The reality of Configuration space

[DevilsAvocado]

:zzz:

 

[eloheim]

Great post bohm2, thanks for supplying all those links and the respective summaries. Obviously you've done some homework on the topic. An interesting book I read, some time ago, on these aspects of Philosophy of Science is called Physics as Metaphor, by Roger Jones. Perhaps I can dig up some relevant passages.

Also, I know the following has been mentioned in this thread, but I don't see a link: Direct measurement of the quantum wavefunction.

And DevilsAvacodo's illusion is awesome!

 

[Ken G]

:zzz:

This is your response to being shown that you are mistaken about Bell's theorem? Which is it-- do you not care that your claim that Bell disproves local realism rather than just locality is contradicted by Bell's own words, or do you not understand that your claim is thus contradicted? To the rest, who do care and can understand, they should note well the quotes that bohm2 provided-- for it is all too common for "commentators" to claim that you can retain locality if you drop realism, but Bell himself has pointed out that he never even assumed realism in his theorem!

 

[DevilsAvocado]

:zzz: ²

 

[DevilsAvocado]

And DevilsAvacodo's illusion is awesome!

Thanks eloheim!

It could be very useful for anyone claiming to be in possession of a "divine consciousness" setting "the rules" for the universe/reality. Let’s run it again!

Stare at the center cross for at least 30 seconds to experience
the three phenomena of the illusion

We are all grand indeed and made out of stardust, literally, but that little 'grey clump' is sometime 'buggy' and we do obviously not have the 'CPU power' to get it right all the time (which is crucial for a coherent universe).

 

[Ken G]

Anyway, getting back to the thread, the claim on the table is this: configuration space is "more real" whenever the scientist has their reasons to regard it as such, and similarly for three-space. There is absolutely no need to say anything more, scientifically speaking-- all that remains is to account for those reasons. The main reasons to choose to regard configuration space as more real seem to center around the fact that our best theories of classical and quantum physics borrow from a mathematical structure that invokes configuration space. The main reasons to choose to regard three-space as more real is that it connects better with how we perceive the world using our senses.

Then the natural question is, why are these not the same? My answer to that is, why should they be-- when nothing in science requires that either be regarded as the actual reality, then nothing in science suggests that they ought to be the same. The argument that it is strange that they are not the same seems to always boil down to some version of "anything that works out to be the truth", but the history of science is so clearly counter to that proposition I hardly think we need to give it any credence.

 

[bohm2]

Anyway, getting back to the thread, the claim on the table is this: configuration space is "more real" whenever the scientist has their reasons to regard it as such, and similarly for three-space. There is absolutely no need to say anything more, scientifically speaking-- all that remains is to account for those reasons.

I think it's guided partly by my reductionist and monist/simplistic biases. But mostly by the "strangeness" for someone who is a bit of a deBroglie/Bohmian admiror but doesn't like the dualism. Monton describes it well where he writes:

I have nothing definitive to say about this ontology, other than that it strikes me as strange. We have two disconnected spaces, with presumably no causal connection between the particles in the one space and the field in the other space, and yet the stuff in the two spaces is evolving in tandem. Presumably there is a nomic connection between the stuff in the two spaces, which supports counterfactuals of the following form: if the stuff in one space had evolved differently, the stuff in the other space would have evolved differently. But having that nomic connection without a causal connection makes it all the more mysterious how these spaces are associated with each other.

http://spot.colorado.edu/~monton/BradleyMonton/Articles_files/qm%203n%20d%20space%20final.pdf

It reminds me very much of the "mind-body problem" in philosophy. With respect to the latter, it might be that this "hard problem" is "chronic and incontrovertible"? In fact, it might be as you suggested, that the problem has its source as some special feature of consciousness, itself; that is, by having this special access (inner experience) to it that we have to nothing else (and nothing else to us), this may not allow us to see the connection? The problem source lies at the gate as has been argued by quite a few authors.

Anyway, with respect to the former, I still found Einstein's quote on this issue interesting:

The method of Schrödinger seems indeed more correctly conceived than that of Heisenberg, and yet it is hard to place a function in coordinate space and view it as an equivalent for a motion. But if one could succeed in doing something similar in four-dimensional space, then it would be more satisfying.

Of the new attempts to obtain a deeper formulation of the quantum laws, that by Schrödinger pleases me most. If only the undulatory fields introduced there could be transplanted from the n-dimensional coordinate space to the 3 or 4 dimensional!

