Bruno Marchal wrote:
On 06 May 2015, at 04:19, Bruce Kellett wrote:
Counterfactual correctness has not been shown to be necessary -- it is
just an ad hoc move to save the argument.
Counterfactual correctness is the bone of what *is* a computation. To
have a computation, you need a universal system capable of understanding
instruction of the type IF A THEN B, ELSE C.
The local truth of the C act must be "caused" by the local falsity of
the A predicate. The computation is in the semantic of those type of
truth, at some level description of yourself.
This is not necessary for computation. It would occur only in a program
that required branching at some point if the input at that stage
differed. Computation is perfectly possible without this requirement. If
you have a simple linear program that computes an output for each input,
then a recording of the action for any particular input, when replayed,
would reconstruct that computation exactly. Counterfactual correctness
is not required in such simple cases. And likewise, it is not required
in more complicated situations, such as where there is a loop, say, that
requires different actions on different iterations of the loop. The
whole calculation, and hence its recording, follows all these
iterations, and the recording reproduces them all exactly. If this
program instantiates a conscious moment, or a whole conscious life,
replaying the recording recreates that moment or life. Just as a
recording of an orchestral symphony reproduces each bar of the symphony
as well as the whole, following exactly the fact that each instrument
plays different notes and sequences of notes in different contexts in
the score. Conterfactual correctness is just a distraction.
You can't question the actors in a James Bond movie and expect to get
anything sensible, of course. But then, no one is suggesting that a
movie of someone's face records the basis of their consciousness. The
movie in question is a recording of the basic brain processes (at the
necessary substitution level). This, when replayed, recreates the
conscious moment -- not a new conscious moment, as you point out, but
a conscious moment nonetheless.
The existence of the movie (perhaps with the checking that it *is* a
computation) might be used to prove that the computation exist, and
consciousness can be associated ... with the computation, but not with
the description of the computation itself. But physical syupervenience
would imply that, and so it is just wrong that consciousness supervene
on a brain or a computer. It supervenes of the mathematical computation
that a physical computer can incarnate, if the physical is the winner on
the sum of all computations below the substitution level.
If it did not, then the original comp argument fails -- we could not
replace all or part of our brain with a device performing the same
operations.
We did assume that a computer is needed, for the local manifestation of
my consciousness. At this stage, assuming it is has to be primitively
physical is begging the question.
What does beg the question is your assumption that the physical
substrate, be it primitive or not, can be dispensed with. MGA does not
establish that either the original computer, or the recording of its
operation run on another physical device, can simply be disregarded. If
you take away both the physical device and the record player, then you
no longer have the conscious moment and/or life.
Bruce
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