherent within our reality, but I have no realist “belief” that we can say something “true” about that mind independent reality (or the "emergence" to our reality) using science. I don’t think there is any justification to believe that what exists outside of our reality is of a form that we would recognise in any manner, thus I can't take on board the "belief" that the realist has in thinking that we can say something true about mind independent reality in terms of science.

So I have to say, that I can’t help thinking that actually you are much closer to idealism than realism - you seem to have no "belief" that science can say anything "true" ("true" in the sense of how I would expect a philosophically aware realist to use that word) about mind independent reality. I understand (I think) what you mean when you assert you are a realist, I’m just not sure that label conforms with my understanding of what it means to be a philosophically aware realist. I know this is just abouit definitions and not substance - but I am interested how and why you may differ over my understanding of realism as it is defined in terms of philosophy.

 

[Ken G]

They assume that the probability assignments of QM are correct, and then argue that there can't exist any additional information (in addition to the quantum state) "that is useful to predict the outcome". I don't really see how the assumption is different from what they're trying to prove.

I don't either. It shouldn't matter if QM is correct, that would be a far more stringent assumption than any PBR made. And it does sound even more circular. I'm generally not very enamored with no-go theorems in physics, the hidden assumption problem seems severe. Proofs in mathematics make sense, so if one wants to prove something within the mathematical structure that the physics borrows from, that's fine, but interpretations of the physics seem to have left that realm, and so the proper assumptions to make are much trickier.

 

[bohm2]

So I have to say, that I can’t help thinking that actually you are much closer to idealism than realism - you seem to have no "belief" that science can say anything "true" ("true" in the sense of how I would expect a philosophically aware realist to use that word) about mind independent reality. I understand (I think) what you mean when you assert you are a realist, I’m just not sure that label conforms with my understanding of what it means to be a philosophically aware realist. I know this is just abouit definitions and not substance - but I am interested how and why you may differ over my understanding of realism as it is defined in terms of philosophy.

I actually thought that KenG's position sounded very Kantian as opposed to idealism but I'm not sure? I think the only philosopher/mathematician who strongly felt that we can get "access" to the class of "true" theories (or pretty close) in some of his writings was Pierce:

In this way, general considerations concerning the universe, strictly philosophical considerations, all but demonstrate that if the universe conforms, with any approach to accuracy, to certain highly pervasive laws, and if man's mind has been developed under the influence of those laws, it is to be expected that he should have a natural light, or light of nature, or instinctive insight, or genius, tending to make him guess those laws aright, or nearly aright...This would be impossible unless the ideas that are naturally predominant in their minds was true...The history of science, especially the early history of modern science, on which I had the honor of giving some lectures in this hall some years ago, completes the proof of showing how few were the guesses that men surpassing genius had to make before they rightly guessed the laws of nature...

He repeats this when he writes:

nature fecundates the mind of man with ideas which when those ideas grow up, will resemble their father, Nature

Unfortunately, this idea has been criticized (quite convincingly, I think) by some well-known cognitive scientists/linguists.

 

[Ken G]

I think of the strict definition of realism in a philosophical sense as consisting of two parts:

1. A notion of “reality” conceived of as totally independent of our possible means of knowing it, along with the hypothesis that we do have access to the said reality, at least in the sense that we can say something “true” about it.

The first part of that is clearly realism. The second part is going too far-- it is asserting something about our relationship with what is real, but how can a true realist make an assertion like that? The true realist must accept reality completely at face value, with no preconditions at all. So I do not precondition realism with the caveat that we must be able to say something "true" about it, largely because that requires a definition of "true" that would go beyond simple realism.

Realism is an ontological stance, but characterizing what we mean by "something true" is an epistemological stance. But I don't think this is a fundamental problem, we can adopt some epistemology, like logical positivism, and call that tantamount to doing science, and then marry the epistemology with the realism and get something we might call "scientific realism" (or just logical positivism, it's more or less the same thing). The key point is, we have now gone beyond claims about what is real, and entered into a particular mode of inquiry about what is real-- leaving behind any and all "real" things that don't fit into our epistemological program.

We can not prove the hypothesis in the way that we empirically verify scientific models, so the “true” element of that statement is a philosophical statement, in the sense that it may be correct or it may not be – we will never know, all we can do is to believe in it, in the sense of having a "faith" that we can say something "true" without ever knowing that to be the case.

