## The role of observers in MWI

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As opposed to what? A world at thermodynamic equilibrium?

Yes. Since there are more ways to be high entropy than low entropy we should have more worlds with high entropy than low. So why are we in a low entropy world if it is very statistically unlikely?

Some version of the past hypothesis, right? But then seeing a world where the past hypothesis is true is vanishingly unlikely, even if it occurs with probability 1, according to MWI derivations of the Born Rule.

I am surprised that you went for this explanation, given what you said above about frequentist explanations. This is a textbook case where statistics does not apply because it simply does not exist.

Your reasoning applies to an ergodic system that has been evolving for a long time, or an equivalent ensemble. But the early universe is nothing like that. If there is no explanation for the past hypothesis (we don't have a good theory of the universe's origin), then it makes no sense to talk about how likely or unlikely it is, because the universe was and still is far from ergodic, it hadn't been evolving for a long time (ex hypothesi), and we don't have an ensemble (unless some kind of a multiverse theory is true, but that is still very speculative, so we can't take it as given).

It seems to me that either low probability events should always be surprising and make us ask questions or they never should, not a too cute mix of both. Just bite the bullet and say the Born Rule is meaningless, a total illusion, in that case.

Eh, surprise is a tricky thing. There have been some detailed analyses of surprise in the literature, both from the purely epistemological standpoint and specifically in the context of issues like the multiverse and fine-tuning. But I find that in the latter case the arguments get too far afield. They start from some careless analogies (e.g. Leslie's firing squad) and then get bogged down in the arguments over the analogies. Given that our everyday intuitions are not trained for such exotic scenarios as multiverses, we probably shouldn't put too much stock in them.
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I am surprised that you went for this explanation, given what you said above about frequentist explanations. This is a textbook case where statistics does not apply because it simply does not exist.

Frequentism seems fine in some contexts, or at the very least, it is at times much easier to explain things in that frame when it doesn't make a material difference. A closer look would indeed show problems with my example. If you accept determinism at all levels of reality, then of course there is only one way a system can evolve, the very way it does evolve, and entropy has to be framed as somehow subjective, or at least relational. The problem with frequentism IMO is that it is generally the only way of understanding probability theory that is taught, and is incoherent when applied to some situations.

Your reasoning applies to an ergodic system that has been evolving for a long time, or an equivalent ensemble. But the early universe is nothing like that. If there is no explanation for the past hypothesis (we don't have a good theory of the universe's origin), then it makes no sense to talk about how likely or unlikely it is, because the universe was and still is far from ergodic, it hadn't been evolving for a long time (ex hypothesi), and we don't have an ensemble (unless some kind of a multiverse theory is true, but that is still very speculative, so we can't take it as given).

You are correct about the nature of the Past Hypothesis; that's a fine answer, but it isn't the argument I get frustrated with. By definition, there are more ways to be in a high entropy state than a low entropy state. Perhaps there is indeed a mechanism at work in the early universe that makes a later low entropy state counterintuitively more likely than a high entropy one. But, barring support for that fact, we are left with the principal of indifference, and this suggests that we weight all options equally, combinatorially if there are a finite number of states. That is, giving equal likelihood to all potential universes of X mass energy existing in an early state with all possible levels of entropy, the high entropy universes outnumber the low entropy ones, barring some other sort of explanation. Appeals to the Anthropic Principle don't address this. The same issue comes up with the Fine Tuning Problem; if we don't know the likelihood of values for constants, indifference should prevail.

If this is the case, then it remains that high entropy states outnumber low entropy ones, and remain more likely.

Positing some as of yet not understood mechanism by which this is not the case is fine, after all, we have empirical evidence that the entropy of the early universe was low (counterintuitively despite being near equilibrium, wrapping your head around negative heat is a doozy). The problem I was addressing is using the Anthropic Principle to address this rather than any appeals to the probability of any observation of the state of the early universe. This is where the problem of triviality comes up.

I think this is a similar problem to that of claims that "everything is explainable in terms of fundemental physics," and then appealing to the black box, brute facts of initial conditions as the origin of many of the most interesting things we'd like the natural sciences to explain. I think the proper response here is: "yes, but we want to know how the particular initial conditions in our past led to X and Y, etc. historically, and if this cannot be explained without appeals to brute facts for a vast array of all natural phenomena, then nature does not reduce to fundemental physics in terms of explanations."
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we lack for vocabulary since ‘measurement’ and ‘physics’ are both human undertakings and apparently cannot be used for interactions not involving humans.
What do you call the actual mechanisms of the universe, as opposed to ‘physics’, the human undertaking to describe it? What would you call an interaction between systems of which humans are completely unaware, say where one system (some radioactive atom) emits an alpha particle which alters a second system (some molecule somewhere) by altering its molecular structure (and probably heating up the material of which the molecule is part). It isn’t a measurement because there’s no intent and no numerical result yielded, so what word describes this exchange between the atom and the molecule?

You’re asking for a description of the world that is not described by physics. Such an undertaking would fall under the general heading of metaphysics, wouldn't it?

The definition of counter-factual definiteness I provided was generated by ChatGPT. Granted, ChatGPT is no all-knowing oracle, but I felt it to be a reasonable summary.

Alternatively, you perhaps suggest an epistemological definition of counter-factual definiteness, where in the absence of human measurement/observation, humans would not know of the thing, and existence is defined by human knowledge of it. Hence, again, by definition, nothing can exist in the absence of humans since no human could know of it. Counter-factual definiteness is therefore false either way.

Correct me where I’ve misinterpreted what you’ve been trying to tell me.

