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

[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.

 

[gentzen]

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?

This is a tricky one, because those equivalence classes risk to reduce the usefulness of an ontology. On the other hand, sometimes equivalence classes are unavoidable in a strong sense. But one point of studying ontology is actually to identify such situations.

In a certain sense, the equivalence classes similar to many-one reductions are unproblematic, but those similar to Turing reductions are risky.

 

[Jarvis323]

so we can derive the force from there...

Is there an assumption that there are no separate yet correlated properties in nature?

 

[Killtech]

This is a tricky one, because those equivalence classes risk to reduce the usefulness of an ontology. On the other hand, sometimes equivalence classes are unavoidable in a strong sense. But one point of studying ontology is actually to identify such situations.

Just asking because if you cannot separate representation from the object being represented, you risk rendering making the the representation the real thing rather what the object it represents. I would find that weird.

 

[Killtech]

Is there to be an assumption that there are no separate yet correlated properties in the nature?

Sounds like you are talking QT. If a quantity is uniquely determined by another, this question isn't relevant. Correlation on the other hand always implies a certain type of dependence. If you assume something is sepererable, then you have to specify what that means and Bell's factorization is one type of separation. And it yields his inequality. Strongest separation is that of independence which implies null correlation.

 

[Jarvis323]

Just asking because if you cannot separate representation from the object being represented, you risk rendering making the the representation the real thing rather what the object it represents. I would find that weird.

Not necessarily. In a more macroscopic picture at least, we can think of lots of physical objects in which we can know some properties of some object from observing another, even though those different properties are different real things.