Of course, the most important reason for adopting Many Worlds:

There exists no alternative explanatory theory to Everett-interpreted quantum mechanics which can reproduce the predictions of quantum theory.

Don't take MW seriously, just take the Schrödinger Equation seriously! — tom

Surprising that the Deutsch acolyte would chime in on this one. ;-)

There needs to be empirical evidence backing it up at some point, or else it will always remain an interpretation. If no empirical evidence can ever be given, then it's not scientific, but it's rather metaphysics, akin to saying we're living inside a simulation. — Marchesk

Yeah, exactly.

So they believe in a real, physical infinity, as opposed to a mathematical infinity? I thought infinities in physics meant there was a problem with the theory requiring revision. — Marchesk

Infinite space? Of course. Whether it's "real" and "physical" is down to semantics, I guess*. But the idea that space is infinite is old and, I would think, much less controversial than its opposite. We only got a good grip on the latter concept (of finite space) recently, with the development of topology and modern cosmology. Otherwise it is rather hard to imagine, intuitively.

I forgot which ancient Greek philosopher it was that argued that space must be infinite, because suppose that it rather had a boundary; then on reaching that boundary you could just poke a stick through it.

* But if you think that space is somehow not physical or not real or doesn't count for some other reason, well, once you suppose that space is infinite, it is only natural to suppose that there's an infinite amount of stuff in it - stars, galaxies, etc. - and that's as real and physical as it gets, right? The alternative would violate the Copernican principle, making our finite pocket of the infinite universe very special for no good reason.

The old argument from personal incredulity! — tom

Yeah, that's the worst possible reason for rejecting some physics or even an interpretation: that it is strange, incredible, etc. - especially for a wannabe philosopher. I mean, if nothing else, the last 400 or so years of discovery should have taught us that the world is stranger than we can even imagine.

Motion does not have to be constantly sustained by a mover? What have you been smoking, Galileo? :-}

Motion does not have to be constantly sustained by a mover? What have you been smoking, Galileo? :-} — SophistiCat

I actually had a guy from Pakistan the US military was teaching nuclear reactor physics too call me a liar when I casually pointed out heavy objects don't fall faster than lighter ones.

"The Interpretation of Quantum Mechanics: Dublin Seminars (1949-1955) and Other Unpublished Essays" Schrödinger

Thanks. I haven't found that particular book yet, although there's an extensive discussion of the comparison between Schrodinger and Everett's views in Schrodinger's Philosophy of Quantum Mechanics, Michel Bitbol. It speaks of Schrodinger's adoption of Advaita Vedanta in combination with the philosophy of Schopenhauer, to produce a kind of mystical monism, in which Mind (capital M) is the primary reality. It notes many similarities between the relative state formulation and Schrodinger's wave equation, but also says that:



So, again, because Everett (and Deutsch, and Tegmark) are physicalists, they can only conceive of 'what is real' in terms of what is physical. So their 'many observers' actually do exist, in really-existing parallel worlds. Whereas, here, Schrodinger's philosophy accomodates 'One Mind which may adopt any one of the available points of view'. And that is 'a difference that makes a difference'.

All quantum interference experiments are evidence of Many Worlds. — Tom

@Tom - could I put the question to you: what problem is the 'many worlds' interpretation a solution for? Why is it necessary to invoke 'many worlds'? — Wayfarer

'Many worlds' is a solution for why we observe quantum interference patterns.

When a single photon is fired in the double-slit experiment, the probability that it will be detected at any particular position on the back screen can be calculated by summing over all the possible photon paths to that position.

In MWI, those photon paths are not merely possible, but real. That is, each path is traversed by a photon in a separate world branch. When a photon is observed on the back screen, that is the result of world branches combining in superposition which causes an interference effect.

The difficulty for other interpretations is how to explain those interference effects if the paths are not real. How can merely possible photon paths cause a real interference effect?

I get that. The problem that I think MWI is meant to solve is that of the 'wave function collapse': which is that, until the measurement is made, the object has no specific position, its position being described probabilistically by the wave equation. The act of measurement 'collapses' the possibility of it being in any other position except where it is at that moment.

So what the many-worlds intepretation does, is to say that it is also in all those other positions, which are viewed or at least viewable by other observers.