Grappling with the distinctions you're providing between various types of interpretation is quite a challenge - not that there's anything wrong with them, but there's a lot to take in, and I think you're better read in them than I am. But there is probably more detail in those diverse interpretations than is required by the broadly idealist view that I'm trying to advocate. Which is that - whatever we construe existence to be, it contains a mental or subjective pole or aspect, which is not in itself disclosed amongst the objects of scientific analysis. From a naturalistic perspective, it is perfectly sound to presume that the laws and objects of physics obtain independently of any observer, but the lesson of quantum physics is that this is not ultimately so, but that the observer retains a central role. And why this is, is not itself a scientific question, but a metaphysical one.

One of the text books I've been consulting on this is Nature Loves to Hide, Shimon Malin. He advocates an idealist interpretation which he says is consistent with Western philosophy (unlike the other authors on this subject who appeal to Eastern philosophy. You can find a profile of Malin here).

Then the measurement takes place and a "collapse" occurs giving a particular solution. Did the measurement "do something" to the system, or does one simply experiment to find the appropriate value of the constant? Where is the magic?

That is indeed the measurement problem in a nutshell. The act of observation is not described by the equations but appears central to the outcome. That is what the many-worlds interpretation seeks to explain away. But nobody has a definitive or unanimous solution - hence the debate!
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You’re asking for a description of the world that is not described by physics.
No, I’m asking for vocabulary that you would accept in describing parts of the world that are not in a laboratory or anywhere else where attention is being paid by some human.
— noAxioms
The definition of counter-factual definiteness I provided was generated by ChatGPT. Granted, ChatGPT is no all-knowing oracle, but I felt it to be a reasonable summary.
I found it quite reasonable. I wasn’t speaking of that, I was speaking of your definition of ‘measurement’, ‘physics’ and such, all those words that you refuse to apply to a case where a human isn’t involved.
Counter-factual definiteness is therefore false either way.
There are valid interpretations that hold to the principle. It has never been falsified, but of course neither has it been proven.
From a naturalistic perspective, it is perfectly sound to presume that the laws and objects of physics obtain independently of any observer
This statement contradicts your assertion that the word ‘physics’ implies a human endeavor and thus cannot ‘obtain independently of any observer’. It seems that you use the word that way, but refuse to let me do it.
One of the text books I've been consulting on this is Nature Loves to Hide, Shimon Malin. He advocates an idealist interpretation which he says is consistent with Western philosophy (unlike the other authors on this subject who appeal to Eastern philosophy. You can find a profile of Malin here).
There is undeniably an element of idealism in a relational view. I might find a copy of this worth reading, but cannot accept anything where the operation of the universe is different for humans than it is for anything else. I doubt it goes there.
The act of observation is not described by the equations but appears central to the outcome. That is what the many-worlds interpretation seeks to explain away.
I think that’s what all the interpretations try to explain, or ‘explain away’ if you happen to disapprove of the way it was explained.

1) The world appears different to us, depending on the perspective we take.
2) The world is different from different points of view.
Kindly give examples of each so I get a clue as to what you’re attempting to convey. The second one seems pretty obvious. The stop sign appears red from the front, but from the rear (a different point of view) it isn’t. From a realist position, the stop sign is not different due only to this difference of perspective, but it appears different. I don’t know what you mean by the first one, a different perspective that isn’t a different point of view, hence my request for an example. OK, I think maybe the apple thing below is such an example, but unclear if it illustrates point 1 or 2.
The former is realist, as assuming a true way that things are, independent of the various perspectives.
OK, maybe I’m confusing your usage of both, and my stop sign example was a difference of perspective, in which case I need an example of a different PoV that isn’t a different perspective. Point of view usually means appearance from some specific location in space, but you seem to be using the term differently.
None of this seems to have anything to do with relativity theory.

And the problem is that to apply relativity theory, and make it work for us, we need to assume the latter. Since that position is adopted for the purpose of applying relativity theory, we cannot make the results derived from the application of relativity theory compatible with the realist assumption of a real independent world.
You seem to be attempting to mix theories of two very different things. Relativity theory isn’t different depending on one’s realism stance on quantum theory and works pretty much the same either way.
Consider "an apple hanging from a tree". That's one way of describing the scenario, it's a static scenario, though "hanging" is still a verb. But we could also describe it as a whole bunch of different molecules with atoms interacting, and the gravity of the earth interacting with the massive molecules, putting immense force on the stem, until with ripeness, the atomic and molecular interactions change considerably, and the apple falls.
Notice, the former is a very simple description, as a static state, it takes no account of the passing of time, except for the word "hanging". The latter description makes an attempt to account for the effects of time passing, by describing the scenario in terms of activity.
This is what I am talking about.
OK, but it wasn’t what I was talking about. Is there a point then? The apple is open to different descriptions. I don’t disagree with any of it, but it’s all still just descriptions. The actual physical system isn’t any different due to your choice of description, unless I suppose if you’re proposing some sort of reality that supervenes on language. Anyway, is this what you mean by ‘different point of view’?
This question is answered with "the passing of time".
No. A system in isolation will remain in superposition indefinitely, so it isn’t time that ‘does something’.
The wave function in quantum mechanics evolves deterministically according to the Schrödinger equation as a linear superposition of different states.
— ”Wiki: Measurement problem
This "deterministic" evolution of the wave function is completely a feature of the type of description employed. It is described so as to be deterministic, when in reality, this description, the "superposition of different states", violates the law of noncontradiction, showing that this deterministic description is actually very faulty.
There’s no violation. MWI essentially posits exactly that: that the wave function evolves deterministically and there is no collapse, and no contradiction.
I discussed this principle in another thread with a number of participants. Suppose there is a jar with marbles in it. The marbles can be counted and this will determine the quantity. The others argued that the quantity is already determined, prior to the counting. The quantity is a "pre-existing property".
Marbles in a jar is a classical system, and yes, the count of them is fixed before they’ve been counted. At the quantum level, which is what Bell was talking about, these things are not necessarily true.
You were arguing that "here" constitutes a frame. If you still can't admit to the fault in this, I really don't see the point to continuing.
If I said that, it would be faulty, yes. You should include my quote then.
And "metric" doesn't imply "coordinate system" to you, in this context, such that a coordinate system is a logical necessity for a metric?
No coordinate system was specified, so one isn’t necessary when specifying a metric as I did, one relative to which the velocity of anything can be expressed, despite the lack of coordinates.
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I’m asking for vocabulary that you would accept in describing parts of the world that are not in a laboratory or anywhere else where attention is being paid by some human.

