On 16 Dec 2011, at 10:39, Russell Standish wrote:

On Mon, Dec 12, 2011 at 04:11:54PM +0100, Bruno Marchal wrote:
Maudlin's argument relies on the absurdity the the presence or absence of inert parts bears on whether something is consious. This absurdity only works in a single universe setting, however. If your computer is embedded in a Multiverse, the absurdity vanishes, because thiose inert
parts are no longer inert.

But they do not play a part in the computation, at the correct
substitution level.

They certainly look like they are. If these parts weren't present, the
calculation proceeds differently in the other branches of the
Multiverse. In other words, counterfactuals are not handled correctly.

If you think of a quantum multiverse, then that argument would work if the brain is a quantum computer. If it is classical, its states can be considered as having been prepared in the classical base, and the computation (or non computation) will be handled correctly in each branch of the quantum multiverse, in which the same MGA reasoning will apply.

So you are introducing a different kind of physical multiverse, which would handle the counterfactuals. But this will not work. Either this physical multiverse, which plays the role of the generalized brain, is Turing emulable, in which case I can emulate it in a single Turing machine, for which the MGA will apply again. Or it is not Turing emulable, but then the need of it will contradict the comp assumption.





They are playing a part concerning the first person indeterminacy,
like in the UD*, or in QM physics. But that is derived (and has to
be) from the indeterminacy.


They do that as well, but this is not relevant to Maudlins argument...

The parallel realities does not play any role for a classical computation, except for statistical interference (in case of a quantum computer). But if this play a role, it means that we have not chosen the right level of substitution. Once it has be chosen correctly (or below), what happens in some other branch cannot interfere or play any role in the computation.





If you then fold the multiverse back into a
single universe by dovetailing, one can then reapply the Maudlin
move.

Indeed. That is the key point.



But then, in that case, one can embed that result into a
Multiverse, and the cycle repeats.

I don't think we can. That would be like saying that we have to
start from the quantum multiverse, but the reasoning show that we
can start from any universal machinery, like numbers. To start from
the multiverse would be treachery (for the derivation of matter) and
ambiguous (we don't assume QM). And even with QM, the multiverse
notion is quite complex and controversial: is it a non computational
multidreams (as forced by comp), or is it a multi-physical material
reality (as forbidden by the MGA).

I do start with a Multiverse for Occams razor reasons (it hardly
treachery), and I know you don't (since it is derived in your
case). However, that is beside the point for Maudlin's argument. I'm
only observing that Maudlin's argument fails in a Multiverse reality.

If the register "323" is missing in one branch of a quantum multiverse, it is missing in all normal extension of the computational state of the machine. Some rare branch will have the pieces, and from there (and thus from the first person point of view of the subject) everything will go well, by comp. But only because we fall back in a branch where the piece is not missing. This is not different than the comp or quantum immortality argument. The fact remains: the physical activity in one normal branch missing the register is the same as the physical activity in some branch not missing it, for the same particular computation. Then Maudlins argument shows correctly that the physical activity can be made arbitrary (and even non existing), showing that comp links consciousness not on the physical activity of the program, but on the computational (in the sense of computer science) structure only, making matter and physics an epistemological indexical for the conscious entity involved.









The question is - where is the consciousness in all this? I think it
must move with the levels - and given the UDA and COMP, I would say
that consciousness appears at the Multiverse level, not the single
universe level.

That is right, but with comp that "multiverse" is the mathematical
structure which needs to be entirely derived from the theory of
consciousness or from the self-reference logics.


Why? I can see how, but why?

Keeping comp, we might say "only by Occam", but that would be weak, given the fact that not much of known physics is handled by comp currently. But then the reason why we have to do that, even without Occam, is the MGA argument. If some physical reality is at play in the brain for it having a role in the making of consciousness, comp makes it Turing emulable in a single reality, and it that single reality we can change the computer structure so that his physical activity is arbitrary, by adding, like Maudlin some physically inactive piece of matter, for handling the counterfactuals. And what I say above will apply.







