By Wayne Myrvold

I posted a link to my blog post, “Beyond Turf Wars,” on my Facebook page. It resulted in an interest back-and-forth involving myself, philosopher Vishnya Maudlin, and Matt Leifer, a physicist working on the foundations of quantum theories, about, among other things, the differences between physics and philosophy, and the respectove roles of the two.   Matt’s own blog, which is worth reading if you’re interested in quantum foundations, can be found here.  I reproduce the Facebook comment thread here; anyone wishing to continue the discussion is welcome to comment on this post.

Vishnya Maudlin (June 11 at 6:09pm)

Philosophers didn’t start the war.

Wayne Myrvold (June 11 at 6:24pm)

“War” is a bit strong, I think. Which is why I called it “squabbling.” I also like Jim Holt’s appellation, “kerfuffle.”

Wayne Myrvold (June 11 at 6:29pm)

Krauss would probably say that David started it. I don’t agree, of course; David’s review of Krauss didn’t strike me as at all mean-spirited or unfair.

I’ve been a bit surprised at how many people describe the review  as “harsh” or “blistering.” It’s blunt, and when he thinks Krauss is dead wrong, he says so. But that’s just David being David.

Vishnya Maudlin (June 11 at 7:08pm)

You know, “war” is a cheap word in US.

Matthew Saul Leifer (June 12 at 6:00am)

Vishnya, If by “physicists” you mean the physics community in general then physicists did not start the war either. Stephen Hawking and Laurence Krauss do not speak for me.

Wayne, I disagree with you that studying the foundations of quantum theory is philosophy. It is physics, it is just that most physicists do not realize that it is physics yet. Of course, there are some questions of a more philosophical nature, but I would argue that the most fertile areas are those which are not obviously purely philosophy.

Wayne Myrvold (June 12 at 6:42am)

Ah, but Matt, but part of the main point of the post was that we shouldn’t worry too much about where we draw the boundaries between disciplines. It’s natural philosophy in the sense of Newton, not counted as physics by many physicists, and may one day will be regarded as clearly part of physics by the physics community—- does it really matter what we call it? Unlike Gutting, I wasn’t trying to stake out a preserve that is and forever will be philosophy’s demesne.

Matthew Saul Leifer (June 12 at 9:16am)

Well, it matters a lot on a personal level if you are trying to get a job doing foundations of quantum theory in a physics department 🙂 More seriously, I think there is a distinction to be made between studying the foundations of a theory in order to better comprehend the theory as it presently exists and studying them in order to arrive at the next theory. There is a sizable group of philosophers of physics, but by no means all or even the majority, who think that their job is only to do the former, and it makes sense to me that this sort of activity would be largely deemed irrelevant by the physics community.

In my view, if you are working on the foundations of some theory and you start with the assumption that the theory in question is correct then you are simply doing it wrong. We ought to be studying distinctions that make a difference, if not right now then in the long run.

Vishnya Maudlin (June 12 at 10:27am)

Matt, of course I agree with you. It is just a result of sloppy writing on Facebook. There are many physicists who regularly talk and cooperate with philosophers.

I agree with Wayne. There is a gray area where the boundaries are hard to draw. Also, I agree with you Matt that philosophers generally are not involved in developing new theories.

But, I completely disagree with your claim that working on the foundation once when we think that a theory is correct (whatever you mean by this – making good predictions?) is a mistake. If a theory can make right predictions it still doesn’t mean that we understand what the theories tells us about the world (this is the point of Feynman’s claim that nobody understand the quantum mechanics. Certainly he didn’t claim that it doesn’t make the right predictions). Or, in Einstein’s words:

“The real difficulty lies in the fact that physics is a kind of metaphysics, physics describes “reality.” But we do not know what reality is if not trough the physical description we give of it.” – Einstein in the letter to Schroedinger

As Wayne said, some of the best philosophers of physics were physicists, but also some of the worst philosophers of physics were physicists. A bad philosophy has a bad influence on the development of science. One can just look what kind of damage a bad philosophy of Bohr and Heisenberg did to QM. One thing philosophers are overall good at is to differentiate a bad from good philosophy. Einstein (who is certainly one of the best philosophers of science) clearly understood that:

