On 22 Dec 2011, at 23:27, Joseph Knight wrote:
Hello everyone and everything,
I have pompously made my own thread for this, even though we have
another MGA thread going, because the other one (sigh, I created
that one too) seems to have split into at least two different
discussions, both of which are largely different from what I have to
say, so I want to avoid confusion.
Here, I will explain why I believe the Movie Graph Argument (MGA) is
invalid. I will start with an exegesis of my understanding of the
MGA, so that Bruno or others can point out if I have failed to
understand some important aspect of the argument. Then I will
explain what is wrong. I believe confusion regarding the concept of
supervenience has been responsible for some invalid reasoning. (At
the end I will also explain why I find Maudlin’s thought experiment
to be inconclusive.)
As it is explained here, here, and here, the MGA consists of three
parts. Throughout the argument we are assuming comp and materialism
to be true.
In Part 1, Bruno asks us to consider Alice. Alice is a conscious
being. Alice already has an artificial brain, to make the reasoning
easier. We are assuming here (with no loss of generality) that,
under normal circumstances, Alice’s consciousness supervenes on this
artificial brain. Alice is taking a math exam, when at a certain
moment one of the logic gates A fails to signal logic gate B. At
this precise moment, however, a particle arrives from some far-away
cosmic explosion and triggers gate B anyway. Assuming comp we
(pretty safely) conclude that Alice’s consciousness is unaffected by
this change in causation – after all, the computation has been
performed. Moreover, we can assume any number – thousands, say –
of such failures in Alice’s brain, with lucky cosmic rays arriving
to save the day. Indeed, all of Alice’s neurons could be disabled,
with cosmic rays triggering each one in just the right way so as to
maintain her consciousness. Bruno (wisely, in my opinion) likes to
end the steps of his argument with questions. At the end of MGA 1,
he asks, is Alice a zombie during the exam? We are really forced to
say that she isn’t, because of our comp assumption. So Alice is just
as conscious as she was before her brain started short-circuiting.
In Part 2, we build on the ideas of part 1 but without cosmic rays.
Bruno assumes for the sake of argument, again with no loss of
generality, that Alice is dreaming and that her brain has no inputs
or outputs. Now, Alice’s (artificial) brain is a 3D Boolean graph
(network being the more common term), which, with a few wiring
changes, can be deformed into a 2D Boolean graph and thus laid out
on a plane. Next Bruno asks us to imagine us instantiating Alice’s
2D graph-brain as a system of laser beams connecting nodes (instead
of wires, and with destructive interference helping out with NOR,
etc.), all in some special material. The graph is placed between two
glass plates, and a special crystalline material is sandwiched
between the plates which has the property that if a beam of light
connects two nodes, the “right” laser is triggered to signal the
right node at that location. (Unlikely, but conceivable and valid,
which is all we intrepid philosophers need anyway!)
So Alice is dreaming (conscious), with her dream supervening on the
2D optical graph, and with no malfunctions. Suppose we film these
computations with a video camera. Now suppose Alice begins to dream
the same dream again but after a while, Alice’s 2D graph begins
making mistakes, i.e. not sending signals where signals should be
sent. But if we, in all our humanitarian goodwill, project the
(perfectly aligned) film onto the optical material/graph, we can
preserve Alice’s consciousness completely. If it worked with the
cosmic rays from part 1, it works here too, by comp. Alice remains
Finally, in Part 3, we reach some apparent contradictions. Bruno
introduces a (safe) principle at the beginning, namely that if some
part of a system is not used for the functioning of that system in
some given task, then it can be removed and still complete that
task. If Alice doesn’t use neuron X to complete her math exam, we
can remove neuron X during the exam and she will perform the same
way. I will call this the principle of irrelevant subsystems.
So, back to Alice and the filmed 2D optical graph. We are apparently
forced, at this point, to conclude that Alice’s consciousness
supervenes on the projection of the movie. In Bruno’s words:
Is it necessary that someone look at that movie? Certainly not. No
more than it is needed that someone is look at your reconstitution
in Moscow for you to be conscious in Moscow after a teleportation.
All right? (with MEC [comp] assumed of course). Is it necessary to
have a screen? Well, the range of activity here is just one
dynamical description of one computation. Suppose we make a hole in
the screen. What goes in and out of that hole is exactly the same,
with the hole and without the hole. For that unique activity, the
hole in the screen is functionally equivalent to the subgraph which
the hole removed. Clearly we can make a hole as large as the screen,
so no need for a screen. But this reasoning goes through if we make
the hole in the film itself. Reconsider the image on the screen:
with a hole in the film itself, you get a "hole" in the movie, but
everything which enters and go out of the hole remains the same, for
that (unique) range of activity. The "hole" has trivially the same
functionality than the subgraph functionality whose special behavior
was described by the film. And this is true for any subparts, so we
can remove the entire film itself.
In short, we are forced to accept that Alice’s consciousness
supervenes on a vacuum. Of course, we don’t really have to go this
far, because already we have Alice’s consciousness supervening on a
film which performs no meaningful computations, i.e., is “inert” –
an absurdity. There are several other ways of stating this part of
the argument, none of which changes the result, and if anyone is
confused I recommend reading the links above. But otherwise this
concludes the MGA. It has apparently been shown that there is a
contradiction between computationalism and materialism.
