Peter Jones writes (quoting SP):
> > There is a very impoertant difference between "computations do
> > > not require a physical basis" and "computations do not
> > > require any *particular* physical basis" (ie computations can be
> > > physical
> > > implemented by a wide variety of systems)
> >
> > Yes, but any physical system can be seen as implementing any computation with the appropriate
> > rule mapping physical states to computational states.
>
> I don't think such mappings are valid
> a) without constraints on the simplicity of the mapping rules
> or
> b) without attention to counterfactuals/dispositions
>
>
> > Attempts are made to put constraints on what
> > counts as implementation of a computation in order to avoid this uncomfortable idea, but it
> > doesn't work unless you say that certain implementations are specially blessed by God or something.
>
> I don't know where you get that idea. Dispositions are physically
> respectable. Simplicity constraints are the lifeblood of science.
The constraints (a) and (b) you mention are ad hoc and an unnecessary complication. Suppose Klingon
computers change their internal code every clock cycle according to the well-documented radioactive
decay pattern of a sacred stone 2000 years ago. If we got our hands on one of these computers and
monitored its internal states it would seem completely random; but if we had the Klingon manual, we
would see that the computer was actually multiplying two numbers, or implementing a Klingon AI, or
whatever. Would you say that these computations were not valid because it's a dumb way to design
a computer? Would it make any difference if the Klingons were extinct and every copy of the manual
destroyed? What about if the exact same states in a malfunctioning human computer arose by chance,
before the Klingons came up with their design? Having the manual is necessary to make the computer
useful, so that we can interact with it, but it doesn't magically *create* computation where previously
there was just noise.
> > So at least you have to say that every computation is implemented if any physical universe at all
> > exists, even if it is comprised of a single atom which endures for a femtosecond.
>
> Hmmm. So much for the quantitative issue. What a strange view of
> physics you have.
This says nothing about physics. There may well be a physical universe, with orderly physical laws,
and our computers would have to be of the familiar type which will consistently handle counterfactuals
in order to be of use to us. But I think it is trivially obvious that any computation is hiding in noise just
as any statue is hiding in a block of marble. This is not very interesting unless you say that computation
can lead to consciousness. You could specify that only brains can lead to consciousness, or that only
non-solipsistic computations with inputs and outputs based on physical reality can lead to consciousness,
but that's not straight computationalism any more.
Stathis Papaioannou
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Received on Thu Jul 27 2006 - 20:32:02 PDT