And I'm saying, it's not a matter of vocabulary. The question is one of metaphysics.

From a naturalistic perspective, it is perfectly sound to presume that the laws and objects of physics obtain independently of any observer - Wayfarer
This statement contradicts your assertion that the word ‘physics’ implies a human endeavor and thus cannot ‘obtain independently of any observer’. It seems that you use the word that way, but refuse to let me do it.

What I'm saying is, that from the perspective of natural philosophy, it is perfectly sound to presume....etc. What I'm arguing is that naturalism presumes that the world would exist, just as it appears to us, even without there being an observer - and that, for pragmatic purposes, this is a sound assumption. But quantum physics challenges that assumption because it calls the purported mind-independent nature of reality into question. That's what the debate is about!

I...cannot accept anything where the operation of the universe is different for humans than it is for anything else.

You still require that we can arrive at a description of a truly mind-independent reality.
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Lots of interesting comments there. I'll focus on the Born rule for the moment.

I don't have these same concerns, but I think it is important than many proponents of MWI do list similar concerns about other theories in quantum foundations.

Yes, fair point.

MWI aside, the puzzle is whether the observed probabilities can be derived without positing the Born rule. The basic approach (borrowing from Carroll and Sebens, Zurek, and others) is to use two alternative rules.

1. The indifference rule: If the amplitudes for the terms in a quantum state are equal, assign the same probability to each term such that they sum to 1.
2. The reduction rule: If the amplitudes are unequal, reduce the state to terms with equal amplitudes. Then apply the indifference rule.

Now those rules may be thought to be equivalent to positing the Born rule. However they aren't mysterious in the way that the Born rule seems to be.

For example, consider a qubit in the state:

$|\psi\rangle = \sqrt{\frac{1}{3}}|0\rangle + \sqrt{\frac{2}{3}}|1\rangle$

Since the amplitudes are unequal, the reduction rule is applied. The reduced state is:

$|\psi_r\rangle = \sqrt{\frac{1}{3}}|0\rangle + \sqrt{\frac{1}{2}}(\sqrt{\frac{2}{3}}|1_a\rangle + \sqrt{\frac{2}{3}}|1_b\rangle) = \sqrt{\frac{1}{3}}|0\rangle + \sqrt{\frac{1}{3}}|1_a\rangle + \sqrt{\frac{1}{3}}|1_b\rangle$

Since the amplitudes are now equal, the indifference rule is applied. There are three states, so the probability for each state is 1/3 which gives 1/3 for the $|0\rangle$ state and a total of 2/3 for the reduced $|1\rangle$ states, which matches the Born rule when applied to $|\psi\rangle$.

That's an operational derivation that bypasses issues about uncertainty, what probabilities "really are", and any reference to MWI.

If the physics in question is reversible, why do we posit a splitting universe instead of a merging one, aside from the fact that having it split in both directions (forwards and backwards in time) is incoherent?

Perhaps whenever we make a measurement we merge universes, such that we progress by such merges to one of many potential end points, final conditions, of the universe, assuming ad hoc that it has an end? This might work, but it blows up the rational-agent based derivations of the Born Rule. Rational agent models are not reversible, we don't say, "given what I observe now, what must have happened in the future, what endpoint must I be most likely to be converging on?"

As it happens, David Deutsch describes both splitting and merging in his version of the Wigner's friend thought experiment (for which reversibility is relevant). See an earlier thread here.

The principle is really just an extrapolation from what is observed on the microscopic scale. Cast in quantum computing terms, qubits and quantum logic gates are reversible. Applying a Hadamard gate to a computational basis state splits it into an equal superposition state, and applying a Hadamard gate again merges the superposition back to the original state. So the question is whether that process scales up to the everyday, macroscopic level. And, if so, whether or how that should affect our reasoning.
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The wave function in quantum mechanics evolves deterministically according to the Schrödinger equation as a linear superposition of different states. However, actual measurements always find the physical system in a definite state. Any future evolution of the wave function is based on the state the system was discovered to be in when the measurement was made, meaning that the measurement "did something" to the system that is not obviously a consequence of Schrödinger evolution
— ”Wiki: Measurement problem

...

There are an infinite number of solutions depending upon that constant (measurement) - a superposition. Then the measurement takes place and a "collapse" occurs giving a particular solution. Did the measurement "do something" to the system, or does one simply experiment to find the appropriate value of the constant? Where is the magic?

