String Theory and Philosophy

From Sean Carroll’s weblog I see that he’s in Austin now for a session at a meeting of the Philosophy of Science Association. Philosophers of science seem to actually write up their talks in advance, and many of the talks for this meeting are already available online. Poking around on their website with papers from earlier conferences, I ran into one on Scientific Realism and String Theory by Richard Dawid.

Dawid appears to have swallowed the hype about string theory hook, line and sinker. He believes that string theory exhibits a new paradigm of how to do physics, one where the idea of being able to calculate anything about the real world and compare it to observations is passe. All that matters now is “theoretical uniqueness”, that one’s theory is the only possible one. He doesn’t seem to notice that there’s something kind of funny about people claiming that they have a wondrous unique theory, but don’t know quite what it is and can’t calculate anything about the real world with it. The S-matrix theorists of the 60s also promoted the idea that they had a wondrous unique theory, but didn’t know quite what it was. Probably one can dig up philosophy of science articles from that period about how a whole new paradigm of how to do science was required.

Dawid also seems to believe that the dualities of M-theory imply the “dissolution of ontology”, that “the ontological object has simply vanished”. In reality, what has vanished is not the ontological object, but the theory.

Over at Robert Helling’s web-site you can read an example of the latest philosophical excuses about why string theory now can’t predict anything, together with implausible wishful thinking about how this might change since “It’s just at this stage we are not yet powerful enough to make these kinds of predictions”.

For the life of me I can’t figure out why smart physicists and philosophers can’t see the obvious fact that is staring them in the face. You don’t need a new paradigm of how to do science, the old one works just fine. If you have a conjectural theoretical scientific idea, there are two ways in which it can turn out to be wrong. Either it predicts something that disagrees with experiment, or it is so vacuous that it predicts nothing. The evidence is now overwhelming that, if string theory is consistent at all, it is wrong for the second reason.

Update: Dawid actually has a whole fancy web-site about Realism and String Theory. He also has a newer paper on Undetermination and Theory Succession from a String Theoretical Perspective.

The PhilSci archive does have another paper about string theory, one by Reiner Hedrich entitled Superstring Theory and Empirical Testability. Hedrich is much less credulous than Dawid, noting about superstring theory “above all, it has fundamental problems with empirical testability – problems that make questionalbe its status as a physical theory at all.”

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19 Responses to String Theory and Philosophy

  1. plato says:

    Arun,

    As noted earlier in Peter’s blog, there are recent mathematical advances which required concentrated work for several years of silence for the authors.

    There is no doubt in my mind the contemplative thinking asks that we recognize the essence of any equation, and a lot of times. The mind clicks a notch, when sitting by a stream(ask witten), and the mind had disassociated itself, from such efforts.

    There is a always a incubative time for consideration, as you quote saids. I thought, all mathematicians had good focus?

  2. Arun says:

    Are there reasons other than the overselling of string theory that the situation hold that Peter describes?

    For instance, perhaps string theory presents research problems that are more likely to reach fruition in one post-doc term than other areas?

    As noted earlier in Peter’s blog, there are recent mathematical advances which required concentrated work for several years of silence for the authors. Are there sociological factors operating in physics that preclude the kind of work that might be needed for such breakthroughs?

  3. Thomas Larsson says:

    Steve M.,

    Peter is of course completely capable of answering for himself, and has already done so. My perspective is somewhat different, in that I have a well-developed suggestion for the missing mathematical structure.

    Let’s also assume absence of any new experimental guidance, then what alternative mathematical structures or approaches in our opinion (ie non string theory) would have enabled a viable leap (or even step) beyond the SM or GR? I assume you would approve of deeper investigation into the mathematical underpinnings of the SM like gauge fields/YM and Dirac operators, but people have looked (are looking) at this anyway surely?

    I have looked one particular mathematical underpinning of the SM and GR since 1987, but despite rather remarkable progress the physics community has been completely uninterested. From this I have concluded that people who already know the correct Theory of Everything have simply no interest in learning about new mathematics, not in the 80s and not now. Mathematicians have in my experience always been much more open-minded, perhaps because everything that I have done has also been worked upon by some mathematicians because of its intrinsic mathematical interest.

