Russell Standish wrote:
> I had a thought about an alternative way of expressing the UDA
> (universal dovetailer argument).
>
> Computationalism is the statement that "I am a computation". To use
> the RITSIAR acronym, computations are real in the sense I am real. But
> the Church-Turing thesis gives a particular model of a computation, it
> is effectively defining a computation as something that there is a
> Turing machine emulating.
>
> The universal dovetailer is a computation. Contained within its
> execution trace, are the execution traces of all other programs,
> including itself. If we are a program, we can be found inside a
> universal dovetailer, which can be found within another UD (infinitely
> many, in fact).
>
> To say that there must be a physical computer on which the dovetailer
> should run, is rather similar to saying there must be an ultimate
> turtle upon which the world rests.
Not really. There is no need for even one turtle. But, depending
on the definition of "computation", there may well be a need for
a "hardware platoform". If a computation is defined as description
of, or behaviour of, or function of some system, the system
itself is necessary. You can't have the software without the
hardware any more than you can have a smile without a mouth.
> The little old lady was right in
> saying "its turtles all the way down". Of course it is also analogous
> to saying there must be a prime mover to start the causal chain. If
> God created the world, then it immediately poses the question "Who
> created God".
The software/hardware (computation/computer) relationship
isn't *that* analogous to the cause/effect relationship.
Causes and effects are ontologically distinct. But there
is nothing ontoloigcally to the software that is not already
int he hardware.
> Since it makes no difference in any observable respect whether we are
> living in a computer simulation running on a bare substrate, as one
> that is incidently computated as part of a universal dovetailer, or an
> infinite chain of dovetailers, we really can make use of Laplace's
> ripost to Napoleon "Sire, I have no need of that hypothesis" with
> respect to a concrete computer running our world.
You cannot dismiss empirically what is logically necessary.
> To rescue the primitive matter world, we need to deny the existence of
> the universal dovetailer.
That is easily done.
> But this denies the Church Turing thesis -
> we have to say some computations exist (eg ourselves), but others
> don't.
Not even remotely.
The CT thesis states:
"every effective computation can be carried out by a Turing machine."
It doesn't guarantee that any physical system is computer-emulable,
it doens't guarantee that anything emulABLE is actually being
emulATED and it doesn't guarantee that anything, a running UD or
otherwise,
exists Platonically.
It doesn't
require that they *are* emulated, nor that
> To make computationalism compatible with primitive materialism
> requires us to abandon the Church-Turing thesis and redefine what we
> mean by computation.
Re-definition is impossible, since definition has not taken place...
in any case, we only need abandon Platonism, if we ever adopted it.
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Received on Mon Nov 20 2006 - 14:43:13 PST