Even is no-collapse intepretations, there is a process of decoherence into "coherent histories" (analogous to the "worlds" of the many world interpretation) that takes place. — Pierre-Normand

If you are going to quote, then the name is "Consistent Histories" or "Decoherent Histories". The first is explicitly epistemic, the second equivocates. The formalisms are however used in Unitary QM.

Coherent histories are correlated to (or "relative to") the macroscopic states of measurement apparatuses, or of the embodied human observers themselves who actively single our aspects of the world to observe, and who don't conceive of themselves as sorts of queer superposed Schrödinger cats). This is what "relative state" refers to in Everett's "relative-state formulation of QM". — Pierre-Normand

It might be worth pointing out that "coherence" is precisely what decoherence destroys. Anyway, I think you have Decoherent histories a bit wrong. They are for closed systems, and don't tell you which one occurred, rather give, under certain consistency conditions, a probability space for the course-grained histories. Of course the major difference between Everett and Decoherent Histories is that Everett regards the histories as real.

As for relative states, I think you've got that the wrong way round. It is the observer who is put into a state relative to each of the outcomes of a measurement. One counterpart is put into the state of having measured up etc.

I am not complaining about those, because I have not the least idea what they mean, nor do I particularly care to find out. After all, this is a philosophy forum, it is not actually Physics Forum. — Wayfarer

Then why do you care about Everettian quantum mechanics?

But in any case, the other wikipedia article, on multiverses, Level III, casts no light whatever. It still maintains there are indeed dopelgangers and multiple worlds. And Tegmark's books on the multiverse are routinely criticized by reviewers for verging on science fantasy. — Wayfarer

Tegmark did not invent the Level I multiverse, he just gave it a catchy name. If our consensus model of cosmology is true - i.e. Lamda-CDM, then there are an infinite number of exact copies of you at mean separation of ~10^10^115 metres.

Tegmark did not invent the Level II multiverse, he just gave it a catchy name. According to the consensus theory of the creation of our universe, inflation is an eternal process giving rise to an infinite number of universes - i.e. a multiverse.

Tegmark did not invent the Level III multiverse, he just gave it a catchy name. This is the quantum multiverse, the only multiverse for which we have any evidence. It adds no complexity to Levels I and II.

The "multiverse interpretation" of QM was an idea that came to light from several researchers at about the same time. Most notably Susskind and Bousso explored the idea and published a paper on it. These are serious big names in physics, as big as you get! The idea has since expanded into the slogan ER = EPR. A very big idea, informing a great deal of research. Quantum entanglement and wormholes could be the same thing!

And Tegmark's books on the multiverse are routinely criticized by reviewers for verging on science fantasy. — Wayfarer

Tegmark made a list. Don't be too harsh!

Tell me, then, why was 'Everettian QM' referred to as 'the many worlds' intepretation? The Wikipedia entry on the subject (and it seems adequately footnoted and referenced) states: — Wayfarer

Wikipedia, the font of all that is true. Well, try this Wikipedia:

https://en.wikipedia.org/wiki/Multiverse

Pay particular attention to "Level III" multiverse.

No one complains that our infinite universe subject to the Bekenstein Bound implies a multiverse of identical and near-identical copies of ourselves. No one complains about inflationary theory being impossible because it implies a multiverse.

No one complains when Susskind and Bouso and others identify Level III and Level I as the same thing. Yet, apoplexy ensues when the only multiverse we have evidence for is mentioned. Bizarre!

No, but then there's the problem of there being many worlds. The remedy is worse than the disease in my opinion. — Wayfarer

There isn't. Everettian QM adds zero worlds to those already proposed by cosmological theories. Denying Everett does not reduce the number of worlds.

This picture of complete determinacy of the future (given some fully determinate specification of energies and momenta in some space-like surface), of course, rubs against the indeterminacy inherent to QM — Pierre-Normand

If you resist the temptation to invoke "collapse", QM is a fully deterministic theory. Copenhagen is not a theory of reality, so has nothing to say about whether reality is really deterministic or not, De Broglie-Bohm is fully deterministic as are the various Everettian interpretations. The indeterminacy is purely epistemic, and not a feature of reality.

That said, according to realist no-collapse QM, we have determinism, but space-time is false, or rather an approximation.