The trouble is, I just think it is consequence of the fact that Everett can't accomodate the idea of a mere observation having causal consequences. To admit that, undermines the principle of the 'causal closure of the physical'. It seems to suggest that simply observing something has physical consequences, which is central to the so-called Copenhagen intepretation. So it solves that 'problem' - but at what cost?

Under MWI, observations do have causal consequences. An observation entangles the observer with objects on a particular world branch.

The real objection, I think, which is the objection that Einstein had, is that the Copenhagen Interpretation entails a rejection of realism. That is, does the world, in some sense, depend on the mind? Does God play dice? Does the moon only exist when you look at it? Is there spooky action at a distance?

Under MWI, these are all trivially answered in the negative. It is an interpretation that is highly explanatory. Whereas the Copenhagen Interpretation is not well-defined and does not explain why quantum interference effects occur.

Thanks - that's pretty close to what I thought, but I don't understand your first point, 'an observation entangles the observer with objects on a particular world branch'. I had thought 'entanglement' was what Einstein meant when he spoke of 'spooky action at a distance'. What does 'entangling an observer with objects' mean? How does that manifest?

You say that MWI is 'highly explanatory' - it may be, but at the cost of assuming an infinite number of parallel universes.

When Everett first showed his paper to Wheeler, 'Wheeler was troubled by Everett’s use of “splitting” humans and cannonballs as scientific metaphors. ...In April 1957 Everett’s thesis committee accepted the abridged version—without the “splits.” Three months later Reviews of Modern Physics published the shortened version, entitled “‘Relative State’ Formulation of Quantum Mechanics.” The same article hints that Bohr never accepted the idea of a real 'split' or plurality of worlds, that perhaps he thought it was intended as an allegory. 'In the spring of 1959 Bohr granted Everett an interview in Copenhagen. They met several times during a six-week period but to little effect: Bohr did not shift his position, and Everett did not reenter quantum physics research.'

https://www.scientificamerican.com/article/hugh-everett-biography/

Thanks - that's pretty close to what I thought, but I don't understand your first point, 'an observation entangles the observer with objects on a particular world branch'. I had thought 'entanglement' was what Einstein meant when he spoke of 'spooky action at a distance'. What does 'entangling an observer with objects' mean? How does that manifest? — Wayfarer

Under MWI, entanglement is just correlation. In terms of the EPR experiment, there will be a pair of correlated opposite-spin particles on one branch and another pair on another branch and these branches are in superposition. When Alice observes the first particle, a process of decoherence occurs whereby Alice becomes correlated with the pair of particles on one branch (and similarly on the other branch). There is no spooky action at a distance because there is no action happening between the particles at all.

You say that MWI is 'highly explanatory' - it may be, but at the cost of assuming an infinite number of parallel universes. — Wayfarer

Not necessarily infinite. But, yes, a lot. The branching isn't assumed. It's just the natural interpretation. That's what the summing over paths is about. The difficulty is in coming up with a coherent interpretation that omits the other branches. If the other branches aren't real, then what causes the interference effects?

Under MWI, entanglement is just correlation. In terms of the EPR experiment, there will be a pair of correlated opposite-spin particles on one branch and another pair on another branch and these branches are in superposition. When Alice observes the first particle, a process of decoherence occurs whereby Alice becomes correlated with the pair of particles on one branch (and similarly on the other branch). There is no spooky action at a distance because there is no action happening between the particles at all. — Andrew M

Under MW, entanglement is not just a (statistical) correlation. "Correlation" is the wrong word. It is the anti-explanatory word used by anti-realists to avoid any questions about why their algorithm works, particularly as the algorithm does not apply to reality, but rather what can be said about reality.

Rather, under MW, the physical mechanism by which the right branches encounter each other - in order to preserve conservation laws etc - is termed "information flow" or something similar. The process was fully worked out here: http://xxx.lanl.gov/abs/quant-ph/9906007

The difficulty is in coming up with a coherent interpretation that omits the other branches. If the other branches aren't real, then what causes the interference effects? — Andrew M

Quite!

Denial is always an option however, and to be consistent, the Copenhagen Interpretation denies all the branches!

Of course "branching" is just shorthand. What troubled Wheeler was branching-by-splitting, which not the current understanding of branching.

