The Scientific Attitude

Just when I thought I was done for now with the “falsifiability” business, in our local book store I found a new book, The Scientific Attitude: Defending Science from Denial, Fraud and Pseudoscience, by Lee McIntyre. This won’t be a review of the whole book, much of which is concerned with what to do about the serious problem of the role of science in our increasingly post-truth society. I’ll just address the few pages of the book that deal with string theory, in which a quote from me appears in a misleading way.

The problem here is almost exactly the same as the problem with the Symmetry article discussed in the last posting. Both authors believe that string theory is a conventionally predictive theory, one with predictions that just happen to be hard to test. According to them, critics of string theory just don’t understand that there can be value in a theory which is testable in principle, even if a practical test is far away. Unlike the Symmetry piece, McIntyre at least names critics and links to their words, writing:

If one reads these kinds of criticisms closely one finds careful phrasing that string theory “makes no predictions about physical phenomena at experimentally accessible energies” and that “at the moment string theory cannot be falsified by any conceivable result.”23 But these are weasel words, born of scientists who are not used to taking seriously the distinction between saying that a theory is “currently” testable versus whether it is “in principle” testable. The practical limitations may be all but insurmountable, but philosophical distinctions like demarcation live in the difference.

The quoted words are mine, with footnote 23 referring to my 2002 article in American Scientist. Of course I was and am well aware of the distinction between testable “in principle” and “currently”. Bizarrely, the author has chosen to edit out from what I wrote the sentence that precisely addresses the issue I’m supposedly weaseling on. Here’s the full quote:

String theory not only makes no predictions about physical phenomena at experimentally accessible energies, it makes no precise predictions whatsoever. Even if someone were to figure out tomorrow how to build an accelerator capable of reaching the astronomically high energies at which particles are no longer supposed to appear as points, string theorists would be able to do no better than give qualitative guesses about what such a machine might show. At the moment string theory cannot be falsified by any conceivable experimental result.

As the deleted language make clear, by “any conceivable experimental result” I was making a claim about “in principle”, not “currently”. Furthermore, near the beginning of the article I explain the problem of principle:

First, string theory predicts that the world has ten space-time dimensions, in serious disagreement with the evidence of one’s senses. Matching string theory with reality requires that one postulate six unobserved spatial dimensions of very small size wrapped up in one way or another. All of the predictions of the theory depend on how you do this, but there are an infinite number of possible choices, and no one has any idea how to determine which is correct.

This article started out as an early 2001 arXiv posting and was published in early 2002, about a year before the now famous KKLT claim to have a string theory model with fully stabilized moduli. Back then, the problem I was pointing to was the basic one that, to have a self-consistent string theory model that you can confront, in principle, with experiment, you need to solve the problem of “moduli stabilization”. 6d compactifications come in families with a lot of parameters (the “moduli”) governing their size and shape, and the physics depends crucially on those parameters. You need to somehow give the moduli dynamics, and get a ground state with a correct fine-tuned vacuum energy.

KKLT claimed they could do this, but with an exponentially large “landscape” of solutions that removes the ability to get well-defined predictions from the theory. Their construction is so complicated, and non-perturbative string theory so poorly understood, that it remains controversial to this day whether these are really solutions to whatever the conjectural well-defined version of string theory might be. This is what the current “Swampland” argument is about.

I’ve put together a FAQ entry answering the Doesn’t string theory make predictions at very high energy? question. What causes all the confusion here is the common claim from string theorists that “string theory is testable at high energy”. If you ask them to tell you what the “test” is, they tell you about one of the characteristic features of the perturbative superstring (Veneziano amplitude, Regge trajectories, 10 space-time dimensions). What they are really saying is “if we did experiments at a high enough energy scale and saw one of these characteristic phenomena, we would have a successful test of string theory”, which is true enough, but not a specific, falsifiable prediction. What they are not telling you is that they are ignoring the compactification problem as well as that of not having a well-defined non-perturbative theory, and that many “string theory” models wouldn’t exhibit these characteristically perturbative features.

The main point of the new book seems to be to argue that a better way to characterize science is by whether those supposedly engaging in it are exhibiting the “scientific attitude”, which

can be summed up in a commitment to two principles:
(1) We care about empirical evidence.
(2) We are willing to change our theories in light of new evidence.

