Relativity & Quantum Theory: Is Locality Violated?

[ttn]

What I'm trying to point out is that there is maybe a subtlety in the concept of "the same entities". If an "entity" is "a state in a classical phase space", then these "same" entities are just "copies" if we have SEVERAL classical phase spaces. If "living cat" is a concept belonging to a classical phase space, then having generated two phase spaces means we now have two of these classical cats, one in each phase space. Of course, quantum-mechanically, it is "the same entity", but who says that what you intuitively call an entity (such as "living cat") is not a concept that only has meaning in a classical context ?
So - this was my point - if your theory GIVES RISE to several of these classical phase spaces, then you just have several of these entities around, and if ONE of these classical phase spaces corresponds to what you are classically used to, then that's good enough, no ? Whether or not they find their common origin in ANOTHER CONCEPT, which is a "quantum cat" is something else. As you've only seen CLASSICAL cats, you have no idea what is a quantum cat, and hence you cannot claim that it is silly to talk about "a quantum cat being live and dead": you only know about classical cats, and our theory gives us DIFFERENT classical cats, which are OR live OR dead. A quantum cat is then nothing else but a "generator of classical cats" in this respect.

I get all of this. I just don't understand what you think any of it has to do with refuting my claim that, according to MWI, we're deluded when we look at a cat and perceive that it is alive. The truth is that there is, as you say, a "quantum cat" which is in a big entangled superposition of alive and dead. This simply does not match with my direct perceptual experience. So what I come to believe based on that experience does not *correspond* to the real (quantum) state of the cat. My belief is *false*. I am *deluded*.

I suppose you want to go back to this old argument that it's not really a delusion, but merely a true belief about some one *part* of the real world. And that takes us back to the old debate about whether the word "part" is really appropriate here. You think it is; I think it isn't. And I suppose this is what you meant when you said maybe there was a "subtlety in the concept of the same entities." Frankly, though, that kind of statement alone is enough to make me reject this whole theory as not serious. It's like when Bill Clinton starts saying "it depends on what the definition of the word 'is' is", you know (as I think Griffiths says in one of his texts in a slightly different context) you should hold onto your wallet. =)

This doesn't need to be the case: there was not THE consciousness token, there was MY consciousness token. Whether or not the others got "new ones", I left it out of the discussion, because it doesn't mean anything useful.

But then I don't think this version of the theory is coherent. If all the copies of you that the splittings generate all get consciousness tokens, then what is the meaning of the probability associated with the Born rule? There's now no one unique happening for those probabilities to be probabilities *of*. If your body splits into 10 copies and they all, with certainty, are conscious of the material surroundings in their branch, then what possible meaning can it have to associate some number like 37% with one or the other of the copies?

Also, a slightly different point for the benefit of lurkers, if you were to give each human being his own "consciousness token" obeying the Born rule, in a very short period of time, the odds are spectacularly good that no two consciousness tokens will inhabit the same branch. So what you consciously think are other sentient beings in the world, are in fact mere mindless hulks. (That is David Albert's term, and his point actually.) Call that one more delusion.

If, in a classical world, I can already not find out whether another body is conscious or not (because behaviourally identical), why would I break my head over a COPY in a world that I cannot even behaviourally interact with ? Even classically, you have not to assume that "others" are conscious. One consciousness is enough to explain your subjective experiences, even purely classically.

I'm sorry, but this is silly. There is good empirical evidence that other people are conscious, and you don't have to know Newtonian mechanics (not to mention later more advanced physics) to know this. Your point, that the non-consciousness of other people is consistent with classical physics, is about as relevant and interesting as the point that the Earth being flat is consistent with classical physics. Sure, but who cares, since we know it isn't true? The interesting point is that other people in fact *being* conscious *is* perfectly consistent with classical physics. If it weren't, since we know for sure that other people are conscious way before we get to advanced things like classical physics, we'd rationally have to *reject* classical physics. Happily, there's no need to do that, though, since there's no conflict.

With MWI on the other hand, we *do* have this conflict. If you accept MWI, you have to accept that what you erroneously took to be conscious-others are in fact mindless hulks. I call that good reason to reject MWI. It contradicts basic empirically grounded knowledge (and then, in order to escape this problem, spins a fantasy brain-in-vat scenario about how all of our earlier empirically grounded knowledge is delusional).

There's no need to assume that another consciousness exists apart from your own one - no matter whether we do quantum theory or classical theory.

Sure, this isn't an issue that really comes up in physics. But that doesn't mean it isn't 100% settled *prior* to doing physics (classical, quantum, or otherwise).

If, however, classically, you assume that others are conscious "by analogy with yourself", well, you can do the same quantum-mechanically. Whatever behaves more or less "as if it is conscious" is then declared to be conscious.

Ooh, interesting... so maybe the one last final thing we're deluded about is that we ourselves are conscious! (Please note how self-refuting such a claim would be.)

But this discussion doesn't matter, classically or quantum mechanically. The only thing that counts is what happens TO YOUR OWN conscious experience, ...

But see, to me, that is *not* "the only thing that counts. I actually believe that knowledge is hierarchical, and that we have to regard the more basic stuff as largely settled. If a scientific theory requires me to accept that *everything* I believed before (based on direct perception and low-level inference therefrom) is a delusion, I reject it.

Of course "delusion" in the sense that naive realism is not true, in that what we perceive with our senses is not ALL there is to the world. But not "delusion" in that there really IS a (part of) reality that corresponds to what you are aware of. That's not a big surprise, is it ?
You're bathing in a SEA of neutrinos and you've never seen them. There are more neutrinos around you than anything else but you're not seeing, feeling or hearing them. Are you deluded now ?

No, because I don't have any direct perceptual knowledge of those neutrinos (including their non-existence). Of course there are all sorts of facts I am not aware of. The point is, the ones I *am* aware of, I'm *aware* of. If I see a living cat, there might be neutrinos flying through it or Martians dancing jigs on Venus or who knows what else out there somewhere, but *there is a living cat*. MWI asks me to accept not that there's more facts out there in the world than that I perceive, but that what I perceive is a delusion. It really is different.

 

[ttn]

I know. But I wanted to illustrate, with a *SILLY* example, that "can influence the probability of something to happen" and "has a causal influence on" is NOT the same. The "naturalness" of Bell's statement comes from the tacit identification of both statements. We like to think that the only CAUSAL INFLUENCES on an event E "come from" its past light cone. And, if we are talked into accepting erroneously the identification of the above two statements, this translates into: "the PROBABILITY of something to happen at event E can only depend upon all we know in the past lightcone of this event." which is the essence of Bell's statement, of his definition of Bell locality.

No, I think you may have missed something crucial. The statement is *not* about "all we know in the past lightcone of this event." If it were merely that, it would be obviously possible to say "we didn't know enough", in which case the subjective probability of a given event *could* change, when some spacelike information is specified, but *without* any relativity-violating causal influence.

