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Thanks for the brief QFT information

Just like, for example, if you read one article by Ayn Rand but have never before heard of philosophy and don't know what any of the central philosophical questions are and how different people have attempted to answer them, it is premature to call yourself an Objectivist (i.e., to endorse Objectivism as true). In that position, you would simply need to learn more before you were in a position to have a position. Or take some random issue from, say, medical science: is some newly proposed procedure for performing some surgical operation better or worse than the older procedure? How the heck should any of us know? We simply don't have the knowledge necessary to take a stand one way or the other.

It's not difficult to guess why this occurs. Someone reads Ayn Rand's philosophy and becomes an Objectivist. He starts telling people about Objectivism, and gets into arguments about its fundamental principles. But he is soon confronted by someone who once read an internet essay about a television program which was discussing a book on quantum physics, which mentioned that Heisenberg's Incompleteness Inequality proves that humans-create-reality/everything-is-subjective/pink-elephants-exist-on-mars. The Objectivist now feels compelled to show this objection is invalid, even though he doesnt have the scientific knowledge to properly address it. So he bases his arguments on the only thing he has available - common sense, guided by philosophical principles. But eventually he stumbles across TEW on the internet - an exciting new theory which claims to eliminate the bizarreness of QM. Since his principle goal is not to learn about quantum physics, but only to dispose of (what he sees) as being a particular objection to Objectivism, he doesnt bother learning the details of TEW (or any other QM interpretation) and starts wielding it like a magic sword in his battle with those who are Waging War Against Reality. Noone on either side has any real idea what they are talking about, and yet another internet argument is born.

If there was a new medical theory which claimed to cure diseases by teleporting bacteria out of the human body, you could bet your last dollar that you'd have people advocating competiting theories which they didnt understand.

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I'm certainly not against people using "common sense, guided by philosophical principles" to reject obviously ridiculous ideas. But there is a difference between rejecting the blatantly stupid (and even telling others that you reject it) and openly proselytizing for a specific theory in the absense of relevant knowledge -- specifically, in the absense of knowledge about the particular issues that distinguish the various alternative theories from one another. To use your example of teleporting bacteria, it is one thing to say "that sounds completely stupid to me and I don't believe it"... quite another to say "that sounds completely stupid to me and, as an alternative, I advocate this other theory that I just read about for 5 minutes on the internet even though I know there are 10 other theories out there too and I don't know anything about those."

You mentioned that some people's motivation to proselytize for TEW is the desire "to dispose of ... a particular objection to Objectivism." I don't consider that a rational motivation (convincing others, I mean). If some random stranger really believes that quantum physics refutes Objectivism, is a brief mention of TEW or anything else really going to change his mind? And what is the point of even trying to change his mind? And on the off chance that the stranger actually knows something about physics, mentioning TEW will have precisely the opposite effect: it will only convince him that Objectivism really is refuted by QM (else why would Objectivists resort to an untenable theory?).

So... I urge people one final time: if you don't know enough physics to be advocating TEW, please just stop advocating it. It's an embarrassment that undermines our shared cause.

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Metaphysics doesn't tell us that perception gives us direct insight into the ultimate constituents or structure of the physical world, or that the ultimate theory of physics must involve 3 spatial dimensions, or that interaction between entities must take place via finite speed propagation of particles or waves, or anything like that.  It says:  what is, is.  And that's about it. 

This is a package deal. While it is certainly true that metaphysics does not tell us that “perception gives us direct insight into the ultimate constituents”, metaphysics does tell us that only the finite exists. There is no such thing as an infinite speed.

Metaphysics says more than “what is, is”. It says contradictions cannot exist. You cannot stretch it to say, “If the only inference from a particular experiment is that something propogates at an infinite speed, then it is what it is, and metaphysics has nothing else to say."

This is really the point I am concerned to make on this thread:  if you don't know enough physics to know, at least in essential terms, how TEW works and how it is supposed to differ from other versions of quantum theory, you are simply not in a position to have an opinion on the theory.  You shouldn't advocate it, and you also shouldn't say it's definitely wrong.
If we should not even say that it is wrong, then why are you going to such an effort to convince us that it is "shameful crackpot junk”?

By the way, why did you drop out of the TEWLIP discussion? And since TEW has been around for years, why are you now coming here to denounce it?