To apply your example, consider the double-slit experiment. When there is no measurement at either slit, the originally emitted particles build up an interference pattern on the back screen. That pattern can be described by a linear superposition of each particle going through the left slit plus each particle going through the right slit, i.e.:

$|\psi\rangle = \frac{1}{\sqrt{2}}(|left\rangle + |right\rangle)$

Suppose, instead, that there is a measurement at the slits. The originally emitted (and measured) particles no longer build up an interference pattern. The particles measured at each slit subsequently end up on the back screen as described by the $|left\rangle$ and the $|right\rangle$ terms independently, and not as described by $|\psi\rangle$.

That outcome is not obviously a consequence of (continuous) Schrödinger evolution. So it seems that the measurements "did something" to the system.

Compare to an ocean wave that might be described as a linear superposition of simpler waves. In that case, observing or measuring the wave doesn't affect the system.
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I didn't want to further detail the thread, so I started a new discussion: The Past Hypothesis: Why did the universe start in a low-entropy state?
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No, I’m asking for vocabulary that you would accept in describing parts of the world that are not in a laboratory or anywhere else where attention is being paid by some human.

Describing something requires paying attention to it. How do you think that someone could describe a part of the world which has no one paying attention to it? You are asking for the impossible, what is excluded by contradiction.

OK, maybe I’m confusing your usage of both, and my stop sign example was a difference of perspective, in which case I need an example of a different PoV that isn’t a different perspective. Point of view usually means appearance from some specific location in space, but you seem to be using the term differently.
None of this seems to have anything to do with relativity theory.

Yes, you seem very confused as to what I was trying to say. I did not express it very well, so we better forget about that. It's very apparent that you have a completely different idea about what relativity theory says from what I do.

Relativity theory isn’t different depending on one’s realism stance on quantum theory and works pretty much the same either way.

It isn't the case that relativity theory is different depending on one's realism stance, but it is the case that a true realism cannot be maintained in the application of relativity theory.

Consider that within any system of formal logic, one must maintain consistency with the axioms. Any premise not consistent with the axioms cannot be employed because it would cause contradiction and incoherency. Take what you said above for example. Axiom: to be described requires that the thing described be observed. If we now proceed with the premise that we can describe something which has not been observed, we'll run into some incoherency.

Realism is not consistent with relativity. Refer back to Galileo's initial development of relativity theory. His point was to show that the orbits of the planets could equally be represented by the geocentric model, or the heliocentric model. By relativity theory each model is equally correct, there is no such thing as the "real" representation. That each representation, or description, is equally correct, and they are contradictory to each other, is the reason why relativity is not consistent with realism. Are you familiar with "model-dependent realism". This is an attempt to make relativity theory consistent with realism, but it isn't a form of realism at all. It just borrows the word "realism", assuming itself to be the closest thing to realism which we can get under the precepts of relativity theory.

The actual physical system isn’t any different due to your choice of description...

Yes it is different. The actual physical system is as described, and the descriptions differ. That's the point. There is no axiom which allows us to say that the physical system is different from what is described, because that would imply that the description is wrong. And, the descriptions differ according to one's choice of description. Therefore the actual physical system is different depending on one's choice of description. For more information read about model-dependent realism.

If you are a hard core realist, there is an escape from this trap. The escape is to realize that relativity theory is not truthful. What it says about the world is a falsity, and we just use it as a useful tool, but the tool is not a truth. Then we can reject model-dependent realism as just a manifestation of relativity theory, and we can maintain a true realism.

Marbles in a jar is a classical system, and yes, the count of them is fixed before they’ve been counted. At the quantum level, which is what Bell was talking about, these things are not necessarily true.

What Bell is saying, is that this idea, that the number of marbles in the jar is fixed, prior to the count is a misleading idea. The quantity of marbles, the number which corresponds with the physical situation, is only determined through a judgement. So the idea, that the number is fixed, prior to the count is a false idea.

Think about this. If the number is fixed, prior to the count, then it is necessary that nothing changes in the meantime, the time between the fixing and the count. If it is even possible that something could change, then we cannot say that the number is fixed. So we tend to think along the lines of Newton's law of inertia, and we figure that a force would be required to change things, so if the jar is watched in the meantime, we'd see if a marble was added or removed. Therefore if we exclude all the ways that we deem are possible ways that the quantity could change, then we can say that the number is fixed. But what if we do not apprehend all the possible ways, and there's other ways, what a physicalist might call "magic" or something like that. The proper conclusion therefore, is to recognize that the number is not actually fixed prior to the count, because there is always some logically possible way that it could change in the meantime. The idea that the number is fixed prior to the count, is just another useful tool that is not the truth about the situation.
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Suppose, instead, that there is a measurement at the slits

Does this measurement physically affect a photon on its way to the far screen?
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And I'm saying, it's not a matter of vocabulary.
It is a matter of vocabulary. You denied my saying that the moon existed relative to a rock because I used words you feel can only be used for human intentful actions. I cannot discuss a metaphysical view that isn’t based on human intent.

What I'm arguing is that naturalism presumes that the world would exist, just as it appears to us, even without there being an observer and for pragmatic purposes, it is a sound assumption.
I mostly agree with that. But firstly, naturalism does not necessarily imply objective realism even though most of the time it does. Your comment was worded using the language of realism.
More importantly, while the world may exist, absent an observer, it wouldn’t ‘appear’ at all. It can be described, but it wouldn’t have an appearance. I think you cover this point with the pragmatic bit. I am for instance attempting a pragmatic description of a quantum interaction between a radioactive nucleus and some molecule a ways off. I attempt to leave off descriptions of how they would appear.
But quantum physics challenges that assumption.
I don’t see how it does anymore than say Newtonian physics which equally wasn’t different when human intent or observation was involved than when not.
You still require that we can arrive at a description of a truly mind-independent reality.
Yes, but that’s pretty easy. It gets tricky (not impossible) when you attempt a truly mind-independent description of reality, but I suppose you would deny it being possible by the anthropocentric restrictions you place on vocabulary, where any description made by something not human is by definition not a description, even when discussing non-anthropocentric metaphysics.