But "Bell Locality" is not a statement about subjective probabilities. It is a statement about a theory's *dynamics*. And the thing we have to specify before we can apply the criterion is not "all we know in the past lightcone of this event" but rather "all that *exists* in the past lightcone of this event." That is, Bell Locality requires a *complete specification of the actual state* in the past light cone.

How, you ask, could we ever in practice *know* whether or not we had specified the states *completely*? Not to worry -- this is what *theories* do for us. A theory (by definition, here) is something which proposes some kind of candidate complete description of states. We may then take the theory at its word and apply the criterion to find out if it is local. This of course doesn't mean the theory is or isn't *true*. That's a different question. But *given* some candidate for a "complete specification of states" (and a candidate for the dynamics, which allows us to calculate probabilities for events) -- i.e., given a proposed *theory* -- we can ask: "is the theory causally local?". That is what the Bell Locality criterion does.

Of course Bell is thinking of "things happening at spacelike distance should not have a CAUSAL INFLUENCE on what's going on at event E" and he's translating this into "their knowledge should not alter the probability of what's happening at E". And of course he's aiming for spacelike distances.

I don't know exactly what you mean by "their knowledge", but this has *nothing* to do with anybody's knowledge. The criterion applies to *theories* and the probabilities involved are simply a way of talking about the *dynamics* of the theories. What any person does or does not *know* is completely and totally irrelevant.

But my silly example just wanted to show that KNOWLEDGE about something CAN alter probabilities of something to happen, without them influencing that something causally.

If you have a *theory* whose *dynamics* has probabilities depending on somebody's knowledge, I would say that is a very strange theory indeed. But even this is no objection to Bell Locality, unless you want to insist that the probabilties depend on the knowledge that someone acquires at spacelike separation and that the assigned probabilities change when this is specified *and* you want to insist that such dependence is consistent with relativity's prohibition on superluminal causation!

So it is not true, in general, that "knowledge about stuff alters the probability of outcomes at E" means that "stuff" has a causal influence on E.

Absolutely right. But irrelevant since Bell Locality isn't about subjective probabilities; knowledge just doesn't enter into it one way or the other.

And now we're home, because, IF IT ISN'T TRUE that KNOWLEDGE OF STUFF CHANGES PROBABILITIES OF EVENT E, then there is NO REASON to Bell's definition of locality.

With all due respect (and it is considerable), you have not appreciated Bell's definition. He's already understood and eluded your worry.

 

[Hurkyl]

I just don't understand what you think any of it has to do with refuting my claim that, according to MWI, we're deluded when we look at a cat and perceive that it is alive. The truth is that there is, as you say, a "quantum cat" which is in a big entangled superposition of alive and dead. This simply does not match with my direct perceptual experience. So what I come to believe based on that experience does not *correspond* to the real (quantum) state of the cat. My belief is *false*. I am *deluded*.

There's (at least) one different interpretation: that when you have a quantum cat, we can say with certainty that it either looks alive or it looks dead: that's simply how quantum things look!

 

[ttn]

There's (at least) one different interpretation: that when you have a quantum cat, we can say with certainty that it either looks alive or it looks dead: that's simply how quantum things look!

Sure, but does that really help? So the way X looks is fundamentally in conflict with the way X is. The perceptual experience doesn't correspond to the facts. So the perceptual experience is delusional.

 

[vanesch]

But then I don't think this version of the theory is coherent. If all the copies of you that the splittings generate all get consciousness tokens, then what is the meaning of the probability associated with the Born rule? There's now no one unique happening for those probabilities to be probabilities *of*. If your body splits into 10 copies and they all, with certainty, are conscious of the material surroundings in their branch, then what possible meaning can it have to associate some number like 37% with one or the other of the copies?

YOUR experience. If there are 10 copies of your body, you might assume that ONE of these "is you" and the others are "copies". The probability for a body to be *your* experience, and not a copy's experience, is given by the Born rule. This doesn't say anything about conscious experiences those other copies might, or might not have.

Now, I have to point out that I'm "heretic" here with respect to most MWI-ers. Most MWI-ers have the hope of establishing, in one way or another, the Born rule "emerge" from an "uniform distribution", or world counting or whatever. What I think I've established is that this includes AT LEAST one extra postulate, and if the goal of that postulate is to allow us to say that FINALLY what we will be consciously aware of is given by the Born rule, we might as well take the shortcut and postulate INITIALLY this Born rule.
There are schemes in the making which hope to establish the "standard" MWI programme though. I'm thinking for instance about Robin Hanson's "mangled worlds" (it's on the arxiv), which, for short, establishes that these classical worlds only occur for a certain "time of stability" for those branches which are bigger than a certain lower hilbert norm (relative to the biggest ones). So if you postulate that you need a time of stability (say, of the order of at least a nanosecond) in order to be "eligible" as "classical world", and with this cutoff, you do "world counting", then he has indications that you arrive at something very close to the Born rule.
My point is simply that you don't have to go through all these pains. Just POSTULATE that what you experience, in the end, is a world drawn according to the Born rule, and that's good enough.

Also, a slightly different point for the benefit of lurkers, if you were to give each human being his own "consciousness token" obeying the Born rule, in a very short period of time, the odds are spectacularly good that no two consciousness tokens will inhabit the same branch. So what you consciously think are other sentient beings in the world, are in fact mere mindless hulks. (That is David Albert's term, and his point actually.) Call that one more delusion.

Well, if I were to give each human and each cat his own consciousness token (of which, I repeat, I don't see the utility...), then this token's "voyage" throughout the successive quantum states (using the Born rule) will indicate what they will experience ; in which successive classical worlds they will be. But there's no problem with the CREATION of NEW tokens in the other worlds, and for the "copies" of others in the worlds visited by the "original" consciousnesses.

I'm sorry, but this is silly. There is good empirical evidence that other people are conscious

Sorry, but that's impossible. There can only be BEHAVIOURAL empirical evidence, and behaviourally you cannot find out if there is, or if there isn't, a subjective experience "lived" by the BODY under study.

The interesting point is that other people in fact *being* conscious *is* perfectly consistent with classical physics. If it weren't, since we know for sure that other people are conscious way before we get to advanced things like classical physics, we'd rationally have to *reject* classical physics. Happily, there's no need to do that, though, since there's no conflict.

Apparently you didn't grasp the "hard problem of consciousness" then. No physical observation can distinguish between a physical process with which there goes a subjective experience, and an identical physical process which is not subjectively experienced. So consciousness of others will never be a falsification or a support for a physical, or scientific theory.

The only reason why we THINK that others are conscious is "by analogy to ourselves". How do you determine whether stones are conscious or not ?

With MWI on the other hand, we *do* have this conflict. If you accept MWI, you have to accept that what you erroneously took to be conscious-others are in fact mindless hulks.

