I Is GRW theory an interpretation of quantum mechanics or a rival theory?

[Killtech]

Even in pure math, if I say "The set exists", no mathematician will ask me to define "The", to define "set" or to define "exists"

Hmm, well Bourbaki would disagree as their starting point in discussing mathematics was... we need to define the word "set" first before we can talk anything else. Also "exist" implies the prior is well defined. There was enough discussion in mathematical logic to what that means so everyone could start on the same page. But fair point, frequently used worlds in mathematical language like "the" or "let" and alike are never formally defined.

1. In classical mechanics, the particle position as a function of time x(t) is ontic. Its Fourier transform x~(ω) is not ontic.
2. In classical mechanics, anything that can directly be derived from x(t) is ontic

These two statements sound like a contradiction to me?

The meaning of "directly" also has to be learned through examples. For instance, the velocity x˙(t) and acceleration x¨(t) are directly derived from x(t). The momentum p(t)=mx˙(t) and the force F(x) are not directly derived from x(t).

I'd rather say that would be a convention. I don't think classical mechanics states what is ontic or not. You could just as well assume the momentum is ontic instead of the velocity.

Think of it this way: if you had to code a simulation of classical mechanics, then all the objects that your application will store in RAM memory could be considered ontic (their information exists in a very direct way). In this scenario, you will find there are very many possible implementations that yield the same simulation and each uses very different convention of what to make ontic. And you can either save the velocity or momentum in memory - or you could take both, which however is likely to run into consistency bugs, so it's better not to have such redundancy.

In principle any minimal implementation could decide to store any (bijective) transformations of the quantities you described above as it's fundamental objects it deals with - instead of what you called ontic. If we really lived in the Matrix as in the films, how would you really know it's not implemented via Fourier transforms of everything? Don't make the mistake of common sense: it is merely a representation of our primary perception (our eyes) and the neural net in our brain to process the data from it. So if you would question blind people you may very easily encounter a different common sense then yours. In particular, they will probably perceive momentum as much more impactful then velocity.

From those examples, one can use intelligent extrapolation to determine whether many other concepts in classical physics are ontic or not. (But in some cases it may not be obvious, so we may have have different interpretations of classical physics. That's particularly true in the theory of relativity.)

I don't think you can uniquely attribute concepts like "ontic" to a quantity in general due to the problem above. You require some additional convention to fix it. Consider choice of ontic quantities being like a specification of coordinates for your theory. That analogy shows the problem: any choice works.

 

[gentzen]

I think @Demystifier will disagree. To me it seems that for him it is very important that momentum is not ontic.

Fine, maybe he will disagree. Perhaps he has good reasons why. I would first have to hear them, before I consider changing my opinion. To me it seems that for him, being able to use words like ontic, ontology, ontologial, or nomological (or rather the concepts corresponding to those words) and be properly understood is what is very important. My impression is that he uses momentum just as an example to clarify his understanding of those words.

Invariant mass is still just a constant.

But for the non-relativistic approximation, the invariant mass is not helpful, neither for Newton's law of gravitation, nor for the relation between velocity and momentum.

 

[Fra]

As mass is somehow confined energy in space, "reconstructing" a mass concept properly first needs a proper reconstruction of both space and energy concepts. And constructing space from distinguishable events, would involve both some embedding dimensionality and a metric.

If we think of the $x(t)$ as the basic kinematical variables, maybe this is the logic of Demystifier?

Mass would instantly bring us into dynamics, which is a more complex matter.

Even in my abstract agent interpretation, the set of distinguishable events, is the absolute most basic thing. But next up, one wants to construct various counts and measures of this, to form "expectations", and one then soon find that one needs to introduce a concept of "amount of evidence" ~ memory, that effectively works as an "inertia" in the information revision process.

/Fredrik

 

[Fra]

Invariant mass is still just a constant.

