Bruno Marchal writes:
If on the basis of a coin toss the world splits, and in one branch I am
instantaneously killed while in the other I continue living, there are
several possible ways this might be interpreted from the 1st person
(a) Pr(I live) = Pr(I die) = 0.5
I hope everyone sees that this (a) is not defensible once we *assume* comp.
Good, we agree here. I don't think everyone on this list would agree.
(b) Pr(I live) = 1, Pr(I die) = 0
And this one (b) is a consequence of comp.
(c) Pr(I live) = 0, Pr(I die) = 1
Option (c) may look a bit strange but is the one that I favour: all first
person experiences are transient, all branches are dead ends, no world is
accessible from any other world.
I think I figure out why you say that and why you take it probably as a
consequence of comp.
Let us see.
However, the various independent, transient observer moments are ordered
in such a way in what we experience as ordinary life that the illusion of
Yes right. But that "illusion" is all what the first person notion is all
about. Your "c" is too strong. What would you say if your comp doctor
proposes you an artificial brain and adds that the Pr(I die), for you, is
1. I think you would say "no doctor". Then the doctor (not you!, I know you
are doctor!) adds that in all case Pr(I die) = 1. Then you will tell him
that he has not given any clue about the probability your first person
"illusion" (I hate this word) lasts. The real question we ask to the doctor
is what is the probability my "illusion" will lasts *as* it lasts for any
other medical operation when it is said the operation has been successful.
What I have called "Papaioannou's multiverse" are just your transient
observer moments *together* with the order you are indeed adding on them
for giving sense to ordinary experience. That order *is* an accessibility
OK, you've put that quite well. Even if continuity of identity is an
illusion, it is an important illusion. An analogy would be going to the
cinema to see a movie: the "reality" might be that we are watching a series
of still images, but the important thing for the audience is that the
illusion of motion is maintained by having a certain minimum frame rate. So
yes, this does give rise to an accessibility relationship, but it
presupposes a theory of personal identity. Even on this list, there are
people who might say (a) above is the case rather than (b) or (c).
This covers such (theoretical, at present) cases as the apparent
continuity of identity between two observer moments that just happen to
seem to be consecutive "frames" in a person's life even though there is no
physical or informational connection between them.
But you cannot deny that with comp, there *is* some informational
connection between them. The connection will appear to be exclusively
mathematical and immaterial. And will appear to be the logical root of
another "illusion": a physical world. We know this by UDA (the Universal
Dovetailer Argument), but we need to isolate completely the structure of
the multiverse extractible from comp if we want to derive the precise
physics from comp (and then to compare with the empirical physics to
evaluate empirically the plausibility of comp (or of its many variants).
What I meant by "informational connection" was actual information transfer
from one frame to the next, by some physical process. This is what happens
normally by virtue of the fact that consecutive frames are implemented by
the same physical brain. It is also what would happen, in a different way,
with teleportation. This is sufficient for the experience of continuity of
consciousness, but it is not necessary: the appropriate frames or observer
moments might occur completely randomly in different parts of the
multiverse, and the first person experience would be the same. (Such is not
the case for observation of third persons: the frames or observer moments
must be explicitly ordered, or they will be lost in the noise). Is this what
you mean by "the connection will appear to be exclusively mathematical and
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