Not at all. I prefer to think of them as "mindless hulks" in the same way I can ALREADY assume that others are "mindless hulks" ; quantum theory or not! But you can have it your way if you want to, and assign conscious experience to anything that classically breaths or not. This doesn't change, in the slightest bit, any physically observable fact by YOU.

For instance, you cannot know whether my body is conscious. Only *I* can know that. You can only perceive actions of my body, which could ultimately be explained by the physics of it ; by neurological and physiological processes. If you knew all that, you would be perfectly able to explain all my body does, says and writes on PF.

In the same way, I cannot know whether YOUR body is conscious.

Now, because I know that my body is conscious, and maybe you know that yours is, and because we see behavioural similarities, by ANALOGY and association, we take it that we're both conscious. But this will remain for ever a hypothesis. And from the moment physical processes are behaviourally totally different, and this basis of analogy disappears, WE HAVE NO MEANS at all to establish ever, whether this physical process is conscious or not. Hence your impossibility to establish whether stones are conscious. Unless by convention.

Ooh, interesting... so maybe the one last final thing we're deluded about is that we ourselves are conscious! (Please note how self-refuting such a claim would be.)

No, that will never be the case. It is the ONLY thing we know for sure.

No, because I don't have any direct perceptual knowledge of those neutrinos (including their non-existence). Of course there are all sorts of facts I am not aware of. The point is, the ones I *am* aware of, I'm *aware* of. If I see a living cat, there might be neutrinos flying through it or Martians dancing jigs on Venus or who knows what else out there somewhere, but *there is a living cat*. MWI asks me to accept not that there's more facts out there in the world than that I perceive, but that what I perceive is a delusion. It really is different.

No, MWI asks you to consider that, next to this living classical cat, there might be another world in which there is another classical dead cat.
To me, this is not so different from the neutrinos.

 

[DrChinese]

Part One: It is an empirical fact that whenever Alice and Bob measure along the same axis, their results are *perfectly (anti-) correlated*. We then ask: how must a Bell Local theory work if it is going to successfully predict this empirical fact? The answer turns out to be: its state descriptions must include variables which, in effect, pre-assign measurement outcomes for all spin components. Such variables are often called "local hidden variables" or some such.

Why does a Bell local theory need to be realistic to explain the correlations? You might want to prove that requirement. I know it seems like that is the only possibility to you, but it won't seem that way to everyone.

 

[LnGrrrR]

Vanesch,

This question is a bit off-the-wall, but I feel the need to ask it anyways.

The many-worlds question posits the idea that we're seeing only one of the 'outcomes' of waveform collapse, and other realities see the other results, correct?

Decoherence occurs though (and I'm describing this in the least scientific way I can) when there are too many 'waveform paths', so that forms function in a 'classical' sense.

Here's the question...is there a possibility of a universe where all the waveforms could 'sync up' in an object, thereby allowing a macroscopic object to behave how QM says it should?

 

[LnGrrrR]

Also, a slightly different point for the benefit of lurkers, if you were to give each human being his own "consciousness token" obeying the Born rule, in a very short period of time, the odds are spectacularly good that no two consciousness tokens will inhabit the same branch. So what you consciously think are other sentient beings in the world, are in fact mere mindless hulks. (That is David Albert's term, and his point actually.) Call that one more delusion.

I'm sorry, but this is silly. There is good empirical evidence that other people are conscious, and you don't have to know Newtonian mechanics (not to mention later more advanced physics) to know this. Your point, that the non-consciousness of other people is consistent with classical physics, is about as relevant and interesting as the point that the Earth being flat is consistent with classical physics. Sure, but who cares, since we know it isn't true? The interesting point is that other people in fact *being* conscious *is* perfectly consistent with classical physics. If it weren't, since we know for sure that other people are conscious way before we get to advanced things like classical physics, we'd rationally have to *reject* classical physics. Happily, there's no need to do that, though, since there's no conflict.

With MWI on the other hand, we *do* have this conflict. If you accept MWI, you have to accept that what you erroneously took to be conscious-others are in fact mindless hulks. I call that good reason to reject MWI. It contradicts basic empirically grounded knowledge (and then, in order to escape this problem, spins a fantasy brain-in-vat scenario about how all of our earlier empirically grounded knowledge is delusional).

I have a friend who takes this stance, and the question I usually ask him, "Well, how do you know if you're actually 'real' then?" His response tends to be 'just cause'.

 

[vanesch]

With all due respect (and it is considerable), you have not appreciated Bell's definition. He's already understood and eluded your worry.

Maybe. It is always difficult to respond to an "accusation" of not having understood something and being deluded into thinking one did. The only answer I can think of is by saying exactly what I understand of Bell.

The way I understand Bell is the following. I know you see it larger, but I think that there are hidden assumptions in the enlargement. Here it goes. I think that Bell considered (consciously or not), a DETERMINISTIC evolution and considered that all of our probabilistic considerations resulted from us not having full knowledge of the fully deterministic description of nature - whether this impossibility was practical or in principle.
Given a deterministic evolution, and a requirement of non-causality between spacelike separated events, which means that no decision taken at one event U (like, deciding in which direction to put your polarizer) can CHANGE the full state in the backward lightcone of an event E, and hence not change the deterministic outcome of all thinkable measurements we can do at E, the probability of our outcome at E cannot depend on anything EXTRA that was produced at U. Of course, there can be a dependence on the outcome at U, BUT ONLY IN SUCH A MEASURE THAT this U was influenced by the SAME "beables" as those that were IN ANY CASE going to determine what was going to be the result at E.
In other words, the only correlation that can be seen between the outcomes at U and the outcomes at E are those of "common origin" - and this for ALL POTENTIAL OUTCOMES OF ALL THINKABLE MEASUREMENTS. And this is clear if the "beables" in the past lightcone of E ALREADY ENTIRELY FIXED what was going to happen at E, in all possible and thinkable measurements we can decide about at E (and at U).

So the fundamental hypothesis is that, for all thinkable outcomes at U and at E, the outcomes are ALREADY DETERMINISTICALLY FIXED by what happened in their past lightcones. They only APPEAR stochastical to us because we lack certain information about this fully deterministic initial state back in the past lightcone of E and of U. And as such, IT IS PLAUSIBLE TO POSTULATE A PROBABILITY DISTRIBUTION over these initial deterministic states, from which ALL PROBABILITIES OF ACTUAL AND POTENTIAL MEASUREMENTS at U and E can be derived ; and the only correlations we can find between U and E are those generated by this postulated common probability distribution, which has to have in it, all the possible outcomes we COULD obtain potentially.

The essence of Bell's theorem is the existence of an overall probability distribution of actual and potential measurement outcomes at E and U - and to me this makes perfect sense ONLY in the case of a deterministic evolution but with partly unknown initial states. In fact, in this case, Bell makes really perfectly sense: given the fact that the outcome is ENTIRELY DETERMINED by the "hidden state" in the past lightcone of E, its "probability of giving a result" only depends on the probability we assigned to the states that will (deterministically, with 100% certainty) evolve in this result. All correlations with things which cannot influence this evolution (which are hence outside of the past lightcone) are then purely correlations due to "common origin", and which are hence generated by *the same probability distribution of those initial states*.