This is one of the problem of mathematical models, a lot of things are just empirical "parameters". These you tune/calibrate = determine experimentally. But once one starts to ask what is the origin of mass (ie what determines the VALUES of the "parameters"), then one needs a deeper grip of things to add explanatory value. Like what is the conceptual function of mass? What we know is that it relates to inertia and gravitation, so we apparently need to understand intertia and gravitation to get deeper.

/Fredrik

 

[Demystifier]

If we think of x(t) the as the basic kinematical variables, maybe this is the logic of Demystifier?

Yes.

 

[Demystifier]

Hmm, well Bourbaki would disagree as their starting point in discussing mathematics was... we need to define the word "set" first before we can talk anything else.

Offtopic, but what's their definition of set? I think set in set theory is primitive, i.e. cannot be defined precisely in terms of something more elementary. There are axioms (ZF) of set theory, but they don't tell what a set is.

 

[Minnesota Joe]

From those examples, one can use intelligent extrapolation to determine whether many other concepts in classical physics are ontic or not. (But in some cases it may not be obvious, so we may have have different interpretations of classical physics. That's particularly true in the theory of relativity.)

When one grasped the meaning of "ontic" in classical physics, one can start to think and talk about "ontic" in quantum physics.

What about time in $x(t)$ and $\phi(x,t)$? Is time considered ontic?

 

[Killtech]

Offtopic, but what's their definition of set? I think set in set theory is primitive, i.e. cannot be defined precisely in terms of something more elementary. There are axioms (ZF) of set theory, but they don't tell what a set is.

Sets are defined in an axiomatic way, but it is a definition. Algebraic objects (groups, rings, fields, ...) are usually defined in a similar fashion. What you mean is that sets are not constructed out of something else and that is true. There is the {} symbol notation to define set expressions which does not have it's own rigorous definition i think, though all elements one can use there are logical symbols and "element of" relation. It however allows you to write down Russels paradox. Generally the expressions that are not enough to satisfy being sets yet well defined to accept them anyway are named classes.

So sets are logical expressions that additionally satisfy set theory axioms. the "element of" relation is implicitly defined along with sets by the same axioms.

Sets therefore initiate the transition from logical expressions to working with mathematical objects. But each mathematical object still represents a very lengthy list of logical expression that define it. Elements of a set inherit a huge part of that list allowing for a very handy notation to say so much about a thing by writing so little (maths are lazy). And that makes us not think of it in such a way and perceive it as an actual object.

Hmm, as such set theory maybe allows for an analogy: It is similar in function to a C++ compiler (or other language) that allows us to write higher language code that is nicely understandable for humanes but that still evaluates to a very nasty assembler / machine language expressions composed of only very elemental/basic operations so the code still can be evaluated by simple Touring machines.

 

[Fra]

What about time in $x(t)$ and $\phi(x,t)$? Is time considered ontic?

I would say no.

As I see it, in classical mechanics and in the basic kinematics, t is just a parameter in the model, that serves the purpose of indexing the order of events. Other than that, time is not something you can observe in itself. The only way to distinguish $t_{1}$ from $t_{2}$ is by means of some change, which is a measure defined in terms of some various $x$ (as that is the basics).

If one starts to question the metric in the time dimension, I think it's again is getting more complex.

From an abstract agent perspective of $x_{t}$ as just a set of distinguishable events, the $x$ are in my view just LABELS. ie. there is no intrinsic justification for imaginig a continuum of these events. It's easy to intuitively think of $x$ as real numbers. But in the reconstruction, they are to me nothing by labels. The continuum is something that needs motivation. Same with the index $t$, it's initially just an index defining and ORDER of the events. NO need to jump into thinking about a continuum as distinguishable events as something that makes sense. In fact I think there is a lot that would speak against this.

So the embedding of these lables into the continuum mathematics, is practical but I think can fool us. We are dressing things up, witout justification, and then forgets about what are the core and what's just a gauged dresssing.

