Metaphysics as science fiction


Recently I’ve found reason to read up on several metaphysical theories floating around among physicists and philosophers – the Holographic Universe theory, the Mathematical Universe theory, the Simulation Reality theory, the Computational Universe theory, the Multiverse theory. Some of these theories seem useful in supporting other theories – the Multiverse theory can be used to support string theory for instance. Some complement each other; some effectively negate each other. All of these theories have the following properties in common:

1. Each is presented as a largely complete metaphysics. If you want to know what this means, one can read the pre-modern science texts of Aristotle plus his Metaphysics; or better yet, Aquinas’ Summa Theologia. A complete metaphysics will tell you absolutely everything you need to know about everything. The last nearly successful attempt to achieve this was Hegel in his Phenomenology of Mind and the (so-called Greater) Science of Logic taken together. ‘Nearly successful’ idiosyncratically enough, for the same reason that it is not successful – Hegel has metaphysics spin inward as a question of what the human mind can know and how it knows it, rather than what the universe is and how best to describe it. That is the Modern turn in philosophy (beginning with Descartes), becoming primarily concerned with epistemology, and leaving questions concerning the actual data of nature to the natural sciences.

2. Now, however, we have some scientists and philosophers who think they can beat this wrap. The access to the deeper truths of reality, they assert, can be found in or via mathematics, as they can be elaborated functionally by computers and the simulations they generate. (It is notable in this context that none of their metaphysical theories seem to me to be epistemologically sophisticated, but we’ll consider their weaknesses later.) Thus each of these metaphysics is either elaborated mathematically or supported by appeals to mathematical principles, or to principles in the computer sciences, especially as applied to sub-atomic physics.

3. Each of these metaphysics is so dependent on mathematics, that empirical evidence for their claims is implicitly held irrelevant or at best tangential.

4. With the possible exception of the Multiverse theory, which has variations strongly physical in nature, each of these metaphysics denies, or at least undermines, belief in the reality of the physical universe, and indicate that the world of our senses is essentially illusory.

Let’s consider their basic claims one at a time (borrowing from Wikipedia):

The Holographic Universe: “In a larger sense, the theory suggests that the entire universe can be seen as a two-dimensional information structure ‘painted’ on the cosmological horizon[clarification needed], such that the three dimensions we observe are an effective description only at macroscopic scales and at low energies.”

The Mathematical Universe: “Our external physical reality is a mathematical structure. That is, the physical universe is mathematics in a well-defined sense, and ‘in those [worlds] complex enough to contain self-aware substructures [they] will subjectively perceive themselves as existing in a physically ‘real’ world'” (the direct quotations are from theory advocate Max Tegmark).

The Simulation Reality: “Simulated reality is the hypothesis that reality could be simulated—for example by computer simulation—to a degree indistinguishable from “true” reality. It could contain conscious minds which may or may not be fully aware that they are living inside a simulation.

The Computational Universe: “Pancomputationalism (also known as pan-computationalism, naturalist computationalism) is a view that the universe is a huge computational machine, or rather a network of computational processes which, following fundamental physical laws, computes (dynamically develops) its own next state from the current one.”

The Multiverse: “The multiverse (or meta-universe) is the hypothetical set of infinite or finite possible universes (including the Universe we consistently experience) that together comprise everything that exists: the entirety of space, time, matter, and energy as well as the physical laws and constants that describe them. The various universes within the multiverse are sometimes called parallel universes or “alternate universes”. (Many variants.)

We’re going to set aside the Multiverse theory because of its many variations. (The one I initially had in mind was Tegmark’s, developed to support his version of the Mathematical Universe; that is, the Multiverse unfolds into differing universes in which a certain sets of mathematical structures realize themselves as the reality of their given universe. He also has his own variation of the Computational Universe as well, apparently.)

I’m not going to go into the details of these metaphysics. I admit I don’t have the mathematics or even the physics to approach them on their own grounds, so to speak. But I will give a brief report, as a layman, on the problems I’ve found in the cursory reading I’ve been able to give them. So think of this as the first remark of an interested outsider.

