The paradox seems to rest on magical thinking about consciousness, and if one simply accepts that a conscious observer can be in a superposition like any other piece of matter, the paradox is resolved.
And, from the article:
For Wigner, this was an absurd conclusion. Instead, he believed that once the consciousness of an observer becomes involved, the entanglement would “collapse” to make the friend’s observation definite.
But what if Wigner was wrong?
Well, obviously Wigner is wrong, sorry for being flippant.
In this paper (preprint here: https://arxiv.org/pdf/1907.05607.pdf), the magical thinking about consciousness seems to be transmuted into "“Absoluteness of Observed Events” (i.e. that every observed event exists absolutely, not relatively)". The authors (it appears to me) mean by this that if an observer performs an experiment, while this observer is himself in a superposition, we have to regard the outcome of the experiment as absolute (i.e. not in a superposition) because it was made by a (conscious) observer.
In my opinion, both "Absoluteness of Observed Events", and the equivalent from the layman's article, "When someone observes an event happening, it really happened", is a disingenuous and confusing way of talking about observers who are in a superposition. We have crossed over from "quantum mechanics is weird" to "these superficially intuitive but clearly false assumptions about quantum mechanics are weird".
We're veering away from physics here, but isn't consciousness actually quite "magical". It's beyond remarkable to me that stimulating nervous tissue, composed of quite mundane things like protons and electrons, yields a subjective experience. I know many people reject the hard problem of consciousness, but to those who don't, the implications of thought experiments like Wigner's friend, like superpositions or entanglement of subjective experiences, are truly paradoxical. You are calling certain viewpoints obviously wrong or false because you adhere to certain philosophical viewpoints. There's nothing wrong with that, and they're all justifiable, but none of them are complete consensus among philosophers.
Coming back to physics, there's an assumption you and other commenters are silently making, which is that quantum mechanics is even applicable to macroscopic objects like humans. The largest objects which have been shown to act wave-like are a few thousand atoms large. While it's indisputable that at the lowest level the universe is fundamentally quantum mechanical, it's a little brazen to extrapolate that over more than 20 orders of magnitude. As a physicist myself, I'll believe it when I see it, and I'm looking forward to getting results from proposed experiments like FELIX and its successors.
>Coming back to physics, there's an assumption you and other commenters are silently making, which is that quantum mechanics is even applicable to macroscopic objects like humans.
It follows from schrodinger equation, it provides no exception for macroscopic objects. You can say quantum effects indeed happen at the lowest level, and macroscopic behavior follows what happens at the lowest level. It's a question of reducibility.
> The largest objects which have been shown to act wave-like are a few thousand atoms large.
Large objects have wave-like behavior, e.g. you can't determine their size with femtometer resolution, they don't suffer from ultraviolet catastrophe and have macroscopic quantum effects like superconductivity.
Pretty sure I’m dunnig-krugering this, but is consciousness really that magical?
Nervous system evolved from ability to respond to external stimuli to centralized control of various processes to evaluation of risks/benefits of actions and finally to predictive modeling of external processes. Rudimentary concept of “self” and understanding of surrounding environment exists in various animals, so why is it strange that an animal with most complex brain has the most sophisticated concept of “self” and it’s placement in the ultimate surrounding environment - the universe?
Of course, apart from how the actual implementation works I don't think many people have a problem with that. And if it was just that, Wigner's friend wouldn't be nearly as interesting, it would suffice to say that if quantum mechanical effects really keep working all the way up to the macroscopic level (which again is anything but obvious), that his friend's body and brain would simply be in a superposition of both states.
But this understand of the surroundings and capability to react to stimuli comes with a subjective experience, which is what is actually meant with "consciousness". This is the hard problem of consciousness[0].
One of brain’s responsibilities is to model the environment, which means modeling all it’s parts. Since each brain is unique - those models are different and “personal”. Physical stimuli evoke some of those models and that’s what we call “blue color” or whatever else we’re experiencing.
I don’t think I understand the problem enough to understand why it’s a problem.
By inner experience, we mean that there's a subject which gets to have perception of such models.
There's no need for such subject to exist.
For example, most people assume that, so far, computers do not have any inner experience.
A computer could, conceivably, execute the same functions as our brain, yet have no inner experience of anything. Numbers get in, numbers get out, without any inner experience being needed.
Sure, just like a thermostat doesn’t experience the feeling of temperature, there is no need for human to feel it, so I understand that we need to explain why is it that we still feel the feeling rather than just observe the signal and react.