In one paper, Wallace and Timpson have suggested 3-dimensional space emergence from 3-N-dimensional space (that may have some utility in MWI, Bohmian, GRW) but I don't think it's very convincing but what do I know:

It is also worth keeping in mind that many workers in quantum gravity have long taken seriously the possibility that our four-dimensional spacetime will turn out to be emergent from some underlying reality that is either higher-dimensional (as in the case of string theory) or not spatiotemporal at all (as in the case of loop quantum gravity). In neither case is it suggested that ordinary spacetime is nonexistent, just that it is emergent.

http://arxiv.org/PS_cache/arxiv/pdf/0907/0907.5294v1.pdf

A video series (4 parts) by Tumulka discussing this paper (apparently Wallace did not show up because of a Volcanic explosion):


http://wn.com/Tumulka_2

http://wn.com/Tumulka_4 (in this section Tumulka criticizes Wallace's model and begins discussing his own views)

 

[Ken G]

Those are interesting insights. I think my issue would be, we first must have a coherent meaning for the term "existent." In science, it is just perfectly clear that what is said to exist is whatever it serves us to say exists, in some context. Why people refuse this obviously true fact amazes me! Once we stipulate this, it is not really saying much of anything to say that 3d space "emerges from" some configuration space, since they are both claims on what exists strictly because they serve us to make that claim, and so they both "emerge" from those goals or ours, and if there is some connection between those emergences, we could say one emerges from the other (not literally, just in how we are understanding the situation). The claim does not require that these things actually exist in any other sense (what sense would that be?), or even that we have any way to say what "actually exists" even means, other than the meaning I've already given for it. I challenge anyone to give any other scientifically defensible meaning for what actually exists!

For one thing, it is easy to show that science invokes the existence of things that we know do not actually exist, this is quite routine. Action at a distance in Newtonian gravity is a completely random example. But some might hold that these are the things that are just models, and don't really exist, which are to be distinguished from the models that actually do exist, as if that phrase even made sense. They might hold that any model that has not been refuted by some more accurate measurement represents something that actually exists. Well, if it represents what exists, then it isn't what exists, so we first have to get rid of "represents" if we want to defend the claim. Then, we must also maintain that no future observation will ever refute the model, such that the modeled thing can be something that actually exists. To do this, we must forget what it is to be a scientist.

 

[bohm2]

Once we stipulate this, it is not really saying much of anything to say that 3d space "emerges from" some configuration space, since they are both claims on what exists strictly because they serve us to make that claim, and so they both "emerge" from those goals or ours, and if there is some connection between those emergences, we could say one emerges from the other (not literally, just in how we are understanding the situation).

The problem is that such a mapping can't be done in any unique way, because when one tries to do it, the structure of the field can underwrite more than one set of emergent 3-spaces. MW1 don't have a problem with this because they argue that more than one set of emergent 3-spaces exist at the same time.

An interesting quote by Hiley on this issue and his/Bohm's conclusion that there is likely something "deeper" underlying this wave-particle duality in QM:

Bohm draws attention to what he calls 'a serious problem' that confronts us when the theory is extended to deal with more than one particle. The problem with N particles is that the wave function is not in ordinary 3-dimensional space, but instead, in an abstract 3N-dimensional configuration space. While of course this space is logically consistent, the concept of a wave in a 3N-dimensional space is far from physically obvious. At this stage Bohm simply regarded his proposals as an artifice that could be used provisionally until a better theory emerges "in which everything is expressed once more in ordinary 3-dimensional space". This problem of configuration space was eventually resolved by introducing the notion of 'active information' . However there remains a deeper problem as Bohm points out:

Finally, our model in which wave and particle are regarded as basically different entities, which interact in a way that is not essential to their modes of being, does not seem very plausible. The fact that wave and particle are never found separately suggests instead that they are both different aspects of some fundamentally new kind of entity which is likely to be quite different from a simple wave or a simple particle, but which leads to these two limiting manifestations as approximations that are valid under appropriate conditions.

http://www.bbk.ac.uk/tpru/BasilHiley/History_of_Bohm_s_QT.pdf

 

[Ken G]

I would especially underscore this part: "The fact that wave and particle are never found separately suggests instead that they are both different aspects of some fundamentally new kind of entity which is likely to be quite different from a simple wave or a simple particle, but which leads to these two limiting manifestations as approximations that are valid under appropriate conditions."
That is more or less what I have been saying all along, except not just for particles and waves, but for all of science. I really don't see why we should ever expect anything different, both on theoretical grounds, and based on our experiences in science.

