Le 21-juin-05, à 21:21, Pete Carlton a écrit :
I think the practical differences are large, as you say, but I
disagree that it points to a fundamental metaphysical difference. I
think what appears to be a metaphysical difference is just the
breakdown of our folk concept of "I". Imagine a primitive person who
didn't understand the physics of fire, seeing two candles lit from a
single one, then the first one extinguished - they may be tempted to
conclude that the first flame has now become two flames. Well, this
is no problem because flames never say things like "I would like to
keep burning" or "I wonder what my next experience would be". We,
however, do say these things. But does this bit of behavior
(including the neural activity that causes it) make us different in a
relevant way? And if so, how?
This breakdown of "I" is very interesting. Since there's lots of talk
about torture here, let's take this extremely simple example: Smith is
going to torture someone, one hour from now. You may try to take
steps to prevent it. How much effort you are willing to put in
depends, among other things, on the identity of the person Smith is
going to torture. In particular, you will be very highly motivated if
that person is you; or rather, the person you will be one hour from
now. The reason for the high motivation is that you have strong
desires for that person to continue their life unabated, and those
desires hinge on the outcome of the torture. But my point is that
your strong desires for your own survival are just a special case of
desires for a given person's survival - in other words, you are
already taking a third-person point of view to your (future) self.
You know that if the person is killed during torture, they will not
continue their life; if they survive it, their life will still be
negatively impacted, and your desires for the person's future are
thwarted.
Now, if you introduce copies to this scenario, it does not seem to me
that anything changes fundamentally. Your choice on what kind of
scenario to accept will still hinge on your desires for the future of
any persons involved. The desires themselves may be very complicated,
and in fact will depend on lots of hitherto unspecified details such
as the legal status, ownership rights, etc., of copies. Of course one
copy will say "I pushed the button and then I got tortured", and the
other copy will say "I pushed the button and woke up on the beach" -
which is exactly what we would expect these two people to say. And
they're both right, insofar as they're giving an accurate report of
their memories. What is the metaphysical issue here?
There are two *physical* issues here.
1) The simplest one is that if you agree with the comp indeterminacy
(or similar) you get an explanation of the quantum indeterminacy
without the collapse of the wave packet. This is mainly Everett
contribution.
2) The less trivial one, perhaps, is that if you agree with the comp
indeterminacy you get an a priori explosion of the number of
appearances of first person white rabbits and the only way to solve
this, assuming the SWE is correct, must consist in justifying the SWE
from the comp indeterminacy bearing on all computational
states/histories.
The issue "1)" is that an indeterministic physical theory is reduced to
a deterministic physical theory.
The issue "2)" is that physics is reduced (at least in principle) to
math/computer science.
Bruno
http://iridia.ulb.ac.be/~marchal/
