On 4/29/2017 12:16 AM, David Nyman wrote:
On 29 Apr 2017 2:33 a.m., "Bruce Kellett" <[email protected]
<mailto:[email protected]>> wrote:
On 29/04/2017 1:18 am, Bruno Marchal wrote:
On 27 Apr 2017, at 23:22, Brent Meeker wrote:
The absurdity, if I've understood this, is that idea of
physical substitution leads to a conclusion that nothing
physical is needed.
The absurdity is that the first person experience in physics
has to be a sum on all computations (to be short).
This might cause some problems for the SAN04 argument. The "Yes,
doctor" assumption says that if my brain is replaced by a
functionally correct digital device (at the appropriate
substitution level), then I would not be aware of any experiential
change. But if my first person experience is the sum on all
computations that pass through my conscious state, then no digital
computer could ever be a "sum on an infinity of computations", so
my conscious state could not be reproduced in this way. In fact,
as has been said, the sum on all computations is not Turing
emulable. Thus my conscious state is not Turing emulable, and the
"Yes, doctor" scenario fails -- we would have to say "No" to the
doctor.
The second problem with the idea that the first person experience
has to be the sum on all computations, is that this renders
duplication of persons impossible. If you duplicate the
computation(s) that make up a first person experience, you have
simply added some more computations to that experience and the sum
over *all* computations is unchanged. Thus there is still only one
first person experience, and the attempted duplication fails.
So, if the "Yes, doctor" assumption, and the subsequent
duplication scenarios, lead to the conclusion that the first
person experience is a sum on all computations, the argument is
self-contradictory: the conclusion contradicts the input
assumptions and the argument is incoherent.
Well, you've certainly​ found a way to make it appear incoherent. But
here's another way to look at the matter that may help. The
multiplicity of machines implied by the UD are in principle
objectively distinguishable so in that sense there is no "sum".
However let's consider the situation vis a vis identical machine states,
A Turing machine consists of a finite state machine and a semi-infinite
tape. When you write "identical machine states" I assume you mean to
include the tape. But if the machine states were ever identical then
they would remain so - and as abstract TMs they would be the same machine.
Or are you referring to some subset of states of the TM which are
instantiating "you".
any of which might comprise, by assumption, my present subjective
state. Now there is no possibility of an objective mapping from the
subjective state to a single machine in the multiplicity. As Bruno
puts it, if I am indeed a machine, I can't know which one.
Because you're not any one in particular? That would be expected if
you'rea (quasi) classical being emerging from a quantum physics. But I
don't think that's what Bruno meant. I think he means that an algorithm
computing "you" can't know which algorithm it is, even if it is a single
(not sum) algorithm.
In that sense my present subjective state could be considered a "sum"
over those identical machine states. So if my brain were then to be
replaced by a functionally identical prosthesis there would be no
change in that "sum" and so my experience, again by assumption, would
be unchanged.
I think unchanged experience is too strong a requirement. Your blood
has K40 atoms whose decay may very well, on occasion, make a difference
in experience or even decision and changing a neuron into some silicon
based electronics would certainly change your susceptibility to local EM
fields. To say "yes" to the doctor is just supposed to express
confidence you'd still be conscious.
But I'm still unclear on what "identical machine states" refers to. The
UD is running every possible program - not just Nyman1.0. So are you
just talking about identical states of a prosthetic brain the doctor
installed?
Brent
Ditto for duplication of persons. The key point here is to distinguish
between the third-person (computational) and first person (perceptual)
situations​. Of course, when one looks beyond any given present state,
divergence of subsequent machine state continuations would then in
principle render the associated personal histories both objectively
and subjectively distinguishable.
Hope this helps.
David
Bruce
So even if a physical universe exists, it *cannot* have any
influence on my prediction. Physics lose *all* its prediction
power. Computationalism saves physics, we should say, but
makes it more modest when wandering on metaphysics.
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