Working paper 5-02

Quantum physics and human consciousness:
The status of the current debate.
The Open Polytechnic Working Papers are a series of peer-reviewed academic and professionalpapers published in order to stimulate discussion and comment. Many Papers are works inprogress and feedback is therefore welcomed.
This work may be cited as: Jackson, P. Quantum physics and human consciousness: The status of thecurrent debate, The Open Polytechnic of New Zealand, Working Paper, November 2002.
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ii The Open Polytechnic of New Zealand This paper reviews the literature on the debate about the relationship betweenthe quantum realm and human consciousness. It starts with a brief look atquantum physics, then moves on to look at the key quantum interpretations,covering the Copenhagen Interpretation, Von Neumann’s views, the neo-realists, and the ‘many worlds’ and ‘many minds’ views. Key authors in theliterature on the quantum-consciousness debate are then reviewed within aframework of three levels of explanation: neurological, psychological andphilosophical. The various analyses are brought together by consideration ofthe key issues that arose during the review, where these were seen as thequantum-neuron interaction, neurons and consciousness, consciousness and thewave equation, Copenhagen versus the rest, ‘many worlds’ versus ‘manyminds’, the Cartesian dichotomy, and Chalmers’ hard problem. Finally, thepaper finds the ‘many minds’ view the most viable of the views examined.
Introduction
Key quantum interpretations
The current debate
Bringing it all together
‘Many worlds’ versus ‘many minds’ Some tentative conclusions
References
Bibliography
Quantum Physics and Human Consciousness:
The Status of the Current Debate
This paper is intended for those interested in the relationship between quantumphysics and human consciousness. Readers from a variety of disciplines, suchas philosophy, physics, and psychology, should find it readily accessible. Itshould also be accessible to a wider readership outside these disciplines.
Arguably, two of the greatest mysteries facing science are that of the ultimatenature of reality as depicted within quantum physics, and that of humanconsciousness. In the former, we cannot directly access it, but can infer itsnature by means of the results of experimental physics. In the latter, althoughwe all know what it is like to be conscious, its actual nature may be beyond thereach of science.
The aim here is to review the key literature on this relationship in an attempt tosee where the debate has led to, to date. Although this debate has been going onfor many decades now (for example, Von Neumann, 1955), it has intensified inrecent years.
At the root of research into the relationship examined here is the classical-quantum dichotomy, along with the Cartesian mind-body dichotomy. In thecase of the former dichotomy, we are powerfully conditioned by our birth into,and subsequent maturation and socialisation in, the realm of sense data. Ouracquisition of speech and concept formation arises directly from our beingembedded in the classical world. Whilst we can generate mathematicalformalisms to model and make inferences about the non-classical micro-realmof quanta, we can never directly access that realm. Our mental representationsof the micro-realm are always classical. In the case of the latter dichotomy, theCartesian epistemology was never an issue for classical physics because mind(consciousness) did not enter into the equations of motion nor into any othermathematical formalism. However, with the introduction of quantum mechanics, conscious experience does come into play, regardless of whichinterpretation of the quantum facts one subscribes to. This has raised questionsabout Descartes’ dichotomy and led some to wanting to revise his epistemologyin the light of the findings of quantum theory. But more of this later. Manybooks have been written about quantum physics, including its historicaldevelopment. There isn’t the space in this paper to address these historical anddevelopmental issues. However, it is necessary to give them in brief.
Quantum physics in brief
Quantum physics (known also as quantum mechanics, as opposed to classicalmechanics — see below) had its foundations at the beginning of the 20thcentury, but appeared more formally as a branch of physics at the 5th SolvayConference in 1927 (Stapp, 1998). Most physicists of the 18th century believedthat light consisted of particles, which they called corpuscles. From about 1800,evidence began to accumulate for a wave theory of light. By the end of the 19thcentury, physicists almost universally accepted this wave theory of light. In1900, Max Planck, responding to the problems posed by the conflict betweentheory and actuality in the spectrum of radiation from a hot body, introducedthe idea of the quantum. He suggested that the radiation energy is emitted, notcontinuously, but rather in discrete packets called quanta. The notion of quantawas realised through experiment when Planck derived a very small value (h),which became known as Planck’s constant — a very important value in thesubsequent development of quantum theory.
Thus arose the concept of quantum mechanics (as opposed to classicalmechanics). In 1905 Albert Einstein extended Planck’s hypothesis to explain thephotoelectric effect. But the development of quantum theory soon becameclosely tied to the difficulty of explaining by classical mechanics the stability ofEarnest Rutherford’s nuclear atom. Niels Bohr in 1913 led the way toexplanation with his model of the hydrogen atom, in which the motion of theelectron around the proton was analysed as if it were a planet orbiting around asun, where only discrete orbits were allowed. However, Bohr’s model relied onan inconsistent mixture of old and new physical principles. De Broglie, who in1924 proposed that not only did light have a wave-particle nature, but so alsodid matter, made a significant contribution to the development of quantumphysics.
In 1925, the arbitrary postulates of quantum theory found consistent expressionin the quantum mechanics formulated by Heisenberg, Schrödinger, and Dirac.
Werner Heisenberg, quite independently of the other two, developed his matrix mechanics as a way of understanding what was happening at the atomic level.
However, the mathematical basis of matrix mechanics proved somewhatcumbersome. In 1926, Erwin Schrödinger postulated a wave equation that hebelieved described the location of, say, an electron. Thus arose wave mechanicsas applied to quanta (wave mechanics had existed long before quantum physicscame into being). In this way, Schrodinger developed a mathematicalalgorithm, based on classical principles that could be applied to the non-classical realm of quanta. However, he encountered problems when attemptingto apply his wave equation to the simplest of atomic structures — the hydrogenatom, which has only the one electron orbiting its simple nucleus. Max Born,who realised that the wave equation was actually statistical and not a real wave,came up with the notion that the square of the amplitude of the waverepresents the probability of finding an electron’s position or momentum. Thusarose statistical mechanics. Born’s insight led to the use of the wave equation,with a wide variety of wave functions (waves that attempt to describesubatomic entities, such as electrons and photons, at the quantum level), topredict outcomes in quantum experiments. The success of this use and the levelof accuracy entailed is without parallel: quantum mechanics has become themost successful of all the branches of science.
These developments led to Bohr’s concept of the electron as a locatable particleorbiting the nucleus being replaced in quantum statistical mechanics by aprobability cloud that describes the likely location of an electron. As impliedabove, for a given quantum entity (for example, electron) and a givenexperimental arrangement, there is a specific wave function. This wave functionevolves in time, describing a probabilistic cloud. Only when a quantum entityentangles with a measurement set-up does the wave function ‘collapse‘ orreduce to a measurable event in classical space-time. However, as we shall seeshortly, not all theorists agree with the notion of the collapse of the wavefunction. The two key features of the quantum theory are: Bohr’s ‘complementarity principle’. This principle deals with the concept ofwave-particle duality, which states that quantum entities can displayeither wave-like or particle-like properties, depending on themeasurement set-up. However, these entities are neither waves norparticles. We simply do not know what they are. In fact, theCopenhagen interpretation (see shortly) insists on a fundamentalquantum ignorance, in which we cannot know what these entities are.
