And yet infinitely often, the zero-amplitude strikes will also happen in some worldline of the observer. Which screws any claim to have done something which has constrained the probabilities to these observed bands. — apokrisis

Zero-squared is still zero, experimental imprecisions aside.

Under MWI, there will be infinitely many worlds in which all the bands are composed of the least likely events. So the bands will be exactly where they shouldn't be for an infinity of observers.

If you take MWI seriously, you can't take the probabilistic success of QM seriously. Everything that can happen, happens infinitely often. — apokrisis

It doesn't have to be that way. You can reject actual infinities and consider limits such as Planck-length and light-speed to constrain the locations a particle can be in since it was last measured. As Max Tegmark, who advocates MWI, says:

Yet real numbers, with their infinitely many decimals, have infested almost every nook and cranny of physics, from the strengths of electromagnetic fields to the wave functions of quantum mechanics. We describe even a single bit of quantum information (qubit) using two real numbers involving infinitely many decimals.

Not only do we lack evidence for the infinite but we don’t need the infinite to do physics. — Infinity Is a Beautiful Concept – And It’s Ruining Physics - Max Tegmark

And QM is moving towards that kind of interpretation with the quantum information or quantum reconstruction projects. MWI and Bohmian Mechanics are the last gasp of an out-dated way of conceiving of physicalism. Their advocates are especially passionate probably because they know they are a passing story. :) — apokrisis

It takes a theory to beat a theory... I think David Wallace's comments are worth reading on this subject (particularly his answers to Q9 and Q10).

I’d also say that I don’t see how reconstruction could reduce the need for interpretation. Ultimately, however we reconstruct quantum mechanics, we’re either going to end up saying (i) that the mathematical structure thus reconstructed represents physical reality faithfully (in which case we end up with the Everett interpretation or something like it), or (ii) that it represents physical reality incompletely or inaccurately (in which case we need to fix it, which leads us to hidden-variable or dynamical-collapse theories), or (iii) that it’s not in the business of representing physical reality at all (which leads us to operationalist or neo-Copenhagen or physics-is-information approaches). — Interview with David Wallace

So, can it be affirmatively asserted that QM affirms the concept of having a 'free will'? — Posty McPostface

No. That's more a conceptual/philosophical issue that one brings to QM. And, as it happens, the Schrodinger equation is deterministic.

The Schrödinger equation describes the (deterministic) evolution of the wave function of a particle. — Wikipedia

For fun, you might like Conway and Kochen's free-will theorem that basically says that if we have free-will then so do particles. But note that free-will, as Conway and Kochen define it, just means that the outcome is not determined by the prior history of the universe.

Yes I agree with the blog post - I think the basic argument boils down to both form and matter being indispensable categories that aren't reducible to the other.

So materialism fails when it eliminates form and idealism fails when it eliminates matter. Hence hylomorphism.

But I think that the Platonist insight into the reality of incorporeal entities (universals and the like) requires a genuine meta-cognitive shift - a gestalt shift, if you like. — Wayfarer

True, but genuine cognitive shifts don't have to end there. As you know, Aristotle was well-versed in Plato's ideas and his hylomorphism retained universals sans the Platonic reification.

Aristotle's position stands in contrast to both Platonic idealism and Democretean materialism. An Hegelian synthesis perhaps.

And then, the question is ‘why’. What is so unpalatable about the irreducible nature of mind? Why is that such a boogeyman? It seems to me an illustration of the incredible things people will be prepared to entertain, just to avoid the possibility that materialism might not be real. Not trying to argue the case, only for reflection on it. — Wayfarer

I think it just comes down to one's fundamental philosophy, especially one's position on universals.

It seems to me that you start with mind (a universal) and your ontology follows from that. What seems incredible to you, and yet seems reasonable to a materialist, is just a function of where one starts from. For a materialist, quantum mysticism seems incredible.

Things exist only in relation to something (anything) else. There is no objective existence of anything, thus solving the problem of why existence exists. It doesn’t. — noAxioms

By "objective" here, do you mean "absolute"?

So I started with something like Ontic Structural Realism, except without the objective realism. The universe is a mathematical structure and things within it are real to each other. It is not platonic realsim. Numbers are abstract (not real) to us, but relate (are real) to each other. 7 exists in relation to 9, or to the set of integers, but our universe is not existent in relation to them any more than numbers are real to us. 13 is prime, and doesn’t require objective existence to be prime. Similarly, we don’t require objective existence to relate to other parts of the structure. This is a key concept, demonstrating why objective ontology (or lack of it) makes no difference in the relations between different parts of the same structure. — noAxioms

On your view, numbers seem to have an existence independent of matter (and mind) which would qualify as Platonic realism about universals.

"Ontologically, either you're a realist or an anti-realist. Either you accept facts are real independently of the "human mind" (realist), i.e. objective, or you accept that reality is only subjective (anti-realist)." [from Research Gate]

Here I must disagree, and this seems to be the point of my OP here. He says the only alternative to an objective reality is one relative to (or supervenes on) human mind. How very anthropocentric. Ontological relativism means relative to anything, but not supervening on that thing. — noAxioms

I agree that absolute/relative is a different axis to realist/anti-realist (objective/subjective). Einstein's theory of relativity is a realist theory, for example.

But that isn't what measuring devices are supposed to do in the Copenhagen interpretation is it? The stuff is there. It just doesnt have any location and so forth.

So the quantum idealist (if that's what they should be called) are realists in the sense you're using. — frank

I would classify the Copenhagen Interpretation as anti-realist since it doesn't provide an explanation of what is going on, just probabilities. Bohr's view, as far as I can tell, was that it was meaningless to talk about objects prior to measurement.

Berkeley denied the existence of substance - so whatever account you have of it cannot possibly accord with Berkelean idealism. — ProcastinationTomorrow

Berkeley was rejecting Locke's material objects (and representationalism). But Aristotle's substance is more like Berkeley's sensible objects, except situated in the world not mind. And I agree with Berkeley's empiricism, rejection of Cartesian dualism and rejection of Lockean primary/secondary qualities.

