String and M-theory: answering the critics

Mike Duff has a new preprint out, a contribution to the forthcoming Foundations of Physics special issue on “Forty Years of String Theory” entitled String and M-theory: answering the critics. Much of it is the usual case string theorists are trying to make these days, but it also includes vigorous ad hominem attacks on Lee Smolin and me (I’m described as having an “unerring gift for inaccuracy”, and we’re compared to people who campaign against vaccination “in the face of mainstream scientific opinion”). One section consists of a rather strange 3-page rant about Garrett Lisi’s work and the attention it has gotten, a topic that has just about nothing to do with string theory.

Duff explains that his motivation for answering the critics is that we have been successful on the public relations front, supposedly responsible for the British EPSRC “office rejecting” without peer review grant proposals on string theory. I know nothing of this, but I think it’s clear to everyone that the perception of string theory among physicists has changed, and not for the better, over the past decade. One dramatic way to see this is to notice that at this point, US physics departments have essentially stopped hiring string theorists for permanent appointments (i.e. at the tenure-track level).

String theorists have a problem not just with the public, but with their colleagues. The main reason for this is not Smolin or me, but the failure of the string theory research program. Duff’s take on whether the landscape is pseudo-science is that string theory can’t even tell whether there is a landscape, and he is “doubtful whether the kind of issues we are considering here will be resolved any time soon.” On the question of the time scale for possible progress, he invokes the two millennia it took to get from Democritus in 400 BC to quantum theory early last century. His list of greatest achievements of string theory in recent years has just two items: applications to fluid mechanics and his own work on entanglement in quantum information theory. Given this, it’s hard to see why he’s surprised the EPSRC is cutting back on support for string theory.

While Duff has detailed complaints about exactly what Smolin wrote in The Trouble With Physics, he mentions my book without saying anything about what is in it (one suspects his policy of how to deal with it is that of Clifford Johnson and some other string theorists: refuse to read it). He does have some specific complaints about material from my blog:

  • According to Duff:

    he [Woit] wrongly credits me with having told author Ian McEwan about the Bagger-Lambert-Gustavsson model in M-theory, which he then proceeds to criticise.

    This is based on a book review about Ian McEwan’s novel Solar, where I wrote about M-theory references in the book that “McEwan seems to have gotten this from Mike Duff, who is thanked in the acknowledgments”. Since Duff is an expert on these topics and the only particle theorist thanked, this was an obvious guess, worded as such. In this review I wasn’t criticising M-theory, just noting an interesting occurrence of it in popular culture. My only criticism was of McEwan, for the minor anachronism of a topic from 2007 showing up in a book set in 2000. In a segment from the novel that I quoted, one character is expressing opinions about M-theory research which you could call critical, but this material was written by the novelist, not by me (and I’m still wondering where McEwan would have gotten this from, other than from Duff).

  • In two cases, Duff claims that I misrepresented his words on the blog. Both are cases where I wrote the blog entry based on information from someone who had heard him talk, since I didn’t have access to his words themselves when I first wrote the blog entry. In general I try to be very careful about what I quote, making sure it is accurate and in context. In these cases, what was reported here was clearly labeled as someone else’s impression of his talk, and Duff has some reason to be annoyed at not being quoted accurately, although it wasn’t me doing it.

    The first case was a posting about the debate in 2007 between Duff and Smolin (see also Clifford Johnson’s blog, which includes comments from Smolin), where one attendee described the scene following Smolin’s talk as:

    Smolin sat down. Duff stood up. It got nasty.

    The trouble with physics, Duff began, is with people like Smolin.

    The transcript actually shows:

    Good evening everyone. The trouble with physics, Ladies and Gentlemen, is that there is not one Lee Smolin but two.

    followed by an extensive description of Smolin as deceptive and two-faced, saying completely different things at the debate and in his book. From the transcript, I’d describe the “Duff stood up. It got nasty” part as completely accurate, the “The trouble with physics, Duff began, is with people like Smolin” much less so.