 

[bohm2]

This is an interesting argument by Lockwood on this issue:

Do we therefore have no genuine knowledge of the intrinsic character of the physical world? So it might seem. But, according to the line of thought I am now pursuing, we do, in a very limited way, have access to content in the material world as opposed merely to abstract casual structure, since there is a corner of the physical world that we know, not merely by inference from the deliverances of our five sense, but because we are that corner. It is the bit within our skulls, which we know by introspection. In being aware, for example, of the qualia that seemed so troublesome for the materialist, we glimpse the intrinsic nature of what, concretely, realizes the formal structure that a correct physics would attribute to the matter of our brains. In awareness, we are, so to speak, getting an insider's look at our own brain activity.

http://plato.stanford.edu/entries/neutral-monism/#7.2

I find it interesting because it seems to imply how little we really do know about "matter"/the "physical" and how much further we need to go to get "material"/neural stuff (as presently understood) to spit out mental stuff. Strawson's insight seems very powerful to me regarding the mind-body problem:

For many take this to be the problem of how mental phenomena can be physical phenomena given what we already know about the nature of the physical. And this is the great mistake of our time. The truth is that we have no good reason to think that we know anything about the physical that gives us any reason to find any problem in the idea that mental or experiential phenomena are physical phenomena...

But I still can't see what "theoretical inference from the character of phenomenal properties" will allow us to progress on this issue. McGinn has put this argument forth but I'm not sure what to make on it:

If we need a pre-spatial level of reality in order to account for the big bang, then it may be this very level that is exploited in the generation of consciousness. That is, assuming that remnants of the pre-big bang universe have persisted, it may be that these features of the universe are somehow involved in engineering the non-spatial phenomenon of consciousness. If so, consciousness turns out to be older than matter in space, at least as to its raw materials.

I'm guessing here that McGinn is saying that mental stuff isn't spatial. One won't find mental stuff by "looking" at neural stuff. This non-spatiality also arguably gave "birth" to the big-bang. But I'm not sure if this "remnant argument" is a very convincing one; nevertheless, it is an interesting one (to me).

 

[Ken G]

There aren't any logical errors in those quotes, but to me they are all trying very hard to shoehorn some prejudicial expectation into our models of the physical world. They seem to want so badly for physics knowledge to be "genuine knowledge of our world", but I don't think the distinction between effective knowledge, and genuine knowledge, has any meaning at all. All we get, with knowledge, is ranges of effectiveness, and every one of those commentators is drawing some arbitrary line and saying "beyond here the knowledge is genuine." It's so much more empowering to just recognize that it is not the nature of knowledge to be genuine. Even a logical proof is not genuine knowledge, it is a logical connection between the axioms and their ramifications-- but the ramifications are not "genuine" because the axioms are not. I'd like to hear how Lockwood can define "genuine" in any way different from "matching my expectations and prejudices about what knowledge ought to be." But we don't have knowledge for that reason, we have it because it works-- and that is even true of logic. The relevance to configuration space and 3-space is clear: they both represent different types of effective knowledge that for completely mysterious reasons work in various ways for describing reality.

 

[bohm2]

An abstraction guides a particle? That doesn't sound coherent. I know Bohm's views are generally self-consistent, so I'm not sure where he got this idea from. He has the pilot wave to guide the particles, but I would have to say that the pilot wave doesn't actually guide anything, the particles behave as if guided by the pilot wave-- that way our concepts are not pushing particles around in anything but how we think about the particles.

There seems to be a major difference (metaphysical) between Bohm/Hiley versus other "Bohmians" with respect to the quantum potential, I think, as Hiley notes in this quote.

To summarise this section then, let me emphasise that the differences between the advocates of Bohmian mechanics and our own approach is not about the need to have a account of the actual, but about what form this account should take. Clearly such a choice is largely decided by what each group regards as an acceptable physical explanation. There is no dispute about the form of the equations. Where Bohm and I differ from many advocates of Bohmian mechanics is the attitude we adopted to the formalism. Our long period of working with the formalism and reflecting on how it works has led us to believe that rather than a simple return to a mechanistic picture something much more subtle is involved. We tried to bring this out in our book but clearly we have not got across our message!

Some of these "Bohmians" Hiley refers to (e.g. Goldstein, Durr. etc.) question the concept of "quantum potential" (as presented by Bohm) partly because of it's "bizarre properties" which include some of the following:

1. The quantum potential has no external source so that there is nothing for the particle to 'push against'. The energy is internal so it's role "is more like the role the gravitational field plays in general relativity where the gravitational energy curves space-time itself."

2. The quantum potential does not arise directly from the Hamiltonian and therefore does not appear explicitly in the algebraic equations (8) and (9)(see links for equations). The quantum potential only appears when we project equation (9) into a particular representation space. This is even more like gravitation where the 'force' appears only when we project the geodesics into a Euclidean space. It is only in this space that we see the deflected trajectories revealing the presence of the gravitational force.

3. The quantum potential is not changed by multiplying the field, ψ by a constant. This can be seen by examining the mathematical form of the quantum potential given by equation... This means that the quantum potential is independent of the magnitude of ψ and so is independent of the field intensity. This in turn means that its effect can be very large even when the amplitude of the field is very small. Because of this, the effect of the potential need not fall off as the distance increases and this is just the property required for an explanation of the EPR correlations.

