Dear JJ Vastola,

I really enjoyed reading your discussion and analysis of Laplace's Demon and quantum mechanics. You have a very creative style of exemplifying complex ideas into simple notions without losing the true essence of the concepts. Your essay raised many ideas in my head about the attempt of different mathematicians who attempt to come up with a single equation that describes the underpinnings of this universe, and in some sense, it made me think more about the P vs. NP problem as well. I know I am connecting all these things, but I am genuinely intrigued by the honesty reflected in your essay. Thank you for sharing your work.

Best,

SV

    6 days later

    Thanks for reading!

    That's a good question. Since, at the end of the day, Laplace's demon is essentially just a really high-end computer, you're probably on to something. I never thought about the parallels between reading/writing/processing memory and thinking/doing experiments, but they seem pretty striking now that you point them out.

    If there is any difference between them, it is probably only the moral difference that I'm emphasizing the demon's ability to 'think' in terms of different (possibly emergent) vocabularies. It calls to mind our own ability to do such a thing: how can we so adeptly switch between thinking about a shirt, its fabric, and the atoms that make it up? There must be a way to compute when it's appropriate to use one vocabulary or another, but it seems hopelessly difficult to pin down what that algorithm might look like in general.

    Thank you for the thoughtful comments! I'll definitely take a look at your essay.

    Judging the correctness of your theory is beyond my pay grade, I'm afraid. It looks very interesting, though.

    Thank you for the kind words, Jim. Yes, I found the imagery of the black witch moth (and some of the surrounding folklore) quite captivating as well.

    The point about our cognitive powers evolving to suit our environment is important, I think. I'm not sure what it would be like to wield a different set of cognitive powers, but I'm sure some kind of different brain architecture (or maybe even no centralized brain at all, a la jellyfish) is physically conceivable. And if it was appreciably different, maybe our ability to understand the world would be appreciably different too.

    I'll definitely take a look at your essay!

    Thank you for reading! Yes, it's fascinating to wonder about the possibility that we can describe the universe in complete detail via some equation or set of equations. What might that equation look like? Could we comprehend it? We can comprehend things like the Schrodinger equation quite well, but it remains to be seen whether it or something like it offers the full story.

    John,

    It's always good to see that someone reads your essay with some interest and with keen comments. I thinks it helps to promote the kind of analysis and thinking the foundation means to foster. Thanks, for reading and for your incisive remarks. I didn't get a chance to rate yours before, but I will now. It will be your 6th since people bomb at the time of comments.

    Jim

    Dear John,

    thank you for a very well-argued and interesting essay. No doubt one of the best I have read so far (and I have read quite some by now!). I also see a great deal of common elements between our views.

    Your variant of demon that aims at operationalizing Laplace's demon is really insightful. I see in your essay the seeds of something that I have been thinking for quite awhile (and partially already expressed in previous works), namely the "inaccessibility in principle" of certain information. I see this as an intermediate position between the ontological indeterminism (i.e. furute states are not yet determined) and the epistemic view (i.e. there is a state but we don't know it). This "inaccessibility in principle" characterizes somehow your demon and it is in fact a very useful concepts.

    I would also like to add the following comment (I think it is kind of obvious from your essay, but I don't think it is explicitely stated there). It is true as you say that a quantum Laplace's demon -due to the Schrödinger's equation- would have the advantage that small deviations of demon's description from the "true state of affairs" would not spread exponentially, contrarily to what happens in classical chaotic systems. Yet, while in classical physics there is the unspokens assumption that the there is a real state independent of measurements, in quantum physics this is no longer the case. This is to relate to the scenario that you discuss where the demon has is subjected to "the same epistemological constraints we do--i.e. that it cannot access the wave function, which is unobservable, and instead must make measurements of observable quantities to interrogate the state of the universe". So, in some sense, classical physics has in my opinion stronger metaphysical assumptions, which I have called "principle of infinite precision" (see my essay for details).

    As for the dead of Laplace's demon, you might like to have a look at my paper with Gisin (https://arxiv.org/abs/1909.03697) and references thereof, where we discuss similar arguments than yours.

    In case you have time to have a look at my essay I would be glad to receive your feedback, and discuss further how our ideas relate to each other.

    Anyway, congrats again for a great essay, top grade from my side!

    All the best,

    Flavio

      Dear John,

      Wow! What an essay.

      I would like to imagine a world where Laplace's demon could answer all questions about the future in that world. So, say the world worked like a fractal. It was generated by a simple algorithm, so it started with a single number in space and then rapidly expanded with ever more numbers added, becoming ever more complex. Say it not only generated new numbers in space but also changed the already created numbers. There would then be space full of change, a little like our own world.

      If someone asked a question about how the fractal would look in the future, the demon could then answer it by restarting the algorithm in another place and just running it at a much faster speed than the original. It would need to be assumed that the demon, its model, and the person asking the question would all need to be outside the original fractal. Also, that there was constant creation in that world, so no unitarity!

