Not really interested. — Terrapin Station

Sure, I figured that out long ago.

Right, and my point was that this happens because mathematics is observational - manipulating and then reexamining a diagram can reveal new information. The difference, of course, is that we are observing our own (ideal) constructions, rather than something "out there" in the (actual) universe. — aletheist

So mathematics is "observational", whatever that means. We are "observing our own (ideal constructions)"

OK, so how did we manage to "observe our own ideal constructions" of phenomena that took 50 years to observe after their discovery?

We were talking about discoveries in (pure) mathematics, not physics. — aletheist

Maybe you could explain how the discovery of entanglement is a discovery in "(pure) mathematics" and not "physics" and why it therefore exist in the Reality?

So on your view, how we interpret mathematical equations as theories has implications for whether it's as if the scientific method never happened because _____ ? — Terrapin Station

I know coherence is not your strong point, but could you translate that into something less incoherent?

Explanation is an account of why something happens. I've just quoted Duhem, probably the main proponent of instrumentalism in the 20thC, who rejects that physical theories are explanatory. Do you have any cites to back up your contrary claim? — Andrew M

It's quite extraordinary. Everyone, both supporters and detractors of Instrumentalism know what it means, except supporters on this forum.

Strangely enough, it is possible even to treat Evolution instrumentally, despite there being nothing to shut-up-and-calculate.

This is confused because just how we interpret mathematical equations as theories and just what we do or do not count as an explanation has no implications for whether it is or isn't like "the scientific method never happened." — Terrapin Station

Because you are confused and wrong, let me spell it out:

Scientific theories are expressed in mathematics because that is the means by which deductions are most easily made - i.e. it is the expression of the theory that is most amenable to testing.

Of course, despite Galileo's proclamation, the theory of Evolution has not yet been expressed mathematically. The theory of Evolution is expressed in ordinary language, and is nonetheless as successful as any other fundamental theory - it provides a good (the only) explanation of what it purports to explain.

You are ignoring the scientific method. For you, it is as if it never happened.

Maybe you could explain the discovery of quantum entanglement in your instrumentalist terms?

Right, and my point was that this happens because mathematics is observational - manipulating and then reexamining a diagram can reveal new information. The difference, of course, is that we are observing our own (ideal) constructions, rather than something "out there" in the (actual) universe. — aletheist

Based on your ideas, how do you explain the discovery of quantum entanglement?

It's just a matter of what people consider an explanation or not. And a large percentage of relevant academics consider mathematical equations read instrumentally to be explanations. — Terrapin Station

It's like the scientific method never happened!

No instrumentalists regard equations as explanations. That is the entire point of their philosophy; the purpose of a theory is to predict the outcome of experiments. Instrumentalists build the LHC for no other reason than they want to predict what the LHC does. The experiments, and more importantly the theories, tell us nothing about the Reality.

The scientific method is fundamentally based on the conception of theories as explanation - statements about what exists in reality, how it behaves, and why. This conception is necessary for a coherent epistemology.

As every instrumentalist knows, there are an infinite number of "theories" i.e. non-explanatory mathematical equations that agree with observations. This is a feature of the underdetermination of the laws of physics.

By contrast, good explanations are extremely difficult to come by!

You didn't ask for an argument, and nor did I claim to have one. You asked for a hidden variable theory that agrees with the results of quantum mechanics. I provided what seems to be just that. — Michael

All is not what it seems!

The only mention of that I can find is by Antoine Suarez. I can't find any other sources that corroborate his findings, but I can find several that say that no experiment refutes Bohmian mechanics. — Michael

Nicolas Gisin performed the remarkable experiment, and yes Bohmians are full of claims, but none has ever made any progress in quantum mechanics - unlike the Everettians who can claim several remarkable discoveries. The lack of progress by Bohmians is discussed in this otherwise positive paper by Gisin:

https://arxiv.org/abs/1509.00767

But science (unlike philosophy it seems) does in fact progress, and a recent experiment involving entangled histories falsifies Bohm and supports Everett. It was the idea of Nobel prize winning physicist Frank Wilczek. This is a very easy to follow article with some explanation:

https://www.quantamagazine.org/20160428-entanglement-made-simple/

People are attributing that quotation to me, but I was quoting a passage from the BBC article that was the subject of the original post. And, hey, Lamarck's not done for yet - he passed some of his characteristics on to later generations — Wayfarer

Actually, Darwin also believed in inheritance of acquired traits as well! He was a Lamarckian!

