About Rationally Speaking


Rationally Speaking is a blog maintained by Prof. Massimo Pigliucci, a philosopher at the City University of New York. The blog reflects the Enlightenment figure Marquis de Condorcet's idea of what a public intellectual (yes, we know, that's such a bad word) ought to be: someone who devotes himself to "the tracking down of prejudices in the hiding places where priests, the schools, the government, and all long-established institutions had gathered and protected them." You're welcome. Please notice that the contents of this blog can be reprinted under the standard Creative Commons license.

Friday, January 24, 2014

Is information physical? And what does that mean?

by Massimo Pigliucci

I’ve been reading for a while now Jim Baggott’s Farewell to Reality: How Modern Physics Has Betrayed the Search for Scientific Truth, a fascinating tour through cutting edge theoretical physics, led by someone with a physics background and a healthy (I think) dose of skepticism about the latest declarations from string theorists and the like.

Chapter 10 of the book goes through the so-called “black holes war” (BHW) that stretched for two and a half decades between Stephen Hawking on one side and Leonard Susskind, Gerard ’t Hooft, and others. The BHW is interesting because Baggott turns it into an illustration of what he thinks is the problem with current theoretical physics, a problem that has much to do with philosophical theories of truth and with the difference between physics and metaphysics.

The BHW began with a challenge issued by Hawking at a scientific gathering back in 1981. Quantum theory maintains that information carried by the wave function of a quantum object cannot be destroyed, it must be preserved because it connects past and future. But Hawking (who is a relativist, not a quantum theorist) had arrived at the conclusion that black holes evaporate over time, emitting what is now known as Hawking radiation. Since everything that ends up inside a black hole’s event horizon can be thought of as representing bits of information, Hawking concluded that while the black hole is evaporating information is not just scrambled — as previously thought — but actually destroyed, thereby contradicting a crucial tenet of quantum theory. Oops!

You can see why Susskind and ’t Hooft, who are quantum theorists, didn’t like this thing, ahem, a single bit. The BHW was on.

It took Susskind, ’t Hooft and Don Page a number of years to do it, but they finally came up with a serious counter to Hawking’s challenge, indeed one that led Hawking to admit defeat in 2007. The best known visual metaphor that captures the response is Susskind’s famous “holographic universe.” The principle essentially states that the information contained in an n-dimensional space (let’s say, a three-dimensional black hole, for instance) is equivalent to the information found on its n-1 dimensional boundary (for example, the surface of said black hole).

Susskind boldly proposed that the universe itself behaves as a hologram, i.e., that all the information that constitutes our three-dimensional world is actually encoded on the universe’s equivalent of a black hole’s event horizon (the so-called cosmic horizon). If true, this would mean that “reality” as we understand it is an illusion, with the action actually going on at the cosmic horizon. Baggott ingeniously compares this to a sort of reverse Plato’s cave: it isn’t the three-dimensional world that is reflected in a pale way on the walls of a cave were people are chained and can only see shadows of the real thing; it is the three-dimensional world that is a (holographic) projection of the information stored at the cosmic horizon. Is your mind spinning properly? Good.

What does any of this have to do with the BHW? That became clear in 1998, when Juan Maldacena (theoretically) demonstrated a “superstring duality”: it turns out that the physics of an n-dimensional spacetime described by a particular type of superstring theory (which one doesn’t really matter for our purposes here, but you’ll find all the details in Baggott’s book) is equivalent to the physics described by a quantum field theory applied to the n-1 dimensional boundary of that same spacetime. This result has deep connections with the idea of a holographic universe, so much so that Susskind eventually wrote in triumph:
Whatever else Maldacena and Witten had done, they had proved beyond any shadow of a doubt that information would never be lost behind a black hole horizon. The string theorists would understand this immediately; the relativists would take longer [ouch!]. But the war was over.
Indeed, as I said, Hawking conceded in 2007, thus ending the BHW, despite some rather large caveats attached to the Maldacena-Witten results, such as that, you know, they actually describe a universe that is not at all like our own.

And now comes what Baggott properly refers to as the reality check. Let us start with the obvious, but somehow overlooked, fact that we only have (very) indirect evidence of the very existence of black holes, the celestial objects that were at the center of the above sketched dispute. And let us continue with the additional fact that we have no way of investigating the internal properties of black holes, even theoretically (because the laws of physics as we understand them break down inside a black hole’s event horizon). We don’t actually know whether Hawking radiation is a real physical phenomenon, nor whether black holes do evaporate.

To put it another way, the entire BHW was waged on theoretical grounds, by exploring the consequences of mathematical theories that are connected to, but not at all firmly grounded in, what experimental physics and astronomy are actually capable of telling us. How, then, do we know if any of the above is “true”? Well, that depends on what you mean by truth or, more precisely, to what sort of philosophical account of truth (and of science) you subscribe to.

There are several theories of truth in epistemology, but the two major contenders, especially as far as the sort of discussion we are having is concerned, are the correspondence and the coherence theories. Roughly speaking, the correspondence theory of truth is what scientists (usually without explicitly thinking about it this way) deploy: in science a statement, hypothesis or theory is considered (provisionally, of course) true if it appears to correspond with the way things actually are out there. So, for instance, it is true that I wrote this essay on an airplane on my way between Rome and New York, because this statement corresponds with reality as ascertainable via a number of empirically verifiable facts (e.g., my airplane tickets, witnesses who saw me boarding, deplaning and writing on my iPad in between, time stamps encoded in the file I generated, and so on). 

A coherentist account of truth seems to me to be more appropriate for fields like mathematics, logic, and perhaps (to a point) moral reasoning. Coherentism is concerned with the internal consistency of a given account, eschewing any reference to correspondence with a reality that, by definition, we can only access indirectly (after all, if you wish to measure the degree of correspondence between your theories and the way things really are, it would seem that you need some kind of direct access to the latter; but you don’t have it, that’s why you need theories to begin with; there are ways around this, but they would lead us too far from the matter at hand).

Back to the outcome of the BHW: in what sense is the holographic principle “true,” given our short discussion of theories of truth? As Baggott reminds his readers, the principle hasn’t been established by way of empirical observations or experiments, so it cannot possibly be true in the sense of the correspondence theory. Rather, it has been arrived at by way of superstring theory, which itself is a theoretical structure which has, so far, not been empirically tested either. The holographic principle, therefore, is true — at best — in the sense of the coherence theory of truth. But the history of physics is littered with examples of beautifully coherent theories that turned out to be wrong when the empirical verdict finally came in. Perhaps Hawking conceded a bit prematurely, after all.