It isn't the case that relativity theory is different depending on one's realism stance, but it is the case that a true realism cannot be maintained in the application of relativity theory
What is ‘true realism’ as distinct from realism? Does it mean something more significant than ‘my personal opinion’?
.
Take what you said above for example. Axiom: to be described requires that the thing described be observed.
I didn’t say any such thing. For instance, I described a stop sign, all without either of us observing it. Had you never seen a stop sign, perhaps the description would have needed to be more thorough, but no reason it cannot be done.
[Galileo's i] point was to show that the orbits of the planets could equally be represented by the geocentric model, or the heliocentric model. By relativity theory each model is equally correct
Both correct, but not equally. The physics of a rotating accelerating frame is not the same as a different kind of frame, so they’re not equal. The frames are abstractions. The abstractions are different (not equal), but both refer to the exact same reality, so they’re not wrong in that sense.
That each representation, or description, is equally correct, and they are contradictory to each other, is the reason why relativity is not consistent with realism.
That one abstract system describes my baguette as about 61 cm and another as about 2 feet is not a contradiction, just a different abstraction. I think the physics community would have noticed by now if there were contradictions between different abstractions of the exact same thing.
I can even take different perspectives and notice that the baguette had a longish silhouette but from the end the same thing appears circular, a contradiction you say. You’ve actually been pushing that fallacious example for years. No actual contradiction has been identified.
Are you familiar with "model-dependent realism".
It seems a form of reality supervening on models instead of the other way around. The baguette is skinny and long. The baguette is circular. Both are equally valid. Something like that.

There is no axiom which allows us to say that the physical system is different from what is described, because that would imply that the description is wrong.
But the baguette being circular and skinny-long are not wrong descriptions, but neither are they complete. Neither fully describes the thing. Models are inherently simplifications. I’m not sure how model-dependent reality deals with that part.

Think about this. If the number is fixed, prior to the count, then it is necessary that nothing changes in the meantime, the time between the fixing and the count. If it is even possible that something could change, then we cannot say that the number is fixed.
Right. It was fixed, but then before they were counted, somebody goes and adds a handful more. It has changed, so it was a mistake to say the first time that it was fixed. Where’s the controversy? The actual number of marbles in the jar has nothing to do with somebody’s knowledge of the count. The latter is epistemology, and the judgement only serves epistemology. Watching it doesn’t make it stay fixed or not. Watching it only makes it somewhat more likely that the watcher knows if the number is changing or not, all of which is irrelevant to the actual count. Point still is, it’s a classical system that does not exhibit quantum behavior. None of your comment seem to suggest otherwise.
But what if we do not apprehend all the possible ways, and there's other ways, what a physicalist might call "magic" or something like that. The proper conclusion therefore, is to recognize that the number is not actually fixed prior to the count
It does not matter what is counted. What matters is how many marbles are in there. I’m discussing metaphysics, not acquisition of information. The number is what it is, and if by some means marbles are added or removed, then that number changes. At no point is the jar in superposition of having different numbers in it. That’s why it’s a classical system.
because there is always some logically possible way that it could change in the meantime.
I never denied that marbles can be added or removed. There’s no particularly logical necessity that such changes can’t happen. It happens frequently to a typical cookie jar.

Does this measurement physically affect a photon on its way to the far screen?
All measurements of anything physically affect the thing measured.

The which-slit detection need not actually convey which-slit information. They put polarizing filters at the slits and this can destroy the superposition (it constitutes a measurement) without actually conveying to anything which actual path the photon took. The vanishing of the interference pattern is the effect. And one photon cannot create a pattern. Only repeated iterations do.
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The explanation of uncertainty as arising through the unavoidable disturbance caused by the measurement process has provided physicists with a useful intuitive guide as well as a powerful explanatory framework in certain specific situations. However, it can also be misleading. It may give the impressions that uncertainly only arises when we lumbering experimenters meddle with things. This is not true. Uncertainty is built into the wave structure of quantum mechanics and exists whether or not we carry out some clumsy measurement. ...Since the wave is uniformly spread throughout space, there is no way for us to say the electron is here or there. ...And this conclusion does not depend on our disturbing the particle. We never touched it. Instead it relies on a basic feature of waves - they can be spread out. — Brian Greene, The Fabric of the Cosmos

You denied my saying that the moon existed relative to a rock because I used words you feel can only be used for human intentful actions.

It's not the words you used, but their meaning, which I'm disputing. What you actually said was
A rock measures the moon as much as I do, and so the moon exists to the rock.
and I disputed the idea that rock measures anything, and also that the expression that 'the moon exists to the rock' is meaningless. //Both 'measurement' and 'existing for' imply intentionality, which both the moon and the rock are devoid of. Why they're devoid of intentionality is not a matter of vocabulary but of metaphysics (or more specifically of ontology).

But firstly, naturalism does not necessarily imply objective realism even though most of the time it does.

It certainly does. Objectivity is the touchstone for naturalism, what is objectively the case, what is truly so irrespective of what anyone thinks. Again, the whole problem here is that this is what has been called into question. Otherwise there would no 'problem of interpretation.'
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For instance, I described a stop sign, all without either of us observing it.