If the other branches aren't real, then what causes the interference effects? — AndrewM

I think 'we don't know' is the superior answer. Physics is getting hopelessly entangled in pseudo-metaphysics, Everett's being an egregious example. A dose of humility and a sense of the limitations of science might be preferable.

The branching isn't assumed. It's just the natural interpretation. That's what the summing over paths is about. The difficulty is in coming up with a coherent interpretation that omits the other branches. If the other branches aren't real, then what causes the interference effects? — Andrew M

The branching is an artifact of quantum mechanics still being formulated using classical mathematics when all the evidence, including macroscopic evidence, indicates nature is fundamentally analog and what is required, at the very least, is some sort of fuzzy logic variation on the excluded middle. That includes modern quantum mechanics which are formulated as wave mechanics according to the Schrodinger Equation.

My own belief, is the law of identity is going down the nearest convenient rabbit hole or toilet of your personal preference. Hence, the reason quantum mechanics are formulated in infinite Hilbert spaces, yet, the same mathematics display no preference for the arrow of time and the last hold-out for the arrow of time, the second law of thermodynamics, has proven to be violated experimentally the smaller anything becomes. Time is running backwards on smaller scales indicating that the contents of the past are synergistically producing contents in their own future which, in turn, is normalizing the contents of the past with the overall effect sometimes resembling infinite universes merging into one and, at other times, resembling the future determining its own past.

We simply don't see broken eggs reassembling themselves because the human mind doesn't work backwards.

The branching is an artifact of quantum mechanics still being formulated using classical mathematics when all the evidence, including macroscopic evidence, indicates nature is fundamentally analog and what is required, at the very least, is some sort of fuzzy logic variation on the excluded middle. That includes modern quantum mechanics which are formulated as wave mechanics according to the Schrodinger Equation. — wuliheron

Yep. But then MWI seems to be an example of applying fuzzy logic interpretations to those successful mathematical formalisms. Which would be ironic.

So the maths can't provide an actual (ie: real) wavefunction collapse. Your interpretive choice then is whether (1) to affirm that there must be a collapse to one-world classicality that so far has escaped out mathematical models, or (2) argue for a no-collapse reality and ride that to wherever it logically leads, like MWI, or (3) argue for strong agnosticism about the true nature of reality as with an instrumentalist version of Copenhagen.

And we are seeing MWI being defended in very fuzzy terms with talk of interactions, correlations, interferences, branches, and other such stuff happening causally across world lines. So concrete sounding mechanisms are being invoked, while at the same time the latest decoherence versions of MWI seem to get squirrely about what any of this talk means in a definite physical sense. The other worlds "don't really exist", just as the collapse "doesn't really happen".

So the charitable view is that MWI is part of the exercise of giving up fairly completely on our classical expectations about how reality works. In some way, the whole of existence is a thermal ensemble of evolving possibility with an emergently classical character. But nothing can be completely pinned down or localised.

So in some sense the very notion of "to exist" has to reflect that reality is fundamentally contextual and can feel the shadowy presence of all its alternatives - all its possible worlds - even as it hovers fitfully around some general emergent equilbrium balance of that ocean of possibility.

In that light, both hard and definite collapse scenarios, and hard and definite no-collapse/many real worlds scenarios, are too strong as interpretations. Existence is to be found somewhere between the bounds of the one and the many.

An approach to MWI I find appealing is Chad Orzel's - http://scienceblogs.com/principles/2008/11/20/manyworlds-and-decoherence/

He emphasises that in a twin slit experiment, every photon has a slightly different thermal history or context as it passes through the array.

What you get depends on exactly what went on when you sent a particular photon in. A little gust of wind might result in a slightly higher air density, leading to a bigger phase shift. Another gust might lower the density, leading to a smaller phase shift. Every time you run the experiment, the shift will be slightly different.

So at a deep level, every photon has a spooky "completely entangled' connection. Yet at the emergent quasi-classical level, the world is varying enough to wash away the effect of these entanglements. Although you can arrange your experiment to also stop the entanglements being washed away and - now tilting the statistical ensemble the other way - present an accumulation of photon events that have the spooky connected pattern.

