On 20 Jan 2010, at 11:25, Stathis Papaioannou wrote:
2010/1/20 Nick Prince <m...@dtech.fsnet.co.uk>:
If the no clone theorem were a problem then you could not survive
more
than a moment, since your brain is constantly undergoing classical
level changes.
How interesting!! I had forgotten that most people believe that
consciousness is a classical rather than quantum process (Penrose
excepted). Thank you for bringing this to my attention. So the no
clone theorem should not pose a problem for copy builders after all.
Even if perfection to the quantum level is needed for a copy (it can't
be, since our brains do change over time, whether quantum level events
are important or not) the no clone theorem says that it is not
possible to make a perfect clone at will. It is still possible to make
a perfect clone by preparing multiple variations of a copy.
I agree. Quantum computer does not violate Church thesis, and are
emulable by classical Turing machine (combinators, elementary
arithmetics, etc.).
In particular the Universal Dovetailer does execute the emulation of
all rational approximation of the relativistic Schroedinger equation
applied to the quantum state of the Milky Way.
In the UD-time, defined by the (arithmetical) execution step some
(fixed) universal dovetailing, you will have to wait gigantic time
before the UD generate such a state, and again comparable time before
it proceeds to the next step, but this is irrelevant because the first
person cannot be aware of the "delays" of the reconstitution or
(quatum-like) preparation.
What do you think could happen if there were 100 copies of you
running
in parallel and 90 were terminated? If you think you would
definitely
continue living as one of the 10 remaining copies then to be
consistent you have to accept QTI. If you think there is a chance
that
you might die I find it difficult to understand how this could be
reconciled with any consistent theory of personal identity.
I know. To be consistent with my other assumptions I would have to
believe in QTI but it is just so difficult to swallow. I think the
hardest bit comes when we think of what we would experience. Suppose
I lived in 200BC or before. It's hard to think of ways you could
keep
on surviving apart from alien visitations with copying machines etc.
This is one reason I have looked in some detail into Tiplers omega
point theory. I don't think this should be written off as being too
whacky just because others have got onto the Tipler bashing
bandwagon. It has not been refuted yet in terms of the accelerated
expansion of the universe or for other reasons which I can eloborate
on - but that is besides the point. If Tiplers final simulation is a
Universal Dovetailer then anyone who has ever lived in the past could
in principle find themselves as a consistent extension in that
simulation. This is one explanation how people could avoid ending up
in a cul de sac branch.
Well, it is possible that the MWI is false. And as I understand it the
MWI does not actually say that anything that can happen, will happen,
although it is often assumed that it does; so it may be that sometimes
probabilities go down to zero, which would make the QTI false.
I would say, to Nick Prince, that Tipler is a bit naïve on his
theology, which is based on Aristotelian implicit assumptions. His
book on immortality is very courageous, and contains interesting
points. Yet, he completely abandon rigor when it comes to theology. It
is more a reflexion on Christian theology by a physicist, than a
rigorous attempt in general or theoretical theology. Of course, the
lack of rigor in theology is almost institutionalized on this planet
since a long time.
Then Tipler seems not to be aware that the comp hyp he is using is not
compatible with its explicit physicalism ...
He is not aware also of the quantum immortality which follows from the
quantum MW, and he missed like many the comp immortality.
I don't think it makes sense that the QTI or the comp-TI can be false
in any way (except by making the QT or comp false). To die with
probability one you have to really find a finite proof in Robinson
arithmetic that 0 = 1. If you find a proof that 0 = 1, you will just
backtrack, perhaps up to Peano or Robinson arithmetic.
According to RSSA and the RSSA your absolute measure in the
multiverse
decreases with each branching as versions of you die. According to
the
RSSA this doesn't matter as at least one of you is left standing;
according to the ASSA, this does matter and you eventually die. The
only way I can make sense of the latter is if you have an
essentialist
view of personal identity. Under this view if a copy is made of you
and the original dies, you die. Under what Parfit calls the
reductionist view of personal identity, you live.