To describe a type of thing, a stop sign for example, is not the same as describing a particular thing, like a particular stop sign.

It seems a form of reality supervening on models instead of the other way around. The baguette is skinny and long. The baguette is circular. Both are equally valid. Something like that.

It's not that they are equally valid, but they are equally true, "true" meaning corresponding with reality.

But the baguette being circular and skinny-long are not wrong descriptions, but neither are they complete. Neither fully describes the thing.

If you do not think that "long and skinny" is inconsistent with "circular", then so be it. I don't think that's something I can convince you of.

It was fixed, but then before they were counted, somebody goes and adds a handful more.

You are not grasping the point which Bell is making. The number is not fixed, because no one has determined the quantity. The quantity is not fixed until someone determines it. How could it be? Do you have an explanation as to how a specific numbered could be associated with the objects, unless someone counts them? Does God establish that relationship between the number and the container? If not, who does, if no one counts them?

It does not matter what is counted. What matters is how many marbles are in there.

Obviously, it does matter. If they are not counted there is no number which correlates. Tell me how there could be one specific number which represents how many marbles are in there, if they have not been counted. Who would designate which number that is? And if no one designates the number, how can you say that there is a number which represents how many marbles are there?

Would you also argue that the winning number for a lottery is already designated before the draw is made?
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It's not the words you used, but their meaning, which I'm disputing.
Only because you will not accept how I mean the words. I say ‘measurement’, I mean that to which the ‘measurement problem’ refers. If you think that means human intended action with a numeric result, then you don’t know quantum theory at all.

What you actually said was
A rock measures the moon as much as I do, and so the moon exists to the rock.
and I disputed the idea that rock measures anything
Yea, because you insist on using your human-intent definition of the word. Being unable to get around that, I asked for a different word to describe the interaction between the moon and rock, but none was offered. ‘Interaction’ seems reasonable, and I’ve tried to use that since. Hence:
The rock interacts (a one-way interaction) with the moon as much as I do, and so the moon exists to the rock.

and also that the expression that 'the moon exists to the rock' is meaningless
despite my defining its meaning. The whole relational ontology is based on it, instead of being based on realism.
Both 'measurement' and 'existing for' imply intentionality, which both the moon and the rock are devoid of.
There you go again, insisting on using your definitions of those words. Hence my request for alternate vocabulary since existence supervening on intentionality is not what I’m trying to convey.
We’re going in circles. You’re still making all the same mistakes despite my pointing out how I’m using all these terms.

But firstly, naturalism does not necessarily imply objective realism even though most of the time it does.
— noAxioms
It certainly does. Objectivity is the touchstone for naturalism
Nonsense. Objectivity is the touchstone for realism. Naturalism is just not-supernaturalism. No woo. One can be a realist but not a naturalist, or one can be a naturalist but not a realist, such as the relational view.

For instance, I described a stop sign, all without either of us observing it.
— noAxioms
To describe a type of thing, a stop sign for example, is not the same as describing a particular thing, like a particular stop sign.
Wow, something I agree with. Good thing I didn’t specify a particular stop sign. You said “Axiom: to be described requires that the thing described be observed“. That statement didn’t mention that the axiom only applies to particular things. I also question the statement since ‘observed’ is not defined. You tend to take the common definitions of words (at least when it suits your purpose), which would imply that a blind man couldn’t possibly describe anything particular since he cannot observe.

[/quote]It's not that they are equally valid, but they are equally true, "true" meaning corresponding with reality.

If you do not think that "long and skinny" is inconsistent with "circular", then so be it. I don't think that's something I can convince you of.[/quote]You say they’re equally true, and then you say that it’s inconsistent to say so. They’re just different perspectives of the exact same physical object, so yes, it’s not inconsistent to use either word to describe the baguette. They’re both valid 2D projections (or shadows) of the exact same 3D baguette shape, and an appearance to a human is a 2D projection after all.

You are not grasping the point which Bell is making.
I know Bell’s point, but the marble thing is classical and thus doesn’t illustrate the point at all.
The number is not fixed, because no one has determined the quantity.
That’s a pretty idealistic statement. Not being one, I deny this. Knowledge of the count has nothing to do with how many marbles are in there. It’s not a wave function that is yet to collapse. Perhaps you mean a mental concept of a number, but for that, no measurement is necessary. A number can be assigned without consulting the jar. The number is then fixed, regardless of the number chosen.
If they are not counted there is no number which correlates.
Correlates to what?
• 17.4k
I asked for a different word to describe the interaction between the moon and rock, but none was offered. ‘Interaction’ seems reasonable, and I’ve tried to use that since. Hence:
The rock interacts (a one-way interaction) with the moon as much as I do, and so the moon exists to the rock.

The relationship between two such masses is defined solely in terms of gravitational attraction. The way sentient beings interact with the moon is through the mind and the senses, which rocks don't possess. So it's not a valid analogy.

What I'm arguing is that there is no existence without mind and that the nature of the universe outside any mind is unintelligible and unknowable. That's why I keep referring to the book Mind and the Cosmic Order, which is not a philosophy book, but a book about neural modelling. If you simply scan the chapter abstracts you'll see the point, which is actually rather simple, but requires something of a gestalt shift.

If we're going around in circles, it's because you continue to insist that, no, there is a universe that would exist, even if there was no mind at all to behold it. And I don't think that's an unreasonable thing to believe, in fact most people would agree with you. However, I don't agree with it, for the reasons I have been stating.

Anyway, I appreciate your patience, and also the opportunity to have had this discussion. :pray:
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Good thing I didn’t specify a particular stop sign.