Heisenberg’s ‘uncertainty principle’, or more correctly, ‘indeterminacyprinciple’. This principle states that if we wish to measure an entity’smomentum (velocity) with precision, then we must sacrifice precision inthe measurement of its position, and vice versa. This principle applies to a variety of such conjugate pairs, where momentum-position is a verycommon pair (there are others, such as spin and charge). What thisprinciple says, in effect, is that as the precision of our measurement ofone of the pair (say, momentum) approaches perfection, our knowledgeof the other of the pair (say, position) approaches zero. Themathematical relationship is a very simple one, and can be picturedsomewhat as a seesaw, as follows: Figure 1: A seesaw analogy
Figure 1 shows a seesaw analogy of the uncertainty principle, where ∆p is theerror in measuring momentum (∆), and x is the error in measuring position (x).
The smaller the value of ∆p or x, the greater the precision. Thus, you can seefrom the diagram that as ∆x is moved down toward greater precision, ∆p mustmove up toward reduced precision. In the extreme, as one of the pair movestoward zero (absolute precision), the other moves toward infinity (noknowledge at all).
These two key principles have profound implications, not only for quantumphysics, but also for our perceptions of the nature of reality. One implication isthat the seemingly solid reliable reality that we perceive is based on somethingthat is ultimately uncertain or non-determinable. Many have found this to be ashocking ‘fact’. Einstein, for one, not only found it shocking but also attemptedto refute it, saying to Bohr one of in his many debates with him that he(Einstein) could not believe that God played dice with the universe.
Unfortunately for Einstein, he lost every one of those debates. Bohr once saidthat if you did not find quantum theory shocking, then you had not understoodit. There are other implications surrounding the complementarity principle. Notonly is everything fundamentally indeterminate; we cannot really know whatthings truly are in themselves. We classical beings are comfortable with notionssuch as particles (electrons as tiny billiard balls) and waves (ripples on a pond).
However, electrons are neither particle nor wave. We simply do not know whatthey are. The term electron (or photon) is a comfortable label, nothing more.
The strangeness of the quantum realm
A range of experiments has brought out the strangeness of the quantum realm. Iwill describe two simple such experiments to give you a feel for just howstrange the quantum realm really is. In a very early experiment, theexperimental set-up consisted of an electron gun (similar to that in yourtelevision), which emitted electrons in a narrow beam. This beam was directedat a metal plate having a very small circular aperture. As the beam was verynarrow, most electrons passed through the aperture and on to a photographicfilm on the other side of the plate. Electrons striking the film chemicallychanged the film at that location, where this showed up as a dark spot on thedeveloped film. Where a large number of electrons was passed, per second,through the aperture, a pattern would appear on the film, looking somewhatlike a series of concentric rings (known as Airy rings, after an 18th CenturyAstronomer Royal who discovered this effect using light). This told theexperimenter that interference was occurring at the aperture, meaning that theelectrons were behaving like waves, not particles. Yet, individual electrons werestriking the film, in order to produce the overall pattern. So what washappening? The experimenter then slowed down the rate of electron emissionuntil only one electron was passing through the aperture each minute. Sureenough, he found that individual electron strikes were recorded, showing that,at the film, he was dealing with particles. However, he then left the apparatus,at this emission rate, for a week (it seems he went sailing on the Thames). Whenhe developed the film, to his amazement, instead of finding a pattern of randomstrikes all over the film, he found the interference pattern. Thus, even thoughthe electrons were passing through the hole and striking the plate asindividuals, and could not conceivably interfere with each other under thoseconditions, they still appeared to form the interference pattern. It was as thoughthe individual electrons ‘knew’ where to land, ahead of arriving at the film.
Thus, not only are we dealing with the wave-particle paradox, but worse, withelectrons that appeared to be conscious! Other experiments have been conducted, using very narrow vertical slitsinstead of small holes. In one simple version, two slits are formed in a platewhere the horizontal separation between them is very small. Again, as in theabove experiment, an electron beam is ‘shone’ at the slits, and another variety ofinterference pattern appears at the film on the other side of the slits. Thus,again, we have wave-like behaviour at the slits and particle-like behaviour atthe film. If the emission rate is reduced to, say, one per minute, again, over alengthy period of time, the interference pattern (vertical light and dark bars inthis case) appears. If one slit is closed, so no electrons can pass through, theinterference pattern disappears and a single vertical dark bar appears, indicating particle-like behaviour. If, with both slits open, we attempt toidentify which slits individual electrons are going though, we cause the set-upto behave as though the ‘looked at slit’ is closed. What do we make of all ofthis? We, again, have ‘knowing’ electrons, which not only know in advancewhere to land on the film; they also appear to ‘know’ what the set-up is inadvance of reaching the slits.
The preceding gives you a flavour of what we are up against in trying tounderstand what is happening at the quantum level. Heisenberg left us in nodoubt that, at that level, there is no certainty, only potentia (Heisenbug’s term),which may or may not become a reality in a given experimental set-up. Inaddition, we have quantum entities that can behave as both particle-like andwave-like in the same experiment. Finally, we appear to have ‘knowing’ quantathat behave in ways that no classical object ever does. It is as though the act ofobserving quanta has an influence on what they become in the classical world,that is, the act of observation appears to ‘collapse’ the probabilities of the givenwave function to an actual measurement. It is this notion that led some tobelieve that it was ultimately the consciousness of the observer that caused thiscollapse.
The measurement problem
The experimentation of recent decades has sharpened what is known as the‘measurement problem’. In essence, the problem centres on the fact that, formany experiments, we can obtain only one unique answer (for example, ameasure of spinup or spindown of an electron1). However, quantummathematics shows that more than one answer can exist simultaneously as asuperposition of probabilities (for example, 50 per cent spinup plus 50 per centspindown). It is here that we have the stark contrast between the familiarclassical world of the senses and the weirdness of the quantum realm. TheAristotelian yes-no logic of our space-time classical world is not obeyed in thequantum realm.
In the classical world, a detector of, say, spinup states can yield only a yes-noresult. It is not possible for it to be in both states at the same time. And yet,under certain conditions, that is just what the mathematics show as beingpossible in the quantum realm. Under certain experimental conditions, electronpairs are produced, in which one of the pair has spinup and the otherspindown. In the case where the electron direction is at right angles to spin, themathematics shows that either spinup or spindown will be detected (but notboth together). Thus, there is no measurement problem, because only one Elecrons have a spin that can assume one of only two states known as ‘up’ for one direction of spin and ‘down’for the other direction. unique result is predicted. However, if the movement is at any other angle, thecomplex operators produce a prediction that both states can exist at the sametime, to some degree of probability. Yet, because the detector can display onlyone unique state, we have a measurement problem. There are various solutionsoffered to reconcile this seeming paradox, and we’ll look at these when we lookat the various interpretations of quantum theory. We will now look briefly athow human consciousness comes into the picture.
