Why John Bell prefered Bohm's ontological pilot-wave interpretation of orthodox quantum mechanics over Bohr's epistemological "Copenhagen interpretation""... despite numerous solutions of the [measurement] problem 'for all practical purposes' [i.e., 'FAPP'] , a problem of principle remains. It is that of locating precisely the boundary between what must be described by wavy quantum states on the one hand, and in Bohr's 'classical terms' on the other. The elimination of this shifty boundary has for me always been the main attraction of the [Bohm] 'pilot-wave' picture. ... all students should be introduced to it, for it encourages flexibility and precision of thought. In particular, it illustrates very explicitly Bohr's insight that the result of a 'measurement' does not in general reveal some preexisting property of the 'system', but is a product of both 'system' and 'apparatus'. It seems to me that full appreciation of this would have aborted most of the 'impossibility proofs', and most of 'quantum logic'" p.viii

Evidently Bell did not think much of David Finkelstein's "quantum logic" approach, discussed in Gary Zukav's The Dancing Wu Li Masters, which does not seem, now in hindsight, to of yielded much new physics. What happens in a self-measurement where the 'system' is the 'apparatus'? This is creative novelty where something that did not exist before comes into actuality. Indeed, this may be how our experience of time itself emerges in our stream of consciousness.

Continuing with Bell's thoughts on Bohm's pilot-wave/hidden-variable (beable) theory:

"While the usual predictions are obtained for experimental tests of special relativity, it is lamented that a preferred frame of reference is involved behind the phenomena .... Many students never reaize, it seems to me, that this primitive attitude, admitting a special system of reference which is experimentally inaccessible, is consistent .. if unsophisticated."

While the special relativity of globally flat is hostile to preferred reference frames, the globally curved, but locally flat, spacetime of general relativity is not so hostile to them. The Michelson-Morely experiment showed that the motion of the earth though the ether was undetectable. That is, the speed of light in vacuum is an absolute speed limit being the same number for all ordinary observers moving uniformly relative to each other. The equations of both special and general relativity obey this local speed limit. Special relativity can be pictured as a field of parallel invariant light cones. General relativity introduces nonparallel relative tilting of neighboring light cones giving things like the one-way horizons of black holes. However, the basic Big Bang expanding universe cosmological solution of the globally generally covariant and locally Lorentz-invariant field equations of general relativity does have a globally preferred frame of reference called the Hubble flow. This has operational meaning. The globally preferred rest frame of the universe is detected by the isotropy, to one part in one hundred thousand, of the cosmic blackbody radiation whose current temperature is a few degrees above absolute zero. Bohm has suggested that this is the frame in which the quantum potential acts instantaneously. This is adhoc, and the final understanding needs a proper theory of quantum gravity.

"Any study of the pilot-wave theory, when more than one particle is considered, leads quickly to the question of action at a distance, or 'nonlocality', and the Einstein-Podolsky-Rosen corrrelations..." p. ix

Bell rejects the many-worlds theory as well as the quantum logic theory as explanations of the meaning of quantum physics.

"My attitude to the Everett-de Witt 'many worlds' interpretation, a rather negative one ..." p. ix

Contrary to Victor Stenger's position in The Unconscious Quantum and to Murray Gell-Mann's position in The Quark and the Jaguar, who both, for different reasons, think that nonlocality is "the story distorted", Bell writing on the Einstein-Podolsky-Rosen (EPR) paradox says:

"It is the requirement of locality, or more precisely that the result of a measurement on one system be unaffected by operations on the distant system with which it has interacted in the past, that creates the essential difficulty." p. 14

According to Bell's definition of "locality" it doesn't matter if its violation is by a direct spacelike quantum action at a distance outside the local light cones of the detection events, or whether there is a timelike or lightlike "advanced" backward propagation of information from the future detection events to the past source pair emission event. Stenger prefers the later picture, however, what he does not understand is that both the "faster-than-light" spacelike and the backward-in-time pictures are operationally equivalent. Stenger, in his book, The Unconscious Quantum, also splits some verbal hairs between "locality", "separablility" and "completeness" which do not add any new understanding to Bell's more elegant presentation of the real physics problem.