A realist interpretation (quantum or otherwise) may be coherent, but this comment sounds like you are suggesting that anything other than a realist interpretation of physical theory (for instance, an instrumentalist one) would be incoherent. You would need to have a strong argument for that, independent, of course, of the bare (and ceded) fact that a realist interpretation of QM is coherent. — jkg20

I'm just referring to realism vs idealism here where we are looking for a coherent mechanism, not just an instrumental use of a formalism.

Ontological realism isn't necessary to physics. There are idealistic and physical schemes that are compatible with any sort of physics. Scientists don't need to sort that kind of issue out. They dont need an extra label: idea stuff vs physical stuff.

Or were you talking about some other kind of realism? — frank

Yes. I'm not drawing a distinction between physical stuff and idea stuff - I think that (dualistic) idea is incoherent as well. My view is Aristotelian realism, which is that substance is primary and ideas about substance are secondary. That doesn't necessarily commit to what the nature of this or that substance is - and so may accord with, say, a Berkelyean idealism in many respects. But conceptually, the stuff comes first, the awareness of that stuff second.

What I think is incoherent is the idea that awareness of stuff somehow causes it to exist.

The whole import of the ‘delayed choice experiment’ seems anti-realist. — Wayfarer

It isn't. The results are just what one would expect from QM.

At issue, is the very meaning of the word ‘physical’. The difficulty is that the precise nature of whatever it is that is being measured can’t be ascertained with certainty prior to the act of measurement. — Wayfarer

It can if the assumption of counterfactual (value) definiteness is dropped. Which is what both Many Worlds and RQM do. Which is to say, they reject classical realism and accept quantum realism.

Again the whole question assumes a realist perspective which is the very thing being called into question. — Wayfarer

A realist perspective is assumed because that is the way to construct a physical theory that is conceptually coherent.

↪Andrew M Fair enough, I stand corrected. But I still think it’s a legitimate question as to whether any actual ‘registration’ has occurred in the absence of an observer, who in such cases, creates the very machine which records the observation. — Wayfarer

Isn't that just a question of the logic of the language used? But whether or not a conscious observer is present (say, before life emerged on Earth), physical systems interact as described by the rules of quantum mechanics. Would you agree?

What is ‘sophistry’ about claiming that ‘an observer’ is in fact an observer? Claiming that an apparatus constitutes an observer is the only ‘sophistry’ in play here. — Wayfarer

Do you include Heisenberg and Bohr in that assessment?

Of course the introduction of the observer must not be misunderstood to imply that some kind of subjective features are to be brought into the description of nature. The observer has, rather, only the function of registering decisions, i.e., processes in space and time, and it does not matter whether the observer is an apparatus or a human being; but the registration, i.e., the transition from the `possible' to the `actual,' is absolutely necessary here and cannot be omitted from the interpretation of quantum theory. — Werner Heisenberg

Naturally, it still makes no difference whether the observer is a man, an animal, or a piece of apparatus, but it is no longer possible to make predictions without reference to the observer or the means of observation. — Niels Bohr

Notwithstanding the fact that all apparatus are constructed by observers. (Sorry for intruding with a philosophical observation.) — Wayfarer

All that is required is two physical systems that interact to produce information. Those physical systems need not have been constructed by anyone.

Here's Rovelli in Edge:

We say that there is "relative information" between two systems anytime the state of one is constrained by the state of the other. In this precise sense, physical systems may be said to have information about one another, with no need for a mind to play any role.
...
The world isn’t just a mass of colliding atoms; it is also a web of correlations between sets of atoms, a network of reciprocal physical information between physical systems. — Relative Information

So - it's acknowledged to be 'observer dependent', but by designating the observer as 'a reference frame' rather than as an actual scientist, then the pesky 'observer problem' with its attendant philosophical problems of 'mind' or 'consciousness' is removed from the equation. — Wayfarer

It's removed from the Schrodinger equation, yes.

That is just one way of putting the metaphysical quandry that QM presents. But jkg20 brought out another insofar as answers to the question "what does the wave function represent" will have metaphysical consequences, and those who want to answer that question should not just help themselves to everyday notions of "observation", "measurement" and so on since those everyday notions are very definitely wrapped up with the idea of their being acts performed by conscious beings. One would be using the word "observer" in a most unusual way if one were to say that "lamps are observers", and to avoid misunderstanding it would be better not to use that word at all in that context. — ProcastinationTomorrow

That usage of "observer" is conventional in special relativity and quantum mechanics. From Wikipedia:

Physicists use the term "observer" as shorthand for a specific reference frame from which a set of objects or events is being measured. Speaking of an observer in special relativity is not specifically hypothesizing an individual person who is experiencing events, but rather it is a particular mathematical context which objects and events are to be evaluated from. The effects of special relativity occur whether or not there is a sentient being within the inertial reference frame to witness them.
...
In quantum mechanics, "observation" is synonymous with quantum measurement and "observer" with a measurement apparatus and observable with what can be measured. — Observer (special relativity)

Physicists are always going to develop technical language in ways that they find useful to them. So I think the key to avoiding misunderstanding is to be aware of how language terms are used differently in that context compared to the everyday context. That is what Rovelli was pointing out with his lamp example.

Along with "observer", terms like "measurement", "information" and "action" similarly don't imply consciousness or mind in a physics context. So note the use of "observer" in the first sentence of the RQM Wikipedia entry:

Relational quantum mechanics (RQM) is an interpretation of quantum mechanics which treats the state of a quantum system as being observer-dependent, that is, the state is the relation between the observer and the system. — Relational quantum mechanics

This simply means that, per RQM, the state of a quantum system is always indexed to some reference frame (termed an observer), rather than being absolute. It implies nothing about consciousness or mind.

I could be misconstruing your worldview, but it would appear to be a QM interpretation that is still clinging to the materialist premise that there is a mind-independent world of matter 'out there', the very notion that Kastrup, or any idealist ontology, is dubious about ... as now am I. — snowleopard

Yes, I think the world exists independently of mind (per Aristotelian realism rather than materialism).

My initial comment in this thread was to point out that quantum contextualism doesn't challenge mind-independent realism as Kastrup claims. In fact the major realist QM theories are all contextual, including RQM which, ironically, Kastrup thinks implies idealism.