“I fully agree with you about the significance and educational value of methodology as well as history and philosophy of science. So many people today—and even professional scientists—seem to me like somebody who has seen thousands of trees but has never seen a forest. A knowledge of the historic and

philosophical background gives that kind of independence from prejudices of his generation from which most scientists are suffering. This independence created by philosophical insight is—in my opinion—the mark of distinction between a mere artisan or specialist and a real seeker after truth. (Einstein to Thornton, 7 December 1944, EA 61-574)”

Matthew Saul Leifer (June 13 at 12:05pm)

OK, I should have known better than to try to summarize my position in a couple of sentences on a thread populated by philosophers of science. I guess I was not very clear. I am not trying to defend logical positivism, so the issue is not exclusively whether you are going to come up with something that makes different predictions.

Matthew Saul Leifer (June at 12:26pm)

Let me illustrate with what I think is the best example, which is the foundations of probability theory. There, we have a foundational question, which is of practical importance. Namely, why is it that we should use probabilities and the standard methods of statistical inference to decide what to believe about the world and to decide what actions to take in the face of the available evidence. The issue here is not one of making different predictions, but rather of different presciptions, i.e. different rules for determining what we should believe and do. There are essentially two approaches to understanding the laws of probability. One can start with the Kolmogorov axioms and try to derive them from more basic ideas of what you think probabilities are fundamentally about. If you fail to derive them then you view the whole approach as a failure and if you succeed in deriving them, by however convoluted a method, then you defend that method to the death as proving that probability is the only logically consistent system for reasoning in the face of uncertainty. The other alternative is to admit that, since we are unable to come up with a fully satisfactory account of why statistical inference works, it may be the case that the standard methods are actually wrong in some cases, although they are a very good approximation for common situations. If this option is not even on the table, then it is unclear to me why you would even be worried about foundational problems to begin with. Concern for foundations must in some way be connected to a worry that the foundational issues imply that there is actually something wrong with the theory. The aim is then to start from basic ideas and take them wherever they may lead you. An example of the former approach would be Cox-Jaynes (not philosophers I know) who make many arbitrary choices in their approach but leave no real wiggle room for meaningful modifications. An example of the latter is Keynes. Although his arguments are not all watertight, and he was wrong on several details, at least he had the courage to follow the natural course of his ideas, which imply that standard probability is not always applicable, and to suggest an alternative. It is interesting that theories not unlike those of Keynes are now in fairly common usage in artificial intelligence, even though the motivation is rather different.

Wayne Myrvold (June 13 at 1:40pm)

Seems to me that there are a variety of perfectly good reasons for concern with foundations, some of which you’ve touched on, Matt.

One is the hope that it will help in the construction of a successor theory. Another is a worry that there might be something wrong with the current theory (not unrelated to the first). Another motivation might be to fend off criticisms that there is something deeply wrong with the theory.

Another concern, though, is: What is the success of this theory telling us about the world? This can be a difficult question because it is not always a simple matter to tell what parts of the machinery of the theory are really doing the work and which are idle wheels. Since it’s his birthday, I’ll mention that JC Maxwell was very good at that. Though he devised mechanical models of the ether, he was cautious about taking them too seriously.

Wayne Myrvold (June 13 at 1:46pm)

Also, the enterprise of drawing ontological conclusions from current theories must be conducted in a way that is compatible with regarding the theory, not as fundamental, but as something that emerges as some sort of limiting cases of a deeper theory. This is something not sufficiently heeded by some philosophers of physics.

I heartily concur with Matt’s “if you are working on the foundations of some theory and you start with the assumption that the theory in question is correct then you are simply doing it wrong.”

Matthew Saul Leifer (June 13 at 2:07pm)

As a pragmatist (somewhat broadly construed) I don’t really see the question “What is the success of this theory telling us about the world?” as distinct from the others. The correct ontological account of a scientific theory ought to have some practical cash value, either by yielding better predictions, suggesting the correct approach towards a successor theory, or by yielding an explanatory structure that is superior to other accounts in some way, e.g. by suggesting experiments that were not thought of before, or by simplifying arguments and calculations. I would include all of these things under the heading of “pragmatic utility”, which may be a bit broader than what some other pragmatists mean by this term. Also, I am not offering this as a criterion for truth in general, but I do believe that pragmatic utility is a defining feature of scientific truth as opposed to any other types of truth that may exist.