It seems to me that the words "faith" and the words "truth" are having a little fight in that statement, because we are trying to hold to scientific epistemology here. Outside of science, it is fine to have faith in truth, but science is all about not having faith in truth, it is all about doubting and poking and testing and questioning whatever is regarded as true. Thus I would say a "scientific truth" is like a big bullseye with a sign "give it your best shot." There's no denial of the usefulness of the provisional truth represented there, if it were not useful then science would not be useful. But there isn't much need for faith in it-- the usefulness is demonstrable, the rest is to be doubted and attacked.

2. A representation of mind independent reality worked out from the phenomena, i.e. from human experience. This representation, in science, is constructed without any need to include mind independent realty as a necessary ingredient in this process of representation.

I agree that's a necessary ingredient of doing science, but I don't think it needs to be associated with realism. Even an idealist would wish to create such representations, and a realist who rejects the value of science might not see any value in these representations. But realism is certainly consistent with doing science, and in practice all scientists I know are also realists.

The representation is used to impart the something “true” about mind independent reality, but the “true” element is a philosophical statement, again in the sense that it may be correct or it may not be – we will never know.

To me, that version of "truth" doesn't mean anything other than "usefulness." So I don't even use the word "true", just "useful." This leaves open the question "but why is it useful", but to me that's a fine question to leave open-- it's certainly not an improvement to say "it works because it's true, and the reason I claim it's true is that it works."

So a realist (of any of the usual flavours) to my mind would, firstly admit that the notion is a philosophical one, but secondly “believe” that the notion is correct, though it can’t be proven.

Yes, but here the "notion" is that there is something real, it does not include any of the aspects that we are attributing to reality. Attributing aspects to reality is a provisional, contextual, and goal-oriented process, all part of the "representations" but not part of the "reality." The map is not the territory.

Now you seem to be saying that one can be a realist without adopting a “belief” that the said realist can say something "true" about mind independent reality.

Correct, because the word "true" in that sentence does not mean anything demonstrably more than "useful" or "expedient." So given that, we should just say "one cannot be a scientist without adopting the belief that the realist can say something useful or expedient about mind independent reality," and note that this is actually not a "belief", it is pretty demonstrably correct (cures to disease, use of technology, etc.).

I’m just, how shall I say, uneasy over your definition. I’m not saying its wrong; it just seems different to how I understand realism. As best as I can infer, you would say that the properties of physics are a useful means in which to do physics rather than implying that those properties are a “true” (“true” in the sense in which I would expect a philosophically aware realist to use the term) representation of mind independent reality.

Right. Your use of what a realist would regard as true sounds an awful lot like what Jaynes called the mind projection fallacy.

I would say that you make no reference at all to mind independent reality in terms of these properties – you don’t see it as any issue.

Yes, I see the use of properties as having nothing to do with realism. An idealist could make just as good use of the concept of properties as a realist could, indeed the idealist is the one who needn't fear the mind projection fallacy, because it isn't a fallacy for them.

Now actually I agree with that, but I would never think of myself as a realist, I would say I am much closer to idealism. I do believe (strongly) that there “exists” a mind independent reality, but equally strongly, I can’t see how we are ever going to penetrate this reality through science.

It depends on what you mean by "penetratre". I think that as soon as you say you believe (strongly) in mind independent reality, you are not an idealist, you are a realist. To say you don't think we can "penetrate" that reality doesn't make you not a realist if by "penetrate" you mean "understand the actual truth of." If you just mean "gain useful conceptual understanding and practical power over", then we clearly do "penetrate" that reality to some degree using science.

So whilst I consider that I adopt a stance of idealism, it is not radical idealism, I do actually consider that our reality “emerges” (and I use the word "emerge" here in no way to impart any kind of familiar usage, I just can't think of any other way to say it) in some manner from mind independent reality and that that "emergence" gives rise (in an undefined manner) to the consistencies inherent within our reality, but I have no realist “belief” that we can say something “true” about that mind independent reality (or the "emergence" to our reality) using science.

Then what I am saying is, you are the actual realist here, and those who claim that science can say something absolutely true about reality (not provisionally true, not effectively true, not borrowed from some formal pattern or mathematical structure in which that element actually has its existence), are not realists because their position is fundamentally logically inconsistent. They are committing the mind projection fallacy, which is only a fallacy for realists! So ironically, their position is only internally consistent if they are idealists (and only if they drop the "mind independent" part).

I don’t think there is any justification to believe that what exists outside of our reality is of a form that we would recognise in any manner, thus I can't take on board the "belief" that the realist has in thinking that we can say something true about mind independent reality in terms of science.

I agree, that's why such self-styled "realists" are not being very realistic.

