My stance is that whether or not an entity is real is not a meta-level philosophical question, the way it is usually treated in the realism vs. anti-realism debates, but an object-level scientific question. Our scientific theories, interpreted literally, are committed to certain ontologies. MWI is quite clearly committed to the existence of something like a universal wave function, otherwise none of its explanations or purported merits make any sense. I also think (like David Wallace) that basic quantum theory, interpreted literally and without any ontological or epistemological add-ons, is committed to something like a universal wave function.
So I think that our best scientific theories should determine our ontology. As for which scientific theory to believe in, I think there are a number of different considerations that go into that—empirical confirmation, simplicity, concilience with the rest of our theories, feritility (in terms of useful predictions), etc.
My beef with instrumentalism is that it is, in a sense, too philosophical. It treats the reality or unreality of the unobservable entities posited by our best theories as a further question, one not determined by the theories themselves. Even once we have accepted, say, quantum mechanics as true, the instrumentalist says there is a further question about whether to take its claims literally or to treat them as mere calculational tools for making predictions. My take is that there is no further question. Accepting quantum mechanics as true, or believing in quantum mechanics, implies accepting the theory as a guide to reality. If you’re unwilling to do that, you need to tell me why. If your standards for determining what really exists are so high that not even our best-confirmed scientific theories can meet them, then I suspect you’re working with a concept of “reality” that I, as a pragmatist, have no use for (and can’t even really understand).
OK, so your approach is something like “QM has wave function as a basic description, therefore wave function is real if QM is true”? And if QED requires virtual particles to calculate anything useful, then virtual particles “exist”, and are not a mathematical artifact of the perturbation theory?
Even once we have accepted, say, quantum mechanics as true, the instrumentalist says there is a further question about whether to take its claims literally or to treat them as mere calculational tools for making predictions.
If that’s what instrumentalism is, then I am most definitely not an instrumentalist. To me “accepting QM as true” is a meaningless statement, while “QM is accurate (at explaining and predicting) and fertile (making lots and lots of interesting, useful and accurate predictions)” is a meaningful one.
If your standards for determining what really exists are so high that not even our best-confirmed scientific theories can meet them, then I suspect you’re working with a concept of “reality” that I, as a pragmatist, have no use for (and can’t even really understand).
I would agree with that, assuming I had “standards for determining what really exists”, which I don’t. To me everything imaginable exists to the same degree, just in different contexts, be it stars, photons, baseballs, unicorns, thoughts, ghosts or numbers. Which makes the concept of existence so loose as to be meaningless. So I don’t see any use for it. If you say that this (obvious to me) approach does not fit neatly to some existing (heh) ontology, I would be quite surprised,
OK, so your approach is something like “QM has wave function as a basic description, therefore wave function is real if QM is true”? And if QED requires virtual particles to calculate anything useful, then virtual particles “exist”, and are not a mathematical artifact of the perturbation theory?
Yeah, I believe virtual particles exist. I also believe in the existence of things like phonons, the electromagnetic field, organisms, beliefs and prices. These are all ontological posits of the best theories of the particular domain. I don’t think that there is a meaningful sense in which some of these things are more real than others. Unlike you, I don’t think unicorns or ghosts exist to any degree, because they are not part of our best theory of the relevant domain. I’m not even sure how to think about degrees of existence.
To me “accepting QM as true” is a meaningless statement, while “QM is accurate (at explaining and predicting) and fertile (making lots and lots of interesting, useful and accurate predictions)” is a meaningful one.
From a pragmatist point of view, there isn’t much distance between those two statements. Pragmatists (myself included) reject the correspondence theory of truth.
Interesting, thank you. I guess our views are not that far apart. And I also
don’t think that there is a meaningful sense in which some of these things are more real than others.
though if someone comes up with an interesting, accurate and fruitful meta-model of partial existence, I’d be happy to change my mind.
I don’t think unicorns or ghosts exist to any degree, because they are not part of our best theory of the relevant domain.
Could it be because you are trying to apply them to a wrong domain? Would you agree that in a certain setting (a fantasy tale, a horror story) we can predict behavioral and visual features of the creatures inhabiting it with a fair degree of accuracy? Often more accurately than, say, a path and strength of a tropical storm being born in the Atlantic.
Would you agree that in a certain setting (a fantasy tale, a horror story) we can predict behavioral and visual features of the creatures inhabiting it with a fair degree of accuracy? Often more accurately than, say, a path and strength of a tropical storm being born in the Atlantic.
Yeah, but what we’re using there is a theory of literary and mythological tropes. Those tropes certainly exist, and can be used to predict features of various books and movies. But I think it’s misleading to characterize this as unicorns or ghosts existing. When people ordinarily say things like “I believe ghosts exist”, they’re not referring to predictable patterns in horror stories. I can tell you some things about what the world would be like if ghosts existed, and the world isn’t that way.
