Hi George,

Oh yes, a universal Turing machine should be able to run *any* program since all such programs boil down to a finite set of logic functions. What I meant was, they won't all run the same programs equally well. In the case of an adiabatic quantum computer (and other quantum computers) this is at least in part a direct result of the underlying physical implementation. So it's a matter of efficiency which, while not a flat-out restriction, is still an effect produced by the underlying physics.

Ian

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  • Post #232

You start your amusing essay with the outdated thinking of Dirac: "chemistry is just an application of quantum physics." But as the Nobel laureate in physics P.W. Anderson wrote in his famous paper "More is different", published in Science, "Chemistry is not applied physics and biology is not applied chemistry."

You then present your belief that bottom-up causation is wrong and promise us that you find many examples of top-bottom causation. You write that "There is nothing new in all this: it's just that we don't usually talk about this as top-down effects."

The problem here is not only that there is nothing new, but that you only provide examples of bottom-up causation. No need to review all your examples, but I will comment on the arrow of time in cosmology and the Caldeira-Leggett model in quantum physics. As is well-known, the cosmological arrow of time can be derived by applying the usual cosmological approximations to the arrow of time at macroscopic scale. There is nothing fundamental in an approximation of the fundamental microscopic description. The same criticism about the Caldeira-Leggett model. This is a well-known approximated model which is derived from the microscopic description (check the section "microscopic derivations" of the same book that you cite). Again there is nothing fundamental in an approximation of the fundamental microscopic description.

The conclusion here is that your top-down causation hypothesis is nothing but the bottom-up causation in disguise.

    "As the Nobel laureate in physics P.W. Anderson wrote in his famous paper "More is different", published in Science, "Chemistry is not applied physics and biology is not applied chemistry." Well yes, that's reference [16] in my essay. Guess you failed to notice I'd referred to it.

    "You then present your belief that bottom-up causation is wrong". Incorrect. I did not say its wrong, just that it's not the whole story. Of course it occurs.

    "You only provide examples of bottom-up causation". Incorrect. You choose to ignore all but two of the examples I give.

    "The cosmological arrow of time can be derived by applying the usual cosmological approximations to the arrow of time at macroscopic scale. There is nothing fundamental in an approximation of the fundamental microscopic description." Actually the causation is the other way round. It's the *macroscopic* arrow of time that derives from conditions at the cosmological scale. At the microscopic scale that there is no preferred arrow of time, and approximating those interactions at the micro scale won't give you an arrow of time when there is none there to begin with. You have to get it from large scale properties of the distribution of matter in the distant past.

    "The Caldeira-Leggett model.. is a well-known approximated model which is derived from the microscopic description." Well yes of course it's well known: I referred to it by name, with references. The question is how introduction of the "counter term" is justified. One of the standard physics texts phrases it "this term is added in for convenience". But you can't just add in a term for convenience: you have to derive it from the interactions in the problem. All the bottom up interactions are already covered by the other three terms in the Lagrangian. You have to add it in to account for the affects that are *not* derivable in a bottom up way from those interactions alone.

    "The conclusion here is that your top-down causation hypothesis is nothing but the bottom-up causation in disguise." Well I choose to side with Nobel prize winner Bob Laughlin's analysis (reference [12]) rather than yours.

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    • Post #234

    The O.P. didn't read the same essay as I. I saw a complex system model in which top down causation is linked to laterally distributed causality. Self organized order with feedback.

    Tom

    Hi Tom

    Agreed. It's a world away from the way fundamental physicists usually think, because they are unfamiliar with all that literature and with that way of thinking, so they find it difficult to relate to this viewpoint. The problem is that their restricted view, which excludes these effects, is supposed by them to encapsulate all forms of causation that occur in the real world. Not true.

    Condensed matter physicists such as Anderson and Laughlin understand the crucial causal connections, which is why they take a broader view than this anonymous commentator (and win Nobel prizes in consequence). But their ideas are crucial to fundamental physics too: vide the key role Anderson's ideas on broken symmetries played in the development of the Higgs mechanism.

    George

    Sure I agree on that. Efficiency is determined by both the underlying physics, and how it is deployed (design issues enter here); possibility is not.

    George

    George, I hope you find time to get involved with one of the several institutes devoted to complex system research, such as NECSI or SFI. I think you'd find the highly interdisciplinary climate very comfortable.

    Tom

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    • Post #238

    I introduced the quote from the Science paper, because this important quote cannot be found in your essay.

    You have truncated part of what I wrote and then missed my point. *All* the examples that you believe show that bottom-up causation "is wrong" are compatible with ordinary bottom-up causation and invalidate your hypothesis.

