On Fri, Dec 16, 2011 at 05:42:19PM +0100, Bruno Marchal wrote:
> 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

Nobody here is proposing that the brain is a quantum computer. Penrose
and Lockwood do, but that's an entirely different hypothesis.

> 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.

In Maudlin's argument, the inert parts are only inert by virtue of the
counterfactuals not having been realised. In a multiverse, the
counterfactuals are realised, but in different branches. Hence those
"inert" parts are no longer inert in all branches. If they were, they
could be removed from the computer altogether, without affecting the

> 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.

This step, as I understand it, is a form of dovetailing. Nobody really
thinks of the dovetailer algorithm as instantiating consciousness, so
the move is ultimately invalid, I would think.

> >
> >>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). 

It is not a question of the parallel realities playing a role in the
computation, but in the supervenience. Maudlin's argument says If
COMP, then supervenience on single universe is contradictory. But it
doesn't say anything about supervenience on multiple parallel realities.

> 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.

I don't follow...

> >
> >>
> >>>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 think I'm coming around to the view that neither of the above steps
are valid - but one could equally say they are as valid as each other.

... snip ...

> 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. 

This is a bit confused. Surely the register is missing in all future branches,

> But only because
> we fall back in a branch where the piece is not missing. 

Why? Are you saying that if consciousness requires the presence of
register 323 at some particular point, then we find ourselves
instantiated by a computer with such a register? But then surely,
never at any point would we find ourselves instantiated by a machine
without register 323 - presumably for most of our history we would be
unaware of whether the register existed or not.

> 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.

In all branches, or just special ones? If all branches, then the
register is totally unnecessary. If just a special pair of branches,
then Maudlin's argument shows that supervenience must occur across
more branches than those two.

> 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.

Yes - it shows that physical supervenience is impossible in that
single reality.

But this doesn't answer the why question. I could imagine that you
might feel that Multiverses are otiose, so would prefer a derivation
of their existence from something "simpler" - eg arithmetic of the
whole numbers.

That's fine and dandy - but the Multiverse is not otiose - it is far
less of an impost than a single reality. 

I know you're keen to attack the Aristotelian primary matter
position. To be quite honest, its not a question I care too much about
- I'm happy for my matter to be phenomenal, not primary. But I do
think we need to be careful about throwing out supervenience of mind
on matter (of whatever stripe), otherwise the Anthropic principle
becomes mysterious, and we're faced with what to do about the Occam

I'm snipping the following text because it moves away from Maudlin's
argument in particular, and also there's some juicy stuff in it I need
to absorb before responding (if indeed I do :).



Prof Russell Standish                  Phone 0425 253119 (mobile)
Principal, High Performance Coders
Visiting Professor of Mathematics      hpco...@hpcoders.com.au
University of New South Wales          http://www.hpcoders.com.au

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