In your question you asked about describing "parts of the world". This implies particular stop signs. So it just means that your example was not relevant to what you asked for.

I know Bell’s point, but the marble thing is classical and thus doesn’t illustrate the point at all.

You are not grasping the fact that an act of measurement is essentially the same whether it is classical or quantum. There is an act, "measurement" and there is a result produced from the act of measurement, which is "the measurement". The idea that the result, the measurement, exists prior to the act of measurement in a classical measurement, is a fundamental misunderstanding of the act, which is misleading you into thinking that there is a difference in this matter, between classical and quantum measurement.

We could use the map/terrain analogy. The act of measurement is part of the act of making the map, and the resultant measurement is part of the map. The idea that "the quantity" is actually part of the thing measured (terrain), instead of a product of the measurement (part of the map) is a basic misunderstanding of the act of measuring.

In the example, the thing measured is called "the jar of marbles". The parameter is "the quantity of marbles in the jar". To describe the thing (jar of marbles) in terms of parameters requires parametrization which is a human act of defining boundaries. In this respect there is no difference between a classical measurement and a quantum measurement. The "quantity" is the result, posterior to the act of measurement, as derived from and posterior to parameterization. These are human acts which are necessarily prior to the existence of the quantity. This principle is validated by the nature of description in general, as "the property" is representative of the quale, so a property is part of the map, not the terrain.

What Bell is pointing out is that the vulgar way of understanding "measurement" misleads us because we commonly think that the quantity is what is measured, not what we assign to the thing after we measure it. The vulgar way confuses map and terrain. In mundane measurements this mistaken view is inconsequential, therefore it has propagated. But this view misleads us when we consider quantum measurements. It is not the case that quantum measurements differ in this respect, as you propose, it is the case that the vulgar way of understanding "measurement" is mistaken, and misleads us.

That’s a pretty idealistic statement. Not being one, I deny this.

It appears like your anti-idealist attitude is making it difficult for you to understand the nature of the act of measurement.
• 2.8k
What I'm arguing is that there is no existence without mind and that the nature of the universe outside any mind is unintelligible and unknowable. That's why I keep referring to the book Mind and the Cosmic Order, which is not a philosophy book, but a book about neural modelling

At age 91, Dr Pinter is still intellectually active it seems. But he made his mark in mathematics, not metaphysics or neurology. His speculations about why we see multiple objects simultaneously and not isolated single objects is perhaps of interest to some. But to stretch this to imply "there is no existence without mind" seems a tad sketchy. :roll:
• 17.4k
But to stretch this to imply "there is no existence without mind" seems a tad sketchy.

I agree my way of putting it seems pretty blunt, but I've read the book thoroughly, and he makes the case quite convincingly, in my view (although I'll acknowledge he doesn't make that exact statement). But there are physicists who do - among them a Richard Conn Henry, 'Academy Professor of Physics and Astronomy at Johns Hopkins University, author of one book and over 200 publications on the topics of astrophysics and various forms of astronomy including optical, radio, ultraviolet, and X-ray.' He arrived at an idealist point of view through his own reflection on, and knowledge of, physics, as he spells out in his 2005 editorial, The Mental Universe ( Nature). And there are others.

Of course, I understand that a lot of people will see this as a form of madness (and I think I even understand why they would see it that way.) But that is why I said there's necessary shift of perspective involved. It doesn't mean what most people think that it actually means.
• 17.4k
I will add, what is meant by 'mind' is something much greater than simply the contents of an individual's conscious thought. Conscious thought and internal mentation are the merest sliver on top of the biological, physical and psychological complex which constitutes the human being. So I don't mean that the world is like an image in the individual mind or a product of the individual's imagination. Nothing like that. We are intelligent beings whose minds synthesise and incorporate information from a huge range of sources perceptual, sensational, and rational (which is why we are designated 'beings'). From this, the mind generates the unified whole which comprises reality for us, and all of science takes place against that background of unified perceptive and rational experience. Whatever judgement we make about objects of experience is made against that background - but that background, 'the mind' in the deepest sense, is not itself amongst those objects.
• 1.6k
Suppose, instead, that there is a measurement at the slits
— Andrew M

Does this measurement physically affect a photon on its way to the far screen?

Generally, yes. One exception is where a detector is placed at only one slit. The detector will not interact with the photons going through the other slit. See also interaction-free measurements.

It's also possible to use polarizers to remove and/or restore the interference pattern:

For single photons, the double-slit interference pattern can be made to disappear by using a marker.
...
The which-path marker consists of two, mutually perpendicular, polarizing filters.
...
When either the vertical or the horizontal filter covers both slits, the double-slit interference pattern is preserved, albeit at a reduced intensity compared to no filter. When the vertical filter covers one slit and the horizontal filter covers the other, the double-slit pattern disappears completely. Two superimposed single-slit patterns are all that remain. This new arrangement changes the setup into a which-path experiment in the sense that it is now (in principle) possible to know which slit the photon passed through; this destroys the quantum interference.