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This is a package deal.  While it is certainly true that metaphysics does not tell us that “perception gives us direct insight into the ultimate constituents”, metaphysics does tell us that only the finite exists.  There is no such thing as an infinite speed.

I agree with you; there is no such speed as "infinity". What made you think I thought there was? Maybe you had an argument like this in mind: if two separated entities affect each other, it is because something flies from one to the other, thus if the effect occurs simultaneously with the cause, the something must fly with infinite speed. Then, since there's no such thing as infinite speed, it follows that "instantaneous action at a distance" is ruled out by metaphysics. But I don't think this argument works. It smuggles in an unproved premise -- namely, that something flies from one to the other.

Metaphysics says more than “what is, is”.  It says contradictions cannot exist.  You cannot stretch it to say, “If the only inference from a particular experiment is that something propogates at an infinite speed, then it is what it is, and metaphysics has nothing else to say."
I don't disagree with you. I disagree with the people who claim that what I advocate is tantamount to "something propagates at an infinite speed"!

If we should not even say that it is wrong, then why are you going to such an effort to convince us that it is "shameful crackpot junk”?

That's a fair question. I'm not really trying to convince anyone here that TEW is false. I'm just making my "expert opinion" more widely known, so that those people who don't have any firsthand knowledge (and hence must rely on the opinions of others) aren't fooled into thinking that TEW has widespread support among Objectivist experts. This relates to your next question...

By the way, why did you drop out of the TEWLIP discussion?  And since TEW has been around for years, why are you now coming here to denounce it?

I was kicked off TEWLIP (for pointing out the flaws in one of Little's attempts to explain these experiments, and some subsequent name-calling). I have also been kicked off of Speicher's "Forum" website, where I attempted to post something explaining what was wrong with TEW. Other knowledgeable Objectivists (e.g., Eric Dennis) have suffered the same fate. The way things stand now, any forum where discussion of TEW takes place has been systematically cleansed of dissenters. Hence, the only discussion that exists is highly biased; I worry that this leads non-experts to the false view that there are no dissenters, which hopefully explains my recent posts here.

The one exception I know of to what I said in the previous paragraph is HBL. There was an exchange about TEW there a few months ago. And I think the outcomes there (especially combined with the "cleansing" mentioned above) speak for themselves. The TEW supporters have no answers to the criticisms, and have rather systematically retreated to a small dark corner where they talk amongst themselves and ensnare innocent victims.

I hope some of my comments here will help people at least understand the lay of the land before they unwittingly support something bad.

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Speaking of rationalism...

This is *not* the reason why TEW is wrong.  It is entirely possible to "force the classical notion of a particle into the quantum world" -- as proved a long time ago by de Broglie and Bohm.  Anyone who thinks that this is the fundamental flaw in TEW, does not understand quantum mechanics (and is obviously ignorant of Bohmian Mechanics) and certainly does not sufficiently understand TEW either. 

While it is true that I have not read up on bohmian mechanics, I am not ignorant of TEW or quantum mechanics (I have taken three classes on QM and have read all I care to of Little's work). I just find it totally ridiculuous that people cling desparately to the notion of a particle as a little dot in space. I just want to know why one needs to make this assumption when the results of so many experiments seem to contradict it. :)

In another note, having an opinion does not make one a crackpot. Whether or not you choose to think about what I am saying, dont think you have this problem solved, or insult others who are trying to form a hypothesis.

With that said, I agree that it is important to consider the source of a comment on an internet forum. Experts are few and far between, and listening to a poseur will make one into an idiot. I also agree that it does no good to anyone to go spouting off about things you only have a vague knowledge of.

Edited by Cake
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[...] I just find it totally ridiculuous that people cling desparately to the notion of a particle as a little dot in space.  I just want to know why one needs to make this assumption when the results of so many experiments seem to contradict it. :)

In another note, having an opinion does not make one a crackpot.  Whether or not you choose to think about what I am saying, dont think you have this problem solved, or insult others who are trying to form a hypothesis.

I'm sorry, I think I misinterpreted your earlier comment. I thought you were objecting to treating particles as *points* (on the grounds that points are infinitely small and hence metaphysically impossible... or some such). But you're not objecting to particles as points (as opposed to tiny but finite sized lumps), right? You're objecting to particles as opposed to waves or something else that is spread out a *lot*.

I still think that's a poor objection to TEW, but it isn't the rationalistic one I criticized you for, so I apologize.

