On 1/27/2011 10:23 AM, Bruno Marchal wrote:
On 25 Jan 2011, at 15:47, Stephen Paul King wrote:
The supervenience thesis is separate from the Turing thesis and
Mauldin does a good job in distinguishing them.
Just to be clear, what Maudlin call "supervenience thesis" is what I
called "physical supervenience thesis", to distinguish it from the
computationalist supervenience thesis.
The computationalist supervenience thesis is basically what remains
when we keep comp, and understand that the Phys. Sup. thesis has to go
away in the comp frame.
The problem that I see is in the properties of physicality that are
assumed in Mauldin’s argument. It is one thing to not be dependent on
what particular physical structure a computation can be run on
(assuming a realistic supervenience), it is another thing entirely to
say that a Turing machine can be “run” without the existence of any
physical hardware at all.
Well, in the branch ~MEC v ~MAT, Maudlin seems to prefer MAT, so he
seems with you on this, I think.
I am trying to make this distinction and trying to fix this problem
that I found in the supervenience thesis within Mauldin’s argument.
He does point out that there are contrafactuals that must have some
physical instantiation. We see this on page 411 where he wrote:
“The only physical requirement that a system must met in order to
instantiate a certain machine table are that (1) there must be at
least as many physically distinguishable states of the system as
there are machine states in the table, (2) the system must be capable
of reacting to and changing the state of the tape, and (3) there must
be enough physical structure to support the subjunctive connections
specified in the table.”
It is in the subjunctive connections that we see the
contrafactuals expressed. If one’s model of physical reality does not
allow for the necessary subjunctive connections to be implemented
then the supervenience thesis would fail independent of the Turing
thesis.
OK.
My point is that we need to be careful about what exactly do we mean
by “causally inactive piece of matter”. If there is material present
within a physical system that does not affect the 3 requirements
above then surely we can agree with Mauldin’s claim, but if there is
a problem with the faithfulness of the model of what physicality
involves, then this must be fixed if possible. This is why I say that
there is a bit of a straw man in his argument.
Maudlin should have said: "causally inactive piece of matter
*relevant* for the computation. This is what I did, and it makes the
argument independent of the counterfactual re-instantiation. The
movie-graph is simpler with that respect. But this can lead to some
ambiguity too.
Mathematical structures do not “do” anything, they merely exist,
if at all! We can use verbs to describe relations between nouns but
that does not change the fact that nouns are nouns and not verbs. The
movie graph is a neat trick in that is abstracts out the active
process of organizing the information content of the individual
frames and the order of their placement in the graph, but that some
process had to be involved to perform the computation of the content
and ordering cannot be removed, it is only pushed out of the field of
view. This is why I argue that we cannot ignore the computational
complexity problem that exist in any situation where we are
considering a optimal configuration that is somehow selected from
some set or ensemble.
I don't see how this would change anything in the argument, unless you
presuppose consciousness is not locally Turing emulable, to start with.
What does "locally" mean in this context? I doubt that consciousness is
strictly local in the physical sense; it requires and world to interact
with.
Brent
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