So why is it wrong to explain this by the necessary recursiveness of predictive modeling that includes modeling “self”? We observe the temperature but we also observe ourselves observing the temperature. First is the signal, second is the introspection of the model evoked by that signal - the feeling.
Yes but where does this observer come from in the first place? Some theories do presume the thermostat experiences the temperature, just in a less-sophisticated form of consciousness. If an "observer" is nothing more than neurons firing in response to stimuli, then it's not fundamentally different from the thermostat.
It is understandable that having an model of an observer can be useful to a brain.
But how/why does that opens a window to an actual observer, and not just a model, is the question.
And we only know that - an actual observer exists - through first hand experience. It is our most immediate and certain knowledge (Cogito, ergo sum), everything else can be questioned. Yet, there's nothing in physics or computer science that gives a hint to this being the case.
Ok, so first hand experience tells you an observer exists.
Are you sure that observer has your personality, mind and memories? Are you sure that observer is involved in any way with the world, other than observing it?
Or are those other things just part of the machinery, and quite illusory. For example our perception of time, coherent thought and personality aren't all that consistent, as we know from various experiments and observations.
Here is the crux of my point:
If there's an actual observer, let's call it "primal consciousness", but they are observing the world through the lens of a mind, which is a complex, self-referential, reactive process running on a brain and body, we don't need to say that any particular physical process "creates" consciousness. We can settle with physical processes create something complex and interesting, which runs models of itself and the world, which "primal consciousness" observes. The "mind machine" running on the physics does not contain the observer, it's observed by the observer.
That doesn't "solve" the hard problem, but it's a model with different properties and consequences than some of the other models.
> So why is it wrong to explain this by the necessary recursiveness of predictive modeling that includes modeling “self”?
It's not "wrong", it's just not parsimonious. A system can model itself without being conscious, any time you have state in a program you are doing this.
I like this idea. From my limited reading and understanding, the nervous system/brain and body seems to function as a huge number of feedback loops where the nerves are predicting a response in the body to a nerve firing event, doing the event, and then comparing what happened to the prediction. Moving your hand is a huge number feedback loops. Seems like a similar thing probably happens for abstract things like words. Building up all these sub models to a model of the self seems like a natural progression and could be very evolutionary beneficial, although with drawbacks also (paralyzing self doubt, depression, neuroticism, etc)
It's only wrong because it's not really an explanation. At best, it's a weak one.
Saying that an active model of self "is" what we experience as the consciousness we experience doesn't tell us why we have that experience.
We can just as easily imagine a complex machine with an active self-model that isn't conscious, as one that is.[1] So an active self-model doesn't tell us about consciousness. This shows them to be different concepts, not different names for the same concept. Which means neither "is" the other, and "is" is not an explanation.
[1] (To be a little more picky, we can't imagine that if we insist they are the same thing, but that leads to circular reasoning here. Our questioner can imagine both, and for an explanation to explain it needs to address the question, not wave it away by offering something circular.)
It all sort of falls apart when we only talk about whether an object other than ourselves is conscious or not.
As far as we know[2], we can't distinguish consciousness of other objects by observation. A hypothetical non-conscious machine might tell us it is conscious; we will never know if it's GPT-3000 talking or if it's another being like ourselves. So eventually we'll probably decide that it's moot, and treat it as conscious if it behaves convincingly and consistently like it is.
[2] That could change, it's not ruled out.
But that doesn't deal with the "hard problem" of consciousness, which is ourselves.
For ourselves, we are in no doubt about the direct experience of our own consciousness. We might convince ourselves that it's just an active self-model, processing, because of how we think of data processing machines these days. But we shouldn't, for one because that's a weak explanation that doesn't explain, and for two because there are other active self-models in the universe, and also in the much larger abstract realm of "unexecuted" self-models that could exist (pick an RNG seed and set of rules of your choice). We don't experience those, so the one(s) we do experience are notably distinct, for no obvious reason.
lots of interesting replies, thanks. i'll aggregate my thoughts into single comment to keep this discussion more focused.
it seems to me the only rebuttal is "sure, self-models can exist but it's concievable that they can exist without an observer, so why is there an observer?" and to me it sounds similar to "sure, an eye can exist without abiogenesis, so why do we only find it in organisms that resulted from abiogenesis?"
an eye is just a collection of amino-acids, nothing prevents an eye from spontaneously assembling in a primordial soup and we recognize that's absolutely impossible. however i would posit that due to configuration of physical interactions in our universe, it's virtually guaranteed for an eye to develop in any life-form that is exposed to star's radiation in earth-like conditions.
similarly, just that we can think of p-zombie doesn't mean it's a simpler system to natually occure. we don't have understanding of building blocks of consciousness like we do with chemistry and biology but the answer to the why question seems to be quite simple: we observe ourselves because we evolved to. and we can find more and more primitive examples of self-observation in more and more primitive animals, so it's not some binary phenomena.