So says a conscious observer. Again, I repeat the question: What exactly is a measurement absent a conscious agent to calculate a measurement from the reactive apparatus, if that measurement apparatus itself is observer-dependent, without which isn't it all just in potentia? — snowleopard

A measurement is a physical interaction between quantum systems.

In the reference frame of the apparatus, a definite particle spin result has been recorded on its display.

In the conscious agent's reference frame, prior to interaction with the composite particle/apparatus system, there is no definite particle spin result recorded on the apparatus display (i.e., the composite system is in superposition).

Kastrup's claims depend on a narrow definition of realism as counterfactual definiteness, not as mind-independence
— Andrew M

You lost me there, Andrew. Care to elucidate the distinction? — Wayfarer

Sure. Counterfactual definiteness means that if a measurement of a physical property is not in fact performed, it nonetheless has a definite value. For example, if a particle is described as being in a superposition of spin up and spin down, counterfactual definiteness means that the particle nonetheless has a single definite spin value prior to any measurement being made.

Many Worlds rejects counterfactual definiteness since it says the particle has both spin values prior to measurement. RQM also rejects it, since it says the particle can only have a definite spin value with respect to an interacting system.

it is traditional to denote this something as the observer, but it is important in the following discussion to keep in mind that the observer can be a table lamp.
— Relational Quantum Mechanics - Carlo Rovelli

↪Andrew M This would seem to be a radical redefinition of the word 'observer.' Surely any claim whatsoever can be rationalized, if you arbitrarily redefine words so that what you want to claim then ends up making linguistic sense. — snowleopard

It's a technical usage, but feel free to just substitute "quantum system". The key point in RQM is that there are two quantum systems that interact and it is that interaction that results in definite values. For example, a particle interacts with a measuring apparatus that consequently displays either "spin up" or "spin down". That process occurs independently of conscious observers being present.

Anyway - I'm reading Kastrup's essay, Making Sense of the Mental Universe, and it seems pretty carefully reasoned to me. — Wayfarer

Just some comments on his opening paragraph...

Contextuality is a formidable challenge to the viability of realism. — Bernardo Kastrup

It's actually not a challenge at all. Kastrup's claims depend on a narrow definition of realism as counterfactual definiteness, not as mind-independence. Bell's inequalities show that counterfactual definiteness and locality can't both be true, not that mind-independent realism and locality can't both be true.

Bohmian Mechanics, Many Worlds and RQM are all contextual realist theories (in the mind-independent sense). As Rovelli says:

In order to prevent the reader from channeling his/her thoughts in the wrong direction, let me anticipate a few terminological remarks. By using the word “observer” I do not make any reference to conscious, animate, or computing, or in any other manner special, system. I use the word “observer” in the sense in which it is conventionally used in Galilean relativity when we say that an object has a velocity “with respect to a certain observer”. The observer can be any physical object having a definite state of motion. For instance, I say that my hand moves at a velocity v with respect to the lamp on my table. Velocity is a relational notion (in Galilean as well as in special relativistic physics), and thus it is always (explicitly or implicitly) referred to something; it is traditional to denote this something as the observer, but it is important in the following discussion to keep in mind that the observer can be a table lamp. — Relational Quantum Mechanics - Carlo Rovelli

The conceptual issues that quantum mechanics raises are to due to classical assumptions like non-contextualism, not philosophical realism itself. So I can agree with Kastrup when he quotes Rovelli here:

Carlo Rovelli’s relational interpretation [Rovelli, 2008], on the other hand, sticks to plain quantum theory and embraces contextuality. Instead of loading it with unnecessary baggage, it simply interprets what quantum theory tells us about the world and bites the bullet of its implications. Rovelli’s goal “is not to modify quantum mechanics to make it consistent with [his] view of the world, but to modify [his] view of the world to make it consistent with quantum mechanics” [Rovelli, 2008: 16]. — Bernardo Kastrup

Almost everything seems to be a relation. — noAxioms

I agree.

I have a hard time coming up with an example of a property. — noAxioms

Yes, if properties are understood in an absolute sense. But they can also be understood as implying a relational context. So to use your color example, the statement "noAxioms' screen avatar is yellow" is true when indexed to humans (as is normally implied) but false when indexed to squirrels. Whereas, the statement "noAxioms' screen avatar emits light with red and green wavelengths" is true in a broader context that includes both humans and squirrels.

I'll leave the rest for now and we can pick it up in the new thread.

Anyway, thank you for the interesting discussion! — boundless

And thank you! I'll be travelling over the next week so will be taking a break from the forum as well.

I rescind this. The position does stake a claim here, that the universe is a universal, and that it does not have Platonic existence since that would be something concrete. — noAxioms

No, Platonic existence is abstract and immaterial. From Wikipedia:

In Platonic realism, universals do not exist in the way that ordinary physical objects exist ... Platonic realism holds that universals do exist in a broad, abstract sense... — Platonic realism - Wikipedia

Then the position I am proposing is not compatible with the Aristotelian position. To frame what I am proposing in such terms is to say that our universe is a (non-Platonic) universal with no necessary particulars. For it to be a particular, said particular would need to be in (relative-to) some container universe which again would be a universal at its foundations. — noAxioms

It wouldn't. On an Aristotelian view, all that is needed is the familiar distinction between things that are a part of the universe and the universe itself. There is no need to assume a separate reality beyond the universe (as is assumed with Plato's allegory of the cave).

As for the apples, I don't see how 2+2=4 would necessarily not be the case just because there are no apples (or any other concrete particular) to instantiate the relationship. — noAxioms

The meaning of '2+2=4' derives from particulars, it shouldn't be assumed to be meaningful independent of the concrete universe that we find ourselves a part of. What distinguishes Aristotle from Plato on this just is the idea of a natural concrete context that establishes meaning versus an abstract view that is untouched by empirical concerns.

I agree that deterministic theories are context-dependent.

What I do not understand however is how can something like "free agency" arise from deterministic processes (or a combination between deterministic and random processes). But as you said, this is normal since no theory has ever explained it :wink: — boundless

Agreed. At present, I think of them as equally valid descriptions in different reference frames (as with Rovelli's RQM or Einstein's relativity).