However, in the case of *stochastic* evolution, meaning, there's NOTHING IN NATURE, no hidden state or anything, which "determines" what's going to happen, but "it just happens" one way or another, there's no way to IMPOSE how this randomness should occur. Of course, signal locality imposes a certain constraint in the link between CHOICES MADE at an event U and RESULTS OBTAINED at an event E at spacelike distance from U, but there's no a priori way to REQUIRE any other constraint on the inherent randomness of nature. In the same way that in a strictly stochastic theory, the randomness of individual events is *unexplained*, in the same way *correlations* can be unexplained.
In a strictly stochastic theory, THERE NEEDS NOT TO BE a common probability distribution which describes all POTENTIAL outcomes at U and E: there only needs to be a distribution of the ACTUAL outcomes as a function of the decision taken to measure this or that. As there is, by definition, NO DYNAMICAL EXPLANATION for this randomness (because if there were, we would have a DETERMINISTIC theory!), there can be no requirement on this randomness, and there can be no speculation about what WOULD have happened if we did a measurement we didn't perform: that's only something we can reasonably think about if we know a DETERMINISTIC mechanism on how the randomness comes about.
So there's no reason, in this case, to impose the same requirements as in the case of a deterministic evolution of a prior existing common probability distribution of all potential and actual measurement outcomes (in other words, to impose Bell locality).

But of course the temptation is great to turn a stochastic theory into a deterministic one with a "hidden state" in some way, so that the APPARENT stochasticity is IN FACT resulting from an underlying deterministic evolution, but of which we can only (in principle or in practice) determine in a probabilistic way the initial state. In THIS case, of course, Bell makes sense again.

So I come back to my old claim that Bell locality is nothing else but "signal locality on a principal level" and "a requirement of fundamental determinism".

This is how *I* understand Bell's theorem.

Now, this reflection (the underlying assumption of fundamental determinism) is in fact no problem, nor for classical physics, nor for MWI style quantum theory, nor for Bohmian mechanics: they are ALL deterministic theories.
However, the reflection IS relevant to "algorithmic" interpretations of QM: if you take it that the QM "algorithm" is just calculating "probabilities of outcomes" as in a fundamentally STOCHASTICAL theory, then you cannot make the Bell assumption. The only thing you can conclude is that it won't have an underlying deterministic theory which is local in a fundamental sense.Again, maybe I missed its content.

 

[LnGrrrR]

Vanesch,

I'm a bit confused on your consciousness idea. Is it your idea that mindless hulks CAN exist in your MWI? Or can they not?

If they CAN exist, how do you know whether or not you are conscious?

 

[vanesch]

Vanesch,
I'm a bit confused on your consciousness idea. Is it your idea that mindless hulks CAN exist in your MWI? Or can they not?

It has nothing to do with MWI or anything. When I first wrote about it, I assumed some knowledge about "the hard problem of consciousness".

Here's a quote from the Internet Encyclopedia of Philosophy:
http://www.iep.utm.edu/c/consciou.htm

Joseph Levine (1983) coined the expression “the explanatory gap” to express a difficulty for any materialistic attempt to explain consciousness. Although not concerned to reject the metaphysics of materialism, Levine gives eloquent expression to the idea that there is a key gap in our ability to explain the connection between phenomenal properties and brain properties (see also Levine 1993, 2001). The basic problem is that it is, at least at present, very difficult for us to understand the relationship between brain properties and phenomenal properties in any explanatory satisfying way, especially given the fact that it seems possible for one to be present without the other. There is an odd kind of arbitrariness involved: Why or how does some particular brain process produce that particular taste or visual sensation? It is difficult to see any real explanatory connection between specific conscious states and brain states in a way that explains just how or why the former are identical with the latter. There is therefore an explanatory gap between the physical and mental. Levine argues that this difficulty in explaining consciousness is unique; that is, we do not have similar worries about other scientific identities, such as that “water is H2O” or that “heat is mean molecular kinetic energy.” There is “an important sense in which we can’t really understand how [materialism] could be true.” (2001: 68)

David Chalmers (1995) has articulated a similar worry by using the catchy phrase “the hard problem of consciousness,” which basically refers to the difficulty of explaining just how physical processes in the brain give rise to subjective conscious experiences. The “really hard problem is the problem of experience…How can we explain why there is something it is like to entertain a mental image, or to experience an emotion?” (1995: 201) Others have made similar points, as Chalmers acknowledges, but reference to the phrase “the hard problem” has now become commonplace in the literature. Unlike Levine, however, Chalmers is much more inclined to draw anti-materialist metaphysical conclusions from these and other considerations. Chalmers usefully distinguishes the hard problem of consciousness from what he calls the (relatively) “easy problems” of consciousness, such as the ability to discriminate and categorize stimuli, the ability of a cognitive system to access its own internal states, and the difference between wakefulness and sleep. The easy problems generally have more to do with the functions of consciousness, but Chalmers urges that solving them does not touch the hard problem of phenomenal consciousness. Most philosophers, according to Chalmers, are really only addressing the easy problems, perhaps merely with something like Block’s “access consciousness” in mind. Their theories ignore phenomenal consciousness.

In other words, physical theories NEVER say anything about what's called "phenomenal consciousness" in the above text, nor does neurobiology or any other scientific discipline.

As such, one could make it easy, and just say there's only one real consciousness, which is mine (yours). It's the simplest assumption. I can even "empirically prove it" I stick a pin in my leg, and I feel pain. so there's some consciousness involved here, because I feel it. I now stick a pin in YOUR leg, and I don't feel anything. Hence, there's no consciousness involved. QED

Ok, you'll tell me that you'll scream and shout and hit me in the face, but this is a PHYSICAL REACTION I could perfectly well analyse if I knew the physics of your body well enough. I could follow some nerve pulses going from your leg to your brain, I could follow the processing in your brain, resulting in nerve pulses going to your throat and lungs resulting in vibrating air which I hear, and pulses going to your arm and fist hitting me in my face. This would be "system analysis" in the same way I could analyse how programmable logic circuits would react to certain stimuli.

So, in a certain respect, it is simpler to consider that there is only one conscious being (me), and one subjective experience (mine) and all the rest is just physics. This has nothing per se to do with quantum theory or classical physics. It's the easiest way to reason. After all, I'm not aware of any OTHER subjective experience apart from mine.

But then, by analogy, I could accept the hypothesis that SIMILAR bodystates also relate to *other* conscious experiences. I can never know for sure of course, but it sounds acceptable, somehow, that other people might be also having a subjective experience of their own.
Well, then, repeat the explanation from their point of view !