Only through endorsing a time-independent formalism can you attempt to reconcile QM with the block-universe view, as you are wont to do. But this is to gloss over the measurement problem of QM and the fact that the measurement operators carry over the time-dependence of actual measurements (e.g. though specifying the time-evolving basis of the projection of the time-invariant state vector.) — Pierre-Normand

There is no measurement problem in realist no-collapse QM.

Science will make arguments mathematical or otherwise but the truth is only established if the external world or other evidence supports the argument. — Andrew4Handel

Truth cannot be established by the method of science. Errors can be detected and corrected with imagination. The purpose of argument is not to support a theory but to criticize it.

Take for example our two most fundamental theories: General Relativity, and Quantum Mechanics (in the guise of the Standard Model). Despite all efforts, no evidence has been found that contradicts either one. They have both met with stunning success, predicting novel phenomena and allowing known phenomena to be predicted with extreme accuracy. However, there is an "argument" that each renders the other problematic. That "argument" is clearly a mutual criticism.

We're not brains in a vat, because if we were, then not only would our lived world be a simulation, the words 'vat' and 'brain' would not refer to real brains and vats either. Likewise, we don't live in a simulation. — jkop

Not so! The Boltzmann brain, or rather a Boltzmann person, would simply have false memories, and the words "vat" and "brain" would refer to the real things.

The issue is that for many cosmologies, we are vastly more likely to be BBs than real people. There is actually a large physics literature on this problem, and a surprising level of disagreement. It's not a problem that can be just swept under the carpet. Some physicists think it is a big enough problem that our current consensus cosmological model (Lambda-CDM) must be wrong!

Sean Carroll's block universe, as he conceives it, within which time just is an objective parameter, doesn't contain any planet because this conception lack any criterion according to which some set of "particles" does or does no make up a "planet" in any specific space-like slice of his "objective" (so called) universe. — Pierre-Normand

Except of course, it is the very theory that reveals the block-universe to us - i.e. that the B-Theory of time is true - that explains the formation of planets and correctly predicts their orbits.

And time is a dimension, not a parameter, and it is relative, not objective.

Since no proposition can be stated without evidence — TheMadFool

That is simply false.

I agree. And how do we talk? Through propositions. — TheMadFool

Criticism of propositions. Most scientific theories die that way. e.g. no observations have ever been made which contradicts either the Standard Model, or General relativity, despite the LHC and LIGO. Yet, we know there is a problem!

However, I find all instances of deductive logic to suffer from the same problem(?). Everyone knows the Munchausen trilemma. Since no proposition can be stated without evidence we're left with three options: 1)Infinite regress OR 2) A starting point arbitrarily chosen OR 3) Circular reasoning. If we don't choose one of the above, deductive logic is impossible. In this particular instance (that of induction) we've chosen option 3 (circular reasoning). — TheMadFool

Another problem with the principle of induction - the future shall resemble the past - is that it's false in general. The Sun may rise every day, but one day it really won't, it will engulf and incinerate the earth.

Also, if you rely in induction you will never discover the reason the sun shines, no matter how many times you look at it!

However, if you make a guess as to why the sun rises, you may, if it is a good guess, be able to deduce some testable consequences of that guess e.g. seasons, Milankovitch cycles etc. This is known as the hypothetico-deductive method, or more succinctly, the scientific method. And it works!

Still this dualistic crackpottery. — apokrisis

Dualist crackpottery, you say?

Nope. It is the semiotic interaction between the realms of sign and materiality that allow that. — apokrisis

Semiotic interaction between the realms, you say?

Still this dualistic crackpottery.

A computational simulation is of course not the real thing. It is a simulation of the real thing's formal organisation abstracted from its material being. — apokrisis

That's what allows thought, and life.

Our theories tells us about how the world might be in itself. — John

Well, that's a small step in the right direction at least.

Any understanding of how the world could be in itself in accordance with our theories can only ever be given in terms of how the world appears to us, and so would be, utterly speculative. — John

Of course theories are speculative - to be more precise conjectural. But for that precise reason, they may have literally nothing to do with anything that has ever appeared to us. Many theories were conjectured to solve theoretical problems; Special Relativity solve the problem of the incompatibility of electromagnetism and Newtonian Mechanics. General Relativity achieved the unification of Newtonian Gravity and Special Relativity........

But what are these conjectures about? They are about how Reality really is. Are they wrong? Of course, but that is a bit harsh. It is more precise to describe our best theories as the prevailing misconceptions, that will be replaced in time, by better theories.

