Undergrad QFT made Bohmian mechanics a non-starter: missed opportunities?

[vanhees71]

But I don't really see how any of that speaks to the power of one interpretation or the other. I don't really see what you mean by saying that these theoretical tools "use" one interpretation or the other. Supposing the interpretations are all observationally equivalent, then at that level you would be working with the same equations. Theoretically, you could have started from the Bohmian picture or whatever other interpretation you may think of, derived the same things, and then claim you don't need to tackle with the superfluous quibbles of the MS interpretation. At the end of the day, as you said, at the LHC they receive data that they analyze with computers. At that level, all of the entities in any interpretation, including your preferred one, are intermediate "fictions" to explain the results. They don't somehow make direct observations of particles etc, there is a huge theoretical structure at play to even produce these "observations", and that includes a ton of what you call "fictions". So I don't think saying a theory has an "unobservable" element is a strong enough argument on its own.

In general I think it's usually a little bit suspect when some idea is called "minimal", or "simplest possible" and thus supposedly better. It reminds me of how dubiously Occam's razor is always invoked.

Well, a big part of my choice of the minimal statistical interpretation, which is very similar to a flavor of Copenhagen, which neither assumes a collapse (which cannot occur for causality reasons and it's not needed at all to use the quantum formalism to compare what's predicted concerning physical observables and what's found when measured) nor a quantum-classical cut (for which there is not the slightest evidence; rather the classical behavior of macroscopic objects is well-understood as an effective description of coarse-grained macroscopically relevant observables), is Occam's razor.

In the case of BM first of all there's no need to calculate the Bohmian trajectories, because it's not needed to confront the theory with experiment. All our colleagues measure are cross sections and related quantities, and these are just about the statistical properties of the outcome of measurements on ensembles of equally prepared collision systems (at the LHC either 2 protons ->X or 2 nuclei -> X, where there are measurements where X is resolved in to identified particles).

Another case against BM is that there's no satisfactory Poincare covariant Bohmian interpretation of relativistic QFT, while standard QFT in the minimal interpretation is Poincare covariant.

The minimalism I like is, that as a natural scientist one should look at what's observed/observable and not at some philosophical fictions, which never can be objectively tested. The latter are simply not within the realm of the natural sciences, which may be unsatisfactory for some philosophically inclined, who think there's more to be known about Nature than what's objectively accessible to observations, but these are questions more in the direction of a personal world view or religion.

 

[AndreasC]

Well, a big part of my choice of the minimal statistical interpretation, which is very similar to a flavor of Copenhagen, which neither assumes a collapse (which cannot occur for causality reasons and it's not needed at all to use the quantum formalism to compare what's predicted concerning physical observables and what's found when measured) nor a quantum-classical cut (for which there is not the slightest evidence; rather the classical behavior of macroscopic objects is well-understood as an effective description of coarse-grained macroscopically relevant observables), is Occam's razor.

Hmm, I kind of object to that, because I don't think Occam's razor makes any kind of rigorous sense almost every time it is applied, and even when it does, there is no guarantee it's not misleading.

In the case of BM first of all there's no need to calculate the Bohmian trajectories, because it's not needed to confront the theory with experiment.

Ok but where's the problem? Don't calculate them if you don't want!

Another case against BM is that there's no satisfactory Poincare covariant Bohmian interpretation of relativistic QFT, while standard QFT in the minimal interpretation is Poincare covariant.

Right, that is a completely different and more valid argument, although @Demystifier disagrees that it matters. Maybe they are right, I don't know, haven't read the papers.

The minimalism I like is, that as a natural scientist one should look at what's observed/observable and not at some philosophical fictions, which never can be objectively tested.

The issue I have with that is that I don't see how you can coherently partake in some kind of "fiction designation" and "fiction counting" in these theories. Also it's kind of weird because while arguing in favor of a specific interpretation, it feels like you are arguing against the very concept of the argument. I mean, if all that matters is the calculations you make, how can you possibly argue in favor of one or the other interpretation? You can make the same calculations with any of them.

 

[Demystifier]

But vanhees71 is neither of those "shut up" guys. Neither does he shut up himself, nor does he tell you or me to shut up. He openly admits that he doesn't like BM, but that is different from telling somebody to shut up.