Hmm.. I think that what I am calling absolute measure you think of
as
relative measure or something like it. I thought absolute measure
was
the total measure of my existence across the whole multiverse. If I
cannot die then RSSA implies this would be conserved. As you traverse
down a particular branch though, your measure would indeed decrease
for both RSSA and ASSA but it would eventually decrease to zero for
ASSA when you died! With RSSA it could only decrease asymptotically
to zero, but never completly disappear.
There is the absolute measure of a particular OM, and there is the
absolute measure of all the OM's associated with a particular person,
and both of these are fixed. As you age, the absolute measure of the
OM you are experincing decreases because versions of you die. I think
everyone agrees with this.
I am not sure "absolute measure of an OM" makes any sense. Even for 3-
OM.
Relative measure for 3-OM makes sense, but the comp supervenience
thesis does not relate 1-OM with such relative measure in any easy
way. That's why we have to find a good (mathematical) definition of 1-
OM, and before that, of "first person" (like the one by Theaetetus),
and then do some math.
Relative measure concerns the ratio of the measure of one OM to that
of another OM or set of OM's. The ASSA/RSSA distinction came up in
relation to QS/QTI, which concerns the probability of your next moment
of experience. The RSSA says you should consider only the OM's which
are candidates for your next moment and assume that your next moment
is sampled randomly from these. In this case, their absolute measure
is irrelevant, and only their measure relative to each other is
important. The ASSA assumes that the sampling should be over all your
OM's, so if the absolute measure of your all potential next moments is
greatly decreased because the guillotine blade is falling and is 1mm
from your neck, then your probability of surviving to the next moment
is very low. This is a corollary of the claim that you are more likely
to find yourself in a high measure OM than a low measure OM. Hopefully
someone can comment if I have misrepresented the ASSA view, because I
just don't see how it could make sense.
I think the term "observer moment" (OM) comes from Nick Bostrom.
Usually I don't use it, except in short conversation when the context
helps to give it some meaning.
The problem with this expression, or more precisely with many uses of
that expression, is that, somehow, it is still based on some identity
thesis like 3-OM ==== 1-OM. But with the comp supervenience thesis,
things are far more complex. Roughly speaking, although from the 1-OM
view, it makes sense to put a measure on all 3-OM reasonably extending
the 3-OM chosen by the doctor for your 1-OM, the measure itself will
be related to the mathematical structure of the complete computational
histories of those 3-OM.
And things are even more complex when you take into account that we
can backtrack per amnesia, if we follow Saibal Mitra, so that the "1-
you" is not a well defined notion.
Here the math can help, but almost negatively, by showing indeed that
no machine can ever really know who she is. Your 1-you just cannot be
defined by you (be it the 1-you, or the 3-you).
For the 3-OM, the (very big, though) set of "next" 3-OM can make
sense. But for the 1-OM, it does not. It happens that with the
Theaetetical definition of knowing (Bp & p) and observing (Bp & ~B~p)
we can associate topological and quantum space of coherent sets of
computational consistent extensions (when p is Sigma_1) so that the
logic of the "measure one" can be derived from the math (that is done
in AUDA), and it gives something resembling quantum logic, and
confirming the universal-dovetailer-related kind of MW.
For those who missed the definition of "p" and "B":
p is for Sigma_1 arithmetical sentences. They are provably equivalent
with sentence having the shape ExP(x) where P is a decidable
predicate. They have the property that, when true, they are provable
(by sigma_1 complete (= universal) machine. So "p -> Bp" are TRUE for
them. And B here and above is for Gödel's 1931 provability predicate.
Löbian machine "knows" that they are Sigma_1 complete: they can PROVE,
for them, that "p -> Bp".
It is really the computer science constraints which put a mathematical
structure on the machine's mindscape, and it is hard for me to imagine
we can progress if we don't dig a bit more on the math of computer
science. I am sorry for that.
Even before using computer science, a bit of modal logic (which is far
more easy) can help. People can perhaps search on "modal" in the
archive for many (old) posts illustrating this. Modal logic, with
unary connector like B and D (D = ~B~), are *the* tool for doing
rigorous metaphysics (not just the computationalist one).
Bruno
http://iridia.ulb.ac.be/~marchal/
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