"Every single person who died before Darwin published Origin of Species in 1859 was ignorant of humanity's origins, because they knew nothing of evolution." — Wayfarer

It's like Anaxemander and Pedocles never existed! Poor forgotten Jean-Baptiste Lamarck, except in France where he is regarded as the father of Evolution.

I don't understand them. I only know (from what's been said of them) that they add to the de Broglie–Bohm theory the one thing that it doesn't normally explain; particle creation and annihilation. If that is indeed what they do then they are non-local hidden variable theories that agree with the results of quantum mechanics up to at least quantum field theory. — Michael

I see. You don't have an argument, but you like playing buzzword bingo for points.

Here are some buzzwords:

Bell - local hidden variable theories do not agree with QM
Leggett - non-local hidden variable ...
Kochen-Specker - non-contextual hidden variable ...
Free Will Theorem - any hidden variable theory whatsoever ...
PBR - probabilistic distributions of any type of hidden variable theory ...

There is also a an experiment that had slipped my mind - the famous Before-Before experiment which refutes any Bohmian theory including relativistic versions.

What about this and this? — Michael

Maybe you could briefly describe those theories and indicate to what extent they are capable of dealing with particle interactions etc.

The strongest critic of Wallace in the book above is Adrian Kent, a Reader in quantum physics at Oxford. Here is how he summarises his criticism:

Wallace's strategy of axiomatizing a mathematically precise decision theory within a fuzzy Everettian quasiclassical ontology is incoherent. Moreover, Wallace's axioms are not constitutive of rationality either in Everettian quantum theory or in theories in which branchings and branch weights are precisely defined. In both cases, there exist coherent rational strategies that violate some of the axioms. — Adrian Kent — mcdoodle

It's difficult to address a criticism which is just a slur.

Anyway, Kent doesn't like MW. His solution is to append some extra mathematical structure to QM in order to make it a single-world theory. He is thus an advocate of hidden variables. The trouble with this is that no hidden variable theory that does not contradict QM exists.

So, Kent advocates changing the physics, because he does not like the implication of currently known physics.

I'm amazed the Deutsch-Wallace approach hinges on decision theory and assumptions about rationality. Decision theory is quite a hotly-debated topic in its own right so I wouldn't build a mountain on it. Well, maybe a rough algorithm for how people act, but no 100% right view. — mcdoodle

Maybe you should watch the video I linked to. Stochastic theories are normative! Very weird.

I have looked it up. And I've watched the clip Wayfarer provided above, thank you Wayfarer. Furthermore, I know very well what a variable is, and I know very well what it means for a variable to be hidden. And as I explained, I see many variables hidden behind mathematics, the mathematics making them appear as constants. — Metaphysician Undercover

So in a double-slit experiment with a particle, name the hidden variable.

You seem to be in some sort of state of denial, afraid to face the possible reality of non-locality. — Metaphysician Undercover

Name a non-local hidden variable theory that agrees with the results of quantum mechanics up to at least quantum field theory.

So, the point Andrew M, I am a metaphysician, not even a physicist, and I can identify numerous possible hidden variables, such as gravity, expansion of space, dark matter, dark energy, so I don't know how many possible hidden variables there really is. Very many I would say. From my perspective there is massive evidence for hidden variables. — Metaphysician Undercover

What you have demonstrated is that you haven't the first clue what is meant by the term "hidden variable". Look it up!

It's redundant to say there is no evidence for hidden variables. If there was evidence, they wouldn't be hidden. But "evidence" is a property of the mind which seeks relationships, it is not a property of the physical world. So evidence may be right in front of one's eyes, or even right on one's list of observations, but if that individual does not establish the appropriate relationships, it is not seen as evidence, and so it is claimed, "there is no evidence". — Metaphysician Undercover

Hidden variable theories are ruled out by the many no-go theorems: Bell, Leggett, Kochen-Specker, Free Will Theorem, PBR.

There is no existing hidden variable theory that is able to replicate the results of Quantum Mechanics up to electrodynamics and field theory. They don't work or don't exist.

All hidden variable theories disagree with quantum mechanics, so they are wrong.

I agree that the ontology of probability is interesting. This 'from 25 mins on' wasn't 'purely QM stuff' at all, though, it was a prolonged lecture about metaphysics. My view of philosophy is that you imagine all the best arguments people can put up against you, and you rebut them. In this lecture Deutsch seems instead to be imagining a series of feeble opponents who haven't considered the slightest subtlety in their position. Even an actuary has a defence to the notion of probability, let alone proponents of statistical mechanics and so on. — mcdoodle

But you haven't addressed a single one of his arguments.