I, too, disagree with Tegmark's Platonism. But I disagree with computabilism because I think that, for example, the "workings" of our minds cannot be explained in computabilistic terms. At the same time however our theories to be both consistent and complete must be computable. This shows, however, the limits of physics IMO. (and of course I did not mean to "lower" the importance of it with this observation :wink: ) — boundless

What I think of as computable here is the physics for Alice's actions from Bob's (non-interacting) reference frame.

However Alice can't compute her own physics for Godelian reasons. For example from Bob's reference frame one of the statements, "Alice will choose tea" or "Alice will choose coffee" will be predicted to be true, but she can't herself construct a proof for the true statement. Either outcome is an open possibility for her and requires her to make that choice for herself.

I observe it, being part of it. Indeed, I could not observe it from outside, lacking a particular ‘it’ to observe. It could be simulated, but then it is the simulation being observed, not the structure itself.
Again, I reach for the simplest cases like 2+2=4, which has no particular, but the relation between 2+2 and 4 exists, particular or not. I can simulate (perform the addition) to observe this, but doing so is just for the benefit of the performer of the operation and has no effect on the truth of the relation. — noAxioms

The Aristotelian position is that cases like '2+2=4' derive from concrete particulars, they don't have an independent existence. For example, there are two apples in the basket and I add two more. By generalizing from apples to any object and abstracting away physical constraints, we derive a formal rule for adding things without limit.

This is an empirical account of mathematics that doesn't require positing a Platonic existence for abstract mathematical entities.

I don’t really claim anything one way or the other on universals. I need to see how this fits in, since you seem to lean on the problem of universals as a counter-argument to my idea here. — noAxioms

It's a question of how one conceptually models the world. I think the arguments that you or I find plausible in our discussion really stem from this philosophical issue.

Being concrete would be an objective context, the larger context of all things that actually exist, not in relation to anything. I guess I’m trying to argue against your point, that concreteness is necessary.
What do you mean by ‘abstract’? Just not-concrete? The word has connotations of being a mental construct (thought or idea), which is not the direction I’m going. Our universe is not necessarily conceived of by something not part of the structure. — noAxioms

As an example, I see two apples on the table but I don't see the number two. The apples are concrete particulars, the number two is an abstract quantity.

On the problem of universals, my position is Aristotelian realism. So I regard the universe as concrete and observable. Also the universe has a mathematical structure, but that structure is not separable from matter.

The meaning might be indispensible human baggage, but the structure itself (not necessarily any ‘equation’ that describes it to an observer for whom it means something) seems not to require said observer. OK, ours comes with humans built in, so it seems to be a structure that finds meaning in itself, but that’s an internal relation, not ontology. — noAxioms

I agree that the universe doesn't need an observer. But given that we are observing it, it follows that it is concrete (since we can't observe universals). Just as the apples must be concrete in order to observe them.

Now your claim seems to be that that is just us humans talking about the universe in our human way - the universe could really be something else in itself. But my argument is that abstractions (and representations) have an essential logical dependency on concrete particulars in our language use. So we can't then just posit something as being purely abstract (which we never observe) and expect that to be a meaningful statement.

We seem to just be asserting opposite views. I don’t see either of us making good justification of our positions. Doing my best. I don’t claim that there is no ontology, just that it is not necessary. To me, that seems to put at least some burden on you to show (not just assert) that it is necessary. The humans in the uninstantiated universe would have the exact same observations and thoughts as the humans in the instantiated universe. Do you disagree? It seems to assume that humans are part of said universe, and not external experiencers of it, so kind of discarding dualist biases, which is hard to do. — noAxioms

I do disagree since, on my view, an uninstantiated (purely abstract) universe would be just nothing. But I do also agree that we are internal experiencers of the universe and that dualism is mistaken. While my specific arguments are the observation and coherency arguments above, generally speaking it's really just the philosophical question of the problem of universals.

I agree that your definition is enough to assign responsibility for one's actions. The average argument defines free will differently, but then incorrectly concludes that I should not be held responsible (on Earth) for my actions. "You shouldn't jail me, physics made me do it!". This is bunk. Physics will also toss your sorry posterior in the clink, and by the same argument, is not wrong for doing so. — noAxioms

Exactly.

I agree with your analysis in the rest of your post and your analogies are great. My general thought is that a pragmatic definition is an abstraction that enables different people to fill in the details according to their own preferred philosophical views. But, being pragmatic, everyone understands how it is used and so communication remains possible despite those different philosophies. We see this in a striking way with the different QM interpretations despite there being broad methodological agreement on how to use the math to solve practical problems.

The "effective" free will advocated by compatibilism in fact is not a "real" free will, but simply it is a statement of "unpredictability". — boundless

Alice could choose tea over coffee all her life and everyone who knows her could predict this. But I don't think this demonstrates that it wasn't really her choice.

I think conceiving of determinism in an absolute sense (the view from nowhere) does seem to negate agent causality, as you indicate. However my argument is that deterministic theories are only applicable within a context (the view from somewhere). So, for Alice, the context includes her ability to make choices, her perceptual capabilities, her knowledge and so on. She can then use deterministic theories to predict what external physical systems will do. But those theories can't circumvent or undermine the intentional context that they are empirically grounded in. And so we see that when Bob interacts with Alice, his prediction about her choice breaks down and Alice's intentional choice prevails.

This (and similar things I read some time ago but unfortunately I cannot remeber now), seem to suggest that if there is a "theory of everything" then "physical laws" are computable. — boundless

Yes, I agree with the computability thesis (though not with Tegmark's Platonism).

