On 5/11/2015 11:14 PM, Bruce Kellett wrote:
meekerdb wrote:
On 5/11/2015 6:54 PM, Bruce Kellett wrote:
meekerdb wrote:
On 5/11/2015 12:14 AM, Bruce Kellett wrote:
Bruno Marchal wrote:
On 07 May 2015, at 14:45, Bruce Kellett wrote:
......
Now, having read this many times, and looked at the other summaries of the MGA, I
still feel that something crucial is missing. We go from the situation where we
remove more and more of the original 'brain', replacing the removed functionality
by the projections from the movie, which, it is agreed, does not alter the
conscious experience of the first person involved, to the conclusion that the
physical brain is entirely unnecessary; indeed, irrelevant.
Hmm... On the contrary: the brain is necessary. It is the primitive physicalness of
the brain which is not relevant.
That is not what you say in the paper. "Hence, consciousness is not a physical
phenomenon, nor can it be a phenomenon relating to observed matter at all." You go
on to say that the appearance of matter cannot be based on a notion of primitive
matter. But these are different things. Elsewhere you appear to agree that
consciousness does depend on the observed physical brain. In fact, it would be
foolish to deny this given the weight of physical evidence that shows this to be the
case.
Now that I have had a couple of days away from the internet to think about this, and
have read other comments on this thread, I think I understand better the point that
was not clear to me from the COMP(2013) paper. What your intuition claims to be
absurd in the MGA is that replaying the film can instantiate consciousness. The
reason for this is based on your belief that replaying the film is not a
computation, and since the basic assumption is of comp is that consciousness is
Turing emulable -- is in fact a computation -- we cannot have consciousness without
the associated computation.
I think this obfuscates the point. One says yes to the doctor not because one's
conscious thought is a computation, but rather because the doctor proposes to replace
part of your brain with something that will perform ALL the computations that part of
the brain could do. It is not that consciousness is a computation, rather it is a
class of computations that will map all possible (not just actual) environmental
inputs into outputs. And that's why a recording is ruled out - whether it would be
conscious or not; it is not counterfactually adequate.
The recording is not supposed to instantiate a fully conscious person, capable of
actiang normally in a changeable environment. All is was ever presumed to do was
replace just the one conscious moment (or string of moments) that were originally
recorded. This whole argumetn about counterfactual correctness is a total red herring.
Why? Have you proven that consciousness supervenes on a record?
Have you proven that it does not?
No, but I have a lot of evidence it supervenes on brain /*processes*/. Reducing that to
/*states*/ is a further assumption.
The assumption of the argument was that consciousness supervenes on the brain state.
That's not the same as saying yes to the doctor. It's your added interpretation that
consciousness supervenes on a brain state as opposed to a brain process that constitutes a
computation. Bruno, who made the argument, I think is relying on the latter.
If that is the case, then reproducing the brain state reproduces the consciousness. (Not
a brain replacement, but the consciousness of that recorded moment or moments.)
The claim that the film (and projection) is not a computation is thus false.
No, I think it's true because it's not counterfactually correct. Whether you call it
a computation or just and look-up table is, as Russell points out, a matter of
intuition about size. How many counterfactuals must it deal with? Whether the
ultrafinitism is true or not, our theory of the world and consciousness should not
depend on there being infinities. So within ultrafinitism all TM's can be replaced
by lookup tables. Or looked at the other way around, a sufficiently enormous lookup
table is a computer.
As stated above, counterfactual correctness is not required to reproduce just the one
original conscious moment.
But how do you know this. Consciousness is somewhat mysterious. Bruno starts with idea
that you can replace part of the brain with something that is I/O functionally
identical. Saying yes to this doesn't commit you saying that a recording is
functionally identical.
You are conflating two issues. "Yes Doctor" is not about recordings, but fully
functional general computers that can reproduce all the functions of your brain. We are
talking here about a recording of one set of conscious moments.
You would very likely only say yes if the device were counterfactually correct for at
least a large range of inputs. So it certainly doesn't follow from "saying yes to the
doctor" that you must also agree that a recording will instantiate consciousness.