/Fredrik

 

[gentzen]

Generally the expressions that are not enough to satisfy being sets yet well defined to accept them anyway are named classes.

So sets are logical expressions that additionally satisfy set theory axioms. the "element of" relation is implicitly defined along with sets by the same axioms.

I would say that Demystifier is right, both with "Offtopic" and with "set in set theory is primitive, ... There are axioms (ZF) of set theory, but they don't tell what a set is". For example, an inaccessible cardinal is a set, but there are no logical expressions that could define a specific inaccessible cardinal.

 

[Killtech]

There are axioms (ZF) of set theory, but they don't tell what a set is". For example, an inaccessible cardinal is a set, but there are no logical expressions that could define a specific inaccessible cardinal.

I'm not sure what you mean by "what a set is"? What isn't clear about a set from the axioms? Well, okay, in terms of ontology as the question of "what is", sets aren't made for this purpose, so they don't define a relation for such questions. But i am not aware of any definitions in math that handle it... so no different to any other objects in math.

not sure what you mean by a specific inaccessible cardinal set. Cardinality number of the real numbers can be written by a set and therefore represents a logical expression for it. Sure it's most probably not complete enough to decide all kind of statements about (like AC or NAC) it but it is a definition. The class of all cardinal numbers i think isn't a set but a class. Even so, it's still well defined but that definition will leave even more statements about it undecided.

 

[Jarvis323]

I would say no.

As I see it, in classical mechanics and in the basic kinematics, t is just a parameter in the model, that serves the purpose of indexing the order of events. Other than that, time is not something you can observe in itself. The only way to distinguish $t_{1}$ from $t_{2}$ is by means of some change, which is a measure defined in terms of some various $x$ (as that is the basics).

If one starts to question the metric in the time dimension, I think it's again is getting more complex.

From an abstract agent perspective of $x_{t}$ as just a set of distinguishable events, the $x$ are in my view just LABELS. ie. there is no intrinsic justification for imaginig a continuum of these events. It's easy to intuitively think of $x$ as real numbers. But in the reconstruction, they are to me nothing by labels. The continuum is something that needs motivation. Same with the index $t$, it's initially just an index defining and ORDER of the events. NO need to jump into thinking about a continuum as distinguishable events as something that makes sense. In fact I think there is a lot that would speak against this.

So the embedding of these lables into the continuum mathematics, is practical but I think can fool us. We are dressing things up, witout justification, and then forgets about what are the core and what's just a gauged dresssing.

/Fredrik

Intuitively, based on my limited understanding, the set of ontic mathematical objects in any dynamical theory should be sufficient to recover the state spaces of the systems.

 

[gentzen]

I'm not sure what you mean by "what a set is"? What isn't clear about a set from the axioms? ... But i am not aware of any definitions in math that handle it... so no different to any other objects in math.

not sure what you mean by a specific inaccessible cardinal set. Cardinality number of the real numbers can be written by a set and therefore represents a logical expression for it.

Even if you don't believe me, your questions have answers, at least answers which are accepted in certain communities. (Those communities don't especially like the Bourbaki treatment of set theory.) However, I would say this is offtopic here. There is a Set Theory, Logic, Probability, Statistics Forum. If you want, we can discuss it there.

 

[PeterDonis]

not sure what you mean by a specific inaccessible cardinal set.

It's a topic that belongs in the math forum on set theory, not here:

https://en.wikipedia.org/wiki/Inaccessible_cardinal

 

[PeterDonis]

There is a Set Theory, Logic, Probability, Statistics Forum. If you want, we can discuss it there.

Yes, please take discussion of set theory to a separate thread in that forum. It is off topic here.

 

[Demystifier]

What about time in $x(t)$ and $\phi(x,t)$? Is time considered ontic?

Good question! I would say yes, but in relativistic physics that's debatable.