Now, re: particles vs. waves, what experiments do you have in mind that contradict the "notion of a particle as a little dot in space"? I find Bell's comment about the two slit experiment completely compelling:

"Is it not clear from the smallness of the scintillation on the screen that we have to do with a particle? And is it not clear, from the diffraction and interference patterns, that the motion of the particle is directed by a wave? DeBroglie showed in detail how the motion of a particle, passing through just one of two holes in the screen, could be influenced by waves propagating through both holes. And so influenced that the particle does not go where the waves cancel out, but is attracted to where they cooperate. This idea seems to me so natural and simple, to resolve the wave-particle dilemma in such a clear and ordinary way, that it is a great mystery to me that it was so completely ignored."

He is, of course, referring to Bohmian Mechanics, which de Broglie actually more or less discovered in 1927, but then subsequently rejected when he couldn't answer some objections that Pauli raised.

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BTW, I don't know what point you were trying to make with a distinction between theory and law.  Whatever you want to call it, TEW is just wrong, and the people who continue to advocate it do this out of negligent ignorance (or worse).

Let us define our terms:

scientific law - a phenomenon of nature that has been proven to invariably occur whenever certain conditions exist or are met

theory - An assumption based on limited information or knowledge; a conjecture.

Do you see the difference? TEW may need revision, but not necessarily abandonment.

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Do you see the difference?

These aren't the way scientists use these terms. The atomic theory of matter, for example, is not a mere conjecture or a mere possibility. But there's no point arguing about mere terminology.

TEW may need revision, but not necessarily abandonment.

The only "revision" that would save it would be to turn it into Bohmian Mechanics.

...i.e., it should be abandoned in favor of Bohmian Mechanics.

Edited by Free Thinker
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Now, re: particles vs. waves, what experiments do you have in mind that contradict the "notion of a particle as a little dot in space"?  I find Bell's comment about the two slit experiment completely compelling:

I think bell's response to the double slit experiment is well thought out and is a valid explanation of the interference pattern that is seen. What I have a difficult time with is why a theory of elementary particles must first begin by assuming that particles are little dots. It seems unnecessary and slightly rationalistic.

I believe that the entanglement issue is the real trouble for a theory that makes the "little dot" assumption. I think bohm tried to resolve the touble by explicitly placing non-local terms in his equation (correct me if i am wrong). It seems funny to make such a claim.

What i think is ridiculous is the mystical interpretation that is given to current QM. It seems to me that the posulate that fundamental particles act as waves does not necessarily imply that they do not have definite properties.

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I think bell's response to the double slit experiment is well thought out and is a valid explanation of the interference pattern that is seen.

I think Bell's point is that it's the most obvious way of making sense of the observed pattern. That doesn't mean it's the only way, and it doesn't prove that this ontology is correct, but it's surely a motivation to look for a more comprehensive theory that is based on this wave-guided-by-particle ontology. That such a theory exists and works, but is hardly known by physicists, is (on the face of it) an inexplicable mystery. Of course we know the explanation is that the founders of quantum theory were *looking* for something that was anti-common-sense and anti-realism.

What I have a difficult time with is why a theory of elementary particles must first begin by assuming that particles are little dots.  It seems unnecessary and slightly rationalistic.
I don't get what bothers you about "little dots." The evidence that particles are really particles (i.e., little "dots" of stuff that stay little as they move around) is "the smallness of the scintillation on the screen" (from Bell's quote)... and all the other countless bits of empirical evidence that particles really are particles. I don't think anyone wants to "first begin by assuming" that there exist particles; people think the constituents of atoms are particles because of actual empirical evidence. So i don't see what you think is rationalistic.

I believe that the entanglement issue is the real trouble for a theory that makes the "little dot" assumption.  I think bohm tried to resolve the touble by explicitly placing non-local terms in his equation (correct me if i am wrong).  It seems funny to make such a claim.

A couple points here. First, entanglement is no more a problem for a particle or particle-guided-by-wave theory, than it is for (say) a pure-wave theory. All "entanglement" means is that two spatially separated systems aren't physically independent -- the separated parts retain some kind of interaction despite the separation. So in a particle theory you just need the particles to interact. There's really no big "problem" there unless you are worried about the fact that the interaction will violate relativity's prohibition on superluminal causation -- that's a valid worry, but my point is that you'd have to worry about that same issue with a pure-wave theory too. Experimental violations of Bell's Inequality prove that nature violates Bell Locality -- i.e., that there is some kind of relativity-violating superluminal causation. It's not like you can avoid this by dropping the "little dot assumption."