It would be a catastrophic mistake to ignore the fact that our deepest theories have made utterly shocking predictions about novel phenomena that are true. All future theories must respect these discoveries. Entanglement, quantum computing, electronics, teleportation .... are not going to go away!

We know from mathematics that there is a limit to what can be proved, but no such limit to conjecture, and no such limit to the scientific method exists.

The salient point is that the laws are models that tell us stories about the world only as it appears to us. They do not tell us anything about the world as it is in itself. — John

Then explain how our theories can tell us stories about things we will have to wait 50 to 100 years to observe?

If you look at any scientific theory, it explains what we see in terms of what we cannot see. Our theories tell us stories of how the world really is and, from them we deduce what we will see, even if we it takes 100yrs to develop the technology.

What does this mean? Does this only mean that if I go in a straight like I will return ultimately to the point I started from? Yes it does. Therefore the Earth not being flat is a model for the underlying reality. The underlying reality is what you experience directly. — Agustino

I had no idea you really did that. Quite a trip eh?

Big-bang, CMB, etc. are concepts, not realities. They are pieces which together form a coherent whole, which is our scientific model of reality. Nothing more. — Agustino

You are in a state of irrational denial.

The Earth really does orbit the Sun, and the Earth really is not flat and it's not turtles all the way down, really.

And entanglement was really predicted in 1935 and really observed in 1982.

And gravitational waves were really predicted in 1916 and really observed in 2016.

And do you think solid state electronics was an accident, or did solid state physicists really predict that if they could really build a p-n junction, they could make diodes, amplifiers ... ? Solid state theory could not even be conceived of without quantum mechanics!

And the CMB really is light from the big-bang, and certain as-yet-unobserved patterns in the polarization of the CMB radiation will be evidence of eternal inflation.

I forgot, gravitational waves were revealed by theory 100 years before they could be measured. It only took ~50years to observe the other features of reality like entanglement and the cosmic microwave background.

And don't forget cosmology takes us to times before the big-bang, whose signal is revealed to be within the CMB.

No, theory clearly reveals nothing.

I've never said this. I've never said through the laws we know nature as it appears to us, nor have I ever implied such a noumenon/phenomenon distinction. In fact I said quite the contrary - the laws themselves do not reveal the phenomenon to us. — Agustino

Apart from entanglement, the geometry of the universe, the big-bang, cosmic microwave background ...

Sure, the laws reveal nothing.

This doesn't show that humans can't perform those operation; only that they may choose not to. Humans don't really instantiate universal Turing machines because they are finite mortal beings, but then so are human brains. But I don't quite know what your argument is anymore. You seemed to be arguing that the mind was the software of the brain. Your ascribing vastly superior computational powers to brains than you do to people supports this contention how? — Pierre-Normand

The distinction I am drawing is between the physics and the abstraction.

At the risk of repeating myself, it has been proved that all real universal computers are equivalent. The set of motions of one can be exactly replicated on the other. It has further been proved that any finite physical system can be simulated to arbitrary accuracy, with finite means, on a universal computer. The brain can thus be simulated on a universal computer, whether it is itself universal or not. Whatever a brain can do, a computer can do. There is nothing beyond universality.

The idea that the brain is not computationally universal seems somewhat churlish. Given that we know that the capabilities of the Mind far exceed the capabilities of any currently known programs which run on computationally universal hardware, to claim the brain is non-universal, does not give credit where credit is due!

The brain is computationally universal, just like my laptop.

I would readily grant that humans are smart enough to execute whatever algorithm is given to them. Indeed they can do it as mindlessly as any old CPU, or as Searle would do it in his Chinese Room. — Pierre-Normand

The brain is computationally universal, but the mind certainly is not. There are many operations a mind will not perform, for reasons as diverse as morality and boredom. Humans can't execute algorithms mindlessly, and they don't execute algorithms like those we program into machines.

I would also readily grant that mental abilities can be multiply realized in a variety of biological or mechanical media (be they better conceived as specifically implementing computational operations, or not) but this shows no more than that possession of mental skills is a formal feature of rational beings. — Pierre-Normand

I certainly wouldn't grant that. The only known object in the universe which instantiates mental abilities - i.e. creates knowledge, possesses qualia and general intelligence, is the human brain.