BTW - I had a similar problem with your MGA - it is not intrinsically
absurd to me that a recording can be conscious.

There is no computation in a recording. There is only a fixed
description of a computation. In arithmetic, it is like confusing p
and Bp.

This also means there is no computation in a block universe like UD*.

I think this needs to be spelled out. It is not so obvious.

UD* contains a lot (all) computations. Indeed they are executed by the UD, or by the additive and multiplicative structure of the natural numbers. I think that you are confusing UD* with a description of UD*, which would contain all descriptions of all computations. But this is already given by the counting algorithm: which generate 0, 1, 2, 3, and thus all description of all computations. yet the counting algorith is not Turing universal, and does not make any computation. UD* is not just a collection of all description of computations, it is a mathematical structure which execute, even if only in the arithmetical sense, all computations. You do at the UD* level the same mistake done by those who think that a recording or a cartoon executes a computation, when it only describe one. UD*, unlike the counting algorithm, *executes* a computation (and can perhaps describe them too) in virtue of relating arithmetically the numbers. The computation is in the arithmetical (or combinators related, ...) true relational structures of the numbers (combinators, etc.), not in the description of the computations. (N, +) describes all computations, but does not run any program, except the program sending x on x+1. The UD, or the structure (N, +, *), does generate and run all programs. The proof that the counting algorithm describe all computations can be done in very few lines. The proof that the sigma_1 arithmetic (par of (N,+,*)) runs all computations cannot be made in less that 50 pages. The UD*, like a block universe, is a very rich and subtle structure.





With p sigma_1,  p and Bp looks alike (which explains the subtlety
of that nuance) in the sense that we have both
p -> Bp and
Bp -> p
But Bp -> p is only true (provable at some [ ]*-logic level), and
not provable by the machine, so p and Bp will still behave in a
different logical way.

I see the difference between p and Bp, but not the relevance to
recordings and computation. Sorry to be difficult here.


No problem. I know that the point is subtle. p here is supposed to correspond to some computational truth, and Bp for a proof of that computational truth. The problem is that "p" is also a proposition, and as such it will involved a description of that computation. But the computation is in the meaning or the truth of some number theoretical relation p, not in the description of p which is needed because we are talking. Then the same occur at the meta-level, with Bp. And, for p sigma_1, the same are equivalent, but not provably for the machine.

The relation with the recordings and the computation is the following one. To have a computation you need a universal system relating (logico-arithmetically) steps of a computation. A description of a computation does not relate the steps by itself. It described how the steps are related, but only the original computation executed by some universal system (the filmed one), has illustrated the true existence of the relation, which can then be described by the movie, which do no more any computation.

A proof that a computation exist can only be done by a proof that the description of the computation exist, and p and Bp will be logically equivalent (for a self-referentially correct machine, and p sigma_1 (computational)), but this does not mean that a computation is the same object than a description of the computation.

I would like to say this in some more easy way, but it is hardly possible, because to talk on a computation, I have to describe it. It is more easy at the meta-level, where I can identify a computation with, say, a universal machine, and a sequence of numbers describing the evolving states of the machine run by the universal machine. Then a description of this by a machine will be just one number coding that stuff. But typically you might accuse me of describing the difference between Bp and BBp. It just happens that I cannot describe p. The difference is really the same as the difference between the true fact that 5 is a prime number, and the sentence "5 is a prime number", which might be true, or false, according to the semantics a universal machine will use to decode and interpret that strings of letter.






Then you have the stroboscopic argument which shows that a recording
like a movie is not well defined in time and space.
But the simplest, imo, to see that a recording cannot be conscious
(with comp, 'qua computatio') is that there is no more any
computations done by a recording.


The computations may be phenomenal to the consciousness in
question. If not, why not?

