They certainly ought to constrain what would be considered credible.

Like after Darwin, you might quarrel about how humans arose from apes. But no longer do you need to worry about the mechanics of turning ribs into first wombs. — apokrisis

All I was saying is that however we might interpret QM the interpretation is a physical, not a metaphysical one, at least in the sense of not positing something transcendent at work. If by metaphysical all that is meant is ' something not directly observable", which might be better termed 'metaempirical' then fine.

So, the two chess claims below are both true:
1. The bishop moves diagonally
2. The bishop moves orthogonally — Banno

Anything goes then?

All I was saying is that however we might interpret QM the interpretation is a physical, not a metaphysical one, at least in the sense of not positing something transcendent at work. — Janus

If this is to be argument by definition, then I’m happy with the usual position that metaphysics is an inquiry into the nature and causes of being, Then as a debate, transcendence vs immanence is one of its familiar organising dichotomies,

do you think the Bohr-Einstein debates were about physics or metaphysics? — Wayfarer

It isn’t me that wants to make a sharp distinction here. I take the opposite view. Science is how we put metaphysical reasoning to the test.

It's something that comes up a lot in discussions. — T Clark

Really? It's an obscure bit of truth theorizing. Note the realists talk out of both sides of their mouths. :roll:

Really? It's an obscure bit of truth theorizing. — frank

Maybe it just comes up in a lot of my discussions.

my question is as to whether we can even sensibly speak of the multiverse in terms of being actual or not actual. Intuitively, of course, it seems we can; but if that's right then we do think that untestable conjectures can be true or false. — Janus

How can we talk about "multiverses" when multiverses are unknowable ?

It is the same problem that goes back to Kant's phenomenon and noumenon. Kant proposed that a phenomenon is a perceptive representation of an object existing in the mind of a perceiver, rather than the object in itself, the noumenon. Kant did not argue that the world of the noumenon does not exist, for there to be an appearance, there must be something for there to be an appearance of. It is just that human knowledge of the true nature of the noumenon is impossible, as the true nature of the noumenon is always mediated by the senses. In that, for example, we perceive the colour red, we don't perceive a wavelength of 700nm.

In this sense, all our beliefs are fictional, and every proposition we use is about a fictional object. When we ask, is the proposition "the multiverse exists" true or false, we are not referring to an unknowable entity in the world, but we are referring to a fictional entity "the multiverse". Similarly, when we ask, is the proposition "there is a table in front of me" true or false, whilst it is true that the parts that make up the table exist in the world and are knowable through the senses, the "table" as a whole, as a particular set of parts, only exists in the mind of the observer.

Therefore, complex objects such as "unicorns", "tables", "chairs", "mountains" and " multiverses" only exist in the mind in the imagination, and are therefore fictional. However, the fact that our all our beliefs are about fictional objects makes no pragmatic difference to our ability to exist within the world.

If I want a beer in a Tanzanian bar, all I need to know is to speak the symbol "bia moja tafadhali". I need know no more. I don't need to know the process of what happens between my speaking the symbol and my achieving my goal. The symbol "bia moja tafadhali" has no meaning in itself outside of any context it is used in. My speaking the symbol "bia moja tafadhali" in the context of a Tanzanian bar means that I will be given a beer. The symbol only has meaning within the imagination of the users, and is therefore fictive.

I may believe that "unicorns exist" is a fiction, but I don't know that unicorns don't exist. I may believe that "the multiverse exists" is a fact, but I don't know that multiverses do exist.

Even if unicorns, tables and multiverses must always remain unknowable, "unicorns", "tables" and "multiverses" can be knowable as fictive entities within the observer's imagination.

IE, in answer to your question, we can sensibly speak of the "multiverse", as what we are speaking of is a linguistic fiction, whether or not it is a fact in the world, and as a linguistic fiction can be either true or false.