The first impression I get from all of these metaphysics, is that there’s a deep streak in the human consciousness of denial of reality. I find it extraordinary that clearly highly intelligent men and woman can indulge in what are clearly mystical speculations, simply because there are mathematical formulas that can be plugged into them. I’m reminded of the Kabbalists of the Jewish tradition, or the sacred word cultists of the Hindu tradition – find the magic number or the secret word, and god will reveal all.

What is it?  the stench of being human?  the crude tactile being of an animal that hungers?  the many mistakes of a contingent consciousness?   Why don’t they want to be human, just as given, just as we find ourselves?  Will mathematics provide them with redemption?  Nothing provides us with redemption; there is no redemption.  There is this life we live – there is nothing else.
Secondly, this primacy of mathematics and computer simulations is putting the cart before the horse – or rather, it is saying that because there is a cart, the horse must be unreal *. These metaphysicians seem either to ignore the fact that mathematics and computers are invented by humans as tools for their use, or they think that the very fact of the invention indicates some greater truth about reality. Imagine when perspective was fine-tuned in painting during the Renaissance, some clever metaphysician, looking for the first time at a painting using the new technique, cried ‘Eureka! Don’t you see, that’s clear evidence that we are merely layers of paint on the firmament!’ That seems to me the same kind of reasoning that goes into theories that ‘the universe is holographic, because, well, there’s holography! we function like simulations because there are simulations that function like us!’

This is something like the ontological argument of the old theology – if it can be thought, it must exist, and the most perfect of what can be thought must exist as perfection itself. (The mathematical/ simulation/ holographic universe is clearly more perfect than the one we have now. E.g., shit is not really shit – smelly nitrogenous waste from a biological digestive system of an aging animal doomed to die – it is really an eternally running computation of a perfected mathematical formula – it is illusion to see it otherwise.)

Third, like the strong suggestion of an ontological argument afoot, one sees strong hints of pre-modern argumentative forms, as well as some strangely attenuated modern argument forms. One sees (in at least the popular presentations of these metaphysics) reasoning by analogy. This was a common Medieval practice that has largely been abandoned, or used metaphorically. Reasoning by analogy is very tricky, since it assumes that structures of one kind of entity can be deduced from the known structures of another kind; the ontologies of the entities compared need to be pretty much same, and this has to be argued convincingly first. The reasoning follows thus: as one entity appears to function as another, the structures of the two entities must be similar or even the same; in the same measure, if the structures of two entities are similar, their function must be similar. Thus to say that because measurement of universe can be computationally simulated, that there fore the universe must be computational, is really reasoning by analogy – as the computer functions so must the universe.

The loose use of more modern argument styles is rather troubling. Nick Bostrom, advocate of the Simulation Reality, structures many of his arguments in a probabilistic fashion: the probability of X being likely, the probability of Y dependent on X, the probability of Y approaches being true. The implication of what this really means, logically, is revealed in a sentence like: “Now, if these assumptions are made, what follows (…)” ( – In other words, the argument really only leads to an assumption, upon which we are to accept the proposal. This is sloppy argumentation.

Speaking about sloppy argumentation, it should be noted that although these metaphysics effectively undermine the notion that reality is fundamentally physical, they lapse continually into claims on the physical – sub-atomic physics proves this, physical laws indicate that – how can the physical possibly be hi-jacked to disprove its own physicality?

Fourthly, the clear move to reduce the reliance in scientific research on empirical evidence is frankly alarming. Many of us depend on the ability of science to provide us an empirically testable reality that can produce, not just reasoning and argument, but actual facts about ourselves and the world we live in. If science is reduced to mathematics, then scientists are reduced to preachers explaining doctrine that we will have to take on faith. Then the charge of anti-science factions, e.g., religious fundamentalists, that science is merely another religion itself, will receive validation from within science itself.