By definition of a computation. There is a real program linking the states of a machine, like the UD, or like a local physical universe (in some conception of them), or any universal machine. With comp, the reason why you are conscious here and now, is that it exist a computation going through you state. But your consciousness is not in any description of any computation, it is in the truth of the (relative) existence of that computation.



We have often talked about what links
observer moments together in this list.

It is a universal system. If we start from the numbers, it is the truth of number theoretical proposition. It arises from the non trivial additive/multiplicative structure of the numbers do the relations. Those relations are independent on us. The only problem for us is that there are an infinity of such relations, and we can only bet on the local most probable universal history. Below our substitution level, all universal machines run by the UD are fiercely competing.






From the right point
of view (presumably that of the consciousness itself - aka the "inside
view"), it seems plausible that a recording could be conscious.

A still other argument, is that no piece of the movie can have any
causal relationship with any other part, and so can be removed,
making eventually a *particular* consciousness (a dream about an
ice-cream, for example) supervening on the vacuum.

Isn't this what you were calling the "stroboscopic argument" above?

I am not sure why you say so. In the stroboscopic argument, we move an observer along a giant version of the movie's pellicle, with a stroboscope sending a flash from infinity (say) so that the observer see a movie. But the presence of the observer plays no role in the presence of absence in a device he is looking for. So we can remove it, but then we have just a giant pellicle + a stroboscope, and the identification of consciousness with state of the movie in time does no more make any sense. We don't remove any part of the pellicle, like in the argument just sketched above.






What is correct is that consciousness is related to all events
having made the recording possible, but this is only in virtue of
some numbers having some special relations with other number, and we
are back to the computationalist supervenience thesis.

We might come back on MGA, given some other questions on the list.
So if this is unclear you might ask question, or wait that I
re-explain the whole argument perhaps.


I remember when you were explaining the MGA before, we got to this
point where you relied on recordings not being conscious, and I think
you said you hoped you didn't need to explain that bit :).  I did ask
why at the time.

It seems I have answered that. It is true than in the first 1988 version, I just say that to confuse a movie about a fact, with the fact itself, is the biggest error a philosopher can do: confusing reality with a representation of a reality! But alarmed by the fact that some people seems to want to make that confusion in the case of a running computer and a (high resolution) movie of a running computer, I provided the stroboscopic argument (in the french thesis), or the usual removing part (of the pellicle) of non necessary components.




Its not a biggie though - just one of those "not understanding all the
steps" things.


There is no problem, Russell. The MGA is at the heart of the mind body problem with comp. UDA1-7 already proves a lot (indeterminacy, non locality, non cloning), but you can still escape the non-materialism by conceiving that the physical reality is too much little for running a significant part of the UD. MGA is supposed to show that this moves is a red herring.

Some people believe that MGA is not needed, and indeed you can add to comp some principles like "no arithmetical zombie in arithmetic", or that "something no material cannot act on something material + "I" can act on matter", etc. Or even just that "physical reality is infinite". But those principles are hard to make precise, or hard to justify, and the MGA, it seems to me, makes them unnecessary.

The difficulty is that we cannot describe the truth of an arithmetical proposition without going trough a description of that arithmetical proposition, and the same appears for the computations.

It is like the difference between the fact that 2 + 3 = 5, and the sentence "2 + 3 = 5".

It is is even more like the difference between a proof that 2 + 3 = 5 and a description of a proof that 2 + 3 = 5.

It is also deeply related with the difference between the formal implication p -> q, and the deduction p => q, or like as I said, at a higher level, the difference between a machine computing some function, and the sentences (perhaps written in a language that the machine can 'understand') "I or the machine compute(s) that function".

I hope this helps a bit, ask any precision at any level. It is obviously a difficult matter, combining the nasty subtleties of philosophy of mind with the nasty subtleties of theoretical computer science and mathematical logic.

Bruno



http://iridia.ulb.ac.be/~marchal/



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