Commenting a bit late since I had this tab open for a while, but I find this discussion interesting. Even more magical than consciousness itself, are people denying that there even is a hard problem of consciousness to begin with (if you assume the standard model) ;) You started with asking if consciousness is really that magical and finished with basically admitting that we don't have an answer for how it works yet.
The hard problem of consciousness is not just about the why, it's also about the how. That's exactly the magical part: how subjective, non-physical experiences (supposedly) come from physical interactions. Brushing it off as "evolution" is not sufficient to explain the how.
You’re right, I have no idea how and that’s hard to figure out. Probably I misunderstood the statement of the problem by only focusing on the why part.
Coming from engineering background, I would say we need to be looking for self perpatuating loops of neuronal activity (“strange loops” may be quite appropriate concept), but how would we go about looking for them - I have no idea because I’m not up to date on modern brain scanning tech.
Why hard problem is even here? Consciousness isn't magic, because chinese room in conscious, and it has nothing to do with quantum mechanics, because of paradoxes.
That still doesn't explain why I'm conscious, something that I have direct, first-hand experience of.
> Consciousness isn't magic, because chinese room in conscious
That doesn't explain anything.
Does that explain to the person experiencing consciousness why they are? No it doesn't.
It just says "something else is conscious so you are too". Which is not an explanation, it's circular.
Is it relevant if the Chinese room is conscious as well? Not really.
I am curious, though. Do you consider a system (such as a Chinese room) to be conscious if it's only implicit, by writing down the rules it should run, without actually performing any of the rules? What if it's so implicit that we don't even write down anything, we just refer to it by name, and assume we would create the rules if we needed to as the first steps in execution? Is it conscious when nothing happens at all, but it could happen? If yes, does that mean every possible thing that could occur is conscious even if it doesn't occur? Every physical possibility is conscious? The whole world of abstract mathematics is conscious? If the answer to any of those is no, where do you draw the line between conscious things (Chinese room) and not-conscious things?
Hard problem suggests that consciousness is magical, in which case it could mess with physics. But if consciousness isn't magic, then hard problem is a problem of understanding, not a problem of physics.
>without actually performing any of the rules?
Chinese room works like human mind, so it should run to be conscious.
You might consider reading the original paper. Because the experiment doesn't rely on conscious observers at all. (Unless you think photons are conscious, which I'm assuming you don't.)
Well, that's the point. The experiment shows that one of three assumptions has to be false. But one of these (AOE) being false is not surprising or concerning at all, when dealing with non-conscious observers (such as photons, indeed). With conscious observers it would be concerning to some (not to me, but to Wigner and presumably the authors), because of the supposition that there's something special about conscious observers (i.e., magical thinking, IMHO). So what has this paper really shown? Absoluteness of Observed Events is false when the observers are photons, which (my layman's assumption) should surprise exactly nobody. And then they propose to repeat the experiment with an AI in a quantum computer as the observer. Lol.
> Absoluteness of Observed Events is false when the observers are photons, which (my layman's assumption) should surprise exactly nobody
I'm with you but is this experimental result not new though? It seems like they're on our side and confirming what should be a non-surprising result, which is good work.
Definitely not new, the double-slit experiment in 1801 first hinted that this might be the case, and then Heisenberg calculated exactly how 'not absolute' observed events are based on the wavelength (aka momentum) of the photon you're using (in 1927).
> if one simply accepts that a conscious observer can be in a superposition like any other piece of matter, the paradox is resolved.
It’s not so simple. Suppose you’re in a box and observe a quantum experiment, and then I open the box and observe you. Then before I open the box you’re in a superposed state |x> + |y>, corresponding to the two possible outcomes x and y. Fine, no problem so far. But what is your own subjective experience? You, subjectively, inside the box, will only ever observe yourself to be in |x> or |y>, never |x> + |y>. Even if from the outside your brain can be said to be in a superposed state, your experience of the world is not superposed.
The |y> superposition of you has one experience, and the |x> superposition of you has a different experience. The |y> version has no information about the |x> experience, and vice versa, because those two states are orthogonal in Hilbert space. This is essentially the prediction that results in the Everett many worlds interpretation.
If you somehow had an experience of "both outcomes simultaneously", that would violate the quantum mechanical prediction that there is no mutual information between the two superpositions. There are two brain states, an x state and a y state, and they know nothing about each other.