Finally, back to the idea that “information is physical.” What does that mean? Baggott summarizes the two possibilities thusly: “The scientific interpretation acknowledges that information is not much different from other physical quantities [like, say, temperature]. But, as such, it is a secondary quality [italics in the original] … The metaphysical interpretation suggests that information exists independently of the physical system, that it is a primary quality [original italics].” He concludes that he has no problem with either interpretation, as long as nobody is going to attempt to pass the second one as science. I couldn’t agree more.

42 comments:

  1. When physicists such as these get pinned in a corner, they'll usually at least admit that superstring theories and such aren't yet verified, but it seems that they invariably slip back into language that would suggest otherwise. I love physics and physicists, but it would be nice if some of them could clean up their acts. It reminds me of how everyone was talking about how our universe could be a program, and then jumping to the assumption of a programmer (especially with human characteristics like consciousness).

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  2. Hi Massimo,

    I would take issue with a number of points here.

    Firstly, I suspect (and I could be wrong here) that you tend to conflate string theory and superstring theory. Superstring relates to a particular type of string theory that assumes supersymmetry. I don't think the holographic principle has anything to do with supersymmetry.

    >a healthy ... dose of skepticism about the latest declarations from string theorists and the like.<

    I think even string theorists are skeptical about their "declarations". I really don't think string theorists are in the habit of presenting their findings as factual, which you seem to imply.

    > If true, this would mean that “reality” as we understand it is an illusion, with the action actually going on at the cosmic horizon.<

    I don't think this is true. My understanding is that what goes on within a volume can also be described in terms of what goes on at the periphery of that volume. There is no "THE cosmic horizon". Cosmic horizons can be chosen arbitrarily. With no single cosmic horizon, it cannot be the case that the action is "really" going on there.

    >we only have (very) indirect evidence of the very existence of black holes<

    I have a problem with that "very".

    >the laws of physics as we understand them break down inside a black hole’s event horizon<

    I think it would be more precise to say they break down at the singularity. There's nothing particularly special about the event horizon apart from the fact that it's a point of no return.

    On the larger point, I disagree that the lack of verification is a particular problem for theoretical physics.

    Take the standard Socratic syllogism as an analogy. All men are mortal, Socrates is a man, therefore Socrates is mortal.

    How do we know Socrates is mortal? We have only (very) indirect evidence that this is the case, and let's not forget that we have only (very) indirect evidence that Socrates ever even existed. Nevertheless, it is true in a coherentist sense, but "the principle hasn’t been established by way of empirical observations or experiments, so it cannot possibly be true in the sense of the correspondence theory".

    Of course this is not correct. "Socrates is mortal" is indeed true in the correspondence theory, and the fact that we can't prove this beyond doubt doesn't change this. The claims made by theoretical physicists are no different. It is more than possible that they are true in the correspondence theory, it is *likely*. For the claims about black holes made by Hawking and Susskind to be incorrect, some pretty basic physical premises (analogous to "Socrates is a man" or "All men are mortal") would have to be false.

    And that could be the case. But if so, then all bets are off. The original Black Hole debate could be construed as a debate about the truth of Hawking's claim that there is no theoretical mechanism by which information could be conserved in black holes. And that was resolved, conclusively. Framing the disagreement this way, Hawking did not concede prematurely.

    >Rather, it has been arrived at by way of superstring theory, which itself is a theoretical structure which has, so far, not been empirically tested either<

    I think this is slightly misleading. It has been worked out in detail in the context of string theory but even if string theory is false the holographic principle is probably true, given that it resolves a paradox and is consistent with what is known about the entropy of volumes.

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  3. I think Baggott's book is important. I hope it has an impact. As he says repeatedly in it, there's nothing wrong with theoretical speculation far beyond the bounds of empirical testing, but there is something wrong with treating its conclusions as having anywhere near the certainty of theories with experimental successes, such as the standard model.

    This appears to be a brewing controversy however. Sean Carroll, in his Edge response, ponders whether falsifiability is worth keeping. (And his reasoning doesn't seem that unusual in the theoretical physics community.)
    http://www.edge.org/response-detail/25322

    I'm a fan of Carroll, but he seems to cutting some mighty thin hairs here. I fear such an attitude gives paranormalists, and other woo purveyors ammunition in their arguments that modern science should include them.

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  4. Some interesting synchronicity:

    http://arxiv.org/pdf/1401.5761v1.pdf

    Hawking's recent paper is titled "Information Preservation and Weather Forecasting for Black
    Holes", a commentary on this very topic.

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  5. It seems to me that saying "information" is secondary (to what?) or primary are equally not science.

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  6. Any help for a beginner? I am stuck on the problem of how "information" in a black hole can be attributed with any confidence to matter secondarily, or "independently of the physical system" primarily. For it seems that all observation is performed in time, and thus every observation, by its beginning and ending, will introduce sinc-function spectral content to the event, which thereby pollutes the "information." Therefore, needn't we say the information is essentially conceptual, and not just because peripatetics were clever about it, but becaue observation is so noisy? I suppose this makes me a correspondence theorist. The informant must be there, in a non-Platonic-formal way, even if I never perceive it per se. For my own internal coherence of information would only be logic, not reality.

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  7. Physical information (which is the topic of the black hole wars) is dynamically enforced correlations between property values. The question is whether the evaporation of black holes breaks the correlation between the early-time state of the universe and the late-time state of the universe.

    This notion of information is unproblematic and (according to us physicalists) is the foundation for any more specialized form of information we might be interested in (e.g., biological, psychological, social).

    "the principle hasn’t been established by way of empirical observations or experiments, so it cannot possibly be true in the sense of the correspondence theory."

    This claim seems odd. I'd have thought the the correspondence theory merely requires that the world actually be the way the true claim says it is. It doesn't require observation.

    My claim that there is a flying saucer orbiting Saturn in true just in case there is indeed such a flying saucer. The fact that I can't see it is irrelevant (or so I'd have thought.

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  8. Black holes and sting theories and shadows in Plato's cave? Get real!!! So how was your trip to Italy Professor, or wasn't it real enough? =

    ...Oh and as for physics, the measure of nature, temperature, and all that science nonsense you like to write about, surely you know or should know that the Universe is truly immeasurable. Surely you must know that outside their cave (or your cave) of theories and doubts is true Italy.
    Viva Italia!

