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
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
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?
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