Why isn't all this in a peer-reviewed paper where his intellectual equals like Wallace and Timpson could respond and critique it? — mcdoodle

Try this paper by Marletto.

https://arxiv.org/abs/1507.03287

or this paper where Deutsch invented the idea.

http://xxx.lanl.gov/abs/quant-ph/9906015

or this paper where Wallace defends Deutsch

https://arxiv.org/pdf/quant-ph/0303050.pdf

or this paper where Wallace improves Deutsch's argument

https://arxiv.org/pdf/quant-ph/0312157.pdf

or this paper where Wallace establishes the formal proof of Deutsch's idea

https://arxiv.org/pdf/0906.2718.pdf

Or chapters 5 and 6 of this book by Wallace:

https://www.amazon.co.uk/Emergent-Multiverse-Quantum-According-Interpretation/dp/0198707541

Because Everett considered the wave function to be real and the world as not inherently probabilistic. — Andrew M

You might like this:



From ~25mins for the purely QM stuff.

I thought it was claiming that a universal computing device can simulate every physical process? Not every physical process involves a machine, unless he's claiming that everything is a computing device, but you explicitly denied that he was stating that. — Terrapin Station

The universal machine can simulate every finite physical process.

Let's not forget that the main claim of 'many worlds' is that there are, in fact, many worlds. It's not simply mathematics, it's a metaphysic. — Wayfarer

it's not a claim, it is a testable deduction...for the umteenth time.

Some intellectual honesty would be a peasant surprise!

Because the CTD principle isn't supposed to be only about machines, is it? — Terrapin Station

It's only about machines.

I like how you respond to that, but completely ignore the problem that Deutsch only defines "computational equivalence" for machines in the paper that supposedly "proves" the CTD principle. — Terrapin Station

Why is that a problem?

Oh I get it, how do you know the machines exist when you're not looking at them.

Meanwhile my impression of MWI is that it's ad hoc to preserve determinism. — Terrapin Station

That is almost funny.

I made a list of the rather low-quality "criticisms" of many worlds, but I'm not sure where this fits in.

It doesn't seem to fit precisely with "criticism by personal incredulity" which cover almost everything. This one seems to be a combination (or should that be superposition) of "ignorance" + "willful misrepresentation".

Here's a test too see if I'm correct:

1. Name the ad-hoc modifications to QM employed by Many Worlds
2. Identify where it is non-deterministic.

So, the first quoted passage is incorrect, in your view? (I ask because it seems to contradict what you said in the post before). — Wayfarer

It's just standard guff written about an theory whose sole purpose is obfuscation and denial. I really couldn't care less about it, so can't be bothered forming an opinion. Save to say, the article makes the epistemic nature of Copenhagen explicit later on.

But these are all intepretations. When you say that something has or hasn't been falsified, all you're doing it is interpreting it in accordance with your chosen metaphysical view, which any statement about what the theory means must be. Everyone sees the same data, the only thing being discussed here is what it means. — Wayfarer

Your primary source of knowledge, Wikipedia, has articles on Bell's theorem etc.

Bell - local realism falsified
Leggett - non-local realism falsified

It has been shown by experiment that both local and non-local realist theories disagree with Reality. Quantum Mechanics has never been shown to disagree with Reality.

PBR - The wavefunction cannot be interpreted as a probability distribution over real states.

I don't believe any experiment has been performed to test PBR - i.e. to test whether reality agrees with Quantum Mechanics or any theory that regards the wavefunction as real probabilities, but no one doubts the result.

Actually, PBR does have implications for Many Worlds - it means Many Worlds is correct.

I interpret the wave-function as a distribution of probabilities. Is that not correct? — Wayfarer

To claim you have an "interpretation" of a topic you know so little about is bizarre.

The WIkipedia entry on the subject states that: — Wayfarer

In metaphysical terms, the Copenhagen interpretation views quantum mechanics as providing knowledge of phenomena, but not as pointing to 'really existing objects', which it regarded as residues of ordinary intuition.

Such joy being reduced to selecting quotes from the same wikipedia page!

Copenhagen, and neo-Copenhagen theories such as Consistent Histories, are purely epistemic. The wavefunction is not part of reality, and certainly collapse is not.

