On 20 Jan 2014, at 18:23, meekerdb wrote:
On 1/20/2014 12:15 AM, Bruno Marchal wrote:
On 19 Jan 2014, at 21:07, meekerdb wrote:
On 1/19/2014 2:43 AM, Bruno Marchal wrote:
I also find it unlikely that the subst level is above the
quantum level. Or at least I think that if it's at the quantum
level then we can guarantee that the duplication arguments would
work (assuming we could duplicate objects at that level, which
we can't due to a fundamental principle...!)
It can, just above that level. And also below, because the UD
does not need to duplicate your body, only the
part of the body doing the computations, and so the UD needs only
to prepeare the multiple copies, so the UD argument go through at
step seven, even if the subst level is below the quantum
uncertainty level.
There is not only the level of substitution, there is the scope.
I include the scope in the level, usually invoking the "generalized
brain".
When you say 'yes' to the doctor, the doctor is only going to
replace a part of you and leave the rest of the world intact.
By definition, it replaces your generalized brain (that is the
whole part of the universe that you need to simulate at some right
level, to let the consciousness invariant). If you think that your
consciousness supervene on your biological brain + the galaxy, let
it be. It makes step 1-6 harder to imagine, but not invalid, and
that should be clear at step 7, because the UD will go infinitely
often through your state, no matter how the scope is large
and the level is low, as long as it exists (and it exists as we
assume comp).
But the rest of the world also contributes to your computation.
When you write, "only the part of the body doing the computations"
you are implicitly ignoring computation done in other parts of
your body -
Not at all. I don't even exclude a priori that we might simulate
the entire observable or even non observable physical universe. The
reasoning does not depend on the choice of the level/scope, only
that it exists (and then is Turing emulable).
which may not be important for mathematical theorizing but may be
important for deciding to take your finger out of the fire. This
is the source of my dissatisfaction with the MGA. It implicitly
assumes you can cut off this interface between "the part of you
doing computations" and the rest of the world by
anticipating all the possible interface events. I don't think
that can be done.
If such cut-off cannot be done, then comp is false or the level is
so low that we have to simulate the entire physical universe at
some level. If that simulation does not exist, then comp is false.
If it exists, then it is done infinitely often in arithmetic, and
the reasoning go through. OK?
Yes, I understood that. But I think that scope of the simulation
must be very large. If it is essentially the physical universe then
it seems to me that means there is no distinction between simulated
and real.
They are not distinguishable by a machine, but they might still
conceivably be different. Peter Jones, would say that the non emulated
one is real, the emulated one is fiction. Of course he needs to reify
"matter".
The simulated physics is the same as real physics in a different
world. Yet a significant part of your thesis is that the
(conscious?) mind is independent of the physics and can be realized
in different physics.
Not at all. Actually the direct contrary. Yes, comp implies that there
is a level of substitution such that I would not see the difference
after the substitution, but then the whole UDA explains that this
makes the physical laws invariant for all possible computational mind.
That's the inference you draw from saying "yes" to the doctor.
Yes.
I'm challenging the validity of that inference.
Then the game, is that you have to find a flaw. or to prove that there
is a contradiction between the premise and the conclusion, like it
seems you argue here.
I think part of one's confidence in saying "yes" relies on the
fact that whatever the doctor does it's going to function within
your old physics.
Yes, and the reasoning shows that this intuition is jeopardized
indeed, so some people just abandon comp because they think that we
have got a contradiction. But that is just a feeling. On the contrary,
(and you are close to the conclusion) here, comp will work because the
laws of physics will appear to be the same for all machines. We will
never leave our old physics. On the contrary we will justify them as
theorem in arithmetic, so they become more "solid" in some sense.
Bruno
http://iridia.ulb.ac.be/~marchal/
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