The mind/software analogy also glosses over other significant differences between rational beings and computers. — Pierre-Normand

It would have to gloss over the significant difference between rational beings and abstract beings instantiated on computationally equivalent hardware. Or more precisely, the significant difference between minds instantiated on human brains and minds instantiated on computers.

Computers don't give a damn. — Pierre-Normand

Brains don't give a damn either.

but an enormous number of simulations won't increase the likelihood of other things being simulations. Even in a universe replete with simulations each and every simulation must be composed of parts which are constituitive for the possibility, but insufficient separately. The number of parts is always greater than the number of simulations. — jkop

According to known physics, our descendants will be able to simultaneously simulate many trillions (surely an underestimate) of universes simultaneously on a single device. They will of course be using quantum computers.

How would an exercise in counting infinities be a reason to believe that reality is a simulation? — jkop

It renders the probability of us not being simulated zero, to any degree of accuracy.

Of course this is all predicated on the idea that our descendants will simulate us. They won't!

Not true. Software is part of a computer - that's the actual definition. Humans are not computers, and thoughts are not software. At best it's a model or an analogy. But, there's been a thread running on Online Philosophy Club, since 2007, about this very question, and it just keeps running. (Maybe it has a halting problem — Wayfarer

Denial is always an option I suppose, but history will not be on your side.

Of course, if you managed to formulate an argument that the brain is not computationally universal, and that it could not be programmed (e.g. by training), and that therefore the mind could not be an abstraction instantiated on a brain, then you might have a point.

Might be easier to show that the entire theory of computation is wrong though. Go for the jugular and attack computational universality. Best of luck!

This has some relationship with the famous Libet experiments, doesn't it? They showed that the body moves before the subject is aware that they want to move it. — Wayfarer

And "everyone" touts Libets 1980s experiments as evidence of the absence of free will, and ignores his 1990s experiments, where he demonstrated a mechanism for it.

The problem with 'mind as software' is that it surely is an analogy. It isn't literally the case, because software is code that is executed on electro-mechanical systems, in response to algorithms input by programmers. The mind may be 'like' software, but it is not actually software, as has been argued by numerous critics of artificial intelligence — Wayfarer

That all computationally universal hardware is equivalent is not an analogy. The human brain has to be computationally universal. That's not an analogy either.

The mind isn't LIKE software, it IS software. The human mind is constantly changing - creating knowledge - by programming itself. It is also a type of software we don't understand yet.

Why do you think there would have to be a second universe?

Would you please elaborate a bit more on why this argument isn't convincing? I agree with you that it's not convincing, but I'd like to here your reasoning. — jdh

The probability that you were born a human and not any other animal is the same as the probability that you were born with a human mind and not an animal mind, or a human liver and not any other animals liver. I don't think you can pick some aspect of a human and argue that because it is unlikely, animals don't possess it.

Animals can't talk, but I don't see how you can infer that from the fact that you can, and that your species is relatively rare.

Animals can't create knowledge, including knowledge of themselves. This is a blessing.

The tendency to make this conflation is a core target in Bennett and Hacker, The Philosophical Foundations of Neuroscience. But if you don't like having your preconceptions challenged, suits you. — Pierre-Normand

I don't mind having my preconceptions challenged, if you don't mind elaborating?

Wall Street and the academic elites isn't the natural home of Democratic liberal, progressivism. — Bitter Crank

What!

Have you heard of George Soros? The top donors to the Democrats at the election were:

University of California $1,945,782
Alphabet Inc $1,576,067
EMILY's List $1,362,696
JPMorgan Chase & Co $1,172,825
Citigroup Inc $1,052,604
Goldman Sachs $1,050,821
Microsoft Corp $1,043,660
DLA Piper $1,027,670
Morgan Stanley $1,014,906
Time Warner $974,069
Harvard University $951,049
US Government $850,539
Skadden, Arps et al $842,393
Stanford University $775,885
US Dept of State $769,921
Columbia University $749,070
New York University $714,374
Kirkland & Ellis $705,744
Apple Inc $700,682 $700,682
Comcast Corp $690,510 $680,510

Hedge Funds donated $123,000,000 to Clinton.
Hedge Funds donated $19,000 to Trump.