The point I wanted to discuss is that IF our universe is such a structure, it need not be instantiated in some larger context to explain empirical experience. — noAxioms

I agree that it doesn't need to be instantiated in some larger context (since there may be no larger context), but I would argue that it still needs to be concrete, not merely abstract. I'd like to highlight this part of Tegmark's (shorter) explanation of the MUH:

Before discussing whether the mathematical universe hypothesis is correct, however, there is a more urgent question: what does it actually mean? To understand this, it helps to distinguish between two ways of viewing our external physical reality. One is the outside overview of a physicist studying its mathematical structure, like a bird surveying a landscape from high above; the other is the inside view of an observer living in the world described by the structure, like a frog living in the landscape surveyed by the bird. — Shut up and calculate - Max Tegmark

So I don't agree that there is a bird's eye view of the universe (i.e., a view from nowhere). We never directly observe numbers or mathematical structures, only concrete things that we can then describe in abstract terms. Mathematical equations ultimately derive their meaning from those concrete things, they aren't dispensable "human baggage". So a complete mathematical description of the universe would need to be in human-observer terms (i.e., a view from somewhere).

The idea that there are pure abstractions or a view from nowhere seem to be claims without an empirical basis.

Wanted to comment on this. Where is Bob in relation to Alice? If outside (non-interacting) with closed Alice system, and if hard single-outcome determinism is true and Bob has access to full state and the resources to make the prediction, then yes, Alice, in the deterministic contained system, can be perfectly predicted and has no ‘predicted outcome’ to reject. Bob cannot divulge the prediction to Alice as that would be interacting, making the system not closed. — noAxioms

Yes.

OK, so if Bob is within the closed system, there are several reasons, determinism or not, that he cannot make such a prediction. 1: State cannot be known, per Heisenberg uncertainty. 2: Bob cannot predict himself, even if he had this unobtainable state. It would require a mechanism to simulate itself faster than real time. Alice of course would just be waiting for Bob’s prediction, at which point Alice will choose the opposite thing. I can make a small mechanical device with only a couple parts that does that, and Bob will fail to predict its behavior. That doesn’t demonstrate that the device has free will, however you might define it. — noAxioms

It doesn't. But I don't define free will as implying unpredictability (nor predictability as implying its absence), but as choosing what one wants. The point is that there is no outcome that Alice must accept if she doesn't want to.

Well I kind of agree with you. But you have to accept that Alice in her reference frame has "libertarian" free will, which is not strictly speaking allowed by the known theories of physics. But that's exactly is the problem. How can it "emerge" from either random or deterministic processes? — boundless

The free will here is that Alice can choose the outcome she wants (and the outcome she wants can change as new information is brought to her attention). I don't see that known (deterministic) theories of physics disallow that, though I would agree they don't explain it either.

I think they can be trivial universes on their own. Does x=1 mean anything that just '1' doesn't? — noAxioms

Yes, I was meaning the equation for a line. In this case, would the line have an infinite number of points or would it be discrete? And if both a line and a number (a point on the line?) can be a universe, does that mean that there are universes within universes?

Well, I'd have to say two kinds of ontology: The structures themselves, which have no ontology, and the things in it (galaxies, cups, photons, gliders) which have a relationship to the structure as a whole. — noAxioms

My main objection is that you seem to be making a distinction between things in a universe, which are physical, and the universe itself which is not physical. But aren't the things in the universe themselves mathematical on your view? In which case, isn't the term "physical" merely human "baggage", to use Tegmark's term?

Well, the relational approach is very interesting in this issue. But again, the outcomes of choices are either random or deterministic (in the "reference frames" of the various agents) and randomness cannot explain free will. — boundless

Instead of random, I would say Alice's choice is determined by her (i.e., self-determined) in her reference frame, whereas the outcome can be predicted with certainty in Bob's reference frame.

On a relational approach, no contradiction arises since Alice and Bob haven't interacted and jointly considered the specific predicted outcome. But if they did, then Bob's prediction would no longer be certain, since he can only predict the outcomes of isolated systems, not outcomes of the (Alice + Bob) system he is now a part of. So Alice is free to reject that outcome. But Carol, an observer of the isolated (Alice + Bob) system, could still predict the outcome of Alice's choice.

On the other hand, if we allow the existence of libertarian free will in the case of Alice, maybe we can still assume that in Bob's "reference frame" the choice was inevitable. I wonder if this makes sense (if it does we actually solved the problem of "free will" and omniscence using an interpretation of QM :wink: Sometimes life can be very surprising :rofl: ) — boundless

Yes. Though it's worth noting that Bob can only predict the outcome of Alice's choice on the condition that he doesn't interact with Alice (perhaps itself a choice).

Wow, a lot of context is missing here. — noAxioms

Sorry! What I was actually drawing attention to in that quote was that observer O' measures particle S with spin-down. But, earlier, observer O had measured particle S with spin-up.

In quantum mechanics, subsequent spin measurements of a particle in the same basis give the same result. So there would seem to be a paradox here, since (in realist terms) the measurements by observer's O and O' contradict each other.

But, per RQM, no comparison can be made until observer's O and O' physically interact and compare results. And when they do, they will find their two spin measurements are in agreement, just as quantum mechanics predicts! So there is no paradox in relational terms.

That should seem a bit fishy. Is there any possible mechanism by which that agreement could come about without bringing in many physical worlds?

Looking for inconsistencies in the view. I really like the view since it removes the need for instantiation, which always seems rationalized, and not actually rational, when I see it explained for other views. Cosmological argument for God is such an example. — noAxioms

OK, I'll take up the challenge. :-) Are the physical things in the universe also merely formal? Or does your ontology have two kinds of things - the formal structures (the universes) and substantial (physical) things in the universes?

Also is the equation "x = 1" a universe? How about just individual numbers, like the number 1? Or 0?

In relation to the more local observation (the geiger counter and the cat it didn't kill), there is only one outcome, not both. RQM seems to never allow multiple outcomes. — noAxioms

I haven't seen Rovelli directly discuss the issue of multiple outcomes but the Wikipedia entry on RQM does:

But, let us imagine that O' measures the spin of S, and finds it to have spin down (and note that nothing in the analysis above precludes this from happening). What happens if he talks to O, and they compare the results of their experiments? O, it will be remembered, measured a spin up on the particle. This would appear to be paradoxical: the two observers, surely, will realise that they have disparate results.