He is a polite guy, this is why he doesn't directly tell anybody to shut up. But it seems to me that this is what he means.

 

[Demystifier]

although @Demystifier disagrees that it matters. Maybe they are right, I don't know, haven't read the papers.

The https://arxiv.org/abs/2205.05986 is really a light read, from a technical point of view. Just saying.

 

[Ken G]

In the case of BM first of all there's no need to calculate the Bohmian trajectories, because it's not needed to confront the theory with experiment.

This by itself is not really an objection however, because there are lots of other examples in physics where we calculate things that we don't need to calculate because we don't measure them. A classic example is the "force of gravity", taught to essentially every single physics major in the world. Not only don't we measure that, our best theory of gravity says it is actually impossible to measure it, but this does not prevent every first year physics course from going on about it! The reason is clear, it is regarded as a nice fiction, which means the term "fiction" cannot be categorically perjorative. The true skeptic regards all of physics as similarly a "nice fiction," and expects every single current physics law to be regarded as incorrect at some point in the future.

Another case against BM is that there's no satisfactory Poincare covariant Bohmian interpretation of relativistic QFT, while standard QFT in the minimal interpretation is Poincare covariant.

I would agree that we don't want our interpretations of some theory to impose limitations the theory itself does not impose. Still, even if it is true that BM cannot be made to interpret relativistic QM (a point that I believe @Demystifier has provided counterargument to, ironically in the spirit of saying that BM might not be able to match the "fictions" of relativity, like Poincare invariance, but can be made to match the observables), one could still correctly say that BM interprets nonrelativistic QM. It is perfectly all right to have an interpretation of a theory that has a domain of application, we do it all the time (e.g., the "force of gravity" again). The overarching point is, we should not take any of our theories so seriously that we think the "best" version is "the truth" that we are trying to interpret. (Again, the true skeptic sees the flaw in that thinking.)

The minimalism I like is, that as a natural scientist one should look at what's observed/observable and not at some philosophical fictions, which never can be objectively tested. The latter are simply not within the realm of the natural sciences, which may be unsatisfactory for some philosophically inclined, who think there's more to be known about Nature than what's objectively accessible to observations, but these are questions more in the direction of a personal world view or religion.

But again, I would bring up "the force of gravity." Your statement here condemns the use of that notion categorically! I think it is perfectly fine to explain your own philosophical preferences, which is essentially what you are doing, and to recognize that those preferences have a context that is pragmatic for your purposes, but it is difficult to apply them as objective principles over all of science. How would you respond to the characterization of Poincare covariance, and Occam's Razor itself, as exactly the kind of "fiction" about which you object? You hold that a minimal interpretation is absent of any "religion," but is it not already a kind of religion of its own?

 

[vanhees71]

This by itself is not really an objection however, because there are lots of other examples in physics where we calculate things that we don't need to calculate because we don't measure them. A classic example is the "force of gravity", taught to essentially every single physics major in the world. Not only don't we measure that, our best theory of gravity says it is actually impossible to measure it, but this does not prevent every first year physics course from going on about it! The reason is clear, it is regarded as a nice fiction, which means the term "fiction" cannot be categorically perjorative. The true skeptic regards all of physics as similarly a "nice fiction," and expects every single current physics law to be regarded as incorrect at some point in the future.

Of course, we need the "force of gravity" (in Newtonian mechanics) to calculate the motions of planets, stars, moons etc. E.g., you can derive Kepler's Laws from it. That's well observed (indeed Kepler figured them out by analyzing observations).

I would agree that we don't want our interpretations of some theory to impose limitations the theory itself does not impose. Still, even if it is true that BM cannot be made to interpret relativistic QM (a point that I believe @Demystifier has provided counterargument to, ironically in the spirit of saying that BM might not be able to match the "fictions" of relativity, like Poincare invariance, but can be made to match the observables), one could still correctly say that BM interprets nonrelativistic QM. It is perfectly all right to have an interpretation of a theory that has a domain of application, we do it all the time (e.g., the "force of gravity" again). The overarching point is, we should not take any of our theories so seriously that we think the "best" version is "the truth" that we are trying to interpret. (Again, the true skeptic sees the flaw in that thinking.)

