sorates and branestawmQuentin Ruyant has written a thoughtful piece about quantum mechanics and philosophy of mind: in a nutshell he argues both that quantum theory may be relevant to the explanation of consciousness and that consciousness may be relevant to the interpretation of quantum theory.

Is quantum theory relevant to consciousness? Well. of course some people have said so, notably Sir Roger Penrose and Stuart Hameroff.  I think Ruyant is right, though, that the majority of philosophers and probably the majority of physicists dismiss the idea that quantum theory might be needed to explain consciousness. People often suggest that the combination of the two only appeals because both are hard to explain: ‘here’s one mystery and here’s another: maybe one explains the other’. Besides, people say, the brain is far too big and hot and messy for anything other than classical physics to be required

In making the case for the relevance of quantum theory, Ruyant relies on the Hard Problem.  His position is that the Hard Problem is not biological but a matter of physics, whereas the Easy Problem, to do with all the scientifically tractable aspects of consciousness, can be dealt with by biology or psychology.

Actually, turning aside from the main thread of Ruyant’s argument, there are some reasons to suggest that quantum physics is relevant to the Easy Problem. Penrose’s case, in fact, seems to suggest just that: in his view consciousness is demonstrably non-computable and some kind of novel quantum mechanics is his favoured candidate to fill the gap. Penrose’s examples, things like solving mathematical problems, look like ‘Easy’ Problem matters to me.

Although I don’t think anyone (including me) advocates the idea, it also seems possible to argue that the ‘spooky action at a distance’ associated with quantum entanglement might conceivably have something to tell us about intentionality and its remarkable power to address things that are remote and not directly connected with us.

Anyway, Ruyant is mainly concerned with the Hard Problem, and his argument is that metaphysics and physics are closely related. Topics like the essential nature of physical things straddle the borderline between the two subjects, and it is not at all implausible therefore that the deep physics of quantum mechanics might shed light on the deep metaphysics of phenomenal experience. It seems to me a weakish line of argument, possibly tinged with a bit of prejudice: some physicists are inclined to feel that while their subject deals with the great fundamentals, biology deals only with the chance details of life; sort of a more intellectual kind of butterfly collecting.  That kind of thinking is not really well founded, and it seems particularly odd to think that biology is irrelevant when considering a phenomenon that, so far as we know, appears only in animals and is definitely linked very strongly with the operation of the brain. John Searle for one argues that ‘Hard Problem’ consciousness arises from natural biological properties of brain tissue. We don’t yet know what those properties are, but in his view it’s absurd to think that the job of nerves could equally well be performed by beer cans and string. Ruth Millikan, somewhat differently, has argued that consciousness is purely biological in nature, arising from and defined by evolutionary needs.

I think the truth is that it’s difficult to get anywhere at this meta-theoretical level:  we don’t really decide what kind of theory is most likely to be right and then concentrate on that area; we decide what the true theory most likely is and then root for the kind of theory it happens to be. That, to a great extent, is why quantum theories are not very popular: no-one has come up with a particular one that is cogent and appealing.  It seems to me that Ruyant likes the idea of physics-based theories because he favours panpsychism, or panphenomenalism, and so is inclined to think that the essential nature of matter is likely to be the right place to look for a theory.

To be honest, though, I doubt whether any kind of science can touch the Hard Problem.  It’s about entities that have no causal properties and are ineffable: how could empirical science ever deal with that? It might well be that a scientist will eventually give us the answer, but if so it won’t be by doing science, because neither classical nor quantum physics can really touch the inexpressible.

Actually, though there is a long shot.  If Colin McGinn is partly on the right track, it may be that consciousness seems mysterious to us simply because we’re not looking at it the right way: our minds won’t conceptualise it correctly. Now the same could be true of quantum theory. We struggle with the interpretation of quantum mechanics, but what if we could reorient our brains so that it simply seemed natural, and we groped instead for an acceptable ‘interpretation’ of spooky classical physics? If we could make such a transformation in our mental orientation, then perhaps consciousness would make sense too? It’s possible, but we’re back to banging two mysteries together in the hope that some spark will be generated.

Ruyant’s general case, that metaphysicians should be informed by our best physics is hard to argue with. At the moment few philosophers really engage with the physics and few physicists really grasp the philosophy. Why do philosophers avoid quantum physics? Partly, no doubt, just because it’s difficult, and relies on mathematics which few philosophers can handle. Partly also, I think there’s an unspoken fear that in learning about quantum physics your intuitions will be trained into accepting a particular weltanschauung that might not be helpful. Connected with that is the fear that quantum physics isn’t really finished or definitive. Where would I be if I came up with a metaphysical system that perfectly supported quantum theory and then a few years later it turns out that I should have been thinking in terms of string theory? Metaphysicians cross their fingers and hope they can deal with the key issues at a level of generality that means they won’t be rudely contradicted by an unexpected advance in physics a few years later.

