Nagel's "Mind and Cosmos"

This is my first ‘real’ blog post, and before I begin, I’d like to thank John for inviting me to contribute to this blog (and apologize for the fact that it’s taken me while to get around to doing so). Many thanks for giving me this opportunity!

I have recently published a review of Thomas Nagel’s “Mind and Cosmos” in Science (if you’re interested, it’s in Science, 339 (6125), p. 1277), and as the word limit there was very restrictive (and given how much stir the book has caused), I thought I’d take this opportunity to say a bit more about what I think about the book and, more importantly, to hear about what others here think about it.

Most of the reviews of Nagel’s book – especially those by philosophers – have been scathing. Now, as I said in my own review, I do think the book has several major flaws (more on those in a second). However, I am not sure it deserved quite the beating it received and I also don’t think it is the most interesting (let alone charitable) approach to focus solely on the negative points of a book in a review. So while I was (and remain) critical in my own approach, I also tried to bring out the positive points in the book.

Perhaps a few words on the negative points first. I think several aspects of the book are rather weak; for instance, the fact that in the chapter on ‘values’ Nagel simply assumes moral realism, without providing any argument for it. He also doesn’t do himself any favors when he combines (problematic) intuitions about the probability that consciousness and cognition could have evolved in the time span available with the philosophically rather more interesting issue of the (im-)possibility of reductionism. The former – which are regularly championed by proponents of ‘intelligent design’ (a movement which, despite his outspoken atheism, Nagel is sympathetic to, as he points out in the book) – don’t lead to strong arguments and can, I think, be rather easily dismissed (as indeed most of the reviews of his book have done). For one thing, we are notoriously bad at judging probabilities and aside from his ‘common sense’ intuition Nagel does not in fact provide any arguments for the view that the evolution of consciousness and cognition was unlikely. Moreover, even if this could be shown, it is unclear what follows from it (after all, to say that an event was unlikely to occur is not to say that it was impossible, and I don’t see why the former should lead one to reject an otherwise very strong theory, such as evolutionary theory). Further, his own sketch of an alternative, namely the introduction of teleological principles, remains unconvincing, not only because he doesn’t say much about how we are to think about these principles, but also because they don’t really seem to address what I ultimately take to be at the heart of his arguments – namely, the irreducibility of consciousness.

However, in focusing on the weaknesses, one fails to see that this main argument is actually very compelling, and that it needs a response (even if Nagel’s own response disappoints). So what is this argument? Well, it’s basically making the point that we are still lacking an understanding of the relation between the mind and brain. Consciousness doesn’t seem to be reducible to any functions fulfilled by processes in the brain (because it is conceivable that these functions could be fulfilled in the absence of any phenomenal qualities). If so, according to Nagel, not only do we have a mind-brain or mind-body problem, but we also have a problem when it comes to explaining the evolution of consciousness. This problem is very different from any considerations relating to probabilities of mutations etc. (even though, frustratingly, Nagel himself doesn’t do a very good job of keeping these two sets of problems apart). Rather, the problem consists in the fact that if consciousness necessarily remains outside the scope of the vocabulary of functionalism (or any other naturalistic theory), then it also remains outside the scope of evolutionary theory. While we might be able to explain why various cognitive functions that we take to be correlated with consciousness could have evolved, consciousness itself (due to the fact that it cannot be reduced to these functions) remains outside of the picture.

Now, none of this is particularly new or original, but given that we have recently witnessed several physicists (such as Stephen Hawking or Lawrence Krauss) argue that physics can explain everything, and given the general popularity of the view that there will ultimately be a ‘physical theory of everything’, I think Nagel is right to remind the general public (which is the target audience for this book) that there still is an ‘explanatory gap’ when it comes to consciousness, and that not everything can be explained in the terms of the physical sciences, after all.  So, as someone who is generally sympathetic to ‘explanatory gap’ type arguments, I am sympathetic to this point (even though, unlike Nagel, I wouldn’t say that it implies that materialism is false, or, as he puts it, ‘almost certainly false’. In fact, I take it to be one of the other main flaws of the book that it doesn’t consider the possibility of a ‘non-reductive materialism’.) I found it somewhat surprising that, as far as I can tell, hardly any of the other reviews focused on this issue, and that instead everyone tried very hard to dismiss Nagel’s book as thoroughly as possible. I suspect this has something to do with the worry that the book will lend support to proponents of ‘intelligent design’, but I would find it problematic if because of this worry his arguments were given less credit than they deserve (especially since he makes it very clear that he is an atheist and that he isn’t looking for or trying to support some theological solution to the problem he raises).

Anyway, I am really curious to hear what you all make of this. What are your thoughts?

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85 Comments

  1. Neil Levy

    Hi Kristina,

    It strikes me that sympathy for the explanatory gap might give you an additional ground for being critical of Nagel’s, rather than going easier on him than other reviewers. What has he achieved, either philosophically or with regard to public awareness? I don’t think he has advanced any novel argument for the explanatory gap (at least none worth taking seriously) or even clarified our understanding of existing arguments. With regard to public perceptions, on the other hand, he has contributed to an impression that the explanatory gap is somehow, perhaps nomologically, linked to opposition to materialism or evolution. The general public will conclude either that anti-physicalist arguments are a good reason to reject mainstream science or that given that such science is in good standing these arguments must be flawed, even mystical or obscurantist. So Nagel’s achievement is to increase the amount of confusion in the general public.

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  2. AnonGrad

    I think this is an important discussion, and I look forward to reading the comments. I have not yet read Nagel’s book, but I share the concern about the dismissive tone of most of the other reviews (Elliott Sober’s is a possible exception). It strikes me as very similar to the reactions that Fodor’s anti-Darwin book received a couple years ago. My guess is that both of these books are deeply flawed, but I don’t think philosophers do their cause any favor when they rush to pile on without adequate charity. I would much rather see exploration of sensible middle ground positions, like non-reductive physicalism here, as you suggest. I suspect the motivation for the harsh tone is quite the opposite, but these reviews only seem to fuel antipathy towards philosophical engagement among scientists and the public.

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  3. Kristina,

    thanks for this thoughtful post. it’s the first time i hear that Nagel argues against materialism/Darwinism from the premise that consciousness lacks a clear fitness-enhancing value. but of course, there are two possible answers to that. either the adaptational value of consciousness has yet to be univocally identified (although plenty of candidates have been proposed) or consciousness is a spandrel (or evolutionary accident). cf.
    http://philosophyofbrains.com/2012/06/28/is-consciousness-a-spandrel.aspx

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  4. > Rather, the problem consists in the fact that if consciousness necessarily remains outside the scope of the vocabulary of functionalism (or any other naturalistic theory), then it also remains outside the scope of evolutionary theory.

    You mention that the problem of consciousness is a problem for all naturalistic theories. My questions is: Why does evolutionary theory take the brunt of the criticism, as opposed to physics? Physics must be even *more* wrong than evolution if consciousness cannot be explained, since evolution must make do with whatever physics exists. If consciousness cannot be explained as a physical phenomenon, then asking the further question about its evolution is moot.

    I think this exposes a problem in Nagel’s argumentation: he cherry picks evolution as the target of criticism. It is as if he started with a contradiction and then proved evolution is wrong. Of course the conclusion followed from the contradictory premises. However, this tells us nothing about evolution, or even has anything to do with evolution.

    Instead, as the issue of consciousness looms so large, we need to examine our naturalistic philosophy of science, as you suggested, in order to make progress. Targeting evolution is capricious.

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  5. PhysicistDave

    Kristina,

    I’m a physicist (Ph.D. from Stanford, 1983); I finished reading the Nagel book a few weeks ago.

    My attitude towards the book is somewhat more negative than yours (maybe I’m just a “hanging judge”!); however, I am in nearly complete agreement with the substance of your review.

    First, there is an explanatory gap between physics and consciousness: the point has been made over many decades by physicists far more illustrious than I (Schrödinger, Roger Penrose, etc.). Physics made the (wise) choice centuries ago to focus solely on external (“primary”) qualities, and no one has ever suggested clearly how to tie our enormously successful theories based on “external” qualities to the “internal” qualities of consciousness.

    Anyone interested in modern neuroscience is painfully aware of this problem: neuroscientists just do not know what causes consciousness. I had the pleasure of chatting with a senior neuroscientist last spring at MIT who forcefully (albeit cheerfully) emphasized this to me.

    I think I may be more critical than you towards the book partly because I think this point is now old hat. Nagel himself famously elucidated the point decades ago in his classic essay “What Is It Like to Be a Bat?” More recently, Colin McGinn has made the same point in a very readable manner in his The Mysterious Flame, and David Chalmers exhaustively surveyed the matter in The Conscious Mind.

    Yes, on that point, Nagel is right, but I see nothing new and improved in this book in either substance or exposition.

    And, the rest of the book is embarrassing, for reasons you so ably explain: the credulity about Intelligent Design, the naïve approach to values realism, the failure to understand how hard it is to graft teleology onto modern science, etc.

    I must confess that, as a scientist, I tend to share the general skepticism of my colleagues towards philosophy and philosophers (although I have always enjoyed Tom Nagel’s writings, even when I disagreed with them). However, I am pleased to see that your review so accurately captures both the pluses and minuses of Nagel’s book.

    All the best,

    Dave Miller in Sacramento

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  6. It seems absurd to me to claim that there will be a physical theory of everything when it is clear that unless we are omniscient creatures we can have no concept of what *everything* entails.

    I think it takes a double standard to point to the explanatory gap in conscious studies as evidence of an intractable explanatory problem in the biology of consciousness that has somehow been conquered by the theoretical power of physical science in its own domain. Clearly, theoretical physics has its own explanatory gaps. Our understanding of the physical universe has always been provisional and gappy as evidenced by its periodic revision and extension. Science is a pragmatic enterprise, not a program for explaining the ultimate existence of anything. So even though we can’t explain the sheer existence of consciousness, I think we are making encouraging progress in explaining what consciousness is like, and how particular kinds of biophysical brain mechanisms can create our phenomenal world (consciousness).

