El Hombre Invisible said:
Earlier you said that if two objective observers both observe the state of the cat then their states are 'entangled' in such a way that the probability of one observing one state and the other observing the other is negligible, if not zero.
That's not exactly what I stated. What I stated was that one observer who observed a phenomenon, and found an outcome A, will only observe another observer (that part of it) that will also have observed outcome A, and that this correlation comes about by the entanglement of the first and the second observer states. This can sound similar to what you say, but it isn't and the difference contains the whole difficulty !
If you accept that observer 1 got entangled with the system:
|O1A*> |A> + |O1B> |B>
(the physical body associated with observer 1 gets into two macroscopically distinct states, where one state has read "A" on the dial, adn the other state has read "B" on the dial, but he consciously observes only the one with a *), and now observer 2 also measures the system, so gets into:
|O1A*>|O2A>|A> + |O1B>|O2B>|B>
clearly, the "conscious" observer 1 only sees the body of observer 2 in his own term, so he sees it in the state "O2A". To observer 1 therefor, observer 2 also observed state A. And if he asks observer 2 to write down what he saw on the dial, he will only see what happens when this action is applied to his term, so to |O2A>, in which case he will see observer 2 write down "A".
Now, it might be, or it might not be, that observer 2 is a conscious observer. It might be, or it might not be, that observer 2's original consciousness got associated with O2B. It might be, or it might not be that a "new" O2 consciousness is "born" in O2A. All this doesn't matter to O1. What O1 simply observes is that he saw the system in state A, and his buddy, O2, for all he knows, also saw the system in state A. He cannot interact with O2's consciousness, but only with his body, which will - that's the premise - behave in exactly the same way whether it is "conscious" or not, and whether it contains now a "new" consciousness, or whether this consciousness is the continuity of the "old" O2 consciousness.
The question of whether a cat is conscious, then, and so in turn of what constitutes consciousness becomes important, for if it is conscious then the cat can then replace the other observer. If consciousness is the phenomenon that causes a seeming collapse, and states are entangled in such a way that one observer will be conscious of the same collapsed state as another, it seems important to differentiate between conscious and non-conscious observers.
No, it doesn't. If all conscious observers were somehow "in the same state" then we should conclude that consciousness CAN collapse the wavefunction ontologically. But we start from the hypothesis that consciousnesses cannot do anything to the physical world - they can only "experience", and the physical world runs on its own. (this was the hypothesis that a conscious being cannot change the state of the entire universe).
But I do NOT need to differentiate between conscious and non-conscious observers: they do not do anything to the physics, and they can end up in other branches than I do if they are conscious. I will never find out, because I can only measure physical things which are not influenced by such consciousnesses. They just "hop passively on the physics train", just as mine does, and I cannot find out whether they are on the same wagon or not.
Your definition of consciousness lacks this. It also lacks a description of consciousness that explains why it differs from the rest of the human body.
It is not a "part" of the human body, it is "associated with" it. There are several viewpoints one can take here, but all of them do not differ in anything which could be checked against any experiment so it doesn't matter.
For instance, you could assume that certain complex enough classical structures are "conscious" (brains, computers, whatever). Then, this would simply mean that from the moment that such a term appears in the wavefunction of the universe somewhere, a consciousness is associated with it (and when the term is not there anymore, the consciousness disappears - dies if you want to).
Now, when the wavefunction of that physical structure splits into two macroscopically distinct structures (for example, as the result of an interaction which could be called "a measurement" such as reading of the dial of a voltmeter), one simply postulates that we now have 2 consciousnesses, and that one of both is "the old one", assigned through the Born rule. This explains completely why, once you're born, you only "experience" the Born (hey :-) rule.
If you say X obeys one law of physics while Y obeys the other, even if this is true it is hardly useful if you cannot tell the difference between X and Y. I think if: 1) we do not have a strict (and common) definition of consciousness; 2) we are not aware of how consciousness physically manifests itself; and 3) we cannot determine which systems are and are not conscious, then it still seems a leap to claim that it is consciousness and consciousness alone that observes collapsed states.
Of course. But accepting that bodies are in superpositions of macroscopically distinct states, while we don't seem to experience this, needs then to come to the conclusion that what we experience is not the full state of our body. That's in fact all I'm saying !
What makes you think this? Actually, browsing down your post, you seem to doubt consciousness is a physical process as it would "constitute a deviation from standard quantum theory". This is what I was referring to with my analogy to the spiritual idea of consciousness. I'm not sure any theory of a non-physical consciousness can be regarded as anything other than, in some way, spiritual. I personally would go for consciousness being a physical process that can, in principal, be understood.