4. Because there is nothing to push against we should not regard the quantum potential as giving rise to an efficient cause, ('pushing and pulling') but it should be regarded more in the spirit of providing an example of Aristotle’s formative cause...The form is provided from within but it is, of course, shaped by the environment...The quantum potential carries information about the environment in which the particle finds itself. For example, in the electron two-slit experiment, the quantum potential carries information about the two slits, their size, shape and distance apart. Thus it carries information about the whole experimental arrangement. Thus the quantum potential reflects the experimental conditions...it is important to emphasise once again that our concept of information is not 'information for us' but objective information for the particle...

From the Heisenberg Picture to Bohm: a New Perspective on Active Information and its relation to Shannon Information
http://www.bbk.ac.uk/tpru/BasilHiley/Vexjo2001W.pdf

Active Information and Teleportation
http://www.bbk.ac.uk/tpru/BasilHiley/ActInfoTeleWein.pdf

 

[qsa]

I totally agree with 3, but 4 I disagree with strongly.

 

[bohm2]

I totally agree with 3, but 4 I disagree with strongly.

Yes, because it's implications suggest giving "particles"/matter far more intrinsic complexity than we currently are willing to do. Actually Bohm in some of his writings does suggest this. I think he wants physics to somehow explain the emergence of mental stuff/consciousness from stuff that physicists look at.

He writes:

There are many analogies to the notion of active information in our general experience. Thus, consider a ship on automatic pilot guided by radar waves. The ship is not pushed and pulled mechanically by these waves. Rather, the form of the waves is picked up, and with the aid of the whole system, this gives a corresponding shape and form to the movement of the ship under its own power. Similarly, the form of radio waves as broadcast from a station can carry the form of music or speech. The energy of the sound that we hear comes from the relatively unformed energy in the power plug, but its form comes from the activity of the form of the radio wave; a similar process occurs with a computer which is guiding machinery. The 'information' is in the program, but its activity gives shape and form to the movement of the machinery. Likewise, in a living cell, current theories say that the form of the DNA molecule acts to give shape and form to the synthesis of proteins (by being transferred to molecules of RNA).

Our proposal is then to extend this notion of active information to matter at the quantum level. The information in the quantum level is potentially active everywhere, but actually active only where the particle is (as, for example, the radio wave is active where the receiver is). Such a notion suggests, however, that the electron may be much more complex than we thought (having a structure of a complexity that is perhaps comparable, for example, to that of a simple guidance mechanism such as an automatic pilot). This suggestion goes against the whole tradition of physics over the past few centuries which is committed to the assumption that as we analyze matter into smaller and smaller parts, their behaviour grows simpler and simpler. Yet, assumptions of this kind need not always be correct. Thus, for example, large crowds of human beings can often exhibit a much simpler behaviour than that of the individuals who make it up.

He goes further in Chapter 15 of “The undivided universe” where he and Hiley write:

It is thus implied that in some sense a rudimentary mind-like quality is present even at the level of particle physics, and that as we go to subtler levels, this mind-like quality becomes stronger and more developed...At each such level, there will be a 'mental pole' and a 'physical pole'. Thus as we have already implied, even an electron has at least a rudimentary mental pole, represented mathematically by the quantum potential. Vice versa, as we have seen, even subtle mental processes have a physical pole. But the deeper reality is something beyond either mind or matter, both of which are only aspects that serve as terms for analysis.

http://books.google.ca/books?id=vt9...m=3&sqi=2&ved=0CCwQ6AEwAg#v=onepage&q&f=false
http://www.tcm.phy.cam.ac.uk/~mdt26/local_papers/bohm_mind_matter_1990.pdf

Further in Ontological basis for the Quantum theory (see-‘Extension to the many-body system’ (p.330-332 of link) he argues that this can be extended upwards for some complex systems with the "right" configurations (e.g. superconductivity, living organisms, etc.). So if I understand him correctly he is interpreting the quantum potential as a mental pole that can’t be measured (like the mental) but can be inferred via the behaviour of the physical pole (e.g. particle) which is picked up by our measurements. So the quantum potential for Bohm is really an information/proto-mental space that guides the particle? So it’s "real"/causal but not in the typical "physical" sense? I'm not sure how this is possible giving Tegmark's calculations?

http://www.tcm.phy.cam.ac.uk/~mdt26/local_papers/bohm_hiley_kaloyerou_1986.pdf

I think physicists in general eschew this type of speculation but I find it interesting because we do have a major problem in philosophy regarding solving the "hard problem" (mind-body problem). There doesn't seem to be any hope of unification within the current models in physics. Some have argued that emergence/novelty may allow mental stuff to arise out of more fundamental entities that we study in physics (whatever those may be) but I'm doubtful that physics has anything to say about such stuff up to this point.