So the warring interpretations want to have it clean cut as being one or the other. Either there is one world spun of definite collapses, or many worlds spawned because of no-collapse. But a thermal realism says no world is perfect for any actual photon. It is always either relatively strongly entangled or relatively weakly entangled, depending on the amount of "perfect control" there is over the identicality of real world conditions.

That is, the context itself is varying or fuzzy at all times. Only an impossibly perfect and regular context could "manufacture" the kind of pure spookiness that hard-line approaches to MWI would demand. The "world" is itself never certain enough to justify the ontic demands of the no-collapse camp, just as much as an actual collapse view yielding a single classical world is also out of the question.

A parallel in thermodynamics might be the opposing notions of absolute thermal order that would be represented by the two possible minimum entropy organisations of a perfect gas. A highest state of order would be all the particles collected in the one corner of the jar - from where they would spread out randomly. But then the opposite perfect bound would be to start with every particle having an exact grid-like spacing - spread out as regularly as possible. Again, as soon as released, randomness would scramble that initial state very quickly (and much more quickly in fact that if the gas has to diffuse from one corner).

So that is an example of how real thermodynamics is about equilibrium states that are some thermal balance which is measured relative to two opposing perfect bounds. And with MWI, the collapse vs the no-collapse positions on quantum maths represent the single perfectly classical world and the unlimited perfectly entangled quantum world-lines of which our own world is the messy actual reality that exists between two impossible states of perfection.

There is huge uncertainty/contextuality at the local particle event level. But also that context has an always present residual uncertainty itself.

So as Orzel argues, we have to both accept spookiness as fundamental, but then not jump to treating it as itself something that has absolutely definite existence. Even the spookiness is relative to what emergently exists. The world in effect exists by suppressing the spookiness. It is not the spookiness that rules in a way that produces some unlimited number of actually branching world-lines, with their then fundamentally mysterious multiple "observers" experiencing different "collapses".

Orzel again...

Why do we talk about decoherence as if it produced “separate universes?” It’s really a matter of mathematical convenience. If you really wanted to be perverse, and keep track of absolutely everything, the proper description is a really huge wavefunction including that includes pieces for both photon paths, and also pieces for all of the possible outcomes of all of the possible interactions for each piece of the photon wavefunction as it travels along the path. You’d run out of ink and paper pretty quickly if you tried to write all of that down.

Since the end result is indistinguishable from a situation in which you have particles that took one of two definite paths, it’s much easier to think of it that way. And since those two paths no longer seem to exert any influence on one another– the probability is 50% for each detector, no matter what you do to the relative lengths– it’s as if those two possibilities exist in “separate universes,” with no communication between them.

In reality, though, there are no separate universes. There’s a single wavefunction, in a superposition of many states, with the number of states involved increasing exponentially all the time. The sheer complexity of it prevents us from seeing the clean and obvious interference effects that are the signature of quantum behavior, but that’s really only a practical limitation.

Questions of the form “At what point does such-and-so situation cause the creation of a new universe?” are thus really asking “At what point does such-and-so situation stop leading to detectable interference between branches of the wavefunction?” The answer is, pretty much, “Whenever the random phase shifts between those branches build up to the point where they’re large enough to obscure the interference.” Which is both kind of circular and highly dependent on the specifics of the situation in question, but it’s the best I can do.

I'm going with (3).

That's close to my own thinking, but was obviously written before the discovery that the second law of thermodynamics is violated more frequently the smaller anything becomes and completely ignores the Quantum Zeno Effect. The simplest explanation is that time can flow both forwards and backwards because a context without significant content and any content without a greater context is a demonstrable contradiction. In other words, the synergy of the contents of the past ensures the void of our future always has some significant amount of content making our lives appear fated at times, while that content in the future normalizes our past, ironically, ensuring that our lives are not entirely fated. Its enough to make Zeno's head spin, but its a more Asian metaphoric take on the issue.

You do realise that that makes you a super-strength pragmatist? :)

You aren't thinking of yourself as a CI proponent in the "consciousness causes collapse" sense? - https://en.wikipedia.org/wiki/Von_Neumann%E2%80%93Wigner_interpretation

Um, I think I'm nearer to an 'objective idealist' (and Pierce comes up under that categorisation.) But I am a pragmatist about science, in that I believe its consequences are, or ought to be, utilitarian and practical; that, I think, is nearer the original meaning of techne.