I said initially that my concern was with the treatment of the
supervenience concept. This term is often thrown around on the
Everything list. It is an important concept. What is supervenience?
If system X supervenes on system Y, then there cannot be a change in
X without a change in Y. Note that there can be a change in Y
without a change in X. In other words, IF change in X, THEN change
in Y. (Supervenience is silent on issues of entailment/causation,
Bruno’s (and Maudlin’s, for that matter) argument hinges on the
issue of supervenience, specifically: on what does consciousness
supervene? If it can be shown that, assuming computationalism and
materialism, that consciousness supervenes on a vacuum, or on a
“causally inert” object, then we have shown something important. But
it matters how we get there.
In Part 1, when the neurons (nodes) in Alice’s brain are all
malfunctioning, she is saved by the cosmic rays. The rays trigger
the neurons precisely when and where they must be in order to
instantiate Alice’s consciousness. But Alice’s consciousness does
not supervene on the cosmic rays. Nor does her consciousness
supervene on her damaged brain. Her consciousness supervenes on the
system (brain + cosmic rays).
There can be a change in consciousness without a change in the
cosmic ray pattern: Alice’s consciousness might change, say, if a
neuron (node) from the brain is removed, preventing the
corresponding cosmic ray from triggering it and leading to an
alteration in her consciousness. Likewise, there can be a change in
consciousness without a change in her (damaged) brain, say, if the
cosmic shower had occurred in a slightly different way.
Bruno’s argument is a conflation of necessary and sufficient
conditions, as well as a conflation of supervenience and entailment.
The cosmic rays are necessary to execute Alice’s consciousness, but
not sufficient. It would be an invalid move to remove her brain
(however faulty it may be) and focus exclusively on the cosmic
particles as a cause of her consciousness. By this fallacious
reasoning, we might conclude that because the left hemisphere of
someone’s brain is necessary for their consciousness, it is also
sufficient. It is the confusion of “IF change in (relevant) cosmic
rays, THEN change in consciousness” with “IF change in
consciousness, THEN change in (relevant) cosmic rays”.
OK. I use this.
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.
The same problem arises in Part 2. Bruno claims that we are forced
to accept that Alice’s consciousness supervenes on the film.
But this is not correct – Alice’s consciousness supervenes on (film
+ optical graph),
for the same reasons as above. There can be a change in
consciousness without a change in the film: suppose I destroy a
portion of the glass/crystal medium, hence some of the nodes in the
graph. The film is unchanged,
? the film is changed, in this case.
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.
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.
Bruno isolates the film and thus reaches his apparent
contradictions. But this is not a permissible move.
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.
We certainly cannot remove it and expect Alice to remain conscious,
any more than we can remove the artificial brain of Part 1 and
expect Alice to pass her exam – in both cases, we are left merely
with an interesting light show. In conclusion, we are not forced to
conclude that Alice’s consciousness supervenes on a vacuum, or on an
inert film reel.
The film is never inert. That is why the stroboscopic argument work.
I think you have interopret the word "film" differently. A film is a
dynamical event taking some times and involving projection. It is
Please discuss, and tell me if I myself have made any errors.
Regarding Maudlin’s argument: Russell has recently stated that
Maudlin’s argument doesn’t work in a multiverse, and that
consciousness is thus a multiverse phenomenon. I disagree for the
same reason that Bruno disagrees: the region of the multiverse on
which consciousness supervenes can just be Turing emulated in a huge
water/trough/block computer, and Maudlin’s argument can be
reapplied. I realize that this could lead to an infinite regress…hmm…
Yes, that is why, in fine Russell's move leads to multi-multi- ...
multi verse. To keep the existence of primary physical stuff
necessary, is last addition of multi playng his role, he has to make
it non Turing emulable. The UD dovetails on all multi-^alpha universes
with alpha constructive ordinal. Russell should impose a Multi-^alpha
universe with alpha not being constructive, then the MGA can no more
be applied, but then comp is also false.
I guess you meant "It is not patently absurd that a constant program/
algorithm can be conscious"?
Well, I find this patently absurd. To have consciousness ,qua
computatio, you need complex self-referential computing.
The real reason I don’t find Tim Maudlin’s argument convincing is
largely due to recent comments made by Brent. It is not patently
absurd that a constant program/algorithm cannot be conscious – it is
for intelligence, however.
For all I know, this has not been decided either way.
But it follows from the computationalist hypothesis.
Maybe in the future a “consciousness theorem” will decide the matter
one way or another, but until then I don’t think that Maudlin has
demonstrated a contradiction, just an irritating fact. (It seems to
me, and is worth noting, that if the principle of irrelevant
subparts is true, then we are forced to conclude that a constant
program/algorithm can be conscious, rendering Maudlin’s paradox,
well, not a paradox.) Intelligence is tricky, as it has the notion
of counterfactual bound up within its definition. But there is no a
priori reason to assume this to be the case for consciousness.
Even when you accept an artificial digital brain, and believe that you
survive because your computation is running correctly by that digital
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