It seems to me there are lots of problems with this formulation. Sticking to the string theory question, undoubtedly string theorists “care about empirical evidence” and would like to have some. The problem though is they don’t have any, and don’t have any significant prospects for getting any. As for being willing to change one’s theories in light of new evidence, if there’s no new evidence, your willingness to change your theory won’t ever get tested.

My impression is that most people, this author included, are just fundamentally unwilling to believe that, given the high scientific profile of “string theory”, it could really have a serious problem of being inherently untestable. The technical issues involved are so formidable that non-experts don’t have any hope of understanding them. But there really is a serious problem here, and those who worry about the string theory fiasco damaging the credibility of science in a dangerously post-truth world are right to be worried.

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16 Responses to The Scientific Attitude

  1. Frank Wappler says:

    woit wrote (April 29, 2019):
    > […] a new book, »The Scientific Attitude: Defending Science from Denial, Fraud and Pseudoscience«, by Lee McIntyre
    > [… proposing] “scientific attitude”, which

    »can be summed up in a commitment to two principles:
    (1) We care about empirical evidence.
    (2) We are willing to change our theories in light of new evidence.«

    > It seems to me there are lots of problems with this formulation […]

    I agree that there are problems with McIntyre’s formulation; and I would call commitment to (merely) these two listed principles rather more specificly an “unstructured scientific attitude”, oder “pre-scientific attitude”.

    A “(structured, actual) scientific attitude” might be instead summed up in a commitment to three principles:

    (0) We care about notions (that go without saying), definitions, principles and methods (expressible in terms of those notions) which allow us to derive empirical evidence (from observations, as they become availabe to us).

    (1) We care about collecting observations from which to derive empirical evidence by methods that can be adhered to.

    (2) We are willing to change our expectations (about which observations and empirical evidence may still be forthcoming) in light of new evidence.

  2. Martin says:

    McIntyre writes “The practical limitations may be all but insurmountable, but philosophical distinctions like demarcation live in the difference”. The demarcation is about demarcating science from pseudo-science. This is a legal argument, which is based on the fact that critics of string theory naively argue that falsifiability would be the criterion. McIntyre loves this criticism. The real point is that there is no empirical evidence in support (!) of string theory. Scientists do not attempt to construct falsifiable, i.e. wrong, theories, they attempt to construct theories that work. Obviously, when a theory should work then it might turn out that it does not work, but that is not the objective. That is why McIntyre states “We care about empirical evidence”, deliberately without saying how the empirical evidence, if it could be obtained, should relate to the credibility of string theory. McIntyre argues like a lawyer – the critics cannot prove that string theory is not scientific. Therefore not guilty.

  3. Peter Woit says:

    All, I really don’t want to host a discussion of McIntyre’s ideas about the “scientific attitude” in general. I doubt many commenters have read the book, and I don’t intend to read more of it, so if it’s not about the string theory issue, please find somewhere else to discuss with the author.

    I’ve been having trouble figuring out why this author would quote me in such an unprofessional way. Taking a look at his other recent activities, I fear the answer is that he’s decided resistance to Trump justifies abandoning usual standards of academic writing, especially fairness to those you feel are on the other side. From this point of view, any criticism of prominent scientists puts one on the anti-science/Trump side, and given the current emergency all takedown tactics are fair. If only I could get McIntyre to read the collected works of Lubos Motl….

  4. vmarko says:


    Have you contacted the author to ask him about this misinterpretation of your words? How does he explain it? How about the book publisher, can you complain to them?

    Best, 🙂

  5. Peter Woit says:

    No, that seems like a waste of time. This author clearly knows nothing about string theory and cares less, it’s just minor grist for his “science is under threat” agenda. Would be best to ignore this, but I did want to set the record straight.

  6. I’m not at all a string theory fan and generally speaking I quite agree with the views expressed on this blog, so this is not a troll-question but a true-question. Reading Heisenberg, I clearly remember him saying that “Copernican theory doesn’t agree at all with observations since every day everyone observes the Sun rising, culminating and moving around the earth”. He says that in fact Copernican theory constrasts what is totally evident from observations to evidentiate a unitary and mathematical principle. My question is if this is in some kind different from string theory predicting that the world “has ten space-time dimensions, in serious disagreement with the evidence of one’s senses”. I repeat I’m really interested and is a true question, not trying to trolling anyone.

