On 07 Oct 2015, at 18:58, smitra wrote:
On 07-10-2015 12:52, Bruno Marchal wrote:
On 07 Oct 2015, at 05:11, smitra wrote:
On 07-10-2015 02:04, Brent Meeker wrote:
On 10/6/2015 4:35 PM, smitra wrote:
On 07-10-2015 00:06, Bruce Kellett wrote:
On 7/10/2015 7:51 am, Brent Meeker wrote:
On 10/6/2015 1:18 PM, Stathis Papaioannou wrote:
I'm not sure I understand what you are getting at. I meant
that if the normal sequence of brain states is s1-s2-s3
with corresponding mental states m1-m2-m3 and s2 is omitted,
there is nothing in m3 to give any indication of the
discontinuity. Of course, normally s2 is necessary in order
to generate s1, but that doesn't change the argument.
But I think that's wrong. Brains are not like ideal von
Neumann computers or Turing machines that have "brain
states" corresponding to "mental states". If you simulated
a brain using a computer you would find that an enormous
number of "brain states" were required to instantiate a
single conscious thought and furthermore the brains states
necessary for one thought overlapped with those necessary for
the next thought. So this overlap at the low level is part
of the physical continuity needed for consciousness. The
fact that the physics can be simulated by discrete
computation doesn't imply that the conscious states are
discrete.
I think that is an important insight, Brent. One thing that it
means
is that two brains can, by chance, be in the same physical
state at
one instant, but those two brains might be supporting quite
different
thought processes. The consequence is that there is one person
per
brain -- the same person can't be spread over several brains.
Bruce
That's impossible, two identical physical states within an
isolated system will yield the same (statistical) results when
measured. So, if one person would be experiencing something
different compared to the other person at that very instant
then, by definition, they were not in the same physical state
at that very moment, because that's how we define physical
states to begin with.
No, the contention is that a physical state, a state that
obtains at a
single moment (Planck time?), does not instantiate a thought or an
experience. A thought or experience requires a sequence many
physical
states and having two sequences share some subsequence of states is
not enough to make the two experiences the same. Consider an
airport:
the fact that two runways cross doesn't make them the same runway.
Brent
Yes, this is the "observer moment problem" discussed a long time
ago in this list, but the requirement of needing a sequence of
states is also problematic, because at any given time I'm a
conscious being. This paradox is related to the well known
paradox where one argues that you can map the states of the brain
of a person as it evolves in time to that of a clock and then ask
why the clock isn't conscious.
Of course, the clock doesn't perform any computations, but to see
this you have to consider the counterfactual inputs and the
corresponding counterfactual outputs. Then as I've argued here
one or two years ago, a much better solution is to invoke the
MWI. Given your conscious experience, your brain can still be in
an astronomically large number of states. So, instead of
identifying yourself with the single branch, you should consider
the very large bundle branches that contain the same macroscopic
information.
The superposition of these states describes a person that is
entangled with the environment. This entanglement contains the
counterfactuals that you need to define what computation is
performed at any given moment.
But invoking the environment makes this a messy way out, a better
way i.m.o. is to include one computational step, you identify the
operator:
O = sum over inputs i of |output(i)><i|
as your observer moment . The summation is over states that fall
within your resolution, and this then partially defines a
computation.
Physical computations?
You don't need physical counterfactuals to define what is a
computation. You do need the right logic of the counterfactual to
have
a notion of first person sharable matter. But that exists in
arithmetic, using the standard, non physical, notion of computations
by Church, Turing, ...
But any observer that arises from such a deeper theory will
presumably find himself in what looks to him a physical world free
of paradoxes...
At first sight, when he looks below its substitution level, it will
see it contradicts the extrapolation he has done from the plausible
universal system around him (father, mother, earth, classical
physics, ...). But if he grasp the UDA and computationalism, he can
predict that below such a level it will look paradoxical ... until he
get used to it (the "parallel "universes" (QM).
Bruno
Saibal
Bruno
Saibal
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