But again, I would bring up "the force of gravity." Your statement here condemns the use of that notion categorically! I think it is perfectly fine to explain your own philosophical preferences, which is essentially what you are doing, and to recognize that those preferences have a context that is pragmatic for your purposes, but it is difficult to apply them as objective principles over all of science. How would you respond to the characterization of Poincare covariance, and Occam's Razor itself, as exactly the kind of "fiction" about which you object? You hold that a minimal interpretation is absent of any "religion," but is it not already a kind of religion of its own?

I don't know, how you come to this conclusion about gravitation or Poincare covariance. The letter is key to our most fundamental understanding of physics and thus for sure no superfluous metaphysical addition to our fundamental theories but to the contrary a key element of it. It's, of course, also based on precise observations of Nature.

 

[Ken G]

Of course, we need the "force of gravity" (in Newtonian mechanics) to calculate the motions of planets, stars, moons etc. E.g., you can derive Kepler's Laws from it. That's well observed (indeed Kepler figured them out by analyzing observations).

We don't need it. We have other ways that never refer to it at all, even within Newtonian mechanics (like Hamiltonian or Lagrangian approaches). That's what I mean, the force of gravity is an unobservable fiction that doesn't exist in a minimalist interpretation of Newtonian mechanics, and never needs to be calculated, so why would you?

I don't know, how you come to this conclusion about gravitation or Poincare covariance. The letter is key to our most fundamental understanding of physics and thus for sure no superfluous metaphysical addition to our fundamental theories but to the contrary a key element of it. It's, of course, also based on precise observations of Nature.

Poincare covariance is a property of the equations, nothing that can be observed. If @Demystifier is correct in his claim that the observations of relativistic quantum mechanics can be correctly predicted using forms of BM that do not obey Poincare covariance, then that is the extent to which your aversion to including elements in a theory that cannot be observed applies to Poincare covariance as well. You put it like, " as a natural scientist one should look at what's observed/observable." So this raises the questions, how does one observe Poincare covariance? How does one observe the force of gravity? If you are actually saying one does not have to observe something, but it is convenient to invoke it when one makes predictions that can be observed, then you are in the subjective realm of "what is convenient" and not in the objective realm of "what can be observed."

 

[vanhees71]

How else do you calculate planetary motion in Newtonian mechanics, if not assuming a force law. It was one of Newton's many great achievements to have found the universal law of gravitation, being the discovery of one of the fundamental interactions in Nature, as we call it today.

Of course you can clarify the question, which spacetime model is correct, by observation. That's, in fact, how it turned out that Galilei-Newton spacetime is an approximate description with a limited realm of applicability, while Einstein-Minkowski spacetime (and it's localized form in General Relativity) has been found to describe all observations correctly. This implies the Poincare invariance of all observables and thus a theory that's not obeying Poincare invariance is at best an approximation.

 

[Ken G]

How else do you calculate planetary motion in Newtonian mechanics, if not assuming a force law. It was one of Newton's many great achievements to have found the universal law of gravitation, being the discovery of one of the fundamental interactions in Nature, as we call it today.

I added the edit (sorry I tend to do that, in hopes the answer isn't read immediately!) that I am talking about Hamiltonian or Lagrangian approaches. What I mean is, let's say Hamilton came along 100 years before Newton, and demonstrated his approach to calculating the motions of planets. Huge success, all of physics seems to now be deterministically accessible. Then Newton comes along and says, "hey you can understand all this if you invoke the existence of forces, including the force of gravity." Hamilton's followers accuse him of inventing philosophical fictions that can't be observed!

Or, what if Einstein in 1600 presents his approach to gravity in the form of an unknown parameter c that is too large to be observed. He also predicts the motion of the planets correctly to lowest order in v/c squared, not only without invoking any force of gravity, but with a theory whose form respects the equivalence principle (as well as Poincare covariance). If Newton then came along later and showed his theory that does not invoke a c parameter but is not Poincare covariant, would people see that as an improvement because it doesn't need an unknown large c parameter, or a fiction because it doesn't obey the key principle of Poincare covariance? Would they point out that Newton's theory is invoking a force that is expressly impossible to observe when there is an equivalence principle that is already regarded as a key symmetry, even though c is still unknown? Would that not still be the case today, if it happened that c was so much larger than it actually is that we still haven't been able to observe it? (I realize this is a hypothetical question because we have observed c so we know Einstein's theory is better than Newton's, but I'm framing this within the context of predictions that are the same in both theories at v scales where the differences are unobservable.)