 

[Ken G]

What interests me about all this is how close to full circle the thinking has come. Originally, Bohmian mechanics was sold as the closest to classical realism, where particles are governed by hidden semi-classical properties that lie below the surface of what we can currently probe, but which are otherwise similar to Newtonian determinism. But these writings show how Bohm has come to think of the simple particle as a kind of information processor, which to me is a pretty clear example of how we project our own thinking onto what we imagine is ruled somehow separately from our thoughts. We want to imagine that the rules of behavior of nature are independent of how we think about them, but when an electron is being somehow treated as if it had a mind of its own, I'd say it's pretty clear that we are doing what we should have always expected we wuold do: looking into a mirror when we contemplate the ontology of electrons. That's why I feel that any scientific ontology must be viewed as fundamentally filtered by how we think and perceive, and hence quite far divorced from anything we might safely consider a true ontology independent from us. I see no reason to object to this on the grounds that such a situation would not allow our science to be effective and accurate.

 

[qsa]

My interpretation of their idea is that we typically start from the small physics and we work our way to the human consciousness. but they look at it the other way around. While this has shed some good light on the problem, but still we have to work in the normal way. I don't see a way around it.

It is strange, but as a matter of fact I was having similar idea trying to answer my own question from the other thread (since no one took me up on it)



a Circle would be concidered an ontic entity and so are the numbers 4 ,100, ...

but the circle must be described in some way and there are multiples of them and so are the numbers ( 1+3=4, 2+2=4 ... ). SO, are the descriptions themselves are ontic or epistemic?

 

[bohm2]

Originally, Bohmian mechanics was sold as the closest to classical realism, where particles are governed by hidden semi-classical properties that lie below the surface of what we can currently probe, but which are otherwise similar to Newtonian determinism. But these writings show how Bohm has come to think of the simple particle as a kind of information processor, which to me is a pretty clear example of how we project our own thinking onto what we imagine is ruled somehow separately from our thoughts. We want to imagine that the rules of behavior of nature are independent of how we think about them, but when an electron is being somehow treated as if it had a mind of its own, I'd say it's pretty clear that we are doing what we should have always expected we wuold do: looking into a mirror when we contemplate the ontology of electrons.

Yes, but most physicists who support the Bohmian picture accept it without the metaphysical baggage. I'm thinking Goldstein, Valentini, Holland, etc. I think here Bohm is trying to infer "intrinsic" properties to matter but as Russel and Eddington pointed out, this is arguably beyond physics, I think; although, it does seem reasonable to think that dispositional properties stem from some underlying intrinsic properties of which we know absolutely nothing about (except our brains as Lockwood argues above). It seems this is the position held by structural realists also:

Science only reveals the causal / relational properties of physical objects, and that "we know next to nothing about the intrinsic nature of the world. We know only its causal/relational nature."

http://plato.stanford.edu/entries/structural-realism/

Stoljar also argues similarly as pointed out in this review:

Physics can tell us only about the dispositional or relational properties of matter, but since dispositions ultimately require categorical properties as bases, and relations ultimately require intrinsic properties as relata, there must also be categorical or intrinsic properties about which physics is silent. Yet these are properties of physical objects and thus are physical properties in one central sense. Instantiations of such properties would therefore constitute physical facts of which we are ignorant, as per the ignorance hypothesis.

http://www.uriahkriegel.com/downloads/slugfest.pdf

So, I'm guessing Bohm is leaping the gun but would probably be sympathetic to this argument:

We might put the argument in another way, as follows. Matter must have an intrinsic nature to ground its dispositional properties. We know nothing of this nature, and in fact the only intrinsic nature with which we are familiar is consciousness itself. It is arguable that we cannot conceive of any other intrinsic nature because our knowledge of the physical is entirely based upon its dispositions to produce certain conscious experiences under certain conditions. Of course, we can assert that matter has a non-experiential intrinsic nature which is utterly mysterious to us, but this would seem to make the problem of emergence yet more difficult. An emergentism which made the generation of consciousness intelligible would be one that showed how experience emerged from what we know about matter, that is, from its dispositional properties. But it seems impossible to see how the dispositions to move in certain directions under certain conditions could give rise to or constitute consciousness, save by the kind of brute and miraculous radical emergence discussed above. If granting some kind of experiential intrinsic aspect to the fundamental physical entities of the world eliminates this problem, it might be worth the cost in initial uncomfortable implausibility.

http://www.scar.utoronto.ca/~seager/pan_seager.pdf

 

[Ken G]

a Circle would be concidered an ontic entity and so are the numbers 4 ,100, ...

but the circle must be described in some way and there are multiples of them and so are the numbers ( 1+3=4, 2+2=4 ... ). SO, are the descriptions themselves are ontic or epistemic?