Second, it's true that there are non-local terms in Bohm's equation -- specifically, the trajectory of a given particle can be influenced by the goings-on at the location of a distant particle to which the first is entangled. That is, Bohm's theory has explicit non-local action at a distance. It's right there in the equations for all to see. But it's misleading to say that "bohm tried to resolve the trouble by" including this effect. This gets the history just backwards. In retrospect, Bohm did basically the obvious thing -- his equations are the obvious equations to supplement Schroedinger's equation with if you want to try to have a particles-guided-by-wave ontology. So he just wrote down those equations and then proved that the theory reproduces all the predictions of orthodox QM. Now, one of the reasons his theory wasn't taken very seriously was that it was explicitly nonlocal. People's attitude was "OK, so you found a hidden variable theory, but it violates relativity so it can't be right and we can all just ignore it." (This is a completely unjustified position since orthodox QM is *also* explicitly non-local, and it's too generous to the culture to say that people ignored Bohm's theory for this reason; mostly it was ignored for *no* reason -- i.e., it was just ignored; after all, it had been proved that a theory like Bohm's couldn't exist...)

Bell was one of the first people to recognize the importance of what Bohm had done -- namely, constructed an actual *counterexample* to the "no hidden variable theory" proof that had been given by von Neumann. Bell's first paper on the foundations of QM is a probing analysis of von Neumann's old proof, which shows where that proof went wrong. (Bell wrote later that von Neumann's assumptions in that proof were not just false, but foolish -- and he had a very low opinion of the mentality of people who had taken it seriously.) So at this point Bell was very interested in the question: would it be possible to have a theory like Bohm's (in the sense of providing a clear, common-sense, realistic ontology for QM while reproducing all the correct predictions of the orthodox theory) but which respected relativistic causality? In a short time he was able to prove that it wasn't possible -- that theories respecting "Bell Locality" could never be made to agree with the predictions of QM.

So it isn't that Bohm "fixed up" his equations to get them in line with the non-locality that Bell proved is really there. Rather, Bell discovered that the non-locality is really there precisely by trying to get rid of the non-locality that was present from day 1 in Bohm's theory (and eventually proving it couldn't be gotten rid of).

What i think is ridiculous is the mystical interpretation that is given to current QM.  It seems to me that the posulate that fundamental particles act as waves does not necessarily imply that they do not have definite properties.

I agree on both points. Mysticism is no good. And there is nothing inherently bad about a pure-wave interpretation of QM. Just because something we used to call a "particle" turns out really not to be a particle, doesn't mean the thing violates the law of identity or whatever. It just means we were wrong about its nature. So you could never veto a theory merely because it said that "fundamental paticles" are really waves.

But there are several other reasons for rejecting this picture. By the way, this was precisely the picture Schroedinger originally had in mind when he discovered what we now call Sch's equation. He wanted to think of the wave function as describing the density of a really-smeared-out electron "blob". But that turns out to be untenable for technical reasons -- in particular, the equations say that the blobs should spread out significantly and quickly, yet we always see electrons at definite places (like in the 2 slit experiment), never smeared out over a finite region.

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I don't get what bothers you about "little dots."  The evidence that particles are really particles (i.e., little "dots" of stuff that stay little as they move around) is "the smallness of the scintillation on the screen" (from Bell's quote)...  and all the other countless bits of empirical evidence that particles really are particles. 

The "little dot" assumption requires that we postulate some other entity, namely some kind of quantum wave that governs particle motion. If one takes sort of an Occam's razor approach, then they have to go about finding some more logical interpretation of QM. This is obviously a rationalistic device, but in science simpler ususally is better.

One other (admittledly silly) question still arises in my mind. What is the shape of an elementary particle? Such a kindergarten question does nothing to refute a little dot theory, but it is answered by regular QM.

All "entanglement" means is that two spatially separated systems aren't physically independent -- the separated parts retain some kind of interaction despite the separation.  ...  There's really no big "problem" there unless you are worried about the fact that the interaction will violate relativity's prohibition on superluminal causation -- that's a valid worry, but my point is that you'd have to worry about that same issue with a pure-wave theory too.