  7. Dave Miller says:


    You said, “I’ve been having trouble figuring out why this author would quote me in such an unprofessional way.” My guess is he took brief notes on stuff he thought might be useful and later forgot the larger context of those notes. The same effect can also occur from cutting-and-pasting different phrases in a manuscript as the author re-works the manuscript. Something like this seems to be what happened with various professionals (e.g., Doris Kearns Goodwin) who engaged in plagiarism but probably did not intend to.

    A point that needs to be more clearly addressed in these ongoing discussions is what is wrong scientifically with producing random, string-inspired phenomenological models that can be multiplied ad infinitum, after each particular model fails.

    I myself am not quite clear on how to formulate this succinctly, but, somehow, a scientist should be invested in a hypothesis in such a way that, if the hypothesis is falsified, it truly alters his thinking on the subject.

    Somehow, it is not fair to toss out a hypothesis, knowing that, if it is falsified, you will just toss out another slightly tweaked hypothesis, and so on when it is falsified, again and again and again. (We all know of a phenomenologist in the upper Midwest who has a tendency to do this!)

    I think the point may be that the goal of scientists is not simply to make and then confirm or disconfirm hypotheses but rather to seriously advance our knowledge of the universe by creating broad new theories that are significantly broader or more accurate than existing theories.

    Just churning out one hypothesis after another, never being fazed by their disconfirmation, fails to advance the cause of building a better, broader theory.

    All the best,


  8. Thomas Mattison says:

    Given an accelerator of astronomical energy, it seems likely that an experiment could falsify the hypothesis that the particles we know today are pointlike.

    That would not prove they are string-like. But strings would be a reasonable working hypothesis under the circumstances. Other hypotheses might be equally plausible in the absence of more data.

    You make a good case that the experimental program that would be required to which particular discrete compactification of string theory is correct would be daunting.

    Is there no hope of organizing the landscape into a pseudo-continuous space with a hierarchy of parameters? So if you knew approximate values for the most important few, you would be able to make some meaningful predictions? So a few experiments could be extrapolated into predictions for more experiments ?

  9. Peter Woit says:

    Daniele Corradetti,
    The point I was making was just that all our observations show four dimensions. If your theory says there are ten, you need to explain why we only see four. You need a theory of the dynamics of the other six dimensions, explaining why we don’t see them and how you could in principle see them. The main problem with string theory is that there is no convincing answer to this question.

    Dave Miller,
    I don’t see that problems with note taking are an explanation here. This author doesn’t appear to be a Doris Kearns Goodwin…

    Besides a few outliers like Gordon Kane, the problem with string theory is not that string theorists are making predictions, then changing them when they get falsified. The problem is that the framework they initially thought was predictive has turned out to be empty, with the partial theory they have incapable of predicting anything currently observable, and consistent with just about anything. The last hope was that the LHC would see something (e.g. SUSY) compatible with the string theory framework, but that hope is now dead.

    Thomas Mattison,
    Yes, if we could do experiments at the Planck scale we would likely be able to figure out what the quantum dynamics of space-time is, and in particular whether string theory had anything to do with it. My point is just that perturbative string theory is not capable of giving a consistent account of this (because of the compactification problem), so there’s no “string theory prediction” of what you would see.

    I actually don’t think our current understanding of string theory is capable of giving a well-defined, consistent description of what the possible “string vacua” are, and thus what the “landscape” is. One could speculate that it has nice properties allowing us to calculate with it, but there’s zero evidence for that.

  10. Lee Smolin says:

    Dear Daniele Corradetti,

    Your question is an excellent one. I am not an historian, but I have read a lot of the history relevant to the Newtonian revolution, and I have the impression that a key part of the argument was carried out by Galileo, who argued by a combination of real and thought experiments that the Earth could be moving around the sun, without the effects of that motion being observed. (Essentially, he argued for the relativity of inertial frames.) But the issue was subtle because the very same observations (the ball falling to the foot of the mast of the smoothly moving boat…) justified both the claim that we would feel the motion were the earth moving and the claim that we wouldn’t feel it, depending on whether one adopted the widely believed Aristotelean or the (yet to be) invented Newtonian dynamics. So Galileo’s arguments rested (correctly) on a yet to be developed dynamics, and Copernicus, who lacked even reference to Galileo’s intuitions, couldn’t possibly tell a consistent or convincing story.