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  9. The correspondence and coherence "theories" can probably be reconciled into a single concept by replacing the word "true" with " level usefulness." This is one of those cases where there's so much confusion that can't be navigated because of the limitations of certain words - like "truth" - to describe something we are interested in. There's just so much linguistic baggage there that can probably never be shed

    Usefulness is a better conceptualization of what we are interested in and what we are probably talking about anyways. Certain models of reality are better - or more useful - than others. The atomic theory is better than the 5 elemental system of the greeks because it's more useful. To describe one as "true" and one as "not true" doesn't get us to far and is probably just a case of us mapping an inappropriate binary reality onto things where there is none. We know our brains often make things artificially digital.

    Empirical proofs that model reality in better ways are more useful than those that don't in terms of making predictions or explaining things we can observe. Mathematical proofs that are internally consistent are more useful because they can help solve or navigate related problems. Again, what we are really interested in is usefulness, and trying to "solve" things in terms of the word "truth" is probably one of those of those areas that's easy to be diverted into, but probably impossible to get out of no matter how much we talk about it.

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  10. What if everything IS information? Wouldn't an ontology of information unify the two, technically?

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  11. I attended (semi-technical) lectures by Susskind for five years. He mentioned the holographic principle several times but he never once claimed it was "true". It's purely a mathematical result and whether you consider "truth" to apply to mathematical results has nothing to do with the kind of empirical results that would cause a physicist to regard something as true.

    And by the way, the subject of the theory of black hole horizons has recently become controversial again. Google "black hole horizon firewall". Both Susskind and Hawking are actively involved is resolving this issue.

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  12. I'm going to riff in a different direction, off astrophysics and cosmology and back to philosophy, per this comment by Massimo:

    "A coherentist account of truth seems to me to be more appropriate for fields like mathematics, logic, and perhaps (to a point) moral reasoning."

    Ahh, that explains part of the defense of virtue ethics. And, I guess this is another reason I'm a bit queasy about it. And, a reason beyond how the "view from nowhere isn't realistic" on why I'm queasy about consequentialism, too.

    I'm not a system-builder in general, and definitely not a Kantian on ethics. I do believe, though, that evolutionary psychology, done right, has something to say about ethics, and that's why I'd say the correspondence theory of truth has something to say on ethics.

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  13. Massimo,

    >in what sense is the holographic principle “true,” given our short discussion of theories of truth?<

    As a deflationist (Tarskian) about truth (which I take to be a topic of philosophical logic rather than epistemology; truth is a logical concept after all) I think framing the concern here in terms of truth obscures the interesting questions.

    The holographic principle is true iff *assertion of the holographic principle*. So much for truth.

    What's interesting are certain conditions of the principle being true. The principle is true iff the entities it posits exist and have the attributes the principle asserts them to.

    Within this, what's compelling is the question of whether the entities posited by the principle exist.

    I don't have a whether-or-not view on this question. My point is just that the interesting issues relate to existence rather than truth.

    If a theory in physics is predictively perfectly accurate, does that mean the entities it posits "really" exist, or (somewhat differently) that we're somehow entitled to say they exist? If not, what else might be the criterion of existence regarding entities posited by such theories?

    >A coherentist account of truth seems to me to be more appropriate for fields like mathematics, logic, and perhaps (to a point) moral reasoning.<

    Do you mean to suggest that different domains of knowledge might call for different accounts of truth?

    To me this seems a mistakenly metaphysical notion of truth: in different contexts - you seem to suggest - what makes a truth true is part of the meaning of the word 'true' when used with respect it. In empirical cases 'true' means correspondence with reality; in ethics it might mean coherence. But is this really how language works? Does the word 'true' change in meaning with regard to different kinds of propositions to reflect what makes the proposition true?

    To me it seems that something being the case and what makes it the case are conceptually distinct matters.




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  14. Gadfly,

    My guess is that holding the correspondence theory of truth (consciously and critically or not) is a major cause of ethical skepticism. If one sees propositions as true or not depending on whether they are good paintings of observable reality, then one is likely to be at a loss regarding how ethical propositions, which are not paintings of anything, can be true.

    The deflationist makes short work of truth then looks at the different ways propositions might be made true.

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  15. My impression was that AdS/CFT correspondence (what Massimo called "superstring duality") is an idea that came from string theory, but does not itself rely on string theory. (Does anyone know?)

    I thought the holographical principle was basically math. Seeing it as math, I'm not really bothered by the lack of experimental input. We can still argue, in a mathematical way, over whether it's true.

    As for whether it's "real", who can say? Personally, I'm happy to think of the holographic description as equally real as our standard description.

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  16. Massimo,
    Did you read this?

    http://www.nature.com/news/stephen-hawking-there-are-no-black-holes-1.14583

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  17. Progress (in physics and even mathematics) comes when a new theory amends the "truth" of the old.

    "the theory justifies the objects it talks about"
    Differential Calculus and Nilpotent Real Numbers
    Anders Kock
    The Bulletin of Symbolic Logic
    Vol. 9, No. 2 (Jun., 2003), pp. 225-230
    home.imf.au.dk/kock/real.pdf

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  18. DM,

    > I would take issue with a number of points here. <

    Why doesn’t that surprise me… ;-)


    > I suspect (and I could be wrong here) that you tend to conflate string theory and superstring theory <

    No, I’m aware of the difference, but these days several authors use the two terms interchangeably. In my post it always refers to superstring theory.

    > I don't think the holographic principle has anything to do with supersymmetry. <

    My understanding is that you are incorrect, at least according to Baggott.

    > I think even string theorists are skeptical about their “declarations". <

    Baggott (as well as Woit and Smolin) go through this and they find an insufficient degree of skepticism, particularly by people like Greene.

    > My understanding is that what goes on within a volume can also be described in terms of what goes on at the periphery of that volume. There is no "THE cosmic horizon”. <

    That was pretty much straight from Baggott, as you know, I’m not a physicist, I rely on other people’s expertise for this sort of things.

    > Take the standard Socratic syllogism as an analogy. … it is true in a coherentist sense <

    Of course, it’s logic. But in science coherentism just isn’t enough.

    > "Socrates is mortal" is indeed true in the correspondence theory, and the fact that we can't prove this beyond doubt doesn't change this. <

    The syllogism in question isn’t supposed to be a scientific theory about the real world, it’s just an arbitrary example to illustrate how a basic type of logical reasoning works. You really need to pick a different example.