Or consider Lagrange's approach that all of classical mechanics is described by minimizing action, such that the minimal principle is all processes have an action and that's it. No forces at all, they're all philosophical fictions! Throw in a Feynman like path integral interpretation to the reason that action is minimized, classical motions are now wavelike long before quantum mechanics. Even Huygens had a successful interpretation of Newtonian mechanics, is that the minimal way to look at it because it invokes a concept of interference of propagating signals rather than unobservable definite trajectories? I mean, what if wave mechanics was understood prior to particle mechanics, and then particle mechanics was seen as a duality based on some unobservably small and unknown h parameter, akin to the unobservably large c parameter in Einstein's gravity metric. Are those minimal interpretations because they don't need to invoke some unobservable fiction like particles following definite trajectories that are never actually observed (because one never observes a definite trajectory)? What if statistical explanations had been proposed long before determinism was a thing, would not determinism have to be regarded as a philosophical fiction if Newton suggested it later on?

Of course you can clarify the question, which spacetime model is correct, by observation. That's, in fact, how it turned out that Galilei-Newton spacetime is an approximate description with a limited realm of applicability, while Einstein-Minkowski spacetime (and it's localized form in General Relativity) has been found to describe all observations correctly. This implies the Poincare invariance of all observables and thus a theory that's not obeying Poincare invariance is at best an approximation.

Well here my position is contingent on @Demystifier's claim that the observations of relativistic quantum mechanics can also be predicted correctly with a form of BM that is not Poincare covariant. I don't know if that is actually true or not, so my logic is if it is true, then BM must be regarded as a successful interpretation of relativistic quantum mechanics by your own reasoning, and if it is not true, then we must fall back to the position that BM is a successful interpretation of nonrelativistic quantum mechanics, like you are arguing that the force of gravity is a successful interpretation of Newtonian mechanics. At issue is, if interpretation X successfully interprets theory Y, and if theory Y passes all the same observational tests as theory Y', then interpretation X also successfully interprets theory Y'. If one adds the further requirement that interpretation X is not successful unless it is minimal, then the Newtonian force of gravity is not a successful interpretation of Newtonian mechanics because the Hamiltonian, or Lagrangian, or Einsteinian with untested c parameter, or Huygensian with untested h parameter, approaches have no such object in them as anything but an unnecessary add on, like Bohmian trajectories.

 

[Demystifier]

If one adds the further requirement that interpretation X is not successful unless it is minimal,

I would like to note that the so called "minimal" interpretation is not minimal at all:
https://www.physicsforums.com/threa...on-is-neither-minimal-nor-statistical.998661/
Just the opposite, it is the maximal interpretation:
https://www.physicsforums.com/threa...al-nor-statistical.998661/page-3#post-6450421

 

[gentzen]

He is a polite guy, this is why he doesn't directly tell anybody to shut up. But it seems to me that this is what he means.

It doesn't see like that to me.

My own perception is rather along the lines of what I expressed in the following comments:

Maybe more fundamental, I would have found it nice to clarify A. Neumaier's view on Ensembles in quantum field theory. I don't even understand why he thought that you have to "repeatedly prepare a quantum field extending over all of spacetime" in order to use an ensemble interpretation of QFT. But if already the fact that an ensemble interpretation is not universally applicable is never acknowledged, not even in simple examples, then this makes it difficult for me to dive into such subtle issues.

If you always say "it is simple," or "I don't understand your problem," or "...", then this might be harmless as long as your conversation partner is right anyway and doesn't need your input. But you get him into trouble in the occasional cases where he is wrong, and would have benefitted from you input to see this for himself.

So with respect to BM, the relevant question for me seems to be whether you or other Bohmians could have benefitted from his input. (I will try to "invent" such a possible scenario below, just for fun.)