I would say the key is how physics borrows from mathematics, so the separate goals of physics and mathematics is crucial to recognize before discussing their ontologies. The situation in mathematics is very clear-cut-- the epistemology is pure logic and the ontology is the axioms, which can be whatever the mathematician chooses as long as they are not inconsistent. In short, consistency of the ontology is all that matters. But in physics, the ontologies have to be supported by evidence from nature, which is a double-edged sword. The good part of that is that the scientist receives guidance about what is a good ontology, and can demonstrate their successes. The bad part is that nature does not necessarily involve anything that we would recognize as a mathematical ontology, so ontologies in physics are more like templates that we borrow from some mathematical system and then lay over nature to see how well they fit. That is demonstrably what physics does, one can imagine all kinds of reasons for why it works but one should not ignore what one is actually doing.

 

[Ken G]

Stoljar also argues similarly as pointed out in this review:

I think structural realism is a basically solid stance, albeit a bit vague, but its vagueness does come with a potential pitfall-- it is easy to extrapolate to additional assumptions that are not necessarily required in structural realism. The issue is, what constitutes a structure anyway? If I create a theory that interprets nature as comprising of particles and fields, and these particles and fields have various properties in my theory, and I get excellent results, the structural realist says that my success proves that reality must have some intrinsic character that is similar to that basic structure. But what is the structure there? Is it the particles and fields, or their properties, or both? Or none of those? Let's say I come up with a different theory that does not use either particles or fields, but path integrals of some kind. let's say. I get all the same predictions, so my theory has the same "structure." But it doesn't have the same elements or properties of those elements! So what is the "structure" that is "real" anyway?

The Stoljar quote gets to an even deeper potential problem. A structural realist might hold that the structure is not the elements or their properties, but some sort of relational pattern that can be expressed with many different types of elements and properties. But Stoljar appears to make the implicit and potentially unjustified assumption that any structural realist must hold that reality is determined by its properties, even if we don't or can't know what those properties are. I would call that reductionist realism, not structural realism, because it reverses the direction of the logic. Structural realism takes the properties of successful models and projects them back onto reality, concluding that something in the model resonates with the reality in some vague but important way. Reductionist realism starts with the reality, and imagines constraints on it (properties), which must then map back into the structures of our theories. In other words, it takes a very specific (and improbable) stance to justify structural realism.

The reason I find that improbable is that I feel anything that we wish to treat as something we might not be capable of knowing, using science, is something that we must accept might not exist at all, from the point of view of science. So I find it downright incoherent to talk about "properties" that are "inaccessible to us" but which all the same determine outcomes. That sounds like an internally inconsistent statement, the meanings of the words are simply incompatible, but the incompatibility is not clear until you recognize that the whole concept of "determining outcomes" is a scientific concept. That means it is a concept that is accessible to us, it is our concept, so we make a category error putting that phrase in a sentence about what reality is doing that is not accessible to us. This I feel is what Stoljar is guilty of in that quote (and PBR as well).

So, I'm guessing Bohm is leaping the gun but would probably be sympathetic to this argument:

Yes, I agree with Seager, and indeed I've made a similar argument myself when people ask about the role of consciousness in quantum mechanics. It's not that there is some term in the equation that we attribute to consciousness, it is that, as Seager said, "our knowledge of the physical is entirely based upon its dispositions to produce certain conscious experiences under certain conditions." It is really in quantum mechanics where the importance of that seemingly obvious yet generally ignored fact becomes unignorable, though I argue it also comes up in statistical mechanics and chaos theory.

 

[bohm2]

The Stoljar quote gets to an even deeper potential problem. A structural realist might hold that the structure is not the elements or their properties, but some sort of relational pattern that can be expressed with many different types of elements and properties. But Stoljar appears to make the implicit and potentially unjustified assumption that any structural realist must hold that reality is determined by its properties, even if we don't or can't know what those properties are. I would call that reductionist realism, not structural realism, because it reverses the direction of the logic. Structural realism takes the properties of successful models and projects them back onto reality, concluding that something in the model resonates with the reality in some vague but important way. Reductionist realism starts with the reality, and imagines constraints on it (properties), which must then map back into the structures of our theories. In other words, it takes a very specific (and improbable) stance to justify structural realism.