    > For the claims about black holes made by Hawking and Susskind to be incorrect, some pretty basic physical premises (analogous to "Socrates is a man" or "All men are mortal") would have to be false. <

    My understanding is that that is very far from the actual state of knowledge in physics. At any rate, my (and Baggott’) main objection is to superstring theory and the holographic principles, not to black holes per se.

    > Framing the disagreement this way, Hawking did not concede prematurely. <

    Yes, but my point is that perhaps the debate should be framed a bit less narrowly.

    > It has been worked out in detail in the context of string theory but even if string theory is false the holographic principle is probably true, given that it resolves a paradox and is consistent with what is known about the entropy of volumes. <

    So you are saying that you have more confidence in an entirely theoretical structure that is based on another entirely theoretical structure, even though the latter could be false? Hmm…

    SelfAware,

    > I'm a fan of Carroll, but he seems to cutting some mighty thin hairs here. <

    I’m a fan too, but I may address Sean’s Edge post next…

    > I fear such an attitude gives paranormalists, and other woo purveyors ammunition in their arguments that modern science should include them. <

    Indeed, while superstring theory, the holographic principle and all the other are most definitely not pseudoscience, these people really ought to be concerned with the image of *science* they are projecting to the public.

    Philip,

    > It seems to me that saying "information" is secondary (to what?) or primary are equally not science. <

    I see your point, but I think Baggott’s argument is that it is natural to interpret information as a “secondary” quality, in the sense that it is a result of the behavior of certain classes of physical objects. If so, then the burden of proof is on those who wish to promote it to the status of “primary” quality. And of course discussions about primary vs secondary qualities usually are philosophical (“metaphysical”) not scientific.

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  19. Niq,

    > For my own internal coherence of information would only be logic, not reality. <

    I’m not sure I followed your comment entirely, but it seems to me you are getting to the issue of whether information is inherent into physical objects or whether it requires an “observer.” I think it certainly doesn’t require an observer, at least not in the sense of a conscious one. It is not just a metaphor, for instance, to say that DNA carries information that is “read” by certain classes of molecules to make other classes of molecules. And none of these molecules is conscious. But perhaps you were getting at something entirely different.

    Peter,

    > This claim seems odd. I'd have thought the the correspondence theory merely requires that the world actually be the way the true claim says it is. It doesn't require observation. <

    But how do you know how the world actually is, if not — indirectly — via observation and/or experiment?

    > My claim that there is a flying saucer orbiting Saturn in true just in case there is indeed such a flying saucer. The fact that I can't see it is irrelevant <

    But if we are talking about knowledge, if you can’t see it you can’t know whether it’s true or not.

    jefscott,

    > The correspondence and coherence "theories" can probably be reconciled into a single concept by replacing the word "true" with " level usefulness.” <

    That would nudge us toward some sort of pragmatic theory of truth, which has its own problems, and a discussion of which really is beyond the scope of this post.

    > Certain models of reality are better - or more useful - than others. <

    Well, to begin with, you need to unpack the concept of usefulness you are deploying here. Second, I think most scientists would not be satisfied with the resulting anti-realism about scientific theory that comes out of pragmatic approaches like this one. Scientists generally subscribe to a correspondence theory of truth, whether they realize it or not.

    > Mathematical proofs that are internally consistent are more useful because they can help solve or navigate related problems. <

    But scientific and mathematical usefulness are very different from each other, considering that the first one regards the physical universe and the latter doesn’t (at least, not primarily).

    Troy,

    > What if everything IS information? Wouldn't an ontology of information unify the two, technically? <

    Well, yes, and some people do go down that alley. But one needs to explain in what sense everything is information, on penalty of loosing any coherent meaning of the term information.

    Gadfly,

    > I do believe, though, that evolutionary psychology, done right, has something to say about ethics, and that's why I'd say the correspondence theory of truth has something to say on ethics. <

    But I wouldn’t argue that virtue ethics requires only coherence. Remember that for Aristotle (and Hume!, who was no virtue ethicist) a proper analysis of human nature is fundamental to ethics. Which means that yes, science can provide input into moral reasoning (it just can’t settle the whole thing). However, I’d pick psychology and anthropology over evopsych. It doesn’t really matter *why* certain human behaviors evolved (which is hard to ascertain anyway), it matters how widespread and flexible they are.

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  20. Paul,

    > The holographic principle is true iff *assertion of the holographic principle*. So much for truth. <

    I know, but that’s precisely why deflationary theories of truth leave me cold. After your assertion above what am I supposed to do about the holographic principle?

    > The principle is true iff the entities it posits exist and have the attributes the principle asserts them to. <

    But how do you know? Seems like you are veering again toward some sort of correspondence concept…

    > My point is just that the interesting issues relate to existence rather than truth. <

    Yes, but — with Quine (I can’t believe I just wrote that!) — I don’t think that metaphysics and epistemology are independent of each other.

    > If a theory in physics is predictively perfectly accurate, does that mean the entities it posits "really" exist, or (somewhat differently) that we're somehow entitled to say they exist? <

    As you probably know, this is the realism / anti-realism debate in philosophy of science. Fascinating, but I didn’t want to get into that for the purposes of the post.

    > Do you mean to suggest that different domains of knowledge might call for different accounts of truth? <

    Yes, that’s exactly what I mean to suggest. I think “truth” is a pluralistic concept.

    > in different contexts - you seem to suggest - what makes a truth true is part of the meaning of the word 'true' when used with respect it. <

    Correct. 2+2=4 is true, and so is the fact that Saturn has rings. But I see huge differences between the two cases, so I may use Tm and Te (mathematical and empirical truth, respectively) to more carefully indicate that.

    > Does the word 'true' change in meaning with regard to different kinds of propositions to reflect what makes the proposition true? <

    That’s a question for social scientists and linguists. As a philosopher, I’m more interested in the question of whether the meaning of truth *should* change with usage, and I think it should.

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  21. Massimo, can you elaborate on what you mean by secondary qualities?

    My understanding of the term goes back the Locke's idea of it, but I thought that was done away with by Berkeley.

    You give the example of temperature. I can see how temperature is a function of the energy of motion of a gas in a container. Is that what you mean by secondary quality?

    What might be another example I can use to try to grasp this idea?

    What about something like hardness?