Bell summarizes the logic of the "incompleteness" argument of the original EPR paper of 1935 in the simpler Bohm "singlet spin" version in the following way. Assuming locality: "Since we can predict in advance the result of measuring any chosen component of sigma2 [i.e., the spin of particle 2], by previously measuring the same component of sigma 1 [i.e., the spin of particle 1 of the same individual pair], it follows [from locality] that the result of any such measurement must actually be predetermined. Since the initial quantum mechanical wave function does not determine the result of an individual measurement, this predetermination implies the possibility of a more complete specification of the state." p. 15

The EPR argument shows that locality leads to a violation of the Heisenberg uncertainty principle for the twin particle in the pair that is not directly measured if we assume "counter factual definiteness" (CFD). That is, a measurement that could have been made but wasn't, would have had a definite result if it had been made. To see a popular discussion of how nonlocality for entangled quantum states is required to preserve the uncertainty principle see Heinz Pagels's The Cosmic Code. For a popular discussion on "counter factuals" and new experiments that confirm CFD see Roger Penrose's The Small, the Large, and the Human Mind. Note, that Bell shows that any local, i.e., "predetermined", hidden variable theory will violate the Heisenberg uncertainty principle which is a constraint on statistical fluctuations of incompatible observables in an ensemble of identical measurements. Therefore, any local hidden variable theory will violate the statistical predictions of orthodox quantum mechanics. Note that the post-quantum mechanics of consciousness that I profess does violate the statistical predictions of orthodox quantum mechanics but for entirely different reasons. That is locality is a sufficient condition to violate the statistical predictions of orthodox quantum mechanics, but it is not a necessary condition. Post-quantum mechanics is a nonlocal hidden variable theory with "nonlocal communication" as defined by Stenger.

Bell on "hidden variables": "In a theory in which parameters are added to quantum mechanics to determine the results of individual measurements, without changing the statistical predictions, there must be a mechanism whereby the setting of one measuring device can influence the reading another instrument, however remote. Moreover, the signal involved must propagate instantaneously, so that such a theory could not be Lorentz invariant." p. 20

To balance out Victor Stenger's premature skeptical certitude in his book, The Unconscious Quantum, I include relevant remarks by John Bell, with Michael Nauenberg who I knew at Cornell and UCSC, on the role of consciousness, the universe and the impossibility of self-measurement in orthodox quantum mechanics:

"this assumes that the intermediate evolution ... is governed entirely by the Schrodinger equation, and therefore that the pointer position is not looked at until after the final interaction. If the pointer position is observed just after each interaction then the moral process comes into play... from the theorist's point of view ... the experiment may be said to start with the printed proposal and to end with the issue of the report. For him the laboratory, the experimenter, the administration, and the editorial staff of the Physical Review, are all just part of the instrumentation. The incorporation of (presumably) conscious experimenters and editors into the equipment raises a very intriguing question. For they know the results before the theorist reads the report, and the question is whether their knowledge is incompatible with the sort of interference phenomena discussed ... If the interference is destroyed, then the Schrodinger equation is incorrect for systems containing consciousness. If the interference is not destroyed the quantum mechanical description is revealed as not wrong but certainly incomplete. We have something analogous to a two-slit interference experiment where the 'particle' in any particular instance has gone through only one of the slits (and knows it!) and yet there are interference terms depending on the wave having gone through both slits. Thus we have both waves and particle trajectories as in the de Broglie-Bohm 'pilot wave' or 'hidden parameter' interpretations of quantum mechanics .... It is easy to imagine a state vector for the whole universe, quietly pursuing its linear evolution though all of time and containing somehow all possible worlds. But the usual interpretive axioms of quantum mechanics come into play only when the system interacts with something else, is 'observed'. For the universe there is nothing else, and quantum mechanics in its traditional form has nothing to say. It gives no way of, indeed no meaning in picking out from the wave of possibility the single unique thread of history.