As for that article - I am dubious about the proposition of consciousness 'causing' anything. I interpret the wave function as being an intellectual construction which is predictive. But I don't think that the sub-atomic particles really exist anywhere until the measurement is taken - it is more like they 'manifest' at the point of measurement; to observe it is to 'make it manifest'. I think Heidegger thought something like that also. What bugged Einstein is his native faith that reality was 'there anyway', whereas the Copenhagen advocates all said that in this matter, the line between observer and observed was no longer clear-cut and that sub-atomic particles have no 'observer-independent reality' or at any rate not one we can know. And I'm with them on that, as far as I can understand it.

(I am having the mischeivous thought, though, that perhaps there aren't any fundamental particles, or that physics itself will turn out not to be fundamental, but only one aspect of the phenomenal.)

And we are seeing MWI being defended in very fuzzy terms with talk of interactions, correlations, interferences, branches, — apokrisis

Really? Where?

Where is MW being "defended" by use of fuzzy terms?

That's close to my own thinking, but was obviously written before the discovery that the second law of thermodynamics is violated more frequently the smaller anything becomes and completely ignores the Quantum Zeno Effect. — wuliheron

I'm hardly ignoring the quantum zeno effect. Remember that that too requires "perfect watching" to stop the particle ever decaying. So it is both remarkable that we could slow down a decay, impossible that we could create the energy-demanding experimental conditions that would stop a decay.

The simplest explanation is that time can flow both forwards and backwards because a context without significant content and any content without a greater context is a demonstrable contradiction. — wuliheron

I'm all for some version of retrocausality. But you are invoking a globally general version that again betrays perfect world thinking and not the fuzzy logic approach that I would take.

So our bulk model of time and causality is best described by this kind of thinking I would say - http://discovermagazine.com/2015/june/18-tomorrow-never-was

This thermal view of time says the past is pretty much solid and decohered, the future is a bunch of open quantum possibilities. And then quantum retrocausality would be about very local and individual events which are criss-crossing this bulk picture.

The bulk seems definitely sorted in having a sharp split between past context and future events. But on the fine grain, past and future are connected because - as with quantum eraser experiments - the context can take a "long time" to become fixed in a way that then determines the actual shape of the wavefunction. It is only in retrospect that we can see all that went into its formation.

So again, rather than time/causality being either absolute in a uni-directional classical sense, or instead absolute in a quantum non-local or "both ways" sense, the real world dangles somewhere between these two perfect limits. It emerges as the equilbrated bulk behaviour.

. Its enough to make Zeno's head spin, but its a more Asian metaphoric take on the issue. — wuliheron

The trouble with Asian metaphors is that culturally they lack mathematical development. So they are inherently fuzzy in being verbal descriptions. At best, using proto-logical arguments, they are proto-mathematical.

So yes, it is my own argument that all early civilisations shared a fairly organic, symmetry-breaking, perspective on metaphysics. There are strong parallels between Anaximander and Tao.

But you can't claim quantum physics to be the triumph of the Eastern way over the Western way. It was Zeno who crystalise the mathematical paradoxes of a way of thinking, and thus made possible their equally sharp counter-reaction. You couldn't develop calculus unless you knew there was some sharp problem when it came to differentiating a curve. And you couldn't develop quantum mechanics if Lagrangian mechanics wasn't already a result of being able to do such differentiation.

So Zeno sparked something usefully concrete in Western thought. It allowed us to speak mathematically about the opposing limits on being. Asian philosophy just spoke about the fact that Yin and Yang gave you the I Ching - a proto-maths that was too fuzzy to ever go anywhere after that.

So I don't undervalue Eastern metaphysics. But there are reasons why Western metaphysics - in its built-in capacity to be "utterly wrong" via axiomatic mathematical claims - became the actually productive intellectual tradition.

Zeno made everyone's head spin for the next 2300 years. Asian metaphysics has since gone down the nearest toilet/rabbit hole even in Asia. Universities over there don't teach quantum theory any differently.

Rather than being defensive, why not critique Orzel from your point of view? That would be more interesting.