I suppose what we really need is someone who can come up with a really good specific theory that shows the value of metaphysics informed by physics, but few people are qualified to produce one. I must say that Ruyant seems to be an exception, with an excellent grasp of the theories on both sides of the divide. Perhaps he has a theory of consciousness in his back pocket…?


  1. 1. Jochen says:

    There may be a middle ground here. Considering the idea that we might just be constitutionally incapable of coming up with an explanation of precisely how the mind gives rise to all these peculiar subjective feels, the painfulness of pain and redness of red, it might be that quantum mechanics introduces the necessary ‘raw materials’ in the world that we can use, but whose effects we can’t grasp.

    A model for this sort of thing might be that explanation is necessarily algorithmical—i.e. that an explanation for something corresponds roughly to an algorithm that describes how that something comes about, given the right circumstances. Then anything nonalgorithmical would be inexplicable. But quantum mechanics can produce ‘true’ randomness, which is nonalgorithmical, i.e. which can’t be faithfully reproduced by any algorithm. And agents with a source of true randomness can do some things agents lacking one can’t. This is not to say that I espouse the Penrose/Hameroff model; indeed, I got the idea from a paper arguing against it, “How Gödel’s Theorem Supports the Possibility of Machine Intelligence” by Taner Edis.

    He brings an amusing example with the case of a cop, let’s call her Maggie, tasked to catch a robber who can be in either of two houses. The police manual supplies a search strategy for such a case, which Maggie follows perfectly. But what if the robber is an ex-cop, who knows the strategy as perfectly as Maggie? He would forever be able to elude her: if she searches house 1, he’d be in house 2, and vice versa.

    But now say Maggie has a source of randomness, say a watch that goes ‘ding’ at random times. Whenever it goes ‘ding’, she switches houses. It’s clear that now there’s no deterministic strategy that can be used by the robber to elude her; but even more so, if the robber used a random strategy as well, she’ll nevertheless catch him in the long run. Access to randomness has fundamentally changed the game and given Maggie a new capability she did not possess beforehand.

    Now suppose that Maggie, due to her flawless field performance, one day becomes a lecturer at the police academy, where she is to teach new recruits her methods. But the problem is—she won’t be able to explain them! That is, she won’t be able to provide the recruits with an algorithm that allows them to always catch the robber—any such algorithm would be defeasible, as opposed to the random strategies. So it follows that the recruits can only replicate her performance if they themselves have access to a source of randomness.

    So, what have we learned? Maggie, through being given access to randomness, has been endowed with a capacity that she herself can’t explain, and that she can’t communicate. Moreover, no amount of learning, of ‘book kowledge’, allows anybody to replicate her performance—in order to do so, it would be necessary to have access to the randomness from the outside world.

    This has some interesting links, it seems, with the story of Mary trying to understand color vision in her monochrome room—like one of Maggie’s students, or Maggie herself before she was given access to randomness, nothing she learns (or so the common intuition tells us) will enable her to learn the capability of evoking colors ‘before her inner eye’; only access to the proper stimulus from the outside world does.

    If this analogy holds any water, then it might be that like Maggie needed to have access to randomness in order to learn her new ability, we need access to something (not necessarily randomness, but it is intriguing that QM seems to produce just that, and moreover, that extending a formal system with digits of a random number—by Chaitin’s theorem—is equivalent to extending it with theorems it can’t prove in the Gödelian sense) produced by quantum mechanics, which induces in our brains a change that we can neither explain nor communicate, capturing some of the most characteristic qualities of qualia.

  2. 2. Jayarava says:

    A little while ago I watched an interview with David “Hard Problem” Chalmers and was very disappointed to discover that he was openly advocating dualistic substance ontology. The hard problem is definitely and irrevocably intractable to a substance dualist partly because of the epistemology that inevitably seems to go along with substance dualism, which is that the mind substance is not knowable. So it won’t ever matter what an empiricist says they have observed because by definition the mind is not observable. The Hard Problem will always be defined as beyond what we currently know.

    Us substance monists (or at least those who, unlike Chalmers, deny Cartesian style mind/body duality) tend to believe the problem to be tractable. And point to the fact that this very young science has made remarkable progress in observing how minds function.

    One philosophical stance predicts we’ll never know, and that trying is pointless. Another predicts that if we look we’ll see interesting stuff and maybe we’ll understand it all eventually. The former has already admitted defeat. The second continues to shed light on what our minds do.

