I am sorry that I have not been able to keep up with the list lately.
I can only peek in occasionally.
My interpretation of the question of computationalism vs supervenience
can be put succinctly. Computationalism says that consciousness depends
both on actual behavior and on counterfactuals. Therefore, it depends
both on what happens and on what doesn't happen. Supervenience says
that consciousness depends only on physical behavior; hence it depends
only on what happens.
Since computationalism says that consciousness depends on what doesn't
happen, while supervenience says that it depends only on what happens,
the two doctrines are inconsistent.
To marry them would require altering computationalism so that it no
longer depended on counterfactuals, which then requires us to say that
all systems implement all calculations.
As far as this latter question, the framework I adopted and adapted from
Wei Dai, which I call UD+ASSA, suggests that there is a sense in which
it is true, but it is not significant or meaningful.
The UDASSA framework seeks to calculate the measure of a conscious
experience. We start by thinking of a conscious experience as something
that can be described as an abstract information pattern. Any physical
system which instantiates that information pattern can be said to
contribute to the measure of that conscious experience.
The Universal Distribution defines the measure of an information pattern
as the fraction of all programs that output that pattern. Equivalently,
the measure is the sum of 1/2^L_n, where L_n is the length in bits of
the nth program that outputs the pattern. Short programs have higher
measure than long ones; hence to a good approximation the measure depends
on the length of the shortest program that outputs it.
If we consider all programs, some of them instantiate or simulate
"physical" universes. They have their own laws of physics and initial
conditions. Some are complex, some simple. In those universes we
may find physical systems which we would naively view as instantiating
particular computations, even conscious computations. We would like to
say that such universes add to the measure of those computations.
In the UDASSA framework, this is handled by imagining a two part program.
The first part creates and runs the universe; the second part scans the
output of the first part and outputs the abstract information pattern
that represents the conscious experience. The size of this two part
program is the sum of the size of its parts. Only if both parts are
small will the contribution to the measure of the experience be large.
As has been discussed here, in principle you can find a mapping from
any physical system to any computation. This threatens to lead to the
conclusion that every consciousness is instantiated by every physical
system. Traditionally, computationalism opposed that conclusion by
insisting on support for counterfactuals. But the UDASSA framework
handles it in a different way.
In the UDASSA framework, a mapping from, say, a solid rock to an abstract
information pattern representing a moment of human consciousness would
be a very large program. In truth, this mapping program wouldn't even
need to use the rock. It could output the human information pattern just
as easily without the help of information from the rock. The mapping
program will need to include all of the information and programming
needed to generate the human consciousness information pattern essentially
from scratch. That's going to be a very large program.
In contrast, a mapping program that goes from a human brain to an abstract
information pattern representing a moment of human consciousness can
be quite compact. It would use the physical information from the human
brain state and translate that to whatever form was used to abstractly
specify the computational state. While this might be modestly complex,
it would be far, far simpler than the nearly-astronomical complexity
needed to output a human brain experience from a rock.
The result is that physical systems which have plausible "naive"
interpretations as implementing certain computations will contribute
significantly to the measure of such computations; while physical systems
where we would need a contrived and complex mapping will contribute
negligibly to such measure.
This provides a reason, within this framework, to neglect the possible
existence of conscious entities created by non-conscious computations.
Any mapping which could specify such an entity will be enormous and will
not contribute meaningfully to the measure of such entities.
Hal Finney
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Received on Tue Sep 05 2006 - 20:05:31 PDT