Where consciousness comes in
Quite unlike classical physics (in which there is no place for human experience),consciousness enters quantum theory and fact at the outset. This is because it isconsciousness that reconciles the weirdness of the quantum realm with theeveryday nature of classical reality; for example, in the experiment mentionedimmediately above, it is the experience of the observer of the detector’s statesthat matters. An observer sees (experiences) either a reading of spinup or ofspindown. It is not possible for the observer to experience both simultaneously.
Yet, under certain circumstances, the mathematics predict that both spinup andspindown can simultaneously exist in some ratio of probabilities. In thetransition from the probabilistic quantum realm to the classical realm, afundamental change occurs, and that appears to be brought about by theexperience of the observer. This change takes the technical name of decoherence,in which the probabilities described by the wave function collapse to a certainty(100 per cent probability). In their unmeasured superposed state, there are onlyprobabilities, no actualities. But, as soon as we make a measurement, we createa certainty. Not all quantum theorists and philosophers agree that it isconsciousness that brings about the collapse of the wave function. The originalCopenhagen School of Bohr did not see it that way.
We shall see later that consciousness is basic to the solution of the measurementproblem in several key interpretations of quantum theory. In some of theseinterpretations, consciousness takes an overt and clear role. In others, it isavoided by introducing the notion of hidden variables, as though electrons, forexample, have an as-yet unknown inner mechanism.
The Copenhagen interpretation
This is the earliest of the attempts to interpret the findings of quantumexperiments, and was formulated at the 5th Solvay Conference of 1927. In itsessential form, the Copenhagen interpretation cleaves reality into the quantumrealm of the entity being measured-observed, and the classical realm of theexperimental set-up and the observer-recorder of the results. We have no directaccess to the world of quanta. All we can do is make predictions aboutoutcomes in the classical realm, using mathematical algorithms that owe theirallegiance to classical thinking (namely Schrödinger’s wave equation). Bohr(1934) argued that, as far as we classical beings are concerned, there are noquantum entities unless we observe and measure them in the classical world ofthe senses. We have a fundamental ignorance of the quantum realm. At best, allwe can usefully envisage in the quantum realm are clouds of probabilities orpotentia. In the Copenhagen interpretation, the wave function collapses becausethe quantum realm entangles with the classical world of the experimental set upat the point of measurement.
Von Neumann
Johan (John) von Neumann, a Hungarian mathematician, made a profoundcontribution to our mathematical understanding of quantum mechanics (vonNeumann, 1955)2. He was uncomfortable with the Copenhagen view that onecould separate the quantum and classical realms so completely. He argued thatthe experimental set up and the observer are part of the quantum realm in thatthey are made of quanta. This being the case, he could not see where the wavefunction of the quantum entity under measurement collapses: Where did itentangle with the classical realm if everything was made of quanta? VonNeumann argued that the only possible privileged position in the whole chainfrom measured quanta to observer was the consciousness of the observer. Hefelt that he could argue thus, because consciousness (in line with Descartes’mind-body dichotomy) was immaterial, hence privileged.
The original text was in German, with the title Die Mathematische Grundlagen der Quantemechanik, and waspublished in 1932. The Neo-realists
There were those who rejected the Copenhagen interpretation in its entirety,finding repugnant the idea that there was no deep reality. Einstein was one ofthe first to take this stand, which later became known as the neo-realist position(a new way of viewing the fundamental nature of reality). The realm of quantawas seen as the location for the ultimate substrate of what most regarded asreality. While Einstein and others appeared to accept that, at present, we haveno access to that realm, it was, nonetheless, very real. It could be argued thatvon Neumann was a neo-realist, in that he postulated a new basis for reality.
However, he was not a neo-realist in the philosophical sense of the term realism.
In fact, he tended toward Cartesian dualism.
More recently, the physicist David Bohm became the key expounder of theseideas. To argue that the quantum realm comprised real entities, as opposed tomathematical abstractions, Bohm assumed that the Schrödinger wave equationwas itself real; he called it a quantum wave. That is, the wave function became areal wave capable of transferring energy and information. On this wave, realparticles (such as electrons) surfed. Bohm’s basic premise is that the quantumrealm is real and contains hidden variables. In this, he argued againstfundamental quantum ignorance, saying instead that there are, as yet,undiscovered laws that determine behaviour at the quantum level. A problemwith Bohm’s approach is that there is an implied violation of Einstein’srelativistic principle that the speed of light is an upper velocity limit for thetransfer of energy and information. In fact, Bohm’s notions make it clear thatinformation is conducted outside the ‘Light Cone’ arising from Einstein’smathematics, implying that there is an instantaneous transmission ofinformation. This is a very controversial notion; many theorists do not like thisfaster-than-light pathology. However, Bell (1966) has argued that, even inclassical reality, there must be a violation of the speed of light limit, otherwise,causal relationships lose their meaning.
‘Many worlds’
In 1957, Hugh Everett critiqued both the Copenhagen interpretation and vonNeumann’s views. Like von Neumann, he could not accept Bohr’s view that themeasuring apparatus and the observer occupied a privileged position in theclassical realm, arguing as von Neumann had that all was quantum stuff.
However, unlike von Neumann, Everett argued against the collapse of a givenwave function stating, correctly, that Schrödinger’s wave equation had no termsthat dealt with such a collapse. To overcome these difficulties, Everett postulated that there is no distinction between the quanta being measured andthe measuring set-up and that there is no collapse of the wave function. There isa universal wave function ψ for the entire universe and, at the point of makingan observation or measurement, the experience of the observer causes abranching of ψ into another world. Some writers interpret Everett as saying thatthe experience of the observer causes a branching of ψ into another universe.
Everett never said this. Rather, he implied branching of streams ofconsciousness. In addition, the term world has caused confusion and debate. It isnot that we have ‘many worlds’ (MW) branching from some primordial wavefunction ψ, but ‘many minds’(MM), each one of which experiences some givenunique quantum measurement result.
‘Many minds’
In the ‘many minds’ (MM) view, the experiencing of an observable secures anappearance in a process of decoherence, which is the untangling of the quantumstate to yield one unique result. The wave function ψ carries on evolving; hencethere is no intervention by the consciousness of the observer. Nor is there ameasurement problem because, at the point of measurement, there is nocontradiction between the quantum states and the experience of the observer. Inpractice, this means that where, for a given set-up, the solution to the wavefunction predicts a probability of both a yes and a no, one of the observer’sminds experiences a yes, and the other a no. The notion that there are ‘manyminds’ within a given observer seems to go against the usual view inconsciousness studies as a branch of psychology. However, we shall see that theMM view is well subscribed to.
At the lowest level of explanation we have what I will term the neurological levelof debate. The next level up is the psychological level. Finally, we have thephilosophical level of debate.
Neurological level
There are several key contributors to this aspect of the debate, for example,Beck (1994), Beck and Eccles (1992), and Hameroff and Penrose (1996).
At the root of this approach is the belief that the quantum realm directlyinteracts at the neurological level, and hence has an influence on consciousness.
There are two major problems that exponents of this view have to contend with.