    I suspect that if we focus on the phenomenology and build up a model from observation we are more likely to understand what experience is. Instead we try to start from pre-scientific legacy concepts and their modern tropes like The Hard Problem and see if we can find evidence for them. That’s not very good science and probably won’t help in the long run.

    If we play the dualism game that there must be something we cannot see because we don’t understand it, we’re going back to superstition. The track record for science vs superstition is such that only a philosopher would continue to back superstition.

  3. 3. quen_tin says:

    Thank you for this comment on my article. As a frequent reader of your blog I am quite honoured 🙂
    I have a few comments on the different points you make (sorry, it will be a bit lengthy…)

    First a minor point. You suggest that quantum mechanics could be relevant to the Easy Problems too, and that it’s what Penrose probably has in mind. I don’t know what is Penrose’s view on Chalmers distinction, but I find it plausible that he is attempting to solve both types of problems at once, either because he does not make such a distinction or because he thinks that both are related. Anyway I have nothing against the idea that quantum mechanics could be relevant to the easy problems too.

    Then you suggest that I would be inclined to appeal to physics and to deny that biology has anything to say on metaphysical issues because I favour panphenomenalism. Ok, I admit this is a fair point. Maybe I could have let more room for alternative theories of mind in my article. Anyway for my defense, I would say that maintaining that biology has something important to say on fundamental metaphysical issues would require addressing the question of how biology relates to physics (physicalism and reductionism) and quantum mechanics could still be of interest on this question. Kim’s causal exclusion argument is an important conundrum on the topic, in that it applies to any special science whose objects “supervene” on the physical, but it relies on a view of the physical that is very classical. The point is that there is room for discussion and that there is no a priori reason for not considering quantum aspects of the physical being involved in any case, either directly or indirectly.

    You doubt that any science could ever address the hard problem of consciousness. This is a point which touches the relations between metaphysics and science. I tend to endorse some kind of “Quinean naturalism” on this. To be precise, I tend to think that metaphysical hypothesis (e.g. atomism) are indirectly tested through their fruitfulness in guiding the elaboration of empirically successful scientific theories. So perhaps a metaphysical interpretation of physics which addresses the Hard Problem could gain some credibility by opening avenues to new successful theories in the cognitive sciences? I don’t know if it’s what you meant by “reorienting our brains”?
    I agree that it sounds a bit like “banging two mysteries together in the hope that some spark will be generated” but part of my argument draws on the conceptual affinities between these two mysteries. I don’t think it is by pure chance that quantum mechanics gave rise to interpretations involving the mind: there is something about the relations between theoretical structure and phenomena in both “mysteries” that calls for an interpretation (ok this is a very vague statement but I hope it can be fleshed out somehow).

    Finally, about philosophers being reluctant to train themselves into accepting a particular worldview that might be superseded in the future, I find this attitude profundly misguided for several reasons.
    First, if this is so, why work on a wordview that is already superseded? On many respects (and Ross, Spurett and Ladyman argued on this convincingly in my opinion), the “level of generality” metaphysicians deal with has already been rudely contradicted.
    Second, quantum mechanics is almost a century old. Do we have to wait another century after a new theory comes up before to consider it seriously? And when do we decide that it is the final word? When it fits our pre-theoretical intuitions?
    Finally, the main reason for which I think this attitude is misguided is that there are strong empirical hints that any theory that will supersede quantum mechanics will share most of its weirdness. In particular, Bell’s theorem (which roughly states that no local-determinate, non-contextual property values can be assigned to a physical state prior to a measurement) is a meta-theoretical theorem largely independent from the specific formulation of quantum mechanics. All it relies on are the generic notions of space-time and measurement, and this feature of reality has been largely confirmed by experiment. Any future theory will have to accomodate it.
    Conclusions could probably be drawn from this meta-theoretical result alone (without bothering with quantum formalism), but I am not aware of any use of it in the litterature in the metaphysics of mind.
    I am eventually wondering to what extent the reluctance of philosophers to engage in quantum mechanics isn’t a reluctance to accept that our intuitions on reality are deeply challenged by contemporary physics…

    Thank you for thinking that I am an exception… Hopefully, many philosophers of science have a really good grasp of contemporary physics. Philosophy of mind is not my main area of expertise, and my aim was not to promote a specific theory of consciousness, rather to encourage philosophers to consider more seriously the potential fruitfulness of contemporary physics in their arguments.
    Having said that I have indeed a few ideas “in my back pocket”, but I’m afraid they more ressemble a combination of unconventional positions in each of the concerned topics, so I despair to convince anyone on this! (I can still post some here, or elsewhere, if you or anyone is interested)

  4. 4. Hunt says:

    Very interesting review and response. Much to think about. One question I have, and I’ve seen this statement a few times here:

    Peter said,
    “It’s about entities that have no causal properties and are ineffable…”

    What do you mean by qualia having no causal properties? I understand the “ineffable” part. This sounds like something Dennett may have said, but I don’t get it. Surely perception of the color red can be part of a causal chain?