Now, it also seems that I derive my conscious experience from a certain part of a physical world (called, my body state). And this is what I do, then: I try to explain from WHICH bodystate I'm deriving this subjective experience. In classical physics, it derives from certain dynamical states of matter (corresponding to body states). It's not because there's such a state somewhere that *I* experience this state. I only experience ONE such state. I don't know why, but it seems to be so. I experience the state of some matter which I call "my body", and I don't seem to experience the state of something very similar, which is "your body". I don't really have an explanation for this. I experience certain matter states, and not some other, similar, matter states. Don't know why.

Now, in MWI quantum physics, this is about the same. But now, I seem to experience not the FULL state of some material structure, but only ONE of its terms. So be it. I was there already in classical physics: I couldn't understand why I experienced certain matter states (body 1, also called "my body"), and not others which were very similar (body 2, also called "your body"). In classical physics, we then said that body 2 was maybe experienced by ANOTHER consciousness (namely you). Or maybe not. Who knows. So be it.
Well, I do the same in MWI: I seem to experience only ONE term of a body state. We now say that those other states are maybe experienced by OTHER consciousnesses ("copies of me"). Or maybe not. Who knows. So be it.

There's a difference, though. In classical physics, once I've accepted that I'm "related to a certain matter state called "my body"", I KEEP to this matter state, which evolves classically and continuously. So once the choice is made, because of the continuity of evolution in classical physics, I *stick* with the same state which is evolving. In MWI quantum theory, this is not true: sometimes the state from which I derive my subjective experiences SPLITS in several "states from which we can derive a conscious experience". And then, there's a choice to be made which will be my "new" matter state to which my subjective experiences "stick". THIS is the new thing, and this is then determined by the Born rule. Why ? Don't know. In the same way I already didn't understand why I experienced my body and not yours, I don't know why I experience THIS body state, and not that one.

But the important part in all this is this: to derive what *I* experience, it doesn't make any difference whether I postulate, or not, whether other similar states are experienced by other consciousnesses.


As to your question:

If they CAN exist, how do you know whether or not you are conscious?

Ask Descartes :-) It is the ONLY thing that is absolutely knowable.
All the rest is hypothesis.

 

[ttn]

Why does a Bell local theory need to be realistic to explain the correlations? You might want to prove that requirement. I know it seems like that is the only possibility to you, but it won't seem that way to everyone.

First a terminological point: I'd urge you not to use the term "realistic." I know you just meant it as a one-word summary of what I claimed in the earlier post empirically-adequate Bell Local theories had to be like. But the particular word "realist" has such a whole slew of other meanings, it's dangerous to use it here for this specialized purpose; you run the risk of forgetting later that you *didn't* mean one of those other possible meanings of the word. But... I won't lose sleep over terminology if you insist.

In regard to the substantive question (how to prove that a Bell Local theory which successfully accounts for the perfect anti-correlation of outcomes when Alice/Bob measure along the same axis, must possesses this particular claimed structure) would it be a turn-off if I just referred you to section 3 of

http://www.arxiv.org/abs/quant-ph/0601205

? The formal proof is there. I could try to explain it in less formal terms here instead, but that seems pointless when the more careful presentation already exists. Of course I'd be delighted to entertain questions/objections about that section of the paper.

 

[ttn]

However, in the case of *stochastic* evolution, meaning, there's NOTHING IN NATURE, no hidden state or anything, which "determines" what's going to happen, but "it just happens" one way or another, there's no way to IMPOSE how this randomness should occur. Of course, signal locality imposes a certain constraint in the link between CHOICES MADE at an event U and RESULTS OBTAINED at an event E at spacelike distance from U, but there's no a priori way to REQUIRE any other constraint on the inherent randomness of nature.

I think this whole issue/objection comes down to this. What should relativity require for a non-deterministic theory?

In the same way that in a strictly stochastic theory, the randomness of individual events is *unexplained*, in the same way *correlations* can be unexplained.

Yes, that's precisely the issue. Do we allow (as consistent with relativity) that irreducibly-random events at spacelike separations should nevertheless demonstrate persistent correlations? For example, Alice and Bob are very far apart and independently flip coins (and in a universe where the outcomes aren't based on any micro-hidden-details, but are genuinely irreducibly random) but magically always get the same outcomes (both H or both T).

Is such a thing consistent with relativity? I say "no" and am thus not at all bothered (but rather relieved) that such a scenario violates Bell's local causality requirement. But I am admittedly at a loss as to what to say next...

Maybe it would be useful to ask: could anyone think of a Lorentz invariant candidate toy theory that would predict the "both H or both T" example above? The collapse postulate of your "algorithmic" orthodox QM is surely not going to work here, right?

 

[Hurkyl]

Sure, but does that really help? So the way X looks is fundamentally in conflict with the way X is. The perceptual experience doesn't correspond to the facts. So the perceptual experience is delusional.

Why? What is the conflict?

Can you explain why there's a confict in a quantum cat looking as if it was alive or looking as if it was dead?

I rather suspect that you have simply developed a bias based on the fact you first learned that classical cats appear as if they are alive or as if they were dead, and so you're conditioned to believe that cats that appear as if they are alive or as if they were dead must be classical.

 

[Hurkyl]

Maybe it would be useful to ask: could anyone think of a Lorentz invariant candidate toy theory that would predict the "both H or both T" example above? The collapse postulate of your "algorithmic" orthodox QM is surely not going to work here, right?

It seems easy enough.

There are two purely random coins in the universe: A and B, and each may be flipped once. (For simplicity)

The joint distribution on the flips is given by:
P(HH) = 1/2
P(HT) = 0
P(TH) = 0
P(TT) = 1/2

I've not postulated a state of the universe, or any sort of collapse. I've simply posited the existence of a pair of random coins, and stated their joint probability distribution.

This is manifestly Lorentz-invarient, since it makes absolutely no reference to space-time whatsoever.


The only thing that's violated is, when the coins are flipped at space-like separated times, that the joint probability distribution violates the mathematical criterion for statistical independence.

 

[LnGrrrR]

Vanesch,

HEhe. I thought you might bring Descartes up...I'm a very firm believer in that statement. :)

Again, (and not trying to go too far off track) it depends on how we define consciousness. For instance, are you a complete materialist? Do you believe that every 'thought' that a person has involves a physical correlation? Is our thinking something that is 'on its own', or is merely a response to some other first cause that has so many variable it is considered to be practically 'unknown'?

For instance, I am at an ice cream stand, deciding what I want to get. Do I pick cherry because I have a 'mind' that says, "I want cherry" and then translates it into the physical act of choosing? Or is that act determined by genetic and environment, and my 'deciding' is only an illusion? Both answers have their pitfalls. :)

http://en.wikipedia.org/wiki/Philosophy_of_the_mind

Ps. Personally, I believe in the idea that physical objects arranged in a certain way can produce 'mental' properties.

The problem then becomes, "How do you know you're conscious?" If you say, "I know because I am thinking", then certainly, others around also seem to have 'consciousness' because they also think and respond to you.

 

[ttn]

It seems easy enough.