  • The second case has to do with a posting about a recent BBC program on superluminal neutrinos, where Duff discussed string theory explanations for this. Based on two e-mails people had sent me who had watched the program, I wrote that it “evidently featured trademark hype from string theorist Mike Duff about how string theory could explain this.” The first commenter, who had also seen the program wrote in “I watched this tonight and can confirm that it did include stringy hype.” Duff complains that

    I said that, although superluminal travel is in principle possible in the “braneworld” picture of string theory, in my opinion this was NOT the explanation for the claims

    It still seems to me that going on a TV program to claim string theory as a possible explanation for this kind of experimental result can accurately be described as “hype”, even if, since no one believes the experimental result, you express the opinion that string theory isn’t the right explanation in this case.

  • Duff is much less interested in the virtues of accuracy when he describes my words. I guess I’ve joined Smolin on his list of targets because of what I’ve had to say on the blog (see here, here and here) concerning his publicity campaign claiming a “prediction of string theory” about qubits (recall that he thinks this is one of the two main advances in string theory of this decade). He claims that “falsifiability of string theory is the single issue of Peter Woit’s ‘single-issue protest group'”, and that my argument about the qubit business “may be summarised as (1)It’s wrong (2)It’s trivial (3)Mathematicians thought of it first.” One can read the postings and decide for oneself, but I’d summarise the argument quite differently: Duff has nothing that can possibly be described as a “prediction of string theory” and it’s misleading hype to issue press releases claiming otherwise. The experimentally testable “prediction” is that “four qubits can be entangled in 31 different ways”, but if experimentalists make measurements of four qubits that show something different, one can be sure that the headlines will not be “string theory shown to be wrong in a lab”.

    Duff’s article contains an appendix about this, in the form of a “FAQ”, where he explains that he approved the text of the press release headlined “Researchers discover how to conduct first test of ‘untestable’ string theory” which is misleading hype by any standard. Initially someone who was successfully misled in the Imperial media team added the subtitle “New study suggests researchers can now test the ‘theory of everything’”, which was later removed. Duff claims that Shelly Glashow, Edward Witten and Jim Gates told journalists that they didn’t agree with this because of the “theory of everything” subtitle, implying that otherwise they were fine with the “first test of ‘untestable’ string theory” business (except for Gates noting that in any case this is just supergravity, not string theory). It would be interesting to hear from the three of them if they’re really on-board with this “first test of ‘untestable’ string theory”.

    What Duff and some other string theorists don’t seem to understand is that this sort of “answering the critics” is exactly what has gone a long way to creating the situation at the EPSRC that he is worried about. Unfortunately it has damaged not just the credibility of string theory, but of mathematically sophisticated work on particle theory in general. According to Duff

    Just recently, in fact, EPSRC completely abolished its Mathematical Physics portfolio.

    Update: Matin Durrani at Physics World (also a target of Duff’s ire) has a blog entry about this here.

    Update: Lee Smolin sent me the following comments on the Duff article:

    Maybe it would help if I provide some context for the debate Mike Duff took part in with Nancy Cartwright and myself in London in 2007. The occasion for the debate was the publication of my book TTWP in the UK and the reason for the debate was that I had insisted that, as the point of the book was to explore the role of disagreement and competing research programs in science, the best way to illustrate it was to have a debate. String theory was discussed in the book as a case study illustrating the issues and so it seemed appropriate to have a debate with a string theorist. I also insisted that in each of these debates a philosopher of science would be included to highlight the fact that the main themes of the book were longstanding issues in philosophy of science, having to do with how consensus forms within a scientific community on issues on which there is initially wide disagreement.

    There were two such debates in the UK, the other was at Oxford with Philip Candelas and Simon Saunders. That went very well, as Philip gave a strong defence of string theory that stayed focused on the scientific issues.

    Duff’s construction of two me’s is, so far as I can tell, a debating tactic to avoid addressing the key issues my book raises. He starts with

    “Who can dispute that the ultimate goal of a scientific theory is to make experimentally testable predictions? Who will challenge the need to keep an open mind and listen to unorthodox views? Who can disagree with the assertion that our current understanding is only partial and that the ultimate truth has yet to be uncovered? What Lee Smolin said in the London debate [29] was so uncontroversial that, had I confined my response [11] to these remarks, the evening would have would have fizzled out in a bland exchange of truisms.”