So I have to say, that I can’t help thinking that actually you are much closer to idealism than realism - you seem to have no "belief" that science can say anything "true" ("true" in the sense of how I would expect a philosophically aware realist to use that word) about mind independent reality.

To summarize, I claim that what makes my stance consistent with realism is that we need to substitute the words "useful and expedient" where you have "true", and if we do that, I not only do have that "belief", I claim it is not a belief at all-- it is fully substantiated by fact.

 

[Ken G]

I actually thought that KenG's position sounded very Kantian as opposed to idealism but I'm not sure? I think the only philosopher/mathematician who strongly felt that we can get "access" to the class of "true" theories (or pretty close) in some of his writings was Pierce:

Yes, I think that's accurate, and I agree with the critics of Pierce. I don't think the arguments "it has to be true or it wouldn't work so well" and "it has to be true or we couldn't have evolved to come up with it" just don't hold any traction. We know things that aren't really true work very well all the time, and we can't claim that everything our mind does must be true or we couldn't have evolved to do it because our minds are capable of logical gaffes. Finally, we can't say that although many things that work aren't true, and although our minds are capable of complete gibberish, all the same the things that work best must be true, and in and amongst all that gibberish must be the actual truth. I can't see any logical requirement for that argument to hold, it sounds much more like wishful thinking to me.

It should be said that I interpret those remarks by Pierce as just a brand of idle speculation on his part-- he was a consummate logician and he perfectly well understood the role of symbols and metaphors in language, so I don't think he would have seen anything in that argument as logically rigorous. He was trying to address the question, why do physics theories work so well, and for that question his answer is perfectly adequate. However, it is not any kind of answer to the question, "is physics true", because if one holds that only what is true could work, one is making an argument that is not only circular, its assumptions run afoul of millennia of evidence to the contrary.

 

[bohm2]

I just do not understand how there can be so many interpretations of PBR? Here's a FQXi BLOG that just came out:

Let me try to summarise their argument. They suppose a particular kind of PSI-epistemic model is possible and then show a contradiction with quantum statistics. The kind of model they consider is essentially a hidden-variable one. The idea is that at the time of preparation of a quantum system one also sets the value of some hidden variable Lambda...

This is *not* assumed to be local as far as I can tell. Lambda is assumed to determine the probabilities of different outcomes. But, also for the sake of argument, Lambda is assumed not to uniquely determine the quantum state, i.e. the same value of Lambda can be associated with the preparation of several different quantum states. So the argument, modulo potential subtleties like hidden assumptions, puts another nail in the coffin for hidden variable theories, adding to the contributions by Bell and others. As it is quite clean and does not appear to assume the hidden variable is local, one can imagine it turning up in text-books at some point.

A very interesting paper by Colbeck and Renner has just appeared apparently deriving a very similar result from even more minimal assumptions, and I know that at least one more related paper will appear on the arXiv soon. My personal inclination remains to not think of the wave-function as a real object.

Are we getting closer to nailing down what the wavefunction is?
http://www.fqxi.org/community/forum/topic/999

 

[Fredrik]

I just do not understand how there can be so many interpretations of PBR?

I think the main reason is that the PBR article is so badly written. They haven't clearly separated the mathematical stuff from the non-mathematical, and the mathematical theorem isn't clearly stated anywhere in the text. The proof doesn't explain what assumptions they're using when they're using them.

Here's a FQXi BLOG that just came out:

Are we getting closer to nailing down what the wavefunction is?
http://www.fqxi.org/community/forum/topic/999

This guy says that the theorem doesn't assume locality. The assumption that Michael Hall (the guy who wrote the article Demystifier linked to) called "factorisability" looks like a locality assumption to me. On the other hand, Hall says that he can weaken that assumption and still get the same conclusion. I haven't studied the details of Hall's article.

Edit: In my post #155, the factorisability assumption looked like this:

We assume that
Q_{\psi\psi'}(\lambda,\lambda') =Q_\psi(\lambda)Q_{\psi'}(\lambda') for all values of the relevant variables.

 

[Ken G]

What's more, I got the impression that the PBR proof held no sway over deBroglie-Bohm, which is by far the dominant hidden variables theory. Yet this new blog entry seems to take aim directly at deBroglie-Bohm. Why would PBR not directly mention deBroglie-Bohm if they were finding some inconsistency in it? So which is it-- does PBR claim to rule out deBroglie-Bohm, or doesn't it? And if it doesn't, how is that a "nail in the coffin of hidden variables theories"?