There are two purely random coins in the universe: A and B, and each may be flipped once. (For simplicity)

The joint distribution on the flips is given by:
P(HH) = 1/2
P(HT) = 0
P(TH) = 0
P(TT) = 1/2

I've not postulated a state of the universe, or any sort of collapse. I've simply posited the existence of a pair of random coins, and stated their joint probability distribution.

But you have simply asserted a summary of what is (taken to be) observed in the lab (so to speak). This is not a *theory*. *Of course* if you just say "X happens half the time" (etc.) there is no problem with locality or Lorentz invariance because you haven't actually *said* anything about anything. A theory (as I've defined it above in the context of defining Bell locality) is some candidate description of the physical world which includes some formalism that allows you to calculate the probabilities of possible happenings.

So I should reformulate the question: can anyone think of a *theory* which explains the coin-flipping results in a local or lorentz invariant way? Just repeating back what those results are, doesn't cut it.

 

[vanesch]

So I should reformulate the question: can anyone think of a *theory* which explains the coin-flipping results in a local or lorentz invariant way? Just repeating back what those results are, doesn't cut it.

I think you are here thinking of "a mechanism that can explain the randomness"... and as such should not be intrinsically random itself ; in other words, a deterministic mechanism.

What's wrong with say, have "stochastical" classical mechanics, where you have to add, at spacelike separated events, intrinsically random variables to the local equations of motion, but in such a way that these random variables are correlated ?

Of course, you can not find any DETERMINISTIC mechanism that can explain this correlation from an underlying "deterministic mechanics with lack of knowledge of the initial state" ; but if the intrinsically random variables are FUNDAMENTAL ? If you have no underlying mechanism, how are you going to require any statistical independence ?

As I tried to outline already a few times, the requirements you want to impose onto these intrinsic random variables are exactly such that they CAN be explained by an underlying deterministic theory where the randomness is a pure result from "ignorance of initial conditions".

 

[vanesch]

I would like to avoid too much delving into these philosophical issues for there own sake. I'm often forced into them here, because discussions around MWI usually start with misconceptions about those issues, which play a role in these views - and often lead to a "premature" rejection of an MWI view induced by conceptual errors in the philosophical view to adopt. I try hard to limit myself to what's relevant for the case at hand.

EDIT: oh, yes, and the reason why I "defend" the MWI view (or at least, fight the statement that it is a totally ridiculous view) is exactly the subject matter of this thread: the peaceful coexistence of relativity and Bell-type quantum phenomena with an ontological picture.

But you bring up of course a point which is of interest...

For instance, are you a complete materialist? Do you believe that every 'thought' that a person has involves a physical correlation?

I'm not a complete materialist, but something in between a property dualist http://en.wikipedia.org/wiki/Property_dualism and an epiphenomalist http://en.wikipedia.org/wiki/Epiphenomenalism.

Is our thinking something that is 'on its own', or is merely a response to some other first cause that has so many variable it is considered to be practically 'unknown'?

I think that our thinking is something that *finds it origin* in the physics, but that the (passive) subjective experience ITSELF is not purely part of physics as we know it. However, I don't think that this experience is active, in that it can intervene in the physical world. I think there is a physical phenomenon which makes my body utter the words "give me some cherry" ; but that the subjective experience that goes with it is generated by this body physics. My subjective experience passively undergoes what my body physics is doing.
This is why I think that behavioralism is missing the issue, because the (physical, observational) behaviour of a body is no indication at all for a subjective experience (qualia) that go with it or not.

For instance, I am at an ice cream stand, deciding what I want to get. Do I pick cherry because I have a 'mind' that says, "I want cherry" and then translates it into the physical act of choosing? Or is that act determined by genetic and environment, and my 'deciding' is only an illusion? Both answers have their pitfalls. :)

Yes, so I think it is the physics of my body that generates this "desire of cherry" and it are purely physical phenomena which make me "pick it", and I have the illusion of having made a decision.

This part is somehow necessary to "leave the physical ontology alone", and to allow for the split between a "purely physical ontology which has its physical laws" and then a "rule that determines how I derive my (passive) subjective experiences from that".

The problem then becomes, "How do you know you're conscious?" If you say, "I know because I am thinking", then certainly, others around also seem to have 'consciousness' because they also think and respond to you.

Well, I think we misread Descartes into "thinking as a problem solving intellectual activity". This is behavioural. I think that the "thinking" of Descartes meant "I have subjective experiences, qualia".

To illustrate this: prove me that a stone has no qualia. Prove me that it doesn't "hurt" a stone when I hit chips of it. You can't. At best you'll REDEFINE in an anthropocentric way what it means, to have subjective experiences, and then prove that there's no remote way in which there could be SIMILAR processes in a stone than in a human body. Sure, it must "feel" totally different to "be a stone" than to be "Joe Sixpack"

Again, I need a certain, limited, form of dualism, in order to specify things such that there is a physical ontology FROM WHICH my subjective experience is derived, and in such a way that this subjective world has no "influence" on the physical ontology. But there's still a lot of "wiggle room" to adapt it to your taste.

In fact, as much as I'm a fundamental reductionist concerning the physical ontology (in the Weinberg sense: that nature's ontology must correspond to a mathematical object, which describes _everything_ of that ontology), I might here incline to anti-reductionists, to say that subjective experiences might be an emerging phenomenon from certain physical structures, which is NOT described by the ontology itself (although all the ontology says about the physical structure is still entirely true - so there's no contradiction).

 

[Hurkyl]

But you have simply asserted a summary of what is (taken to be) observed in the lab (so to speak). This is not a *theory*.

No, this is my theory. In my theory, the probability distribution is a fundamental physical constant.

And besides, this is exactly what you were asking for: you were asking a theory about "irreducibly-random events", and further clarified by stating "a universe where the outcomes aren't based on any micro-hidden-details, but are genuinely irreducibly random".

So, in fact, the very conditions you've put forth require that there are no other physical variables that affect the outcomes of the coin flips -- the only property these coins have is their joint probability distribution!



This seems, to me, to completely fulfill the requirements you set forth. If you disagree, it would help greatly if you could put forth any theory that had irreducibly-random events in a universe where the outcomes aren't based on any micro-hidden-details, but are genuinely irreducibly random

So I should reformulate the question: can anyone think of a *theory* which explains the coin-flipping results in a local or lorentz invariant way? Just repeating back what those results are, doesn't cut it.

But if you're looking for any theory, we don't even have to be hypothetical. We could even take ordinary classical mechanics!

I can, right now, create two devices that will display either "H" or "T" when a button is pressed. I can give these to Alice and Bob, and they can press the buttons in whatever way they want, and when they compare notes, they will find they both got the same sequences of "H"s and "T"s.

 

[LnGrrrR]

Vanesch,

Yes, it's certainly interesting how QM can intrude (or at the least, walk hand in hand) with some forms of philosophy.