 

[A. Neumaier]

I guess now we would need a new thread entitled "Learning the word "feels"", because obviously this word cannot be defined precisely.

Well, it is learned by osmosis... The human body responds to forces in a similar way as the spring; no qualia are needed!
The point is that forces are more real than position, and hence qualify more as being ontic, according to your defence of why position is ontic.

 

[Demystifier]

The point is that forces are more real than position, and hence qualify more as being ontic, according to your defence of why position is ontic.

I think you took one of my defences out of the context.

 

[A. Neumaier]

I think you took one of my defences out of the context.

Well, you said that you ''see position'' (though in fact you don't) to justify its ontic-ness. I didn't see a context that would remove the force of the argument (if it woukd have applied).

But I guess the real reason you consider position as ontic is because it is needed for Bohmian mechanics...

 

[Demystifier]

Well, you said that you ''see position'' (though in fact you don't) to justify its ontic-ness. I didn't see a context that would remove the force of the argument (if it woukd have applied).

The context is that it was only one in a series of hand-waving arguments, neither of which is sufficiently convincing by itself.

But I guess the real reason you consider position as ontic is because it is needed for Bohmian mechanics...

Actually, it's the other way around. The idea that position is ontic in classical mechanics is much older, from which Bohmian mechanics looks like a natural extension.

 

[Minnesota Joe]

Actually, it's the other way around. The idea that position is ontic in classical mechanics is much older, from which Bohmian mechanics looks like a natural extension.

Given this interesting information and given the Dürr and Teufel quote in post #21, I have another question if you don't mind. They wrote: "They must be there: a particle theory without particle positions is inconceivable." [emphasis mine]

If I take that claim literally, they are stating a necessary condition to have a particle theory. That seems to imply that "ontic" is the name for this relationship of necessity and that would explain why it is narrower than "real".

But that also seems to imply that what fixes the ontic quantities is what you take to be real in the first place (e.g. particles or fields or...)

What do you think of this?

 

[martinbn]

Actually, it's the other way around. The idea that position is ontic in classical mechanics is much older, from which Bohmian mechanics looks like a natural extension.

This is what you want, not necessarily what is. That's why your arguments are not convincing. You started with the conclusion (that you wish to be true) and then you try to find support for it.

You still haven't answered some of my questions. For example what is the ontology in classical field theory?

 

[Demystifier]

But that also seems to imply that what fixes the ontic quantities is what you take to be real in the first place (e.g. particles or fields or...)

What do you think of this?

Yes, but it's relative to a theory. Late Durr would say that you can't have a physical theory if you have not fixed what is your theory about. For instance, if you propose a speculative theory of unicorns, then, within the theory, unicorns are treated as ontic.

 

[Demystifier]

For example what is the ontology in classical field theory?

A field, e.g. scalar field $\phi(x,t)$. (In gauge theories it's a bit more complicated.)

 

[Demystifier]

This is what you want, not necessarily what is. That's why your arguments are not convincing. You started with the conclusion (that you wish to be true) and then you try to find support for it.

Suppose that you don't know what "beauty" means, so I try to explain it to you through an example. For example, cat is beautiful and cockroach isn't. Would you object that this is what I want, not necessarily what is? If you would you would miss the point, because the point is only to explain what the beauty means, not to decide which animals are beautiful and which aren't.

Or perhaps you have a better way to explain what "beauty" means?

And if you have no idea how is that related to "ontic", then you missed the point of the entire thread.

 

[martinbn]

Yes, but it's relative to a theory. Late Durr would say that you can't have a physical theory if you have not fixed what is your theory about. For instance, if you propose a speculative theory of unicorns, then, within the theory, unicorns are treated as ontic.

Then in the classical particle theory, it is the particles that are ontic.

A field, e.g. scalar field $\phi(x,t)$. (In gauge theories it's a bit more complicated.)