    Indeed the constant theme of my book is the development of those “truisms.” What Duff does not explore is that in spite of the agreement there may be over these “truisms”, they have strong consequences for the evaluation of research programs in fundamental physics. Apparently we disagree about the implications for string theory. What Duff could have done is acknowledged these disagreements and explored the reasons for them. Instead he claims to attack my book, but it is striking that he does so, not by criticizing the text I actually wrote-but by attacking first the publicity blurb on the cover and then responses from journalists. As I have stated many times, the material on the cover was neither my text nor my choice and is more strongly worded than anything in the actual book. I hope it is obvious also that you cannot attack a book by pointing out inaccuracies in reviews.

    When he finally does get around to quoting from the book, he makes a few good points mixed in with distortions gotten by quoting out of context. Had he stuck to the good points he had we could have had a useful debate that would have shown the audience the role of disagreement among scientists faced with difficult questions. Had he done that, there would have been no need to construct a fiction of two me’s. I am happy to leave it to readers of my book to judge whether its text is or isn’t completely consistent with the “truisms” he asserts we agree about.

    There is one aspect of Duff’s rant which deserves correction, which is his attack on me related to Garrett Lisi. What Duff says is, “So when Lee Smolin described him [Lisi] as the next Einstein, the publicity juggernaut moved into overdrive”. There are several untruths in this short sentence.

    First, this refers to a Discover article of March 2008 which says, “With Smolin’s aid, DISCOVER has scoured the landscape and found six top candidates who show intriguing signs of that Einsteinian spark” of whom Lisi is one. This was, so far as I recall, based on a phone call with an editor at Discover following a piece I had written for Physics Today on the challenges faced by those who do high risk-high payoff research. I think anyone who looks up the full list of six will see that the editors were aiming to illustrate a wide range of approaches to fundamental research, of which Lisi is at one pole. And as they make clear-the choice of the list was theirs and not mine.

    Furthermore, the media attention on Lisi had begun and peaked already in November of 2007, sparked by a New Scientist article, following immediately the posting of his article on And while there was a very exaggerated media response-which I and others did our best to advise against-there was no “publicity juggernaut” ie no attempts by Lisi or anyone to seek publicity for him, no press releases, no publicist, no calls to journalists except to strongly advise the story was premature. I told everyone who asked not to write a story on Lisi because the preprint had just been uploaded and there had not been time for experts to evaluate it. Indeed, New Scientist had quoted me very much out of context, ignoring emails I sent them advising them not to write a story on Lisi’s paper before the experts could evaluate it. So the reality was the opposite of the impression created by Duff’s sentence.

    None of this is new, none of it is said for the first time. It is depressing to revisit these debates from five years ago. Most of us have moved on. At least I have, as readers of my next books, as well as the article I was invited to write for the same special issue, will, I hope, see.

    Update: The following is Garrett Lisi’s response to the Duff article. I should note that I’m not complaining about Duff’s listing of my titles. If you want to make up your mind who is right based on titles, Duff’s your man in this argument.

    Michael Duff’s article is full of deceptive half-truths. To attack the commentary on Lee’s book, while avoiding Lee’s actual arguments, is just one example of this fundamentally dishonest tactic. A similar example is his reference to Peter as “Computer Administrator and Senior Lecturer in Discipline,” as if Peter was not also a very knowledgable mathematical physicist. Duff then launches an attack on my work, once again focusing on a large volume of commentary by others rather than on my actual arguments. Also, Duff refers only to my first paper, saying it’s never been peer-reviewed and published, avoiding the fact that I’ve since published papers on the theory, including “An Explicit Embedding of Gravity and the Standard Model in E8.”

    Scouring Duff’s rhetoric, baseless statements, and ad hominem attacks in search of some factual argument supporting his attack on my work, I can find only this:

    “Nature (and the standard model of particle physics) has three chiral families of quarks and leptons. ‘Chiral’ means they distinguish between left and right, as they must to account for such asymmetry in the weak nuclear force. But as rigourously proved by Jacques Distler and Skip Garibaldi, Lisi’s construction permits only one non-chiral family.”