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  7. Kristina Musholt

    Hi Neil,

    I think you make a fair point. I tend to agree with your claim that he has not advanced the discussion from a philosophical point of view. Though I must admit that I did like the way he framed the mind-body problem, namely by putting it into the context of the scientific revolution of the 17th century. I also generally admire his writing and clearly (when you consider some of the reviews written by non-philosophers) it does resonate with non-philosophers, and so might actually contribute to a public understanding of the problem of consciousness, after all. It is indeed unfortunate that some of the formulations he choses do suggest that he wants to reject mainstream science. However, I think when you read the book it actually becomes pretty clear that he doesn’t attack scientific practice per se. Rather, his book is directed against ‘scientism’, ie. the view that the natural sciences (and ultimately physics) can explain everything and are the only ‘valid’ approach to reality. Given that there are increasing calls on philosophers, social scientists and others to justify their existence, and given the prevalence of (naive) reductionist views in the mainstream media, this is a valid point to make, I believe. But I see where you’re coming from, and perhaps you are right. Certainly the book is disappointing and frustrating in several ways.

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  8. Kristina Musholt

    Hi Gualtiero,

    Regarding your two possible responses:

    a) ‘either the adaptational value of consciousness has yet to be univocally identified’

    Well, if the explanatory gap type arguments go through (ie., if consciousness cannot – in principle – be explained in terms of functional roles), then it is hard to see how we could identify an adaptational value of consciousness. It seems that at best we can identify the adaptational value of cognitive processes that also happen to be conscious. We might then want to say that it is simply a brute fact that those cognitive processes happen to be conscious, but Nagel wouldn’t be satisfied with this.

    b) ‘or consciousness is a spandrel’

    Nagel actually considers this option, but dismisses it as dissatisfactory. This has to do with the fact that he takes consciousness to be one of the most fundamental features of the world, and so he believes it cannot simply be an evolutionary accident.

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  9. Kristina Musholt

    Hi Noah,

    I think Nagel would agree with this. It’s not that he only picks on evolutionary theory (rather, like you, he sees the flaw in the underlying reductive physicalism), he just wants to point out that if we accept the fact that there is something that physics necessarily leaves out, then this something will also be left out by evolutionary theory. That said, he does put quite a bit of emphasis on evolutionary theory; presumably because it is a theory that is currently very popular (and popularized). But I think he would probably agree that ‘we need to examine our naturalistic philosophy of science’.

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  10. Kristina Musholt

    Hi Dave,

    Thanks for your kind comment! I agree that many physicists and neuroscientists are very aware of the explanatory gap. That said, I took his book to be written with those physicists and neuroscientists in mind that do tend to deny the explanatory gap, or call into question the need for philosophy.

    May I ask what exactly makes you feel skeptical towards philosophy? If you agree that there is an explanatory gap, don’t you think that’s an interesting philosophical problem? (Not to mention other areas where, I believe, we clearly need philosophy, such as moral questions.)

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  11. Kristina Musholt

    Hi Arnold,

    I don’t think by focusing on consciousness Nagel wants to imply that there is ‘an intractable explanatory problem in the biology of consciousness that
    has somehow been conquered by the theoretical power of physical science
    in its own domain’. To the contrary, I take it that he sees the problem of consciousness as a problem for all natural sciences, from physics to evolutionary biology (insofar as it implies that there will be something that these sciences will not be able to explain.)

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  12. Kristina Musholt

    Dave,

    I forgot to add, it’s interesting that you say that ‘Physics made the (wise) choice centuries ago to focus solely on external
    (“primary”) qualities, and no one has ever suggested clearly how to tie
    our enormously successful theories based on “external” qualities to the
    “internal” qualities of consciousness.’ Nagel of course seems to think that this is precisely the reason that we cannot now fit consciousness into the picture provided by physics. Once you decide to focus solely on “external qualities” (and develop your methods of inquiry accordingly), there is simply is no way to get the “internal qualities” back in.

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  13. Hi Kristina,
    I think you are right that Nagel would agree. But I find that all the more problematic. It implies he knew he was only making a media splash and not adding much of anything to the discussion. Even if the book was meant to be popular, he is writing in bad faith. He must have known that he was going to be playing right into the sympathies of people he (says he) doesn’t want to support.

    Now, like you, I am less miffed about Nagel’s book than other commentators. Also, I am all for philosophers making lots of money selling books, even if concessions have to be made (or they are just rehashing old arguments for a new audience– what I though Fodor and Piattelli-Palmarini did a few years back). What irks me is that it looks like he made the obvious, easiest money grab at the expense of evolutionary theory and biology.

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  14. Joshua Stern

    I want to second Noah’s point, that “targeting evolution is capricious”. Further, evolution does not explain or dictate particulars, it does not explain the peacock’s tail, only after the fact does it explain that it was there because it was chosen, not because it was green, or pretty, or has other properties known or unknown. Then why not consciousness, whatever it is?

    So in disdaining evolution Nagel argues only one point among many, and misunderstands it at that. Which is hardly surprising, evolution is nearly as slippery in its own right as mind. It is just a weak argument.

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  15. PhysicistDave

    Hi Kristina,

    You wrote:
    >May I ask what exactly makes you feel skeptical towards philosophy?

    Well, basically, it seems to me that the sort of problems you point out in Nagel’s book have been endemic in philosophy for at least the last couple centuries: I.e., Nagel makes statements on subjects about which science has pretty conclusive answers, but he ignores those answers. For example, I myself could write at length about the misuse of ideas from information theory by the Intelligent Design gang (I hold some patents applying information theory to computer and satellite-communication systems): Nagel was just unwilling to go to the trouble to learn what is actually known. (I hope everyone understands that I am not trying to demolish Tom Nagel: he was a pioneer in pointing out, correctly in my judgment, the explanatory gap between physics and consciousness, and, as far as I know, he is a decent fellow. It is some of his arguments in this particular book, not the man himself, that I am criticizing.)

    Second, one of the main keys to the success of science is that we are willing to definitively drive a stake through disproven hypotheses: the geocentric theory, phlogiston, the “pre-formationist” theory in embryology, etc.. All dead and gone – we would laugh at anyone who still tried to claim they are true.

    However, philosophers seem reluctant to do this: e.g., Kant claimed that our minds were structured so that they necessarily impose the categories of Euclidean geometry on the physical world. But, a few years later, non-Euclidean geometry was discovered, and we physicists now use its categories to describe physical geometry. Yet, so many philosophy texts still treat Kant’s theory as a serious theory, rather than just pointing out that it has been disproven.

    Finally, while philosophy as a discipline is too reluctant to accept that some philosophical views have simply been proven wrong, many individual philosophers are far too willing to treat questions as settled that are really still open: I have in mind, for example, Ryle’s The Concept of Mind, which, while readable enough, misses almost all the real issues concerning consciousness and claims to dissipate a mystery that is in fact really still a mystery.

    So, I object not so much to the questions that have been pursued by philosophy as to the methods that have unfortunately been far too common in philosophy.

    It does seem to me that there are some signs that younger philosophers (I’ll point to your criticisms of Nagel in your review as an example) share some of my concerns. So, an optimist might say that we are on the verge of a rebirth in philosophy, where philosophy again shows the seriousness that it showed with Aristotle or with Locke. (I’m of course not suggesting “back to Aristotle” or “back to Locke” but merely noting that both men seriously tried to engage the full breadth of knowledge of their time.)

    Dave

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  16. PhysicistDave

    Kristina,

    By the way, I hope it is clear that I am not claiming that no modern philosopher has ever written anything of value. Do you know Huw Price’s Time’s Arrow and Archimedes’ Point? My “gut feeling” is that Price may be onto something in his claim that temporally bidirectional causation may be the key to unraveling the mysteries of quantum theory. (To anyone not familiar with the literature, let me explain that of course Price and I know that causation is effectively unidirectional at the macroscopic level, with a preferred direction, presumably given by the low-entropy state of the Big Bang. However, the microscopic laws have no preferred direction, although, as now formulated, they cannot go in both directions at once. Price and I think maybe a different formulation will allow this, and, in fact, something of that sort actually occurs with “least-action” principles in classical physics.) I’d been thinking along those lines before reading Price’s book, but his book crystallized in my mind that this approach was really worth pursuing.

    So, I’ve actually tried to figure out how to implement this in an actual physical theory – no success so far. And, alas, my “gut feelings” often turn out to be wrong. Of course, if I ever succeed, Price and I both get to be famous!

    Similarly, I think that Donagan (The Theory of Morality) and Mackie (Ethics: Inventing Right and Wrong) make crucial points in ethical theory, although these points are too rarely grasped by other philosophers. And, I think Ernest Gellner was interesting in almost everything he wrote: I think he was most insightful in discussing the origins of the scientific method (e.g., Legitimation of Belief), but, even when I think he is wrong (e.g., much of his work on the rise of the modern state), I think that thinking through his arguments is almost always enlightening.

    I’ve mentioned Colin McGinn’s The Mysterious Flame; I also think his whimsical exposition of Cartesian dualism, “Consciousness and Cosmology,” published in Davies’ and Humphreys’ Consciousness: Psychological and Philosophical Essays is worth reading: I’m not completely convinced that all forms of dualism are really dead. (On the other hand, I think my views on the epistemology of logic are probably closer to Quine’s than to Colin’s.)

    And, of course, David Stove is almost always entertaining, even when he is horribly wrong.

    On the other hand, I think that most of the philosophers I just mentioned are not entirely in the mainstream of academic analytic philosophy of the last half century (vide Gellner’s Words and Things, which I take it stirred up quite a commotion among his colleagues).