I'm sorry, but Wall St and the academic elites ARE the Democratic Liberal establishment!

http://observer.com/2016/02/why-wall-street-gives-hillary-clinton-millions-of-dollars/

The entire universe cannot be a simulation, because there must be something left, say a second universe which is real, and of which our universe could then be a simulation. So the speculation makes no sense. — jkop

I think the idea is that there is one universe and it is the inhabitants of the future that are simulating the past, and they are doing it an enormous number of times. Hence we are far more likely to be simulated than real.

But, if you add in the infinite number of other universes, and the infinite number of causally disconnected regions in our own infinite universe, then the fact that we are simulations is inevitable.

Do you say that the mind is analogous to software? If so, that would paint a rather inert picture of the mind. In this context I would rather say that software are the instructions for the brain. One problem is, how do we write those? — Querius

No, I mean the mind IS software. According to known physics, it can't be anything else. Consciousness is a software feature, and the software programs itself.

If the mind is the brain, and is produced by neuronal behavior, then the whole path from intentionality to neural change is a purely physical affair. There is no gap between the ‘mental’ and the physical, so no need for a mechanism to close any gap. I have no questions concerning this scenario, other than how matter can be intentional. — Querius

Is that not analogous to the claim that the chess program is the computer?

If instead the ‘emergent’ mind is independent from neuronal behavior, if it can reach down, by free will of its own, and cause neural change, I would like to know how this works.
If, as a third possibility, the mind is 'semi-independent' or something, please provide a clear picture. — Querius

Software needs hardware to run on, and if you disturb the hardware with anaesthetics or death, then the effect on the running of the software is going to be pretty drastic. But there is another type of independence: all computationally universal hardware is equivalent.

In my book it makes no sense to term neuronal systems 'sub-conscious'. Anyway, how does the independent mind control those 'sub-conscious' neuronal control systems? — Querius

You can remove an entire cerebellum, and the only difference the person notices is reduced motor control.

Explain what happens when one chooses to raise one’s arm. Explain the mechanism from intention to neural change. And explain how the “I” knows which neural parts to change and which not. — Querius

It would go something like this:

The abstract mind, instantiated on the computationally universal brain, decides to move an arm. It does not know the mechanism of how this is performed, because it does not need to. The mechanism involves layers of sub-conscious neuronal control systems, which eventually result in the appropriate nerve signals to the appropriate muscles.

An abstract computer program, instantiated on a computationally universal computer, decides to move its robot arm ...

Because we don't believe in magic, there cannot be any other explanation, though some of the details are a bit sketchy to say the least.

My question is is math deserving of this respect and trust? Could it not be flawed? What does a mathemstical analysis of a given subject deprive us of? Are there some areas of study where math is harmful instead of beneficial? — TheMadFool

In that case, the mathematics is perfect - its use however is not.

As systems become more complicated, in order to make them tractable, it is inevitable that certain simplifying assumptions are made. You might be able to write down an exact set of equations, but can you solve them? More often, the equations themselves are approximations.

No

Most mathematical truths cannot be proved. The overwhelming majority of mathematical relations cannot be known. The overwhelming majority of numbers can't be represented. Only a tiny fraction of mathematical functions can be computed.

And, the above restrictions are imposed by physics!

I will have an infinite number of relationships that can account for the underlying structure of the two variables which have generated these facts. — Agustino

And despite this, we aren't exactly overwhelmed by competing scientific theories are we? It is trivial to write down endless ad-hoc modifications to our best theories, which will be empirically indistinguishable from the original. Why does no one do that?

Well, there are several reasons no one ad-hoc modifies theories, the most significant being that scientific theories are not models and they are not equations.

I'll go out on a limb and guess that any measurements that are fine enough to test the HUP will not be about macro impacts. — andrewk

The stability of atoms has rather significant "macro-impacts". And you can demonstrate HUP at home with a laser pointer and some aluminium foil.

The probability that I won that lottery is 1, as it is for any lottery winner. — andrewk

Perhaps this is a good opportunity to remind ourselves of the difference between marginal and conditional probabilities?

I think you got that backwards. Laplace's demon? Not so, whichever way you want to read it. In any case, how has that anything to do with whether determination extends beyond the epistemic realm? — John

The laws of physics are completely deterministic.

Your reply has nothing at all to do with the question.The question has nothing to do with anything anyone might find panic-worthy, either, as far as I can see. Perhaps try saying something more relevant next time; that's the best way, if you genuinely want to engage in an actual conversation. — John

The laws of physics are fully deterministic. Given the state at any time, the future can be retrodicted and the past can be predicted.