It is not surprising that occasionally some philosopher can come up with crackpot theories about alternative realities in which we are all illusions without bodies. Philosophy has long had history of some thinkers getting carried away with the sheer brilliance of the reasoning process, off into fantasy lands constructed out of mere words. There’s always a danger, in attempting to reason through the deepest questions of human existence, to think that one has found the ultimate truth of it all, especially if one has a strongly systematized logical structure. The structure seems to organize reality so well, some become convinced that the structure of the logic is the structure of reality.

But logic, philosophy, mathematics, the sciences, are merely descriptions of what we can know of reality. Although any one science only investigates, describes, and explains a particular part of the whole picture, there is no one science that can give the whole picture (such an effort is what we expect from philosophy) – nonetheless, we have long depended on the sciences to provide reliable descriptions of what they do investigate, that are coherent with some human experience of reality. If the sciences are allowed to go into metaphysical speculation without empirical grounding, then reality is irrelevant. The most extreme post-modern claim – there is no single ‘reality,’ only strong narratives that we attach to for ideological reasons – becomes the default epistemic position.

I know that the mathematical/computational metaphysicians are not aware they are helping to construct such a trap to walk into – they are convinced that mathematics – since, within its own logical domain, it is very trustworthy – can vouchsafe the reliability of their logical claims; that is, the math being reliable, the metaphysics built upon it must be reliable. This is simply wrong. Epistemologically, mathematics have their own domain. They reside in the human mind. They can be used to measure reality; they cannot replace reality.

Reality is just this messy stuff we keep belching out when we eat certain foods. It is the stuff we bump into when we’re not looking. It’s that big thing floating above the earth at night. It is the machine we build and the clothing we wear. It is the desire that urges us, the frustration we feel when desires go unmet. It is the shit that stinks.

A metaphysics that cannot account for my bowel movement is effectively worthless. Intriguing, perhaps, and entertaining. But most science fiction is.  But I will not allow it to establish the new religion of a trans-humanist, post-humanist, or otherwise anti-humanist religion.  I haven’t freed myself from the hypnotism of religion to buy into mathematical mysticism.  This earth is filled with problems, corruptions, and imperfections of  unnumbered variety.  But it is the only earth I have, for the short amount of time allotted me.  And it is the only reality in which I have any interest.

We are unredeemed.  There is nothing to be redeemed.  There is no hope and no future.  There is only ‘come as you are, leave and farewell.’   That’s what it means to be human.  Live with it.


*  Obviously these metaphysicians never read Nagarjuna, who, some 2000 years ago, demonstrated that the cart could not exist as anything more than an (empty) concept, being necessarily an aggregate.  I allow that one can disagree with Nagarjuna, but clearly his argument is considerably more sophisticated epistemologically than those such metaphysicians produce.  For that matter, the arguments of Occam, of the famous razor, whose rule they continually violate, are as well.


9 thoughts on “Metaphysics as science fiction

  1. Disagreeable Me sent a response to a comment I made to an article on this topic to my “About” page; that page was not the place for it, so I reproduce it (in its entirety) here:

    “Disagreeable Me (@Disagreeable_I)
    11 hours
    Hi ejwinner,

    Ran out of comments on Scientia Salon, but I wanted to say I think you got Bostrom badly wrong. You can delete this comment after you read if if you like. This isn’t really the place for it but didn’t know how else to reach you.

    > His main projects are that we should devote our technologies to hastening post-human evolution

    Not true. His main project at the moment is in fact to warn of the dangers posed by artificial intelligence, and his funding is for research to help design programs that will help to avert catastrophe by developing strategies to ensure that any AI we develop will be benevolent.

    And if you look at the very link you posted in support of your argument, the paper concludes not that we need to rush to spread throughout the galaxy but that we must make sure we survive long enough to do so (if this is even a remote possibility). If anything he is an opponent of over-hasty development. His interest is in exploring the consequences of technological development and doing work to make sure we’re ready for it.

    > Creative speculation can be done in an armchair

    Bostrom is not just doing speculation. He is working with scientists to help develop research programs and strategies to avoid the kind of risks associated with developing disruptive new technologies.

    The simulation argument has no bearing on any of this. It is pure philosophy, has no political goal and is not connected in any way with the work he is getting all this funding for.”