What bugged Einstein is his native faith that reality was 'there anyway', whereas the Copenhagen advocates all said that in this matter, the line between observer and observed was no longer clear-cut. And I'm with them on that, as far as I can understand it. — Wayfarer

CI itself comes in a rainbow of variants. But the central idea in my view is that in the end what we can be sure of is that we don't know how to define what looks like a necessary division between observers and observables when it comes to quantum scale observations of observables. So we know there is an explanatory gap, but can see no watertight way to fill it.

So CI says there is a line for sure. We sit on its classical side. And where that line gets drawn to rule off the quantum side is something we can't answer.

And my response to that is that it is this notion of there being a definite line which is questionable. Instead, I see the classical and the quantum as complementary models of the two perfect limits on existence. So CI gets it wrong in persisting in believing in a dividing line. Although, as I say, CI comes in so many varieties that it can be seen as a "shrug of a shoulders" intrumentalism even about hard line vs fuzzy line ontologies. Who cares because we can use the maths to deal with the world and built great machinery?

Then Peirce comes in here because he was already dealing with this precise problem - the nature of observers. And he extended that epistemological question to make it a ontological answer. His semiosis is a way of defining soft dividing lines in worlds where observers and observables are fundamentally entangled, but can - thermally - develop robust habitual divisions.

So you keep claiming Peirce to be an idealist - someone somehow arguing that divine mind conjures the world into being. And at stages in his life, he may have well wanted to believe that.

But if you look at his actual metaphysics - his semiotic approach - then he was talking about signs rather than minds. Observers weren't localised experiencers but contextual habits of interpretance. The difference might be subtle, but it is also huge.

I never really saw CI as instrumentalist. Though I mostly take it along the lines of Heisenberg and Bohr -- who never saw eye to eye. Heisenberg was something of a mathematical literalist and a formalist at the same time, from my reading. He didn't particularly seem to care that the findings of QM ran in contradiction to other physical sciences -- he seemed to believe that this was just another question to ask and answer. Whereas Bohr definitely took CI in a more idealist direction, with complementarity forming the core of his interpretation (of, after that, not just QM but everything)

These are just my impressions though, and impressions from memory at that. We always differentiated between instrumental interp from CI, though.

(EDIT: Not really challenging you, just asking for a comment)

We always differentiated between instrumental interp from CI, though. — Moliere

As you say, even if you go back to Bohr and Heisenberg, you can't recover some pure CI position. And perhaps I should have said pragmatist or logical positivist rather than instrumentalist initially - even though instrumentalism is only Dewey and Popper trying to strip down Peircean pragmatism of its "unfortunate" metaphysical leanings.

So I find that when I talk to modern proponents of CI, they are essentially arguing pragmatism - all we can know is that the maths sure works. And then the metaphysics that lingers at the back of this is the idea that the mind of the observer works on the classical side of the equation, so something that sure looks like a definite collapse of quantum weirdness must be the case in that we manage to extract classically understood measurements from the world (within the bounds of uncertainty).

So even the instrumentalism relies on a background metaphyics which I would say should be troubling. And it certainly was for Peirce who was working on a "fuzzy logic" view of metaphysics for just that reason.

Generally, I struggle to draw sharp lines between interpretations. But when given some central issue - like wavefunction collapse - people are going to divide quite logically into the three camps of (1) it must do, (2) no, it can't, and (3) can't know so learning not to care.

CI as people currently use it seems more 3 than 1 these days.

So the Copenhagen Interpretation says there is a line for sure. We sit on its classical side. And where that line gets drawn to rule off the quantum side is something we can't answer. — Apokrisis

I'm reading Quantum: Einstein, Bohr, and the Great Debate about the Nature of Reality, Manjit Kumar, on this topic.

Kumar quotes Bohr as saying:

Scientists had always conducted their experiments on the unspoken assumption that they were passive observers of nature, able to look without disturbing what they were looking at. There was a sharp distinction between object and subject, between the observer and observed. According to the Copenhagen Interpretation, this was not true in the atomic realm.

(p262)

Heisenberg, meanwhile, said:

Unlike objects in the everyday world, 'atoms or elementary particles are not as real; they form a world of potentialities rather than things or facts'

These ideas were considerably elaborated by Heisenberg in his later philosophical essays, such as The Debate between Plato and Democritus, where he comes down on the side of Plato. He also compares the nature of the existence of electrons to Aristotle's potentia, which makes sense to me; I've read elsewhere that electrons don't exist, they only have a tendency to exist.