It is the same problem that goes back to Kant's phenomenon and noumenon. Kant proposed that a phenomenon is a perceptive representation of an object existing in the mind of a perceiver, rather than the object in itself, the noumenon. Kant did not argue that the world of the noumenon does not exist, for there to be an appearance, there must be something for there to be an appearance of. It is just that human knowledge of the true nature of the noumenon is impossible, as the true nature of the noumenon is always mediated by the senses. In that, for example, we perceive the colour red, we don't perceive a wavelength of 700nm. — RussellA

I was going to say your analogy, comparing the multiverse to noumena, is not applicable, but I thought about it more. I think it is a good analogy. I started this thread to discuss things like the multiverse and my belief that, if I can't know, demonstrate, whether or not it exists, it's existence has no truth value or is meaningless.

I don't think you will find my solution to the issue satisfying - in my view, noumena don't exist either. They are just one way of looking at reality, similar to Lao Tzu's Tao and in contrast to the idea of objective reality.

I think it's a question of values.
— T Clark
I don't see how. — Banno

Would it make more sense to you if I changed "values" to "preference" or "taste?"

A small point of jargon. But important where folk are mostly arguing rhetorically. — apokrisis

I'm not sure "rhetoric" is the right word. They're not just trying to convince you of their position, they actually believe in the truth of what they say and are trying to present their position.

Anyway, the difference can be summed up that by saying the principle of bivalence is the logical claim that propositions are to be judged either true or false - true or not true. And a dialectical or dichotomous logic says that any "bivalent" division of metaphysical possibility has to obey the rule of being "mutually exclusive/jointly exhaustive". So to be "true", each has to stand as the logical negatation the other. Or to be more accurate, each has to be the formal inverse of reciprocal of the other. — apokrisis

…and are trying to present their position. — T Clark

That would be true if they make a positive and open minded argument for it. No problem there.

A small point of jargon. But important where folk are mostly arguing rhetorically.
— apokrisis

I'm not sure "rhetoric" is the right word. They're not just trying to convince you of their position, they actually believe in the truth of what they say and are trying to present their position.

Anyway, the difference can be summed up that by saying the principle of bivalence is the logical claim that propositions are to be judged either true or false - true or not true. And a dialectical or dichotomous logic says that any "bivalent" division of metaphysical possibility has to obey the rule of being "mutually exclusive/jointly exhaustive". So to be "true", each has to stand as the logical negatation the other. Or to be more accurate, each has to be the formal inverse of reciprocal of the other.
— apokrisis — T Clark

I posted this before I was finished by accident. Let's try again:

Although I agree with your point about how bivalence works, I think there is a place for it as long as you recognize that it is just a point of view, a choice, and not the fundamental basis of reality. I guess that's what you mean when you say:

Reductionism is fine too. It works really well if you want to build machinery or even mechanise human society and the human mind. Simple cause and effect thinking is neat little everyday tool of thought. — apokrisis

What do you think metaphysics ought to deliver as its social good? Does it have a purpose? I can't see any other reason to "do metaphysics" except to attempt to deduce the truth of reality from first principles ... and so set yourself up with clear hypotheses worth the effort of empirical test. — apokrisis

For me, there is no "truth of reality." There are lots of ways of seeing reality. You can choose the one that's most useful in a particular situation, then switch to a different one when the situation changes. I see philosophy, metaphysics, as a tool box. Pull out the right tool for the job.

Although I agree with your point about how bivalence works, I think there is a place for it as long as you recognize that it is just a point of view, a choice, and not the fundamental basis of reality. — T Clark

These are always “just models” that need to prove themselves pragmatically.

And I’ve said that reductionism and holism themselves are reciprocal points of view - a dichotomy - if understood correctly. I don’t reject one in favour of the other, but do then use each to sharpen the sense of the other.

You could consider that a disputable meta-metaphysical claim. I would be quite happy to defend it.

You could consider that a disputable meta-metaphysical claim. I would be quite happy to defend it. — apokrisis

I think you and I are in agreement.

Damn. :razz:

Would it make more sense to you if I changed "values" to "preference" or "taste?" — T Clark

I think there must have been some misunderstanding. You seem to have said that the truth value of the sentence given in my post is a question of taste. But that makes no sense. So you've lost me.

