But Physicalism is incompatible with Computationalism.

From: Bruno Marchal <marchal.domain.name.hidden>
Date: Mon, 27 Jun 2005 20:10:51 +0200

Hi Brian,

May I quote you?

You (Brian Holtz) wrote at:


> ...
> Note that, while the Life thought experiment depends on mind being
> computable, the logically possible universe (LPU) thought experiment
> only assumes that our universe could be considered as a logically
> possible sequence of (not necessarily finitely describable)
> universe-states.  The LPU hypothesis also depends on the thesis that
> physicalism is right and that qualia and consciousness are
> epiphenomena. The LPU hypothesis is of course unparsimonious (sort of
> like the many-worlds interpretation of quantum theory), but parsimony
> is perhaps inconsistent with *any* answer to the Big Why.  

I'm afraid Physicalism is incompatible with Computationalism.

  Marchal, B. (1988). Informatique théorique et philosophie de l'esprit.
In Actes du 3ème colloque international de l'ARC, pages 193-227,

  Maudlin, T. (1989). Computation and Consciousness. The Journal of
Philosophy, pages 407-432.

With the computationalist assumption (comp), physics *must* be derived
from a general measure definable by self-referential machines and
defined on the collection of their "maximal consistent extensions".
See my url for references. Sorry for being short. Note that this made
comp empirically testable.

> The idea that the world might be a dream is of course not new.  But I
> don't recall ever hearing that the world might be just a logically
> possible dream for which no dreamer exists.

Sure. (But this does not make the dreamer "material" in any stronger
sense that, if the dreamer observes itself, he will first discover some
third person description of himself;(hopefully manageable with respect
to its most probable history) and that by looking closely he will
discover the "fuzziness" of "slumberland" (say) and its mathematics.

Do you know the Godel-Lob-Solovay provability/consistency modal logics
G and G*?
They make possible to ask the machine about those questions (including
the measure on the consistent extensions). Note that the machine
remains mute on all deep questions (like "is there a world?"), but then
G* can explain why. The difference between provable (G) and true (G*)
allow to distinguish communicable knowledge (I guess quanta) and non
communicable knowledge (I guess qualia).
For knowledge (and "first person notion") I use Theaetetus' definitions

Smullyan's "Forever Undecided" is a recreative introduction to G. I
guess you know Godel, but the basic fundamental papers are really:

  Gödel, K. (1931). Über formal unentscheidbare sätze der principia
mathematica und verwandter systeme i. Monatsh., Math. Phys.,
38:173-198. Traduction américaine dans Davis 1965, page 5+.

  Löb, M. H. (1955). Solution of a problem of Leon Henkin. Journal of
Symbolic Logic, 20:115-118.

  Solovay, R. M. (1976). Provability Interpretation of Modal Logic.
Israel Journal of Mathematics, 25:287-304.

For the machine's interview you could read my currently last paper (and
the errata perhaps):


Received on Mon Jun 27 2005 - 14:14:37 PDT

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