If all you mean is that ghosts exist in certain fictional universes, then sure, they do. If someone asks me “Do ghosts exist in Middle Earth?” I’d say “Yes”. If someone asks me “Do ghosts exist?” I’d say “No”.
When people ordinarily say things like “I believe ghosts exist”, they’re not referring to predictable patterns in horror stories. I can tell you some things about what the world would be like if ghosts existed, and the world isn’t that way.
Right. When you extrapolate a model beyond its domain of validity, in this case from stories to the physically perceived world, the predictions of ghost models tend to fail pretty badly. So when people argue about what exists and what does not, all I see is “domain confusion”.
I’m not at all sure what you mean when you say that all you see is “domain confusion”. Do you mean that people in these arguments are talking past each other because they are each talking about different domains? Because I’m pretty sure that is not true in general. Or do you mean that people who say, for example, that ghosts exist are saying this because they are illegitimately extrapolating a theory that works in one domain into another? I don’t think this is true in general either. Or do you mean something else?
Just to clarify: When, in ordinary circumstances, you encounter a debate between two people about whether ghosts exist, do you think one of them is right and the other is wrong?
Or do you mean that people who say, for example, that ghosts exist are saying this because they are illegitimately extrapolating a theory that works in one domain into another?
Yes.
When, in ordinary circumstances, you encounter a debate between two people about whether ghosts exist, do you think one of them is right and the other is wrong?
Usually yes, since people rarely argue whether ghosts exist in mythology. But a discussion about whether numbers exist is almost always a confusion about domains, since numbers exist in the mind, just like ghosts.
Not sure what you are saying. My guess is that you are implying that the quotation is not the referent, and unicorns are hypothetical magical creatures, while “unicorns” are vivid and very real descriptions of them in the stories often read and written by the local bronies. If so, then all I have to say that unicorn is not an accurate or fertile theory, while “unicorn” most definitely is. The difference is the domain of validity: can you go outside and find one running around, or can you mostly encounter them in books and movies? But that applies to most theories. If you go slow, Newtonian mechanics is adequate, if you study fast-moving objects, Newton gives bad predictions. Similarly, if you apply the predictions of the “unicorn” model beyond the domain of its validity, you are going to be disappointed, though occasionally you might discover a new applicable domain, such as a cosplay or a SFF convention.
The distinction is that a theory of “unicorns” is a theory that describes how and why other people (and probably you yourself) think about unicorns, while a theory of unicorns would explain actual unicorns. The latter would clearly fail as a theory, because you’re never going to actually see a unicorn.
The same distinction doesn’t apply to Newtonian mechanics, because Newtonian mechanics is a theory of mechanics, not a theory of how people think about mechanics.
On those grounds, I think it’s quite reasonable to say that virtual particles are real, and “unicorns” are real, but unicorns are not real.
The same distinction doesn’t apply to Newtonian mechanics, because Newtonian mechanics is a theory of mechanics, not a theory of how people think about mechanics.
On those grounds, I think it’s quite reasonable to say that virtual particles are real, and “unicorns” are real, but unicorns are not real.
Not sure if you read anything I wrote in this thread. Note that both Newton’s laws and “unicorn” laws are models. You don’t find Newton’s laws in Nature, just like you don’t find “unicorn” laws. You don’t find virtual particles, either, as they are but terms in the perturbative expansion of a particular quantum field theory (which is also a model, and not found in the wild).
My stance is that whether or not an entity is real is not a meta-level philosophical question, the way it is usually treated in the realism vs. anti-realism debates, but an object-level scientific question. Our scientific theories, interpreted literally, are committed to certain ontologies. MWI is quite clearly committed to the existence of something like a universal wave function, otherwise none of its explanations or purported merits make any sense. I also think (like David Wallace) that basic quantum theory, interpreted literally and without any ontological or epistemological add-ons, is committed to something like a universal wave function.
So I think that our best scientific theories should determine our ontology. As for which scientific theory to believe in, I think there are a number of different considerations that go into that—empirical confirmation, simplicity, concilience with the rest of our theories, feritility (in terms of useful predictions), etc.
My beef with instrumentalism is that it is, in a sense, too philosophical. It treats the reality or unreality of the unobservable entities posited by our best theories as a further question, one not determined by the theories themselves. Even once we have accepted, say, quantum mechanics as true, the instrumentalist says there is a further question about whether to take its claims literally or to treat them as mere calculational tools for making predictions. My take is that there is no further question. Accepting quantum mechanics as true, or believing in quantum mechanics, implies accepting the theory as a guide to reality. If you’re unwilling to do that, you need to tell me why. If your standards for determining what really exists are so high that not even our best-confirmed scientific theories can meet them, then I suspect you’re working with a concept of “reality” that I, as a pragmatist, have no use for (and can’t even really understand).
OK, so your approach is something like “QM has wave function as a basic description, therefore wave function is real if QM is true”? And if QED requires virtual particles to calculate anything useful, then virtual particles “exist”, and are not a mathematical artifact of the perturbation theory?
