Structural realism, a way to be a scientific realist?

In the scientific realism vs instrumentalism debate, realism is the position that the elements of a scientific theory represent reality. So when general relativity talks about space warping, space really is warping. Instrumentalism, or anti-realism, is the stance that scientific theories are just prediction mechanisms, with no guarantee that they represent reality. Under instrumentalism, general relativity accurately predicts our observations as though space were warping, but whether it actually does or not can’t be determined.

Scientists, by and large, tend to be realists. It’s hard to find motivation to do the often boring and sometimes dangerous work involved in gathering scientific data, to dedicate years of your life to it, unless you see yourself in pursuit of truth. But as I noted in our last discussion on this, scientists tend to be realist about some theories and instrumentalist about others (although which is which depends on the scientist).

The argument in favor of instrumentalism is theory change. Many historical theories have been successful at making predictions, but eventually end up being replaced by a better theory, often with a radically different view of reality. The example I usually cite is Ptolemy’s model of the universe. For centuries it more or less accurately predicted naked eye astronomical observations, but we now know its model of a stationary Earth, with everything else in the universe revolving around it, is wrong. It eventually gave way to a Newtonian view of the universe, which in turn later had to give way to an Einsteinian view.

Realists often respond with the no-miracles argument. If scientific theories do not reflect reality to at least some approximation, then the argument is their ability to reliably make accurate predictions amounts to a miracle. Under this view, theories may change, but each one is getting us to a closer and closer approximation of the truth. This argument seems bolstered when we consider that often multiple theories are consistent and can be reconciled with each other.

As I’ve noted before, I tend to think this debate is misguided, because what we call “real” or “truth” are themselves just another predictive model. Still, while emotionally I’m a realist, I’ve long had intellectual sympathy with instrumentalism, although I prefer scientists to aim for realism and only settle for explicitly anti-real theories when there’s no choice. All in all, I’d prefer to be a realist, but wonder if there’s an intellectually honest way to get there.

Maybe there is. I recently came across the concept of structuralism or structural realism. The idea starts with the fact that what tends to survive theory change are the mathematical structures of the old theory. More specifically, these structures still tend to be useful in whatever domain the old theory was reliably accurate in. The prime example here is Newtonian physics, which gave way to general relativity and quantum physics in the early 20th century. But Newton’s mathematics remain so reliable for most situations that they’re what NASA uses for most space missions.

Under structural realism, it isn’t necessarily the concepts discussed in the theory descriptions that are real, but the structures and relations revealed in the mathematics. There may be multiple possible underlying realities from which these structures emerge, but the structures and relations appear to be what endures. If so, a philosophy of realism that focuses on the structures seems much more defendable than traditional realism.

There are multiple types of structural realism discussed in the articles linked to above, but they seem to fall into two broad groups: ESR (epistemic structural realism) and OSR (ontic structural realism). ESR says that all we can know about entities in the world, “the furniture of the world”, are their structural relations. It doesn’t rule out that there might be intrinsic non-structural and non-relational aspects of these entities, just that we can know anything about them.

OSR on the other hand, asserts that all there is to the entities are those structures and relationships. OSR apparently gets support in the fundamental physics community, particularly from researchers working in quantum field theory.

When considering these two views, ESR seems like the more defendable position to me. But I can see the argument from the OSR advocates. If there are intrinsic non-structural non-relational properties or aspects of entities in the world, how would we ever know about them? If they have no structural relations with anything other than the entity itself, how could we ever interact with them to observe them? Can they exist for us in any meaningful manner?

It’s worth noting that many panpsychists make an appeal to these intrinsic properties, arguing that they could be what provides consciousness to matter. In fact, it was Philip Goff’s description of causal structuralism, and his arguments against it, that first alerted me to the concept of structuralism. Ultimately the appeal to intrinsic properties seems to imply an epiphenomenal type of consciousness that seems problematic.

The motivations of the OSR advocates seem to be to close off these kinds of discussions. But the distinction between ESR and OSR strikes me as utterly metaphysical and unknowable, which I think defaults me into the ESR camp.

There are a number of criticisms of structural realism discussed in the SEP article. Two I find notable. One is that it implies a sort of Tegmarkian (mathematical universe hypothesis) view of reality. But this doesn’t seem right to me. Structural realism doesn’t seem to be arguing that all structures modeled by mathematics are real, only ones that have some reliably causal relationship with empirical observations.

The second one appears to have more bite. It’s that, strictly speaking, structures are not preserved across theory change. In reality they’re approximately preserved. But I think when we consider that the typical realist position isn’t that scientific theories are absolutely perfectly true, only that they approach ever closer approximations of truth, this criticism loses most of its bite. But I don’t know that it loses all of it.

Consider the examples I cited above. Arguably the structures of Newton’s theories are preserved well enough that we can say they mostly reflect reality, again to the extent they remain useful for NASA. But can we say the same thing about Ptolemy’s model of the cosmos? We could argue that his structures are preserved, but only from the standpoint of an observer on Earth, a pretty limited scope.

No one at NASA with their head screwed on straight would use any of Ptolemy’s structures in planning a mission. A structural realist could argue that the Ptolemaic model was a pre-scientific one, that well tested scientific theories are unlikely to be as far off. But that assumes we may never be as far beyond our current theories as they are beyond the Ptolemaic system. It seems like an example that should make us cautious.