    This is, once again, a misleading half-truth, avoiding the fact that a chiral family of quarks and leptons can be part of a non-chiral representation space, as is the case in E8. I cannot credit Duff alone for this deception, as its source is Jacques Distler — a master of the half-truth — but I can blame Duff for supporting it.

    For anyone who actually cares about the state of E8 theory, I would recommend my recent papers. Apparently Duff considers the work sufficiently threatening to the string program that he needs to attack it in this dishonest manner. If string theory models are as twisted and misleading as the statements in Michael Duff’s paper, it’s no wonder they’re dying.

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    67 Responses to String and M-theory: answering the critics

    1. John Merryman says:

      Interesting comments on the nature of progress and skepticism. It seems, just like nature, we need to keep building out those large, unwieldy, unstable structures in order for them to collapse and see what hard little nuggets of content remain. On the other hand, maybe those large gaseous fields are every bit as natural as the little bits of mass into which they collapse. Lots of heat and some light are generated.

    2. Jon Lennox says:

      Anonyrat / Peter: The Wayback Machine archives of this site are pretty thorough (with the usual caveat that they run about six months behind).

      For long-term storage, that’s a single (organizational) point of failure, though.

    3. Chris Austin says:

      @ harryb,

      I was surprised and disappointed by that unfortunate quote from Ed Witten; perhaps he had his mind on something else at the time, like Paul Dirac in that wonderful interview that Peter linked to recently.

      Here’s a one-page article from Witten’s IAS website, where he does a better job of explaining why superstring theory is interesting.

    4. Peter Woit says:

      I’ve added as an update a response from Garrett Lisi to Duff’s article.

    5. Dan Burgess says:

      Apparently even Google’s a critic. A search for ‘Not Even Wrong’ brings up this result for Google books:
      Not even wrong: the failure of … – Peter Woit

      That’s tough 🙂

    6. harryb says:

      @Chris Austin

      Thanks for the link – agree it is a lot more accessible / humble on string theory’s strengths / limitations. Leaves little room for any other line of thought though, with the suggestion that should any emerge, they will be reshaped as just a yet undiscovered element of string theory. But clear article.

      I’m reminded again of Feynman’s comment when asked if he had to leave one sentence behind to aid other civilisations: he noted it would need to be “Everything is made of atoms”.

      I guess Witten would rejoin “Everything is made of strings”. Would this help or hinder these hapless civilisations I wonder.

    7. Hendrik says:

      Maybe not too far off-topic, is a piece by John Horgan in Scientific American, how in physics sometimes cranks are indistinguishable from experts. Based on a book by Margaret Wertheim, link is here. Of course strings are mentioned.

    8. Peter Woit says:


      I ordered a copy of the book a few days ago, should arrive tomorrow, then review to follow shortly.

    9. Pingback: Weekly Picks « — the Blog

    10. Shantanu says:

      Peter or anyone else, does anyone know if smolin and Duff actually went for a drink or dinner after the debate?

    11. Dan says:

      Dear Peter,

      even though, I might agree with what you say in some points of your article. The response you published from Lisi really needs a comment. Lisi makes comments about half-truths when he’s the first one using them.

      Lisi mentions the fact that his peer reviewed paper (in a conference proceedings) wasn’t mentioned by Duff, but Lisi fails to say that this paper doesn’t say that he succeeds in the unifications, it just provides an embedding for the “one family” standard model, something already present in Distler’s paper.

      About it, also, Lisi wants to make the readers thing that it’s possible to include a chiral generation in a non-chiral representation. This is almost outrageous. Everybody knows that this sentence either makes no sense, or it states the obvious. Distler and Garibaldi’s point isn’t that the one generation isn’t possible, they say that “because of the presence of an antigeneration, that generation will never be chiral”. But, most importantly, they prove that three generations are impossible to get out of E8. And Lisi doesn’t have any answer to this. Of course.