Which one? What if there are more than one way of describing the physical field in terms of mathematical fields? In classical electrodynamics what is ontic, $E$, $B$, $H$, $D$, $F_{\mu\nu}$,...?

 

[martinbn]

Suppose that you don't know what "beauty" means, so I try to explain it to you through an example. For example, cat is beautiful and cockroach isn't. Would you object that this is what I want, not necessarily what is? If you would you would miss the point, because the point is only to explain what the beauty means, not to decide which animals are beautiful and which aren't.

Or perhaps you have a better way to explain what "beauty" means?

And if you have no idea how is that related to "ontic", then you missed the point of the entire thread.

My problem is that you are not discussing like a scientist. You are not interested in finding things out. You are discussing like a member of school debate team. You simply want, through rhetoric, to present the best possible argument to support your position. You don't really care what is ontic or not, what you care about is how to make your case, which is BM is the way to go. As I said, I am probably wrong, but that's how it seems to me, and that's why I find it dificult to follow your reasoning. By the way is there anyone, who is not a BM supporter, who finds your arguments convincing?

 

[Demystifier]

Then in the classical particle theory, it is the particles that are ontic.

Yes. And the mathematical object that most directly represents the particle is $x(t)$. Unless you know an even better mathematical object, in which case I am ready to revise my claim above.

In classical electrodynamics what is ontic, $E$, $B$, $H$, $D$, $F_{\mu\nu}$,...?

In the theory before relativity theory, it was $E$ and $B$. In the modern relativistic version it's $F_{\mu\nu}$.

 

[Demystifier]

As I said, I am probably wrong, but that's how it seems to me, and that's why I find it dificult to follow your reasoning. By the way is there anyone, who is not a BM supporter, who finds your arguments convincing?

I believe that most supporters of ontic interpretations of QM would find my arguments convincing. This includes supporters of many worlds and objective collapse (GRW), who would not agree that particle positions are ontic in QM (and which I don't even claim in this thread), but would agree that particle positions are ontic in classical mechanics. That's because they understand what ontic means. On the other hand, supporters of non-ontic interpretations (shut up and calculate, Copenhagen, minimal statistical, QBism, relational, ...) have problems with understanding what ontic means, and contrary to my hopes, it seems that this thread does not help them much.

 

[Demystifier]

My problem is that you are not discussing like a scientist.

My problem is that there is no scientific definition of "ontic", so I must use more basic methods of teaching new words, through examples like in kindergarden.

 

[Minnesota Joe]

I believe that most supporters of ontic interpretations of QM would find my arguments convincing. This includes supporters of many worlds and objective collapse (GRW), who would not agree that particle positions are ontic in QM (and which I don't even claim in this thread), but would agree that particle positions are ontic in classical mechanics. That's because they understand what ontic means. On the other hand, supporters of non-ontic interpretations (shut up and calculate, Copenhagen, minimal statistical, QBism, relational, ...) have problems with understanding what ontic means, and contrary to my hopes, it seems that this thread does not help them much.

Well, if it's any consolation, it also helps kindergarteners like me who are trying to learn about physical theories in quantum foundations!

 

[PeterDonis]

It's compatible with common sense and basic intuition.

I don't think I agree. If an object hits me and knocks me off my feet, it's not the object's position that did it, it's the object's momentum. If I focus sunlight on a leaf with a magnifying glass and set the leaf on fire, it's not the position of the sunlight that did it, it's the sunlight's energy. If I put two objects in the two pans of a balance and watch what happens, it's not the positions of the two objects that determines what the balance does, it's their masses.

So my intuition says that all of those things are "ontic". Which may just mean that my preferred meaning of "ontic" is different from yours; but that just raises the question of why I should care about yours.

 

[TeethWhitener]

My problem is that there is no scientific definition of "ontic", so I must use more basic methods of teaching new words, through examples like in kindergarden.

There’s a philosophical distinction here that makes this assertion problematic. It seems like you’re saying that “ontic” has an extension (there is a list of things that are ontic) but not an intension (that list of ontic things might have nothing else in common with each other than simply being ontic).