Well, a big part of my choice of the minimal statistical interpretation, which is very similar to a flavor of Copenhagen, which neither assumes a collapse (which cannot occur for causality reasons and it's not needed at all to use the quantum formalism to compare what's predicted concerning physical observables and what's found when measured)

My impression is that neither Ballentine nor Einstein would agree that the minimal statistical interpretation is a flavor of Copenhagen.

nor a quantum-classical cut (for which there is not the slightest evidence; rather the classical behavior of macroscopic objects is well-understood as an effective description of coarse-grained macroscopically relevant observables), is Occam's razor.

My impression is that you don't understand Bohr's position at all, and "accidentally" side with Heisenberg's position with respect to the cut. But from the perspective of the minimal statistical interpretation, only Bohr's position seems to be valid.
I guess your basic problem is that you don't understand why you have to first fix a context before applying statistics. Many scientists in the "softer sciences" ran into the practical consequences of this misunderstanding. The currently favored solution is to preregister (i.e. fix a context for) studies that would risk to get into trouble with this.

In the case of BM first of all there's no need to calculate the Bohmian trajectories, because it's not needed to confront the theory with experiment.

Maybe the situation is rather the opposite, and BM could actually benefit from input of skeptics like you. If you compute the complete evolution of the whole wavefunction anyway, then the trajectories of BM cannot really give you additional experimentally relevant information. But maybe there is another way to look at BM, where the trajectories are really helpful? What if you compute more than a single trajectory, and really sample from the ensemble of trajectories? The trajectories now tell you which part of the wavefunction you have to compute, and which parts you can ignore. Because now your predictions are really based on the trajectories alone, and no longer on a MWI-like wavefunction.

 

[vanhees71]

My impression is that neither Ballentine nor Einstein would agree that the minimal statistical interpretation is a flavor of Copenhagen.

May be. I thought the key issue with the Copenhagen flavors is just to take the probabilistic meaning of the quantum state in addition to the other postulates, and that's common to all Copenhagen flavors. Then there are as many Copenhagen interpretations as there are early quantum physicists under sufficient influence of Bohr and Heisenberg...

My impression is that you don't understand Bohr's position at all, and "accidentally" side with Heisenberg's position with respect to the cut. But from the perspective of the minimal statistical interpretation, only Bohr's position seems to be valid.

What precisely IS Bohr's position? All I read by him is just some philosophical gibberish. There's no concrete math, and without this you can't clarify the meaning of the words. Where does he think this quantum-classical cut should be? How is this consolidated by experiment?

 

[gentzen]

What precisely IS Bohr's position? All I read by him is just some philosophical gibberish. There's no concrete math, and without this you can't clarify the meaning of the words. Where does he think this quantum-classical cut should be? How is this consolidated by experiment?

Bohr's position is that you have to describe your experiment before you can apply QM, and you have to describe your experiment (i.e. what you actually do in your laboratory) in terms of classical physics (edit: or rather classical concepts), because that is the description that can be communicated.

 

[Lord Jestocost]

...
What precisely IS Bohr's position? .....

The following could perhaps clarify few things. N.P. Landsman in “Between classical and quantum”, chapter 3.2 “Object and apparatus: the Heisenberg cut” (https://arxiv.org/abs/quant-ph/0506082):

“Describing quantum physics in terms of classical concepts sounds like an impossible and even selfcontradictory task (cf. Heisenberg, 1958). For one, it precludes a completely quantum-mechanical description of the world: ‘However far the phenomena transcend the scope of classical physical explanation, the account of all evidence must be expressed in classical terms.’ But at the same time it precludes a purely classical description of the world, for underneath classical physics one has quantum theory.66 The fascination of Bohr’s philosophy of quantum mechanics lies precisely in his brilliant resolution of this apparently paradoxical situation.