      About Lisi’s work being threatening to string theory, let’s just have a laugh. What Duff is clearly upset at certainly isn’t Lisi’s theory, he’s upset at who still doesn’t clearly state that Lisi’s was an interesting attempt, but the theory has so many holes and it’s so incomplete that there isn’t really a reason to give him so much resonance in the news. And when they prove his mistakes (he wrote several “wrong” statements, both physically and mathematically), then the press forgets and they don’t give reasonable updates.

    12. Peter Woit says:


      About Lisi vs. Distler/Garibaldi, I think both sides have had a chance to make their case, people can make up their own minds about this. The bottom line I think is that there are problems with Garrett’s unification proposal, just like there are problems with all unification proposals out there. He’s pursuing his and may someday overcome them, others may find some inspiration in what he has done for their own ideas. If you don’t think his proposal can go anywhere, work on something else. It’s not like there’s a problem with the field being dominated by work on his ideas, crowding out others.

      As to the complaint from string theorists that Garrett got too much positive media attention, and Duff’s belief that this is such a big problem for string theory that he had to devote several pages to it of his short article defending string theory, try the following thought experiment. Imagine that Garrett’s ideas fit into the string theory program, that he had some unification proposal he was pushing involving string theory (with similar problems to all the string theory unification proposals). The media would have found it just as attractive to write about the surfing outsider physicist with his revolutionary ideas about how to make string theory work. Do you really think Distler or Duff would have mustered the same outrage and gone on an anti-Lisi campaign? Would Duff have devoted pages of his article to the Lisi problem?

      What’s funny about both Duff and Distler is that they clearly have no problem with outrageous, dishonest media hype. They have both had their universities issue absurd press releases about their own work supposedly “testing string theory”, when they had nothing remotely approaching such a thing, see


      It’s only when a string theory critic gets media attention that they get completely bent out of shape.

    13. Dan says:

      Peter, thanks for your answer.

      I think you missed my point. Lisi “himself” says clearly that his theory isn’t currently able to reproduce the standard model, with one, two or three generations. He has no particle masses and doesn’t have the correct quantum numbers. This is clear to everybody who understands the physics. But Lisi’s answer here and in popular magazine is deceptive because he doesn’t always present this statement clearly.

      There is a big different between the Pati Salam model, say, or other unifications models that are not complete, but that can at least explain the standard model, and Lisi’s model, that cannot even explain why the electron has a different mass than a muon. Or even if he can actually have a muon (second generation problem).

      That is a huge incompleteness, much much bigger than not being able to prove, for example, whether or not N=8 supergravity is finite.

      In general, forgetting about string theorists, there isn’t a hate towards E8, which is in fact used in many fields. The annoyance is towards some interviews or presentation of facts, that don’t say clearly that in Lisi’s theory: still we don’t know how to actually get this fermionic degrees of freedom (the unconventional BRST isn’t ever defined), still we don’t have a way to get chiral fermions in the one generation case (there is only a comment about it), still there is no way to get the three generations (not a real word about it, that says something mathematically meaningful), still we don’t have a proper symmetry breaking mechanism, still we don’t know if really the Coleman-Mandula theorem is valid or not in those limits, still we don’t know why it would be a finite theory… And I could keep going. Of course everybody is welcome to work on the theory they want. And the good thing about nature is that it doesn’t care about what theory we like. Eventually the right theory will become evident. What matters though, is to be honest with the readers, especially the ones who can’t understand most things we are saying. And to them we owe the truth, which is that Lisi’s model is not more wrong or less wrong than a million other models, but also that it is way way far from being a complete theory, given that it doesn’t even reproduce all the known results of the standard model, which most other “good” attempts to theories of everything instead can reproduce. This difference is important.

      The other point that I was making wasn’t supportive of Distler, Duff or Motl or anyone else. I was just saying that Duff was upset because what I said above isn’t stated clearly enough. And the press makes it look like Lisi’s theory is as probably and as developed as lots of actually “working” theories (in the sense of at least reproducing known results and producing some predictions). Which is obviously not the case. Duff certainly isn’t upset or scared that Lisi’s theory will be creating problems to string theory, certainly not at this premature definition of the theory, does is just slightly more than some numerological correspondance between Lie groups and quantum numbers.