Well, in a way I even find it satisfying in some way to be pushed into these considerations, because after all, there is no physical explanation for conscious experience. There can be a physical explanation for all the *behavioural* aspects usually associated with consciousness (you heat that part of the body here with a flame, and the body says "aaaaahhh !", or other relations of the kind). But the very fact of consciously experiencing, or not, is something which has no physical explanation, and is bound never to have one, if you think a moment about it. It is not because you've programmed your computer to print on the screen "You hurt me" when you push the space bar, that you assume that you really cause some pain sensation in your computer. In the same way, you could say the same about a human body. It is simply because, when we do the same thing to OUR OWN body, and you experience pain, that you assume, by analogy, that that other body experiences something of the same kind. But when you transpose that to OTHER physical structures, you cannot use that analogy anymore, and then you are completely lost as to whether there has "really been a conscious experience" or whether the "behaviour is exactly as if there were such an experience by analogy as to how *I* would behave" because the "behaviour is also exactly as I expect according to the physical laws of the structure". So behaviourism is NOT going to indicate, ever, whether a physical structure is conscious or not and as such, you can conclude that consciousness is not really part of the physical world - it not having one single measurable property. However, the psycho-physical hypothesis is that, if there is a consciousness, it is always ASSOCIATED to some physical structure (this prevents ghosts from floating around, I guess). But in itself, it is not something that belongs to the physics of the structure itself, as in no way, it can give rise to anything observable (behavioural). I could think that that is established, with or without quantum theory.
And now the surprise in QM seems to be that that a priori non-physical item can resolve a riddle in the theory: namely the apparent clash between the unitary evolution which puts physical bodies into macroscopically distinct superpositions, and the fact that we don't experience that.
The simple explanation would simply be that QM is wrong then. I accept that possibility (I even hope for it). But given that we have no view of what it could be replaced by that will solve the issue, we can just as well stick to it for the moment and take it as a working hypothesis that it is strictly correct.
In that case, the clash between superposed bodies, and the conscious experience of only one of these states, can only be resolved by claiming that we consciously observe only ONE of the different bodystates. And that's all I'm saying. So this makes us enter consciousness, after all, into the physical world, but gives it a special place. It is NOT something that enters into the state of the physical universe (the wave function) ; it is something that simply gets associated with a term of that wavefunction, according to a special law of its own: the Born rule. Isn't that beautiful ?
So consciousness is not a quantum field or a particle or something, it is something that gets associated with certain physical structures (body: that's the psycho-physical hypothesis) which appear in the physical state of the universe ; only, it doesn't associate with the ENTIRE structure (which may not even have a sense in all terms), but only with ONE term ; and if the structure splits into two terms, it is now associated with only ONE term, according to the Born rule.
No, the reason why consciousness doesn't end up in an entangled superposition. See my second paragraph in this post.
Because it is not part of the wavefunction: it is not a degree of freedom of the physical universe described by the wavefunction, but something ASSOCIATED with a part of it.
First off, as per your description, will the wave function necessarily decohere in the same every time the memory is retrieved? Secondly, if you are willing to utilise decoherence at one stage, why not all and abandon the notion that consciousness somehow observes only one term altogether? Correct me if I'm wrong, but for decoherence in set-ups such as the double-slit experiment, a conscious observer is not necessarily required. As long as, in principal, you could determine which slit the particle went through, decoherence is present.
I would like to point out that decoherence does NOT make ONE term appear. Decoherence just makes the macroscopically distinct results appear in a superposition, but such that it becomes almost impossible to observe interference experiments between the different terms (them being so complicated that they remain essentially orthogonal, no matter what measurement interaction you apply to them). But decoherence does not solve the riddle of how to pick out ONE term out of the "interference-less" superposition.
Likewise if your photon detector made a 'click', whether you are there to hear it or not, decoherence will also be present. The argument then becomes one of when decoherence takes place, but if one requires an idea of a non-physical (and so inherently mysterious and maybe even unknowable) conscious and the special laws of physics it obeys, it seems an odd choice.
Decoherence really takes place rather quickly, but again, it doesn't pick out one term ; it just makes it very hard to observe interference phenomena between the different terms in the superposition.
Again, why is that 'something' consciousness and why is consciousness not a physical process?
For two reasons: I tried to outline above why - even apart from QM considerations - consciousness is not something physical, as it has no behavioural (measurable) quality at all. But in this context, it cannot be something belonging to the physical universe, because otherwise it would have its own hilbert space and hamiltonian and just get entangled with all the rest - so indeed, it would not be able then to "break the unitary curse" and to only see only one state of the body in superposition.
Bad choice of word on my part - apologies. My point is: 1. you adopt the notion that consciousness is not a physical process, which is akin to the view of consciousness of most religions
Granted. It is not because religions claim something that that must necessarily be completely wrong of course. It is not because I'm often a liar that I cannot look at the sky and say that it is blue !
; and 2. you are describing consciousness, something we know too little about, as obeying different laws than the rest of the physical universe, which seems to me to be something of a leap of faith.
Well, I think there are arguments - even outside of QM - that could claim so. Now, if you would rename "physical universe" by "that part of the physical universe described by the wavefunction" and claim that your consciousness is just another part of the physical universe, NOT governed by the wavefunction, but governed by the Born rule, it makes consciousness already something less supernatural.
I'll treat the rest of your (long) post later...
cheers,
Patrick.
, or even wilder stuff. Never thought that physics got so fun.
. Nevertheless, you could find differences: your examples were not mathematical objects that were required in a highly successful theory, but already "interpretations to make sense of it", added onto it. For instance, in Maxwell, the luminiferous ether was thought up to "carry" the E and B fields as mechanical vibrations. It was something put in by hand that wasn't required by the theory: nothing in Maxwell's equations refers to it. I mean: you can STILL make sense of Maxwell's equations which remain unaltered, without referring to the luminiferous ether. I have a harder time making sense of QM, without referring to a quantum state. It's more like saying "the E-field doesn't exist" in Maxwell (but we can do calculations with it), than to say "the ether doesn't exist".