    More precisely, I’m talking about the quantum representation theory of the correct constraint algebras of GR and the SM. The constraint algebra (in covariant formulations) of GR is the group of 4-diffeomorphisms, and the constraint algebra of the SM is the group of gauge transformations based on SU(3)xSU(2)xU(1). Upon quantization these algebras acquire quantum correction, making them into higher-dimensional analogues of the Virasoro and affine Kac-Moody algebras. That such algebras exist, and that they have an interesting representation theory is by itself some kind of mathematical success.

    This goes beyond field theory, because a 4D Virasoro algebra is a diffeomorphism anomaly in 4D, something which can not exist within field theory. Nevertheless, there are no assumptions about new physics here. 4-diffeomorphisms and SU(3)xSU(2)xU(1) gauge transformations are simply the correct constraints of GR+SM. So one reason why people have failed to go beyond GR+SM might be that there isn’t anything there; at least there are no conclusive experimental hints. There are some well-known mathematical problems, e.g. that GR and QM are inconsistent and that the SM is somewhat ugly (although by no means as ugly as string theory), but this may well be explained by the fact that people have missed the existence of the relevant anomalies.

    In the absence of experimental guidance in 25 years now surely all possible alternatives are just wishful thinking too and can’t make any predictions either? Everything else that has ever tried to go beyond the SM and GR has run into their own technical brick walls too so you can’t really just single out string theory esp when it was the most promising.

    I don’t think that loop quantum gravity is particularly promising neither. However, when evaluating the promise of an approach it is not fair only to judge the physical achievements (string theory: 0, LQG: 0, me: 0), without taking into account the amount of time and funding invested in it. Public spenders must expect public scrutiny, and big public spenders must expect more public scrutiny than small ones. If the funding to LQG were raised to string theory levels, e.g. by redistributing funding from string theory, and LQG didn’t make any spectacular progress after a decade neither, then it would be fair to criticize it too.

    Another intrinsic aspect of string theory is the consistent overselling for the past 20 years. I always felt dubious about a theory without experimental support, but what convinced me that string theory is not only wrong but detrimental to science was a Physics Today article by Gordon Kane in 1997, entitled “String theory is not only testable, but super-testable”. The title vividly illustrates the complete discrepancy between the hype and the actual achievements. In this respect, string theory is totally unique in serious science, and can only be compared to pseudo-science.

  4. Peter says:

    Hi Steve,

    A couple comments. You’re right that my own point of view is that, given the lack of experimental guidance, the most promising thing for theorists to do is to try and learn more about the mathematical structures used in the standard model and see if new and better ways of understanding them can be found. There seem to me to be quite a few things of this kind to investigate, but I can tell you from personal experience that if you try and talk to most theorists about these issues, they’re really not interested. The attitude has become very widespread that the only possible mathematically sophisticated approach to particle theory is string theory, and that anyone who thinks otherwise is just too stupid to be a string theorist. Throughout the late eighties and into the early nineties, besides doing string theory, Witten came up with a lot of new ideas about gauge theories, but for the last ten years or so he seems to have decided to devote his full energies to string theory.

    I don’t think there’s only one thing people should be working on. In the absence of any particularly promising idea, which is where we are now, they should be trying out a wide range of different things. But there needs to be a much more honest process of recognizing when ideas don’t work and moving on to try something else. What’s completely dysfunctional about the field is the way it continues to be dominated by the idea of unifying the SM and gravity in an 11d M-theory of some kind, long after it should be clear this can’t work. It would have been unreasonable to demand predictions from string theory during the first few years that people were seriously looking into it, but twenty years later, the fact that it can’t produce a single prediction of any kind should count very heavily. String theorists should be honest about how bad the situation is, and stop heavily hyping and promoting the theory unless they can make some real progress with it.

    The main question facing the field seems to me to be that of how to encourage more people to try different things, and not just stick to one failed idea because it is what every one else is doing.