Firstly, there is the issue of how quantum entities actually interact at the level ofneurons. Secondly, there is the issue of the relationship between neurologicalstructures and consciousness. Any successful theory at this level of explanationmust deal with both of these issues.
In tackling the first of the problems faced within this level of explanation,various neurological mechanisms become the focus of the likely interaction. ForPenrose and Hameroff (1996), it is the microtubule, whereas for Beck and Ecclesit is the all-or-nothing exocytosis of synaptic neurotransmitters. A part of theproblem here is how the infinitesimally small quanta can ever interact in aninfluential way with macroscopic structures such as a neuron. While the neuronis a small structure from our viewpoint, it is massive compared with subatomicstructures. In addition, there is the problem of how a wet, warm and electricallynoisy environment such as a neuron can support the precision of wave functioncollapse needed.
Penrose, with input from Hameroff, has chosen the microtubule because of itsvery small dimensions, where these are argued to be small enough to permitinfluential energy exchange. Penrose’s candidate mechanism for the quantum-microtubule link is his notion of quantum gravity — Penrose’s own discipline.
Within the debate surrounding this possible mechanism, it is still unclear as tohow the microtubule is involved in neuronal mechanisms (for example, thetransmission of information down the axon or across the synapse). It appearsthat the microtubule does not have an information-processing function. Rather,it serves as a support structure. But even if it were feasible that, on collapse ofthe wave function, information was somehow transmitted to a neuron, howdoes this moderate the neuron’s action? The collapse is characterised as an abrupt change of state — a switch-like action. This does not fit with the wayneurons work. Also, information passes between neurons across the synapticcleft, whereas the microtubules are structures within the neuron. It is not clearhow a collapse of the wave function, via a microtubule, causes the neuron tooperate in the way that we know that it does.
The approach by Beck and Eccles (1992) is somewhat more sophisticated, whichwe might expect because Eccles is a renowned neuroscientist. Beck and Ecclesargue that the interaction between quanta and brain occurs in the all-or-nothingexocytosis of synaptic neurotransmitters. They argue that exocytosis is the basicunitary activity of the cerebral cortex. Quantum entities interact at the atomiclevel, probably in the movement of a hydrogen bridge, by electronicrearrangement. This approach still suffers from the same basic problems asPenrose’s approach, in that we have the very small interacting withmacroscopic structures.
The problems surrounding the mode of interaction between quanta and neuralstructures are serious enough, but they pale in the face of the higher-orderproblem of the relationship between neural structure and consciousness.
Unfortunately, the key theorists at this level of explanation do not deal with thisdimension at all well. Hameroff and Penrose appear to sidestep the issue withtheir intense focus on microtubules. They (mainly Penrose of the pair) invokevague-sounding principles entailing Godel’s theorem, Platonic realms, andfeatures of consciousness such as non-computability. However, none of thisaddresses the fundamental issue of the relationship between neural activity andconsciousness. Beck and Eccles’ approach seems more plausible, if only becauseof Eccles’ past work on the neurological nature of consciousness. At least Beckand Eccles’ work offers some experimental support for the idea that inconscious willing, there is a selection process that appears to increase theprobability of exocytosis. But, in general, at this level of explanation, a greatdeal is skipped over, trivialised and simply avoided as to what consciousness isand how it arises from the brain’s activities.
Because the psychological literature is still very divided on the relationshipbetween consciousness and its neurological basis, it is bold of Penrose inparticular (Penrose; 1989, 1994 & 1997) to make the assumptions he does withvery few references to that literature. Penrose seems very anxious to find alink between quanta and neurons. This anxiety is highlighted in the critique ofan article by Penrose and Hameroff (1995), provided by Grush andChurchland (1995), in which the authors accuse Penrose especially of the pairof presenting arguments consisting of the merest possibilities piled atop evenmore mere possibilities.
With regard to Beck and Eccles, we are faced mainly with the issue of whetherquantum level activity can have an influence at the macroscopic level of thehydrogen bridge, hence at the neuronal level. I have not found a critique of thisargument, and feel unqualified to critique it myself. However, even assumingthis quantum-neuron mechanism is valid, it does not really address therelationship between consciousness and the neuronal level of activity. Whileexperimental support is offered for a relationship between conscious willingand exocytosis, much more work would have to be done to establish a causalrelationship between the experiencing of a given detector result in a quantumexperiment and the collapse of the wave function.
Scott (1996) does not see answers at this level of explanation coming fromquantum physics. He says that over the past few years there have beendiscussions on the role of quantum physics in explaining consciousness. On oneside are neuroscientists who assert that brain science must look to the neuronfor such understanding, on the other are physicists who suggest that quantumphysics might influence the dynamics of mind. Often, they seem to be talkingpast each other. Scott argues that classical non-linear theory obviates the needto turn to quantum physics. Scott states that there are fundamental problems inattempting to apply Schrödinger’s equation at the neurological level. He feelsthat most quantum physical approaches to consciousness ignore or discount thedeep explanatory power of classical non-linear dynamics.
Psychological level
Some of the key players at this level of the debate are Bohm (1951; 1952; 1987and 1990); Butterfield (1995); Donald (1990; 1997; 1999); and Lockwood (1996).
The challenge at this level of understanding is in explaining how consciousnessenters the equation. In classical experiments, there is no role for consciousness.
It does not enter the equations of motion, and outcomes are not dependent onthe observer. As explained in the introduction, it is quite the reverse withquantum mechanical experiments, where consciousness seems to enter at theoutset, and the observer’s role is crucial to the experimental results.
Bohr adopted an agnostic view in regard to the nature of the quantum realmand placed the conscious observer in the classical realm. He neither confirmednor denied a relationship between observers and quanta. Von Neumann and,later, Wigner (1967) were not happy with this stance. Von Neumann arguedthat all was quantum stuff, including the brain of the observer. For him, onlyconsciousness could hold a privileged position, in that consciousness was not a part of the physical universe but was res cogitans. Wigner (1967) went further,arguing that it was the consciousness of the observer that caused the collapse ofthe wave function, converting a probabilistic state into a measurement result.
As we saw above, Everett introduced what has become known as the ‘manyworlds’ (more properly, ‘many minds’) theory.
Bohm’s views have changed over the years of his involvement in the quantumtheory. In his early work, Quantum Theory (Bohm, 1951), there appears to be acomplete allegiance to the Copenhagen interpretation. There is only a slight hintof his subsequent departure from the fold in his attempts to define whathappens at the quantum level. This all changes in 1952, with his paper inPhysical Review (Bohm, 1952), in which he talks of hidden variables as a solutionto some of the paradoxes thrown up by quantum theory. Some time later, histrue neo-realist persuasions emerge (Bohm, 1987) when he declares that he isanti-Cartesian, being against the mind-body split. He saw psyche-soma as beingtwo aspects of the one reality. Shortly after (Bohm, 1990), he introduces hisnotion of an implicate and explicate order, in which the former is the substratefor all reality (reality folded up) and the latter is the world of space-time(unfolded from the implicate order).