However, this apparent paradox only arises as a result of the question being framed incorrectly: as long as we presuppose an "absolute" or "true" state of the world, this would, indeed, present an insurmountable obstacle for the relational interpretation. However, in a fully relational context, there is no way in which the problem can even be coherently expressed. — Relational Quantum Mechanics - Wikipedia

Which is to say, multiple measured outcomes can occur, but this can't be coherently expressed in relational terms since no interactions between the worlds occur. That is, in relational language, the other worlds are not real for observers in this world and neither is our world real to them.

The gliders and such exist as 'physical' parts of that universe. — noAxioms

OK. So to clarify, you're saying that CGOL (as a formal and non-instantiated structure) nonetheless has its own internal physics. And from inside the structure, gliders are physical but, from their frame of reference, their universe is formal.

And similarly for us, birds, trees and human beings are physical. But our universe is formal.

Yes, that "free will" is certainly possible in determinism. Nobody denies the "phenomenon" of "willing" and that in principle it is possible to choose tea rather than coffee. — boundless

I would just note that it is the agent herself that is the locus and determinant of her choice, not her will or desires. (As Pierre-Normand explains in his last sentence here.)

On the other hand, if determinism is true then all my choices are inevitable even if there are different options and if is not forced to choose in a way. — boundless

I think it's worth considering something like Rovelli's (and Bitbol's) relational approach here. Bob may be able to secretly predict the outcome of Alice's choice with certainty, per Bob's deterministic theory. But there is no specific outcome that Alice should regard as certain, since she can always reject that outcome and choose differently.

In my view, both those perspectives should be taken as equally valid. Which means that whether or not an outcome is inevitable is indexed to the agent considering the outcome, it's not an absolute claim.

While I agree that the occurrence of the prediction, and the presentation of its putative content to the agent, take away nothing from the agent's freedom of choice, it must be noted that this setup may make it impossible for the prediction to be successful. That's because if the agent has set up her mind to do the opposite from whatever she is told that she had been predicted to do, then, conditionally on her being presented with the prediction that she would drink tea, say, the predictor will predict that she will drink coffee, and vice versa. So, under those conditions, the prediction, as written down and shown to the agent, can't succeed. — Pierre-Normand

Exactly. So, per my comments to boundless above, the agent should never regard any specific outcome as inevitable for her since she can always choose otherwise if she wants to. Whereas a specific outcome may be appropriately regarded as inevitable from the predictor's perspective.

Hence, in the counterfactual scenario, you may choose to deliberately do the opposite of what it is that was "predicted". That's because the "prediction" was effected under the assumption that you would not be informed about its content. — Pierre-Normand

I agree with your comments. However it wouldn't matter if the prediction did take into account that I would be informed about its content (assuming it didn't include a reward or threat). I would still be free to either accept or reject that prediction (i.e., to drink either tea or coffee) and there would be no inconsistency in either outcome.

Mainstream compatibilist theories spoil this insight when they attempt to theorize the question of agency (and its internal conceptual link with practical deliberation) from within the theoretical stance and hence reify desires, wants and dispositions as some sorts of psychological forces that determine action. — Pierre-Normand

The ghost in the machine.

I always had this problem with "compatibilism". Free will requires that the "choice" is not totally conditioned by the past events whereas determinism implies that when the "initial conditions" are fixed (or better: when the state of the system is fixed at a certain time) then all events are "fixed". — boundless

It's a difference of definitions. As I use the term, free will means one can intentionally drink tea rather than coffee because that is what one wants to do. As distinct from situations where that freedom is absent, e.g., when there are no options or when one is forced to do something against their will.

I think that reflects ordinary, pragmatic usage and is not precluded by a universe that evolves deterministically.

It implies that even if you have a completely deterministic description of the universe which predicts I will drink tea, I am not bound by that description. Instead the correctness (or incorrectness) of the description depends on my choice to drink tea (or not).

How does Copenhagen describe the cat in the box then? The cat is in superposition, both dead and alive, despite the measurement being taken from the cat POV. I realize that is a relational description, but I've known no other even before I knew the name for it. — noAxioms

Per Copenhagen, if the cat (or the Geiger counter) does the measurement then it is not described as being in superposition, only the atom is. And regarding the atom, the wave function is just a tool for calculating probabilities, nothing more. So asking about reality beyond what is observed is a meaningless question.

Relational also denies the latter it seems. The other outcomes don't exist in relation to any observation. — noAxioms

It would seem so, but I'm not really sure. Per RQM, the quantum state continues to evolve unitarily for an external non-interacting observer (i.e., the superposition is maintained) while at the same time the quantum state reduces to a single definite outcome for the interacting observer (where that outcome is undefined, not merely unknown, for the non-interacting observer).

That difference in perspective is easily accounted for in MWI. But it's not clear to me whether RQM allows multiple outcomes or not. If so, then it seems to be essentially MWI in different language. If not, then what explains interference?

Conway game of life is such a structure. Not a physical thing, just formal construct. It does however have physical things in it, with particles that zoom around at varying speeds with casual laws, etc. — noAxioms

If Conway's Game of Life is instantiated on a computer, then gliders and the like emerge. But without that instantiation, it's just a formal construct where nothing happens at all.

In fact what MWI says is that all the possible outcomes occur and at the classical level there is determinism, so IMO it has the same problem of "classical determinism" if what you say is right ;) — boundless

MWI says that the quantum states with non-zero amplitude all occur, so that is the level that is deterministic. As I've argued, our everyday ostensive possibilities don't all occur.

Well yes, I admit you are right and I am defeated :lol: but at the same time the unitary evolution of the Schroedinger equation implies that "all possibilities occur". So FW is incompatilble with MWI (well for that matter is incompatible with all theories in science)... IMO this is one of the reasons why I do not think reality is (only) mathematical, like MWI esplictly holds. At least other interpretations do not go so far. — boundless

Free will isn't incompatible with MWI (or deterministic theories in general). It is the dynamic systems themselves that are driving things, not the equations. The equations merely describe and predict (rightly or wrongly) what the systems will do.

Thank you for the insights! — boundless

And thank you for yours!

Wait, how is a collapse-interpretation not unitary? Unitary seems to mean that probabilities of various outcomes of measurements add up to 1. — noAxioms

Collapse doesn't preserve the norm of the state vector so it's a non-unitary transformation. It reduces the superposition state to just one of the relative states which had a probability less than 1.