Im not sure that is entirely correct. Such superluminal causation seems to be something that is a result of assuming a finite and definite end to a particle. In a pure wave theory one could say that the particles are still "touching" no matter where they are. I would argue that such infinitesmal wavefunction overlap can be neglected in almost every case, with entanglement being a prime counterexample.

Second, it's true that there are non-local terms in Bohm's equation

Thanks for the history. I have heard about the aharonov-bohm effect, and found to be a pretty compelling argument for pure-wave theory (much to my chagrin at the time as I had come up with a little dot theory of my own due to my dissatisfaction with QM).

He [schrodinger] wanted to think of the wave function as describing the density of a really-smeared-out electron "blob".  But that turns out to be untenable for technical reasons -- in particular, the equations say that the blobs should spread out significantly and quickly, yet we always see electrons at definite places (like in the 2 slit experiment), never smeared out over a finite region.

Im still not entirely convinced that understaning a wavefunction as a description of an electron "blob" is untenable. I know that things like phase differences and imaginary wavefunction components complicate this understanding, but some rational all-wave understanding must exist.

I think that part of the problem with interpreting the double slit experiment (for example), is that no formulation of QM (that I know of) describes the dynamics of electron localization at an elementary level (like F=ma type of undertanding). I think such an understanding is necessary to avoid the fundamental indeterminism that is present in QM.

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Im not sure that is entirely correct.  Such superluminal causation seems to be something that is a result of assuming a finite and definite end to a particle.

No, it isn't.

I think that part of the problem with interpreting the double slit experiment (for example),  is that no formulation of QM (that I know of) describes the dynamics of electron localization at an elementary level (like F=ma type of undertanding).  I think such an understanding is necessary to avoid the fundamental indeterminism that is present in QM.

Bohm's theory is deterministic, so it avoids the indeterminism of orthodox QM -- and there is no special need in Bohm's theory to explain "the dynamics of electron localization at an elementary level" since electrons just are localized particles. There is also a respectable pure-wave interpretation of QM called GRW (Ghirardi, Rimini, Weber, aka spontaneous collapse or spontaneous localization), but this theory is not deterministic.

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No, it isn't.

If one thinks that energetic interactions that constitute causal mechanisms between two particles travel in space at a finite speed (for example light waves) then, to determine that speed, one must define an interparticle distance. There need not be an interaction that travels faster than the speed of light in the case of entanglement if the two particles cannot be definitively separated.

In other words, the idea of superluminal causation (defined as packets of force that travel faster than light from one partricle to another) requires the boundary of each particle clearly defined. Should the ultimate constituients of matter actually resemble waves, this boundary is not clearly defined (nor should it be). In such a case, an interaction between the waves that is a result of physical contact of the two waves can occur instantaneously betwen two waves whose centers are quite separate.

As I think about this I find that any little dot theory postulates two entities other than particles themselves to explain what regular QM does.

1) a wave that governs particle motion

2) a mechanism for superluminal interactions

Let me just say for the record that I find a little dot theory to be conceptually simpler, intuitive, and not prone to contradictions and indeterminism. I just think the experimental evidence leans the way of the wave.

Also, could you give me some kind of a list of the different quantum theories that you have read, along with a quick description of them?

It also makes me wonder just how many alternative theories have been developed by good scientists, not to mention the thousands (mabye more) that have been thought up some who might be more well described as crackpots?

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If one thinks that energetic interactions that constitute causal mechanisms between two particles travel in space at a finite speed (for example light waves) then, to determine that speed, one must define an interparticle distance.  There need not be an interaction that travels faster than the speed of light in the case of entanglement if the two particles cannot be definitively separated.

I understand the picture you have in mind, but let's be clear about something. Do you think that the derivation of Bell's Inequality somehow assumes a "little dot" model of particles? It doesn't. It doesn't assume any physics model at all. It's just statistics, based on the assumption that the outcome on one side of the experiment doesn't depend on the final settings on the far side. So if the inequality is violated experimentally, the outcome on one side *does* depend on the setting on the other side, and you can put a lower limit on the speed involved (assuming for the moment that there even is a "signal" which propagates with some speed) based on features of the experiment in question (namely, how far apart the two sides are and how long before each outcome is registered the distant setting is set).