To each brain state (with the limited information available to it) it would appear that something "definite" had happened, even though in the global picture, a superposition still exists.
Either you believe in collapse, so there are two of you, who each observed different things, and one of those will at some point cease to exist, or you embrace the Everett interpretation, and so there are two of you who each observe different things and go on to live their separate lives.
Both paths you laid out are built upon the idea that superposition happens. Is there any serious consideration these days that superposition itself is dead end?
When people compare QM theories they often do so on basis of the original experiments that were used to develop them. But as a discipline physics has moved well past those. Superposition has been proven and tested to exist, and we have long since moved past that phase and started building things, like quantum computers, on top of it. At this point, pretty much the only way superposition doesn't exist is that every time a physicist does something that superposition needs to work, a devil figures out what kind of result is needed to fake it and does that.
Trying to challenge superposition would kind of get same kind of results from physicists as trying to challenge the existence of electrons would get from people who build circuits. Like, if you have some interesting new theory, I am intrigued, but do understand that to get people to follow it you will need to explain how it replicates the results of what superposition would do in so many different cases that you won't be able to enumerate them in a week.
I didn't know that. If you have more information I'd love to learn about it. I was under the impression that collapse wiped out all information about any other states.
Many-worlds interpretation takes care of this. Anyway, how do you know your experience of the world cannot be superposed? Have you ever been in superposition? We make up stories to maintain consistent histories all the time.
> how do you know your experience of the world cannot be superposed?
For your experience of the world to be superposed it would mean that you carry out a quantum experiment with two mutually exclusive outcomes |x> and |y> and you actually experience the superposed result |x>+|y>. This would be like opening the box in the Schroedinger's cat experiment and actually observing the cat to be |alive>+|dead>, instead of either alive or dead. Maybe it's possible, but such an experience has never been reported.
It's "possible", but not really possible. The larger the object is, the harder it is to maintain superposition. Even the slightest nudge will tend to push it all into one state or other. Seeing the superposition directly would be like standing twenty octillion strands of spaghetti on end.
So it's "possible" but would never happen in a trillion lifetimes of the universe. You can tell the difference between that and "impossible" by watching the quantum mechanics work for a few isolated particles, and observing what it means for them to fall out of superposition equilibrium. But in practical terms, it's equivalent to impossible.
Nonlocality basically means that the universe has a global RNG state. If you write some code that uses a global RNG and no other global variables, that code will still be "local" in the sense that functions cannot communicate information between each other using the RNG. But the outcomes of the functions might still be correlated in interesting ways (corresponding to entanglement).
No, non-locality simply means that effects happen at infinite speeds, not that they carry information.
For example, the Copenhagen interpretation of QM abandons both locality and realism - particles don't have definite states, and they also communicate at infinite speed (but in a way that can't carry information).
Basically when you measure the state of two particles that are entangled, you find that their state is correlated in some way. For example, they may be entangled in such a way that their spins are the same. So if you measure one to be spin up (when measured along any axis), the other will also be spin up (when measured along the same axis). This happens regardless of the separation distance between the two particles. By carefully adjusting the axes along which you do your measurements, you can prove that the spins that you get are not predetermined (this is Bell's Theorem) and yet the particles are not communicating at the speed of light with each other either (the correlation remains even if you move the particles far apart and then do the measurements at the same time). Note that the actual spin value itself is random, and once you do the measurements the entanglement is broken, so you can't use this to transfer information faster than light. Hence what the parent poster means by "communication without information": each particle individually appears to be completely random, and yet when you compare them you see both particles are random _in the same way_ (or in the opposite way, particles can be anti-correlated too).
Sorry but there is nothing obvious about any of it. It all boils down to the measurement problem and entanglement. While I don't like psi-epistemic interpretations either, it's not like there is anything clearly inconsistent with them, or like psi-ontic and psi-complete interpretations make more sense or are devoid of issues. They all have problems and make assumptions that are hard to swallow, and if you believe any of them and start ridiculing others you are pretty much picking sides with no good evidence. So while you might have already pledged your faith, other people with probably as much understanding of the issues or more haven't.
Translating the thought experiment to an actual physical experiment is something worth appreciating.
A possible lack of absoluteness of observed events has implications for what observations may or may not be reconcilable using existing scientific methods.
> "From the point of view of the friend, the measurement result was determined long before Wigner had asked about it, and the state of the physical system has already collapsed. When now exactly did the collapse occur? Was it when the friend had finished their measurement, or when the information of its result entered Wigner's consciousness?"
