On 12 Dec 2013, at 06:30, Jesse Mazer wrote:
Thanks Bruno. As I understand it step 8's movie-graph argument is
making a point similar to the "implementation problem" chalmers
discusses in the paper at http://consc.net/papers/rock.html --
basically the problem is that there seems to be no good way to
decide whether a given physical system "implements" a given abstract
computation (Chalmers proposes his own rules for deciding this, but
they seem a bit ad hoc to me, depending on dividing a physical
system into distinct spatial regions).
Hmm... I am not sure I agree with this. "rock" is a non well defined
notion. I think we have already discuss this, when I told you it is
more related with Maudlin than with the Chalmers-Putnam-Mallah
implementation problem.
I guess we will soon or later come back to step 8. It only dimish the
use of Occam to get the reversal physics/arithmetic (or physics/
theology).
Anyway, even though I tend to agree with you about rejecting the
idea of what you call "real ontological primitive matter", it seems
to me this argument goes too far, because it could easily be
modified into an argument that there's no good way to decide whether
one abstract computation (including the universal dovetailer)
"implements" another computation as some sort of subroutine of the
first one.
Consider your movie-graph experiment, where you have a lab with a
computer made of optical gates. What if, instead of a real physical
lab, we imagine a program A that is running an incredibly complex
simulation of the same sort of lab, down to the level of individual
atoms and photons and such? And within this simulated lab is the
same type of computer made of simulated optical gates, which are
supposed to run some simpler program B (we could imagine B is some
very simple program, say a 1D cellular automaton consisting of a
small number of cells, or we could imagine B as something
complicated enough to include a conscious observer, like a large
simulated neural network, but still much simpler than the atom-level
simulation of the lab). If the notion of one program "implementing"
another as a subroutine has any meaning, then shouldn't this be a
case where program A implements program B?
Yes. As long as there is an (perhaps unknown) universal numbers
relating logically the states, we can say that there is a computation.
A computation is really equivalent with the giving of
1) a universal number or system (that is: a number)
2) a data (a number for the program run by the universal number above)
3) two numbers (the beginning and end of the computation. The end does
not need to be a stopping state).
This is a finite object, and can be codes by a number.
But if the simulated lab has a simulated movie projector of the type
you describe, then simulated experimenters in the lab could run the
experiment you describe of knocking out logic gates and replacing
them with a movie of the same gates projected from above, which
provide the needed triggers to the remaining light-sensitive gates.
If more and more gates are knocked out until all that's left is a
simulated movie being projected on an empty table, is there still
any meaningful sense that program A is implementing program B?
There is no more sense. That would be a confusion between a
description of a computation, and a computation. To have a
computation, you need the exact logical relationhip between the state.
The filmed movie abstracts from them. It only points to the fact that
some computation exist, but is not a computation.
Personally, I lean towards the idea that since any running of a
Turing machine can be represented as a set of logically
interconnected propositions in an axiomatic system, to say that
program A "implements" program B can mean that you can map some
subset of the propositions about program A to all the propositions
about program B, such that all the same logical relationships
between the propositions still apply.
That seems correct, yes. The computation is in the logical
relationship between the numbers, states, etc. Not in their local
implementation, which change the measure, and not at all in the
descriptions of computation, like the filmed graph, which will not
change the measure, unless they are used for some further
reimplementations (which would again change the measure).
I think we agree on this. OK?
And if the physical world follows universal physical laws, then the
set of all physical truths about events in spacetime and the causal
relationships between them should in principle be representable as a
huge set of propositions about events, and propositions about
universal laws, with logical relationships between them--in that
case "physical implementation" could be defined in exactly the same
way as I suggest defining program A's implementation of program B
above. This is the idea I discussed with you a few years ago in the
post at http://www.mail-archive.com/[email protected]/msg16244.html
and some of the follow-ups--I used the word "causal structure"
there for this notion of isomorphisms in relations between
propositions, although I think "logical structure" might be better
since this could apply to collections of propositions in any
axiomatic system, including arithmetic, where we don't normally
think of the relationships between propositions as "causal" ones.
I think we agreed, including on the fact that Chalmers does not bear
on this in his rock paper.
Anyway, I don't know what *is* a rock.
Bruno
Jesse
On Tue, Dec 10, 2013 at 4:06 AM, Bruno Marchal <[email protected]>
wrote:
On 09 Dec 2013, at 23:03, Jesse Mazer wrote:
I don't have institutional access but I was able to read it online,
That was what Elsevier (Santa) promised.
though not to download it as a PDF
Pfftt.... Santa looks like being a bit shabby those days ...
(I just copy-and-pasted all the text for future reference instead).
It's great to see each step of the argument laid out in greater
detail than I've seen on the list (admittedly I don't consistently
read all the posts here)--I still have doubts about step 8, the
film-graph argument, hopefully will have time to write up my
response soon.
Thanks. We can come back on step 8 anytime. It shows that any
supplementary assumptions we could add to (Robinson, no induction
axioms) Arithmetic will not change anything about the belief we can
have on matter, making primitive matter into ether or phlogiston.
Step 8 just reduces the amount of occam razor that we should need in
step 7, in case we want to stop the argument at that step.
Step 8 is not so useful in this list, because most people here are
'everythingers', and so find quite doubtful the idea that we would
live in a unique little physical universe, which is the move you can
still do at step 7 to save the idea of real ontological primitive
matter (but who needs that?). Step 8 makes primitive matter into a
god-of-the-gap explaining nothing, not even the appearance of matter
(unless you make it non Turing emulable and playing a role in the
brain, but then comp get wrong).
UDA 1-7 is purely deductive, but step 8 is supposed to make the link
with 'reality', and so we need some use of occam razor.
Bruno
Jesse
On Mon, Dec 9, 2013 at 3:32 PM, meekerdb <[email protected]>
wrote:
Excellent, Bruno! I'm very glad for you - and for the wider
audience that will now read your ideas. However I notice Santa
only delivers if you have institutional access. I do. But others
on the list may not.
Brent
On 12/9/2013 2:48 AM, Bruno Marchal wrote:
Hi,
Santa Klaus exists, and by its magical power seems to have made my
last paper ("The computationalist reformulation of the mind-body
problem") in Progress in biophysics and molecular biology,
*freely* available; here:
http://elsarticle.com/18AF6PI
This offer seems to last up to the 31 january (Santa Klaus seems
to have only a *finite* amount of magic).
So please download, comment, ask questions, etc. it contains
(again!) the two main parts (UDA, AUDA), but also answers to many
reviewers' questions in an appendix.
I send this also on FOAR, for Gary :) (apology for the doubletons)
Bruno
http://iridia.ulb.ac.be/~marchal/
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