But as I have often noted, when Heisenberg says that electrons are 'not as real', this poses an ontic challenge; surely, you will say, something is either real (exists, =1) or not (doesn't exist, =0). Notice that this is precisely what is being called into question here. And that is what bugs Einstein.

[Einstein] continued to believe in a reality where natural phenomena unfolded according to the laws of nature, independently of an observers.

'What we call science', he said, 'has the sole purpose of determining what is' Physics for him was an attempt to grasp reality, as it is, independent of observation. It is in this sense, he said, that 'one speaks of "physical reality" '.

(p262)

Now, I've realised what I think is wrong about this view. This is that science views reality through theories and hypotheses. And what I think Einstein is forgetting (and, hey, he's Einstein, so I know I'm saying a lot!) is that the kinds of purported facts that he is arguing about are only disclosed by a rational intelligence who is capable of interpreting the facts. So 'the facts' - and by extension, even the moon - don't exist irrespective of whether one is looking or not. 'Looking' is inextricably intertwined with what is being observed. That has always been the case, but it took 'the observer problem' for it to more or less come up and punch us in the nose!

There's an interesting article called When Einstein Met Tagore, which helps make this point.

EINSTEIN: Truth, then, or Beauty is not independent of Man?

TAGORE: No.

EINSTEIN: If there would be no human beings any more, the Apollo of Belvedere would no longer be beautiful.

TAGORE: No.

EINSTEIN: I agree with regard to this conception of Beauty, but not with regard to Truth.

TAGORE: Why not? Truth is realized through man.

EINSTEIN: I cannot prove that my conception is right, but that is my religion.

TAGORE: Beauty is in the ideal of perfect harmony which is in the Universal Being; Truth the perfect comprehension of the Universal Mind. We individuals approach it through our own mistakes and blunders, through our accumulated experiences, through our illumined consciousness — how, otherwise, can we know Truth?

EINSTEIN: I cannot prove scientifically that Truth must be conceived as a Truth that is valid independent of humanity; but I believe it firmly. I believe, for instance, that the Pythagorean theorem in geometry states something that is approximately true, independent of the existence of man.

But the point that I want to make, is that the Pythagorean theorem can only by known by a mind. So it's not mind-dependent, in the sense of being reliant or this or that mind, but in the sense of only being perceptible by a mind. So, what is, includes or implies a mind capable of grasping the truth! But that is what had been bracketed out of the scientific method by Galileo and his successors; this is where the idea of 'mind-independent' came from. So I think Einstein's conception of realism is at fault. Essentially, it doesn't want to recognize the limitations of science; saying that science sees 'things as they truly are' is a conceit.

CI as people currently use it seems more 3 than 1 these days. — apokrisis

Perhaps I fell into an odd camp, then. Though I learned it more from the Chem side than the physics side, though physics was part of it, so that might be why.

We went along with collapse was real, and it was the "observation" which made it real. But we didn't attach much significance to "observation", hence why I tend to go back to both H and B -- they both had different takes on it.

Rather than being defensive, why not critique Orzel from your point of view? That would be more interesting. — apokrisis

I note you are unable to defend your baseless claims.

Orzel's understanding of Many Worlds has improved over the years:

http://scienceblogs.com/principles/2015/02/20/the-philosophical-incoherence-of-too-many-worlds/

Under MW, entanglement is not just a (statistical) correlation. "Correlation" is the wrong word. It is the anti-explanatory word used by anti-realists to avoid any questions about why their algorithm works, particularly as the algorithm does not apply to reality, but rather what can be said about reality.

Rather, under MW, the physical mechanism by which the right branches encounter each other - in order to preserve conservation laws etc - is termed "information flow" or something similar. The process was fully worked out here: http://xxx.lanl.gov/abs/quant-ph/9906007 — tom

Yes, it's not merely statistical, it has a causal basis. My main point is that there is nothing mysterious about entangled particles under MW - it just means that they are on the same world branch. And if the observer becomes entangled with them, then they will also be on that world branch.