    My response:

    On re-reading the Bostrom essay I linked, I admit I read it too fast, nonetheless, an essay that concludes its opening section “Even with the most conservative estimate, assuming a biological implementation of all persons, the potential for one hundred trillion potential human beings is lost for every second of postponement of colonization of our supercluster” and finally argues “This should lead her to emphasize speed of technological development, since the rapid arrival advanced technology would surely be needed to help current people stay alive until the fruits of colonization could be harvested,” frankly has a political agenda much as I pointed out, and cannot do otherwise. That the simulation hypothesis does not depend upon any one advocates political agenda, I do not deny. Still the discussion concerning the allocation of resources (and the critical analysis this necessitates) remains valid.”



    • I realized that to be fair, I needed to include my comment to which Disagreeable Me was replying:
      “Nick Bostrom, a major simulation hypothesis proponent, has been pushing a political agenda (see for instance, His main projects are that we should devote our technologies to hastening post-human evolution (that is, mastering the simulation with supercomputers, if I understand correctly) and trans-galactic interplanetary colonization (because otherwise, the human race is doomed, apparently).

      Although he doesn’t discuss what resources we would need to draw upon to achieve any of this, let me ask, how many billions of dollars are you willing to take away from charity and from social welfare programs in order to give Bostrom support in this venture?

      Fortunately, most politicians will not be terribly impressed with such arguments. But they may be interested in whether such research can develop improved technological means of surveillance, increased social control, or more destructive weaponry. At any rate, Bostrom has managed to convinced someone somewhere that his speculations are worth hundreds of thousands of dollars, as he directs two research projects, one at Oxford University, and the other the independent Future of Humanity Institute.

      Creative speculation can be done in an armchair, and beyond the funding of employment (which would likely not be awarded for the speculation alone), there is little more at stake when academics engage in such speculation. But the game changes when large grants and donations, and possible government funding, become involved. “


  2. Hello ejwinner,

    Thanks for the post,

    I agree with the general thrust of your argument, but would question the necessity of the bleak framing employed in your concluding paragraph. While our present and future realities will always include uncertainties, discomforts and disappointments we ourselves play an important role in the way we interpret our present ‘realities’ and influence the future realities of ourselves and others. I think we can find fulfillment in this world, and influence at least a temporarily more hopeful future without resorting to mystical fantasy.


    • Yes, well, I agree. I suppose I closed so bleakly because much of these kind of metaphysics imply a kind of immortality – or certainly the wish for immortality. While the new technologies certainly are increasing life-spans, when I hear anything that seems to promise immortality, I just want to say, ‘no, probably not, not in this lifetime.’ immortality


  3. Hi Ejwinner,

    Just realised you answered me here. Will also comment on your article.

    I think where we differ on Bostrom’s arguments is that you think he is producing political rhetoric and I think he is pointing out the surprising conclusions that follow from pretty reasonable seeming assumptions. To me, his paper on waste and the simulation argument seem to be motivated by genuine intellectual curiosity. It’s philosophy for the sake of philosophy as far as I can see.

    What he actually cares about these days is the existential risks posed by technology, and particularly AI. Of course he’s not alone in that, Stephen Hawking also recently raising concerns. The risk posed by rogue AI is perhaps very very small, perhaps only a 0.1% chance that it will take over the world in the next 200 years. But that risk is still large enough to warrant spending some money doing research to investigate and hopefully prevent that problem. A few million is not a lot of money out of the global economy.


    • Well, there’s nothing wrong with intellectual curiosity, and there’s actually nothing wrong with research if it can produce something useful or greater knowledge. However, the issues you write of can be addressed without reference to speculation on whether we are simulations, or whether the species can survive long enough to produce simulations like ourselves, or to colonize other planets.


  4. Hi ejwinner,

    With regard to this article, needless to say I find a great deal to disagree with. I’m quite taken with the mathematical universe hypothesis in particular, as you are probably aware, but I also have a much higher opinion of most of the other ideas you attack.