That a recording is conscious is plausible because supervenience on a sequence of
physical states is plausbile. But it has its own problems: Like the rock that computes
everything, the sequence of states may be conscious of everything.
The same goes for the existence of normal numbers, which must contain within themselves
all possible states of the dovetailer, including all possible relations to the universal
numbers that Bruno insists are essential for there to be a computation.
Yes, I think that's a generic problem for these TOE's that start with
everythingism.
So conterfactual correctness is not important for the single conscious moment. It
might be one way of saying that a conscious person is one who can respond, more or
less appropriately, to a range of physical circumstances (external inputs), but it
says nothing about separate conscious moments.
I think the concept of separate conscious moments is incoherent. Conscious "moments"
need to have duration and to be in overlapping sequences, and they need to occur in
reference to an environment.
That is why I try to be careful to refer to a conscious moment *or moments*.
But it is by no means clear that a need for counterfactual correctness can be
concluded from the computations of the dovetailer. The idea there seems to be that the
same conscious instant (or sequence of instants) is reproduced many times in the
dovetailer, and many of these will lead to different continuations, implying that each
instance has to be more flexible than is required for *that* instant.
I think you are equating a conscious moment with a state of the dovetailer. I think a
conscious moment, a thought, must correspond to a long sequence of dovetailer states
which may not be identical but only 'similar enough' at a classical level.
I think this is where your concern about the need to include quite a bit of the external
world in the set of states that instantiate a consciousness comes to the fore. The
assumption is that consciousness supervenes on the physical brain. That brain obeys
deterministic physical laws, so the set of dovetailer states that gives a consciousness
must also give a coherent world that obeys a set of deterministic physical laws. Since
the same laws obtain over the whole universe that is accessible to us (I do not comment
on type II or IV universes), then the relevant set of dovetailer states must cover the
whole history of the observable universe. If they did not, there would be no requirement
that the laws apply consistently across the whole universe. We have to have a theory
that agrees with observation at at least this level. SO I am beginning to think that the
dovetailer states that sustain one consciousness must also sustain all other
consciousnesses that exist, or have existed, as well as the whole physical universe from
the time of the big bang.
OK, this might be possible, but I think it reduces the set of dovertailer states over
which one must sum to a set of essentially zero measure. Does this make sense? I
struggle to think that it does.
Yes, I think that's right and I think this universe, and all universes with physics (i.e.
consistent laws) are of measure zero. It's like the Boltzmann brain problem. Maybe's
there's a solution or maybe it's just an appeal to the anthropic principle.
But I have a problem with this if the dovetailer is instantiating a classical physics
model of consciousness. There is an important theorem in complex analysis that states
that if two analytic functions coincide in a neighbourhood, no matter how small, then
the two functions are equal everywhere in the region over which they are analytic.
This has its parallel in classical physics, where it can be shown that if one is given
initial data over some Cauchy surface, then the complete past and future of that
system is determined, and calculable in terms of known physical laws.
This all depends on continuous functions. I don't think anything similar applies to
digital computations.
I think that, in effect, it does. See above.
This seems to imply that if two computations coincide for some sequence of conscious
states, then the continuations of those computations must be identical. If they are
not, then the computations do not instantiate consciousness that is governed by
deterministic physical laws.
That's why Bruno wants to model consciousness as a bundle of threads of computation.
The bundle can divide and diverge presumably modeling Everett's MWI.
But Everett's MWI is entirely deterministic and law-governed. It cannot be reproduced by
random variations from dovetailer state to dovetailer state. I think the importance of
the deterministic nature of the MWI is frequently overlooked.
The UD is executing infinitely many threads of computation. Imagine the UD is simulating
universes at the quantum level. Then a single person's thought would be realized by an
enormous number of sequences of states that were only the same at a crude classical
level. At the UD level there would differences that would cause them to,
deterministically, diverge into different threads corresponding to different amplified
quantum outcomes. Since the number of threads is essentially infinite, branch counting
can handle the probabilities.
Brent
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