The problem here is when we ask how the term ontic is any more useful than a made-up term like blergian. Typically, the usefulness of a term comes in its intension. Consider a famous example: analytic functions vs holomorphic functions. The two terms have the same extension (all and only analytic functions are holomorphic) but not the same intension (“analytic” does not mean the same thing as “holomorphic”). So without an intensional definition of ontic, it just seems like ontic is an arbitrary list.

 

[Demystifier]

I don't think I agree. If an object hits me and knocks me off my feet, it's not the object's position that did it, it's the object's momentum. If I focus sunlight on a leaf with a magnifying glass and set the leaf on fire, it's not the position of the sunlight that did it, it's the sunlight's energy. If I put two objects in the two pans of a balance and watch what happens, it's not the positions of the two objects that determines what the balance does, it's their masses.

So my intuition says that all of those things are "ontic". Which may just mean that my preferred meaning of "ontic" is different from yours; but that just raises the question of why I should care about yours.

I said basic intuition. Trained physicists have good intuition about momentum, energy and mass, but most people on the street don't. Yet all people have intuition about object's position. I can easily imagine a non-human civilization that did not develop concepts analog to our momentum, energy and mass, but I cannot easily imagine that such a civilization did not develop a concept analog to our position.

If I wanted to be more dramatic, perhaps I would even dare to paraphrase Kronecker by saying: God created positions, all else is the work of man.

 

[vanhees71]

I think this thread proves by empirical evidence that "ontic" is a completely irrelevant property, because it's not defined at all what it means. All that's relevant is what's observable, and all you need for a theory is that describes the observable facts (usually within a limited realm of applicability) correctly.

 

[Demystifier]

and all you need for a theory is that describes the observable facts

No, that's all what you need. As for ontic, some physicists need it, some don't.

 

[PeterDonis]

I said basic intuition. Trained physicists have good intuition about momentum, energy and mass, but most people on the street don't.

I disagree. I think the ordinary person on the street would understand the things I wrote about the real world effects of momentum, energy, and mass just fine, and would consider your claim that those things are not "ontic" to be daft. Your arguments about why position alone should be ontic are not based on "basic intuition", but on complicated physical theories that took centuries to develop and many expensive experiments to confirm.

 

[Demystifier]

I think this thread proves by empirical evidence that "ontic" is a completely irrelevant property, because it's not defined at all what it means.

People need a lot of concepts that are not defined at all. I already mentioned the concept of "beauty". Even in your sentence above, the words "I", "think", "irrelevant" and many others are not defined at all.

 

[Demystifier]

I disagree. I think the ordinary person on the street would understand the things I wrote about the real world effects of momentum, energy, and mass just fine, and would consider your claim that those things are not "ontic" to be daft. Your arguments about why position alone should be ontic are not based on "basic intuition", but on complicated physical theories that took centuries to develop and many expensive experiments to confirm.

OK, another try! I hope we all know what's the difference between kinematics and dynamics:
http://www.differencebetween.info/difference-between-kinematics-and-dynamics
What if I define ontic objects as objects that are studied by kinematics?

 

[physika]

One cubic metre of iron has more mass than one cubic metre of plastic. Explain that intuitively!

...well, space (volume) is not mass !

rather M=E/C²

.

 

[gentzen]

My problem is that you are not discussing like a scientist. ... You are discussing like a member of school debate team. You simply want, through rhetoric, to present the best possible argument to support your position.

I think this thread proves by empirical evidence that "ontic" is a completely irrelevant property, because it's not defined at all what it means.

OK, another try!

My own approach would be try to avoid "discussing like a member of a school debate team". This means that I should at least acknowledge the questions I did not address yet, even if some questions would be challenging for me to answer (satisfactory).