    1. The Holographic Universe

    You’re quite wrong about this, as it is only bad science journalists who represent this as a metaphysics about what reality is. In actual fact, the holographic principle is a theorem in physics about how much information is required to describe the state of a volume. It turns out that the state can be encoded on the surface of a sphere like a hologram. It shows that it is valid mathematically to treat the observable universe as such a hologram, but it is not at all a statement about what the universe actually is. After all, the observable universe is just an arbitrary volume of space with the earth at the center. There is no reason to think it is any different from any other volume of space, and that fact seems to make nonsense of the suggestion that the observable universe is *actually* a hologram.

    2. The Simulated Reality

    As you point out, this is just the hypothesis that reality could be simulated such that observers within the reality would perceive their world as physical. That seems to me to be perfectly valid. However, almost nobody argues that the universe actually is simulated. Even Bostrom doesn’t go so far. He doesn’t, as you suggest, make assumptions upon assumptions leading to a conclusion which is no more than an assumption. Rather he argues that either universes with lots of observers are almost never simulated or we are probably in a simulation. Either horn of that dilemma is fine.

    The simulated reality is an interesting thing to think about but I wouldn’t confuse it with a complete metaphysics that is supposed to explain everything. I do think it is possible that we are in a simulation but this should not be confused with believing we are. In fact I think the possibility is negligible.

    3. The Computational Universe

    I think you’re conflating two different ideas in this article. The first is the view that the universe is itself a computer which computes its own state as it evolves. That’s mostly just a way of looking at things — the only metaphysical claim it makes being that the laws of physics are computable. Sometimes describing things in new ways can provoke new ideas or solutions, and I think that’s what this attempts to do. I don’t really go along with it: not because I think it’s wrong but because I am unconvinced of its utility.

    Tegmark’s Computational Universe Hypothesis is not a variant of this in my view, but is instead a weaker version of his Mathematical Universe Hypothesis, as I will now explain.

    4. The Mathematical Universe Hypothesis

    Of the ideas you mentioned, the only one that actually has the characteristics you criticise is the MUH (and the weaker CUH).

    The MUH is the hypothesis that all mathematical structures exist. Some correspond to what we might call universes and contain self-aware substructures we can treat as observers. Furthermore, it is claimed that this universe is just such a mathematical structure and we are such observers. The CUH variant weakens these claims slightly by postulating that perhaps only computable mathematical structures exist. The difference between computable and uncomputable structures is a somewhat technical one and Tegmark raises it only to answer some specific objections raised against his MUH. As such I feel the CUH and MUH can be treated as the same basic idea for our purposes.

    Since the MUH is the only idea you bring up that really matches what you seem to be attacking, I will concentrate on defending it and leave the rest.

    Firstly, contrary to what Tegmark might have to say, I do not regard the MUH as physics but as metaphysics. I don’t think you need any particular mathematical or physics expertise in order to grasp it or argue against it. Mathematics and physics are useful as sources of inspiration and intuition, but detailed knowledge is irrelevant because the MUH posits that all mathematical structures exist, meaning that the specifics of this universe don’t have much to do with it.

    “The first impression I get from all of these metaphysics, is that there’s a deep streak in the human consciousness of denial of reality. ”

    So, your first impression is that the MUH arises not from deep reflection and development of ideas over time but from some sort of psychological need to deny the obvious. I beg to differ. I came up with the MUH independently of Tegmark, and I can trace its development in my mind over many years. I have gone through the steps in my reasoning in my blog and would strongly deny any such underlying psychosis.

    “I find it extraordinary that clearly highly intelligent men and woman can indulge in what are clearly mystical speculations”

    It is not at all clear to me that these are mystical speculations. Again, I urge you to go through the argument on my blog. Whether I’m right or not, I am at least trying to present clear reasons for my views.

    “What is it? the stench of being human?”

    Not at all. Again, you’re implying that there is some kind of pychosis to blame, ignoring the possibility that there are actual reasons for these beliefs. Isn’t that a little arrogant? Not everybody who holds views you disagree with is crazy.

