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>From: chalmers@bronze.ucs.indiana.edu (David Chalmers)
Subject: Quantum theory and consciousness (was Pansychism)
Message-ID: <1992Feb16.220955.18106@bronze.ucs.indiana.edu>
Organization: Indiana University
References: <jbaxter.697880577@adelphi>
Date: Sun, 16 Feb 92 22:09:55 GMT
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[Crossposted to sci.physics for obvious reasons.]

In article <jbaxter.697880577@adelphi> jbaxter@physics.adelaide.edu.au (Jon Baxter) writes:

>Ok, what I meant was that materialism as it currently stands seems to
>provide no explanation for the existence of qualia, hence a materialist
>would hold that such a universe is indeed possible. I believe that
>materialism needs modification, and not just trivial "epiphenomenal"
>type modifications either; such as: "qualia just *are* the result of
>information processing, ok? Don't ask me why". The universe is just not
>that simple. A lot more thought about some of the mysteries in physics should
>lead us to a far richer and more uniform description of the universe, a
>description that doesn't need anything so ugly as dualism to explain qualia.

I don't know that dualism has to be ugly.  A correct theory of qualia
wil probably show how they are tightly enmeshed with other fundamental
properties (you don't get much more fundamental than information
processing).  But it's still dualism, as long as it's the case that the
existence of qualia forces one to postulate extra facts about the
universe, that one wouldn't be forced to postulate on the basis of
physics alone (that's more or less a definition of dualism).  We just
have to hope that the theory is as simple as possible, i.e. that the
nomological danglers don't dangle too far.  A view of information as
something that has two aspects, a physical and a qualitative aspect,
would seem to be a stab in that direction.

Of course it's just possible that thinking really hard about physical
problems alone would force one to a view which led to the existence of
qualia as a logical implication, but I personally don't see any
reason to believe that.  An objective physics could probably get by
without mentioning or implying qualia.  (Whether we, in our limited
status as conscious observers, can actually come up with a complete
objective physics, is a different question.)

>I have one problem with this viewpoint, namely that there is no canonical
>set of eigenstates within the big superposition. A set of eigenstates
>is simply an arbitrary choice of basis vectors in terms of which
>we express the universe's total state. We usually choose these basis states
>to be eigenstates of relevant operators (e.g energy, position, etc) but
>by doing so we automatically force other operator's eigenstates to be
>superpositions of these basis states. So if consciousness is non-superposed
>with respect to one set of operators, it will definitely be superposed with
>respect to another.  Why then, do "I" only ever experience the non-superposed
>part. Seems to be an astonishing coincidence to me.

This is where the arguments on personal identity (e.g. by Parfit) that
I mentioned come in.  If you accept these arguments (and they're very
good) there are no "deep facts" linking your conscious state now to
conscious states in the past and future; there is just memory, and other
psychological relations.  So there's no fact of the matter about what "I"
will experience in the future, given that there are lots of minds about
the place.  In particular, your question in the penultimate sentence above
is more or less meaningless, except insofar as it's asking "why is it that
I am not now in a superposed state, and I don't have any memories of
superposed states?"  The answer to that is fairly straightforward -- your
conscious state just *is* that non-superposed state, and it's predictable
that a nonsuperposed state will have nonsuperposed memories.  Of course
there are a lot of other minds out there, possibly including a lot of
superposed minds -- but your mind isn't one of them, and it doesn't
stand in a memory relation to any of them.

>As above, it doesn't seem to me to be what one would expect. Why do we
>have no access to these superposed states? I would have thought that just
>once in my life I could see a dead and alive cat, or does the very nature
>of information processing preclude that. If so, why?

Maybe there are superposed minds that experience superposed cats -- I'm
not 100% sure about that.  Maybe there will even be such minds, in the
future, that remember being the Jon Baxter in the past who was reading
this message.  But I-now am nonsuperposed, and it's not surprising that
everything I have "access" to (through perception, memory, etc) is
non-superposed.

>Do you have any references for this "Many Minds" interpretation of QM?
>Maybe they address the issues I've raised here.

I did a journal search yesterday.  The key reference is

Albert, D. & Loewer, B., 1988.  Interpreting the many-worlds interpretation.
Synthese 77:195-213.

This is a terrific paper that makes a good case against the more common
"splitting worlds" version of the many-worlds view.  Their treatment
of the mental side of things is a bit naive, I think, assuming an
infinite number of non-physical minds associated with any given observer,
with determinate trans-temporal identity conditions on minds.  Towards
the end of the paper they come to the realization that they needn't go
quite this far, but they don't spell things out.  They don't address
the possibility of superposed minds at all -- all of their minds are
associated directly with eigenstates.  So it's somewhat ad hoc on the
mental side of things, but I think this could be eliminated.  A view
like this seems to me to be the *least* ad hoc way of interpreting
quantum theory -- no bizarre "collapse on observation", no splitting
worlds, just a nice big wavefunction which we only see part of.

Some other references:

Albert, D. & Loewer, B. 1989.  Two no-collapse interpretations of quantum
theory.  Nous 23:169-86.

Dieks, D. 1991. On some alleged difficulties in the interpretation of
quantum mechanics.  Synthese 86:77-86.

Albert D. & Loewer, B. 1991.  The measurement problem: Some "solutions".
Synthese 86:87-98.

Healey, R.A. 1984.  How many worlds?  Nous 18:591-616.

Clarke, C.J.S. 1974.  Quantum theory and cosmology.  Philosophy of Science
41:317-332.

DeWitt, B. & Graham, N. (eds) 1974.  _The Many-Worlds Interpretation of
Quantum Mechanics_.  Princeton University Press.

Albert & Loewer 1989 is another introduction to their many-minds view,
along with a very different determinist view (a determinate-position
view) due to Bohm and Bell.  Dieks 1991 is an argument against the
Albert & Loewer view, and Albert & Loewer 1991 is a response.  Healey
1984 is a nice survey of various different ways to interpret the
many-worlds view (involving 0, 1 or an infinite number of worlds; none
of these correspond precisely to the view I've been advocating, though).
Clarke 1974 is an earlier view that bears a resemblance.  DeWitt & Graham
is the classic collection on the many-worlds view.

-- 
Dave Chalmers                            (dave@cogsci.indiana.edu)      
Center for Research on Concepts and Cognition, Indiana University.
"It is not the least charm of a theory that it is refutable."