      Think of a theory like the one that Nima Arkani-Hamed is working on. Do you think it is as developed as Lisi’s. Less worth? More worth? Do they have the same media attention? Do they deserve that compared to each other?

      I’m not even saying anything bad about Lisi or his research. I’m just saying that the theory is in such a preliminary state that calling it theory of everything is almost a joke. Maybe, an work in progress, stil incomplete, attempt towards a theory of everything could have been better. Especially when people present it to the main public that isn’t capable of distinguishing between theories.

    14. Peter Woit says:


      I just disagree with you about why Duff is upset. He has shown conclusively that he has no problem with misleading hype appearing in the media or making untrue statements himself when it’s part of a campaign that aligns with his interests. The idea that his problem with Lisi is just that he’s offended by inaccuracy in the media is not plausible.

    15. Dan says:

      OK, I understand your point of view. But again, I wasn’t supporting Duff’s point. I was just saying that the literal interpretation was about that. Then everybody is free to have their own interpretations. But it was misleading of Lisi to present his words in a deceptive way and changing the literal meaning of them. Which is always the problem with every statement that Lisi makes. He rarely talks any physics or math but very often gives deceptive and misleading answers. That’s all.

      And even if Duff is wrong, or hypocritical and all that. What the media do with Lisi isn’t something to be proud of. It damages good physics. Maybe also Duff does, but it’s not with one bad thing that we cancel another bad thing.

      Thanks for offering this space of confrontation.

    16. Peter Woit says:


      My perception is different. Lisi’s public claims about his ideas seem to have about the average accuracy level you expect from someone enthusiastic about his own research. On the scale of the Distler and Duff press releases, not to mention the average popular book about string theory, he’s a stickler for accuracy. And, while the damage done by string theory hype to particle theory is huge and on-going, I just don’t see any significant damage from the media Lisi coverage.

      I’m not sure what work of Arkani-Hamed’s you’re referring to, and quite possibly I don’t know what he’s up to most recently. But whatever it is, I’m sure it will get quite a lot of attention from other theorists, and media attention if it pans out. If he quits his job at the IAS, moves to Hawaii and takes up surfing, he’ll do much better on the media front.

    17. Dan says:

      Ok, let’s ignore for a second string theory. I believe myself that it has made its damages. I don’t even like string theory, and for a while we all know all the jobs where there. Similar thing with supersymmetry. We aren’t finding it, and still we will have to deal with some fine tuning problems to solve if the Higgs is confirmed at 125 GeV. Also, is it really a Higgs? Is it elementary? Is it composite? How does it couples, in case, with gravity and so on… all questions to answer. Fortunately at least in particle physics we will be busy enough with this.

      But about Lisi, allow me to strongly disagree. I studied very carefully both Distler’s paper and all Lisi’s papers. And even if it’s true that he’s very excited about his theory it seems to me that he’s not even trying to have progress in it, just to defend it for the status he’s got in the media.

      What did Lisi really publish about his E8 stuff after the first paper? His paper with the explicit matrix representation doesn’t add anything to the initial structure. The result was even not only compatible, but in agreement with Distler and Garibaldi’s paper. His paper with Smolin and Speziale is barely related to the unification part but there is no E8 and the fermions (his main innovation in the other theory) are treated in a completely different way. Has he published any mathematical work on the unconventional BRST theory that he said he wants to use? Has he published any results about whether or not he’s safe from the extensions of Coleman-Mandula theorem? Has he found any way to get rid of the non-chirality and at least have a one generation standard model? Has he said anything specific about how he wants to recover the three generations out of fields with the wrong quantum numbers? Has he given any important math about this stuff in the last few years? Has he studied whether or not his theory is anomaly free, finite, renormalizable… etc? The paper with Smolin and Speziale certainly is not exhaustive about the topic.

      So, at the end, why does he give lots of interviews saying that Distler and Garibaldi made unnecessary assumptions in proving his theory wrong, but never actually says why those assumptions are wrong, what they are, and how he thinks of actually progress?

      To me this doesn’t seem a very accurate. He seems, although, very lucid about responding to these questions without really giving an answer. So we, physicists, know that he gave no answer, while the general audience believes he gave a valid answer. I don’t find this very encouraging…


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