    “Secondly, this primacy of mathematics and computer simulations is putting the cart before the horse – or rather, it is saying that because there is a cart, the horse must be unreal *.”

    Rather it is saying that the cart and the horse are made of the same stuff. Just because the universe is made out of mathematics doesn’t mean it isn’t real. Rather it means that reality is fundamentally a mathematical construct.

    “These metaphysicians seem either to ignore the fact that mathematics and computers are invented by humans as tools for their use, or they think that the very fact of the invention indicates some greater truth about reality.”

    As you are probably aware, there are two major schools of thought on philosophy of mathematics (realist and anti-realist), and the debate has raged for a long time. You seem to assume some sort of
    anti-realist nominalism, and portray realist Platonists as blind to or ignorant of this point of view. Again, I would suggest that it might be more productive for you to pay some attention to the reasons for Platonism rather than assuming your opponents are ignorant or deluded.

    “‘Eureka! Don’t you see, that’s clear evidence that we are merely layers of paint on the firmament!’”

    So you think the argument is that we see some similarity between a human construct and reality and we then assume that reality must be just such a construct.

    Except that that is never the argument. There are invariably reasons for the ideas you propose and you are not even trying to engage with them.

    “The mathematical/ simulation/ holographic universe is clearly more perfect than the one we have now.”

    This bears no relationship to anything in mine or Tegmark’s thought process, I assure you. What do you even mean by “perfect”? This smacks of theological talk of purity, but nothing could be further from the kinds of analytical reasoning that lead to ideas such as the MUH.

    “how can the physical possibly be hi-jacked to disprove its own physicality?”

    Because that’s not quite what is happening. What is happening is various attempts to explain what physicality actually is.

    In conclusion, your article comes across to me as strong on rhetoric and invective, but quite weak on argument. I would suggest that you try engaging with what your opponents actually say rather than painting them as fools or simpletons for sport.


  5. DM,
    I can tell by the tone that you are somewhat upset with the article. First, please understand that nobody’s charging psychosis here. I have a sometimes aggressively critical view of certain political and religious theories too, but I don’t charge ‘psychosis’ against those who hold to them.

    However, I certainly can raise critical questions concerning their motivations. All philosophies have motivations, and many of these, despite our denials, arise from the personal. Pain led me to Buddhism, Pragmatism resolved confusions arising from studying Deconstruction for my graduate degree, anti-realist nominalism allows me to maintain detachment from the temptation to take my own ideas too seriously. All these are personal motivations that I admit, and I continually find similar or similarly personal motivations in most of the texts of philosophy.

    However, I am not a professional philosopher; I’m an essayist. I have no qualms about using the tools of rhetoric to persuade readers to look at certain subjects in a different light than hitherto, even if that should be a harsh light or, in other cases, a warm, cozy glow. On the other hand, I always assume an intelligent reader, and have no interest in bullying or commanding readers to agree with me. The texts on the metaphysics discussed here are available in print and on the internet, and my readers can search them out and make of them what they will.

    The question whether metaphysicians simply don’t like being human actually applies to a great many metaphysics, old and new. That’s why Diogenes, hearing Socrates had defined humans as featherless bipeds, plucked a chicken and tossed it at Socrates’ feet, saying, ‘there’s your human.’ That’s why, when asked whether dogs had Buddha Nature, Zen monk Joshu simply replied “mu” (basically, ‘no such question’). Chickens are not human, the Buddha Nature is an abstraction, computer simulations are something we do.

    As an essayist, whose employment is in a field wholly unrelated to my writing or reading, I don’t have much time to go into the details. (Also, I have not been engaged in professional reading or writing for some 15 years, and admit my knowledge base is somewhat out of date.) My purpose in writing this blog is simply to explore issues of concern, and hopefully direct to further questions concerning them. If I came out so strongly here, it is because I honestly feel that the metaphysics derivable from undeniably useful mathematics, computation, and physics, are leading into an intellectual cul-de-sac, where they will be unable to address more basic concerns that are shared with those outside of the sciences or philosophy.