Do we really have to repeat these threads over and over again? Local realism and non-local realism have been falsified by several no-go theorems. Copenhagen survives because it is not a theory about what is real, rather it is a theory about what can be said about what is real. Many Worlds survives because the no-go theorems do not apply to it.

This is the whole point of the famous Bohr-Einstein debate. Einstein could not accept that QM was not about "elements of reality", whereas Bohr claimed "the quantum world does not exist".

And, as we have repeated, and repeated, a theory that is explicitly anti-realist cannot provide an explanation. The ONLY explanatory theory that exists, which agrees with QM all the way up through field theory and the Standard Model is Many Worlds.

A famous quote from Bohr:

There is no quantum world. There is only an abstract physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature

Of course, Einstein, Everett disagree, though I think Deepak Chopra agrees.

This blog is worth a look.

http://mattleifer.info/2011/11/20/can-the-quantum-state-be-interpreted-statistically/

But it's not. It is the result of a simple conjecture: 'hey, what if the wave collapse DOESN"T OCCUR?' — Wayfarer

You are misrepresenting QM:

Copenhagen - Wavefunction collapse does not occur.
Many Worlds - Wavefunction collapse does not occur
De Broglie-Bohm - Wavefunction collapse does not occur
Modal Theories - Wavefunction collapse does not occur
Relational Theory - Wavefunction collapse does not occur
Statistical Interp. - ....
Ensemble ...
Many Minds
Consistent Histories

Get the idea?

The only theories that ever employed wavefunction collapse as a process in nature are von Neumann's theory of consciousness causing collapse, GRW - which is NOT quantum mechanics and does NOT work, and the Transactional interpretation.

Oh, but of course, wavefunction collapse also happens to be falsified.

Bam! There's your slam-dunk McD. You're powerless in front of that. To oppose it is to be declared an 'enemy of reason'. — Wayfarer

Denial is always an option. People do it all the time, just ask a creationist.

At about 2:00 Deutsch says that the existence of computation explains the unreasonable efficacy of mathematics in the natural sciences. I really don't get that. No computer or computational process could exist were it not for mathematics in the first place. Isn't it putting the cart before the horse? How come 'computation' is assigned to this kind of quasi-deistic role in Deutsch's worldview? 'There is a law of nature that the universe is computable, or that a universal computer exists'. — Wayfarer

The point is that the mathematics that we can perform - including proofs - is determined by the laws of physics. This also goes for the computations that any physical system can perform. This is why some functions are computable, but most are not.

Life is essentially a computational process, which you claim can not exist prior to mathematics. While it seems that the timeless truths and objects of mathematics must have always existed, I'm not convinced that they cannot be regarded as novel at the time of their discovery, or rather, invention.

I'm trying to understand this simulation business. I am using the critical eye of Christopher Timpson in 'Quantum Information Theory and the foundation of Quantum Mechanics'. He argues that your/Deutsch's argument is a 'simulation fallacy': that simulation is not a like for like business. Here are a couple of directly relevant paragraphs. Do you have a Deutsch rebuttal to this line of argument? It's part of a wider case, as I grasp it, that Deutsch is conflating the mathematical and the physical in 'the Turing principle' through a misunderstanding (in Timpson's view) of the original thesis. — mcdoodle

A rebuttal of what? The claim that Shor's algorithm does not require an astronomically vast number of parallel processing channels in or order to work?

We already know, based on every QM experiment ever performed, particularly interference experiments, that the classical idea that there is only one universe is destroyed. Despite the mis-representations of Timpson, the argument is not that parallel processing takes place therefore there are parallel universes, but precisely the opposite!

Logically, the possibility of complex quantum computation adds nothing to the argument already made. It is because parallel universes exist, that quantum computation possible! Please don't forget, that we know of these universes, but we don't know how to make a quantum computer! Shor's algorithm hasn't actually worked yet!

It is probably worth pointing out, that quantum computers were discovered by Deutsch as a by-product of thinking about how to test Many Worlds.

Deutsch is on record stating that the main impact of the first quantum computer will be psychological. And if you follow the references in Timpson's thesis to Deutsch's book, he explicitely states that the argument from Shor's algorithm is for "psychological impact".

You should also read note 8 of Timpson's thesis.

Maybe he'd argue that everything is just a computing machine, but where is that argument? — Terrapin Station

He is explicitly opposed to that idea. You will enjoy the video, where he explains why.

The CTD-Principle is a discovery, that has been proved to hold for known physics. The discovery is that Reality has the surprising property of self-similarity: it is possible to simulate exactly the universe from within.