In a quite different direction, Butterfield (1995) looks at the interpretive problemin terms of consciousness or mind. He explores the issues of the indeterminacyat the quantum level, and the seeming determinacy at the classical level, andhow one reconciles the paradox. He identifies two basic approaches: an indefinite macro realm, in which one can only secure appearances.
It is the latter approach that leads to the MW/ MM views. Butterworth arguesthat the distinction between the MM and MW views is delicate and that Everettintended the former. Orthodox quantum physics suggests that the electron’sindefiniteness is transferred to the apparatus, but, at the collapse of the wavefunction, the measured system goes into the eigenstate corresponding to theresult obtained. Butterfield further argues that, with regard to the MW/MMviews, one assumes that the entire universe has a pure quantum state ψ. Onetakes ψ to be a superposition of states corresponding to many different definitemacro realms, where all these realms are actual. The idea is that the world splitsat each measurement, like a tree into branches, with ‘daughter worlds’ for eachresult. However, if all branches are actual, why can we not see all of them? TheMW theorists argue that, after splitting, the daughter worlds have no access toone another. Plurality represents a contrast between MW and other no-collapseinterpretations.
Donald (1990) notes that a functioning brain is wet and warm and of greatcomplexity. This creates difficulties for physicists who try to describe it inquantum terms. He proposes the notion of the brain as a family of thermallymetastable switches. Donald analyses the problems of characterising a two-element switch in quantum terms. In using the neural model, Donald admitsthat neurons are not simple. In quantum terms, the neuron is a macroscopicobject of great complexity. Even the idea of ‘firing', as a unitary process, issimplistic. Donald uses the sodium channel model, which can behave as aquantum switch. In this approach, the original state of the universe ϖ is notbeing split into a multitude of different ways in which it can be experienced.
This was the basis of the von Neumann collapse scenario. Donald simplycalculates an a priori probability for any of the ways in which ϖ can beexperienced. It is the least condition on the quantum state of the world that willallow brains to process definite information, as this minimises the necessity ofwave function collapse. The sodium channel is one that, when open, allowssodium ions to cross the cell membrane. It is closed through twodistinguishable processes. One is responsive to the voltage across themembranes and opens following depolarisation. The other closes the channelduring depolarisation. After the membrane returns to its resting potential, theactivation gate closes, the inactivation gate reopens, and the cycle is complete.
Finally, there are the ideas of Lockwood (1989; 1996). Lockwood (1996) pointsout that, seventy years after the emergence of quantum theory, there is still noconsensus as to how the theory should be understood. In quantum physics,possible states of a physical system are represented by vectors in Hilbert space,which can be multiplied by coefficients and added together so as to yield newvectors, which stand for states said to be in superposition. The strange logic ofquantum theory is illustrated by electron spin, which may be up (clockwisearound spin axis) or down (counterclockwise). In any given direction thevectors representing any pair of spin states, spinup and spindown, are at rightangles in Hilbert space. Any arbitrary spin state can be expressed as asuperposition of these two states. If an electron is spinup in a given direction,and we measure the component of spin angular momentum in that samedirection, we get a positive value; for spindown we get a negative value. Inclassical mechanics, spin states in directions other than the same or oppositewould yield intermediate values between spinup and spindown. Not so inquantum theory. We still get either spinup or spindown, but with probabilities,which can be determined by expressing the electron’s spin state as asuperposition of spinup and spindown in the direction of measurement. This isthe quantisation that gives quantum physics its name.
Lockwood notes that, in general, the probability of getting a given result(eigenvalue) in a measurement is the square magnitude of the coefficientattached to the corresponding eigenstate, when the state of the system isexpressed as a superposition of the eigenstates of this observable. Measurementprojects the system into the corresponding eigenstate. The effect ofmeasurement transforms the system. This is known as the state-vector reductionor collapse of the wave function. Lockwood argues that this collapseinterpretation ostensibly conflicts with the predictions of quantum theory sinceany such physical transformation would represent a departure from the so-called unitary evolution prescribed by the Schrödinger equation. One wayaround this is to modify the Schrödinger equation to allow for collapse (so far,this has not been satisfactorily done). Another line is the hidden variableapproach (Bohm), which eliminates collapse and in which collapse is viewed asour ignorance of the prior state. However, as Lockwood points out, thisapproach has its own problems due to entanglement (electrons in a singletstate). In such a singlet state we have an example of quantum holism, whereinthe whole transcends the sum of its parts. The entangled pair of electrons doesnot possess individual spin states. There is a quantum correlation between thespin states.
Lockwood (1996) classifies Everett as an MM theorist. Instead of postulating aninfinity of worlds, we could credit every sentient being with a continuousinfinity of simultaneous minds, which differentiate over time. Withoutreduction or hidden variables, quantum theory is deterministic. This createsproblems for the probabilistic notions in the theory. Also, it is difficult to seehow the mind of an observer could be in superposition. If we have astochastically evolving mind harnessed by a deterministically evolving brain,we encounter the ‘mindless hulk’ problem. Advocates of the MW view mustconcede that there is a sense in which there is only one universe (a multiverse).
Likewise, the MM advocate could concede to there being only one mind perperson (a multimind).
Philosophical level
There are several theorists at this highest level of explanation, the chief of whichare Bilodeau (1996), Esfield (1999), Squires (1993; 1994) and Stapp (1993; 1996;1998; 2000). The challenges at this level are bound up with Cartesianepistemology and ontology, in the spectrum from naïve realism, throughbrands of dualism, to idealism.
Bilodeau (1996) argues that, if the foundations of physics are so controversialthat no agreement can be reached on the meaning of physical concepts, thenphysics is hardly a suitable basis for a discussion of the ontology of mind.
Bilodeau argues that the notion that the world is made of inanimate matter wasa convenient convention — Descartes aimed to separate mind as far frommatter as he could by affirming the physical world as geometric and mind asnon-spatiotemporal. However, physics has had to include concepts that arenon-geometric (for example, the field-approach in electromagnetics). But fieldtheory posed no threat to the Cartesian split, whereas quantum theory does.
Bohr realised that no sharp distinction could be made between subject-objectwithin the theory. However, Bilodeau points out that Bohr’s writings weredifficult and obscure, and the authorities became Dirac and von Neumann, thelatter violating Bohr’s taboo. Von Neumann portrayed the collapse of the wavefunction as a physical event, thus opening the door to the measurementproblem and all its offspring (for example, Schrödinger’s cat, Wigner’s friendand even the ‘many worlds’ concept). Also, Bilodeau asserts, any defence ofBohr’s warnings has been seen as defeatism in the face of the quest for theobjective quantum state; for example, the ‘many worlds’ view is seen as daringand radical, yet is merely the defence of objectively describing the universe.
According to Bilodeau, our analytical habits have much more to do with theway our minds work than with the way nature really is. The notion of aphysical substrate arises from an oversimplified view of how we observe andanalyse the physical world. Descartes created the geometric world by removingthe subjective self from it entirely. Today, those committed to the ontologicalprimacy of the physical world must show it to exist completely independentlyof the subjective by showing how this dimension can arise from a purelyphysical world.