I don't think that is the central concern in Stoljar's argument. He is primarily concerned with Russell's and Eddington's "ignorance hypothesis"; the unknowable "intrinsic" properties of matter and the consequences it has on the mind-body problem. It is really the debate between the panpsychists (Seager, Strawson, Bohm) versus the emergentists (Stoljar, Chomsky) in trying to understand how the brain/matter/nonexperiential/structural (as currently conceived) can spit out experiential/mental/qualia. Here is one paper discussing this:

Suppose that Russell and Blackburn are correct, and scientific methodology will never reveal the ultimate ontological basis for observed phenomena, despite the optimism engendered by science’s continuing progress. In that case, we are not justified in generalizing from cases in which scientific methods have shown that non-manifest phenomena explain manifest nonexperiential phenomena, to the conclusion that no experiential truth is primitive. If categorical properties are beyond the reach of scientific investigation, then at most we can conclude that manifest dispositions (of experienceless objects) will be initially explained by other, non-manifest dispositions. But we have no reason to speculate about the nature of the categorical properties that ultimately explain the dispositions we observe...This may seem a hollow victory for the primitivist, since allowing that categorical properties are experiential appears to lead to panpsychism, a view rejected by most primitivists. But as Stoljar himself notes, panpsychism can be avoided...

"The Role of Ignorance in the Problem of Consciousness”. Critical notice of Daniel Stoljar
http://pages.shanti.virginia.edu/bg8y/

Strawson’s Realistic monism (Stoljar's criticism of Strawson's paper)
http://philrsss.anu.edu.au/sites/default/files/people/Strawson.pdf

Realistic Monism (Strawson)
http://faculty.unlv.edu/beiseckd/Courses/PHIL-352/Dave%20-%20Consciousness%20PDFs/Strawson%20-%20Realistic%20Monism%20and%20Replies/Strawson%20-%20Realistic%20Monism%20Why%20Physicalism%20Entails%20Panpsychism.pdf

 

[Ken G]

Yes, I'm sure you are right that this is the correct context for Stoljar's points, I'm just surprised at how often I see the implicit assumption that behaviors are controlled by properties, and at issue is whether or not science has access to those properties. That just seems like a very confused assumption to me-- science is all about properties, it uses the concept of a property to generate models that explain outcomes. Nothing about reality has anything to do with properties, other than the lens through which science sees reality. Properties are clearly a part of science, to assume they are part of reality requires quite a leap of faith at best, and a category error at worst.

Note even the quote above seems to fall into this trap when it says "But we have no reason to speculate about the nature of the categorical properties that ultimately explain the dispositions we observe..." I would say we have plenty of reasons to speculate about the nature of properties, and we have plenty of reasons to speculate about how they explain dispositions. What we have no justification to speculate, and no payoff either, is that they are "categorical" in nature (whatever that even means), or that they "ultimately" explain anything at all-- on the simple grounds that a "categorical" or "ultimate" explanation is an incoherent concept that never had anything to do with either science or knowledge in the first place.

 

[bohm2]

This seems like a very interesting (and long) dissertation by Allori (via Tim Maudlin's direction) discussing ontology and physical theories. I'd like to print it out but I'd get beat up. I just briefly looked at it and she discusses the different interpretations of QM and does a really good job hi-liting some of the different versions of Bohmian models (configurational versus particle versions), GRW theories, etc. with respect to the possible "physical" interpretations of configuration space, wave function, particles, fields, etc. Interestingly, when discussing the ontology of the wave function and the possibility that it is a property of "particles", she seems to dismiss it:

The Role of the Wave Function

Let us now clarify one issue: If the primitive ontology of the theory are the building block of the physical world, they are the stuff in three-dimensional space physical objects are made of, what is the wave function if not a material object? One way of interpreting the wave function if it is not part of the primitive ontology is to say that the wave function is a property of the particles. Monton seems to have this view in some of his writings: "the wave function doesn’t exist on its own, but it corresponds to a property possessed by the system of all the particles in the universe".(Monton 2006)

If it is the case, then the wave function is not physical but it is instead an abstract entity. It is not really clear to me what “the wave function is a property” is supposed to mean, given that it is not clear to me what a property is supposed to be. Be that as it may, what kind of property is the wave function supposed to be? Categorical or dispositional? In my understanding, a dispositional property is a property that is what it is in virtue of the laws of physics. For example, the mass of an object can be considered a dispositional property in the sense that it expresses the resistance of the body to be accelerated by external forces. In contrast, the mass can be thought as a categorical property of the body as it specifies its own nature.

In any case, it does not seem right to consider the wave function (not even the conditional one) as a categorical property of the particles: in fact, it does not in any ways determine its nature. It might seem a little less far fetched to think to the conditional wave function as a dispositional property but actually it is difficult since it might happen not: the conditional wave function might not evolve according to Schrödinger’s equation. It would do that only in particular situations like the one in which the wave function has a particular form, the so called effective wave function. In any case, independently of whether one can make sense of the wave function being a property of the particle or one has to assume that the wave function is an holistic property, a property of the universe as a whole, I do not really see any advantage in saying that the wave function is a property, unless what one means is, at the end of the day, that it is a law.