 

[Fredrik]

I think it's clear that PBR doesn't rule out de Broglie-Bohm. Harrigan & Spekkens explains that dBB is a ψ-supplemented (and therefore not ψ-epistemic) ontological model for QM. PBR only rules out (local?) ψ-epistemic ontological models.

 

[Ken G]

OK, that's what I thought, but note deBroglie-Bohm is the quintessential nonlocal hidden variables theory that gives the same results as quantum mechanical states. So if that latest blog thinks PBR extends generally to nonlocal hidden variables theories, it would be strange to call that a nail in their coffin when deBroglie-Bohm is alive and kicking. Reports of the demise of hidden variables seem greatly exaggerated! (My own objection to hidden variables theories is that we don't build theories to hide our variables, we build theories that include perfectly apparent variables to explain some observations that previous theories, with their own perfectly apparent variables, don't.)

 

[bohm2]

My head is spinning. Valentini, who is a big-time supporter of deBroglie-Bohmian interpretation seems to be very excited about this theorem. This suggests to me that he feels it rules out some other interpretations as suggested also in the Leifer piece. I'm kind of looking forward to see what the major Bohmian group of Durr/Goldstein/Tumulka/Zanghi have to say about PBR but I haven't come across anything, yet. Either way, I'm totally lost but then again, the experts themselves don't seem to be doing much better?

 

[my_wan]

I'll try again to contextualize these characterizations of what the PBR theorem entails. Consider what Matt Leifer said:

The question is whether a scientific realist can interpret the quantum state as an epistemic state (state of knowledge) or whether it must be an ontic state (state of reality).

This is the defining feature where the propensity is for people to separate epistemic and ontic states into mutually exclusive categories. Here is what Matt Leifer said immediately following the above statement:

It[/PLAIN] seems to show that only the ontic interpretation is viable, but, in my view, this is a bit too quick.

This I hope to justify in a historical context. He then follows that with the statement:

On careful analysis, it does not really rule out any of the positions that are advocated by contemporary researchers in quantum foundations. However, it does answer an important question that was previously open, and confirms an intuition that many of us already held.

Why then is the PBR theorem so important if it fails to rule out any of the positions that are advocated by contemporary researchers? Exactly as Matt said: It formally closes a potential hole that was previously merely assumed to be closed by the researchers in the field. Now it's time to contextualize the epistemic verses ontic characterizations in a historical context, to show why neither the ontic or epistemic positions advocated by modern researchers have not been ruled out.

Historically classical thermodynamics (CT) was developed first and was a purely epistemic construct. It made no reference to any underlying ontic constructs whatsoever. This ignited a debate quiet similar to the ontic verses epistemic debate today. Then over some years statistical mechanics (SM) was developed. Although SM made use of statistics it explicitly defined precisely what bits of mechanistic data were traded in the ensemble procedure. The epistemicists of the time still felt safe. After all the ontologist couldn't prove their atoms existed, they merely had an equivalent theoretical construct. That is until Einstein published his work on Brownian motion, which provided an empirical distinction between CT and SM and proved atoms existed. At least existed as something more than a mathematical fiction, whatever that something was. Ironically it was Einstein's logical positivist approach to relativity that drove the more modern developments, which put ontic based dynamics in the back seat.

The question this historical bit posses is: Did the ontic formalization SM remove the epistemic content of either CT or SM? Absolutely not, in either case. Both such models are explicitly formulated in terms of "states of knowledge", i.e., epistemic. The value and contributions of epistemicists will not go away under any circumstances, but it is not exclusive of the potential value ontologist provide. Such as SM and the empirical consequences provided through Brownian motion. The PBR theorem did not invalidate epistemic models any more than SM invalidated the epistemic content of both SM and CT. It did however open up the possibility of contextualizing QM in terms of variables that are not fundamentally statistical, whether those variables have epistemic or ontic substructures in themselves or not.