I always wondered how they detect superposition of say macroscopic states. They put some object (a small bar just large enough to see unaided) into a superposition of vibrating and not. I didn't get from the article how they knew this state had been achieved. — noAxioms

One way is to look for interference effects (as in the double-slit and Mach-Zehnder interferometer experiments). Another way is to do repeated measurements and see if the results conform to the probabilities predicted by QM for measuring each relative state in superposition. That's the case here - they repeatedly put the metal bar into an excited state that decays as a superposition into the ground state and measured the state after different delay times.

The interpretations with which I am familiar say the photons are both there, in superposition, so long as they've not been measured. It is only after measurement where they differ. Mostly talking about collapse or not interpretations. Copenhagen is mutually exclusive with MWI only in its choice of reality against which the state is defined. If reality is a relation, this is no more contradictory than my location being both north-of and south-of something. Just different things. — noAxioms

Actually Copenhagen takes an instrumentalist view of the wave function and so denies there is ever more than one photon. And Bohm says that there is only ever one photon whether measured or not (the photon rides the wave, so to speak).

Defining reality as a relation only shifts the basic claim. The claim now is whether there is one measured outcome or whether there is a measured outcome for each relative state. Copenhagen and Bohm (and most other interpretations) deny the latter, contrary to MWI.

If the physical universe is a mathematical structure, and humans are part of it, and not something separate from it but interacting, then humans are 'in' the structure, just like my engine is in my car. How is that a category mistake? — noAxioms

A mathematical structure is a formal construct not a physical thing. The analogy is saying that your engine is in an equation. Of course we could, in principal, describe your car with a formal equation. But the form of the car is not the car. The car has materiality and substance that the equation does not.

I don't disagree, but this is already stepping into interpretation territory. QM doesn't say what the states actually do. — noAxioms

Unitary QM does. If a quantum state describes a photon being emitted towards a 50/50 beam splitter then, per the Schrodinger equation, this initial quantum state evolves into a superposition of two quantum states with one state describing a transmitted photon and the other state describing a reflected photon.

Other interpretations provide different accounts because they alter or add to unitary QM in some way (e.g., adding collapse).

They can both be correct. The wave function in its simplest form exists in relation to the whole structure of the Schroedinger equation for any closed system, but it exists in collapsed form for any isolated quantum state such as the point of view a human subjective view. These are just different relations, not mutually exclusive interpretations, at least one of which is necessarily wrong. — noAxioms

There are either two photons emerging from the beam splitter in the scenario I described above (per unitary QM) or just one (per most other interpretations). Aren't they mutually exclusive claims?

Yes, it is this unnecessary breathing of fire that I'm talking about. Is such a structure real, in that Platonic sense? Turns out it doesn't matter. The human in the mathematical structure will behave identically, asking the same questions about the same experience, whether or not there is some ontological status to the structure itself. That designation does not in any way alter the structure.

In a way I find myself to be a reverse Platonist. I believed numbers to be real for a while, but now I favor a view that ontic structural realism, where yes, we perhaps share the same ontology as those numbers, not that the numbers must exist, but that the existence of our universe is required much in the same way that numbers don't need it. OSR says we're made of the same stuff, so it presumes the two have the same ontology, but it doesn't presume that shared status must be some kind of objective existence. — noAxioms

OK, but the theory still has to be coherent. I think it's a category mistake to talk about "the human in the mathematical structure..." or to presume that humans and numbers have the same ontology.

Ok, with this I agree. In fact the problem arises with the interpretation of the Schroedinger equation. If you accept it as the "reality", then of course all branches are as real as ours. However, if we accept from the beginning that the wave-function is epistemic and not ontic, then the relation between "potential" and "actual" becomes much more relavant. — boundless

OK, but that would seem to require giving up realism. Physics World has a good analysis of the current thinking on psi-epistemic theories (quote below):

Pusey, Barrett and Rudolph's theorem, which has come to be known as the PBR theorem, essentially offers an ultimatum. If quantum mechanics is right, then the wavefunction cannot be epistemic - it cannot merely represent an experimentalist's partial knowledge about reality. It must instead be ontic and directly correspond either to part of reality (as Bohm said) or to reality in full (as Everett said). — The life of psi - Jon Cartwright

Regarding the "non-scientific reasons"... Well consider ethical responsibility. The reason why we give importance to ethics relies on the fact that we have to choose everytime what to do. We have to make up decisions. With determinism we are completely helpless: we think we have the possibility to choose but in fact we have not that possibility. Every movement and every thought in fact is simply "necessary".

Of course determinism is not the "view" of MWI ... — boundless

The Schrodinger equation is deterministic but it is descriptive/predictive not prescriptive. That I predictably drink tea rather than coffee doesn't imply I don't freely choose tea. And showing me an equation predicting that I will drink tea wouldn't prevent me from drinking coffee on that occasion.

I concede that energy conservation is not a problem for MWI, but what about the splitting and consciousness? There is a continuous creation of "subjects" every moment. And here we have a quite inelegant consequence - there is a multiplication of "sentient beings" among other things. — boundless

Yes, it would be a natural fissioning process (like amoeba fissioning). Merging can also potentially occur (i.e., interference). While it's admittedly a problem for people's preconceptions, it's not a problem for MWI.

Also, if it is possible according to MWI that "boundless" commits a crime and we observe he does not, then we know that necessarily another "clone" of "boundless" committed the crime. — boundless

Yes, but only if it is possible according to MWI, i.e., only if such a possibility hinges on a quantum event. Whereas I think a person's intentional choices demonstrably resolve at a higher level than quantum events. For example, I don't find myself inexplicably drinking coffee instead of tea half the time even though the choice to drink coffee is an ostensive possibility. So what we would regard as possible outcomes and what quantum outcomes actually occur are very different things.