    The macroscopic arrow of time can be obtained from the microscopic description. The cosmological description is a coarse-grained approximation to the microscopic description. This is all well-known and explained in many excellent textbooks although ignored by some cosmologists.

    The "counter term" in the Caldeira-Leggett model is an ordinary renormalization term. In the same textbook that you use as reference, the Caldeira-Leggett model is introduced in the section on quantum Brownian motion. As everyone knows quantum Brownian motion is compatible with ordinary bottom-up causation. You would also check the section "microscopic derivations" of the cited textbook before continuing posting such incorrect thoughts.

    "I introduced the quote from the Science paper, because this important quote cannot be found in your essay." There are numerous important quotes I could not include because of the length limits on the essay. I have no obligation to include any particular one that you prefer.

    "*All* the examples that you believe show that bottom-up causation "is wrong" are compatible with ordinary bottom-up causation and invalidate your hypothesis." I deny this claim of yours. In particular it does not apply for example to the way that abstract algorithms control computerised robots. There is no way you can derive those algorithms from the underlying physics in a bottom up way. The relevant variables are not coarse grained versions of lower level variables, or derivable from them in any other way. It also does not apply to the physiology of the heart, as explained by Denis Noble in his writings on physiology, or to epigenetics, as explained by Gilbert and Epel.

    "The macroscopic arrow of time can be obtained from the microscopic description. The cosmological description is a coarse-grained approximation to the microscopic description. This is all well-known and explained in many excellent textbooks although ignored by some cosmologists." Of course the cosmological description is a coarse grained approximation to the microscopic description; see my GR10 lectures from 1984 for a clear description of how this works. This feature is incapable of explaining the arrow of time, as there is no arrow of time in the micro level physical laws. This was known already to Loschmidt and Boltzmann (the key point is that Boltzmann's derivation of the H-theorem works equally well for both directions of time). It is for this reason that authors such as Roger Penrose and Sean Carroll relate the arrow of time to a global low entropy state in the early universe. That is a macro state that has to be described at a macro level of description.

    "The "counter term" in the Caldeira-Leggett model is an ordinary renormalization term. In the same textbook that you use as reference, the Caldeira-Leggett model is introduced in the section on quantum Brownian motion. As everyone knows quantum Brownian motion is compatible with ordinary bottom-up causation." I will reconsider this when I have the chance, the issue being whether renormalisation can be regarded as representing a purely bottom up effect or not. It is conceivable this review could lead me to change my opinion in this particular case. But your claims of a purely bottom up explanation won't work for example in the case of superfluidity, as is carefully explained by Robert Laughlin in his Nobel lecture.

    Dear George, you agrue that causation is top down with those who argue it is bottom up. But even with feedback loops, either way, it is still a linear, one-dimensional view on things. Have you considered that it may be neither? (I know from your essay that you considered it could be both).

    What if causation is a multidimentional, convoluted, worse yet, fractal thingie that defies all methodologies trying to trace it with a finger like a crack on the wall?

    It so happens that all things in life and in physics are interconnected; nothing is ever a single, naked point in spacetime. Everything has many different causes, large and small, near and far, that converge into making that particular thing manifest. And it, in turn, also causes so many other things manifest, large and small, near and far -- after colliding, merging and parting ways with so many other things and causes, large and small, near and far..

    Ah?

      I have sympathy with this view: "What if causation is a multidimentional, convoluted, worse yet, fractal thingie that defies all methodologies trying to trace it with a finger like a crack on the wall?" Yes the web of interactions in the real world is very complex. But it's not fractal: there seems always to be a lower level where in small enough domains the essential causal interactions are linear. Their outcome depends on context, but nevertheless we can understand the elements of causation by looking at such small local systems.

      It is when you put them together to get really complex interaction networks that things get really complex: but even then there are identifiable hierarchical structures and network motifs that let us understand much of what is going on. It is in this context that we can reliably identify both bottom up and top down elements of causation.

      So I am not as pessimistic as you.

      George Ellis

      lol good for you, George!

      But I seriously think that information is fractal (and information is related to causation). I base it on my observation of the real world, when I was trying to understand some strange phenomena. To me it appeared that an event had many consequences, large and small, near and far, just as I said above. And I saw those consequences (I am a visual type) as paisleys of various sizes making up a flowery pattern on a fabric. And the interesting thing I saw was this: before an event arrives (a big paisley), there are many small paisleys (and of course a few medium size ones) that arrive before it, in a way, announcing the arrival of the main event. They do it many times, at various times. And they run in streaks, like it befits a fractal thing proper. Likewise, after the main event, there are many "aftershocks", large and small, running in streaks. Then a streak changes as if madam info got tired of her tune.

      I hope I made sense. This view of events as paisleys on repeated patterns, large and small, made me think that info is indeed fractal. And information, you must admit, is related to causation.