    So, I think it is fair to say that I am a “skeptic” towards philosophy as it has generally been practiced in the last couple centuries: even if there are a lot of individual philosophers whom I respect, they are a tiny minority in the field.

    But times can change.

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  17. Kristina, my comments were not directly aimed at Nagel, but rather at an observation you made in your introductory post. You said:

    “Now, none of this is particularly new or original, but given that we have recently witnessed several physicists (such as Stephen Hawking or Lawrence Krauss) argue that physics can explain everything, and given the general popularity of the view that there will ultimately be a ‘physical theory of everything'[1], I think Nagel is right to remind the general public (which is the target audience for this book) that there still is an ‘explanatory gap’ *when it comes to consciousness* [emphasis mine], and that not everything can be explained in the terms of the physical sciences, after all. So, as someone who is generally sympathetic to ‘explanatory gap’ type arguments, I am sympathetic to this point [2] …

    1. My first comment argues against the notion of “a theory of everything”.

    2. This prompted my other comment because you seem to imply by your “sympathy to explanatory gap type arguments” that the problem of an explanatory gap in the natural sciences is restricted to the study of consciousness. Perhaps I misunderstood you.

    A question: Do you agree that there is something it is like to be conscious? If you do think so, what do you think consciousness is like?

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  18. Vicente

    I believe one of the causes of confusion when talking about physics, evolution and consciousness is that “to explain” and to “to describe” are used too carelessly. The problem with consciousness is that we even fail to describe it, while for physics and biology, at least, we have been able to describe the systems fairly well. But how to properly describe what cannot be measured. On the other hand, what is really explained? depends on how easy you are to satisfy.

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  19. Vicente: “The problem with consciousness is that we even fail to describe it, while for physics and biology, at least, we have been able to describe the systems fairly well.”

    Consider theoretical physics. Do we really *describe* its subatomic systems? I don’t think so because we are unable to observe these theoretical systems directly. I think it is more accurate to say that we *define* their relevant properties according to the demands of a theoretical model, and then we *describe* the *effects* of their hypothetical properties in observable experimental settings.

    If this is the case, it seems that we need to have a working definition of consciousness that is consistent with a theoretical model that can be tested in experiments or in other observable settings.

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  20. Vicente

    Arnold: Precisely, you have been working on a definition of consciousness that suits you. Thus, the resulting definition is not sufficient because it is not intended to define consciousness but to serve the support of a particular theoretical model. Now let’s try a general one.

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  21. OK, here’s my general definition of consciousness:

    *Consciousness is an experience of something somewhere in relation to one’s self*

    So a creature is conscious *if and only if* it has this kind of experience. Notice that this implies that there are also non-conscious experiences.

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  22. Kristina Musholt

    Arnold, I agree that the notion of a “theory of everything” is problematic, but then some people do talk this way.

    I also think that there are many explanatory gaps, but it does seem to me that the problem of consciousness is perhaps more fundamental than others (for reasons that have been discussed, among others, by Nagel in his 1974 paper). And the term “explanatory gap” is commonly used to refer to the problem of consciousness.

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  23. Kristina Musholt

    Noah, personally, I didn’t get the impression that Nagel was writing in bad faith or simply trying to grab money (the problems of the book notwithstanding). My sense is that he was trying to express a genuine concern about the problem of consciousness – and to remind people that despite the apparent popularity of reductionism, this problem is still very much alive. But then we can only speculate about his motivations…

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  24. Vicente

    Arnold, this is a usual point of divergence. To me, there are non-conscious mental processes (most,) but in order to call them “experience” they have to reach the conscious level. Again, language is a trap, since one could say that somebody has a lot of experience in a certain task which was gained through unconscious processes. It is better to refer to “practice”. Please note the implications of: “one’s self”. Do you mean that in order to be conscious, first you have to be self-conscious, or is it just a geometrical consideration?

    Now it is necessary to define “experience”, for which you need to use consciousness, and we end up in a tautology, as it usually happens when trying to define non reducible fundamental concepts.

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  25. Yes, common language is problematic. This is why general definitions usually need to be upgraded in a more detailed way to be scientifically useful. For my view on this see *The Cognitive Brain*, p. 301, here:

    http://people.umass.edu/trehub/thecognitivebrain/chapter16.pdf

    As you read these words, you are having preconscious experiences in your visual modality and semantic networks which do not become conscious until these pre-conscious experiences are experienced as *something somewhere* in the world around you. In my view, consciousness is a biological event that is captured in this working definition:

    *Consciousness is a transparent brain representation of the world from a privileged egocentric perspective*

    Then the scientific problem is to find the system of brain mechanisms that can generate this kind of internal representation.

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  26. Tom Sledger

    Did Stephen Hawking and Laurence Krauss say that physics can explain everything? I need a citation for this. I’ve their work and I have never encountered such a claim.

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  27. Tom Sledger

    Kristina wrote “several physicists claim that physics can explain everything”. But neither of the two posts you provided says that. In both cases, physicists say that philosophy doesn’t help cosmology. I don’t see how that can interpreted in any way to suggest that physics can explain everything. The only way to turn that into “physics can explain everything” is to assume that 1. cosmology is everything, and 2. knowledge is either physics or philosophy. I seriously doubt that’s what Hawking and Krauss meant. I read A Grand Design and A Universe from Nothing from back to back. Nowhere does either author says anything close to that.

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  28. Tom Sledger

    “Consciousness doesn’t seem to be reducible to any functions fulfilled by processes in the brain (because it is conceivable that these functions could be fulfilled in the absence of any phenomenal qualities).”

    I don’t understand this argument. It is conceivable that the function of phototransduction could be fulfilled in the absence of opsin. It does not follow that evolution cannot explain the emergence of opsin. It is also conceivable that the function of flying could be fulfilled in the absence of wings. It does not following that evolution cannot explain wings. It’s very obvious that evolution is not required to take the only conceivable path. It can take *any* path. Am I missing something?

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  29. John Schwenkler

    The argument you’ve quoted doesn’t mention evolution. And its point is not that consciousness could exist without the realization of some particular functions or material basis, but rather that any functions or material structures we might think of as the basis of consciousness could exist without consciousness.

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  30. Tom Sledger

    Let me quote the original text in full: ” Consciousness doesn’t seem to be reducible to any functions fulfilled by processes in the brain (because it is conceivable that these functions could be fulfilled in the absence of any phenomenal qualities). If so, according to Angel, not only do we have a mind-brain or mind-body problem, but we also have a problem when it comes to explaining the evolution of consciousness.”

    So, the text does says that the conceivability of zombies makes any evolutionary explanation of consciousness problematic. The argument (as I understand it) seem to be: why can’t explain how consciousness evolved, because the same function can be done without consciousness. But the same logic would then say that we can’t explain how flying evolved, since the same function (to get away from predators or even to get off the grounds) can be achieved without flying.

    You wrote “any functions or material structures we might think of as the basis of consciousness could exist without consciousness”. Replace consciousness with flying. Any functions or material structures we might think of as the basis of flying could exist without flying. That is true. But it only shows that consciousness is not unique in this regard. Every biological function is like that.

    I must be missing something. Can you point out what I am missing?

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  31. Kristina Musholt

    For example, on the Amazon page for “The Grand Design” Stephen Hawking is quoted as saying about his book:

    “It was Einstein’s dream to discover the
    grand design of the universe, a single theory that explains everything.
    However, physicists in Einstein’s day hadn’t made enough progress in
    understanding the forces of nature for that to be a realistic goal. And
    by the time I had begun writing A Brief History of Time, there
    were still several key advances that had not yet been made that would
    prevent us from fulfilling Einstein’s dream. But in recent years the
    development of M-theory, the top-down approach to cosmology, and new
    observations such as those made by satellites like NASA’s COBE and WMAP,
    have brought us closer than ever to that single theory, and to being
    able to answer those deepest of questions. And so Leonard Mlodinow and I
    set out to write a sequel to A Brief History of Time to attempt to answer the Ultimate Question of Life, the Universe and Everything. The result is The Grand Design, the product of our four-year effort.” (emphasis mine)

    This seems to me to suggest that he does think that physics (or perhaps more broadly the physical sciences) can explain everything.

    The
    general sentiment and belief in reductionism also seems to be one that
    is shared in much of the mainstream media, as well as being reflected by
    a number of comments and messages I have received from scientists in
    reaction to my review.

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  32. John Schwenkler

    Any functions or material structures we might think of as the basis of flying could exist without flying.

    That seems wrong. Could there be a creature just like a bird, in a world just like ours, that couldn’t fly?

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      • Right — and ostriches, too. But this just supports the point, which is that the only way to make sense of a bird’s not being able to fly would be due to some feature of it or its environment (e.g. insufficient air density, different physical laws). If we consider a kind of bird that *can* fly in the actual world, then it’s hard to make sense of its being unable to fly in some other world unless that world were different w/r/t some “functions or material structures we … think of as the basis of flying”. And the idea behind conceivability arguments is that consciousness is not this way: we can imagine a world just like ours in all physical respects but where the facts about consciousness are altogether different.

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  33. Kristina Musholt

    Tom: There are several different (related) arguments that try to establish the explanatory gap. One of the basic lines of reasoning is this (roughly): In order to explain macro-properties in terms of micro-properties we usually follow a two-stage model. In the first step, we provide a functional analysis of the properties we want to explain, and in the second step we show how the micro-properties fulfill the relevant functional conditions. If we are successful, no question should remain as to why the micro-properties in question produce the macro-properties in question because this is made intelligible by our two-step explanation. For example, we understand how the micro-properties of collections of H2O molecules at room temperature satisfy the conditions for the liquidity of water. However, when it comes to consciousness, many philosophers have argued that however much we learn about the brain, the link between brain states or processes and phenomenal consciousness (or qualia) will never be fully intelligible. In contrast to the water case (and presumably the case of wings), we can always ask why the brain state/process in question has the phenomenal quality it does (or, for that matter, any phenomenal quality at all).