But how else to read this:

Seems to me we can assign "true" or "false" to the above sentence without contradiction, so the answer is "yes, there can be sentences that are true or false but undecidable".
— Banno

I don't agree, but I don't think we can resolve our differences. I think it's a question of values. — T Clark

But that makes no sense. — Banno

You wrote:

Seems to me we can assign "true" or "false" to the above sentence without contradiction, so the answer is "yes, there can be sentences that are true or false but undecidable". — Banno

I say - Whether or not you want to assign truth value to the referenced sentence is a matter of your choice, taste, value, preference. It's not a matter of fact. I, when I'm wearing my pragmatist boots, would say no. That would be a matter of my choice, taste, value, preference.

Whether or not you agree with that, it shouldn't be hard to understand.

Whether or not you want to assign truth value to the referenced sentence is a matter of your choice, taste, value, preference. It's not a matter of fact. — T Clark

There's something very odd happening here.

One more try, perhaps. You asked:

1) Can a statement be true or false if it is not possible to determine which it is, even in principle? — T Clark

I responded with:

"This statement is true or it is not possible to determine that this statement is true". — Banno

...pointing out that whether one assigns true or false to this sentence, it must be undecided, and hence it is a candidate for an example fo the sort of sentence you asked for.

There's nothing here about taste. Whichever you assign, true or false, the sentence is undecided.

Actually, on looking at it again, I wonder if we might do better. Consider my other suggestion:

"If it is not possible to determine that this statement is true then it is true"... — Banno

Assume a bivalent logic. Then this statement is either true or it is false.

If it is true then it is undecidable.

If it is false, then the antecedent is true, hence "it is not possible to determine that this statement is true" is true.

So in either case it is undecidable.

Of course if this is some kind of Gödelian move, I'm willing to get on board. — TheMadFool

Not unlike a Godel sentence, but with "decidable"" in the place of "provable". Where a Godel sentence is true but unproven, this sentence is presumably either true or false, but we can't decide which.

...pointing out that whether one assigns true or false to this sentence, it must be undecided, and hence it is a candidate for an example fo the sort of sentence you asked for. — Banno

If something's truth value is undecided that doesn't mean it isn't true or false, only that I don't know. On the other hand, if it's truth value is undecidable, I consider it either as having no truth value or as being meaningless.

I think we've gone far enough with this. I don't see that any more back and forth will bring us any closer to agreement.

If something's truth value is undecided that doesn't mean it isn't true or false, only that I don't know. — T Clark

Yep.

On the other hand, if it's truth value is undecidable, I consider it either as having no truth value or as being meaningless. — T Clark

Fine.

I think we've gone far enough with this. — T Clark

I answered your question and you get all huffy. Odd. OK, that'll do.

If this is to be argument by definition, then I’m happy with the usual position that metaphysics is an inquiry into the nature and causes of being, Then as a debate, transcendence vs immanence is one of its familiar organising dichotomies, — apokrisis

It's not so much argument by definition as it is a recognition that physics is not concerned with the transcendent (whatever that might be thought to be). Whatever physics is concerned with it is based on what has been observed or hypothesized based on the math. I don't see how "transcendence vs immanence" is relevant to debates about interpretations of QM.

How can we talk about "multiverses" when multiverses are unknowable ? — RussellA

We can talk about the multiverse because it is imaginable. I'm not sure whether you are referring to the cosmological hypothesis that our universe may be one "bubble" of spacetime among an infinitely numerous array of others, or the MWI explanation of the collapse of the wave function.

It doesn't matter anyway because either is imaginable as a possibility, but both would seem to be impossible to confirm or dis-confirm. The question is whether, since we cannot know the truth regarding these speculations, we should think they therefore cannot be true or false.

You say they are fictional, but we don't know that, because that would be to know that they don't exist. You could say that they might as well be fictional, since they cannot exist for us.

It doesn't matter anyway because either is imaginable as a possibility, but both would seem to be impossible to confirm or dis-confirm. — Janus

I was reading somewhere recently that some astronomers think it may be possible to look for evidence of multiverses associated with cosmic inflation by looking at anomalies in the cosmic microwave background. Can't remember where I saw that.

I don't see how "transcendence vs immanence" is relevant to debates about interpretations of QM. — Janus

All I was saying is that however we might interpret QM the interpretation is a physical, not a metaphysical one, at least in the sense of not positing something transcendent at work. — Janus

This is ridiculous. Here is what a competent philosopher says as something just taken for granted….