    Meanwhile, Kepler went ahead and posited that the planets were influenced by a force from the Sun-which was a key step even if he did get details wrong. But what he really did that was crucial was to impose the conservation of angular momentum in the form of the equal area law, and show it was to first order in ellipticity equivalent to Ptolemey’s law of equants.

    So, after this overlong historical context, we can ask what a current day string theorist needs to do, to advance at least to the stage of Galileo and Kepler, and it is to invent some kind of principle that together with a good story based on a non-perturbative dynamics yet to be invented, that convinces us to ignore the evidence from the senses that the world has three stable spatial dimensions and not nine. And of course, this runs up against the problem of stablizing the moduli-a problem that Einstein knew about in the early 1920’s which caused him to abandon the Kaluza-Klein idea. And that leads to KKLT, the swampland…and here we are.

  11. Thomas Van Riet says:

    Dear Peter

    In your writings and those of Lee Smolin I see two main sources of criticism: 1) string theory is not sufficiently understood and 2) the Kaluza-Klein character of the theory anyhow makes it “unpredictable”. Concerning 1) I agree and I hope more people will put energy in developing the foundations. Concerning 2) there might be a misunderstanding here. Consider alternative theories, without extra dimensions. These theories will always be confronted with non-uniqueness: these alternative quantum gravity theories cannot be coupled just to the standard model and most likely many other gauge groups and couplings will be possible. I am guessing an infinite choice. This is where string theory helps allot. String theory geometrizes this freedom AND by doing so it has shown surprising constraints and patterns in these possible 4D theories. Our struggles with moduli stabilisation and SUSY breaking only arises because the theory is quite constraining.

    Thomas Van Riet

  12. Peter Woit says:

    Thomas Van Riet,
    I’ve just never seen any evidence that a string theory (or any other) geometrization in terms of extra space-time variables answers any significant question about the Standard Model. In the string theory case, instead of getting an explanation of features of the Standard Model, you have to put a huge amount of effort into (not clearly successfully…) trying to explain away why generic features (eg. SUSY, massless moduli fields) of these models are not observed. Fundamentally, you’re asking people to accept a poorly understood, very complicated framework as an improvement over the Standard Model, with zero positive evidence for it (and, at this point, no plausible prospects for getting any).

  13. Dear Lee Smolin,
    thank you for the insightful answer! I think is really a good point!

  14. Jim Given says:

    I applaud you for having introduced your readers to the research project methodology of science, a la Inre Lakatos, as explaining quite well the situation with string theory, i.e., as a degenerate research programme. Hearing about the “scientific attitude” as an attempt at a serious contribution to philosophy of science made me so sad, I just wanted to point out that the long essay, “The Methodology of Scientific Research Programmes” by Lakatos is available in paperback, is well worth reading carefully, and will clarify these situations in physics theory that you struggle with, far more than such current, rather unfortunate attempts to redefine science. The problem is not science. Rather, you and I (and our generation) are spoiled, having been trained in science in an era of extraordinarily rapid progress. One comes to have faith that the logically “inevitable” next step will turn out to be correct, and that rapid progress will continue. Alas. As Lakatos notes, the current generation of scientists does not turn away from long adopted but failed research programmes. Rather, they retire, and are replaced by a new generation; hopefully, one that reads your blog-

  15. You may appreciate this recent post on applications of the philosophy of science, and the associated paper. Quite a different subject matter, but perhaps this kind of Lakatosian analysis would help quantify some of the current state of affairs in fundamental physics? I don’t understand enough on a deep level to be certain, but I find the approach overall valuable. Lakatos definitely popularized, if not originated, the ideas of a “degenerate research programme.”

  16. Peter Woit says:

    Andrew Krause,

    Thanks. I know nothing about paleontology, but the Lakatos distinction between a “progressive” and “degenerative” research program does seem to me the most illuminating way of thinking about how to evaluate scientific research programs. I’ve never seen string theorists deal with this argument, they seem to carefully avoid it, since by any measure string theory fits quite well into the “degenerative” characterization, not well at all into “progressive”.

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