The first step of this resolution that he and Heisenberg proposed is to divide the system whose description is sought into two parts: one, the object, is to be described quantum-mechanically, whereas the other, the apparatus, is treated as if it were classical. Despite innumerable claims to the contrary in the literature (i.e. to the effect that Bohr held that a separate realm of Nature was intrinsically classical), there is no doubt that both Bohr and Heisenberg believed in the fundamental and universal nature of quantum mechanics, and saw the classical description of the apparatus as a purely epistemological move without any counterpart in ontology, expressing the fact that a given quantum system is being used as a measuring device.67 For example: ‘The construction and the functioning of all apparatus like diaphragms and shutters, serving to define geometry and timing of the experimental arrangements, or photographic plates used for recording the localization of atomic objects, will depend on properties of materials which are themselves essentially determined by the quantum of action’ (Bohr, 1948), as well as: ‘We are free to make the cut only within a region where the quantum mechanical description of the process concerned is effectively equivalent with the classical description’ (Bohr, 1935).68” [Bold by LJ]

 

[vanhees71]

Of course, I have to describe the experiment I want to analyze, but why should I be forced to do this in terms of classical physics. Most of the experiments done which lead to last year's physics Nobel prize are not even describable without QT!

https://physicsworld.com/a/the-bohr-paradox/

 

[gentzen]

Of course, I have to describe the experiment I want to analyze, but why should I be forced to do this in terms of classical physics.

Because to describe the experiment, you should describe what the experimenters actually do, not how you interpret what they do in terms of your theory.

 

[vanhees71]

To describe an experiment you also need theory to be able to talk about what's done, and if the experiment tests predictions of QT, it's impossible to describe it entirely with classical physics. E.g., when quantum opticians use entangled photon pairs from parametric down-conversion, you cannot describe this entirely in terms of classical physics since Fock states of photons are entirely quantum, and there entanglement cannot be described in any way by classical physics.

 

[gentzen]

To describe an experiment you also need theory to be able to talk about what's done, and if the experiment tests predictions of QT, it's impossible to describe it entirely with classical physics.

You are focusing too much on classical physics, and not enough on classical concepts. You should ask yourself which sort of quantum concepts you could use in addition to purely classical concepts to describe what is being done by experimenters. For example, is it unproblematic to talk about the ground-state of some simple atom, ion, or molecule? What about some specific excited state, or some equilibrium thermal state?

In the end, you need stuff which can be reliably described and reproduced. At least, if the results of your experiment consists mostly of statistics.

 

[Demystifier]

You are focusing too much on classical physics, and not enough on classical concepts.

Focusing more on concepts and less on physics is against everything what @vanhees71 stands for.

 

[Ken G]

Ironically, I think the key to Bohr's "cut" is along the lines of what @vanhees71 has also been saying, that the essential features of any scientific theory must be observables. Poincare covariance is not observable, wavefunctions and Foch states are not observable, quantum fields are not observable, etc. The irony is that although @vanhees71 criticizes Bohr for being too philosophical, it seems to me all Bohr is doing is recognizing the elephant in the room of the logical inconsistencies we have pointed out above (about conflating observables and theoretical constructs as if they were the same thing). Bohr is saying that we have a fundamental paradox to navigate, the ontologies of physics are based on unobservable concepts, while the epistemology of observational science is based on objective tests. Hence in quantum mechanics, the "cut" is essentially the cut between ontology and epistemology, the two pieces of everything we learn in physics that we pretend fit together seamlessly. But they do not fit together seamlessly, and this is essentially the role of interpretations, to create a milieu that allows contact between these things that do not actually touch.

In essence, BM allows the observables, or more correctly the behaviors of the observers, to penetrate into the ontologies by seeking classical interpretations of those ontologies. Everett's prescription is the opposite, the abstract ontologies of the wavefunctions are allowed to penetrate into the behaviors of the observers (who thusly become unable to observe the entire landscape of the universe they are interacting with). And the Bohr "cut" allows us to avoid interpenetration by either domain, essentially "punting" on the need to describe the contact. These are all just ways of handling a paradox that has always been right in front of our faces, even before quantum mechanics: we test our theories with observations, but we do not observe the elements of the theories, nor do we have any theories that describe the behaviors of the testers. This loophole is never closed, it is merely ignored. Quantum mechanics is the place where it is more difficult to ignore, but it was always there.

 

[haushofer]

In the case of BM first of all there's no need to calculate the Bohmian trajectories, because it's not needed to confront the theory with experiment. All our colleagues measure are cross sections and related quantities.

