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
of inert parts bears on whether something is consious. This
only works in a single universe setting, however. If your computer
embedded in a Multiverse, the absurdity vanishes, because thiose
parts are no longer inert.
But they do not play a part in the computation, at the correct
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
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
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
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
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
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
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
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
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 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
From the right point
of view (presumably that of the consciousness itself - aka the
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
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
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.
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