Second, the book describes a bizarre sequence of events: a character who
experiences uploading in one universe has the exact same brain state as
a character who is insane and _thinks_ he experienced uploading in another
universe. When the first upload is terminated, the second character
proceeds to gradually overcome his insanity. (At least, that's what I
think is supposed to have happened. Another interpretation which is
technically as plausible is that the character was simply insane and had
an insane vision of the universe which turned out, against all odds, to be
true.)
This is related to the many-minds school of QM, where an entity with
a given brain state can be said to span many (perhaps infinitely many)
parallel universes. My mind right now is shared among multiple instances
in different universes. As events happen which distinguish the universes,
my mind in effect splits into multiple, disjoint, non-interacting parts.
Conceivably in some of those universes I could be uploads, being watched
over by beings who are simulating me, while in others I could be living in
the base reality. In yet others I could be in some kind of VR. And I
suppose in some I could be an insane alien being who has fantasized
the entire world of human existence, including an identity for himself
which happens coincidentally to match in every detail my own identity.
With an infinite number of universes, it's bound to happen somewhere.
This last case is the most similar to the situation in Permutation City,
and I think it is equally implausible.
Hal