On 24 Mar 2015, at 06:05, Bruce Kellett wrote:
Russell Standish wrote:
On Tue, Mar 24, 2015 at 02:17:40PM +1100, Bruce Kellett wrote:
If you take the block universe model seriously then we are nothing
more than conscious recordings!
Fair point!
I don't know what MGA stands for, or what it means, so I can't
comment on that.
Ha - it's in the title of this thread!
I can enter a thread without knowing what the title means!
It's Bruno Marchal's "Movie Graph Argument" (I would probably have
translated it as "Filmed Graph Argument", but MGA seems to have
stuck. Also known as "Step 8" of the UDA. It purports to show that
materialism and mechanism (aka computationalism) are fundamentally
incompatible. It is closely related to Tim Maudlin's Olimpia
argument.
I wrote a preprint which is available from
http://www.hpcoders.com.au/blog/?p=73 if you're interested in knowing
a bit more, or at least is a source of references, if you think I'm
too turgid.
Thanks. I downloaded your short paper. I can see why the extended
argument on the everything list have failed to move me. The gaps in
your argument are rather evident. You state that if computationalism
is valid, then all possible experiences are instantiated by the
dovetailer. But nowhere do you define what is a possible experience.
It seems to depend on the fact that the dovetailer runs all possible
computer programs. In that case, it runs a program in which in the
next instance I become lighter than air and can float around the room!
In fact, I can write computer programs where the laws of physics
change from instant to instant. Why do we not experience these things?
Excellent. That *is* the question. But the "everything" of comp is not
just noise, it is the sigma_1 complete part of the arithmetical
reality, and it get structured when apprehended by the machines or
number themselves, from inside.
All modal realism (or everything theories) can suffer of an inflation
of realities threatening the possibility of prevision and
theorization. But with computationalism we have computer science to
make the question precise and get some clues thanks to the vast
accomplishment in that era (not well known unfortunately).
ISTM that you are simply assuming that 'possible' means 'possible
within the bounds of the physical laws that govern the world we live
in.' I think you might see the problem with such an assumption.
At the basic meta-level, possible will mean that a mental state is
accessible by the UD, or exist in arithmetic.
We do have (thanks to Church's thesis) a precise definition of digital
computation, with reasonable equivalence classes of behaviors. We
don't have this for analog or physical computation notions, which have
no (serious) Church's thesis.
Church's thesis (also called Church-Turing thesis, or CT) is a very
strong thesis. I can prove the incompletess of all theories about
digital machines in one diagonalization (well two, as you make always
two diagonlaization technically). Judson Webb, and Kleene wrote a
papers on that.
Church missed Church's thesis. It is Kleene who created the 'Church's
thesis", and understood the best, with Emil Post, Martin Davis, and
some others, its alluring consequences.
Computability can be defined in term of provability, and indeed
sigma_1 complete provability. Computability is a tiny part of the
arithmetical truth, and living souls supervene on the border between
computability and non computability, (where they can hesitate notably
between security and freedom).
I have to go.
Will comment very plausibly other MGA posts later. Sometimes some
people tend to put more in MGA than there is, like other people put
more in "arithmetical realism" than there is.
There are two bombs: the universal machine, the fact that some
universal machine knows the price of being universal, and the
empirical bomb: the quantum universal machine. It is too early to
decide if the quantum universal machine (which does not violate Church
thesis) confirms of refute computationalism.
Bruno
Bruce
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