On the other hand, I don’t know that we should expect complete perfection in these outlooks. A philosophy of science view, to be useful, arguably only needs to provide useful heuristics, assumptions we should still always be prepared to revise. In that sense, structural realism may be reliable enough for most purposes.

What do you think? Does structural realism make scientific realism a more plausible position? Or does it sacrifice too much to retain the “realist” label? Is the remote possibility of major structural change a fatal flaw? Or should we just stop letting the problems of fundamental physics constrain our philosophy toward the rest of science, where traditional realism is a much easier proposition?

69 thoughts on “Structural realism, a way to be a scientific realist?

  1. There is a scientific attitude that applies here. Whenever there are competing theories in any area, it tells us a couple of things, one of which is that no one of those theories is completely satisfying. I was taught that when you reach a point of asking “Which theory should I apply here?” that answer is “The one that works.”

    This allows one to keep working and eventually things will get sorted out. The wisdom in this is that of patience, but also it is a little like the story of the panicked little girl whose cat won’t come down from a tree and the uncle who asks “Have you ever seen a skeleton of a cat in a tree?” There is no sense in getting all hot and bothered when things will work themselves out. I am unaware of an area of science where this has not worked out. Of course, we still do not have good physical interpretations of quantum mechanics yet, but we also have not run out of time.

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    1. Definitely at a pragmatic level for a working scientist, it often doesn’t matter, at least in day to day research. But it can have an effect on the psychology of theorists, on what theories they’re willing to explore. Consider this quote from Stephen Hawking comparing his attitude with Roger Penrose’s.

      He’s a Platonist and I’m a positivist. He’s worried that Schrödinger’s cat is in a quantum state, where it is half alive and half dead. He feels that can’t correspond to reality. But that doesn’t bother me. I don’t demand that a theory correspond to reality because I don’t know what it is. Reality is not a quality you can test with litmus paper. All I’m concerned with is that the theory should predict the results of measurements. Quantum theory does this very successfully.


  2. I take a pretty simplistic view. Realism is the metaphysical belief that there is a consistent lawful reality that exists before, after, and outside of our perceptions. (We, of course, are part of that reality.) Science is the self-correcting search to understand and codify that reality, and — because it’s self-correcting — converges over time to a closer and closer approximation.

    E.g. Ptolmey → Copernicus → Newton → Einstein → ??? …

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    1. That seems like realism on two axes. One is on the realism-idealism axis, which I’m with you on. And it seems like few scientists, particularly in the natural sciences, are idealists. (The ones I’ve seen invoke idealism were in fields like linguistics or psychology.)

      The other is on the axis of how we think scientific theories relate to that reality. Your stance definitely seems like scientific realism. I’m with you on science outside of fundamental physics.

      But for fundamental physics, this structural realism seems promising, if for no other reason than it gives me an honest way to more clearly separate my views from prescriptive instrumentalism.


      1. I don’t draw that distinction in science. It’s all a convergent process to me — an attempt to understand physical reality. My simple view doesn’t find much role for philosophical navel-gazing therein. The science itself is hard enough!

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  3. I tend to think of myself as a realist. But, realistically, instrumentalism gives a better picture of how science works.

    … realism is the position that the elements of a scientific theory represent reality.

    Well of course it does. But what is the meaning of “represent reality”?

    It’s not as if there is some god giving us rules of representation. The rules of representation that we use will all come from humans. To a significant extent, a scientific theory provides us with the rules of representation. When we adopt a scientific theory, we accept that theory’s rules of representation. Accepting those rules of representation really amounts to adopting a social convention (a convention within the society of scientists).

    Science is fundamentally pragmatic. When we find a new convention (a new set of rules of representation) that work better, we go for that and retire the old convention.

    Theory change is simply a consequence of scientific pragmatism. When we find a theory that works better, we move to adopt it.

    The example I usually cite is Ptolemy’s model of the universe. For centuries it more or less accurately predicted naked eye astronomical observations, but we now know its model of a stationary Earth, with everything else in the universe revolving around it, is wrong.

    The mistake here is to assume that truth is human-independent. It isn’t, and it couldn’t be.

    Ptolemy’s theory was true at that time. It was true, in the sense that it faithfully followed the accepted rules of representation. Today, we see it as false — but that’s only because we have changed the rules of representation that we use.

    People seem to assume that there must be some platonic perfect way of representing the world. And they take truth to be determined by that platonic system of rules of representation. However, I can find no basis for such a belief. The best we can do is pragmatically construct our own rules of representation, which is what science does.

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    1. Neil, would you agree that as science changes these rules of representation, that it’s making progress? If so, what would you say it’s making progress towards? If not, then in what sense would you say you’re a realist?

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      1. Yes, I see science as making progress. But I disagree with philosophers about what that means.

        Philosophers of science usually think of progress as moving toward a final theory. However, I see no reason to assume that there could ever be a final theory. I see it as making progress in the sense of continuing to get better. I guess that’s a pragmatic view of “progress”.

        Philosophers tend to see science as being about the theory. And I disagree with that.

        Take an example. Due to modern physics (some of it not so modern), we have a number of GPS satellites. These allow us to get very precise location information. But the laws of physics did not launch the satellites. If we stopped sending up those satellites, we would lose a lot, even with the same laws.

        For me, progress means that we continue to improve the quantity and quality of information that we are able to get. It’s not the laws — it’s the information and the continued access to information on demand.