      I only mention this, as I think there is an interesting argument to say that Quantum Mechanics could be reinterpreted as a simple algorithm expanding the Universe in a fractal like way (see my essay if you are interested).

      Thanks for a beautifully written, clear and thought-provoking essay, with a very well-argued conclusion.

      All the very best,

      David

        Thank you for the very kind words, Flavio!

        I agree that information being "inaccessible in principle" is a useful concept, and that one must be mindful that determinism vs indeterminism may not be black and white. However the universe really 'is', there are ample restrictions on what we can know about it...whether it's better to describe the universe as it 'is' or in terms of what we can ever possibly know about it is an interesting question. I don't pretend to know the answer!

        Great point about classical vs quantum mechanics. I really enjoyed discussion along these lines in your essay, and never thought before about the strong metaphysical assumption that observables really 'are' determined to infinite precision in classical mechanics, though our ability to measure them is restricted. Perhaps they are not determined to infinite precision. It's hard to imagine a way to tell the difference. Still, which formulation is more useful in practice is amenable to debate/discussion, I think.

        Thanks for the paper link, I'll take a look at it.

        Dear John,

        I enjoyed a lot to read your essay. Laplace demon is hunting since a long time. I hoped your essay could help me, to get rid of him. One good thing is, that you made him physical and took him a few of his superpowers. But by submitting him to the epistemic restriction we as human have, or any physical object, that can transmit or gather information, does not chase away the metaphysical demon. In fact, how you describe the relation between, what can known and what is, is in the traditional realist fashion.

        To chase a way the metaphysical demon, one has to justify, why epistemic notions should matter at all for the understanding of our universe.

        I like how you equip your physical demon. Von Weizsäcker, who wanted to construct a time dependent formal logic, took an operational approach to formal languages and mathematics. While animals instinctively react (take action) on sensory inputs, humans can imagine the actions they take. He constructs the meaning of propositions as imagination of possible actions. This - I think - is what is described in your points 1 to 4 for the equipment for the demon.

        Von Weizsäcker's approach does, in my opinion, bridge the somehow artificial gap between the meaning of concepts of a formal language and the 'concepts of the physical world'. This because the formal concepts depend on the laws themselves. I belief this could chase out the metaphysical demon.

        How such a world without this demon could look like is described in my essay.

        Luca

          Dear John,

          I enjoyed your very readable demon essay.

          I liked the way you first introduce the demon as LaPlace did as an omnipotent being, the considered the consequences of the demon inside the Universe and then eventually 'humanised' the demon and consider what we can eventually learn given more time and analysis of future experiments.

          I also discuss the demon in my essay, albeit in a much briefer fashion, and draw some conclusions as well, before invoking Maxwell's demon as well. I hope you enjoy my angles, as much as I enjoyed yours!

          Best Regards,

          Lockie Cresswell

            Hi John!

            This was a very nice essay! I really enjoyed thinking about several aspects of Lapace's Demon, and the modified demon you talk about here. I think you're exactly on-point, even if all of our current math and physics can be programmed into such an entity, there are still tons of things that are unknowable.

            I wonder, have you thought about the limit of the size of Laplace's Demon to where it is the size of the entire universe? What is the universe itself is Laplace's Demon? Personally, I think this limit would imply the universe does indeed "know" everything about itself, and is likely a boring trivial result. But, then working backward from size, what is the demon was the universe minus one atom? How would it change things?

            Cheers!

            Alyssa

              John,

              Hope you have time to check mine out before the deadline: https://fqxi.org/community/forum/topic/3396

              Jim Hoover.

                Thanks for reading! Great question. My inclination is to believe that it would take a computer as big as the universe to effectively simulate the universe in complete detail---as you said, the universe should 'know' everything about itself! But I don't know how much power a universe-sized demon would lose for each atom you take away. You could say it loses a 'small' amount, but how do you define small here? What's the critical number of atoms or particles you have to take away in order for it to be effectively incapacitated (like a demonic ship of Theseus)? Hard to say.

                Although I didn't specify in the essay, I think in any case that it's more interesting to speculate about a demon whose size is small compared to the universe overall. Partly because it's hard to imagine such a demon doing experiments, thinking (is its ability to think hampered somehow by the finite speed of light?), and communicating with us. And partly because I was thinking about the demon as an idealization of our own struggle to understand the universe.

                Thank you for reading, and for the kind comments! That's an interesting idea. What do you mean by saying that the demon/its model/the person should be outside the original fractal? To me, it's important to imagine that all of them are a part of the universe, as we are. Given your idea about a fractal-like universe, what can a demon inside the fractal know?

                Thanks for reading! Yes, your essay was very interesting.

                Thanks for reading! Interesting, I've never heard of Von Weizsäcker (I don't know much about philosophy, to be honest). I like your essay, but I am still a bit confused about how we can know whether a given theory is semantically closed.