Bruno Marchal writes:
>> Bruno: If consciousness supervenes on all physical processes a case
>> can be made that matter could be relevant for consciousness. (I see
>> Peter Jones makes a similar remark).
> Stathis: Except that you could say the same for the Maudlin example,
> in which it is shown that conscious can differ in two objects which do
> not differ in physical activity: it does not strictly show that
> physical activity (or more generally, matter) is unnecessary, just
> that the usual definition of supervenience does not apply.
OK, I guess that by "usual supervenience" you mean "physical
supervenience". Both Maudlin and the movie graph show that the comp hyp
is incompatible with usual (physical) supervenience. We both show (~
comp OR ~ physical supervenience). This is equivalent with (comp -> ~
physical supervenience) or with (physical supervenience -> ~ comp).
Now I take comp, and I prove more (the UDA + Movie graph) gives more
information than just the movie graph or Maudlin, and the acomp
shows more and less. More in the sense that it gives the precise logic
of comp-physical proposition; less because without much remaining work
it gives only that. But the puzzle pieces fit enough together to expect
some quantum computing provable to appear in the neighborhood of any
The usual definition of supervenience is that if A properties supervene on B
properties, the A properties cannot differ without the B properties also differing.
So if it can be shown that the one instant of B properties (the one physical state)
can be associated with more than one instant of A properties (two or more distinct
conscious states), then this wrecks the physical supervenience thesis. However, it
does not strictly show that *no* physical state at all is required for consciousness
to occur; I agree that this is a neater and more elegant conclusion but it doesn't follow.
> You take comp and supervenience as two separate theories, but I would
> bet that most computationalists take them as a package deal.
Of course. But they are wrong. That package deal is made of sand. That
is my point. Comp and physical supervenience is a bit little "molecular
biology" + vitalism.
The point of the UDA in 8 steps (that is UDA including the
movie-graph/maudlin point) is really that nobody can be serious by
keeping both comp and physical supervenience. But physical
supervenience is obviously an invention of materialist (monist or
If we keep comp you can easily understand that we have to go back on
computational supervenience, and then we have to explain the origin of
the physical laws from that.
I agree. I was just pointing out that computationalists are generally fond of
computers, and their raison d'etre would be challenged if the computers were
shown to be unnecessary.
>> > I wonder if we are talking about the same thing, because it doesn't
>> > seem to me that an empirical proof is needed to show that any
>> physical > process could be seen as implementing any computation.
>> This is not obvious at all. You need both empiry + a physical theory
>> about that empiry, just to say that there is a physical process
>> implementing if only one computation (to say nothing about all
> All you need is one physical process.
That is enough for my point.
> If consciousness is in no way dependent on the details of this
> physical process, then the actual physics is irrelevant.
What does that means? If physical supervenience is correct
consciousness has to be described by a non turing emulable *physical
process* whatever details are needed or not, a part of it have to
include an infinity of details (or it will be computationalist).
But physical supervenience isn't correct if comp [i.e. comp excluding the
physical supervenience part] is correct, as we are both arguing. This means
that consciousness is not dependent on any particular physical properties.
> Do you see how, aside from one small detail, this is equivalent to
> saying that consciousness is not dependent on any physical process at
I don't see this (but I see that this is going in the direction I argue
it should go).
> It doesn't matter if the machine loops, because the one physical state
> can map to many different computational states.
I can only *imagine* this, and this only together with some physical
assumption. Remember that one of my goal is to explain what a "physical
state" can possibly be. As you know I do not assume physics. I do not
assume any physics.
> Semantics is arbitrary.
Hmmm... here I see what you mean, but I disagree. You consider some
physical state (a fuzzy thing imo) and then *you* consider all the
semantics, which *you* interpret as any or many computational states.
Perhaps we should go back on the basic assumption.
Indeed, I provide the semantics, in language as in computer science. A string
of characters has no meaning unless an observer gives it meaning. However,
what of the special case where a computation is conscious, providing its own
observer even if all inputs/outputs are destroyed and there is no-one left who
is able to understand the details of its design?
> But if you consider a physical computer the actual states
> corresponding to the steps of the computation can be arbitrary. They
> will be ordered in a certain consistent way, so we can utilise the
> machine, but that is just a practical requirement. The natural number
> 3 does not have to be written as "3" nor even as "III"; it could be
> written as "II" on a Wednesday, "IIII" if the moon is full and "I" the
> rest of the time. This has no effect on the platonic object 3, but it
> does affect our ability to communicate and do arithmetic unless we
> keep track of the notation. Similarly with a computation, we need to
> be aware of the meaning of the states on a physical computer in order
> to use it, but our awareness of the computer semantics does not
> "create" the computation or imbue it with consciousness (if
> computations can be conscious) any more than our awareness of
> mathematical notation creates the number 3.
The computational states just need to be *relatively* coherent. I have
no idea what you mean by a "physical computer" for the reason that the
term "physical" denotes different things relatively to the assumption
By a physical world I mean just what appears to me to be a physical world.
This is a starting point, even if you later conclude beginning with this and
some other observations that there is no separate physical reality.
> Why can't the black page contain everything that can possibly be
> written, i.e. it can be a superposition of an infinite number of pages
> with an infinite amount of ink?
You mean a quantum superposition? (then with comp such a superposition
really describes an infinity of immaterial computational histories in
which each page contains a finite amount of ink. Well it is rather
similar with the quantum mechanical superposition).
The only sense in which (both with quantum field theory AND with the
comp-physics) I can accept an infinite information on a black page is
related to renormalization problem, spurious infinite energies ....
You're being too clever for me. I simply meant that a page on which a
large number of people had written (perhaps a digital page with digital
ink, so that it doesn't get saturated) would appear black. Once it is black,
more writing would not change its appearance, so a page with a million
superimposed English texts would look the same as a page with every
possible text in every possible language all superimposed.
But then why to assume a physical world with all those infinities when
comp forces us to deal with already enough infinities?
You loss me I'm afraid. Are you trying to save both comp AND the
No: one or other is flawed. But the evidence suggests that it is still possible
that *some* physical reality is needed for consciousness to occur, given
comp, even though the supervenience relationship does not apply. This is
a kludge; better to say either that consciousness is dependent on matter in
some well-behaved way like every other physical phenomenon, or completely
independent of matter - but I can't quite see how to do this.
We have not yet derive the whole of physics
from comp, but we can already expect the "mind-matter" mapping to be
something quite complex. For me it is obvious that to a mind state
there will be an infinity of "computational states and histories" going
through that mind state. The reverse is harder because we are unable
(assuming comp) to singularize a "comp-physical states". Physical
states *are* already first person plural (inter-subjective) appearances
emerging from the gluing and overlapping of infinities of computations
(and thus immaterial(*)). Unless I am wrong, standard computationalism
is flawed, like both the monist and dualist doctrine of materialism are
It would be wrong to say that comp makes materialism refutated, but for
a similar reason that it is wrong to say that bilogy has proves that
vitalism is refutated. But biology has made vitalism
explanation-useless, and computationalism makes materialism explantion
Of course it remains the possibility that comp is incorrect. If comp is
true, we have to live with that possibility forever.
OK, I agre with that.
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