        As another example, take Newton’s laws. Because of Newton, we could now talk about the force of friction and the force of air resistance. With Aristotle’s physics, friction and air resistance were seen as just part of the natural slowing down of things, and we could not measure them. Again, it was the increase in information that we could collect that made Newton’s laws so valuable.

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  4. Scientific theories are predictive because, and only because, they are explanatory. They are intrinsically empiric. And so, they offer better and better explanations of our experience in total, without ever uncovering some “really real” substrate which was heretofore completely unknown. There is no occult reality, wholly independent of our experience, to be discovered. How would one propose to scientifically discover such a thing?.

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    1. You can’t. All we can do is get better and better explanations. But by what standard do we say the explanations are getting better? What makes one better than the old one? On a spectrum between a theory that’s a perfect explanation, one that only provides a partial explanation, and one that provides none, what is different about them? What is the axis of that spectrum? We can’t just say the accuracy of the predictions, because I don’t think we’d consider a black box that made perfect predictions, with no insight into how it was doing it, to be explanatory.


      1. If I want to know how a wing works, Newtonian mechanics is better. If I want to know how a microchip works, quantum mechanics is better. I don’t think it makes sense to speak of theories as being globally superior to other theories.
        The black box would be explanatory as part of a larger series of events. As a standalone predictor, it would be an Oracle, and so nonscientific. I assume we want to continue talking about scientific predictions and not oracular ones:)

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        1. I actually was talking about comparing theories in their domain of applicability. Certainly we don’t want to compare general relativity to, say, a theory about ribosomes. We’d want to compare it to Newtonian gravity. And the black box example was just to make a point. Although in the end, I’m not sure we really ever get any standard other than the rate of prediction success, although we want to know how those predictions work.

          My broader point is that it seems like there’s something general relativity is closer to than Newtonian mechanics is. It might be pragmatic to call that something “reality”, as long as we keep in mind we’ll never arrive there, only (hopefully) get ever closer. But you could also view it as we’ll have theories with more and more accurate predictions. The word “reality” is just a crutch.

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          1. I understand, but my point is that within physics, the greater detail and precision of theories of the small may actually make them less accurate in macroscopic applications.
            Likewise, I am not so sure that we really are getting closer to something with general relativity as opposed to Newtonian mechanics. That may be mistaking precision for accuracy, and detail for truth.

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          2. Certainly trying to use quantum physics to predict chemical reactions, much less the weather, would be the wrong tool for the job. But within a theory’s domain of applicability, if the precision is inaccurate and the details false, it seems like it would come out in testing. If it passes those tests but still doesn’t approximate reality to some degree, it seems like we’re at the no-miracles argument I mentioned in the post.


          3. Sure, back to the no miracles argument. But the question is how do we get there? As you asked, what is the standard for accuracy? It seems to me that that begins and ends with observation – experience. That is the standard for accuracy. I don’t see how that can ever translate to representation of a “hard”, non-experiential reality. I don’t think there could be a standard on those terms.


          4. Ah, we’ve been having a different discussion than I thought. The realism vs idealism debate is much broader. My take is both are theories, just like any other. The question is which requires fewer assumptions. Both have to account for scientific observations. But to me it seems like idealism has to account for events no one expected, like COVID, that realism can take to just be the unexpected results of mindless physical laws playing out.


          5. But isn’t idealism just a particular flavor of realism? It seems to me that the realist vision of scientific endeavor has us whisking away the dust obscuring an underlying structure, whatever the nature of that structure should be, rather than building out the details of an explanation.


  5. Apparently I’m like you here Mike, or a strong instrumentalist, except that I consider the quest for a way to intelligently be a scientific realist, to be fraught with epistemic peril. It may make some feel better to talk of “truth” and “facts”, though at the cost of accuracy. Science will always remain provisional, and this is mandated by the subjective nature of experiencing existence. Apparently there’s only one truth or fact about reality itself that I can ever be assured of, or that my own subjectivity does exist (from Descartes of course). All else shall always remain more and less credible belief.

    Perhaps this proclivity of mine stems from my deep appreciation for clear and effective statements? For example I like to “presume” rather than to “assume”. So when I define a term like “consciousness”, I get to the point that I mean to express without adding various extraneous qualifiers such as “Must be biological”.

    Need I be this pedantic? Perhaps not, though to me this seems warranted given that words not only reside as our medium of expression, but the medium by which lingual humans tend to think. That’s pretty basic! Sloppy terminology should at least subtly lead to sloppy science.

    The “cure” as I see it, would be to develop a respected community of professionals with accepted principles of epistemology (and metaphysics, and axiology) from which to guide the function of science, both in this regard and elsewhere.

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    1. Eric, what do you mean by “strong instrumentalist”? I’m not sure that describes me. In truth, with the discovery of structuralism, which articulates a coherent point between traditional realism and instrumentalism, I’m not sure I’d say anymore that I am an instrumentalist. At least until someone identifies a fatal flaw in the structural realism view.

      On a respected community of professionals, I think we have that with scientists and philosophers of science. (Although admittedly the former often have little respect for the latter, even while often adopting their ideas.) Or at least we have a group of people trying. You keep dismissing these efforts and saying we need to start over. But what makes you think a new community would arrive at different positions than the current one? Maybe we just need to keep making progress anyway we can.