    According to Nagel (1974), this is because of the inherent differences between the subjectivity of our conscious experience and the objectivity that is required for scientific explanation.

    Does this help?

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  34. Kristina: “For example, we understand how the micro-properties of collections of H2O molecules at room temperature satisfy the conditions for the liquidity of water [1]. However, when it comes to consciousness, many philosophers have argued that however much we learn about the brain, the link between brain states or processes and phenomenal consciousness (or qualia) will never be fully intelligible [2].

    1. In the case of H2O isn’t “liquidity” *defined* in terms of its physically satisfying conditions? If liquidity is taken as a *phenomenal” feature of H2O then the physical explanation does *not* do the explanatory job.

    2. Why should we even expect to have an intelligible link between brain states or processes and consciousness if we do not propose a meaningful definition of consciousness in terms of specified brain states?

    It seems to me that without an acceptable working definition of consciousness we will go round and round over the same conceptual path. Nagel pointed to something important when he asked what it is like to be a bat. It is too bad that he didn’t take the next step and explore the question of *what it is like to be conscious*. Though Nagel makes no reference to my proposal, this is a basic question I addressed in the retinoid theory of phenomenal consciousness. For example see these publications:

    http://people.umass.edu/trehub/YCCOG828%20copy.pdf

    http://evans-experientialism.freewebspace.com/trehub01.htm

    http://theassc.org/documents/where_am_i_redux

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  35. PhysicistDavedhmi

    Kristina,

    In Hawking’s most famous book (at least for us physicists), The Large-Scale Structure of Space-time, co-authored with George Ellis, the authors comment:

    Of course there is a contradiction [concerning logical paradoxes involving time travel in general relativity] only if one assumes a simple notion of free will; but this is not something which can be dropped lightly since the whole of our philosophy of science is based on the assumption that one is free to perform any experiment. (p.189)

    I don’t suppose this proves one way or another whether Hawking is a naïve materialist: I myself only met Steve once, and, as a lowly student, I was too nervous to ask him about this (or anything else). However, to me, this does not sound like someone who is a dogmatic reductionist.

    I can tell you that, as a physicist myself, I have always assumed that when physicists (including me) talk about a hypothetical “theory of everything,” we are talking about a theory that unifies all of the current fundamental theories, forces, and particles known to physics – i.e., a successful TOE should quantize gravity, unify the four fundamental forces, explain why we have all the different fundamental particles we do (quarks, leptons, quanta of the four force fields, and, last but not least, the Higgs), and allow us to calculate the masses and interactions of all these particles.

    I never took my fellow physicists’ reference to a TOE as going beyond that. It might be arrogant for physicists to call such a theory a “theory of everything” without worrying about consciousness, the existence (or not) of God, the issue of abstract entities, and all the rest. But, I think most of us were implicitly assuming that everyone would understand that we mean “a theory of everything physical,” that being, after all, our domain of expertise.

    After all, if we could get a theory of everything physical, we could reasonably say we had finished our job as physicists.

    Dave

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  36. PhysicistDave

    Tom,

    You wrote, “Any functions or material structures we might think of as the basis of flying could exist without flying.”

    I think part of the point here is that the connection between these material structures and the ability to fly is unavoidable given the known laws of physics. There is no explanatory gap, given our knowledge of physical laws.

    On the other hand, for the reasons that Nagel, Kristina, and I (and many other people more famous that Kristina or I) have given, given the known laws of physics the connection between the brain and consciousness is not necessary.

    Hence, the explanatory gap.

    I realize, of course, that many people want to claim that “physical” does not mean “explainable by the known laws of physics.” Perhaps not: as a scientist, I am disinclined to debate the “true” meaning of words. In any case, what we are talking about when we point to the “explanatory gap” is the gap between brain and mind given the known laws of physics.

    Some people just shrug and say they do not care about the known laws of physics. Fair enough, but then they are talking about something different than what we are choosing to talk about. Some people say that maybe future laws of physics will fill the gap. Could be – though I will tell you, as a physicist, that it is my job to try to figure out future laws of physics, and I’d bet that any that can fill the “explanatory gap” are going to be rather dramatic departures from existing physics.

    The two sides are, I fear, talking past each other simply because we are interested in different things. Our critics are basically saying to us, “Stop worrying: somehow empirical investigation will work all this out someday and you’ll be able to calm down.” And our response is, “Perhaps, but not simply by using the existing laws of physics, and it is this current explanatory gap given the currently known laws of physics that interests us.”

    We don’t want just a vague promissory note guaranteeing that someday empirical science will explain consciousness; we want to know what the existing limitation in current scientific knowledge is that prevents such an explanation today.

    Dave

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  37. PhysicistDave

    Kristina,

    I’m surprised that people do not point out the obvious analogy between the “explanatory gap” and Hume’s famous argument that you cannot derive an “ought” from an “is.”

    The analogy seems to me fairly exact: if you start with statements involving solely terms relating to external reality, at exactly which point in one’s reasoning does the first statement arise that refers to internal experience?

    I figured out the “explanatory gap” for myself as a physics student over forty years ago just by thinking in this way about the vocabulary physics uses (and does not use), long before I had heard of Nagel, et al.

    The analogy with the Humean argument would seem to me an obvious one for philosophers, and I am perplexed that it is not more widespread.

    Dave

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  38. Kristina Musholt

    Dave,

    Fair enough. I don’t doubt that most physicists understand TOE in the way you do. Nor is it my aim to prove that Hawking is a naive materialist. That said, in the paragraph preceding the one I quoted above he says this (which suggests to me that he does want to go beyond your understanding of TOE):

    “How can we understand the world in which we find ourselves? Over twenty years ago I wrote A Brief History of Time ,
    to try to explain where the universe came from, and where it is going.
    But that book left some important questions unanswered. Why is there a
    universe–why is there something rather than nothing? Why do we exist?
    Why are the laws of nature what they are? Did the universe need a
    designer and creator?”

    But be that as it may, my point was simply that reductionism seems to be quite widespread, both in the sciences and in the general public (that’s my impression at least). And I wanted to situate Nagel’s book within this context because it seems to me that the anti-reductionist points he makes are the most important ones in his book (even if they’re not particularly original). I pointed to Hawking and Krauss merely because both have recently made remarks suggesting that they consider philosophy to be “dead” (or on the way of becoming redundant).

    See also this interview with Krauss:

    http://www.guardian.co.uk/science/2012/sep/09/science-philosophy-debate-julian-baggini-lawrence-krauss

    What I take to be the important point for our discussion, though, is that both you and I seem to think that there is something to the explanatory gap, while others don’t (regardless of what exactly Hawking’s and Krauss’ positions are).

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  39. Kristina Musholt

    Btw, here is another thing I find puzzling about Nagel’s book. I have suggested that Nagel argues against the claim that the physical sciences can explain everything (by arguing for the irreducibility of consciousness, which he takes to be a fundamental aspect of reality). At the same time, he himself seems to endorse an all-encompassing view of the physical sciences – it’s just that he thinks that they probably also need to include teleological principles.

    Any thoughts?

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  40. tom sledger

    Thank you all for the comments. Maybe I am totally confused about conceivability. Chalmers wrote “Zombies are probably not naturally possible: they probably cannot exist in our world, with its laws of nature.” (I got this from wikipedia on the zombie argument). Assuming that we’ve been talking about the conceivability in the sense of what Chalmers is talking about, zombies are LOGICALLY conceivable but not PHYSICALLY conceivable. Ie. zombies are NOT conceivable given our law of physics, but are conceivable in some possible world. A recent piece by Gutting (http://opinionator.blogs.nytimes.com/2013/03/12/mary-and-the-zombies-can-science-explain-consciousness/), who I realize is not an expert on this matter, also made this point.

    Could you confirm if my understanding is correct (i.e.: Chalmers says that zombies are possible not given our physics but in some possible world). John and Dave seem to suggest that zombies are possible in our world. That is contradictory to Chalmers. Could you comment on this contradiction? Are you disagreeing with Chalmers or I am just misunderstanding Chalmers?

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  41. John Schwenkler

    I think Chalmers’s view is that zombies are conceivable (full stop) and METAPHYSICALLY possible, but — assuming the supervenience of the mental on the physical — not PHYSICALLY possible.

    However, the mere conceivability and metaphysical possibility of zombies is enough to challenge materialism about consciousness.

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  42. PhysicistDave

    Kristina,

    My impression is that Krauss is indeed a naïve reductionist (not that I have ever had a chance to talk with him directly!). I’m less sure about Hawking – Steve has sort of gone into outer space in the last few decades, thinking he can explain, e.g., the origin of the universe with the no-boundary idea (most physicists do not buy that, by the way).

    I suspect that most of my fellow physicists have never thought much about the issue one way or another: physicists (like most professionals, perhaps) are prone to a bit of tunnel vision so that most issues outside of their own narrow area just seem not to be worth that much thought. I remember in grad school when one of my fellow physics graduate students figured out the obvious transition process by which one could go from a functioning conscious organism to a Searle-Chinese-room situation (one by one replace the neurons by electronic devices, slow down the electronic devices drastically, and then replace the electronic devices one by one with humans as in the Chinese room). My friend had just never thought about the issue before, and was really shocked to discover there was a problem: he ended up switching to neuroscience!

    You wrote:

    But be that as it may, my point was simply that reductionism seems to be quite widespread, both in the sciences and in the general public (that’s my impression at least).

    I wonder. Here in the US, I am pretty sure that the median American is a naïve Cartesian dualist, partly because of the Christian religiosity of a majority of Americans. The intellectual elite seems to tend towards naïve reductionist physicalism: I suspect that this is largely in reaction to the perceived religious basis of critiques of reductionist physicalism. I’m a fairly militant critic of Christianity, but I have often been accused of being a “closet Christian” when I try to point out the explanatory gap (of course, Popper, Nagel, McGinn, Penrose, etc. are also not theists, as far as I know).