    I have read the blog post you linked to, and unfortunately, I find nothing there that changes my mind. I may write a critique of it, and will certainly do so if you wish, but am hesitant, because I wish no animosity between us.

    ““how can the physical possibly be hi-jacked to disprove its own physicality?”
    Because that’s not quite what is happening. What is happening is various attempts to explain what physicality actually is.”

    From your blog: “So given that physicality as applied to universes seems to be incoherent, and given that physicality is the only (completely undetectable) property that distinguishes the mathematical universe from the physical universe, it seems to me that the only sensible conclusion is that only the mathematical version of our universe exists.”

    That is not an explanation of the physical, it can not begin an explanation of the physical.

    As an anti-realist nominalist, I can hold that concepts are mental phenomena used to understand the world, without denying that the world is actually there, which allows me to use words like ‘really’ and ‘reality’ without violating my own philosophic stance. It also allows me to accept certain constructs of experience as illusory, without assuming that somehow experience itself is illusory. It’s not. It’s the only being we can have. That is the point I wanted to attract attention to in my essay, and its a position I am loathe to move from barring the voice of god (and presuming I am under no discernible or probable physical influence when I hear it, which likelihood is probably nil).


    • Hi ejwinner,

      Like you, I don’t want any animosity. I was somewhat vexed with your article, but not because it challenges a position I hold. Rather, my annoyance was because it did so by only by postulating motives and biases without really engaging with it at an intellectual level.

      Questioning motives is perfectly legitimate, but in my view it should be a supplement to a critique of a view on the view’s merits rather than the main thrust of an argument, as to do otherwise is more or less the ad hominem fallacy.

      I don’t think a fair critique of my post would raise my hackles. In fact I am quite eager to have weaknesses in my argument spelled out. I certainly did not expect to change your mind — that almost never happens — but I hope that you might find in it specific points of reasoning to take issue with rather than jumping to a criticism of a conclusion you find implausible. However, my argument is actually that mathematical Platonism, functionalism and naturalism entail the MUH. If you disagree with mathematical Platonism (or functionalism or naturalism), then you can accept my argument without embracing the MUH, but if so then you should at least acknowledge that there may be reasons to believe the MUH that don’t simply stem from an irrational hatred of reality or being human.

      Your quote from my blog does indeed seem to show me contradicting myself. I think however that the contradiction is superficial. What I am saying is that embracing the MUH leads to a recalibration of what the term “physical” means, and that other interpretations become apparently incoherent. So in my view I am not denying that the universe is physical — I am explaining what my take on the proper interpretation of “physical” is. Meanwhile I deny that the traditional, intuitive interpretation of the word is meaningful.

      Here I could be accused of equivocation or argument by stipulation. Perhaps. I see what I am doing as a little more like what the compatibilists do with free will. Like the compatibilists, I see a familiar concept in its traditional form as incoherent and propose a different interpretation that picks out the same situations and circumstances but in a more robust fashion. So, from my point of view, telling me the MUH implies the universe is not physical is like telling a compatibilist that compatibilism implies we have no free will. Manifestly, the universe and its contents are physical, because what physical means is (very roughly) “things we can sense or causally interact with”. There is no denying that a table is physical in a way that the number 4 is not.

      The difference between how you and I think of physicality is that to me it is a relative concept. The table is physical to me because I am a self-aware substructure in a mathematical structure and the table is another substructure in the same structure. What I deny is the idea of ultimate, observer-independent physicality, which is rather like how the compatibilist denies ultimate uncaused free will.

      Similarly I am not saying that our existence is illusory or that our perception of our reality is illusory (unless you can find a quote where I say just that, in which case I will no doubt find a way to weasel out of it yet again 😉 ). I think we exist and I think we are real. If there is an illusion, it is that there is an observer independent difference between the physical and the abstract — but that’s not so much an illusion really as a predictable and understandable artifact of our point of view, kind of like the “illusion” that the earth is at the centre of the universe or that I am a real conscious person with a body and a biography and so on while you are a disembodied anonymous avatar on the Internet.


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