Now before anybody tries to make too big a deal out of this analogy to classical physics, it is interesting to note what set QM apart. The notion that QM can be derived from known positions and momentums of parts is completely and irrevocably broke. Will not even waste my time with anybody arguing otherwise. Yet it seems to me that given only what we know from classical physics alone it must be broken, not necessarily that it entails QM. The reason fundamentally harks back to the complaints of Newton's critiques, especially wrt gravity, but also the magic like properties sprinkled on classical particles. With SR we could easily interpret the effects as kinematically induced illusions in an otherwise Newtonian flat spacetime metric. A few paradoxes, if viewed this way along ontic assumptions, notwithstanding. With GR it becomes explicitly dynamic, breaking this kinematic illusion interpretation if ontic assumptions are involved at any level. Any ontic based construct must then also be able to generate differing relativist metrics of space and time. IIf any sort of mechanistic dynamics generates empirical metrics of space and time upon which positions are given empirical meaning, what then can we say about the positions of things at a level below which relativistic positions are even defined or definable? No more than we can say about a position outside the Universe. Hence, given the assumption of any form of ontic substructure, the very foundation of upon which SM rest, the positions and momentum of particles, is ripped out from under classical physics prior to any QM considerations. Yet this position/momentum model is the prototype by which the strangeness of QM is judged. This to me is ironic.

 

[Fredrik]

My head is spinning. Valentini, who is a big-time supporter of deBroglie-Bohmian interpretation seems to be very excited about this theorem. This suggests to me that he feels it rules out some other interpretations as suggested also in the Leifer piece. I'm kind of looking forward to see what the major Bohmian group of Durr/Goldstein/Tumulka/Zanghi have to say about PBR but I haven't come across anything, yet. Either way, I'm totally lost but then again, the experts themselves don't seem to be doing much better?

My head is spinning too, but I'm not looking forward to more opinions and interpretations from the experts. The only thing I would be interested in at this point is a much more rigorous proof of the mathematical part. I don't know how many times I've read the "simplified" argument, and I still don't know what the **** they're talking about. I don't even know what the theorem says. (Not exactly). It looks like the "simplified" argument should prove something like this:

No quantum theory with a 2-dimensional Hilbert space has a ψ-epistemic ontological model such that for some orthonormal basis {|0>,|1>}, the probability distributions of ontic states corresponding to |0> and (|0>+|1>)/√2 are overlapping.​

But my best guess at what the proof is really saying goes like this:

Suppose that the above is false. Define the quantum theory of two non-interacting qubits. Pull an ontological model for it out of a hat. Use an assumption/theorem that looks suspiciously like locality. Yada-yada-yada contradiction.​

I don't know why there would even exist an ontological model for the two-qubit theory. Maybe it can be derived from the ontological model for the single-qubit theory, by arguments similar to the ones in Aerts & Daubechies, but I'm not sure, and in either case, it's a very non-trivial detail. A proof must explain if it's an additional assumption, or if they're just using another theorem there.

The "factorisability" is another interesting issue. It looks like locality to me, but no one seems to call it that.

 

[my_wan]

Here is simplest toy model I can think of to contextualize the PBR results in an ontic construct. Following the procedure outlined by PBR we begin by preparing four systems with four states. These states are prepared such that state 1 never has property 1, state 2 never has property 2, etc. All four can have 3 of the four properties mentioned. Now if \Lambda\neq\Lambda_1 the probability of measuring one of the four properties is certain. Only QM dictates that the outcome will never result in any of the four properties.

In fact, as far as I see, all such no-go theorems are predicated on a first order logic, \Lambda=\Lambda_1, in relating measured variables to onic objects. That's why they are limited to non-contextual assumptions. Let's look at the two logical structures more closely.

First-order logic:
To illustrate visually why, consider a 3 sided dice. The dice 1 is labeled: [1,2,3], dice 2: [1,2,4], dice 3: [1,3,4], and dice 4: [2,3,4]. Hence each dice has a zero probability of landing on one of the four possible numbers. Yet given a random one of the four dice it must land on one of the four numbers. Only QM says, in terms of ψ, it cannot land on any of the four numbers.

Higher-order logic:
So let's try a different classical state variable, temperature. We don't even need four states but we will prepare four systems. Each mixture has equal probability of possessing three of four possible states, zero probability of one unique state (or temperature). Now to randomize these four systems requires mixing them in the measuring process, though they were prepared separately. QM requires that in order to randomize or entangle (not know which state is being measured) they must be mixed like the dice before being measured, irrespective of being prepared separately. If you measure each state separately in a separate measuring device then the QM makes an entirely different prediction. It is now trivial to define four states (temperatures) in which the mixed state can never result in any of the four prepared states. In QM terms the properties are entangled.

This last analogy is why the Bohmian's are so exited. The dice analogy is the naive mechanistic view that Matt Leifer said: "On careful analysis, it does not really rule out any of the positions that are advocated by contemporary researchers in quantum foundations." This includes those assuming ψ has some ontic substructure, like the medium with a temperature state variable, and the purely epistemic constructs.

 

[DevilsAvocado]

... PBR only rules out (local?) ψ-epistemic ontological models.