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      1. Right Mike, I probably shouldn’t have put you in my boat. I’m the strong instrumentalist who isn’t looking for a way out, while you would like an out. Maybe you’ll decide that this “structural realism” business gives you that. To me this sounds like a convenient complication which would thus sacrifice parsimony. I’m not out to fix what I don’t consider broken, and especially when there are major things that I do consider broken…

        I agree that we do have respected scientists and philosophers, though among them they provide no generally accepted principles of metaphysics, epistemology, and/or axiology from which to do science, and worse still, few seem to grasp that science should need such accepted principles in order to potentially improve in substantial ways. That’s what I consider broken — an inability to grasp what’s needed. How might we intelligently fix something when its flaws aren’t formally acknowledged?

        So what I think we need is a new initially small community, built somewhat from the old, with the founding premise of agreement within regarding various formal principles of metaphysics, epistemology, and/or axiology. Note that the existing system would remain as well, with this new community formed additionally. And perhaps there would be many such communities vying to become the most respectable group of “meta scientists”? I’d like that! Regardless such a community would develop various principles that they think would help to guide science (such as my own four). If scientists were to find a given community’s principles effective for their work, then I’d expect this community to grow and become increasingly influential over science and humanity in general.

        The people who should hate this most would be traditional philosophers now largely relegated to “historians and artists of metaphysics, epistemology, and axiology”. My perception is that things would get quite nasty! Regardless I do think that’s what science needs in order to markedly improve, and mainly in its softest forms which remain most susceptible to structural failure.

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        1. Eric,
          What about structural realism do you consider unparsimonious?

          My biggest issue with hard core instrumentalists is they tend to be satisfied too quickly. If a theory makes accurate predictions, they’re ready to declare victory even if it clashes with other reliable theories. (Sometimes we’re stuck with that scenario, but it should be recognized as the problem it is.) From what I’ve read, work in quantum foundations was suppressed for decades due to this kind of attitude. For that matter, you can blame a similar view for the behaviorist movement and its effects on psychology, also for several decades. This stuff really does affect how people do science.

          I think I’ve said this before, but if you really want to start a new field, your best option is to start doing the work that will define it. No one ever started a new science or philosophy by advocating for a new science or philosophy, at least not by that alone. They started it by doing the kind of work they were advocating for and paving the way, showing how it could be done.

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          1. Mike,
            If it’s not possible for something inherently subjective to be objective (except regarding just one specific sort of observation), to me it seems non parsimonious to continue trying to intelligently claim “realism” anyway. Why not explicitly acknowledge your boundaries? I’d rather not complicate my perspective with such technical nuances.

            As for your problem with instrumentalists being satisfied, am I not one of the most unsatisfied people that you know? I consider myself wholly unsatisfied with the situation in our soft sciences and philosophy. And I’m not just bitching here, but proposing potential solutions. Furthermore they’re often derived through my own introspection, or the opposite of what methodological behaviorists advocate.

            Yes Einstein is a hero of mine, though in retrospect I can admit that he did make some crucial mistakes. Even if our metaphysics does mandate that “God doesn’t play dice”, I think he should have supported the original Copenhagen interpretation for its instrumental virtues. Instead today we get all sorts of funk ideas such as Sean Carroll’s non instrumental “many worlds” crap (not that all Everettian interpretations must be so literal, but still).

            So why do I merely talk about this sort of thing rather than actually do something about it? I guess this is mainly because I’m a standard nobody who thus considers himself relatively weak. It takes far more than to simply have good solutions than to actually implement those solutions. I’m simply a working family man who blogs. Yes I do keep my eyes open for potential ways to have influence with prominent people, and I’d love to find various generally aligned regular people in my travels. Even if my ideas do happen to be pretty good however (which of course is speculative), I do try to keep my feet on the ground. I try to have fun with this stuff, as do you.

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          2. Eric,
            I can’t seem to parse your comments about parsimony here. I’ll just note that we can regard realism and idealism as theories, just like any other, and ask which requires more assumptions. Both have to account for scientific observations, but idealism also has to account for where events that surprise everyone actually come from.

            Einstein did accept the achievement of the Copenhagenists. But his contention was that quantum theory wasn’t finished, that there was more work to be done. His and Schrodinger’s 1930s papers were really the last marks of progress in quantum foundations until the 1950s. Even Jim Baggott, who favors anti-real interpretations, admits that a lot of the progress has come from realist theories inspiring experimental work, which instrumentalist theories are not good at doing.

            Totally understand on just having fun!

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          3. Mike,
            We’ve seemed to be talking at cross purposes somewhat, so I went through your article again. Apparently what you’re claiming for “realism” does remain provisional. I guess it just troubles me to use a term such as “real” epistemologically, as well as “truth” and “fact”. (And don’t get me started on “idealism”.) So perhaps I was supporting “instrumentalism” somewhat because the name itself doesn’t offend me?

            In any case my second principle of epistemology specifically demonstrates my beliefs here, and regardless of what title this puts me under. It states, “There is only one process by which anything that subjectively experiences its existence, may subjectively figure anything out. It takes what it thinks it knows (or evidence), and uses this to assess what it’s not so sure about (or a model). As a given model continues to remain consistent with evidence, it tends to become progressively more believed.”

            So this is what I propose for a parsimonious rule. Note that scientists naturally have reason to subvert this principle in situations where conforming would be inconvenient. Thus I believe that an explicit rather than implicit rule is needed to promote “hardness” in science.