That there is superluminal causation is simply an empirical fact. You can't make it go away with some kind of non-little-dot model of the particles. What you *might* do is argue that, based on some plausible model, it doesn't make sense to talk in terms of particles interacting by sending finite-speed signals back and forth. You might have a model in which there aren't really two distinct spatially separated entities, but, rather, one unified blob which extends across the whole region of space where the two detectors are located. And in such a model perhaps it would be appropriate to speak of the "blob" responding as a whole when one corner of it gets tweaked in a certain way (thus rendering talk of the "speed" of "signal propagation" inappropriate). But strictly speaking this still violates relativistic causality. If you've got a hunk of stuff and whacking one end makes the other end jiggle, then it's equally problematic for relativity whether a pressure wave propagates through the stuff at a million times c, or if, instead, the whole hunk "rings" simultaneously the instant the one end is struck. In both cases, something happens over there before a light signal from here could get there, so the idea of effects living exclusively inside the future light cone of causes is out.

In other words, the idea of superluminal causation (defined as packets of force that travel faster than light from one partricle to another) requires the boundary of each particle clearly defined.  Should the ultimate constituients of matter actually resemble waves, this boundary is not clearly defined (nor should it be).  In such a case, an interaction between the waves that is a result of physical contact of the two waves can occur instantaneously betwen two waves whose centers are quite separate.

Not to dwell on this, but if you wanted to take it seriously, you'd basically have to say that in these EPR/Bell experiments, although "particles are detected" at the locations of the two detectors, the causally-relevant parts of the particles are located (right next to each other) in some other spatial region -- say, midway between the detectors where their respective edges touch. In other words, you have a problem explaining how anything gets registered at the detectors.

But this is all really beside the point. If the question is whether relativity's prohibition on superluminal causation is respected by nature, it isn't, and you don't need to consider any particular physical model of particles to know that. That's why Bell's Theorem is so amazingly cool. On the other hand, if the question is whether this particular theory of yours is viable, I think you have some more fleshing out to do before anyone can possibly answer that question.

Also, could you give me some kind of a list of the different quantum theories that you have read, along with a quick description of them?

Well, there's the "copenhagen interpretation" which I wouldn't even mention as a serious theory except that it's been the orthodoxy for almost 100 years. Then there is the de Broglie - Bohm theory, which I have discussed already. It is, I think, quite clearly the most reasonable way of understanding quantum physics. There are some technical physics issues related to it (like whether it's possible to generalize it to more than just non-relativistic QM) but I don't think there are any legitimate philosophic objections to it. Then there is the many worlds interpretation (MWI) which comes in several different versions including the so-called Many Minds Interpretation. Most versions of this are either ill-defined or solipsist -- and in either case I find them too crazy to take seriously. Finally there is the GRW type theories I mentioned before. That's about it, really. There are some fringe interpretations like Cramer's "transactional interpretation" (which tries to avoid faster-than-light causation by having backwards-in-time causality), but this just doesn't really work as a serious theory (for reasons pointed out in Maudlin's book, among others) and nobody in Foundations circles takes it very seriously. And there are some others at that same level. Then there are the crackpot theories you mention, which typically explain one obscure isolated phenomenon or two by the use of some strange ad hoc device which obviously does not work in general.

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But strictly speaking this still violates relativistic causality.  If you've got a hunk of stuff and whacking one end makes the other end jiggle, then it's equally problematic for relativity whether a pressure wave propagates through the stuff at a million times c, or if, instead, the whole hunk "rings" simultaneously the instant the one end is struck. 

I am clear on what you are saying. If something happens over here that causes an instantaneous change over there, it is superluminal causation, regardless of what changes, or how it changes. It is easy to get stuck on a picture of how things occurr and come to improper conclusions, sometimes.

Well, there's the "copenhagen interpretation" which I wouldn't even mention as a serious theory except that it's been the orthodoxy for almost 100 years.  Then there is the de Broglie - Bohm theory, which I have discussed already.  It is, I think, quite clearly the most reasonable way of understanding quantum physics.  There are some technical physics issues related to it (like whether it's possible to generalize it to more than just non-relativistic QM) but I don't think there are any legitimate philosophic objections to it.  Then there is the many worlds interpretation (MWI) which comes in several different versions including the so-called Many Minds Interpretation.  Most versions of this are either ill-defined or solipsist -- and in either case I find them too crazy to take seriously.  Finally there is the GRW type theories I mentioned before.  That's about it, really.  There are some fringe interpretations like Cramer's "transactional interpretation" (which tries to avoid faster-than-light causation by having backwards-in-time causality), but this just doesn't really work as a serious theory (for reasons pointed out in Maudlin's book, among others) and nobody in Foundations circles takes it very seriously.  And there are some others at that same level.  Then there are the crackpot theories you mention, which typically explain one obscure isolated phenomenon or two by the use of some strange ad hoc device which obviously does not work in general.