    So, it is a rather strange situation, in which various religious, cultural, and even political issues have become intertwined with what, in my opinion, should be a scientific issue: can physics as it now exists explain consciousness?

    Of course, this does mean that when I really irritate Christians, I can gain some points with them by pointing out that at least I am not a naïve materialist!

    Dave

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  43. PhysicistDave

    Kristina,

    You wrote:

    I pointed to Hawking and Krauss merely because both have recently made remarks suggesting that they consider philosophy to be “dead” (or on the way of becoming redundant).

    Yeah, and I basically agree with them, as I explained above. But, I think it needs pointing out that I, and probably Hawking and Krauss, are not criticizing Locke and Hume: my, and I think their, critiques are directed at the navel-gazing focus on the “true” meaning of words that seemed for a long time to characterize twentieth-century analytic philosophy. I don’t think they are trying to attack those among the younger philosophers who are trying to take science seriously and systematically understand its implications: in fact, as my earlier quote from Hawking and Ellis shows, Steve seems to see a continuity between philosophy in that sense and science.

    You also wrote:

    What I take to be the important point for our discussion, though, is that both you and I seem to think that there is something to the explanatory gap, while others don’t (regardless of what exactly Hawking’s and Krauss’ positions are).

    Indeed. I’m just frustrated that Nagel messed up so much of the science (e.g., in his uninformed comments on Intelligent Design) that it will be easy for scientifically literate readers to dismiss the valid points in the book because of all the errors.

    I hope it is clear that I am in fact gratified that something which has been bothering me for more than forty years is, over the last decade or two, actually becoming a subject of serious discussion. I really would like to know how consciousness works, and we are unlikely to find that out if we just wave our hands and say, “Oh, somehow it’s physics,” without realizing that there is a real problem there.

    A lot of those who deny the existence of the “explanatory gap” seem to think that pointing it out is somehow anti-science. My concern is just the opposite: I don’t see how science can solve the problem until we honestly admit it is a problem.

    Dave

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  44. PhysicistDave

    Kristina,

    You wrote:
    > Nagel argues against the claim that the physical sciences can explain everything (by arguing for the irreducibility of consciousness, which he takes to be a fundamental aspect of reality). At the same time, he himself seems to endorse an all-encompassing view of the physical sciences – it’s just that he thinks that they probably also need to include teleological principles.

    Well, it seems to me one of the big problems discussing this broad issue is that people have wildly different meanings for the word “physical”: For some people, “physical” means anything occurring in spacetime – which would seem pretty automatically to include consciousness. For others, “physical” means anything which can interact with anything which is obviously physical, which again automatically includes consciousness. And, for still others “physical” automatically includes anything that is given a functional description (which is pretty odd, since, as far as I can remember, physics never gives a functional description to anything).

    All of that is why I like to be very specific and make clear that by “physical” I mean completely explainable/reducible to the currently known laws of physics. Of course, you should really add some phrase along the lines of “and conservative extensions to currently known laws of physics.”

    The recent discovery of the mass of the Higgs particle, for example, does not change the picture concerning the explanatory gap. On the other hand, imagine we discover a new quantum field, let’s facetiously call it the “ectoplasmic field,” which occurs only around the nervous systems of higher animals. In some sense, that might still be physics, but obviously such a discovery might completely change our picture of consciousness.

    The sense in which this is not a “conservative” discovery is, of course, that most reductionists want to claim that what we already know about electrons, protons, and neutrons (and therefore atoms and molecules) is enough to explain consciousness.

    Obviously, the discovery of the “ectoplasmic field” related to nervous systems would radically change that picture. (I trust that it is clear to everyone that this is a hypothetical example, and, in fact, I’ve basically stolen the example from McGinn’s essay “Consciousness and Cosmology,” which I mentioned earlier.)

    So, again this is an instance illustrating why I think the whole subject can not really be discussed coherently without accurately referencing contemporary science, and, particularly physics, since the issue is whether physics can explain consciousness.

    Dave

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  45. Dave,

    You wrote: “In any case, what we are talking about when we point to the “explanatory gap” is the gap between brain and mind given the known laws of physics.”

    Why should we believe that the *laws of physics* can bridge the explanatory gap when the laws of physics, as such, are an invention of biology? The laws of physics did not exist until the evolved human brain created them. If we seek a physical reduction of consciousness, it seems to me that it will be a biophysical reduction in the weak sense of reduction — in the sense that the biological explanation will not violate the current laws of physics. The explanation of consciousness that I have proposed is in this spirit of reduction, as you can see from the articles that I linked in my remarks above.

    By the way, I would be very much interested in your thoughts about the parallel implications (regarding complementarity) of the double-slit experiments in physics and my SMTT experiments described in the paper “Evolution’s Gift: Subjectivity and the Phenomenal World”, referenced in my earlier comment.

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  46. Vicente

    “if you start with statements involving solely terms relating to external reality”

    Try to do that, give an statement involving solely terms relating to external reality.

    To save you time: e.g. The Earth turns around the sun.

    NO!! The Earth and the Sun are entities based on internal concepts in our minds… the don’t have an independent existence from our internal experience. Whatever the very nature of those two objects is, you’ll never know. And so on…

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  47. Kristina Musholt

    Sure, (a) is a (or *the*) big if. As I have suggested, the question as to what weight you think anti-reductionist/explanatory gap type arguments carry is precisely the crucial point here.

    As for (b), on p. 50 Nagel writes:

    “Elliot Sober once suggested to me in that spirit that consciousness might be like the redness of blood – a side effect of functional biological features that has no function itself, and no direct explanation by natural selection. In that case consciousness would be like a giant spandrel, in the sense of Gould and Lewontin (and a very lucky one for us). But clearly this bare identification of a cause would not be a satisfactory explanation. Without more, it would explain neither why particular organisms are conscious nor why conscious organisms have come to exist at all.”

    I take it that the reason that, on Nagel’s view, we should ask for more has to do with the importance Nagel ascribes to consciousness because, for example, on p. 47 he writes:

    “I am putting a great deal of weight on the idea of explanation, and the goal of intelligibility at which it aims – a goal that assumes the intelligibility of the universe, as discussed in the previous chapter. Not everything has an explanation in this sense. […] But systematic features of the natural world are not coincidences, and I do not believe that we can regard them as brute facts not requiring explanation.”

    And elsewhere again he states:

    “My guiding conviction is that mind is not just an afterthought or an accident or an add-on, but a basic aspect of nature.” (p. 16)

    Note that I am not endorsing or trying to defend Nagel’s view on this matter (I think it is entirely possible that consciousness might be a spandrel); I am merely trying to present his view.

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  48. PhysicistDave

    Arnold Trehub wrote to me:
    > If we seek a physical reduction of consciousness, it seems to me that it will be a biophysical reduction in the weak sense of reduction — in the sense that the biological explanation will not violate the current laws of physics.

    Well… how do you know that it will not violate the current laws of physics? Personally, as a physicist, I’m pretty desperate for something that will violate the current laws of physics, so that we can expand our knowledge of physics beyond its current level.

    AT also wrote:
    > The laws of physics did not exist until the evolved human brain created them.

    I’m afraid that we physicist are pretty certain that these laws described how the physical world worked long, long before there was a human brain, or any biological life at all. There is compelling evidence for this (cosmology, stellar-structure theory, etc.).

    AT also wrote:
    > By the way, I would be very much interested in your thoughts about the parallel implications (regarding complementarity) of the double-slit experiments in physics and my SMTT experiments described in the paper “Evolution’s Gift: Subjectivity and the Phenomenal World”, referenced in my earlier comment.

    Hmm… I’m afraid that Bohr’s concept of “complementarity” is just not a very significant idea in modern physics. I realize that lip-service is still paid to Bohr’s ideas in many introductory textbooks, not to mention pop-science books aimed at the general public.

    However, quantum mechanics is a very detailed, very precise area of modern physics: indeed, one application of quantum physics (quantum electrodynamics) displays the most precise agreement between scientific theory and experimental measurement in the history of science. Quantum mechanics is not at all a matter of just waving one’s hands and saying “complementarity.”

    I’m afraid that almost all attempts to “apply” quantum ideas outside of quantum mechanics in the most literal sense of quantum physics strike most physicists as simply bizarre (Deepak Chopra is, perhaps, the standard example). A more benign example is the old TV show, “Quantum Leap,” which was, at least, harmless.

    Dave.

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  49. PhysicistDave

    Vicente wrote to me:
    > NO!! The Earth and the Sun are entities based on internal concepts in our minds… the don’t have an independent existence from our internal experience.

    You are trying to defend some sort of idealism a la Berkeley?

    The problem is that if nothing exists outside of my own internal experience, then you do not exist.

    In which case, I fear, our conversation is just me talking to myself!

    Dave

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  50. Excellent post. I think you get to the crux of the problem with this:

    “Rather, the problem consists in the fact that if consciousness necessarily remains outside the scope of the vocabulary of functionalism (or any other naturalistic theory), then it also remains outside the scope of evolutionary theory.”

    I wish Nagel could have expressed it so clearly. His arguments about probability and his problematic use of moral realism cloud what I think is his most convincing point: if the very structure of our physical theory precludes a description of “internal” experience, some change to the structure of our theory will be necessary if we want a satisfying explanation. Nagel’s suggestion has to do with teleology, which, again, seems to confuse the issue more than clarify it.

    An important thing to remember is that the problems with conceptual structure and vocabulary are not limited to science. Philosophy has also failed to find a structure that can coherently integrate brain activity and conscious experience. Terms like “consciousness”, “awareness”, “mind”, “quale” and “intentionality” are still very vague when examined closely. And the language of “correlation” precludes a whole lot of possible explanations.