Say we then move on to the theory of relativity. Now we think about what is ontic again, and we have our commen sense picture that assigns physical meaning. We will have a new meaning of ontic as well. Does it matter if the common sense picture we have now contradicts the one we had with classical physics?

Our common sense picture needs to be right? Or is just an exersize, and/or for comfort, or entertainment?

Now we do the same in QT. Because QT is supposed to describe the microscopic world on a fundamental level, ontic now has more weight? We are talking again just about common sense pictures of the mathematical objects with the same motivation and goal? Or, if we assumed that QT were the complete lowest level description of reality, does this imply that what is ontic in QT is absolutely real? This is what I don't understand the most, what is the end game. If we prove QT is complete, and we prove A is ontic in QT, then we've proven something about the true physical meaning and existence of A?

I do have an opinion on some of those questions, but me trying to answer those questions would (probably) not help.

 

[physika]

I guess now we would need a new thread entitled "Learning the word "feels"", because obviously this word cannot be defined precisely.

Alternatively, to avoid a use of that word, I would say that the spring "just" moves the way it moves and a regularity of this motion can be described by an abstract mathematical quantity we call force.

..."feel", it's just figurative language.

Action-Reaction, Newton.
it doesn't just move, it interacts.
.

 

[physika]

Yes, but it's relative to a theory. Late Durr would say that you can't have a physical theory if you have not fixed what is your theory about. For instance, if you propose a speculative theory of unicorns, then, within the theory, unicorns are treated as ontic.

Sorry,
Treated, but not ontic...

Ontic (from the Greek ὄν, genitive ὄντος: "of that which is") is physical, real, or factual existence.

But that also seems to imply that what fixes the ontic quantities is what you take to be real in the first place (e.g. particles or fields or...)

Maybe both, particles as excitations of the fields.

.

 

[PeterDonis]

What if I define ontic objects as objects that are studied by kinematics?

You would still have to claim that "kinematics" only includes position, which is debatable. And then you would have to claim that, while things that change are "ontic" (kinematics), the things that cause them to change are not (dynamics). Which, again, does not seem to be a "basic intuition" that an ordinary person in the street would have.

 

[physika]

OK, another try! I hope we all know what's the difference between kinematics and dynamics:
http://www.differencebetween.info/difference-between-kinematics-and-dynamics
What if I define ontic objects as objects that are studied by kinematics?

.
maybe fated to fail...

The paradigm of kinematics and dynamics must yield to causal structure.​

https://arxiv.org/abs/1209.0023#

"The distinction between a theory's kinematics and its dynamics, that is, between the space of physical states it posits and its law of evolution, is central to the conceptual framework of many physicists. A change to the kinematics of a theory, however, can be compensated by a change to its dynamics without empirical consequence, which strongly suggests that these features of the theory, considered separately, cannot have physical significance. It must therefore be concluded (with apologies to Minkowski)
that henceforth kinematics by itself, and dynamics by itself, are doomed to fade away into mere shadows,
and only a kind of union of the two will preserve an independent reality."

.

 

[Jarvis323]

I think this thread proves by empirical evidence that "ontic" is a completely irrelevant property, because it's not defined at all what it means. All that's relevant is what's observable, and all you need for a theory is that describes the observable facts (usually within a limited realm of applicability) correctly.

I think the property of being ontic is irrelevant when restricting your universe to one painted by a particular incomplete theory (although not irrelevant as a topic of discussion, since it forces us to try to be more clear about what we think). We know that there is some "onticness" underneath classical physics, because classical physics has predictive power. But it doesn't necessarily mean that any specific mathematical objects in the theory are ontic in the sense that both the theory treats that object as fundamental/irreducible, and that object is fundamental or irreducible in nature. So pointing to this property and that property is misleading, because you can only do that within the universe of the theory. Yet here we are reaching outside of that theory into our own mental models to try and figure out what we think is real in the universe spanned by the theory and our own abstract knowledge. If we go that far, then there is no point in not spanning our entire set of scientific theories. So it is pointless to thinking about ontic in a specific theory unless that theory really completes the picture and we don't need intuition or any outside of the box thinking, only derivation. QT, supplemented with evidence from classical theory might be a foundation for thinking about what is ontic, yet still we have too shaky a formalization of QT to be clear about ontology in QM, and we have no language to connect QT and classical theory. So currently the best we can do is use our understanding of the entire universe of theory, and try to guess which direction of future work to do in an attempt to fill in what is missing. That's my opinion at least.