            It’s good to hear that my hero did accept the original Copenhagen interpretation provisionally, as well as presumed that more work was needed. Indeed!

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          4. Eric,
            Thanks for revisiting the post!

            The problem with rules is it always requires judgment to know if they’re being followed or violated. For instance, a hard core many-worlder would say they’re taking what they think they know (the raw quantum formalism) and using it to assess what they’re not so sure about (the state of the universe). I presume you don’t accept this as a valid case of following the rule, but, strictly speaking, it seems to follow the letter of it. I do think there’s a valid concern about the amount of “terrain” between where the formalism has been tested and the predictions of other worlds, but your rule doesn’t seem to address that issue.

            I don’t want to oversell Einstein’s acceptance of Copenhagen. Here’s a typical quote of his feelings toward it, leading up to the phrase in relation to QM he’s most famous for.

            “Quantum mechanics yields much that is very worthy of regard,” Einstein wrote to Born. “But an inner voice tells me that it is not yet the right track. The theory . . . hardly brings us closer to the Old One’s secrets. I, in any case, am convinced that He does not play dice.”

            Halpern, Paul. Einstein’s Dice and Schrödinger’s Cat (p. 104). Basic Books. Kindle Edition.

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          5. Mike,
            Thanks for giving my model that testing. This is how one might gain a working rather than simply lecture level grasp.

            Actually I don’t mean to excluding any variety of MWIer from my EP2. My theory seeks to represent the beliefs of anything which subjectively experiences its existence, such as a mouse. So it’s not quite about achieving “good” answers, but rather a kind which is “reasoned”. Here it’s the process itself that matters rather than the result.

            Your query however suggest that maybe the “…figure anything out…” idea misrepresents my meaning somewhat. From now on I think I’ll instead go with “…reason anything out…” Theoretically there is only one process from which to reason. You take what you think you know (or evidence), and use this to assess what you’re not so sure about (or a model). You could challenge me here by proposing an alternative means from which to reason, or beyond induction.

            Ah but if that’s the case then I suppose you’ll ask about deductive reasoning, which is to say statements that are true or false by definition. Is this not different? Ultimately I think it reduces back to induction.

            First note that only a creature armed with language has any potential for deduction given that language statements are inherent here. Second, consider a deductive statement such as “2+2=4”. Here evidence exists as the statement itself, or what you think you know, and the model you’re assessing is whether or not the statement happens to be true. Of course this one is obvious which should somewhat hide what you do to assess it. In a complex enough statement however (whether in mathematics or English), you may need more evidence by means of writing some things down or punching some things into a calculator. Just because we have language statements which may inherently be true or false, I’m suggesting that the educated human should not have attained an inherently different variety of reasoning than standard induction.

            (There’s abduction as well though to me this seems even more plainly based upon induction.)

            I’ll also mention a quite standard competing strategy where we simply accept the views of others without personally checking the evidence. This may effectively be referred to as “faith” rather than “reason” however. For example to some degree I need faith that scientists aren’t fabricating their evidence. But here I might at least reason that it seems implausible that reproduced studies might have been fabricated so many times. Or a theist might support his or her faith in God by means of various apparent miracles, or perhaps given the good deeds of their church.

            In any case I’m proposing that beliefs are based upon both reason and its opposite, which faith. Furthermore we have a respected group of hard scientist that provide various generally accepted understandings for us to use. Hopefully we’ll also develop a community of respected professionals which is able to provide various generally accepted principles of meta science which helps our mental and behavioral varieties harden up.

            On Einstein, yes that’s my hero — no ontological dice playing for he and I. And none for Sean Carroll either, though if Einstein were around I’m sure that he’d have a good laugh at some of what’s been going on since he left.

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          6. Eric, I agree with much of that. I’d just note that I don’t think language is needed for deductive reasoning. Non-human animals do simple deductive reasoning all the time. You do need language to communicate your deductions, but of course that’s tautological. Symbolic thought, including language, does vastly increase the scope of what we can reason about and how far we can take it.

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          7. Now that you mention it Mike, I do remember reading and article suggesting that even bees display mathematical figuring such as counting. Furthermore I suspect that there’s a subjective dynamic to them. Anyway it’s good to hear that I’m making sense here. For a moment it wasn’t entirely clear to me that my EP2 would remain as the unique process that I’ve been advertising for years.

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  6. If a theory is correct / true? It can accommodate new data / information. (As far as ‘we’ know so far.)
    Or, cannot be falsified except for … there will always be persons / minds that cannot accommodate new information. And so the divide / debate continues.

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    1. Certainly the success or failure of a theory hinges on how well it’s compatible with observations, old and new. But usually a theory has components that are unobservable. These are often unavoidable components, structures and relations, that form part of its ability to explain and predict the observations we can see. The question is, what should be our stance toward those components? Are they “real”? Or mere mathematical conveniences?


  7. >A philosophy of science view, to be useful, arguably only needs to provide useful heuristics, assumptions we should still always be prepared to revise.

    I like that. Any theory, “as long as it’s useful and was empirically obtained” regardless if it’s ultimately “true” or not, would be my ideal for what science represents. After all, everything we see, feel, hear, taste or smell is actually an interpretation of reality. All factors of existence filtered through some unfathomably complex, but ultimately crude biological translation layer. When it comes to true vs useful, I’ll take the latter every time.