I myself lean towards property dualism. :)

I can not prove the qualia of a stone...but I also can't prove an invisible spaghetti monster lives on the planet Uranus. So I choose to assume that neither happens. :)

Thanks for the replies though. This is a 'pet topic' of mine.

 

[ttn]

No, this is my theory. In my theory, the probability distribution is a fundamental physical constant.

The probability distribution *of what*? You'll maybe say something like "the outcomes"... but what *are* these? What are they *made of*? What's actually *going on* in this scenario?

Is it really such a myserious surprise that there is a difference between saying "X happens" and providing a *theory* about X?

And besides, this is exactly what you were asking for: you were asking a theory about "irreducibly-random events", and further clarified by stating "a universe where the outcomes aren't based on any micro-hidden-details, but are genuinely irreducibly random".

A theory can provide some account of beables involved in the production of some "observable", and still include irreducibly random events. I'm not asking for a deterministic theory -- just some kind of theory with some kind of state descriptions and some kind of dynamics.

So, in fact, the very conditions you've put forth require that there are no other physical variables that affect the outcomes of the coin flips -- the only property these coins have is their joint probability distribution!

Maybe the problem is that the example is too silly. But the main point here is that my conditions *don't* "require that there are no other physical variables that affect the outcomes..." Indeed, I don't see how you can propose a theory without talking about, well, *some* variables. An example would be orthodox QM: the collapse postulate involves irreducible randomness, yet it is part of a theory which proposes a definite state description and definite dynamics. So what you need is an example of something like that -- but something that doesn't violate Bell Locality.

This seems, to me, to completely fulfill the requirements you set forth. If you disagree, it would help greatly if you could put forth any theory that had irreducibly-random events in a universe where the outcomes aren't based on any micro-hidden-details, but are genuinely irreducibly random.

Orthodox QM w/ collapse postulate. Only, make the collapse occur along future-light-cone out from the measurement event so it doesn't violate Bell Locality. That would be a local theory w/ irreducible randomness. (But of course it isn't empirically viable.)

I can, right now, create two devices that will display either "H" or "T" when a button is pressed. I can give these to Alice and Bob, and they can press the buttons in whatever way they want, and when they compare notes, they will find they both got the same sequences of "H"s and "T"s.

Sure you can do this. But what does this have to do with Bell Locality? Perhaps you've forgotten that Bell Locality speaks not of subjective probabilities but of probabilities assigned by a theory. And it doesn't count to say "my theory is that there's nothing actually going on" -- i.e., "my theory is that there is no theory."

 

[ttn]

I think you are here thinking of "a mechanism that can explain the randomness"... and as such should not be intrinsically random itself ; in other words, a deterministic mechanism.

You're half right. I'm thinking of what might as well be called "a mechanism that can explain"... but the point is not to explain the randomness (in terms of an underlying deterministic mechanism) but just to explain the results. This is nothing special. It's called having a theory about what's going on (as opposed to just shrugging and saying "this particle detector over here ended up firing at a certain moment; oh well; I guess that's just an irreducible inexplicable fact").

What's wrong with say, have "stochastical" classical mechanics, where you have to add, at spacelike separated events, intrinsically random variables to the local equations of motion, but in such a way that these random variables are correlated ?

I have no objection to injecting random variables into the dynamics. What I object to is picking a random number and then simultaneously injecting it into the dynamics of two spatially separated regions.

Of course, you can not find any DETERMINISTIC mechanism that can explain this correlation from an underlying "deterministic mechanics with lack of knowledge of the initial state" ; but if the intrinsically random variables are FUNDAMENTAL ? If you have no underlying mechanism, how are you going to require any statistical independence ?

Maybe this is what's causing the disagreement here. You seem to think that "irreducible randomness" means there's "no underlying mechanism." I'm willing to accept candidate descriptions of underlying mechanisms (i.e., *theories*!) which involve irreducible randomness.

For example, I think Orthodox QM is perfectly well a "theory" in the sense I'm insisting on. It provides an account of what's going on behind the scenes to produce something like a detector firing. And what I don't like about that theory is *not* that half of its dynamics isn't deterministic. The "problem" (in this context) is that this half of the dynamics is nonlocal. It says that an irreducibly random event at one place has an instantaneous effect at other places.

Do people think that the whole notion of "causal influence" is absent/meaningless in a non-deterministic theory? Maybe that's the source of the trouble here...

 

[selfAdjoint]

The "problem" (in this context) is that this half of the dynamics is nonlocal. It says that an irreducibly random event at one place has an instantaneous effect at other places.

Do people think that the whole notion of "causal influence" is absent/meaningless in a non-deterministic theory? Maybe that's the source of the trouble here...

The problem is that "orthodox quantum mechanics" doesn't say that, and does have a perfectly good relativistic notion of causality. It says that you only see the correlation after the fact, and that the correlation isn't because the one event caused the other, because there is no causality between spacelike separated events. It all hangs together and gives correct predictions, but you have to take to heart the old saying "Correlation is not causation."

 

[ttn]

The problem is that "orthodox quantum mechanics" doesn't say that, and does have a perfectly good relativistic notion of causality. It says that you only see the correlation after the fact, and that the correlation isn't because the one event caused the other, because there is no causality between spacelike separated events. It all hangs together and gives correct predictions, but you have to take to heart the old saying "Correlation is not causation."

In orthodox QM, the state description of one object (or, in one region) *changes* as a result of a measurement on some other object (in some other region). One can of course always say "Oh, you shouldn't take those state descriptions literally." Well, OK. But not taking the descriptions as literal does not change the fact that *if* those descriptions are literally correct ("complete") descriptions of the real world, then the real world contains relativity-violating causal influences. That's just what the theory *says*, and frankly I find it ridiculous that so many otherwise reasonable people are able to get lulled into the cognitive trap of simply denying the literal truth of the theory as a way of avoiding this implication. The fact is, orthodox QM provides a candidate description of the world and dynamics for it, and this combination -- this theory -- is nonlocal (in the specific sense of violating Bell Locality).

A given person may or may not be troubled by this fact, depending on whether or not he thinks this theory is true. (If you don't think OQM is true, then there's no reason to worry about its conflicting with relativity.) But then, you have to face the obvious next question: what theory *is* true? Anybody who is not interested in asking and answering this question is, in my opinion, no physicist.

As to "correlation is not causation", the point of this old saying is that you can't infer, from the mere observed correlation of A and B, that A causes B. But this has precisely nothing to do with what we're talking about here. Yes, it's notoriously difficult to validly infer causal relationships from observation. But the whole beauty of Bell Locality is that we don't have to try to do this, because the criterion isn't *about* observed correlations (or "subjective probabilities" as I keep saying). It's about the predicitons of *theories*. And it is notoriously UN-difficult -- notoriously *easy* -- to validly infer causal relationships from *theories*, because (by virtue of what it means to be a theory in the first place) theories simply *tell* us what causal relationships exist.