    Can it be something more subjective, like catchy-ness of a song, with the song being the object.

    I remember there being a response to the mind-body problem that talked about universities and the buildings, and the university just being the thing that exists when you combine the buildings and people and activities. The idea being that the mind just is the combination of the various activities of the brain.

    Is a secondary quality something like that, where a university (or mind) is a secondary quality of the objects and activities that occur? That doesn't seem right to me for some reason.

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  22. Another fascinating post. I loved reading the BHW not just for the science, but the window into the personalities and process of physicists. I haven't read Baggott's book yet, but I will. Right now I'm wading through "Meta Metaphysics" Massimo, if you have time, give me a hint about how you feel about that collection. Your initial reference was cryptic.

    DM, thanks for pointing out the difference between a black hole's event horizon and its singularity. It was just a technical mistake that doesn't affect Massimo's point, but what happens between the event horizon and the singularity is so fascinating it's worth pointing out. If you were in a spaceship you wouldn't even notice crossing the event horizon, yet your fate is sealed. Susskind talks about how this moment creates two very different realities.

    As to information being primary or secondary, it seems to me that this distinction, when properly untangled, will inform the discussion about consciousness and whether or not we should be Platonic about mathematics. Oddly, this post by Massimo ends up being less about the philosophical implications of that notion and more about the demarcation problem.

    Doesn't confidently saying that information is secondary also solve the question of consciousness? Consciousness would be secondary just in the same way as information is. Or should I say consciousness is secondary to information which is secondary to matter?

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  23. Massimo,

    >> The principle is true iff the entities it posits exist and have the attributes the principle asserts them to. <

    But how do you know? Seems like you are veering again toward some sort of correspondence concept…<

    I mean no attempt at a definition of truth with my statement above. I see it as a matter of logic that the truth of a proposition depends on its overt or implied (existential and attributive) assertions being true.


    >> Does the word 'true' change in meaning with regard to different kinds of propositions to reflect what makes the proposition true? <

    That’s a question for social scientists and linguists. As a philosopher, I’m more interested in the question of whether the meaning of truth *should* change with usage, and I think it should.<

    I well understand and agree about the normative nature of philosophy but a philosophical analysis of a term such as truth must work closely with how the term works in language.

    By "how the terms works in language" I mean how it works as can be revealed by logical analysis, something sociology and linguistics don't do, in a philosophical sense at least.

    There is effectively little difference between a concept and its correlate linguistic expression, so if one wants to give an account of a concept, such as truth, one must attend to how to the correlate expression functions in language. A philosophical analysis is in a sense a prescription for using relevant expressions.

    If 'true' functions in a univocal way in language then a pluralist view of truth risks not being a view of truth at all. A sound analysis of a concept must begin by capturing the concept as it ordinarily functions and going from there. A notion of "truth" that bears little relation to how 'true' functions in language is effectively not about truth at all, but a theory that gives the word 'true' a deviant use.

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  24. I loved this post! If my blog is ever half as awesome as yours, I'll be the happiest man in the world!

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  25. This may just be a terminological disagreement, but I don't think *theories of truth* are at issue here, but rather *theories of knowledge* (or justified belief). You can have a correspondence theory of truth and still have a coherence theory of knowledge.

    >> in what sense is the holographic principle “true,”...the principle hasn’t been established by way of empirical observations or experiments, so it cannot possibly be true in the sense of the correspondence theory.

    The fact that a sentence can't be (or hasn't been) empirically/experimentally established doesn't entail that the sense in which it is "true" changes. For example, take the sentences, "There are 987,248 granules of salt in my kitchen salt shaker right now" and "There were 987,248 granules of salt in my salt shaker exactly 200 hours ago." Presumably these are both true or false in the straightforward correspondence sense of 'truth', but the first sentence can be empirically verified while the second one (presumably) cannot be.

    Regarding the case of physics, I see no reason for thinking that the various physical statements involved are all true or false in the correspondence sense, but the *justification* for the non-empirically-verifiable statements is necessarily coherentist.

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  26. Someone mentioned the binary tendencies of ordinary – and philosophical – thinking. Information as a primary or secondary quality. Coherence or correspondence. Mathematics or science. (Various forms of) realism or anti-realism. Good science/scientists or bad science/scientists.

    I don't deny that string theory has been over-hyped in the past, but I don't see any cause for seeing it as bad science. Sure, it's mainly a mathematical framework but physics is only comprehensible in terms of mathematics. And just because string theorists haven't managed to make the hoped-for breakthroughs yet doesn't mean breakthroughs won't be made.

    I mean, what's the hurry? Think how long it took to get from Newton to Einstein. The 19th and 20th centuries were very remarkable periods of scientific progress. We have no reason to expect that rate of progress on fundamental questions to be sustained.

    String theory is very abstract and difficult and inaccessible to most of us, and no doubt these facts have led more than a few of its practitioners to exhibit a degree of hubris and lose their sense of perspective. But so what? That's human nature.

    And I'm sure Massimo would agree that it has no bearing on the value or worth or beauty of the work in question.

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  27. "But scientific and mathematical usefulness are very different from each other, considering that the first one regards the physical universe and the latter doesn’t (at least, not primarily)."

    “Well, to begin with, you need to unpack the concept of usefulness.


    To some degree, this is my point. Of course we still have the job of describing exactly what we mean by “usefulness” and by which metrics of problem solving (empirical or mathematical) we correlate with the definition. But this leaves us in far less murky territory than trying to define “truth.” Part of the problem is that the concept of “truth” as a linguistic tool puts us in the difficult, if not impossible, position of making a binary distinction about something we are interested in. In that sense the concept of “truth” percolates into a sort of false reductionism.

    Or put another way (and in regards to your comment), the reason that “usefulness” is a better concept than “truth” in describing what we often want to talk about is PRECISELY because it is more “unpackable” than the concept of truth. So while our common cultural usage of “truth” does well as it applies to our everyday lives, it breaks down as a concept when applied to certain areas (like quantum mechanics). By way of analogy think of the way that classical mechanics describes a continuous and unbroken gradient of possibly energy states – this makes sense as an intuitive experience of everyday life (like the velocity of a baseball), but it stops being a useful concept once we talk about quantum mechanics. Truth is like this in many regards – while does well enough to describe our common interactions with the universe, at certain scales it fails to be a meaningful concept. By way of another analogy, think of how we often try to conceptualize the position of an electron – we know that in some sense the very concept of “position” fails to relate to anything meaningful. The concept of truth often leads us to this same type of failure.