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    1. I’m onboard with useful. But if that’s the only standard, it ends up being a pretty instrumental view. Of course, if we’re looking for useful in understanding reality, we’ll probably have a higher standard than merely useful for making predictions. But in terms of a philosophy of science, the real issue here is our assessment of theories. Should we be satisfied with an explicitly anti-real theory, or consider it even more of a placeholder than the normal provisional nature of scientific theories?

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  8. > “But usually a theory has components that are unobservable. These are often unavoidable components, structures and relations, that form part of its ability to explain and predict the observations we can see. The question is, what should be our stance toward those components? Are they “real”? Or mere mathematical conveniences?”

    I think we could never know what the “reality” is. We, humans, are trying to create some copy (as a theory, math construct, belief, etc.) of “the reality” and compare it with “reality.” However, we could never be sure that our “copy of reality” does not miss some components. Therefore, we could never say with 100% confidence that observable or not-observable components are “real.” For that reason, I do not see any “realism,” scientific or not, as a viable.

    As for math, it makes sense to look at it as abstract structures. Then, the question would be, are those abstract structures just our instruments, and, if not, then how those abstract structures relate to “the reality” we are trying to understand.

    Many of the current physical theories originally were born from some math equations, assumptions, etc. Just remember Einstein. Also, it looks like the discussion about structural realism revolves much around mathematical structures. For me, one very interesting question is, do abstract structures represent “the core” of so-called reality? Could we understand, or imagine, how that could be?

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    1. Definitely, we can never know that a theory is a full and complete account of reality. But realism, as I understand it, doesn’t demand that, only that the theories approximately represent reality to an ever closer degree. All theories are provisional, subject to being replaced on new evidence. But the replacement has to replicate all the successes of the old theory while going beyond it, which means the structures of the old theory, in approximation, should be preserved in the new one, at least in most cases.

      Structural realism does focus on the structures modeled by the math. Note that I was careful with the wording there. The math, in and of itself, isn’t the structure. In many cases, we might have multiple mathematical frameworks to model the same underlying structures. (Quantum mechanics, for instance, has several, although people often focus on the Schrodinger equation.)

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      1. We could replace the wording “abstract structure” with “abstract” in my previous note. All math is based on abstracts. Numbers, geometrical figures, etc., and relations between them are all abstracts. I still believe that the term “realism” is still a misleading one in the contents of this discussion. If we embrace that the essence of the discussion is about abstracts, then we will have to look at it in a new light.

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          1. What is “abstract” – that is a separate discussion. I think that this definition from Wikipedia makes sense: “Abstraction in mathematics is the process of extracting the underlying structures, patterns or properties of a mathematical concept, removing any dependence on real-world objects.”

            We could say that abstract is something where there is no dependence on real-world objects (as we know or imagine those objects).

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          2. Thanks for that clarification. I’d say those aren’t the structures that structural realism is concerned with. It’s concerned with structures that are dependent on real world objects, entities, and relations. The way I described it in the post is that they have some kind of causal relationship with empirical observation.

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  9. I think we would like our models of the world at the macro and microlevels to resemble somewhat our world of ordinary experience. We can think of atoms as something like little balls and molecules as a bunch of little balls connected together.

    We can grasp an electromagnetic wave from our experience with waves from tossing a pebble in a pond. Einstein’s gravity is like a spiral wishing well.

    The problem comes when there grows a disconnect between our models of the ordinary world and the actual science. Hence, we end up with multiple interpretation of QM. How do we model in our ordinary world imaginary numbers which appear to be necessary for QM? How does a wave act like a particle? What would structural realism tell us about the many worlds interpretation? Are the many world really out there?

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    1. One thing I wonder about imaginary numbers is if they show up in places in the equations that might be relations between physical entities rather than the entities themselves, such as the relationship between angles and sides. Of course, any physical entity is composed of relations, and that may hold down to the most fundamental entities themselves, so that might not give us any real relief.

      In terms of QM, I think structural realism would favor that the structures modeled by the Schrodinger equation are real, but it would be agnostic on what the nature of that realness might be. So it would rule out the entire thing being a mathematical contrivance. What it can’t address is the scope of those structures. In other words, do they continue to evolve through a measurement according to the mathematics? In other words, SR can’t help us in knowing whether the current model is complete (i.e. no hidden variables). The many worlds hinge on the answer to this question.

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      1. My thought (and not sure where it comes out on the issue under discussion) is that there are aspects of reality that we can’t map exactly to the models in our brains. We can learn about them, find mathematical relations, do predictions, but in a fundamental way we cannot grasp them through ordinary experience. Structures may underlie QM (or not) but they are not anything we can easily conceptualize as a structure.

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        1. I think that’s definitely true. I’ve never seen a visualization of quantum spin for instance. You often see a symbol of a spinning ball, but everyone knows that’s a caricature based on early conceptions that turned out to be simplistic. But we use them because no one has come up with anything better. I think it was Max Tegmark who said it’s one of those things we only know through the mathematics deduced from empirical observations.

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  10. Well, I certainly wouldn’t expect NASA scientists and engineers to use Ptolemy’s model of the cosmos, but it’s still a pretty good model if you’re an amateur astronomer. In that sense, it’s still a very useful thing.

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    1. That’s a very good point! I do think I’ve seen cases of observational astronomy using Ptolemaic concepts in discussing, say, where in the sky Mars might be found on a particular night. So the scope is limited to an observer on Earth, but that’s really all you need for a backyard telescope.