  5. Steve M says:

    Peter, I am curious about something. Let’s suppose we could turn the clock back 20 years to 1984 and let’s imagine that Green and Schwarz never did their famous Colorado calculation. String theory remains a backwater of physics in the 80s pursued by only a few diehards. So the question is: how would you have liked physics to have evolved–if you had had your way–to the present day, and would the situation really be any better than it is now? Or perhaps even worse? Let’s also assume absence of any new experimental guidance, then what alternative mathematical structures or approaches in our opinion (ie non string theory) would have enabled a viable leap (or even step) beyond the SM or GR? I assume you would approve of deeper investigation into the mathematical underpinnings of the SM like gauge fields/YM and Dirac operators, but people have looked (are looking) at this anyway surely? In the absence of experimental guidance in 25 years now surely all possible alternatives are just wishful thinking too and can’t make any predictions either? Everything else that has ever tried to go beyond the SM and GR has run into their own technical brick walls too so you can’t really just single out string theory esp when it was the most promising.

  6. plato says:

    DRL,

    I do not want to defer on recognizing your enthusiam either:)

    The increasing complexity, of what one might reveal of the cosmo, with a microcosmic view, had me consider how either the string theorist or the LQGist might interpret, that same cosmos. Gamma detection is one view right.:)

    There are obvious attempts to interpret quantum gravity. I was looking for how they might view the picture supplied in my previous post.

    If it is becoming increasing complex , the basis of their determnations would have to have a foundation to begin with, right?

    Mathematically, how could two views of picture supplied in previous post, be so different, and are they?

    As I stand, under the arch of reason, I am asking about that one thing. City Slickers, was very interesting from my historical perspective:)

  7. Anonymous says:

    Lubos,

    String theory, once it’s understood completely, cannot really be an approximation of anything deeper – it follows from its basic mathematical features.

    Can you explain this in more detail for a layman?
    (layman = math grad student, in this case)

  8. Lubo Motl says:

    Hi,

    I just want to say that I’ve seen your replies, and I find it inappropriate to answer this kind of feedback.

    All the best
    Lubo

  9. Chris Oakley says:

    String theory, once it’s understood completely, cannot really be an approximation of anything deeper – it follows from its basic mathematical features. There were many complicated historical coincidences that have led up to this point – namely string theory – but once we know that it’s a fact, there is some sense in which it could have been derived without explicit data from experiments, by “pure thought” much like many ancient philosophers were dreaming.

    I am going to go into suspended animation for a few decades. Could someone please revive me when Harvard physics professors start doing science again?

  10. Thomas Larsson says:

    But this feels worse, as it is based on what is being peddled by very smart and established people. Someone once told me that in the 80s David Gross predicted that string theorists would be able to predict the quark mass matrix within a decade. It is safe to say that that day will never come.

    Stephen Weinberg was here in Stockholm in December 1984, attending the Rubbia-van Meer Nobel party. At a colloqium he predicted that some smart young string theorist would win the Nobel Prize in 1991. Well, that prediction was at least falsifyable.

  11. Chris W. says:

    This old post by Michael Nielsen has some relevance to this discussion. (Don’t ignore the comments.)

    So does this well-known commentary by Albert Einstein.

  12. Anonymous says:

    “What sort of scenario do you have in mind? How could string theory be proved irrelevant?”

    Bon Motl believes string theory follows rigorously from the existence of God. So, if you can just disprove the existence of God, then even he will admit string theory is irrelevent.

  13. Chris W. says:

    Of course that all these conclusions would break down in the (unlikely) scenario that string theory will eventually be proved irrelevant.

    What sort of scenario do you have in mind? How could string theory be proved irrelevant? I can’t imagine what a “proof” of irrelevance is supposed to mean here. On the other hand, I can imagine how the majority of theoretical physicists might lose interest in string theory’s continued development, even in the absence of such a “proof”.

