On 13 Feb 2010, at 19:48, Jack Mallah wrote:

--- On Fri, 2/12/10, Bruno Marchal <marc...@ulb.ac.be> wrote:
Jack Mallah wrote:
--- On Thu, 2/11/10, Bruno Marchal <marc...@ulb.ac.be>
MGA is more general (and older).
The only way to escape the conclusion would be to attribute consciousness to a movie of a computation

That's not true. For partial replacement scenarios, where part of a brain has counterfactuals and the rest doesn't, see my partial brain paper: http://cogprints.org/6321/

It is not a question of true or false, but of presenting a valid or non valid deduction.

What is false is your statement that "The only way to escape the conclusion would be to attribute consciousness to a movie of a computation". So your argument is not valid.

OK. I was talking in a context which is missing. You can also conclude in the prescience of the neurons for example. The point is that if you assume the physical supervenience thesis, you have to abandon comp and/ or to introduce magical (non Turing emulable) property in matter.

I don't see anything in your comment or links which prevents the conclusions of being reached from the assumptions. If you think so, tell me at which step, and provide a justification.

Bruno, I don't intend to be drawn into a detailed discussion of your arguments at this time. The key idea though is that a movie could replace a computer brain.

What do you mean? I guess you mean: COMP + phys. supervenience entails that a movie can replace a computer brain.

The strongest argument for that is that you could gradually replace the components of the computer (which have the standard counterfactual (if-then) functioning) with components that only play out a pre-recorded script or which behave correctly by luck.


You could then invoke the 'fading qualia' argument (qualia could plausibly not vanish either suddenly or by gradually fading as the replacement proceeds) to argue that this makes no difference to the consciousness. My partial brain paper shows that the 'fading qualia' argument is invalid.

I may be OK with your point, but I am not using the 'fading qualia' argument. Just the physical supervenience (to show it absurd by 'reductio').

I think there was also a claim that counterfactual sensitivity amounts to 'prescience' but that makes no sense and I'm pretty sure that no one (even those who accept the rest of your arguments) agrees with you on that.

It is a reasoning by a an absurdum reduction. If you agree (with any computationalist) that we cannot attribute prescience to the neurons, then the physical activity of the movie is the same as the physical activity of the movie, so that physical supervenience + comp entails that the consciousness supervenes on the movie (and this is absurd, mainly because the movie does not compute anything).

Counterfactual behaviors are properties of the overall system and are mathematically defined.

But that is the point: the counterfactuals are in the math. Not in the physical activity. That is why comp forces the computational supervenience. But then the appearance of the physical world(s) will eventually be in need to be recover from the mathematical computation.

Jack Mallah wrote:
It could be physicalist or platonist - mathematical systems can implement computations if the exist in a strong enough (Platonic) sense. I am agnostic on Platonism.

This contradicts your definition of computationalism given in your papers. I quote your glossary: <<Computationalism: The philosophical belief that consciousness arises as a result of implementation of computations by physical systems. >>

It's true that I didn't mention Platonism in that glossary entry (in the MCI paper), which was an oversight, but not a big deal given that the paper was aimed at physicists. The paper has plenty of jobs to do already, and championing the possibility of the Everything Hypothesis was not the focus.

I don't follow you. The point is not the everything hypothesis, just that the movie graph makes consciousness supervene on the computations (in their usual mathematical meaning) and not on the physical activity, which has to be redefine from the structures of the "many computations".

On p. 14 of the the MCI paper I wrote "A computation can be implemented by a physical system which shares appropriate features with it, or (in an analogous way) by another computation." If a computation exists in a Platonic sense, then it could implement other computations.

But here you don't distinguish the first and third person points of view. No universal (mathematical) machine can know which computations bear it, and its next personal state has to be recovered from the statistics on the possible relative continuations.

Bruno Marchal

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