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        1. That reminds me of something that was an issue in early NASA missions. Initially, the planners of the Apollo missions wanted to use an absolute space based 3D navigating coordinate system. But the astronauts, being pilots and used to aeronautic navigation paradigms, balked. If I’m remembering right, they decided to switch systems at various points in the mission: one for when they were over the Earth with Earth as the floor, a second for when they were in deep space between Earth and the moon, and a third for when they were over the moon, with the moon as the floor.

          Sometimes you just have the use the models that are most convenient for where you are. An amateur astronomer on a Mars colony will probably want to use a Mars based system to find things in the sky.

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          1. I remember something about that as well. It’s sort of like that line from Ender’s Game: “The enemy’s gate is down.” You just have to pick the easiest frame of reference available to you and stick to it.

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  11. “The position that the elements of a scientific theory represent reality.”
    I can only say that I HOPE that to be the case – it is what I would like to hope science can provide. Might provide. I have never been interested in approximations or analogies or theories unless they tell me what is really out there.

    Read my first Carlo Rovelli the other day. None too sure that I am any the wiser (or that he is) . Thought provoking nonetheless.

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    1. That pretty much sums up my attitude, although I fear approximations might be the best we can hope for. At least they’re better than the useful fictions that hard core instrumentalists insist is all we have.

      I haven’t read a lot of Rovelli. I did read a good chunk of his Seven Lessons book, but I found it too basic, and it’s made me leery of his other stuff. That said, I pre-ordered Helgoland, which won’t be out here until late May.

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  12. I like “Ontic Structural Realism” as described in the Stanford Encyclopedia article. What I like about it is that it seems like a way to simplify any model of reality that is not already stated in its simplest form, by reducing the number of dimensions in it. If you can get rid of talk of some of the objects or properties by focusing on the relations between them, winding up with fewer terms, that’s a good move.

    ” a corresponding crude statement of OSR is the claim that there are no ‘things’ and that structure is all there is (this is called ‘radical structuralism’ by van Fraassen 2006),” says that article. That would be too crude, because structures can be things, which to me boils down to: they sit in the noun role in our languages. Ontology recapitulates philology, as W. V. O. Quine said. Snow is white if and only if “snow is white” is true, as Tarski said. (I have turned Tarski’s formula around to highlight the fact that there is no such thing as semantics-free truth.)

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    1. I do see the appeal of OSR. And as I mentioned in the post, ESR and OSR are epistemically and operationally equivalent. Any talk of an intrinsic nature that is utterly unknowable seems also utterly irrelevant. The only way we could ever know about them is if it turns out that have some kind of relational properties after all.

      I would say that all things seem to be structures and/or processes. The question is whether all structures and processes are composed of things. With QFT, it seems like we’ve just hit structure and process. But that assumes we won’t eventually find things it’s composed of.

      Ontology recapitulates philology? Hmmm. I don’t know. It seems to assume that multiple philologies can’t converge on an ontology. If not then scientific breakthroughs are just fads. That seems too post modern. But maybe I’m reading too much into the phrase?

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      1. You’re reading too much into the phrase. Different languages (e.g. English, Chinese) will phrase the same ontology (e.g. no time apart from spacetime) in different ways. Although English speakers, with their tensed verbs, may have more difficulty avoiding a scientific faux pas, it can be done.

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  13. Hi Mike,

    You wrote, Under structural realism, it isn’t necessarily the concepts discussed in the theory descriptions that are real, but the structures and relations revealed in the mathematics. There may be multiple possible underlying realities from which these structures emerge, but the structures and relations appear to be what endures. If so, a philosophy of realism that focuses on the structures seems much more defendable than traditional realism.

    What does it mean “to focus on the structures” and why is that different than traditional realism?

    What I think this means is that we can have two radically different conceptual pictures of an underlying reality that yield identical mathematical relationships. That makes sense. But is mathematics ever without a conceptual underpinning?

    And I suppose “traditional realism” might begin with the concept, and try to understand how that conceptual “thing” is behaving such that we get certain results, and maybe in the course of thinking about this and exploring the options mathematically we’ll even get some novel predictions. How this sort of realism you’re describing is different is unclear to me.


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    1. Hi Michael,
      Consider the Ptolemaic model of the universe. A traditional realist’s attitude toward this theory might have been that everything really goes around the Earth on concentric crystalline spheres. I think a structural realist would have been more cautious. They’d have said that yes, the structural relationships are real, but probably would not have committed to physical spheres. (The person who initially came up with them, Eudoxus, actually considered them to only be mathematical. It was Aristotle who interpreted them as physical spheres.) In that case, as someone pointed out in the thread, the structural realist view might still be approximately correct in terms of amateur astronomy.

      Or consider something we’ve discussed before, the Schrodinger equation. A traditional realist might say it’s modeling actual matter/energy waves. An anti-realist might say it’s just a mathematical convenience, that any relationship to actual reality is undetermined. I think a structural realist would say it’s modeling something real, but probably wouldn’t go beyond that. The structuralist would stay open to alternate lower level realities.

      Basically, I think of structural realism as minimal or cautious realism. It doesn’t accept that the theory narrative is necessarily right, but it also doesn’t take the theory to be completely unrelated to reality.