These considerations, in our opinion, lead inescapably to the conclusion that quantum mechanics is, at best, incomplete. We look forward to a new theory which can refer meaningfully to events in a given system without requiring 'observation' by another system. The critical test cases requiring this conclusion are systems containing consciousness and the universe as a whole. Actually, the writers share with most physicists a degree of embarrassment at consciousness being dragged into physics ... It remains a logical possibility that it is an act of consciousness which is ultimately responsible for the reduction of the wavepacket ... What is more likely is that the new way of seeing things will involve an imaginative leap that will astonish us..." pp. 25-27

Henry Stapp has a post-quantum ontological collapse of the mental quantum wave function of the brain which is not caused by consciousness the way Wigner meant it, but, rather, which explains the inner experience of consciousness. What is important about Stapp's picture is that it is a self-measurement. Similarly for Penrose's "orchestrated self objective collapse". I have a "neural network" way of looking at this, using a post-Bohmian picture, where the self-organizational aspect is more obvious than in Stapp's or Penrose's picture. The big change from Bohm's picture is that there are no empty branches of the wavefunction in the self-measurement. This is a point emphasized to me by Stapp and it is crucial. The self-organizing loop consisting of "backactivity" with the Bohm force, self-consistently determines the momentary observable and its actual eigenfunction that forms a basin of attraction in configuration space at each moment of consciousness for the self-measuring "isolated" (e.g. Penrose) conscious mind-brain system pumped by sensory input. This measurement is happening inside the system consistent with the introspective nature of our, so far, private inner experiences. It is no accident that Bell in the above quote lumps quantum cosmology and conscious systems together, for an analogous self-measurement is happening in quantum cosmology. See Lee Smolin's The Life of the Cosmos on the latter problem.

Bell characterizes the Copenhagen interpretation of quantum reality, with only an epistemological wavefunction for statistical ensembles of identical simple systems, as "subjective". The classical description is "objective". p. 29 He finds the fuzziness of the "Von Neumann cut" boundary between quantum and classical realities to be "surely of a provisional nature". Bell has several reasons for the existence of "hidden variables".

"A possibility is that we find exactly where the boundary lies. More plausible to me is that we will find that there is no boundary. It is hard for me to envisage discourse about a world with no classical part - no base of given events, be they only mental events in a single consciousness to be correlated. On the other hand, it is easy to imagine that the classical domain could be extended to cover the whole. The wavefunctions would prove to be a provisional or incomplete description of the quantum mechanical part, of which an objective account would become possible. It is this possibility, of a homogeneous account of the world, which is for me the chief motivation of the study of the so-called 'hidden variable' possibility. ... A second motivation .. it can be conjectured that the seemingly random statistical fluctuations are determined by the extra 'hidden variables' ... we ... because at this stage ... we certainly cannot control them ... the possibility of determinism is less compelling than the possibility of having one world instead of two ... A third motivation is .... the famous argument of Einstein, Podolsky and Rosen .... Thus we can know in advance the result of measuring any component of sigma2 [spin] by previously, and possibly at a very distant place, measuring the corresponding component of sigma1. This strongly suggests that the outcomes of such measurments, along arbitrary directions, are actually determined in advance, by variables over which we have no control ... There need then be no temptation to regard the performance of one measurement as a causal influence on the result of the second, distant, measurement. The description of the situation could be manifestly 'local' ... We will find, in fact, that no local deterministic hidden-variable can reproduce all the experimental predictions of quantum mechanics." pp. 30-31

Bell wrote the above in 1971. Since that time Eberhard et-al have removed the restriction to "determinism" a fact that Stenger seems not to have noted in his recent book, The Unconscious Quantum -- unless I am mistaken?

Bell considers nonrelativistic particles with "spin". The particle's position is a hidden variable.

"We have here a picture in which although the wave has two components, the particle only has position ... The particle does not 'spin', although the experimental phenomena associated with spin are reproduced. Thus the picture resulting from a hidden-variable account ... need not much resemble the traditional classical picture ... The electron need not turn out to be a small spinning yellow sphere.

