2009/5/4 Bruno Marchal <marc...@ulb.ac.be>:
>> in the same way a
>> message is obscured if encoded with a one-time pad that is
>> subsequently destroyed and forgotten. In fact, even with the
>> store-bought computer the computation is obscured if there are no
>> intelligent beings around who can understand it.
> Not at all. If the computer evaluate fact(4), even alone in a room,
> the probability it gives 24 is one, in a verifiable way by a third
> person. With or without physicalism we accept the idea that the
> physical neighborhood is locally Turing universal, and does interpret
> the computation of 4.
Sure, the computer is evaluating fact(4) even when no-one can
understand it, but it is obscured because no-one can understand it. An
intelligent person who has never seen a computer before may eventually
figure it out, and computers are as a broad generalisation designed to
follow understandable patterns in their architecture, just as written
languages are designed (or evolve) to follow recognisable patterns.
But what if fact(4) is a military secret, and the engineers
deliberately tried to make the internal workings of the machine as
convoluted as possible, so that it looks like random activity to
anyone lacking the design specifications? This would be the equivalent
of taking a written message and encoding it so that it looks like
random letters; with the right key, any message can be encoded to look
like any given string (of similar or greater length). Are you saying
that obscuring the workings of the computer in this way would be
> It seems to me that we agree that physical supervenience leads to many
> absurdities. Is your argument purely academical, or do you think it
> can be used to prevent the conclusion that physics has to be explained
> by the purely mathematical notion of "most probable computation as
> seen from inside", among the 2^aleph_0 computations going through the
> current states, in UD* or in arithmetic?
I agree with you. I am not terribly happy with the conclusion, because
it seems so weird. The only way out is, as you say, if comp is false:
the mind is not Turing emulable, or (even weirder, perhaps incoherent)
there is no such thing as consciousness at all.
> With you argument, the movie-graph is conscious. But is all
> consciousness at once, not just the consciousness corresponding to the
> filmed boolean graph. This not change the problem measure in any way.
> It makes the primitive physicalness idea even more absurd.
> It seems to me that your point just recall that in Platonia, there are
> complex sequence of universal machine which can interpret any
> computation, including the empty one, as being any other computations.
> But this is akin to white rabbits (from the probability pov) and akin
> to the fact that, with its terrible redundancy and "free
> imagination", the UD generates also conspirator interpretations.
> With just arithmetic, when we stop to postulate a primitive or
> ontological material world, all primitive ad-hocness is removed, given
> that the existing internal interpretations are all determined, with
> their relative frequency, by addition and multiplication rules, and
> physics will be defined by the (absolute) probability of relative
> computations (here = probability of relative number theoretical
> relations. "to be a finite piece of computation" is decidable even in
> very tiny fragment of arithmetic, and this can be used to avoid any
> starting ambiguity. This is made possible through Church thesis, and
> it eventually forces us to realize that a rock is the result of an
> infinity of computation, and the rock "we see" a crude local average,
> but comp makes it possible that a rock implements all computations to,
> but only by an explicit call to a sequence of universal machine in
> Platonia. Meaning; there is no room for providing an explanative power
> (both for mind and matter) to the notion of primitive substance and
> primitive substancial incarnated laws. Due to the failure of logicism
> we need numbers or combinators and primitive immaterial laws to agree
> on, like addition and multiplication, or lambda abstraction and
> application, etc. The measure does not depend on which first universal
> system you choose, by non completely trivial application of computer
> science. And to use a primitive quantum computer for a primitive
> physics is treachery with respect to the comp mind body problem.
OK, I think. Thanks for taking the time to reply!
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