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      1. That makes sense, Mike. Where the argument that it’s just a mathematical convenience breaks down for me is the fact that math is the manipulation of symbols according to a syntax, and when we apply that to the real world we must form some sort of bridge between the symbols and something physical. We may not know all of what that physical element is, but in a sense it’s impossible to do the math successfully without having some relationship (that works) between symbol and reality. So if a structural realist simply thinks that mental relationship is probably incomplete, I’m on board with that. It seems like since the dawn of science thinkers have probably varied in their certainty about how accurate such models were–such as Eudoxus and Aristotle.

        But the notion that we might yet discover new relationships we’ve not seen before is captivating, and I think part of the joy of scientific discovery. I’m not sure we’ll ever be able to end this exploration, and I’m also of the mind we’re not going to run out of novel relationships to discover!

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        1. Definitely Michael. The nice thing about structural realism, is it seems to recognize the part of current theories that are likely to survive, at least to some level of approximation, even after we discover those new relationships. Any new theories have to repeat the successes of the old one, which puts some constraints on what those new theories could be. But one of the best things about science is discovering something new and plausible or confirmed that shifts the ground from under your feet.

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  14. Fantastic post! You’ve managed to cover quite a lot of territory in a short amount of time.

    The ESR/OSR divide seems familiar. It reminds me of certain phenomenologists attitudes towards Kant’s noumena—why bother? Or, as you put it, “Can they exist for us in any meaningful manner?” Like you, I’m not comfortable with eliminating entirely ‘that which we can’t know’, but at the same time it does seem sill to posit such a frustrating, ghostly class of entities, or non entities.

    “Does structural realism make scientific realism a more plausible position? Or does it sacrifice too much to retain the “realist” label?”

    I think so. I don’t see this so much as a problem for structural realism as for scientific realism, which from what I’ve learned from your post would seem fairly naive by comparison. Besides, the two seem to apply realism to different things, but I could be giving short shrift to what scientific realism entails. My understanding is that scientific realists believe in some unknown material stuff that exists “out there”, the ongoing discovery of which is finding out the truth, whereas structural realists believe some mathematical structures are real, and there might be something non-mathematical underlying those structures—unknowable noumena. Does that sound right?

    Your points about the Ptolemaic model were the objections I was thinking of as I read your post. As I understand it, it was the model itself that underwent a revolution. For a time, both models were equally good at “save the appearances,” but not equally good on structural grounds.

    Great post, Mike!

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    1. Thanks Tina! Definitely this post is a summary of the concepts, which is why I linked to the SEP and Wikipedia articles for anyone interested in taking a deeper dive. And I agree it’s very much related to Kant’s noumena / phenomena distinction. A lot of this could be seen as different views on the relationship between phenomena and noumena.

      I think you’ve got a good grasp on structuralism. Although I’d say that there’s no requirement that what might be underlying those structures be non-mathematical. It might just be more structure and relations that we just haven’t discovered yet. (It might be structure all the way down.) But the idea is that the structures we’re currently working with would continue, at least approximately, in some form even after theory change.

      The interesting thing about the Ptolemaic model is it is preserved (approximately), at least for observers on Earth. J.S. Pailly pointed out above that, for amateur astronomy, that’s enough. It’s just that the scope of those structures turned out to be far more limited and relative than Ptolemy imagined. A structuralist in the 1500s might have been as prepared for that development as an instrumentalist. (Although the instrumentalists at that time seemed more motivated by denial than epistemic caution.)

      It is an interesting question whether structuralism is a type of realism, as the SEP article implies, or more something in between realism and instrumentalism, as the Wikipedia article seems to assume. Ultimately it may come down to whether we like the term “realist”. But it does seem to address the shortcomings of both the traditional positions. It might come down to which view provides the more reliable heuristics, and structuralism seems to do much better than that than traditional realism, while not requiring that we accept the reliability of our current best theories as a miraculous coincidence.

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      1. Thanks for clarifying structuralism for me…makes sense that it could be more structure all the way down. And if it’s like Kant’s noumena, we can’t say anything about what lies underneath the mathematical structures, if there is anything at all.

        On the Ptolemaic model being enough for amateur astronomers here on Earth, I’d agree so long as we don’t have to get into epicycles on epicycles to account for retrograde motion and that sort of ugly stuff. But certainly when I look up at the stars, I imagine I’m at the center of a giant beach ball looking up at pin pricks of light around its surface.

        On the term “realist”, I think my problem with calling structuralism a type of realism comes from the debate over whether mathematical ideas are real. It seems structuralism views (enduring) mathematical structures as constituting reality, but I think of “realism” as viewing math as an instrument which we use to make sense of an objective, mind-independent world. If that makes sense. It’s a question of whether math is a tool with which we view reality or reality itself…. Maybe I’m just finding the term “realism” confusing.

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        1. You’re far from the only person who struggles with the distinction between the mathematical structures and the reality. My take on structuralism is it allows us to keep a distinction between the math and the underlying structures. Of course, someone like Tegmark says the underlying structures are the math, as opposed to the nomenclature and techniques, which is just how we work with it.

          But I think a realist can make a distinction simply by observing that the mathematical structures aren’t guaranteed to be a perfect representation of the actual structures “out there”. They could be, but it’s also highly likely they’re just close approximations, and some successor theory will be closer. That, to me, seems like enough to keep math as a tool distinct from reality.

          Ultimately it amounts to a betting strategy on how reliable current theories are for predictions about the currently unobservable.

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