If that’s what instrumentalism is, then I am most definitely not an instrumentalist. To me “accepting QM as true” is a meaningless statement, while “QM is accurate (at explaining and predicting) and fertile (making lots and lots of interesting, useful and accurate predictions)” is a meaningful one.
I would agree with that, assuming I had “standards for determining what really exists”, which I don’t. To me everything imaginable exists to the same degree, just in different contexts, be it stars, photons, baseballs, unicorns, thoughts, ghosts or numbers. Which makes the concept of existence so loose as to be meaningless. So I don’t see any use for it. If you say that this (obvious to me) approach does not fit neatly to some existing (heh) ontology, I would be quite surprised,
Yeah, I believe virtual particles exist. I also believe in the existence of things like phonons, the electromagnetic field, organisms, beliefs and prices. These are all ontological posits of the best theories of the particular domain. I don’t think that there is a meaningful sense in which some of these things are more real than others. Unlike you, I don’t think unicorns or ghosts exist to any degree, because they are not part of our best theory of the relevant domain. I’m not even sure how to think about degrees of existence.
From a pragmatist point of view, there isn’t much distance between those two statements. Pragmatists (myself included) reject the correspondence theory of truth.
Interesting, thank you. I guess our views are not that far apart. And I also
though if someone comes up with an interesting, accurate and fruitful meta-model of partial existence, I’d be happy to change my mind.
Could it be because you are trying to apply them to a wrong domain? Would you agree that in a certain setting (a fantasy tale, a horror story) we can predict behavioral and visual features of the creatures inhabiting it with a fair degree of accuracy? Often more accurately than, say, a path and strength of a tropical storm being born in the Atlantic.
Yeah, but what we’re using there is a theory of literary and mythological tropes. Those tropes certainly exist, and can be used to predict features of various books and movies. But I think it’s misleading to characterize this as unicorns or ghosts existing. When people ordinarily say things like “I believe ghosts exist”, they’re not referring to predictable patterns in horror stories. I can tell you some things about what the world would be like if ghosts existed, and the world isn’t that way.
If all you mean is that ghosts exist in certain fictional universes, then sure, they do. If someone asks me “Do ghosts exist in Middle Earth?” I’d say “Yes”. If someone asks me “Do ghosts exist?” I’d say “No”.
Right. When you extrapolate a model beyond its domain of validity, in this case from stories to the physically perceived world, the predictions of ghost models tend to fail pretty badly. So when people argue about what exists and what does not, all I see is “domain confusion”.
I’m not at all sure what you mean when you say that all you see is “domain confusion”. Do you mean that people in these arguments are talking past each other because they are each talking about different domains? Because I’m pretty sure that is not true in general. Or do you mean that people who say, for example, that ghosts exist are saying this because they are illegitimately extrapolating a theory that works in one domain into another? I don’t think this is true in general either. Or do you mean something else?
Just to clarify: When, in ordinary circumstances, you encounter a debate between two people about whether ghosts exist, do you think one of them is right and the other is wrong?
Yes.
Usually yes, since people rarely argue whether ghosts exist in mythology. But a discussion about whether numbers exist is almost always a confusion about domains, since numbers exist in the mind, just like ghosts.
Ah, but then you’re talking about a theory of “unicorns” rather than a theory of unicorns.
Not sure what you are saying. My guess is that you are implying that the quotation is not the referent, and unicorns are hypothetical magical creatures, while “unicorns” are vivid and very real descriptions of them in the stories often read and written by the local bronies. If so, then all I have to say that unicorn is not an accurate or fertile theory, while “unicorn” most definitely is. The difference is the domain of validity: can you go outside and find one running around, or can you mostly encounter them in books and movies? But that applies to most theories. If you go slow, Newtonian mechanics is adequate, if you study fast-moving objects, Newton gives bad predictions. Similarly, if you apply the predictions of the “unicorn” model beyond the domain of its validity, you are going to be disappointed, though occasionally you might discover a new applicable domain, such as a cosplay or a SFF convention.
The distinction is that a theory of “unicorns” is a theory that describes how and why other people (and probably you yourself) think about unicorns, while a theory of unicorns would explain actual unicorns. The latter would clearly fail as a theory, because you’re never going to actually see a unicorn.
The same distinction doesn’t apply to Newtonian mechanics, because Newtonian mechanics is a theory of mechanics, not a theory of how people think about mechanics.
On those grounds, I think it’s quite reasonable to say that virtual particles are real, and “unicorns” are real, but unicorns are not real.
Not sure if you read anything I wrote in this thread. Note that both Newton’s laws and “unicorn” laws are models. You don’t find Newton’s laws in Nature, just like you don’t find “unicorn” laws. You don’t find virtual particles, either, as they are but terms in the perturbative expansion of a particular quantum field theory (which is also a model, and not found in the wild).
Anyway, disengaging now.