Critics of heliocentrism: In calculating trajectories of planets in our sky you don't need to invoke heliocentrism to confront theory with observation. All astronomers on earth measure with their telescopes are positions on the hemisphere.

 

[gentzen]

Ironically, I think the key to Bohr's "cut" is along the lines of what @vanhees71 has also been saying, that the essential features of any scientific theory must be observables.

Well, there are also actions in addition to observables in control theory, and intervertions in statistical studies. In fact, one of the main differences between the ancient greek precursor of science and the modern scientific method are precisely the controlled experiments enabled by the systematic use of interventions.

The irony is that although @vanhees71 criticizes Bohr for being too philosophical, ... Hence in quantum mechanics, the "cut" is essentially the cut between ontology and epistemology, the two pieces of everything we learn in physics that we pretend fit together seamlessly. But they do not fit together seamlessly, and this is essentially the role of interpretations, to create a milieu that allows contact between these things that do not actually touch.

The irony is that you get very philosophical here, to the point where I can no longer see why vanhees71 should be willing to try to understand what you are saying. In case all you wanted to do is preaching to the choir, well done, your comment is full of brilliant and lovely reflections. But in case you wanted to communicate with vanhees71, I am not convinced of your approach.

 

[Ken G]

Well, there are also actions in addition to observables in control theory, and intervertions in statistical studies. In fact, one of the main differences between the ancient greek precursor of science and the modern scientific method are precisely the controlled experiments enabled by the systematic use of interventions.

I agree, if we are to take into account everything that is on the plate of the scientist, we cannot blithely label a bunch of outcomes as "observations" without some care given to the behaviors that are necessary in order to count them as such. That's why I said it was really behaviors of people moreso than just observables.

The irony is that you get very philosophical here, to the point where I can no longer see why vanhees71 should be willing to try to understand what you are saying. In case all you wanted to do is preaching to the choir, well done, your comment is full of brilliant and lovely reflections. But in case you wanted to communicate with vanhees71, I am not convinced of your approach.

The idea is to convince @vanhees71 that his approach somewhat simplifies the actual requirements of doing science. We can all agree that the scientific method is the defining character of that discipline, and as such it involves a confrontation between theoretical prediction and observational test. The former is generated by manipulating ontologies, and the latter by manipulating epistemologies. At issue is the confrontation itself, which involves crossing a kind of "cut" where an apple is held up next to an orange and some sort of comparison is made. An attempt to formalize that comparison was carried out by Bayes, for example, and other attempts have also been made (say, a frequentist perspective), and the various subjective elements of these formalizations mirror the process of creating interpretations of theories.

One simply cannot deny there is a need to add this kind of scaffolding to the process of testing predictions, it is just that we generally sweep such attempts under the rug and pretend that it is all very straightforward. Then we look at specific examples, like choosing MOND or dark matter to explain galactic dynamics (or, say, heliocentric vs. geocentric solar system models), and we see it is not so straightforward and may generate ongoing debates that can never be resolved beyond all doubt or skepticism. Nor do they need to be, because science is an ongoing process by its very nature.

 

[vanhees71]

I agree, if we are to take into account everything that is on the plate of the scientist, we cannot blithely label a bunch of outcomes as "observations" without some care given to the behaviors that are necessary in order to count them as such. That's why I said it was really behaviors of people moreso than just observables.

The idea is to convince @vanhees71 that his approach somewhat simplifies the actual requirements of doing science. We can all agree that the scientific method is the defining character of that discipline, and as such it involves a confrontation between theoretical prediction and observational test. The former is generated by manipulating ontologies, and the latter by manipulating epistemologies. At issue is the confrontation itself, which involves crossing a kind of "cut" where an apple is held up next to an orange and some sort of comparison is made. An attempt to formalize that comparison was carried out by Bayes, for example, and other attempts have also been made (say, a frequentist perspective), and the various subjective elements of these formalizations mirror the process of creating interpretations of theories.

Theoretical predictions are not due to some philosophical isms or "logies" but the use of math to evaluate what the theory predicts for a given experiment. Nobody cares about "epistemologies" vs. "ontologies". It's just a matter of how well the theorist can mathematically describe what's measured by a given experimental setup or the other way, how the experimentalist can test a given prediction of the theorists by constructing an adequate measurement. Both are creative acts rather than some nebulous philosophical speculation.