A second way in which the scheme is instructive is in the explicit picture of the very essential role of the apparatus. The result of a 'spin measurement', for example, depends in a very complicated way on the initial position .. of the particle and on the strength and geometry of the magnetic field. Thus the result of the measurement does not actually tell us about some property previously possessed by the system, but about something that has come into being in the combination of system and apparatus. ... the present 'quantum theory of measurement' in which the quantum and classical levels interact only fitfully ... should be replaced by an interaction of a continuous, if variable, character..." pp. 35-36

Looking at the many-particle problem in Bohm's pilot-wave model of quantum reality "one sees that the behavior of a given [hidden] variable ... is determined not only by the conditions in the immediate neighborhood (in ordinary three-space) but also by what is happening at all the other positions ... That is to say, that although the system of equations is 'local' in an obvious sense in the 3n-dimensional space, it is not at all local in ordinary three-space. As applied to the Einstein-Podolsky-Rosen situation, we find that this scheme provides an explicity causal mechanism by which the operations on one of the two measuring devices can influence the response of the distant device. This is quite the reverse of the resolution hoped for by EPR, who envisaged that the first device could serve only to reveal the character of information already stored in space, and propagating in an undisturbed way towards the other equipment." p. 36

This objective nonlocality is crucial to the understanding of how the quantum thought field organizes and synchronizes separated parts of the brain, and indeed, the whole living body IMHO. The Eccles gates linking mind to matter in the brain appear to be the web of isolated control electrons that couple to the conformations of the individual protein dimers in the microtubule infrastructure. In ordinary quantum mechanics there is no possibility of nonlocal communication between these spatially separated electrons even though their collective behavior is nicely globally coordinated above and beyond classical signalling mechanisms. This is because there is no nonrandom self-organizing stability mechanism in ordinary quantum mechanics. There is such a stability mechanism in post-quantum mechanics which is predicted to come into play when the Eccles gate control electrons are sufficiently isolated from external random decoherence as discussed, for example, by Roger Penrose in The Large, the Small and the Human Mind.

Bell points to a surprising relationship between Everett's many-worlds idea and the de Broglie-Bohm pilot-wave: "the elimination of arbitrary and inessential elements from Everett's theory leads back to, and throws new light on, the concepts of de Broglie." p. 93

"... there are infinitely many different expansions ... corresponding to the infinitely many complete sets ... Is there then an additional multiplicity of universes... ? I think (I am not sure) the answer is no, and that Everett confines his interpretation to a particular expansion ... Everett's structure is based on an expansion in which instrument readings R ... are diagonalized. This preference ... is not dictated by the mathematical structure ... It is just added ... to make the model reflect human experience. The existence of such a preferred set of variables is one of the elements in the close correspondence between Everett's theory and de Broglie's -- where the positions of particles have a particular role." p. 96

"(1) Whereas Everett's special variables are the vaguely anthropocentric instrument readings, de Broglie's are related to an assumed microscopic structure of the world ....

(2) Whereas Everett assumes that all configurations of his special variables are realized at any time, each in the appropriate branch universe, the de Broglie world has a particular configuration. I do not myself see that anything useful is achieved by the assumed existence of the other branches of which I am not aware. ...

(3) Whereas Everett makes no attempt, or only a half-hearted one, to link successive configurations of the world into continuous trajectories, de Broglie does just this in a perfectly deterministic way..." p. 98

De Broglie's "determinism" does not survive the extension from quantum to post-quantum mechanics because the "backactivity" from the sufficiently isolated classical "beable" to its attached pilot-wave introduces the qualitatively new feature of adaptive self-determination, or self-organization, which is non-computable in Penrose's sense. Even though the beable is isolated from random environmental decoherence enabling it to quantum compute, there are non-random secular changes from the I/0 sensory devices feeding information into the self-organizing sentient post-quantum feedback-control loop.

"Now these trajectories of de Broglie, innocent .... in configuration space, are really very peculiar as regards locality in ordinary three-space."