  5. 5. Vicente says:

    Jayarava, to “believe” that ordinary science will “eventually” make it is also superstition.

  6. 6. VicP says:

    Quentin: Thank you for the thoughtful piece. I added a comment on Massimo’s blog about Scott Bakker’s Blind Brain Theory, you can do a Find for it with my last name Panzica. Essentially Scott advocates that human brains are scaled to percieve the distal environment but simply engage in the conundrums of philosophy when turned on themselves because they really don’t have a handle on the fundamental architectural complexity. I (an engineer) analogize it to kids being proficient at using their iPhones but having no real theory of microelectronic devices, computer architecture or software algorithms.

    From a Blind Brain pov, because of the highest complexity of human brains, I propose a theory of fundamental biology concerning what we share with every other animal that moves about, a fundamental sense of space and feeling in our lower brains which we build reality around. As far as quantum reality, biology is several levels up but neuron cells themselves may exhibit biological “quantum” effects by performing some type of superposition of function when they fire, essentially becoming the “same cell” which yield the qualia, emergence or a fundamental building block of conscious experience.

  7. 7. Callan S. says:

    I think qualia and such is something like various processors of external data ALSO recieving input from inside the brain (from other processors – either ones which process outside input or even some which only process internally collected input) rather than just from outside sources. And that input from other processors is treated with as much gravitas/realness as the table in front of you, because no signal is given that it is a fiction (Ie, a cross signal from other processors) and to essentially be treated with a sense of humour. All fictions that are at first taken to be real are incredibly compelling, I’m sure we’d all agree, having all gone through some example of that at some point in our lives.

  8. 8. Tom Clark says:

    Thanks as always Peter. You say:

    “To be honest, though, I doubt whether any kind of science can touch the Hard Problem. It’s about entities that have no causal properties and are ineffable: how could empirical science ever deal with that? It might well be that a scientist will eventually give us the answer, but if so it won’t be by doing science, because neither classical nor quantum physics can really touch the inexpressible.”

    The question then, is why might the inexpressible – qualia – come to exist? This problem may not be traditionally scientific in nature, since it has to do with the very nature of objectivity, but it might not be intractable if we take a broader philo-scientific approach.

    Empirical findings thus far (e.g., Dehaene, S., Changeux, J.P. Experimental and theoretical approaches to conscious processing,Neuron, 2011,70, 200-27) strongly suggest that phenomenal consciousness, the elements of which we call qualia, is a system property, not that of a system’s components. So it seems to me physics is the wrong place to look for a theory of consciousness. More fruitful, perhaps, are approaches that contrast the representational functions carried out by those brain processes associated with consciousness and those not, which is what Dehaene and Changeux do.

    Why might a representational system (RS) end up with ineffable, qualitative elements – qualia – that exist only for the system itself? Perhaps because any sufficiently complex RS by necessity needs non-decomposable (hence qualitative for the system) elements with which to do its representational work. Plus there are limits to recursive representation that will guarantee that these elements remain uninterpretable, that is, inexpressible in any more basic terms. There are other related considerations having to do with being an RS that point in more or less the same direction, see

    Why might these elements be non-causal? Since (unlike their neural correlates) they exist only for the system, they don’t appear to outside observers and so can’t play roles in third-person explanations of behavior. Hence they are barred from playing causal roles from a third-person perspective. But of course as conscious subjects we can’t help but feel they play a causal role, which sets up the problem of phenomenal causation. However, if we take the privacy of phenomenal consciousness seriously, as an ineliminable existential reality, we’ll see that consciousness can’t even be epiphenomenal,

  9. 9. Vicente says:


    just a clarification,is it that matter is a system with components, i.e. particles and fields, that have properties, i.e. mass, charge, spin… is it like this?

    For the brain, which are the components and which the properties?