    And, while I’m at it, how would we know that string theory is a “fact”? We don’t know that any scientific theory is a fact. Theories may successfully account for facts, but they are never known to be facts themselves. That they have achieved some empirical success can certainly be a fact; indeed, these successes are among the more important facts that we hope to explain with subsequent theories.

    Of course, if a theory has never achieved any empirical success, or at least no unique empirical success, it is more likely* to be regarded as irrelevant, simply because it offers nothing that calls for a explanation.

    (*  Physical theories often retain some relevance as sources of ideas for building new theories, but in this respect they share the stage with many ideas from mathematics, philosophy, and even engineering.)

  14. D R Lunsford says:

    Plato,

    While I admire your enthusiasm, you have absolutely no idea about what is going on in physics. You should keep that in mind before posting.

    -drl

  15. D R Lunsford says:

    My feelings about philosophers are usually negative, but this guy was able to capture some important philosophical differences between string theory and previous pictures how to do science that should undoubtedly affect the way how philosophers think about science and its developments.

    And this is what I specifically detest about you folks – as if you, who have predicted nothing, and accomplished nothing, and DO nothing other than produce hot stupid uninteresting AIR, have the right to stand in judgment on the methods of Newton, Einstein, Maxwell, Faraday, Hertz, Kelvin…

    You in particular, Motl, have never written a scientific word worth reading, notwithstanding your “lofty” position. Your bombast and bluster are nothing but a cover for your empty sophist’s self-indulgent house of cards. You will never accomplish anything in science – your very presence is an affront to reason.

    You toss around the word “old fashioned” like a radical’s gas cocktail thrown through the window, a crazy Bolshevik on a mission from your “God”. Save me from the “good” people.

  16. plato says:

    Maybe people just do not like dealing with the complexity of the issues?

    We all like solid things, we just don’t know how they got that way from a earlier time?

    As a outsider, it is not to hard to maintain a view of the arguements that are presented when theoretical minds engage themselves.

    Maybe it as easy as saying that the following picture, can be taken one of two ways? Are The extremities of these theoretical positions, presenting themselves this way?

    I thought of putting the old woman versus beautiful woman picture, that changes when perspective is changed. But the picture choosen, should do.

  17. Lubos Motl says:

    My feelings about philosophers are usually negative, but this guy was able to capture some important philosophical differences between string theory and previous pictures how to do science that should undoubtedly affect the way how philosophers think about science and its developments.

    Of course that all these conclusions would break down in the (unlikely) scenario that string theory will eventually be proved irrelevant. However, if it’s relevant, the various standard old-fashioned ideas must be revisited. Every previous theory was an approximation of a better theory. String theory, once it’s understood completely, cannot really be an approximation of anything deeper – it follows from its basic mathematical features. There were many complicated historical coincidences that have led up to this point – namely string theory – but once we know that it’s a fact, there is some sense in which it could have been derived without explicit data from experiments, by “pure thought” much like many ancient philosophers were dreaming.

    Of course, these statements are just “in principle” because – first of all – history was very different and observations were totally essentially for us to move in essentially the right direction and – second of all – we still don’t know exactly how to complete string theory in such a way that the true quantities in the Universe can be calculated with the desirable precision.

    I am not gonna comment on Peter’s conjectures about what’s the reason why string theory “is wrong” because I think that these comments of Peter are stupidities that simply don’t deserve my time right now.

  18. BEB says:

    Well said, Peter.

    I think I am seeing another example of the over-selling that will ultimately backfire. The previous one being some of the things said in support for the SSC (that it could lead to cure for cancer!). I too wanted the SSC, but I wanted us physicists to be honest about it.

    But this feels worse, as it is based on what is being peddled by very smart and established people. Someone once told me that in the 80s David Gross predicted that string theorists would be able to predict the quark mass matrix within a decade. It is safe to say that that day will never come.

    Or maybe the problem is me; I do not believe strongly enough in the “rapture” from “faith-based” physics;)

    BEB

  19. D R Lunsford says:

    The opening paragraph of that Dawid opus made me laugh out loud. What a pile of garbage. I can’t believe people get paid to make up this tripe.

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