Fundamental Physical Theories: Mathematical Structures Grounded on a Primitive Ontology
http://www.niu.edu/~vallori/thesis4.pdf

 

[bohm2]

Here's another interesting ('Quantum Mechanics Without Wavefunctions') model that just got posted today:

Regarding interpretation, we draw no definitive conclusions here. However, it is clearly of great significance that the form of Q can be expressed in terms of x and its C derivatives—implying the key idea that the interaction of nearby trajectories, rather than particles, is the source of all empirically observed quantum phenomena (suggesting a kind of “many worlds” theory, albeit one very different from Ref. 5). As such, it is locality in configuration space,rather than in the usual position space per se, that is relevant. In effect, we have a hidden variable theory that is local in configuration space, but nonlocal in position space—though the latter is hardly “spooky” in the present nonrelativistic context [even classical theory is nonlocal in this sense, depending on V (x)]. Many ramifications are anticipated for a wavefunction-free interpretation of measurement, entanglement, etc. One wonders whether Bohm would have abandoned pilot waves, had he known such a formulation was possible—or, for that matter, whether the notion of quantum trajectories might have actually appealed to Einstein.

Quantum Mechanics Without Wavefunctions
http://lanl.arxiv.org/pdf/1201.2382.pdf

 

[ThomasT]

Another nice thread bohm2. Lots of links and interesting statements regarding your consideration.

I'm curious. Can you summarize how you're thinking about this now?

My own view is in agreement with Ken G's (with my bolding):

... just because the mathematical structure works in experiments, that cannot prove that the elements exist anywhere but in that theory. Indeed, this has been seen over and over throughout history. That doesn't mean we shouldn't use the terms from the theory to apply to reality, it just means there is no requirement to take them too literally. The demonstrable physics doesn't care how literally we take those terms, so why should we?

You've asked about the relative ontological feasibility of wave functions and fields and configuration space. Well, it's known that these are mathematical constructions used for the purpose of predicting instrumental behavior. Beyond that, it's pretty much a matter of taste. Force fields correspond roughly to the notion of media. Wave functions are solutions to a general (arguably nonrealistic) wave equation. And configuration space is clearly a calculational convention ... not to be taken as a literal description of nature.

The only reality that we can appeal to is our 3D sensory apprehension, which remains the ultimate arbiter of the truth of statements about reality.

 

[bohm2]

Another nice thread bohm2. Lots of links and interesting statements regarding your consideration. I'm curious. Can you summarize how you're thinking about this now? My own view is in agreement with Ken G's (with my bolding):
You've asked about the relative ontological feasibility of wave functions and fields and configuration space. Well, it's known that these are mathematical constructions used for the purpose of predicting instrumental behavior. Beyond that, it's pretty much a matter of taste. Force fields correspond roughly to the notion of media. Wave functions are solutions to a general (arguably nonrealistic) wave equation. And configuration space is clearly a calculational convention ... not to be taken as a literal description of nature.

The only reality that we can appeal to is our 3D sensory apprehension, which remains the ultimate arbiter of the truth of statements about reality.

From the little that I've read on the topic, I'm very biased/sympathetic toward 'structural realism'. From what I understand of your/Ken G's position, it is more in line with 'constructive empiricism', I think. So I see the wave function and configuration space as something more than just a calculational device.

 

[ThomasT]

... I see the wave function and configuration space as something more than just a calculational device.

And you might be right. The question is: how can that be ascertained? Any ideas?

But maybe that's not fair. Maybe all we can hope for are reasonable, consistent arguments in favor of the ontological reality, in some sense, of wave function and configuration space representations.

So, wrt that, what's your current opinion?

 

[bohm2]

Of all the models I've linked in this thread, I think, I find Valentini's model the most appealing (maybe because it's the easiest one for me to understand-dumb reason) but Bohm's/Hiley's is interesting also, despite the strange properties of their quantum potential. I

 

[ThomasT]

Of all the models I've linked in this thread, I think, I find Valentini's model the most appealing (maybe because it's the easiest one for me to understand) but Bohm's/Hiley's is interesting also, despite the strange properties of their quantum potential.

Then I'll check out Valentini's model more closely. Thanks. As for Bohm's quantum potential ... maybe it would be informative for Demystifier to talk about this, as it seems to me to be a mathematical construction required to make dBB predictions fit with standard QM predictions that doesn't inform wrt ... reality.

 

[Ken G]

Here's another interesting ('Quantum Mechanics Without Wavefunctions') model that just got posted today:

Yes, this nicely highlights my objection to treating any of the concepts we cook up to do physics as anything but effectively, rather than actually, ontological: they are often non-unique in regard to the testable predictions they make. If reality has any attribute, should that attribute not be uniqueness? Even a "landscape" believer would presumably not hold that every interpretation of a given theory spawns a separate reality! Or, if we hold that one view is the actual reality, even though we have no evidence to distinguish it, do we not follow the path we often criticize about world religions?