On 31 Mar 2015, at 07:19, meekerdb wrote:
On 3/30/2015 10:17 PM, Bruce Kellett wrote:
meekerdb wrote:
On 3/28/2015 11:36 PM, Bruce Kellett wrote:
Bruno has acknowledged that this is not what the MGA shows. MGA
simply shows that his version of computationalism is incompatible
with physical supervenience. This cannot be seen as surprising
since it is explicitly built into computationalism that
physicalism is false.
That's not my understanding. Bruno's argument starts with
assuming that a part, or all, of your brain could be replaced by a
digital AI with the same I/O and if done at a suitably low level
of detail (probably neuronal) you conscious inner life would be
essentially the same. That seems to me to be assuming physicalism
as the basis of consciousness.
This contradicts what you say below about Bruno assuming that only
certain special processes institute consciousness.
He's trying a reductio. So he assumes physicalism - that some
physical processes produce consciousness (not just any physical
process) - and tried to reach the absurdity that the physical
process can be a do-nothing process.
I think there is an ambiguity, or uncertainty, about just what the
program that is to replace part or all of your brain does. If the
program is just a simulation of the actual physical brain, neuron
by neuron, synapse by synapse, so that that physical laws that
govern the behaviour of these brain elements are instantiated by
the computer, and act on the initial data given by the state of the
brain when the program is started, then there will be no essential
difference between the program and the brain it replaces. In this
case you might say "Yes, doctor", with some confidence. The
necessary programming would presumably be well understood since the
brain is deterministic at the level with which we are concerned,
and the physical/chemical laws can be determined. If the initial
state can be ascertained with sufficient precision without killing
you, then the simulated computer brain substitute acts just like
the original, so should give no problems.
This understanding is based on the idea that consciousness
supervenes on the processes and states of the physical brain. These
have been replaced by equivalent physical processes, so
consciousness should remain intact. There is no appeal to
computationalism here.
Sure there is; it's the requirement that the computer compute the
equivalent physical processes. They are equivalent in the sense of
producing the same sequence of states (at whatever level they are
simulated).
The simulating computer has to perform many detailed calculations
to carry through the operation of known physical laws on the
initial data, but I don't think anyone is saying that consciousness
supervenes on such calculations.
I think they are. In fact didn't you say so above: "...then the
simulated computer brain substitute acts just like the original, so
should give no problems." Are you making some distinction between
simulating the brain and simulating the physics of the brain?
The other approach is to assume that the computer used to replace
your brain is running a true AI program. It is not simulating the
physical processes piece by piece, but running some black box
program that has been shown to reproduce known brain outputs for
some range of suitable inputs. The program is presumably supposed
to implement the universal TM computations upon which consciousness
supervenes independently of the underlying hardware/wetware. If
this is the model you have in mind, then the computationalist model
directly contradicts physical supervenience, right from the outset.
No, as I understand it Bruno is assuming the doctor replaces all or
part of your brain with a digital device (or even an analog one so
long as it's function doesn't depend on infinite precision) that
computes the same I/O function at it's interface with the rest of you.
Now, I think the interesting question to ask is: "Given these two
different implementations of the brain replacing program, would you
have equal confidence in both possibilities?"
I think the answer would, in general, be "No!". The program that
assumes physical supervenience can be tested element by element, so
that once it has been shown to truly follow the known chemical and
physical laws, and accurately reproduces the structure of your
actual brain, it will be counterfactually correct, and could be
trusted into the future.
The alternative, computationalist model cannot be tested in this
way. Basically because it is necessarily holistic. Consciousness is
assumed to supervene on a particular type of computation, but is
your computationalist program the same as mine? How do we know? I
do not think the we could ever guarantee that such an AI device was
counterfactually correct for /your/ brain. Many artificial learning
programs, based on neural nets or the like, can be trained to
perform with great reproducibility on the training data set, but
fail miserably once one goes outside this data set. They are not
counterfactually correct, and I do not know how you could ever
ensure the necessary counterfactual correctness, even if you did
imagine that you knew precisely the sort of computation upon which
consciousness supervened.
So I would reject the computationalist program right at the start
-- I would not say "Yes, doctor" to that sort of AI program.
Nor would I or Bruno. But what about the other kind of simulation.
It is still reducible to a program running on a UTM - except for
interaction with the world outside the brain. As I understand it
Bruno finesses this problem by (1) saying the subject is conscious
while dreaming so the external world isn't necessary to consciousness
It is not usable. The external world is made like a god of the gap. It
is like chosing a special universal number, and say, we got the theory
of everything, where computationalism says (or seems to) that below
our substitution level what there is is an invariant resulting from
the limit of the first person experience on all computations. All
universal numbers are in competition below. Above there is a finite
(or infinite) competition too.
If not, you say that one u solves the measure problem. That is
possible, but if true we can prove it. (assuming computationalism).
or (2) if it's necessary whatever part of it that is necessary can
be added to the UTM simulation.
And all that parts are added, including aberrant one with white
rabbits, in the arithmetical relation.
I know I have to explain better a point which is perhaps hard to
understand fro some, but the arithmetical reality does not just
contain description of computations, it literally emulates them all.
You don't need comp for this, the sigma_1 complete part of arithmetic
emulates, infinitely often, all computations. That is not an
interpretation, it is a theorem in math, without any controversial
axioms, nor interpretation.
Then with the assumption of computationalism added, you next states
can only be indetermined on all computations going through your
states. That gives a way to test comp.
Once you have consciousness instantiated by a UTM program then he
and Maudlin argue that the computation can be inert.
Well, notably. In the process of showing the incompatiblity between
the existence and role of some primitive matter, and the
computationalist assumption.
I think that's his argument, but Bruno can correct me if I'm wrong.
No problem, except the point above. MGA does not show that matter +
comp are logically contradictory, but it is epistemologically
contradictory. It is not that we don't need the matter hypothesis, it
is that we cannot use it, except as a God-of-the-gap to slow down the
inquiry if comp is refuted or not, or if it explains well the origin
of matter, and in that case that would be an evidence that it might be
correct on consciousness, intelligence, protagorean virtue, and the
Noùs, and the One, too.
Primitive matter is to computationalism like Bohm hidden variable is
to Everett QM.
Bruno
Brent
Bruce
The MGA is, therefore, largely irrelevant, because it does not
prove anything that we didn't already know. It certainly does not
show that consciousness is an abstract process in Plationia,
independent of any physical process.
Bruno assumes that only some special processes instantiate
consciousness and these are characterized by being computations of
some kind, i.e. a sequence of states that could be realized by a
program running on a Universal Turing Machine (not necessarily
halting). Since the consciousness computation defined this way is
an abstract mathematical process in Platonia; it is equivalent to
assuming consciousness is instantiated by an abstract mathematical
process.
Brent
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