  10. 10. Tom Clark says:


    Being conscious is associated with being a complex system like a brain performing various representational functions, so consciousness can be thought of as a property or characteristic of the system, a *system property*, not a property of its components. And crucially, it’s a property for the system only, not for outside observers. The system components go from the micro (ion channels, synapses, neurons) to the macro (neurally realized global workspace) and these components of course have various physical properties which are observable and quantifiable, e.g., mass, charge, etc., and various functional properties, e.g., for regulating the body, representing the body and environment, controlling behavior. But consciousness is not among those properties; it only exists for the system when it’s up and running. So it doesn’t seem to me that it’s a physical property, but rather a property of being a sufficiently ramified representational system, hence a representational property or characteristic.

  11. 11. Vicente says:


    In summary, another way to describe emergentism adding the subjective constraint.

    The only emergentism I know in physics takes place in the quantum domain, where for example, the chemical properties of a certain molecule, cannot be traced back to the chemical properties of the components (atoms). The reaction seems to add something new. Nevertheless, the new chemical properties can still be explained in terms of the electronic structure (outer orbitals)of the molecules, on the same terms, as it was done for the constituent atoms (so it is a “soft” emergent property).

    Maybe in that sense, quantum coherence is not utterly broken in the hot brain, at least for some regions, at fleeting periods, and this broad area super-structures, provides a physical substrate for your emergent new representational property, who knows.

    The point is that all these considerations shed no light at all on the hard problem analysis.

  12. 12. Vicente says:

    I meant “Tom”, sorry.

  13. 13. Tom Clark says:


    Emergent physical properties, as you point out, arise as a function of the arrangement and characteristics of the components, and are observable and quantifiable from a third person perspective. But even though we will eventually know in great detail what physical and functional correlates of consciousness are, it won’t be found to emerge from the operations of brain as an observable physical property. So I don’t think we can look to standard emergentist explanations as viable solutions to the hard problem since such explanations are restricted to what’s observable, which consciousness isn’t.

    On the other hand, being a physically instantiated representational system of the kind we are seems to somehow necessitate the existence of phenomenal, qualitative states for the system. It’s the representational logic of that necessitation that I think might bridge the explanatory gap of the hard problem. We are conditioned to want causal, mechanistic and emergentist explanations of the sort physical science traditionally traffics in, but the very notion of the physical is itself a representational designation or category that we use in modeling reality, not an a priori fact about reality in toto. So the physical, understood as a such a category, may not necessarily capture all the relations involved in a satisfactory explanation of consciousness.

    Not that I’m advocating substance dualism, only suggesting that representation might be the master concept in understanding why phenomenal states come to exist when representational systems, which we quite naturally and properly describe as purely physical from a third person perspective, engage in modeling the world.

  14. 14. Arnold Trehub says:

    Tom wrote: “Not that I’m advocating substance dualism, only suggesting that representation might be the master concept in understanding why phenomenal states come to exist when representational systems, which we quite naturally and properly describe as purely physical from a third person perspective, engage in modeling the world.”

    I agree, but the critical point re qualia is that the world must be modeled from a fixed locus of perspectival origin. This is what defines subjectivity/ consciousness. See * Space, self, and the theater of consciousness* and *Where Am I? Redux” on my website.

  15. 15. VicP says:

    Tom: “Not that I’m advocating substance dualism, only suggesting that representation might be the master concept in understanding why phenomenal states come to exist when representational systems, which we quite naturally and properly describe as purely physical from a third person perspective, engage in modeling the world.”

    The natural brilliance or natural design of nature, brains know that they are inside our heads but never question the world that appears outside and all around us. As BBT states only when brains turn on themselves do they go blind. As an engineer I have a very good handle on the natural architecture and why this happens, just look at how visual data gets distributed, like the man wearing eyeglasses in front of his eyes, on his forehead and on top of his head. Just as our folk language suggests this natural aboutness or dualism.

  16. 16. vector shift says:

    “To be honest, though, I doubt whether any kind of science can touch the Hard Problem. It’s about entities that have no causal properties and are ineffable: how could empirical science ever deal with that? It might well be that a scientist will eventually give us the answer, but if so it won’t be by doing science, because neither classical nor quantum physics can really touch the inexpressible.”

    ANY kind of science? There were arguments that temperature was beyond science since putting one hand in a bucket of cold water and the other in hot water results in the hot one feeling cold and the cold one feeling hot when both immersed in a room temperature bucket. Clearly something so subjective could not be studied objectively.

    Scientists like to invent new properties, electric charge, spin, color, lot’s of them. Just to be able to predict things. What’s going to stop them from inventing whatever they need to predict how consciousness arises and gives our various experiences?

  17. 17. Peter says:

    If that’s a child’s question, Lawrence, I think you’re mixing with some unusual children. 🙂

    Seriously, I think your simple explanation could benefit from being expressed in even simpler terms, if that’s possible.

  18. 18. De vita privata – aleksey godin says:

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