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  28. I have not read Baggott's book, but there seem to be a number of inaccuracies in the physics, at least as described above.

    First, the holographic principle is being horribly caricatured. The principle is just this: it is a bound on the number of quantum states that can exist in a given region of space-time, based on its area. How you get from there to reality being an illusion, I haven't a clue.

    The claim that the holographic principle doesn't have any empirical evidence is, I think, quite false. The principle makes claims about every space-time region in the universe with certain spacial properties. This has been checked for many examples, most much more mundane than black holes, and no contradictions have yet been found.

    The holographic principle (if it continues to hold up) will, I think, be a huge advance in physics because it is a link between general relativity and quantum mechanics. Hence, it will tell us a great deal about what a theory of quantum gravity has to look like.

    The earlier commenter is correct that the holographic principle is not dependent on supersymmetry. I think Baggott is doing it a disservice by lumping it together with supersymmetry and string theory. As I said above, the holographic principle makes testable predictions, which so far appear correct. Supersymmetry makes predictions as well, but as I understand it, the evidence coming out of LHC so far goes against it. (And I don't know to what extent string theory makes testable predictions.)

    Finally, I don't know what Baggott means when he discusses "information is physical" (since I haven't read his book), but this phrase is used a lot in the quantum information community and it's meaning seems unrelated to the discussion above. (I've always heard it used in the sense of Landauer.)

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  29. Hi Massimo,

    First, let me just mention that I don't much like the new commenting format. Was this a deliberate change?

    >My understanding is that you are incorrect, at least according to Baggott.<

    Hmm, ok. I'm no expert, but there was no mention of supersymmetry on the Wikipedia page at least.

    I still think you're wrong on whether the holographic principle asserts there is a 'THE' cosmic horizon. Whether that's in your interpretation or Baggott's description I don't know. Either way, it wouldn't imply the three dimensional world is an illusion, only that there are two different but ultimately equivalent ways to describe that world.

    >The syllogism in question isn’t supposed to be a scientific theory about the real world, it’s just an arbitrary example to illustrate how a basic type of logical reasoning works. You really need to pick a different example.<

    I know it's just an arbitrary example. But I think the analogy works. I think that fundamentally there is no difference between this type of reasoning and what Hawking and Susskind are doing. Their arguments are certainly true in a coherentist sense, and they are probably true in a correspondence sense. Just as with Socrates.

    >So you are saying that you have more confidence in an entirely theoretical structure that is based on another entirely theoretical structure, even though the latter could be false? Hmm…<

    What I am saying is that I don't accept that the Holographic Principle is actually based on String Theory. It was arrived at and developed in the context of String Theory, but the basic idea makes sense even without String Theory and can be explained without reference to String Theory. It fits in so well with the physics that is generally accepted that it is probably (or perhaps even certainly - I'm not an expert) true whether or not String Theory is.

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  30. Troy's comment about an ontology of information is interesting and seems forward-looking, but I'd like to know more about say, how he would define senders and receivers of information.

    I came up with 'Everything is information" about 35 years ago. While progressing in mathematics and computer science, stayed at barely high school level in nearly all other sciences until about 5 years ago, but would say I saw nothing in all those years that would lead me to think otherwise.

    Three chinks in the theoretical armor though (1) While acceptance of information as the basic unit of our existence implies that anything is possible, there needs to be not only conceivability but also utility - therefore you are not likely to find 8 spleens playing chess at every stoplight using chess pieces made out of jokes, etc... (2) A debate is now brewing among the foundationals (those who wonder what is below matter/energy). One side says it is all information, the other side says there is something, but not willing to call it that - yet. Ladyman/Ross call it structure, Tegmark calls it math, Vedral calls it quantum information, Bohm called it an implicate order, never mind that he non-foundationally interchanged matter, information, and energy. I think these ideas can converge on standalone information, but will take a while to get there because in all four cases, one needs to prove that something that makes no sense to most could conceivably make sense to a single entity, and serve to nullify any or all other understandings. (3) The absense of any moral or ethical takeaways from recasting everything as information. It is simply a point of view, and if the worlds of philosophy and sciences cannot sell the ideas to the public at large as having any social value, well, its a problem.

    What may play a significant role in the future in tying things together are:

    - Reinvention/expansion of sociology as a key to understanding the reality we seem to be stuck with. Examples include treating of groups of people as a single object, taking another look at transactional analysis (remember I'm OK, You're OK?), and general use of consilience to unite hard and soft sciences

    - Discarding requirements of 'physical reality' to accord equal footing to imaginary things, thus if gods and coffee cups can coexist, it is all a matter of how we interpret symbols in this world.

    - Accepting backwards time flow, better yet, discarding the forward arrow of time as gospel. Doing this allows you to take all symbols from the 'mystical/religious' realm and get you to good old naturalistic interpretations of life that even Massimo would be proud to hang his hat on

    - To a lesser extent, use of mereology to get more comfortable with ideas about 2+2=5, not simply to break Western analytical mindsets, but to use the same to show how counting can be done in different ways.

    Cannot get over how good it is to see others coming up with the same ideas I kept in my head for a very long time, keeping silent because I could not find the ideas comunicated to others via non-academic channels, and was not aware of people like say Bishop Berkeley, and many other thinkers from way back who probably felt the same way.

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  31. SecularDad,

    > can you elaborate on what you mean by secondary qualities? My understanding of the term goes back the Locke's idea of it, but I thought that was done away with by Berkeley. <

    That’s the philosophical understanding of the terms, but I think people are still talking about it after Berkeley, if in modified fashion. However in this context Baggott is simply referring to the logical distinction of whether matter or information are primary.

    > You give the example of temperature. I can see how temperature is a function of the energy of motion of a gas in a container. Is that what you mean by secondary quality? <

    That’s what Baggott means, yes. Not sure it’s worth pursuing other examples since the discussion is focused on information: the question Baggott asks is whether information is like temperature or more fundamental.

    > I remember there being a response to the mind-body problem that talked about universities and the buildings, and the university just being the thing that exists when you combine the buildings and people and activities. <

    That one is slightly different: it’s a standard example of category mistake.

    OneDay,

    > Right now I'm wading through "Meta Metaphysics" Massimo, if you have time, give me a hint about how you feel about that collection. Your initial reference was cryptic. <

    Because I haven’t had time to wade through it. Stay tuned, and I’d be interested to hear what you think.