Quantum mechanics, like any physical theory, comes equipped with many metaphysical assumptions and implications. The line between metaphysics and physics is often blurry, but as a rough guide, one can think of a theory's metaphysics as those foundational assumptions made in its interpretation that are not usually directly tested in experiment.

https://link.springer.com/chapter/10.1007/978-3-540-70626-7_119

Quantum mechanics, like any physical theory, comes equipped with many metaphysical assumptions and implications. The line between metaphysics and physics is often blurry, but as a rough guide, one can think of a theory's metaphysics as those foundational assumptions made in its interpretation that are not usually directly tested in experiment.

If by metaphysical all that is meant is ' something not directly observable", which might be better termed 'metaempirical' then fine. — Janus

Discussion would be much better if you bothered to read what I wrote, rather than jumping to stupid conclusions about what I'm saying.

That's an interesting possibility. But then even regarding our accepted theories, if they can never be verified, for example if the theory that curvature of spacetime by mass, which we cannot observe, is responsible for gravitational effects, we are not justified in saying that relativity theory is true, but just that it works. But we do tend to think that it must be either true or false that spacetime is curved and that that curvature is responsible for observed gravitational effects.

Discussion would be much better if you bothered to read what I wrote, rather than jumping to stupid conclusions about what I'm saying. — Janus

Be huffy. But as Callender notes, it is not about what is or isn’t observed. The metaphysics grounds what even counts as the right kind of measurement.

If you feel your preferred jargon covers that, go for it. But it would be nice if you could supply a source to substantiate your implication that metaphysics and “metaempiricism” ain’t just synonyms here.

LOL, I'm not being "huffy". And I'm not saying the terms cannot be synonymous, in fact I'm saying they can and should be. I'm advocating a distinction between metaphysical as a synonym for metaempirical., and metaphysical as a synonym for supernatural, that's all.

There is a lot of "New Age" thinking that would seek to use the "observer problem" as justification for the notion that mind is, in some way apparently no one is able to coherently imagine, the foundation of reality.

That is a supernaturalist view, or an anti-naturalist view, if you prefer; it is the idea that there is a higher realm of mind or spirit that gives rise to what we, "down here", understand as a physical reality.

I'm advocating a distinction between metaphysical as a synonym for metaempirical., and metaphysical as a synonym for supernatural, that's all. — Janus

But who supports a definition of metaphysics as the study of the supernatural?

And when metaempirical is used as a term, it is about the wider epistemic reasons for believing in a theoretical framework rather than about the ontological presumptions that might motivate ideas about suitable experimental metrics.

So metaempirical justification for some line of physical inquiry might be Occam’s razor, or this way of thinking has worked for us before, or this way of thinking seems to produce more results than just the ones we were directly aiming for.

Metaphysics is indeed a broad brush label. But context would make it clear I was talking about ontic presuppositions that lay the ground for the actual business of making measurements. So for instance, whether you believe reality is made of particles or waves, whether you believe actions are local or nonlocal, etc.

The fact that New Age crackpots conflate two kinds of “mystery” - quantum collapse and the neuroscience of consciousness - is just one of those things. It has nothing to do with metaphysics and science as two fruitfully related academic disciplines … if you must treat them as clearly demarcated in the first place.

My vote: just spare us from the crackpots and their theories that can’t even past the first hurdle of “even being wrong”.

This is not intended to be a discussion about what constitutes justification. — T Clark

I understand that, but my point is that you cannot make any progress in answering the question if you are not clear on the criteria that the answer should satisfy. Without that the question is effectively meaningless (as you like to say).

Take interpretations of quantum mechanics, for example:

In my judgement, interpretations that are empirically indistinguishable are the same thing. Differences between them are meaningless — T Clark

Meaningless for you, because of the particular epistemic criteria that you set out for yourself in this case: if you can't put a proposition to an empirical test, then it is meaningless. (Not so for others, so they must be applying different criteria.)

Now, in the OP you want to turn the question onto that epistemic criterion itself. But that's clearly inapt: an epistemic criterion is not the sort of thing that you can test by the methods of science. You can see if it leads to contradictions or to unpalatable conclusions, but that's not the same thing.