Nope, any ontological model must be non-local within the standard Bell framework.

 

[DevilsAvocado]

Regarding dBB: Unless the Pilot Wave is ψ-ontological de Bohemians are in trouble (according to Leifer’s own conclusion). Is the Pilot Wave real?

 

[Fredrik]

Nope, any ontological model must be non-local within the standard Bell framework.

I'm not sure that's accurate. I think Bell's theorem only rules out those local ontological models for QM that assign probabilities 0 and 1 to measurement results. I don't think it applies to models that can assign any number in [0,1]. Do you have some other theorem in mind?

Even if your statement is correct, that doesn't automatically mean that the word "local" shouldn't be there (in my statement about what the PBR theorem says). It only means that if it should, then the theorem doesn't prove anything we didn't know already.

 

[DevilsAvocado]

I'm not sure that's accurate. I think Bell's theorem only rules out those local ontological models for QM that assign probabilities 0 and 1 to measurement results. I don't think it applies to models that can assign any number in [0,1]. Do you have some other theorem in mind?

Even if your statement is correct, that doesn't automatically mean that the word "local" shouldn't be there (in my statement about what the PBR theorem says). It only means that if it should, then the theorem doesn't prove anything we didn't know already.

I don’t agree. Any pre-assignment, not matter which form, needs non-locality.

Why!?

Because if the EPRB experiment is done properly A and B should be outside each other’s light cone when the randomly rotating polarizer stops.

You could pre-assign all numbers in the world and still it won’t help, because it’s the relative angle between A and B that is crucial.

 

[Ken G]

IIf any sort of mechanistic dynamics generates empirical metrics of space and time upon which positions are given empirical meaning, what then can we say about the positions of things at a level below which relativistic positions are even defined or definable? No more than we can say about a position outside the Universe. Hence, given the assumption of any form of ontic substructure, the very foundation of upon which SM rest, the positions and momentum of particles, is ripped out from under classical physics prior to any QM considerations. Yet this position/momentum model is the prototype by which the strangeness of QM is judged. This to me is ironic.

I think this places us back into the context where we agree. I have been saying all along that ontic substructures, like the concept of exact position and momentum (often claimed to be an ontic substructure of classical mechanics, but I maintain it was never that at all, just a kind of lazy fiction that makes it easier to talk about classical mechanical predictions but is in no way central to those predictions and certainly was never a tested aspect of the theory), are always provisional and contextual. No theory ever required them, there is no such thing as a theory that is "founded on" such substructures, for the simple reason that all theories have to work in concert with how scientists actually do science. So the irony that you see in calling quantum mechanics "unreal" if it doesn't preserve the single most unrealistic, unnecessary, and undemonstrated element of how classical mechanics actually connects with the performance of physics, is the irony I see in claiming that quantum mechanics "realists" must believe in "a complete set of properties" that determine outcomes. That is a highly unrealistic assumption in my view, so what I have been trying to say is, we should not make the mistake of equating ontological descriptions with realist descriptions, when being realist should mean, above all, recognizing the limitations of ontological language about reality. The only people who can believe that their ontological descriptions are absolute truth about reality must be idealists, which is the opposite of realism. (That is also why I claimed that Brownian motion does not prove that atoms exist, it merely adjudicates in favor of the benefits of borrowing the atomist ontology from the mathematical structures in which atoms actually do exist.)

 

[my_wan]

I'm not sure that's accurate. I think Bell's theorem only rules out those local ontological models for QM that assign probabilities 0 and 1 to measurement results. I don't think it applies to models that can assign any number in [0,1]. Do you have some other theorem in mind?

Even if your statement is correct, that doesn't automatically mean that the word "local" shouldn't be there (in my statement about what the PBR theorem says). It only means that if it should, then the theorem doesn't prove anything we didn't know already.

(My bold)

This is how I see it more or less. More or less the point I was making with first-order verses higher-order logic. The [0,1] or law of the excluded middle models only appear to make sense if you are looking for particles that "own" properties like raisins in pudding. Once you allow two bowls of pudding to mix all bets are off as to which pudding the raisins belong to, or even whether the raisins will stay intact.

 

[Fredrik]

I don’t agree. Any pre-assignment, not matter which form, needs non-locality.

Why!?

Because if the EPRB experiment is done properly A and B should be outside each other’s light cone when the randomly rotating polarizer stops.

You could pre-assign all numbers in the world and still it won’t help, because it’s the relative angle between A and B that is crucial.

OK, that makes sense.