The meaning of "simulation" is defined explicitly in the paper everyone keeps ignoring:

http://www.daviddeutsch.org.uk/wp-content/deutsch85.pdf

Here's Deutsch explaining the CTD-Principle, in an accessible way, without mentioning it.

What does the principle mean by simulating a physical process? Does it mean replicate? Can a quantum computer replicate consciousness, the Big Bang, evolution, etc.? Or can it just perform some sort of representative algorithm?

I'm pretty sure that the very definition of a simulation is that it isn't the real thing. Simulated consciousness isn't consciousness, just as a simulated explosion isn't an explosion. — Michael

You only need a quantum computer to simulate processes involving quantum coherence, so a laptop or something similar is all that is needed to exactly simulate consciousness.

Evolution is classical, so a classical computer is all that is required. The Big-Bang would require a quantum computer to simulate exactly.

Clearly a simulation of the Big-Bang is not the real Big-Bang. A simulation of you however, would be you, just in the same way that an algorithm is the same algorithm whatever hardware is running it. You are an algorithm running on computationally universal hardware.

Whether this is true or not is highly contested by physicists to this day (Penrose, et al). — Question

The CTD-Principle is not contested, not even by Penrose. Can you spot Penrose's name on the paper that proved the CTD-Principle?

http://www.daviddeutsch.org.uk/wp-content/deutsch85.pdf

Penrose is a genius. He knows perfectly well that the known laws of physics obey the CTD-Principle and all that implies. This is why he denies that the known laws of physics operate in the human brain. He has been looking for new laws of physics that do not obey the CTD-Principle, with zero success.

All of Penrose's arguments that somehow the human brain can out Godel a computer have been debunked.

They would be no solution at all. But this would imply the QM formalism being either wrong or incomplete. And QM is a very well tested theory. — Andrew M

But you know that is an understatement by a very long way! Ignoring the fact that our culture and technology is based on QM -we spend hours a day interacting with it and through it, not even the LHC can detect a hint that there might be the slightest problem.

Then of course there is the fact that QM is full of surprises. How is it possible that a conjectured law to explain atomic spectra, should also reveal entanglement, superposition, teleportation, quantum computing and the multiverse? Luck?

The philosophical issue is whether mathematical equations provide insight into the world we live in, or whether they are mere Platonic abstractions that nonetheless may have instrumental value. — Andrew M

Instrumentalism, apart from being wrong for other reasons, cannot explain the surprises.

That is because you are a stranger to philosophy and reason.

The author of the book I recommended is a philosopher. David Wallace works in the philosophy department of Oxford Uni.

Here he is talking.

https://podcasts.ox.ac.uk/plurality-worlds

but when the initial decision is made to entertain the notion of many worlds, then a whole series of consequences flow on from that. But I'm sceptical of the very first assumption. Actually, I'm not just sceptical - I'm dismissive of it. I think it is a fantasy. Everett himself says he had been drinking when the idea came to him. 'Hey, what if all the outcomes are real?' — Wayfarer

If you dismiss Many Worlds, what theory do you replace it with?

Everett never mentioned Many Worlds in his publications, he focused on solving the measurement problem thus formulating quantum mechanics in a manner suitable for addressing quantum gravity.

Because you have never studied quantum mechanics, you keep claiming the many worlds are an assumption. This is pure ignorance. I'm getting a bit tired of repeating that the branching nature of the wavefunction - which gives rise ultimately to the many worlds - is a prediction of the theory. It can't be avoided without ad-hoc modification of unitary quantum mechanics.

Try this book:

https://www.amazon.co.uk/Emergent-Multiverse-Quantum-According-Interpretation/dp/0198707541

In what sense is this particular prediction "testable"? What specific experiential consequences can we deductively explicate from it? How would we then go about inductively evaluating whether there really are parallel "worlds"? — aletheist

That particular prediction is tested in every quantum interference experiment, and every experiment involving "non-locality". Quantum computing is also a test, as are certain proposed experiments involving reversible quantum computers.

A particularly striking and simple test is the Elitzur-Vaidman Bomb-Tester, in which you get to blow up a laboratory and perhaps kill yourself in a parallel world.

https://arxiv.org/abs/hep-th/9305002

Many Worlds is the only interpretation of QM that exists. The other theories are either not testable or proved wrong:

https://arxiv.org/abs/1508.02048

The only known theory that can reproduce the results of QM, at least up to quantum field theory, is Many Worlds.