Introducing a third polarizing filter, the quantum eraser, between the marker and the detector thwarts the which-path experiment if it is oriented 45° with respect to the marker filters. Every photon reaching the detector is now polarized in the direction of the third polarizer and it is no longer possible to know which slit each photon passes through; as a result, the interference phenomenon is restored.
• 1.2k
The relationship between two such masses is defined solely in terms of gravitational attraction.
I gave no such definition. Just for example, one mass might be larger than the other. That’s a relation that isn’t gravity related. It’s also not the relation of which I speak, which is one about A existing relative to B.
And the rock might be affected by a photon emitted by the moon. That’s a fairly trivial and direct interaction. In fact, it is nearly impossible to keep two nearby objects from interacting, which is why putting a macroscopic object into superposition of states requires it to be in the total darkness and cooled to nearly absolute zero, and even then the interaction is prevented for only a microsecond or so.
The way sentient beings interact with the moon is through the mind and the senses, which rocks don't possess. So it's not a valid analogy.
The way sentience affects the interaction of things is irrelevant to an ontology not based on sentience. The analogy is spot on if you would just stop interjecting assumptions from different views. I’m really surprised that you can’t do that, let go of your biases for a moment to consider a different view. You can’t falsify it if you presume alternate views to do the falsification.
What I'm arguing is that there is no existence without mind
Not in a view that doesn’t define existence based on epistemology. This is exactly what I mean about your inability to set aside this bias long enough to consider something that doesn’t assume this.
If we're going around in circles, it's because you continue to insist that, no, there is a universe that would exist, even if there was no mind at all to behold it.
I said no such thing. That’s realism, a valid view in itself even if it contradicts your biases. But I’m not talking about that view either, and I didn’t suggest that there is a universe that would exist even if there was no mind at all to behold it. And yes, we’re going in circles because almost all my responses are pointing out where you put in your assumptions in a view that doesn’t posit them, or you insisting on realist assumptions in a view that isn’t realist.
And I don't think that's an unreasonable thing to believe, in fact most people would agree with you.
You mean most people agree with realism. But I’m describing something else. Realism seems to have problems, but not the problems you see which is only an incompatibility with your views.
However, I don't agree with it, for the reasons I have been stating.
That’s fine. I’ve never asked you to agree with anything, realism or otherwise. I don’t think you’ve shot down realism since various realist interpretations (MWI, the subject of this topic, being one of them) are still considered valid interpretations by the physics community.

Good thing I didn’t specify a particular stop sign.
— noAxioms
If you think I described a particular stop sign, then surely you can inform me which one was specified.
The sign thing was simply my attempt to figure out how you distinguish ‘perspective’ from ‘point of view’, something you’ve not clarified.

It appears like your anti-idealist attitude is making it difficult for you to understand the nature of the act of measurement.
I’m not anti-idealist, but the premises of idealism shouldn’t be asserted when discussing a non-idealistic view.

If they are not counted there is no number which correlates.
• 11.1k
If you think I described a particular stop sign, then surely you can inform me which one was specified.
The sign thing was simply my attempt to figure out how you distinguish ‘perspective’ from ‘point of view’, something you’ve not clarified.

I didn't see that either of us was trying to distinguish 'perspective' from 'point of view'. What would be the point of making such a distinction?

The number which correlates with the defined parameter. I went though that already. There's an object described as a jar full of marbles. The defined parameter is 'how many marbles are in the jar?'. There is no specific number which correlates with this parameter until someone counts the marbles and establishes that relation. You can say that someone estimates, guesses, or assigns a random number, these are all different modes of counting, and the mode of "counting" is not relevant. The point is that there is no answer to the question of "how many marbles are in the jar?" until someone answers it.
• 17.4k
set aside this bias...

My trying to explain a philosophical view to you is not 'bias'. It's a philosophical view.

The way sentience affects the interaction of things is irrelevant to an ontology not based on sentience.

So, an ontology not based on sentience is described as what? Where in the philosophy text books or science textbooks do you find a description of such an ontology?
• 1.2k
My trying to explain a philosophical view to you is not 'bias'.
It's a bias if you apply the assumptions of that view to all other view.

I didn't see that either of us was trying to distinguish 'perspective' from 'point of view'. What would be the point of making such a distinction?
You said the following, suggesting two different ways to 'take' relativity, seemingly differing only in the words 'perspective' or 'point of view'.
We can take "relativity" in two ways. 1) The world appears different to us, depending on the perspective we take. 2) The world is different from different points of view.
Not knowing how you distinguish those, I don't see the two ways. I think you're speaking of relativity theory, but not sure about that either.

Correlates to what?
— noAxioms

The number which correlates with the defined parameter. The defined parameter is 'how many marbles are in the jar?'
But you defined the latter as the same as the former. 'How many marbles are in the jar' is a mental quantity in your mind, which tautologically is going to correlate to count, also the mental quantity in your mind, no matter which number you choose. Interaction with the jar (counting) seem unnecessary for this.

The point is that there is no answer to the question of "how many marbles are in the jar?" until someone answers it.
This seems to agree with my assessment just above.

You seem to suffer from the same problem as Wayfarer, which is insistence on applying the premises and definitions of idealism to falsify a view that isn't idealism, which is a begging fallacy.'
• 11.1k
But you defined the latter as the same as the former. 'How many marbles are in the jar' is a mental quantity in your mind, which tautologically is going to correlate to count, also the mental quantity in your mind, no matter which number you choose. Interaction with the jar (counting) seem unnecessary for this.

Right, that's the way ontology works, we make definitions which accord with the way that we understand reality, and we proceed from those principles. If you think that you have a better ontological understanding of this matter, (perhaps you think that God always counts how many marbles are in the jar, or something like that), then propose your better definition.

You seem to suffer from the same problem as Wayfarer, which is insistence on applying the premises and definitions of idealism to falsify a view that isn't idealism, which is a begging fallacy.'

This is obviously because idealist premises are the one which best correspond with the reality of the situation. You haven't provided any reasons why you think that they are not the best premises, only the attitude of 'those are idealist therefore reject them'.
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