In fact virtue becomes relevant when X can decide to follow it and not to follow "vice". In MWI X follows vice and virtue in two different stories. Both the virtuous and the vicious are "two outcomes" of the wavefunction. . If both choices are a possibility then in two different "worlds" Xs choose both. And the existence of the virtuous X depends on the existence of vicious X. So actually every time all (possibile) good and bad choices are actualized. — boundless

I think your analysis here assumes that choices under MWI result in branching. But our ordinary experiences with making choices don't exhibit the uncertain outcomes that one would expect if branching did occur. Consider the MZI experiment where, on a classical understanding, the photons should have a 50/50 chance of ending up at either detector. Yet the experiment can be setup such that all the photons end up at only one of the detectors. I think this is analogous to the single outcome that reasoning and intentional choice converge on and so the outcomes of our choices aren't actually probabilistic or random. To get multiple outcomes, we would instead need to make the choice contingent on a quantum event (e.g., if spin-up is detected, drink tea; if spin-down is detected, drink coffee).

Yes.

I see what you mean. But at the same time, conflating the "actual" and the "potential" can appear to be inelegant in its way. — boundless

Yes. So what I'm getting at is that a notion of res potentia (i.e., a dualistic substance) does not arise in the Schrodinger equation. As far as the Schrodinger equation is concerned, the quantum state continues to evolve unitarily regardless of observed measurement outcomes, with each state equally physical.

Positing an invisible and undetectable res potentia (whether for the wave function itself or just the unobserved states) seems to be a purely semantic move and not one that is motivated by the Schrodinger equation itself.

In any case, if this perspective is used then one must accept MUH (Mathemaical Universe Hypothesis). — boundless

Not necessarily. MUH is an example of Platonic realism about universals. In his paper, Tegmark says:

Stephen Hawking famously asked "what is it that breathes fire into the equations and makes a universe for them to describe?" In the context of the MUH, there is thus no breathing required, since the point is not that a mathematical structure describes a universe, but that it is a universe. — Max Tegmark - The Mathematical Universe

Whereas I accept Aristotle's immanent realism about universals. That is, the universe is substantial (matter and form), not merely formal.

Since the apple does not appear "red" if we close our eyes, then its colour is not a "property" of the apple itself, but of our perception of it — boundless

Note that the apple also doesn't appear solid if I'm not looking at or touching it. Yet it doesn't follow that it's not solid. Properties of things are identified in experience, but are real independent of experience. That's the nature of language abstraction.

So, in normal usage, there is nothing wrong with saying that the apple appears green but is actually red (e.g., because of background lighting or filter glasses). Or that the apple in the dark, sealed box is red. Whereas it would be wrong to say that it appears red when no-one is looking, or when there is no light, since "appears" refers to perceptual experience, not the object.

Even if we accept "mathematical realism" we can think about different "levels" of reality: the other branches exist potentially, and not actually. I concur that this solution appears inelegant, mathematically. — boundless

Yes, the problem is that that distinction doesn't arise in the mathematics - each relative state is treated equivalently. So why make such a distinction? As I suggested in another post, it seems like taking a heliocentric model and packaging it as geocentric.

Also the idea that "what is mathematical is actually existing" presupposes that (1) our world is no different from a mathematical structure (2) that the mathematics we "use" is a perfect representation of the "actual existing". — boundless

Yes, in the Aristotelian sense that the universe has a nature (form) and we are seeking to discover it.

There are several other reasons for my not acceptance of MWI. But in this discussion are quite useless, so I do not write them (unless one is VERY curious and VERY patient to read them, of course ;) ). — boundless

Feel free to write them - I'd be interested.

It came to be called ‘the many worlds theory’ because according to it there are an infinite number of universes which allow all possible observations to be realised in one of those universes. — Wayfarer

I think you're getting needlessly distracted by the idea of "infinite universes". Unitary quantum mechanics postulates only one universe and it is described by the universal wave function. Given the premise (which I accept) that the universe has a finite age, size and divisibility, there can only be a finite number of branches. I recommend reading Max Tegmark's, "Infinity Is a Beautiful Concept – And It's Ruining Physics". As he says, "This means that today's best theories need a major shakeup by retiring an incorrect assumption. Which one? Here’s my prime suspect: infinity."

So, in line with the principle that ‘drastic problems call for drastic solutions’, the question I asked is, if as drastic a solution as ‘many universes’ is warranted, what is the drastic problem that it is responding to? ‘If the many-worlds formulation were found to be impossible in principle, then we would be obliged to accept that: ...’ — Wayfarer

... the theory is wrong and so back to the drawing board.

Now let me try to explain as clearly as I can why Everett seems likely to be correct.

The problem is to account for observed quantum phenomena. Unitary quantum mechanics (a.k.a. Everettian QM) does that in a simple and elegant way with only two postulates. It does not postulate many worlds, they are emergent in the theory.

Every quantum interpretation depends on unitary quantum mechanics. If the emergent worlds are not desired, then the general strategy is to add postulates until they go away, while being careful to continue matching the predictions of unitary quantum mechanics.

So your question could be put in another way. Why is it so important to match people's prior expectations about how the universe should be? Both Bohmian Mechanics and the various collapse interpretations are analagous to utilizing the heliocentric model to make all the predictions and then packaging it as a geocentric model. Alternatively, we could all accept that the underlying predictive model just seems to be the correct theory.

A "potential world" (what we see in our minds as virtual action) does not entail an actual world (the MWI) solution. — Rich

Yet despite not being actual, it has actual effects. This is why Bohmian Mechanics requires two equations. The wave equation to describe the quantum potential. And the guiding equation to describe the potential's effect on actual particles.

As I see it, this is analogous to Descartes' res cogitans and res extensa where the mind guides the body. Would you agree with that analogy?

On the Everettian model, there are just particles and the wave equation is sufficient to describe their dynamics. There is no need for a superfluous guiding equation.

In other words, why was it necessary for Everett to propose an hypotheses comprising the apparently radical speculation of ‘infinitely branching universes’? If it turned out not to be tenable, what would we be obliged to accept? — Wayfarer

Everett's theory is just unitary quantum mechanics [*]. Everett was the first to realize that it predicted many worlds (his term was "relative states") when understood as a realist theory. If unitary QM were to be falsified by experiment, then a different theory with different predictions would be required. For example, a dynamical collapse theory like GRW.

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[*] Unitary quantum mechanics includes only two postulates and is common to every interpretation of quantum mechanics.