On 26 Dec 2011, at 05:47, Joseph Knight wrote:
On Sat, Dec 24, 2011 at 9:05 AM, Bruno Marchal <marc...@ulb.ac.be>
On 23 Dec 2011, at 20:16, Joseph Knight wrote:
The same problem arises in Part 2. Bruno claims that we are forced
to accept that Alice’s consciousness supervenes on the film.
No. On the projection of the pellicle on the Boolean graph, and
then on the Boolean graph missing part. The idea is that we built
again the right physical activity, with the projection of the film
playing the role of the cosmic rays.
What is a pellicle? (Sorry) I understand this part, however. My
objections arise later.
A film. (But in french "film" is for cinema (movie?)).
OK, there was no confusion.
but (film + optical graph) is certainly changed, and Alice’s dream
turns out differently (if it occurs at all).
With comp + sup-phys, it can't.
Why? If we assume sup+phys, then some changes in the physical
system on which the dream supervenes certainly will lead to changes
in the dream.
I don't think so. Remember that we suppose comp (and sup-phys). So
we already agree that we can change the physical implementation if
it runs the computation at the correct level. So, we can change the
physical implementation as we wish, below the substitution level
without changing the first person private consciousness.
I think I wasn't clear here. I didn't mean changes in the particular
physical system consciousness is supervening on -- of course by comp
that doesn't matter. I meant that, assuming sup-phys on physical
system X, there must exist some changes in X which lead to changes
Bruno isolates the film and thus reaches his apparent
contradictions. But this is not a permissible move.
I think that the term "film" could have different meaning in french
and english. But the film here means the projection of the pellicle
on the glass/crystal medium. This one is never broken. It is a
process which takes time, and occur in some place.
Not only is the definition of supervenience violated, but his
principle of irrelevant subparts is violated as well – for the
optical graph is not irrelevant for the execution of Alice’s
Of course, but once we put away the nodes, the physical activity
corresponding to the computation are not changed. The optical graph
becomes irrelevant for the physical activity on which Alice's
consciousness is supposed to supervene, by comp+sup-phys.
This is where my problem lies. Of course the physical activity of
the system is changed when you (invalidly) remove the optical graph
from the system. It is far from irrelevant. For example, what
mechanism causes the light to triggers the lasers? There must be
some "internal" mechanisms at work as well. The nodes aren't
"connected" to one another, but it matters whether or not the
recording is being projected on an optical graph, vs. a concrete
wall, vs. movie screen....
Why? The relevant physical activity is the same.
Obviously I agree with you (the projection of the film does not
instantiate consciousness). The point is that if comp and sup-phys
are maintained, and if 323 is correct, then there is nothing
different from projecting the film on the glass crystal with the
boolean laser graph removed and a wall.
I have no problem with 323. My argument is that consciousness never
supervenes on the film/movie/recording.
I agree with that. If only because there are no more any computation
done "in time and space" (the original abstract computation does not
disappear, of course, so with comp, we will have to attach
consciousness to it, and not to its particular "concrete
So there is something different between projecting the film on the
glass crystal, and the wall. The relevant physical activity, in the
two cases (glass/crystal vs wall), is not the same. In the first
case (and not the second) the light interacts with the crystal
medium and triggers the lasers. How can you argue that this
interaction is irrelevant and can be removed?
Because that special activity has nothing to do with the original
computation. If it were, I could not have said yes to the doctor at
the start. Once the boolean graph is remove, we just get a special
weird screen. And the absurdity is still there: there are no
computation done when we project on that weird sort of screen.
Let me restate my concern: Consciousness supervenes on the optical
graph+the recording, even when the nodes are completely
disconnected. It is true that "most of the work" is being done by
the recording, but not all of the work. The optical graph still
matters, and the "physical activity" of the system is not solely
provided by the recording, as it still depends on how the projected
light interacts (physically) with the glass/crystal surface.
But this is no more relevant in term of the computation, which is
supposed to be a copy of the brain processing at the right level or
There is a point in the argument at which you ignore the glass/
crystal system and focus solely on the movie/recording, claiming
that Alice's consciousness supervenes on the movie/recording. But
this is false. At no point does Alice's consciousness supervene on
the recording, not even when the nodes are completely disconnected.
Yes. That's why it is a reductio ad absurdum.
Its a reductio ad absurdum only if you artificially ignore the
interaction between the projected light and the crystal medium and
lasers. Because consciousness supervenes on crystal/glass/nodes
+film, it is not meaningful to make this move. Consciousness changes
do not imply film changes (even though the converse may well be
true). You have isolated a subsystem from the machine, mistaken this
subsystem for being sufficient for consciousness to supervene on --
little wonder an absurd conclusion follows!
I could because all this is supposed to be done below the substitution
I am trying to think of an analogy to another system which would
make my argument clearer (and in the process learning how tricky the
concept of supervenience can be).
Actually, I do the same. I search a system where I can make it clearer
why the idiosyncrasies of the movie-graph are simpler to evacuate.
But in the present case, it seems rather obvious to me that the
absurdity is already there, before replacing the glass+smoke by a
usual screen. There is already no more computations, we can already
use the stroboscopic argument to make that absurd.
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