The hard problem of phenomenal consciousness, Bilodeau argues, is really theinconsistency with our own experience of a complex of beliefs about thephysical world. Matter is inanimate and mechanical, its ontology mathematical,so that all its properties are properties of form or structure. It is divisible intocomponents so that the properties of the whole are implied by the properties ofthe parts plus their spatial relationships. The next step is to transcend the hardproblem by accepting a richer non-mechanical ontology. This is not physicalismnor idealism nor dualism. It is a view of reality as a unified process in which weare participants and which we can conceptualise in many ways in accordancewith the many kinds of knowledge we can have of the world. Bilodeau feelsthat, while it is natural for us to use machine analogies, we can hardly expectthat that which the mind readily produces is the same as that which producesthe mind. Mind is surely not epiphenomenally superimposed on a pattern of information processing that the brain happens to enact. It is more plausible thatthe brain and mind are both manifestations of an underlying process, and thatour own ego awarenesses are merely the tip of an ontological iceberg as yetunknown to us.
Esfield (1999) looks at the seemingly holistic nature of the quantum realm andthe implications for consciousness and everyday reality. He talks of the currentrevision of the Cartesian tradition along the lines of direct realism andexternalism, and asks if the features of quantum physics concern only themicrophysical world or if they extend to the macroscopic. He argues thatendorsing the latter entails a commitment to certain consequences in thephilosophy of mind. Quantum measurements imply a quantum holism, as inexperiments with entangled photons (Alain Aspect’s experiment — Aspect etal., 1981). However, Esfield notes that current anti-Cartesian developmentsmake a strong case against quantum holism touching the macro realm. Yet, inthe von Neumann view, entanglement propagates to the macro realm. Esfieldassumes that quantum theory tells us something about the natural world, andstates that the following features of the quantum realm must be taken intoaccount: non-localisation, entanglement, and non-individualism. In terms ofhow the quantum world leads to the classical world, Esfield argues for twobasic options: One can maintain that entanglement does not propagate to higher levels ofmacroscopic systems. This is limited quantum holism. However, this entailssome modification of Schrödinger’s dynamics.
One can conceive of quantum holism as extending to all physical systems.
This option is universal quantum holism. That is, the physical world is ahuge quantum system whose internal structure consists in ubiquitousentanglements. The implication is that everything at the macroscopic level isentangled.
Esfield further argues that the option for universal quantum holism calls thephilosophy of mind into play. Two main strategies appear in the literature: Abstraction from entanglement by the observer such that the world appearsto the observer as described by common sense and higher level theories.
The ‘many minds’ of the observer, wherein each term in a superposition iscorrelated with at least one mind of the observer. Thus each mind sees theclassical world.
Esfield points out that there is a thrust toward the revision of Cartesianepistemology. There are two theses within this position: Representationalism: Persons have access to the world only by means ofmental representations, which act as an epistemic intermediary.
Internalism: The individuation of intentional states and their identitydepends only on factors that are immanent to the person having thesestates.
Current anti-Cartesianism consists of replacing these two theses with directrealism and externalism. Esfield states that the former is the claim that there areno epistemic intermediaries between perceptual beliefs and the world. We aredirectly aware of things and events in the world. Externalism claims that wemust be embedded in a physical and social environment to have intentionalstates. Esfield asks, what are the consequences of adopting holism in regard toepistemic access to the world? In one MM view, all our beliefs about perceptibleobjects are false. In holism, there is the implication that things do not objectivelyhave the definite properties that we ascribe to them in our perceptual beliefs.
Their objective states are nothing like we conceive them to be. Externalismappears to be incompatible with the option of quantum holism. As a result ofuniversal entanglement, the physical environment of an observer does notobjectively have that definiteness that is a prerequisite for its being able tocontribute to the individuation of the observer’s intentional states. Likewise, theuniversal holism option cannot go with direct realism. Endorsing universalholism commits one to the position that the objects of our perceptual beliefs aredependent on the conditions of our observation of them (the abstraction fromentanglement). In fact, the quantum holism option implies a commitment torepresentationalism in that there is an epistemic intermediary. Esfield arguesthat we face two philosophical packages: We can opt for universal quantum holism in the physical realm. In this, wemust counter arguments against epistemic self-sufficiency.
If one approves of direct realism and externalism, one cannot commit touniversal quantum holism.
However, Esfield says that we could conceive of quantum holism as beinglimited only to the microscopic realm and so favour representationalism. Onecannot approve of the revision and construe holism as concerning the wholephysical realm. A comprehensive holism includes both the physical and mental,and could replace the Cartesian tradition. If we regard the mental and physicalas complementary aspects of being, we are committed to an ontology of psycho- physical parallelism (for example, Spinoza). Esfield argues that, by conceivingof quantum holism as touching the whole physical realm, one is committed tothe Cartesian epistemology.
Squires (1993, 1994, 1998) looks at the relationship between quantum theory,events in the macro world, and consciousness. He points to the problemssurrounding the Stern-Gerlach experiment (Squires, 1993), in which electronspin states are investigated. In particular there is the measurement problem thatarises when the spin is in some direction other than z, which gives rise tocomplex coordinates and a superposition of states, only one of which canactually be detected. Squires goes on to say that, since quantum physicalequations do not contain what we observe, either the equations are wrong orwe must add equations. In the first approach, the idea is to add non-linearelements to the Schrödinger equation. The effect of this is to collapse the waveat a certain rate to eigenstates of positions. In this way, the particles will havedefinite positions. The rate of collapse is chosen to be so slow as to have nodiscernable effect in ordinary experiments. Because stochastic processes areinvolved in quantum physics, a random white noise process is needed in themodified Schrödinger equation. In this approach, only when the detectionapparatus, which is macroscopic, becomes correlated to the particle directiondoes the determination occur. The alternative method, which came from deBroglie and Bohm, assumes that physical reality has two parts: the usualclassical world of particles moving along trajectories, and a quantum force. It isthen easy to find the unique expression, in terms of the wave function, for whatthis force has to be in order that the statistical predictions of quantum physicshold exactly.
Finally, at this level of discussion, we can look at the views of Stapp (1993, 1996,1998, 2000). Stapp (1996) argues that, in principle, it should be possible todeduce all of the internal processing that occurs in our bodies and brains fromthe principles of classical mechanics. However, one cannot deduce feelings(qualia) from classical principles. Do we conclude that consciousness andfeelings are part of a full description of nature, yet play no efficacious role inclassical mechanics? Or do we conclude that certain implemented functional orlogical structures are conscious experience? The first makes no sense, and theproblem with functionalism is that classical principles are too impoverished todeal with feelings and experience. Conversely, quantum physics brings in theexperience of observers. The Copenhagen approach is essentially dualisticbecause it deals with experience and the mathematical algorithms.
The Copenhagen claim is that physical theory is about our classicallydescribable perceptions of the world. In some experimental situations in quantum physics, the observed results do not match the predictions of a givenwave function. Stapp (1996) goes on to argue that the Copenhagen Schoolresolved this contradiction by postulating that the quantum state represents notthe full reality itself, but rather the probability of our perceptions being variouspossible perceptions. Only in this way can quantum physics account for theclassicality of our observations (which quantum physics does not entail orallow). In this, we see that the matter-like consideration gives only half of theontological story. Thus, we have a dualism, one part of which is mind and theother part of which is the Schrödinger equation. However, as Stapp points out,some theorists have avoided this dualism (see Bohm’s model).