    > Oddly, this post by Massimo ends up being less about the philosophical implications of that notion and more about the demarcation problem. <

    In a sense, but I don’t find it odd, and the demarcation problem *is* a philosophical one…

    > Consciousness would be secondary just in the same way as information is. Or should I say consciousness is secondary to information which is secondary to matter? <

    Not sure that solves much, really. There would be a lot of unpacking to do, beginning with the fact that information and consciousness seem to be very distinct phenomena to me (I’m not saying they are not related, obviously!).

    Paul,

    > I see it as a matter of logic that the truth of a proposition depends on its overt or implied (existential and attributive) assertions being true. <

    Ok, but I don’t find that to be a particularly enlightening assertion. Perhaps I’m missing your broader point.

    > If 'true' functions in a univocal way in language then a pluralist view of truth risks not being a view of truth at all. A sound analysis of a concept must begin by capturing the concept as it ordinarily functions and going from there. <

    I disagree. Technical terminology can be significantly distinct from common usage without creating any conceptual problem at all. Thus I’m using “truth” in a technical, pluralist, sense, which I have elaborated upon. That technical concept is related (rooted, if you will) in the commonsense concept of truth, but it is more precise and diverse. But that’s just the difference between technical and common language.

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  32. C,

    > This may just be a terminological disagreement, but I don't think *theories of truth* are at issue here, but rather *theories of knowledge* (or justified belief). <

    Both. As I said above, I think metaphysics (theories of truth) and epistemology (theory of knowledge) better go hand in hand.

    > The fact that a sentence can't be (or hasn't been) empirically/experimentally established doesn't entail that the sense in which it is "true" changes. <

    Correct, and your example works that way. But the holographic principle could be true in two distinct ways: it could be a mathematical truth (if the calculations have been done properly, which I’m sure they have) and/or a physical truth (if it describes the way the universe actually works). Baggott’s (reasonable) position is that at this moment to say that the principle is mathematically true is rather uncontroversial, but to say that it is scientifically true amounts to redefine what it means to do science — and not for the better.

    Mark,

    > Someone mentioned the binary tendencies of ordinary – and philosophical – thinking. <

    Someone was oversimplifying. In all the cases you mention there are several nuanced positions in between.

    > I don't deny that string theory has been over-hyped in the past, but I don't see any cause for seeing it as bad science. <

    I think the charge is that it isn’t science at all (because it makes no contact with empirical reality), and that it is a bad idea to attempt to pass it for science. Hence the title of Woit’s book: Not Even Wrong.

    > And just because string theorists haven't managed to make the hoped-for breakthroughs yet doesn't mean breakthroughs won't be made. <

    Of course, although we have been waiting since the ‘80s… Regardless, the point is that *if* and when the theory will make contact with the empirical *then* one can talk about it in terms of more or less good/bad science. But that moment hasn’t arrived, and may never arrive. (Indeed, if one takes seriously the contention of a landscape of 10^500 different versions of the theory, then it is *certain* that it will never be tested, not in the sense of being able to empirically discriminate among that many versions.)

    > I'm sure Massimo would agree that it has no bearing on the value or worth or beauty of the work in question <

    Certainly not the beauty. As for value and worth, it depends. Again, if we are talking science, so far the value has been way underwhelming, especially compared to the hype.

    jefscott,

    > Part of the problem is that the concept of “truth” as a linguistic tool puts us in the difficult, if not impossible, position of making a binary distinction about something we are interested in <

    I’m not so sure. Philosophers have elaborated on degrees of truth, or truth-likeness, of theories, so the concept doesn’t have to be binary at all.

    > the reason that “usefulness” is a better concept than “truth” in describing what we often want to talk about is PRECISELY because it is more “unpackable” than the concept of truth <

    But the problem is that we know of a number of scientific theories (e.g., Newtonian mechanics, or even Ptolemy’s system) that are useful and yet very clearly not true.

    > By way of analogy think of the way that classical mechanics describes a continuous and unbroken gradient of possibly energy states – this makes sense as an intuitive experience of everyday life (like the velocity of a baseball), but it stops being a useful concept once we talk about quantum mechanics <

    That makes my point: classical mechanic is less true than quantum mechanics.

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  33. kczat,

    > the holographic principle is being horribly caricatured. The principle is just this: it is a bound on the number of quantum states that can exist in a given region of space-time, based on its area. How you get from there to reality being an illusion, I haven't a clue. <

    Well, since Baggott’s description refers to a number of verbatim quotes from the creators of the principle, you may want to take it up with them…

    > The principle makes claims about every space-time region in the universe with certain spacial properties. This has been checked for many examples, most much more mundane than black holes, and no contradictions have yet been found <

    You may be correct, but I think that Baggott’s issue is that the principle doesn’t make any *novel* empirical prediction. It is compatible with what we already know, yes, but so is superstring theory, in 10^500 different versions, of which only one can possibly describe our universe.

    > is a link between general relativity and quantum mechanics. Hence, it will tell us a great deal about what a theory of quantum gravity has to look like. <

    Precisely the (so far) unfulfilled promise of string theory, superstring theory, and M-theory.

    DM,

    > let me just mention that I don't much like the new commenting format. Was this a deliberate change? <

    Yes, I’m playing with different possibilities. Stay tuned.

    > it wouldn't imply the three dimensional world is an illusion, only that there are two different but ultimately equivalent ways to describe that world. <

    You may be right, but if that’s the case, what is the point, from the perspective of physics? The principle then simply becomes a different mathematical rendition of the world, with no impact on the empirical realm. I doubt that’s what the authors intended.

    > I think that fundamentally there is no difference between this type of reasoning and what Hawking and Susskind are doing. Their arguments are certainly true in a coherentist sense, and they are probably true in a correspondence sense. Just as with Socrates. <

    Sorry, I just think the two examples have very little relevance to each other, but I’m not sure how to further articulate the point, so I’ll leave it at that.

    > What I am saying is that I don't accept that the Holographic Principle is actually based on String Theory. <

    My understanding is that this is indeed incorrect. The principle is tightly linked to a duality (see one of the comments above) that emerges from string theory. Needless to say, Baggott’s objection is that this makes the principle even further remote from the empirical realm than string theory is.