One simply cannot deny there is a need to add this kind of scaffolding to the process of testing predictions, it is just that we generally sweep such attempts under the rug and pretend that it is all very straightforward. Then we look at specific examples, like choosing MOND or dark matter to explain galactic dynamics (or, say, heliocentric vs. geocentric solar system models), and we see it is not so straightforward and may generate ongoing debates that can never be resolved beyond all doubt or skepticism. Nor do they need to be, because science is an ongoing process by its very nature.

Well, there are some tensions in the cosmological standard model ($\Lambda\text{CDM}$ model), and it's not yet clear, whether there really is "dark matter" (in the sense that there are yet unknown "dark-matter particles" and maybe yet unknown interactions, all called "physics beyond the Standard Model of particle physics") or if the description of the gravitational interaction by GR has to be modified. Given the high-precision confirmation of GR and the somewhat shaky grounds of MOND, I'd not think that MOND is a convincing solution of these problems. Of course, science is always "an ongoing process by its very Nature", and that's why philosophical "isms" are rather obstacles to the progress of science.

 

[Demystifier]

Of course, science is always "an ongoing process by its very Nature", and that's why philosophical "isms" are rather obstacles to the progress of science.

It's an obstacle only for scientists who spend too much time on this subforum.

If there was no us who constantly put "ism" obstacles in front of you, you would probably have quantized gravity by now.

Now seriously. Philosophy is not an obstacle to the progress of science. In principle, scientists do what they do independently of philosophers, nobody forces scientists to listen what philosophers have to say. Indeed, most scientists simply ignore philosophers and do pure science instead. However, some scientists are not able to simply ignore it. Some scientists are deeply disturbed and irritated by philosophers, and it is this psychological state of being disturbed and irritated that constitutes an obstacle for those scientists. So the problem is not the philosophers, they just do their job, which is philosophy. The problem is how some scientists cope with it. They should learn to focus their mind on things they really care about, and ignore the stuff that makes them disturbed and irritated, be it philosophy, string theory, particle physics (for some cond-mat physicists), politics, or whatever.

 

[Demystifier]

"Bohm's language destroys the symmetry between position and velocity,"

I never understood why is that a problem. In classical physics, most of the languages (Newton, Lagrange, ...) do the same, and nobody complains that it's a problem. Even in quantum physics, the Lagrangian path integral formulation destroys the symmetry between position and velocity, and again nobody complains.

 

[vanhees71]

It's an obstacle only for scientists who spend too much time on this subforum.

If there was no us who constantly put "ism" obstacles in front of you, you would probably have quantized gravity by now.

Well, I'm not sure that this is the obstacle in my case ;-).

Now seriously. Philosophy is not an obstacle to the progress of science. In principle, scientists do what they do independently of philosophers, nobody forces scientists to listen what philosophers have to say. Indeed, most scientists simply ignore philosophers and do pure science instead. However, some scientists are not able to simply ignore it. Some scientists are deeply disturbed and irritated by philosophers, and it is this psychological state of being disturbed and irritated that constitutes an obstacle for those scientists. So the problem is not the philosophers, they just do their job, which is philosophy. The problem is how some scientists cope with it. They should learn to focus their mind on things they really care about, and ignore the stuff that makes them disturbed and irritated, be it philosophy, string theory, particle physics (for some cond-mat physicists), politics, or whatever.

I think we all are in the danger to be caught in our world views. The most prominent example is Einstein, who could not accept the irreducible randomness of Nature, revealed by QT. For the last 30 years of his life he looked for a phantom, inventing a lot of general classical field theories with no success (paralleled by Schrödinger).

Philosophers of science tend to event pseudo-problems which are simply not there like the "measurement problem" or the "ontology of elementary particles".

 

[WernerQH]

Not being able to perceive a problem can be a handicap. For the afflicted it appears to be a benefit.

 

[A. Neumaier]

I think we all are in the danger to be caught in our world views.

Did you ever consider that you might be caught in your own world view?

 

[vanhees71]

Of course, that's why I said "we all".