Even though I realize that ontology in QT in general is probably not knowable in the sense I imagine we want it to be. Rather, it should be that we have some clear formalization of QT that we can rely on in the larger universe of spanning all scientific theory consistently and then we can say what is ontological in an intuitive sense in the consistent global picture. This might be thinking in the spirit of coherentism. Actually I think in the discussion about what is ontic, we are being sort of selective coherentists, and not being clear that we are being coherentists as we try to use our intuition/abstract knowledge and infer meaning from past experience and word usage.

Rather than conceiving the structure of our knowledge on the model of Euclidean geometry, with its basic axioms and derived theorems, these epistemologists favor a holistic picture of justification which does not distinguish between basic or foundational and non-basic or derived beliefs, treating rather all our beliefs as equal members of a “web of belief” (Quine and Ullian 1970, cf. Neurath 1983/1932 and Sosa 1980).

https://plato.stanford.edu/entries/justep-coherence/#CohVerFou

However, I personally have doubts about there existing an accessible coherent language that could give us a theory of everything. It may be that such a language is infinite, or uncomputable.

 

[martinbn]

In the theory before relativity theory, it was $E$ and $B$. In the modern relativistic version it's $F_{\mu\nu}$.

$E$ is force on unit charge. So forces are ontic after all.

 

[Killtech]

Yes. And the mathematical object that most directly represents the particle is $x(t)$. Unless you know an even better mathematical object, in which case I am ready to revise my claim above.

In the theory before relativity theory, it was $E$ and $B$. In the modern relativistic version it's $F_{\mu\nu}$.

I feel that such a choice is strangely specific and yet arbitrary.

Let's query something else first and ask what about $E(x)$ and $E(x')$ or some unit transformation multiplying some additional constants? All of them are equivalently describing the very same thing, yet are different in the explicit expression. Does the "ontic" stuff acknowledge that the objects of interest don't ever appear in a raw naturally unique form but there is always a layer of representation and convention of top such that you can never assign a property to one thing but always have to think of an equivalence class of closely related quantities?

 

[gentzen]

$E$ is force on unit charge. So forces are ontic after all.

$E$ being ontic is less problematic than force being ontic, because $E$ exists in space and time. The force resulting from Newton's law of gravity on the other hand does not have an independent existence in space and time, but can only exist where the particle position already exists. Therefore the particle position is the primary ontology in that case, and force is only one of many possible secondary variables.

This existence in space and time is precisely one of the reasons why ontology with respect to "physical existence" has a slightly different character from ontology with respect to "mathematical existence". The "intuitive notion" of something which exists physically normally implies that it exists at some time and at some point, or at least in some region of space and time. This is one reason why the wavefunction should better not be ontic.

 

[Killtech]

E being ontic is less problematic than force being ontic, because E exists in space and time. The force resulting from Newton's law of gravity on the other hand does not have an independent existence in space and time, but can only exist where the particle position already exists. Therefore the particle position is the primary ontology in that case, and force is only one of many possible secondary variables.

Good point. Newtowns force does not hold any additional information about the system at all. Since it is instantaneous knowing the particle position and its mass we have all information we need so we can derive the force from there. Thus the force field itself merely holds redundant information.

Due to the Maxwell equations however this is different for $E$. The information stored there is irreducible and any theory of classical e-dyn losing it won't be able to make correct predictions.