    I would like to see philosophers spend more time examining some of the “smaller” questions, like how a network of neurons (and supporting structures) plans and executes the task of, say, reaching out and grasping an object. In the processes of really understanding how things like this occur, I believe that we will develop philosophical concepts that will enable us to structure the bigger questions.

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  51. Dave,

    You wrote:

    “Well… how do you know that it [a biophysical reduction of consciousness] will not violate the current laws of physics? Personally, as a physicist, I’m pretty desperate for something that will violate the current laws of physics, so that we can expand our knowledge of physics beyond its current level.”

    I don’t know if it will violate the laws of physics any more than you do. I do think, however, that if a candidate explanation of consciousness were to violate the current physical canon, it would confront much more resistance from the scientific community than an equally powerful explanation that did not violate current physical theory.

    Dave: “I’m afraid that we physicist are pretty certain that these laws described how the physical world worked long, long before there was a human brain, or any biological life at all.”

    I’m sure that this is your strong intuition, and it is mine as well. But can you justify a denial that the entire conceptual edifice of modern science is a product of biology? Even the most basic and profound ideas of science, such as relativity, quantum theory, the theory of evolution, are generated and necessarily limited by the particular capacities of our human biology.

    Science is a pragmatic enterprise; its “laws” are always open to revision based on the weight of empirical evidence.

    Dave: “I’m afraid that Bohr’s concept of ‘complementarity’ is just not a very significant idea in modern physics.”

    This observation is not responsive to the question I asked you.

    Dave: “However, quantum mechanics is a very detailed, very precise area of modern physics: indeed, one application of quantum physics (quantum electrodynamics) displays the most precise agreement between scientific theory and experimental measurement in the history of science.”

    Regarding the explanatory gap, it is amusing to recall that Feynman assured his students that they would not be able to understand the predictive success of quantum electrodynamics because he himself didn’t understand it, and “nobody understands it”.

    The point that I wanted you to address, Dave, was that there is now a detailed neuronal model of consciousness that demonstrates good agreement between theory and experimental measures of conscious content. The retinoid model of consciousness has been able to predict such previously inexplicable phenomena as the appearance of a volumetric world, size constancy, the moon illusion, Julesz random-dot induction of depth, motion after-effects, etc. Most telling is the successful prediction that the structure and dynamics of the brain’s putative retinoid mechanism can induce a vivid conscious experience of an object moving in front of a subject when, in fact, there is no such object in the subject’;s visual field. Wouldn’t you say that this kind of theory and experimental test narrows the explanatory gap within the norms of science?

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  52. Asher,

    You wrote: “Philosophy has also failed to find a structure that can coherently integrate brain activity and conscious experience. Terms like “consciousness”, “awareness”, “mind”, “quale” and “intentionality” are still very vague when examined closely.”

    I agree. So I’ve proposed the following working definition of consciousness:

    *Consciousness is a transparent brain representation of the world from a privileged egocentric perspective*

    A detailed neuronal model of consciousness that is consistent with this definition has been proposed and is well supported by empirical evidence. For more about this see the links in my 4/4 comment.

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  53. PhysicistDavedhmille

    Arnold wrote to me:
    >This observation is not responsive to the question I asked you [vis a vis “the parallel implications (regarding complementarity) of the double-slit experiments in physics and my SMTT experiments…”]

    Ah, that’s what I get for trying to be polite!

    Arnold, your attempts to connect quantum theory (e.g., “the double-slit experiment in physics,” “cmplementarity,”) to your ideas on psychology seems to me utter and complete gobbledegook. That is the reaction I and most physicists have to nearly all attempts to tie in quantum mechanics to topics outside of physics.

    Perhaps we are just not open-minded enough. Frankly, though, I do not think that is the problem: we know quantum mechanics inside and out, and, when we see people pursuing very superficial attempts to show that something else is somehow really just like quantum theory… well, it just is not.

    Sorry, but if it were that easy to advance quantum theory, I’d have a Nobel prize.

    AT also wrote:
    >The point that I wanted you to address, Dave, was that there is now a detailed neuronal model of consciousness that demonstrates good agreement between theory and experimental measures of conscious content.

    Again, Arnold, sorry, but by the criteria traditionally used in physics, no, what you have does not count as “good agreement.” It is just not that easy.

    Dave

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  54. Vicente

    Dave, not at all.

    What I mean is that when you think you are referring to external objects, you are really referring to the internal concepts your mind created to handle those external objects, by “subjective” perception, and scientific inspection. But there is no way to give an statement involving “solely” terms relating to external reality. The simple fact you name those objects makes it evident. Names, language, are only in your mind. Not to mention all the other myriad of mental concepts you need to manage physical objects.

    If not, try, provide such an statement.

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  55. Dave, you wrote:

    “… we know quantum mechanics inside and out, and, when we see people pursuing very superficial attempts to show that something else is somehow really just like quantum theory… well, it just is not.”

    I certainly do *not* think that a biological theory of consciousness is “just like quantum theory”. Just the opposite! I have explicitly argued that consciousness can be explained in the terms of biology, but not in the terms of physics.

    Regarding complementarity, here is what I wrote in *Evolution’s Gift: Subjectivity and the Phenomenal World*:

    “In the development of the physical theory of light, the double-slit experiment was critical in demonstrating that light can be properly understood as both particle and wave. Similarly, I believe that a particular experiment – a variation of the seeing-more-than-is-there (SMTT) paradigm – is a critical experiment in demonstrating
    that consciousness can be properly understood as a complementary relationship between the activity of a specialized neuronal brain mechanism, having the
    neuronal structure and dynamics of the retinoid system, and our concurrent phenomenal experience.”

    As you can see, I do not claim that consciousness is a quantum effect. I refer only to the fact that consciousness has the complementary properties of both brain activation (in retinoid space) and subjective experience.

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  56. Dave,

    In a reply to Kristina, you wrote:

    “The recent discovery of the mass of the Higgs particle, for example, does not change the picture concerning the explanatory gap. On the other hand, imagine we discover a new quantum field, let’s facetiously call it the “ectoplasmic field,” which occurs only around the nervous systems of higher animals. In some sense, that might still be physics, but obviously such a discovery might completely change our picture of consciousness.”

    Why do you believe that the discovery of something like a quantum “ectoplasmic field” might change our picture of consciousness, Dave? It seems to me that this would merely be one more example of the many physical correlates of consciousness. I’ve argued that simple correlates are not informative enough to advance our understanding of consciousness. We have to look for the brain *analogs* of salient features of conscious content. Accordingly, I have proposed the following bridging principle for the scientific study of consciousness:

    *For any instance of conscious content there is a corresponding analog in the biophysical state of the brain*

    The problem then is to find those brain mechanisms that can generate the right kind of biophysical analogs. The candidate brain mechanism that I have proposed and tested is the *retinoid system*.

    Consider the apparatus for detecting the Higgs particle. As I understand it, the Forward Pixel Detector is able to give nice images of the various paths that particles take as a result of proton-to-proton collisions in the Large Hadron Collider. Well, the apparatus that I used in my SMTT experiments serves a similar purpose. It gives an overt/objective display of the subject’s covert/subjective images that my theoretical model of the brain’s retinoid system predicts should be detected using the SMTT apparatus. What are your thoughts, Dave, about this approach as a way to narrow the explanatory gap? Kristina, what are your thoughts about these findings? It seems to me that Nagel’s argument is poorly founded if he takes no account of this kind of work.

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  57. Richard Wein

    Asher wrote: “I would like to see philosophers spend more time examining some of the “smaller” questions, like how a network of neurons (and supporting structures) plans and executes the task of, say, reaching out and grasping an object.”

    That sounds like the problem of “intentionality”. Philosophers have spent quite a lot of time on that one! I would say that it’s a mistake to think of the mind reaching out and grasping an object. The mind (or brain) is just modelling the object, based on data received by the senses.

    Some of these apparent problems (like intentionality) can be deflated by thinking about computer systems. There’s no difficulty understanding how a computer or robot can build a model of reality from sense data and then act in accordance with that model. Such a robot has data about the objects in its environment. (Intentionality is often thought of as the ability of things to be “about” other things.)

    This doesn’t address the “hard problem” of consciousness. But the problem of intentionality is generally considered a separate problem. Providing they’re kept separate, the problem of intentionality is easily solved, as far as I’m concerned.

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  58. Richard Wein

    P.S. On re-reading your comment, I’m starting to think that you meant “reaching out and grasping” in a literal, physical sense, i.e. with one’s hand. If so, my reply was off the point. Sorry.

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  59. Thanks for adding that. Yes, I was talking about the literal, physical sense. It’s my suspicion that an understanding of how a neural network operates – the entire process from perception to motor activation – will give rise to new concepts and ways of talking about these issues that will prove valuable for philosophy.

    Your examples of intentionality (which in most analytic philosophy is modeled abstractly and symbolically) and computer systems (which are disctinctly un-neural-network-like) highlights, I think, how new conceptual structures are needed.

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  60. PhysicistDave

    Arnold Trehub wrote to me:
    >Why do you believe that the discovery of something like a quantum “ectoplasmic field” might change our picture of consciousness, Dave?

    Well, perhaps the new field has the property that it is always conscious. We have good reason to believe that known quantum fields — the photon field, the electron field, etc. — are not invariably conscious.

    AT also wrote:
    >We have to look for the brain *analogs* of salient features of conscious content. Accordingly, I have proposed the following bridging principle for the scientific study of consciousness:
    >*For any instance of conscious content there is a corresponding analog in the biophysical state of the brain*
    >The problem then is to find those brain mechanisms that can generate the right kind of biophysical analogs. The candidate brain mechanism that I have proposed and tested is the *retinoid system*.

    The problem is that suggestions such as yours are not really defined in purely physics terms, so you have not succeeded in reducing consciousness to purely physics terms, even if you are right.