Stapp (1996) then goes on to outline his ontology. In summary, he seesconsciousness as playing a causal role. It is not determined. He denies purechance, saying that it is unacceptable in an ontological interpretation. Stappargues that, if quantum events occurred at the neuronal level, there would beno free will, in that there would be no high-level choice entailed. Stapp’s modelavoids both the Scylla of a fate sealed at the birth of the universe and theCharybdis of wild chance. The intricate interplay between chance anddeterminism within quantum physics frees the organism to pursue goals basedon its own values. The element of pure chance reflects our ignorance regardingtrue causes.
At the neurological level there are two key issues: How does a quantum entity interact with the relatively massive neuron? What is the relationship between neurons and consciousness? At the psychological level there are several issues: Does consciousness influence the wave equation? If consciousness does influence the wave equation, how does it do thiswhen there are no terms for consciousness in Schrödinger’s equation? The Copenhagen interpretation versus the rest.
‘Many worlds’ versus ‘many minds’.
At the philosophical level there are several issues: Matter is no longer the substance that Descartes considered.
Quantum holism and the classical world.
Although it would make sense to deal with these issues under their separateheads, there is too much interaction across them for this to work in an orderlyway. Therefore, I will look at the following issues and deal with anyinteractions across levels of the debate within that context.
Quantum-neuron interaction
This is a fundamental issue. Even if we are unsure as to exactly how it occurs,that quantum-neuron interaction must occur is essential to claims about arelationship between consciousness and the quantum realm. The two mainproponents of an interaction at this level are Penrose and Eccles. There appearsto be no empirical evidence in support of Penrose’s claim that the microtubuleis the mechanism. Even the microtubule, small as it is, is still a massive structure when compared with quantum entities (assuming these to be fermionssuch as the electron). Eccles’ view seems more plausible in that his proposedhydrogen bridge mechanism is closer in size and energy level to quantumentities. But again, there is no clear evidence that there can be such aninteraction, despite the claims of Beck. This issue spills over into other levels ofthe debate, and certainly comes into the MW/MM theories. Even though theseare no-collapse theories, an interaction between the quantum realm andneurons is necessary (for example, in Donald’s MM approach, where he usesthe sodium channel as a quantum switch.) Until more work is done to revealthe link between quantum events and biological structures, the claimants for aquantum-neuron interaction are on shaky ground.
Neurons and consciousness
Even if a causal relationship is established between quantum events andneurons, there remains the even bigger challenge of showing the relationshipbetween neurons and consciousness. None of the authors presented in thisreview appear to come even close to answering this challenge. Again, althoughthis issue is central to the claims of those such as Hammeroff and Penrose andBeck and Eccles, they present no really convincing model. The challenge ofexplaining this relationship is not just a problem for those interested in thedebate reviewed here; it is a major challenge within consciousness studies ingeneral. One cannot deal with it without bringing in the Cartesian dichotomyand Chalmers’ hard problem (Chalmers, 1996). This issue impinges on all levelsof the debate reviewed here. If the likes of Donald are correct in their claimsabout the mode of interaction between quantum events and neurons, how dowe reconcile this with the major view among consciousness theorists thatconsciousness is not locatable in any given group of neurons? Donald implies abasically on-off switching mode of interaction at the neuronal level. Further,there seems no suggestion that quantum events are interacting across largegroups of neurons during the collapse process. Rather, the implication is thatthere is interaction between small numbers or even single neurons. Yetconsciousness seems to pervade brain activity cortically and sub-cortically.
How do we reconcile this with the simple one-on-one interaction implied bythose subscribing to the consciousness-determined collapse model? If thismodel is to be validated, then not only must the quantum-neuron link be clearlyestablished, it must be shown that the group(s) of neurons involved in a simpleobservation are part of this interaction.
Consciousness and the wave equation
A major challenge here is to show how consciousness comes into Schrödinger’swave equation. There are no terms in that equation that representconsciousness. It is a linear, time-dependent equation that was derived fromclassical principles and hence does not take consciousness into account. If therewas a consciousness-controlled collapse, then the equation would have to bemodified to contain terms for consciousness. Seeing that consciousness is notreadily definable at the neuronal level, what form would these terms take?Leaving aside the vexed issue of consciousness for the moment, the brain is aclassical structure and an amazingly complex one at that. While aspects of itsoperation are still a mystery, it does obey the classical laws of physics,chemistry and biology. Thus, ultimately, it succumbs to the equations ofmotion, even though, as Scott (1996) points out, it demands a non-linearclassical approach. In view of all this, it is very hard to see what form themodifications to the wave equation would take.
Copenhagen versus the rest
There are those who have seen Bohr’s agnosticism as defeatist (for example,Bohm, 1952) and who insist that there is a real substratum to the classical worldof the senses. Such thinkers see this as an issue of the maturation of quantumphysics and not as an issue of fundamental ignorance; that is, once we have afully mature quantum physics, we will have a full and direct understanding ofthe nature of the quantum realm and know its hidden laws. Some (for example,Bilodeau, 1996; Esfield, 1999) regard this as a pious hope, even as a return to the‘innocence of our youth'. They imply that, now that we have been faced withthe alien nature of the quantum realm, there is no turning back from anacceptance of its ineffability.
The views of Bilodeau and Esfield support Bohr’s agnostic stand, in that we havecome up against an ultimate mystery and will never have the tools to directlyinvestigate it. We have developed a mathematics that provides very high levels ofpredictive power, but we do all this from the basis of our conditioning in theclassical realm of sense data. The best we can do is to take an inferentialapproach. Direct observation is beyond us. We can only ever make measurementsfrom within the classical realm. Concepts such as electrons and photons are veryuseful, but they are only concepts. We seem to be left with a fundamentalignorance of what they truly are, even whether they exist as such. Because we canonly talk, hence conceptualise, from our embodiment in the classical realm, weneed to guard against imposing our conditioning on the quantum realm andagainst requiring it to have some kind of reality that we can grasp.
We have seen that various theorists, for a variety of reasons, have rejected theCopenhagen interpretation. Von Neumann objected to the quantum-classicalsplit, arguing that everything was made of quantum stuff. He did not denyBohr’s basic complementarity principle (the wave-particle duality referred toearlier), or the indeterminacy it implied. Bohm, on the other hand, by 1952(Bohm, 1952), had parted company with the Copenhagen School and wasinsisting that the quantum realm was real and contained hidden variables. Herejected the indeterminacy notion, saying that the problem lies in our ignoranceof the hidden variables and not in fundamental quantum ignorance. For the‘many worlds’ and ‘many minds’ theorists, the issue has centred on themeasurement problem and its resolution. There has not been a concern withBohr’s basic stance.