      Also, when we think of causation, we tend to oversimplify and consider real only the obvious things, like, 'heating up water causes it to boil'. Usually, what's left out are things like, why exactly did mom put the kettle on the stove. Was it because she wanted some tea? Or because she expected a company? Maybe a habit; she always does it around that time. Even when a person thinks that he or she had a clear, well defined intent, in reality it is virtually impossible to trace the "intended action" to something concrete. As long as an action appears reasonable in a given context, one can always find a reasonable explanation. The trouble is, reasonable explanations are rarely right. Worse yet, they rob us of our illusion of free will.

      I find the first part of your response a bit mysterious: it may be to do with the mind rather than physics.

      I very much like the second part about the kettle: it raises the real deep issues. The thing that's puzzling is how these deep questions relate to physics: how can we take the physics seriously, not underestimating it in any way, but not also not trivialising the deep issues? -- in particular, not trivialising life, consciousness, and the issue of free will. That's the real challenge that underlies this whole discussion.

      You may have missed the post in this thread by J. C. N. Smith on Jul. 20. It's worth reading.

      George Ellis

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      • Post #244

      GE:

      Yours was an interesting and informative essay.. As a newcomer to the FQXi community, I feel few of the "community" grade, or even look at, my essay which approaches the problem very realistically, based on an internal view.. Might you look at it, comment if so inclined, and grade it?

      To Seek Unknown Shores

      聽聽 http://fqxi.org/community/forum/topic/1409

      Thank you

      TE

        Yes, thank you, that was a very good reading.

        About my mysterious response, I was just in a playful mood last night which continued into this morning (hope you don't mind). What I find mysterious is that I made both posts above _before_ I followed your lead and read "Patterns in the Fabric of Nature" by Steven Weinstein, which brings up the complexity of non-locality of causation and the question of free will. Coincidence?

        It is tempting to see my largely unconscious actions (2 posts above) as precursors to the event about to unfold (reading Steve's essay), as if the arrow of time can be reversed. Since I do not believe in the reversal of the arrow of time, I see this sort of coincidences as the proof of the fractal nature of information (and causality), which I tried to convey above. How else can this be explained?

        George Ellis,

        Your essay is empty - no wonder it gets top community rating. It is tautological - you just define as "top-down causation" influences that go from what you see (or mankind has defined) as higher hierachical level to what you see (or mankind has defined) as lower hierachical level.

        Pentcho Valev pvalev@yahoo.com

          Dear George Ellis,

          As a relativist who has written about the structure of spacetime, how do you get causality out of block time? You don't mention block time in your essay, but it would seem from your bio that you think Minkowski spacetime is right, and that leads unavoidably to block time.

          I've argued in my essay that if block time is right, and motion through time is an illusion, then the laws of physics, and crucial principles such as cause and effect, would have to exist within the illusion, because they require motion through time.

          I've also argued that the two levels of time we seem to find, block time and motion through time, can't possibly co-exist as simply part of the nature of the time dimension, as many assume. Given the intrinsic unpredicability of quantum events, the two levels disagree over whether the future already exists. This means only one of these levels can be real - I've examined both possibilities.

          Block time is one of these two possibilities. But it implies that you can't assume the spacetime interpretation of SR is right, and also have causality. This is one of many problems with block time that people often ignore. Because the time dimension is taken to be different from the other dimensions in Minkowski spacetime, people sometimes assume that the nature of the dimension somehow solves the problem. I've tried to show that this can't be the case. Do you have a way to get causality out of block time?

          Best wishes,

          Jonathan Kerr

            Dear Jonathan Kerr,

            that is not the topic of this essay or thread. However I have just put an extensive paper on the archive [ink:http://xxx.lanl.gov/abs/1208.2611]

            Space time and the passage of time [/link] looking at the issue in detail. In brief: there is no problem if one has an Emerging Block Universes (EBU).

            George Ellis

            Dear Pentcho Valev

            Your comments would carry much more weight if you chose to omit the insults and sarcasm.

            You claim "It is tautological - you just define as "top-down causation" influences that go from what you see (or mankind has defined) as higher hierarchical level to what you see (or mankind has defined) as lower hierarchical level".

            There is indeed an issue here: how does one define higher and lower levels? That has to be done depending on context: it is quite different in the physical sciences, the life sciences, and artificial sciences. It can be sensibly done, as is shown in various articles referred to in my essay (indeed one cannot understand complex systems without categorising such levels: see for example Tannenbaum's book on digital computers for that particular case).

            Given that context, this is a sound definition. The scientific issue is whether there are instances of existence of such effects. My claim is that there are indeed many examples showing this is the case, across the sciences. There is much evidence to support this claim.

            George Ellis