    I know this is hard for non-physicists to understand, but try to write down the constraints on the Schrodinger equation that correspond to consciousness in your theory. If you can do that, you will be proposing a new fundamental law of physics. If you can’t, you have not really reduced it to physics.

    Either way, you have not succeeded to reducing consciousness to currently-known physics.

    Dave

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  61. PhysicistDave

    Well, you make my point for me.

    When I refer to ‘electrons,” I am actually referring to electrons. When I want to refer to my ideas of electrons, I use phrases such as “my ideas of electrons.”

    An elementary point of linguistics.

    Dave

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  62. PhysicistDave

    Well, Arnold, I find that an excellent example of gobbledegook, “word salad,” to use the more current term.

    Sorry, but your simply asserting that your theory is similar somehow to physics does not make it so: it should be easy for anyone who actually understands the physics to see this.

    I know you are greatly enraptured with this, but you did ask my opinion, and my opinion is that what you wrote is silly.

    Be careful asking someone’s opinion!

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  63. PhysicistDave,

    I previously wrote this to you:

    “I certainly do *not* think that a biological theory of consciousness is “just like quantum theory”. Just the opposite! I have explicitly argued that consciousness can be explained in the terms of biology, but *not* [emphasis added] in the terms of physics.”

    Now you, PhysicistDave, write to me:

    “The problem is that suggestions such as yours are not really defined in purely physics terms, so you have not succeeded in reducing consciousness to purely physics terms, even if you are right.

    I know this is hard for non-physicists to understand, but try to write down the constraints on the Schrodinger equation that correspond to consciousness in your theory. If you can do that, you will be proposing a new fundamental law of physics. If you can’t, you have not really reduced it to physics.

    Either way, you have not succeeded to reducing consciousness to currently-known physics.”

    What is it that you do not understand, Dave? Or have you not read what I previously wrote? I am NOT trying to reduce consciousness to physics. I am trying to explain consciousness in terms of the neuronal structure and dynamics of a particular kind of brain mechanism, the retinoid system. Many empirical findings support the validity of this theoretical model of conscious content.

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  64. PhysicistDave

    Well, Arnold, I think that if your approach were to make any sense, it would have to be because it did reduce consciousness to physics. For example, you refer to “neuronal structure and dynamics”: well, we now understand neuronal structure and dynamics in terms of physics — action potentials, the Nernst equation, and all that.

    Anyway, your and my discussion on all this started when you asked my opinion as a physicist of your alluding to certain aspects of quantum theory in what you wrote.

    I still think your allusions to quantum theory are nonsense. When I write about physics, I do not generally find it either useful or necessary to make allusions to psychology. I have noticed that people writing in areas outside of physics who somehow try to allude to quantum theory generally end up making fools of themselves.

    You would be wiser to avoid trying somehow to refer to quantum theory and instead just say directly what you have to say.

    I am neither a neuroscientist nor a psychologist and am therefore not in a position to judge your “retinoid system” idea on its merits. A bit of googling suggests that your ideas have not exactly generated enormous acceptance among researchers in those areas, and my own limited knowledge of those areas does not make me think that your ideas have much merit.

    But, perhaps that really is just my ignorance.

    At any rate, returning to the area I do know well, I would really suggest that you refrain from the allusions to quantum mechanics: it only impresses the ignorant.

    Dave

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  65. Dave,

    I’ve had many mutually informative discussions with physicists and have never encountered a response like yours. Did my suggestion that physics is an invention of the human brain trouble you? This forum is open to interdisciplinary talk about matters relevant to brains. Censorship of ideas is bad for science.

    To get back to a question I asked you earlier: Do you deny that the very universe you formalize as a physicist is your phenomenal universe — an internal representation of the reality around you?

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  66. Vicente

    Dave

    Well, here everything is anything but elementary.

    I suppose we called them electrons because they all carry a label with their personal data: name, mass, charge, spin …

    Electrons are fundamental particles defined and described by their properties and place within a model and theory, which are all mental objects. When you refer to electrons you refer to these concepts, and to nothing else. Electrons without ideas about electrons cannot be addressed.

    Whatever the physical reality behind the concept is, it cannot be handled using “SOLELY” external reality terms. Please, focus on “SOLELY”

    If not, please provide such an statement.

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  67. PhysicistDave

    Arnold wrote to me:
    >This forum is open to interdisciplinary talk about matters relevant to brains. Censorship of ideas is bad for science.

    Oh, Arnold! That is just silly! I am not trying to “censor” you. I am merely pointing out why I am certain that your attempts somehow to link your ideas to quantum physics are worthless.

    Disagreement and criticism are not censorship. Quite the contrary.

    Arnold also wrote:
    >I’ve had many mutually informative discussions with physicists and have never encountered a response like yours.

    That’s good – it is then possible that you might learn something from me that you did not learn from them.

    In truth, most physicists most of the time, when confronted with what appears to be pseudo-science, mumble something polite and avoid serious controversy.

    If you would like to show that this was not your past experience with my colleagues in physics, by all means give us a link to a reputable physicist who said something nice in public about your ideas.

    I, alas, have always lacked the sort of good sense in dealing with pseudo-scientific claptrap that most of my colleagues possess: I am appallingly frank about stating the truth in public – you have no idea what sort of trouble this has gotten me into!

    Arnold also wrote:
    >Do you deny that the very universe you formalize as a physicist is your phenomenal universe — an internal representation of the reality around you?

    I know this will pain you, but, yes, I do deny that: I honestly think I am talking about the real physical world, not my phenomenal universe.

    I am, I fear, an unrepentant sinner is oh-so-many ways!

    Dave

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  68. PhysicistDave

    Vicente wrote to me:
    >When you refer to electrons you refer to these concepts, and to nothing else.

    No, when I am referring to electrons, I am not referring to my concepts about electrons: if I were, I’d refer to “my concepts about electrons,” not to electrons.

    The earth and my concept of the earth are two different things, two very different things.

    This really is simple, and everyone, even you, knows it.

    I know perfectly well about the idealist/phenomenalist/positivist/etc. arguments to which you are implicitly appealing. But, G. E. Moore’s argument long ago for the existence of some physical objects (his two hands, as I recall) really is sufficient to refute all that nonsense: our knowledge of the existence of external physical reality is much, much more secure than any reasons to give credence to any of the arguments for the position you are defending.

    Earlier, you said:
    >The Earth and the Sun are entities based on internal concepts in our minds… the don’t have an independent existence from our internal experience.

    And, I claim the earth and the sun do have an existence independent of our experience, indeed that they existed for billions of years before there was any human experience of any sort at all.

    Either I am right and you are wrong or vice versa.

    I am content to let everyone make up her mind on that simple quote from you.

    Dave

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  69. Vicente

    We are not discussing the existence of an external reality (physical objects).
    We are discussing how we perceive and “think” about it.

    Now, make an statement about electrons, and let me proof you wrong, please.

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  70. Richard Wein

    Hi Dave and Arnold,

    Having read some of your exchange, and disagreeing to some degree with both of you, I can’t resist giving you my own third point of view.

    Dave, If I’ve understood you correctly, you seem to think that any explanation of consciousness must be in terms of fundamental physics. But why should that be so? We can explain all sorts of things without reference to fundamental physics. Historians don’t refer to fundamental physics when they explain historical events. Biologists don’t generally refer to fundamental physics when they explain the evolution or functioning of organisms. And so on. We model reality at many different levels, and we explain a particular phenomenon at the level most appropriate to that phenomenon. It needn’t necessarily be the case that the appropriate level for understanding consciousness is the level of fundamental physics.

    In saying all this, I’m certainly not subscribing to any sort of supernatural or dualistic ideas. I’m not denying that in some suitable sense everything can be reduced to physics. To use some philosophical jargon, I would say that the mental supervenes on the physical. More generally, I would say that everything above the level of physics supervenes on the level of physics.

    I’m no physicist, so correct me if I’m wrong, but I believe physicists generally don’t claim to have found an ultimately fundamental theory. I believe that physicists are referring to such a prospective theory when they talk about a “final theory” or “theory of everything”, but they haven’t found one yet. So today’s “fundamental physics” probably is not ultimately fundamental. It is still just one level of modelling among many, albeit the most fundamental we currently have. (I’m taking no position on whether an ultimately fundamental theory is possible.)

    In my view a large part of explaining consciousness must consist in dispelling conceptual confusion. A large part of the problem of consciousness, as it’s widely perceived, is the so-called “hard problem”, the question of how we can have this special type of experience which is variously called “subjective”, “private”, “phenomenal”, “qualitative”, etc. It feels as if we have something that cannot possibly be explained as the functioning of any physical structure or process. I’m inclined to agree with those philosophers (such as Wittgenstein and Dennett if I understand them correctly) who say that this feeling is illusory.

    Perhaps you have already decided this for yourself, and are simply disregarding the “hard problem”. But then I would say you are not speaking to the concerns of most people who worry about consciousness. To those people I think you must at least say that they are conceptually confused, or labouring under an illusion, and preferably give them some reason for thinking so.

    [continued…]

    1+
  71. Dave: “I am merely pointing out why I am certain that your attempts somehow to link your ideas to quantum physics are worthless.”

    How many times do I have to say that I am NOT trying to link my ideas to quantum physics before you will accept the idea that I am not trying to link my ideas to quantum physics! Roger Penrose invited me to contribute an article for a publication in which he was the principal editor. Here is a direct quote from that article:

    “Some investigators have claimed that consciousness depends on particular kinds of quantum events in the brain’s neuronal circuits. On the basis of our present understanding of quantum electrodynamics we should expect quantum events to be relevant to all biophysical processes at a fundamental level. However, I would argue that if particular kinds of quantum events are selectively determinate for conscious content, they must conform in some way to the structural and dynamic
    properties of the retinoid system.”

    Dave: “Disagreement and criticism are not censorship.”