‘Many worlds’ versus ‘many minds’
Everett’s radical approach to the measurement problem led to the MW and MMinterpretations. Both approaches are no-collapse theories, and their protagonistshave not had to worry about whether the quantum realm is real or not. Theconcern, for these theorists, is the interaction between the Schrödinger waveequation and the experience of the observer of a quantum physical experiment.
The major difference lies in what occurs at the point of observation. In the MWview, observation leads to the branching off of a new world, whereas in the MMview, there is only the one universe, but a multiplicity of minds within a givenobserver, one of which is uniquely connected with a given experience. Oneproblem with the MW view is that there is no way of demonstrating it. Once asplit has occurred, the new world is completely isolated and follows its ownunique history. In the case of the MM view, there does seem some possibilityfor empirical investigation, in that what is happening is all within the singlebrain of the observer, in one single universe. There are ways in which the MMview is the most parsimonious of the interpretations explored here (leavingaside the original Copenhagen version). It does not need to deal with anythingother than the Copenhagen ontology (which is a no-ontology!) There is noimposed collapse of the wave equation, hence the original Schrödinger equationsuffices, and there are no hidden variables.
MM’s major challenge is the relationship between the quantum realm at thepoint of observation and the specific mind of the observer at that point. Thischallenge has already been looked at above under the quantum-neuroninteraction. While it has not yet been satisfactorily addressed, it is at leastwithin Chalmers’ ‘easy’ category (see shortly), and so is amenable to a scientific-technological investigation and explanation. Clearly, a lot more than just theorising is needed now. We need to see some solid experimentation. Therehas been a great deal of the former, as evidenced in this paper. I have not comeacross any of the latter.
The Cartesian dichotomy
This issue is fundamental to interpreting quantum theory. It is at the root of theagnosticism of the Copenhagen interpretation. In a quantum physicalexperiment we have the hardware (including any computer software) of theexperimental set-up and the brain of the experimenter-observer. From theviewpoint of the classical world, there is nothing else. In attempting to interpretthe theory in terms of the classical findings, we introduce the notions of a mind(of the observer) and of a quantum realm, neither of which are tangible, sense-data objects. In the case of a mind (of the observer), we have introducedDescartes and the whole conundrum of how the brain and mind might interact.
By introducing the notion of a quantum realm we have raised issues about whatDescartes meant by matter. It seems fairly clear from quantum theory thatDescartes’ concept of matter as simply res extensa does not apply. Perhaps weneed a new term such as res incorporeal to describe matter in a fundamentalway. The putative quantum realm does not behave at all in the way Descartes’res extensa behaves. The notions of space and time appear to have no meaningat the quantum level, where it appears to be an undivided whole.
How therefore, are we to view Descartes’ original dichotomy? If the holistic-supraluminal nature of the quantum realm is universal, extending to the so-called classical realm, then we have gone a long way toward doing away withthe Cartesian dualism. However, we still have to deal with Descartes’ rescogitans. Are we to assume that ‘mind’ is a classical phenomenon and thus apart of the holism of the quantum realm? Or do we assume that ‘mind’ issomething quite apart from the classical realm? If we adopt the first notion,then we have done away with dualism, in which mind becomesepiphenomenal. However, if we go along with Esfield (1999), who assumes thatquantum theory tells us something about the natural world (classical world),then we must also agree with him that the following features of the quantumrealm must be taken into account: From this basis, Esfield argues for two basic options. One is that of limitedquantum holism, in which the entanglement does not propagate to higher levelsof macroscopic systems (mainly those above the molecular level). The secondoption is that of universal quantum holism, in which entanglement extends toall physical systems in the classical world. In this view, the entire physicaluniverse is seen as one huge quantum system. Esfield points out that neitherdirect realism nor externalism are valid approaches for either of his twooptions. We are left with accepting that there is an incompatibility between thenature of the world and how we conceive it to be, and so we are faced with theneed for an epistemic intermediary. This means that we must accept that rescogitans is different from res extensa, as Descartes held.
Chalmers’ hard problem
The previous section leads naturally onto the consideration of Chalmer’s ‘hard’problem (Chalmers, 1996). Chalmers sees the mind-body dichotomy as fallinginto an easy and a hard part. The easy part deals with technical problems, thesolution to which is a matter of the maturation of some given discipline (forexample, psychology or quantum physics). The hard part deals with ontologicalproblems, with which only philosophy is equipped to deal. For Bilodeau (1996),Chalmers’ hard problem arises out of the tension between the seemingontological primacy of the physical world and the subjective sense we allexperience. One cannot easily show how this sense arises out of a purelyphysical world, hence the ‘hard’ problem. It is our subjective sense that makesthe physical world appear as ‘objective'. If Esfield’s analysis is valid, then mindor consciousness acts as an epistemic intermediary with the objective world andso is different from it. Thus, we are stuck with Chalmers’ hard problem. It won’tgo away.
Recall that we started by looking at the quantum theory and the weirdness of itspostulates. We saw that the principles of indeterminacy and wave-particlecomplementarity are fundamental tenets. At root, the quantum realm isprobabilistic in nature, where the probabilities are realised only in experimentalsituations in the classical realm. While we like to conceptualise quanta as wavesor particles or both, these are merely conceptualisations and do not describequanta. There is an implied holism at the quantum level that pushes outclassical imagination to its limits and beyond. The classical world’s smoothnessand solidness appears to be the result of statistical aggregation and has no ultimatesubstance that we can grasp. The measurement problem centres on the seeminginfluence of the observer over the collapse of the wave function. Only when wemake a measurement do quanta actualise.
So, bearing the above brief summary in mind, where does this review andanalysis leave us? It is clear that the debate considered in this paper is still verymuch alive, and that the findings of quantum theory and experimentation areimportant to consciousness studies. Although the views looked at in this revieware interesting, they all seem to be faced with immense challenges. Those arguingfor a collapse view must explain how the Schrödinger equation is to be modifiedto permit consciousness to bring about collapse. Furthermore, they must explainhow quantum entities interact with the neuronal structures of the brain. Beyondthis is the challenge of explaining the relationship between neuronal structuresand consciousness. The neo-realists have taken on a difficult mathematicalchallenge, and do not have a very parsimonious theory. While one mightsympathise with their longing for a ‘real’ substrate to the natural world, thislonging seems to lead to a retrograde view that ignores the totally non-classicalnature of the quantum realm. The ‘many worlds’ view does appear to get arounda number of problems faced by some other views. However, it is not open toempirical investigation: once split off, each world is isolated from all others.
For me, the most plausible view reviewed here is that of the ‘many minds’. I saythis because it appears to be the most parsimonious, and seems to lend itself toempirical experimentation. Because it is a no-collapse interpretation, it is notconcerned with difficult modifications to the Schrödinger wave equation. Also, it isnot concerned with hidden variables. Its challenge lies in explaining how ‘minds’come into being as a result of entanglements between the quantum realm and theclassical realm. It also has to deal with the more philosophical aspects of itsposition, as discussed under the Cartesian dichotomy and Chalmers’ hard problem.
It is hoped that this paper will spark further analyses of this fascinating debate, andhelp to keep it alive. The writer will continue to watch with interest as the debateunfolds to see how each view fares.
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