This is an absolutely fundamental point to this discussion, and there's no point talking about anything else until this is clear. Nobody is saying that you can look at some empirical fact (like Alice's and Bob's outcomes are correlated in a certain way) and infer that there is some spooky superluminal causation going on. The claim is that you can look at a *candidate theory* (like OQM or Bohmian Mechanics or whatever) and infer that, according to this theory, there is or is not spooky superluminal causation going on. To be confused about this point, is the same about being confused about the distinction between Bell Locality and Signal Locality. (A violation of the latter *can* be directly inferred from observed correlations; a violation of the former cannot.)

 

[selfAdjoint]

In orthodox QM, the state description of one object (or, in one region) *changes* as a result of a measurement on some other object (in some other region).

Orthodoxly the state function doesn't exists in any region of spacetime. What exists is a measurement, the result of a preparation and an action. Those are events in spacetime. And the time relations of spacelike events are indeterminate. So what you're saying here is violating both QM and relativity.

 

[ttn]

Orthodoxly the state function doesn't exists in any region of spacetime. What exists is a measurement, the result of a preparation and an action. Those are events in spacetime. And the time relations of spacelike events are indeterminate. So what you're saying here is violating both QM and relativity.

This point has already been covered. There are simply two possible version of "orthodox QM". One (perhaps closer to von Neumann's ideas, although Bohr's insistence on the completeness doctrine makes me think this is close to Bohr's views too) is that the wave function provides a literal and complete description of physical states, with two different dynamical laws depending on whether or not a measurement is being made. The other possible view is to take the whole quantum formalism as an empty black-box algorithm for predicting measurement outcomes. This latter may or may not constitute a theory (in the relevant sense) depending on whether or not its advocate is claiming *ignorance* about real goings-on at the sub-microscopic level, or, rather, is claiming that there are no such goings on (i.e., that *the only thing that exists are readings on measurement devices* -- a view that to me is too preposterous to take seriously since it contradicts pretty much everything discovered by scientists in the last 200 years).

 

[vanesch]

I have no objection to injecting random variables into the dynamics. What I object to is picking a random number and then simultaneously injecting it into the dynamics of two spatially separated regions.

Why ?

Maybe this is what's causing the disagreement here. You seem to think that "irreducible randomness" means there's "no underlying mechanism." I'm willing to accept candidate descriptions of underlying mechanisms (i.e., *theories*!) which involve irreducible randomness.

Yes, but you place extra limits on how this irreducible randomness can be applied. For instance, what's indeed wrong with using the SAME (or correlated) *intrinsic random numbers" at two spatially separated events ? If these numbers have no ontology attached to them, and are fundamental quantities, I don't see why this should be forbidden. Them not having a *mechanism* in them, there's no "causality" involved in this. It "just happens that way". This is the essence of an intrinsically fundamental stochastical theory, no ? "things just happen this way".

For example, I think Orthodox QM is perfectly well a "theory" in the sense I'm insisting on. It provides an account of what's going on behind the scenes to produce something like a detector firing. And what I don't like about that theory is *not* that half of its dynamics isn't deterministic. The "problem" (in this context) is that this half of the dynamics is nonlocal. It says that an irreducibly random event at one place has an instantaneous effect at other places.

Well, this is only true in the case that one assigns some reality to the concept of the wavefunction ; not if it is an "algorithm to calculate probabilities", right ?

Do people think that the whole notion of "causal influence" is absent/meaningless in a non-deterministic theory? Maybe that's the source of the trouble here...

I think that there is a total absense of the notion of causal influence in THE STOCHASTICAL ELEMENT of an *intrinsically* non-deterministic theory. That doesn't mean that the theory as a whole does not have elements of causality to it: the "deterministic part" (the evolution equations of the ontologically postulated objects) does have such a thing of course. But the "random variables" that are supposed to describe the intrinsic randomness of the whole don't have - a priori - to obey any kind of rules, no ?

 

[Hurkyl]

The probability distribution *of what*? You'll maybe say something like "the outcomes"... but what *are* these? What are they *made of*? What's actually *going on* in this scenario?

In my theory, the outcomes "H" and "T" are fundamental things. They cannot be analyzed any further. The thing I call a "probability distribution" is a fundamental quantity.

The term "probability" is justified for the following reasion:

Suppose we had many pairs of coins whose "joint probability distribution" factors into the "probability distributions" on the pairs. (Where, again, P(HH) = P(TT) = 1/2 and P(TH) = P(HT) = 0 for the two coins in a pair)

Then, this "probability distribution" gives a value of nearly one to the set of outcomes where roughly half of the pairs of coins flip to HH and rest flip to TT.

So, my "probability distribution" really does give probabilities -- it satisfies the frequentist interpretation of probabilities.

Is it really such a myserious surprise that there is a difference between saying "X happens" and providing a *theory* about X?
...
Maybe the problem is that the example is too silly.

But yet, there is a theory that says nothing more than "X happens". The class of theories is very broad, and includes lots of dumb, ridiculous, uninteresting, unrealistic, and impractical things.

But yet, they're all still theories.

I'm not asking for a deterministic theory -- just some kind of theory with some kind of state descriptions and some kind of dynamics.

Fine -- flesh the rest out however you want. Let's make the coins Special Relativistic point particles, and each can be in one of three fundamental states: "H, T, and unflipped". The initially start out as "unflipped", and via an interaction called "flipping" can transition to "H" or "T". The transition is nondeterminsitic, and is governed by the joint probability distribution P(TT)=P(HH) = 1/2, P(TH) = P(HT) = 0. This joint probability distribution is a fundamental constant of the theory.


More details just obscures the point -- the theory is simple and clear. It doesn't have messy details to work through and understand, and it's manifestly Lorentz invariant.

If you really needed me to, I'm sure I could flesh this out to work with many coins and additional interactions, such as ways to revert a coin back to the "unflipped state" and a pairwise interaction on coins called "entanglement", but that would just obscure what's going on, and I don't think I'd be doing anything more than a nondeterministic variation of classical mechanics without the axiom that spatially separated probabilities are statistically independent.

Sure you can do this. But what does this have to do with Bell Locality?

It has to do with what you had asked in the paragraph I quoted.




Incidentally, another way to go is to assert that observations are random variables. And not the silly stuff we learned as kids: I'm saying that observations are like the random variables defined in mathematical statistics.

Observations are probabilitiy distributions on a space of outcomes, nothing more. In particular, observations never actually "take on" the value of a particular outcome.

 

[selfAdjoint]

This point has already been covered. There are simply two possible version of "orthodox QM". One (perhaps closer to von Neumann's ideas, although Bohr's insistence on the completeness doctrine makes me think this is close to Bohr's views too) is that the wave function provides a literal and complete description of physical states

You say you have been over it, but you keep coming back to the same issues. What does "literal and complete" mean? A map can provide a complete description of a town; every street, every address, is there; but the map is still not the town, and the space of quantum states is still not in spacetime.