Deutsch (was Re: Marxism as science)

[Chuck Grimes]

``Despite the unrivaled empirical success of quantum theory, the very
suggestion that it may be literally true as a description of nature is
still greeted with cynicism, incomprehension and even anger...'' 

Ian Murray

------------

So I went to Deutsch's website and did manage to sort of read
mathematical physics for New Years. It seemed to be more interesting
than getting drunk or stoned and watching a bad movie. Maybe it's the
same, but I couldn't tell. Try:

 http://xxx.lanl.gov/abs/quant-ph/0104033 

for the mathematical version of the multiverse. I think what this is,
is something like a discretized Hilbert space, my image of which is an
exfoliated onion.

The difference that Deutsch adds though is to transform the quantum
world, into the universe, which is a world of information about
itself. In other words, the physical world is modeled as if it were an
information universe. Just to twist your mind around, here are his
concluding remarks on the mathematical model:

``Since a generic quantum computational network does not perform
anything like a classical computation on a substantial proportion of
its qubits for many computational steps, it may seem that when we
extend the above conclusions to the multiverse at large, we should
expect parallelism (ensemble-like systems) to be confined to spatially
and temporally small, scattered pockets. The reason why these systems
in fact extend over the whole of spacetime with the exception of some
small regions (such as the interiors of atoms and quantum computers),
and why they approximately obey classical laws of physics, is studied
in the theory of decoherence (see Zurek 1981, Hartle 1991). For
present purposes, note only that although most of the descriptors of
physical systems throughout spacetime do not obey anything like
classical physics, the ones that do, form a system that, to a good
approximation, is not only causally autonomous but can store
information for extended periods and carry it over great distances. It
is therefore that system which is most easily accessible to our senses
­ indeed, it includes all the information processing performed by our
sense organs and brains. It has the approximate structure of a
classical ensemble comprising `the universe' that we subjectively
perceive and participate in, and other `parallel' universes.

In Section 1 I mentioned that the theory presented here does roughly
the same job for the multiverse as the theory of foliation into
spacelike hypersurfaces does for spacetime in general
relativity. There are strong reasons to believe that this must be more
than an analogy. It is implausible that the quantum theory of gravity
will involve observables that are functions of a c-number time.
Instead, time must be associated with entanglement between clock-like
systems and other quantum systems, as in the model constructed by Page
and Wootters (1983), in which different times are seen as special
cases of different universes.  Hence the theory presented here and the
classical theory of foliation must in reality be two limiting cases of
a single, yet-to-be-discovered theory ­ the theory of the structure of
the multiverse under quantum gravity...''  (Deutsch, The Structure of
the Multiverse, 19-20p)

On the other hand there are some very subtle problems that lurk within
this mathematical formalism, most of which I don't understand, except
to perceived as in a heavy fog.

The first of these problems is something like Occam's razor or the
parsimony test. Do we need to postulate all these foliations to
explain anything meaningful for our physical or scientific
understanding of the world? 

Deutsch's answer is yes, and he gives Zeno's paradox as the
reason. How can you get to the end, if each step is only one step in
an infinite path of such steps? Or alternatively, if there are a fixed
discrete number of such steps, what happens to you between steps?
Deutsch's answer is you need the multiverse to resolve this
dilemma.

Another problem is something I think of as Hegel's mistake. The
mistake is to conflate the phenomenology of mind with the
phenomenology of the world. This makes the assumption that the world
and its processes are knowable because there is no meaningful
difference between the world and the mind that experiences the
world. The two are somehow reciprocally interchangeable. The problem
here is, if this assumption is accepted, then there is no method
available to distinguish between, what I consider two distinct realms:
the world, and the mind (or in collective terminology, then the human
and physical worlds). This solves the problem of knowledge by
subjectifying the world, or conversely objectifying the mind.

The transposition of this mistake into the case of mathematical models
is that there is no meaningful distinction to be made between the
mathematical models of the world (activities of mind) and the physical
world itself (processes of material reality). In other words, advanced
physical science makes the same romantic mistake as its arch rival,
the great grand-daddy of postmodernism his own bad self, George
Wilhelm Fredrick.

To my thinking, David Hawking has reached the terminal phase of this
mistake, when he postulates what he calls the strong anthropic
principle, ``We see the universe the way it is because we exist.''
[124p. Brief History of Time]. He later extrapolated this idea into
a potential argument for the existence of god in some subtly about the
infinite, but bounded universe, that escapes me at the moment. If you
re-read Deutsch above, you will see a permutation on a similar
anthropic principle.

In some intuitive sense, I see all these problems and even Deutsch's
multiverse (world as information) as symptoms of a cultural terminus
on the plateau of reason, the postmodern turn, the horizon of the
knowable. On the other hand, I don't want to launch immediately into
some bizarre and convoluted discussion of meaning and linguistics, or
get lost delving into some other hermeneutic realm as an alternative.

It seems to me, that it is possible to simply hold all of this in
suspension, as potentials none of which have yet crystallized into
anything resembling what we might later look back on and call science,
art or history.

Chuck Grimes