This to me, shows just how hand-wavy the whole superposition/quantum collapse stuff really is. I have to say I side with Einstein with his view that everything is already in one state or the other. We don't cause the system to choose a state when we measure it. We simply discover the state it was already in. It is one thing to assign a probability to which state we will find it in. It is quite another to create an entire theory around quantum measurement.
There is nothing mysterious about this paradox. The friend performs the measurement ans discovers the state of the particle/system. Wiger doesn't know about it, but that doesn't mean it's not in that state, he just isn't aware of it yet. The fact this is a paradox just seems like silly mind games.
> how hand-wavy the whole superposition/quantum collapse stuff really is
Superposition isn't particularly hand-wavy. It's the basis of various technologies, and of precise numerical models we use to build technologies.
Quantum collapse is hand-wavy, and that's because it is not well understood. It might not exist (in which case superposition of mind-states is a thing), or it might exist (in which case mind-states may be definite). Quantum mechanics that we can calculate doesn't give an answer either way, even though it gives lots of other answers very precisely and correctly.
> Wiger doesn't know about it, [...] just seems like silly mind games.
When only applied to a single measurement it does seem like silly mind games, you're not wrong.
The motivation for those thought experiments was to try to reason back from the consequences found from more complex behaviour observed with multiple measurements, back to a simple system with only one measurement.
But when you have many measurements with entanglement, of which there are numerous physical experiements and confirmations by now, the idea that there are just multiple, correlated probabilistic states ready to be observed that we're not yet aware of is not consistent with physically measured behaviours. Those measurements aren't hand-waving, they are hard data, even though my explanation here is hand-waving and doesn't go into it.
> I side with Einstein with his view that everything is already in one state or the other
Numerous experimental results now contradict this view, or require other strange things to be true about the world (for example superdeterminism was mentioned in the article).
Your position is more or less defensible, but you will have to accept some compromises to your description of the universe that most physicists find untenable.
These experiments were really the nail in the coffin for Einstein's position for most physicists. Having to admit non-local hidden variables is a pretty distasteful result.
QM is not hand wavy and gives precise results for many practical problems. Your theory is wrong as per one of the simplest quantum experiment - the single electron double slit problem.
The variation of the double split experiment that supposedly proves that observance "changes" the outcome, is only a thought experiment, and therefore can be flawed due to incorrect thinking. Obviously, the basic double slit experiment which shows the wave/particle duality of light is done in practice and therefore empirical.
I like most on here have followed your thinking at some point, but have had to ditch our intuition along with comman sense and a good part of our sanity when we found out we were lost down the rabbit hole after schrodinger's cat ate our breadcrumbs.
An observer changing the outcome is a very real repeatable experiment with non wavey results.
It's similar to the problem that has been highlighted here by OP, to quote the artical I posted
"Indeed, the results of both Truscott and Aspect’s experiments shows that a particle’s wave or particle nature is most likely undefined until a measurement is made. The other less likely option would be that of backward causation – that the particle somehow has information from the future – but this involves sending a message faster than light, which is forbidden by the rules of relativity. "
It's interesting the way some scientists have been biased into this kind of magical thinking, probably because the integrity of conscious observation is so central to their practice/worldview. Nobody is free from the pressure of cognitive dissonance.
The paradox seems to rest on magical thinking about consciousness, and if one simply accepts that a conscious observer can be in a superposition like any other piece of matter, the paradox is resolved.
And, from the article:
For Wigner, this was an absurd conclusion. Instead, he believed that once the consciousness of an observer becomes involved, the entanglement would “collapse” to make the friend’s observation definite.
But what if Wigner was wrong?
Well, obviously Wigner is wrong, sorry for being flippant.
In this paper (preprint here: https://arxiv.org/pdf/1907.05607.pdf), the magical thinking about consciousness seems to be transmuted into "“Absoluteness of Observed Events” (i.e. that every observed event exists absolutely, not relatively)". The authors (it appears to me) mean by this that if an observer performs an experiment, while this observer is himself in a superposition, we have to regard the outcome of the experiment as absolute (i.e. not in a superposition) because it was made by a (conscious) observer.
In my opinion, both "Absoluteness of Observed Events", and the equivalent from the layman's article, "When someone observes an event happening, it really happened", is a disingenuous and confusing way of talking about observers who are in a superposition. We have crossed over from "quantum mechanics is weird" to "these superficially intuitive but clearly false assumptions about quantum mechanics are weird".
(by the way, I read the article here: https://theconversation.com/a-new-quantum-paradox-throws-the... because that site doesn't think I'm a robot and then redirects me to the homepage after filling out the captcha)