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  34. Hi Massimo,

    I think kzcat is probably right. He seems to know what he is talking about and he is more confidently articulating what I was trying to express. Miller, the commenter you referred to who brought up "duality" is also under the impression that this was discovered in string theory but is not based in or dependent on string theory. It would be interesting if we could get anyone posting here who understands this stuff to back you up.

    >Well, since Baggott’s description refers to a number of verbatim quotes from the creators of the principle, you may want to take it up with them…<

    Those quotes may have been taken out of context or interpreted incorrectly by either you or Baggott. Again, I'm not asking you to take my word for it, but in the absence of any supporting voices here or online resources elsewhere, perhaps there might be something wrong with your representation of the physics.

    >You may be right, but if that’s the case, what is the point, from the perspective of physics? The principle then simply becomes a different mathematical rendition of the world, with no impact on the empirical realm. I doubt that’s what the authors intended.<

    This new way of representing information may prove to be more useful for solving certain kinds of problems. The very fact that these representations are equivalent also points the way to a solution of the Black Hole Information paradox. This discovery is therefore very interesting and does indeed have empirical implications.

    >Sorry, I just think the two examples have very little relevance to each other, but I’m not sure how to further articulate the point, so I’ll leave it at that<

    Fair enough. I think I can express my point in another way.

    You asked how could these hypotheses possibly be true in a correspondence sense. I think that some confusion is due to this wording of the question. Of course they can be true in a correspondence sense. The question you should have asked is how can we know them to be true.

    Obviously this knowledge would have to be justified in some way. One way to justify it would be to perform some sort of empirical test. But I think coherentist truth can also allow a justification, once you have sufficient evidence for the correspondence truth of the premises and confidence in your logic.

    If I want to figure out the area of a rectangle, I can multiply the breadth by the width and find an answer - but I have done so only by coherentist means. Your argument seems to be saying that we can only justify a belief in the correspondence truth of this result by directly measuring the area of the rectangle.

    Your skepticism could be vindicated - my measurements may be incorrect, or it may not be a perfect rectangle, or the surface might not be flat, all of which would skew the result. Nevertheless, the coherentist calculation can be trusted if these possibilities are accounted for. The coherentist account will only fail if there is something wrong with the premises.

    And the same is true for the predictions of theoretical physicists. For them to be incorrect on their most confident predictions, there would have to be something profound we are missing in our basic understanding of reality. Sure, that could be the case, but it is perhaps not very likely. Belief in the correspondence truth of their predictions is therefore justified, to a point at least.

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  35. "But the problem is that we know of a number of scientific theories (e.g., Newtonian mechanics, or even Ptolemy’s system) that are useful and yet very clearly not true."

    The problem with with the concept of truth is that it needs almost no manipulation to its definition to show that the Ptolemic model is actually true. That is, the Potelmic model is true because it "truly" shows, from our perspective, the way the stars and planets and moons move. But most of the time when we are talking about "truth" that's not what we really want to talk about, and it's because of this binary implication in the concept of truth that makes it a less meaningful term than we need.

    "That makes my point: classical mechanic is less true than quantum mechanics."

    Again, just think hard about the linguistics here. "less true" is the inevitable "unit" we are led to when we try to describe things in terms of truth, but it's such a murky and indefinite conceptualization of what we are talking about it just begs for a more meaningful term. Ultimately when you get down to it and try to ask the next logical question like," well, then what is a unit of "less truth"" you see that you are really asking about "usefulness" anyways. The ptolemic model is "less true" than other models precisely for the reason that it is less useful as it relates to other problems/models of cosmology and gravity (which has empirical and mathematical corridors). So in that sense we know that usefulness is a more fundamental description of what we are talking about, and truth is a conceptual description layered upon it. Which is why as a concept it can so easily fails at certain scales. And it's the reason people can talk about "truth" until their man (or lady) parts fall off and never get very far.

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  36. How does the holographic principle relate to the idea that to an outside observer, nothing ever actually falls into a black hole, everything should get all smooshed onto the surface of the event horizon since time dilation goes to infinity there?

    If some alien civilization perceived somehow it was in the holographic type of universe, would their Susskind pronounce the universe was actually an n+1 dimensional whatever?

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  37. On the last practically conclusive paragraph: would it not be simple enough to regard information as necessarily artificial, since it is interpretive, rather than naturally forceful (e.g., even computer programming or radio transmission requires an ultimately human source)? Whether information is physical or meta-physical would seem thereby easily answered, but not whether such information is objective or subjective, or real or instrumental. On the opposite side of skepticism, it seems natural that human intelligence would require skepticism within its cognizant development, but that some skepticism (e.g., “quantum theory”) would be both impractical and unnecessarily too strenuous to produce many conclusions. So, I ask, what practical applications does quantum theory present?

    Thank you for your blog, it's truly a good pleasure to read from you. Cheers!
    ~ Peter

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  38. @Massimo ... Again, we're probably closer than I first thought. Maybe differing 10 percent or so on where to split the bill on which theory of truth to give more credence?

    ==

    If the meaning of truth "should" change (and I'm not saying either yea or nay on that right now), is it not incumbent upon the person(s) involved with an issue of truth in a certain field to make some advance stipulations?

    (Tell that to Harris, too, in suggesting that he can also use the help of philosophy of language at times.)

    ===

    @ Paul M.: Well, I disagree that ethical concepts are pictures of nothing. They may be pictures of abstractions, but I'm not *that much* of a realist to think that abstractions are nothing.

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  39. Massimo

    >… the charge is that it isn't science at all ... <

    As I understand it, string theory is basically a set of mathematical frameworks (and associated intuitions) which has been applied (with mixed success) to various problems in theoretical physics. It is a part of the history of late 20th and early 21st century physics (and mathematics) and, even if hopes for it leading to a comprehensive "theory of everything" appear to be fading fast, it seems to be going a bit far to suggest that string theory is not science!

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  40. That the universe is information, or "every object and process in our universe, at the deepest level of physical existence, is a quantum data structure" ("it from "qubit") appears to be a pretty popular view.

    On the Possibility of Quantum Informational Structural Realism

    It reminds me of the concept of Computronium.

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  41. Outside the box of scientific uncertainty is the infinite universe of absolute. To see it is to simply be it, be true. =

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  42. You would think that if information *isn't* physical, this would have rather profound implications for 'physicalism', wouldn't it? Because if (as for instance Wheeler thought) information is 'metaphysically primitive' (i.e. can't be reduced to anything else) and is fundamental, then physicalism can't, ipso facto, offer a theory of the fundamental basis of reality.

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