On 17 Dec 2011, at 05:06, Russell Standish wrote:

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.

OK. Just saying that MGA works independently of the comp level.



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.

OK.


In a multiverse, the
counterfactuals are realised, but in different branches.

Not necessarily. If the computation is classical, it is the same in the normal continuations. The classical counterfactuals are not realized in a quantum multiverse. You have to put the Klara in some superposition state to do that. You need a quantum Olympia.




Hence those
"inert" parts are no longer inert in all branches.

I don't see this.



If they were, they
could be removed from the computer altogether, without affecting the
computation.

But that is the case for the computation under consideration.





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.

The problem is there. With comp + the physical supervenience thesis, the dovetailing algorithm does instantiate consciousness.








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.

Those are relevant for the relative measure on continuations.
Unless you are using a non Turing emulable multiverse, whatever physical supervenience thesis you are using, you can come back to a single reality. You will not say "yes" to a drunk doctor, because you bet that in some parallel realities he will be sober.




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...

Computation are by definition based on the running of a single universal machine. Even in the quantum case. Quantum computer can be emulated in a single reality or by a single well defined universal machine. The inert pieces handles classical counterfactual at the comp substitution level.







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.

Not sure I see which steps you are talking about. The MGA is a reductio ad absurdum from comp + physical supervenience.





... 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.

Yes...

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,

Not in the (rare) white rabbit type of branches, where the register can reappear by a lucky vacuum fluctuation.





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?

I am saying this assuming that the "323" principle is false, to get the contradiction.




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.

That's the point.




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.

In this case the same computations, with the same inputs are done in all branches.



If just a special pair of branches,
then Maudlin's argument shows that supervenience must occur across
more branches than those two.

There is no more branches. We are now simulating all the branches in a single reality. If that is not possible, then comp is already false.




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.

OK, but then to make your argument you have to shift toward a multi- multiverse, given that we have come back to a single universe. And the argument can continue: I will just simulate that multi-multiverse in a single branch on a single classical universal machine. If that is not possible, then comp is false. If that is possible, then MGA will apply again.




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.

Not at all. It is the idea that there is primary matter which is otiose, or epistemologically contradictory. It is physicalism which is show wrong. The multiverse is shown to be emergent from a numbers multi-dream. Physics becomes a branch of machine's theology.




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

Yes. We agree on this. It is the main theme of this list. The question is not about their existence, but their primitivity.




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.

The MGA is just an help for people to realize that comp makes this necessary.



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
catastrophe.

Matter (like consciousness) are fundamental and plays a big role in the big picture, but the point is that they are not primary. UDA 1-7 has already reduce physics to classical computer science/ number theory, except that some can still make the move toward a single little physical reality (with non concrete UD running in it). MGA shows that such a move is a red herring.



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 :).

Enjoy :)

Bruno


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



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