Thanks, it looks like I have a little reading to do.

All models aside, what would you say would constitute a philosophically valid model of quantum mechanics? I would say the following has to be true of such a theory:

Deterministic causality of particle motion

A Definite state of a particle

Corresponds with experimental evidence

(I say philosophically valid because I just lumped everything associated with correct physics into the experimental evidence part)

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Thanks, it looks like I have a little reading to do.

Why bother? Not that I don't think you should; I'm just curious about your motivation. Are you a physics student or just interested in the subject or...?? Anyway, let me know if I can help suggest something. There's a lot of crap on this topic out there.

All models aside, what would you say would constitute a philosophically valid model of quantum mechanics?  I would say the following has to be true of such a theory:

Deterministic causality of particle motion

A Definite state of a particle

Corresponds with experimental evidence

(I say philosophically valid because I just lumped everything associated with correct physics into the experimental evidence part)

That's a very difficult question. I don't strongly disagree with what you say, though I think "corresponds with experimental evidence" needs to be fleshed out significantly. I mean, it's certainly correct that a theory must be consistent with experiment, but there is more to it than that -- the theory needs to emerge in a certain way from a rational organization and essentialization of the evidence. But saying exactly how this ought to work is equivalent to giving a detailed theory about how induction works in physics, something I'm not in a position to do in this post...

Also, I don't think there's a lot to your other two criteria. I wouldn't require a theory to be deterministic. It's a theorem that any stochastic theory can be turned into a deterministic theory by adding hidden variables. (What's not true is that a non-local stochastic theory like OQM can be made into a local hidden variables theory!) So determinism just isn't a big issue. I suppose you meant that if a theory claimed explicitly that its randomness was fundamental, a philosopher might object to that. But I think a better objection is simply that, given the theorem I mentioned, there cannot possibly be a basis for the claim that the randomness is irreducible. So any such claim should be rejected, not on metaphysical grounds per se but on the grounds that there would be no evidence for the claim. Finally, it's not clear to me what you mean by the requirement that the theory attribute definite states to the particles (or whatever). I can't think of any theory (among the ones I mentioned before) that would fail this test. I mean, a theory which says that the wave function is all that really exists, will attribute a "definite state" to particles -- e.g., the particle is in a superposition of being over here and over there. That's only not a definite state if you smuggle in some notion of what a definite state ought to look like... which is equivalent to smuggling in your own theory and then dismissing the one in question because it's different. But that, obviously, isn't the same as "philosophy requires such and such".

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Why bother?  Not that I don't think you should; I'm just curious about your motivation.  Are you a physics student or just interested in the subject or...??  Anyway, let me know if I can help suggest something.  There's a lot of crap on this topic out there.

I am a student of chemical physics at the university of minnesota (go gophers). I am both interested in the topic and I may be teaching it someday. (My interest in alternative theories is definitely more recreational and my research is more in solid state.) My first teacher of QM in the chemistry department said something like "dont try to make a picture of what is occurring" as a warning to the (usally highly visual) chemistry students. I guess I am still rebelling against that advice, but I am not finding any clear answer. Its not really a big deal, but there is a something that is occurring, and therefore some mental image of what is occurring must exist.

I am curious to know which books you find particularily insightful (orthodox QM or otherwise). I may get the time to read them one of these years.

I think "corresponds with experimental evidence" needs to be fleshed out significantly.  I mean, it's certainly correct that a theory must be consistent with experiment, but there is more to it than that -- the theory needs to emerge in a certain way from a rational organization and essentialization of the evidence.  But saying exactly how this ought to work is equivalent to giving a detailed theory about how induction works in physics, something I'm not in a position to do in this post... 

I had not thought of this question of induction. I can't really argue with anything you say here but I wonder about the validity of ideas that would be nearly impossible to emerge simply from experiment (the possibility of quantized time and space for example).

