On 3/26/2015 6:04 PM, Bruce Kellett wrote:
Bruno Marchal wrote:
On 26 Mar 2015, at 08:05, Bruce Kellett wrote:
I simply say, so what! Counterfactual equivalence does not have any independent
justification, and it is highly unlike to be sensible, even in the context of
computationalism.
You are quick here.
I might explain the stroboscope machinery which might help me to ask you what you mean
by consciousness supervening to a recording, given that no computation at all is
involved in the recording.
Basically, because the simulation of any given conscious state can be carried out an
any computer -- whatever the architecture, physical construction, or programming
language. As long as the original state is accurately simulated, the conscious state
will be the same.
It is not the state which must be correctly simulated, it is the relation between those
state/ You need the truth of the proposition IF the input change, I do some this or
that". That truth is part of what define my person, and it is not applied in the movie.
The movie is a sequence of description of states, not a sequence of states related by
some universal number.
As is usual with debates of this kind, I think we are talking about two different
things. When you introduce the possibility of the Dr replacing your brain with a
simulation, you mean "an artificial intelligence program initialized by the synaptic
weights read out from your old brain". In other words, this is not simply a recording of
the state of the brain at one instant, it is a full description that would enable the
brain to be reconstructed. In other words, it is a prescription for producing a model of
your brain -- a simulation.
I agree it is clear that this model is conscious only when it is running. If you write
down the Godel number of the description, that is a static object and would not be
considered conscious in itself. But this description could be used to build a model in
any medium, be it a computer, or a system composed of billiard balls. Provided the exact
details are modelled, the model will be conscious when the simulation is run.
The other thing (that seems to be introduced with the MGA) is the we observe the active
brain and record it from instant to instant in sufficient detail that we can observe
which neurones are active, which connections are made, and in which order. This is
effectively the "movie". It records a certain period of conscious activity, but it does
not contain the information necessary to construct a model that can go on operating
independently outside the original recording period.
The question is: if I replay the recording of the second type, do I recreate the
conscious experience? Note that this is not a simulation in the normal sense, it is a
replay of a recording of the relevant parts of the brain undergoing conscious activity.
If conscious supervenes on the physical brain so that the pattern of connections and
neurone firings constitute the physical manifestation of the conscious experience, then
rerunning the recording will recreate the conscious experience.
It is essentially the same as if I am running the simulation on the computer I observe
all the registers and memory of this computer then recreate exactly this pattern of
registers and memory data by some other means than by running the original program. If
one creates a conscious experience, then so does the other.
The argument seems to be that the replay of the recording will not recreate the
conscious experience because it is not counterfactually correct. I do not think that it
has been demonstrated that this is relevant. If exactly the same physical activity of
the brain has been replayed, then exactly the same consciousness would be experienced.
This is the meaning, as I see it, of saying that consciousness supervenes on the
physical state of the brain (or, probably more correctly, on the sequence of physical
states). Sure, replaying the movie does not reconstruct an individual that can go on
functioning independently once the movie finishes -- but that was not the idea. We are
reproducing a conscious moment, not simulating a conscious entity in its entirety.
The Movie Graph Argument is an attempt to argue that this concept of physical
supervenience is absurd, so that consciousness supervenes only on the (counterfactually
correct) computation. I think the argument fails because it assumes what it attempts to
prove. Namely, it assumes that physical supervenience is false (absurd).
Bruce
I think counterfactual correctness is necessary for a process to be a computation.
Otherwise, I think the process is equivalent a sequence of states A,B,C,... and there can
be a translation into a completely different set of states a,b,c,... which then putatively
instantiates the same computation. This is what motivates the counterfactual correctness
requirement.
I would claim though that getting counterfactual correctness mean anticipating and
providing for all possible events, which in turn means incorporating a very large part of
the world into the process to be recorded - maybe all the past light cone. If you do that
then the MGA is about simulating a world and it's trivial that the brain part of the
simulation experiences that world *within the simulation*.
Brent
"It’s quite something to be the subject of a major film. It makes you realize how short
life is when they cut out the boring bits."
--- Stephen Hawking
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