    What would you call it when you ask me to “refrain from the allusions to quantum physics”?

    Dave: “I am appallingly frank about stating the truth in public”

    Surely you don’t really claim that someone else cannot state a “truth” opposed to your own false belief, do you?

    Dave: “I honestly think I am talking about the real physical world, not my phenomenal universe.”

    Kudos for your honesty. But I think that most who are more knowledgeable than you about such matters would say that you are clueless about the source of your own ideas.

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  72. PhysicistDave

    Arnold wrote to me:
    >How many times do I have to say that I am NOT trying to link my ideas to quantum physics before you will accept the idea that I am not trying to link my ideas to quantum physics!

    Well, Arnold, you did in fact refer to quantum theory in the article you wrote, and you chose to ask me for my opinion of what you said in that article with regard to quantum theory.

    And, since you asked my opinion, I expressed my opinion that what you said is pseudo-scientific nonsense.

    That’s all.

    For some reason, you keep attacking me for responding to your request to me for my opinion.

    Arnold also wrote:
    >What would you call it when you ask me to “refrain from the allusions to quantum physics”?

    Great Darwin, you honestly call that censorship???????

    It was a helpful suggestion aimed at helping you to avoid making a fool of yourself in public.

    I obviously do not have the power, nor do I have the desire, to enforce that suggestion on you. If you wish to make a fool of yourself in public, I certainly cannot stop you.

    Arnold also wrote:
    >But I think that most who are more knowledgeable than you about such matters would say that you are clueless about the source of your own ideas.

    Since you did not specify which of my ideas have origins about which I am clueless, I suppose we will have to leave it at that. I suppose everyone has some ideas the origin of which they are clueless about, eh?

    Dave

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  73. PhysicistDave

    Well, Vicente, what I am talking about is your claim above that:
    >>The Earth and the Sun are entities based on internal concepts in our minds… the don’t have an independent existence from our internal experience.

    If you are not willing to admit that this claim is most obviously and certainly false… well, I am quite content to leave the dispute between us hanging on that simple point.

    If you really believe that the earth and the sun have no independent existence separate from our internal experience, then your conception (or lack of conception) of reality is so alien to my own (and, I strongly suspect, to most people’s) that to argue about finer points would really be quite pointless.

    I’m really not trying to be rude here nor am I trying to play games. But, if you really believe that “The Earth and the Sun are entities based on internal concepts in our minds… the don’t have an independent existence from our internal experience,” then a debate beyond that between us would be like a debate where one person was speaking in Swahili and the other in Navajo.

    Dave

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  74. PhysicistDave

    AT wrote to me:
    >Dave, emotive outbursts aside, I take it that you believe that your experience and understanding of the real world is not produced and constrained by the properties of your brain.

    Ah, Arnold! I said nothing of the kind.

    What I have said, repeatedly, is that your reference to the double-slit experiment and complementarity in the paper you asked me to look at smacks of pseudo-science.

    Suggesting that I must hold a particular view that I did not state, simply because I criticized one aspect of your paper, also smacks of pseudo-science.

    But, I will answer your implicit question: I think that neither you nor I nor anyone else actually knows exactly how our “experience and understanding of the real world” is produced – it remains an open scientific question.

    My mentor in physics, Dick Feynman, once said:
    > “I can live with doubt and uncertainty and not knowing. I think it is much more interesting to live not knowing than to have answers that might be wrong. If we will only allow that, as we progress, we remain unsure, we will leave opportunities for alternatives. We will not become enthusiastic for the fact, the knowledge, the absolute truth of the day, but remain always uncertain… In order to make progress, one must leave the door to the unknown ajar.”

    That is one of the main differences between scientists and pseudo-scientists: pseudo-scientists are absolutely certain they know the answer to important question, even though they have no evidence for their answer and even though their” answer” appears to be merely words strung together without any clear referent in the real world.

    Dave

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  75. tetsugakunodaigakuinsei

    The new book “the neural basis of free will” by Tse/MIT has a lot to say about much of what has been said in this thread, and gives Nagel what he says he wants, a physicalist account of the NCC that requires a new view of how brain causation works. First Tse argues that physical causation in biological systems like neurons emphasizes the phase (spatiotemporal relations) among particles, unlike most systems studied by physics, which are largely understood in terms of amplitude and frequency. For example, receptors and neurons function as coincidence detectors of patterns of input. Second, he gives a new account of the neural code. Whereas people have thought that this would be a code in terms of neural spikes, he argues that it is really a code in terms of super-fast synaptic reweighting. That is, neurons don’t just make each other fire, they ‘rewire’ each other on the fly to form temporary ‘epicircuits.’ It is really interesting to think of information transfer and transformation not as spike cascades, but in terms of neurons recoding each other continually. He goes from this new view of the neural code ultimately to a new view of the neural basis of attention and qualia. I am near the end of his last chapter now, and would recommend reading it first, because in it he argues that consciousness is the domain of possible attentional operations, like tracking, and links qualia with attentional pop-out. He gives a neural account of the basis of attention in terms of what he calls ‘burst packets’ that is also an NCC. I think a couple of the middle chapters are neurosciency, but his goal is nothing less than to give a neural basis of mental causation and to link this to qualia and the NCC. He argues that the brain does not exploit any strange quantum effects like nonlocality in order to generate consciousness. However, he does argue that quantum level randomness can be amplified up to randomness at the level of spike timing, and that this is essential for the possibility of nonepiphenomenal conscious causation. He even has a section where he argues that this kind of neural code leads to the becoming real of some possible particle paths over others, because neurons set parameters in advance that collective particle paths would have to satisfy to count as informational and to make the next neuron fire. To me, this was the first plausible account of how downward mental causation might work in the brain or any physical system that I have ever come across. A lot of the book is spent drawing out the implications of this new view of the neural code, as rapid synaptic resetting. This goes way beyond Nagel harping that there is an explanatory gap by trying to fill it with a new account of the neural code, mental causation, volition, attention and the NCC. Personally, I think if Tse is right about the neural code it has really fundamental implications for the NCC specifically and the neural basis of mental events in general. There are a lot of new ideas here.

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  76. No question that changes in patterns of synaptic strength can be reasonably thought of as neuronal “rewiring”. But regardless of our theoretical intuitions, our theoretical models must be cashed out in successful tests of their empirical predictions. In the case of brain theories about consciousness, what happens in the brain has to be empirically demonstrated to be related to what happens in conscious experience.

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  77. PhysicistDave

    Whew! Richard, I think it is rare for someone to think that I said the exact opposite of what I think! Perhaps, you did not read the earlier parts of this page above my and AT’s discussion?

    The only point I was really making to Arnold, as a reply to his question directed to me, was that I think he committed a “Deepak Chopra” in his allusions to quantum theory: i.e., I think he wrote silly nonsense in alluding to quantum mechanics and that people who do not understand quantum mechanics should refrain from alluding to it.

    That’s all.

    You wrote:
    >Dave, If I’ve understood you correctly, you seem to think that any explanation of consciousness must be in terms of fundamental physics.

    Nope. Rather, the exact contrary: as I made clear earlier on this page, I agree with Chalmers, Nagel, McGinn, etc. that such an explanation is logically impossible, at least if we take “fundamental physics” to mean anything like the physics of today (of course, if we allow the phrase “fundamental physics” to be infinitely elastic, all bets are off).

    My point on that issue to Arnold was simply that his proposed explanation does seem, ultimately, to be a physical one. I very much doubt that his proposed explanation works. (This is, incidentally, a very safe bet: after all, most proposed scientific explanations turn out to be wrong, and almost all far-reaching attempts such as Arnold’s turn out to be wrong.)

    You also wrote:
    >It feels as if we have something that cannot possibly be explained as the functioning of any physical structure or process. I’m inclined to agree with those philosophers (such as Wittgenstein and Dennett if I understand them correctly) who say that this feeling is illusory.

    Well, I think Wittgenstein and Dennett are obviously and provably wrong: as I explained earlier on this page, I think there is a “Humean guillotine” – the same reasoning that shows that you cannot derive an “ought” from an “is” – that shows that you cannot derive statements relating to inner experience from statements of physics.

    I know some people want to claim that “physical structure” means something different from “structure explained by physics,” but frankly I find their claims incoherent.

    Richard also wrote:
    >Perhaps you have already decided this for yourself, and are simply disregarding the “hard problem”.

    No, again, quite the contrary: I fully agree with Chalmers on the “hard problem,” though I am skeptical of his pan-psychical solution.

    Sorry that you so radically misunderstood my position. I suppose the explanation is that Arnold and I were not directly addressing these issues in our exchange and that you did not read the earlier posts on this page by me which do address them.

    Dave

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  78. I was asked this question in a different forum:

    “So you seem to be saying that an analog, as you define it, is an event, a thought, or an image. But which is it? And just as importantly, how can it be any of them? How do we get from neurons (observable physical happenings in the brain) to an event, a thought, or an image (none of which are observable happenings in the brain) …. (PS: When I say “get from” I mean it qualitatively. How do we explain the apparent difference in nature between neurons doing their thing and events, thoughts, and images?)”

    This was my answer:

    We do not get from neurons to a thought or an image. The point that I stress is that a particular pattern of neuronal activity *constitutes* a thought or an image. So even though a thought or an image is not an observable event in the brain from the first-person/subjective perspective (from within a brain), the same thought or image can be an observable event in the brain from the third-person/objective perspective (from outside a brain). This claim seems incomprehensible to most people (an apparent difference in nature) for the very powerful reason that 1st-person descriptors and 3rd-person descriptors occupy separate descriptive domains. But there are intuitively analogous properties that can cross these two domains of understanding. This is why I proposed the principle of corresponding analogs as a guide to the scientific study of consciousness. A scientific theory of consciousness constructed within this framework will be judged on how well it is able to predict relevant empirical findings, not on whether it conforms to other common intuitions.

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