Also, I don't think there's a lot to your other two criteria.  I wouldn't require a theory to be deterministic.  It's a theorem that any stochastic theory can be turned into a deterministic theory by adding hidden variables.  (What's not true is that a non-local stochastic theory like OQM can be made into a local hidden variables theory!)  So determinism just isn't a big issue.  I suppose you meant that if a theory claimed explicitly that its randomness was fundamental, a philosopher might object to that.  But I think a better objection is simply that, given the theorem I mentioned, there cannot possibly be a basis for the claim that the randomness is irreducible.  So any such claim should be rejected, not on metaphysical grounds per se but on the grounds that there would be no evidence for the claim.  Finally, it's not clear to me what you mean by the requirement that the theory attribute definite states to the particles (or whatever).  I can't think of any theory (among the ones I mentioned before) that would fail this test.  I mean, a theory which says that the wave function is all that really exists, will attribute a "definite state" to particles -- e.g., the particle is in a superposition of being over here and over there.  That's only not a definite state if you smuggle in some notion of what a definite state ought to look like... which is equivalent to smuggling in your own theory and then dismissing the one in question because it's different.  But that, obviously, isn't the same as "philosophy requires such and such".

This is all very interesting. This point about smuggling in your own theory is a good one, but again, I cant help but ask if the possibility for forming a mental image of the situation is irrevocably doomed... This is beginning to sound very epistemological. I can't possibly imagine that some learning style (visual) is fundamentally unable to comprehend some part of nature. Naturally, mathmatics is required to make any understanding quantitative, but qualitatively, anything should be able to be understood through many different learning styles.

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I am a student of chemical physics at the university of minnesota (go gophers).  I am both interested in the topic and I may be teaching it someday.  (My interest in alternative theories is definitely more recreational and my research is more in solid state.) My first teacher of QM in the chemistry department said something like "dont try to make a picture of what is occurring" as a warning to the (usally highly visual) chemistry students.  I guess I am still rebelling against that advice, but I am not finding any clear answer.  Its not really a big deal, but there is a something that is occurring, and therefore some mental image of what is occurring must exist.

I'm with you. A proper theory in physics should give a *physical* account of what's happening in physical processes, and this should be "visualizable" in some terms. (Maybe the physical processes postulated by the theory don't look like familiar things like billiard balls, but they should look like something, so to speak.) This is related to the point that a proper theory is not just formalism. It's important to have a formalism, because without that you've just got loose talk (e.g., TEW) -- but the formalism must be interpreted. A theory has to tell you what the formalism means, what the equations in the theory are *about*. And as soon as it's clear what the theory is about, you should be able to "visualize" those things and their actions.

I am curious to know which books you find particularily insightful (orthodox QM or otherwise).  I may get the time to read them one of these years.
The best not-too-technical presentation of the fundamental interpretive problems with QM and the various possibilities for addressing them (that is, the various theories I listed before) is David Albert's book "Quantum Mechanics and Experience." It gets a bit weird at times (when he raises questions about how consciousness fits into all these theoretical models) and his writing style is unique. (I love it, but many people can't stand it.) That might be a good place to start.

Jim Baggott's book "The Meaning of Quantum Theory" is also pretty good. (I think there's a second edition of that out now with a different title. "Beyond measure" maybe?)

If you want a visualizable model of QM, then you need to study Bohmian Mechanics. The article by S. Goldstein at plato.stanford.edu is excellent. Jim Cushing's "Quantum Mechanics: Historical Contingency and the Copenhagen Hegemony" gives a very nice historical survey. Bohm and Hiley's "The Undivided Universe" is a fairly readable textbook-type presentation of the theory. Holland's "The Quantum Theory of Motion" is a denser textbook-style presentation. And I can't recommend Bell's papers (collected in the book "Speakable and Unspeakable") highly enough. He is an amazingly clear thinker and writer, and is almost 100% responsible for the resurgence in interest in Bohm's theory in the last couple of decades.

On a shorter timescale, maybe you'd enjoy some of these papers:

http://www.arxiv.org/find/quant-ph/1/au:+n...ec7c3c560531df1

... This is beginning to sound very epistemological.  ...

Good. That was the perspective I meant to argue for before when I tiraded against rationalism. If you want to know which theory in physics is true, metaphysics just isn't going to tell you. The question is fundamentally epistemological, and there is no valid "short cut".

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  • 2 weeks later...

Would you agree that there must ultimately be some point at where the question "but why?" is no longer answerable? If not, in what form could the "ultimate theory" possibly be, such that it you never have unanswered "why" questions?

Is it is possible the idea that "everything is deterministic" and that it has an "underlying model" is a result of intuition (i.e., inductive logic)?

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