[ExI] Many Worlds (was: A Simulation Argument)

[Lee Corbin]

Damien writes

> At 03:54 PM 1/16/2008 -0800, Lee wrote:
> 
>> By the way, I agreed with your (Stathis's) explanations to Damien.
> 
> Oh?

Well, later, on a more careful re-reading, I did have some
nits to pick. Somehow I did not (and do not) suppose 
them substantive, but we shall see.

> So even before the quantum toss, there are already
> two separate instantiations of you, eh?

Well, I myself would not call them "separate".  They
really ought not to be, carefully speaking, referred to
in the plural. Perhaps Leibniz's "Identity of Indiscernables"
can be invoked here.

Ordinarily even though two carbon atoms are *completely*
identical, we can properly say that there are two of them
because they have one (and only one) property not shared:
location. But I suppose that this is not even true of the
"individual threads" in a GIU (group of identical universes).
Yet note that Deutsch does manage to say with that phrase
that it is a "group". 

I don't feel like there is a problem here, except in choosing
words.  The images of a flow-stream of lines which don't
quite have individual identity works for me. But I do invite
you and others to keep subjecting them (the images) to
criticism.

> This will not bother Stathis, who  (I gather) doesn't see
> any problem with starting out with infinite variations that
> just get infiniter.

We are already up to the cardinality of the continuum
(Deutsch, FoR, p. 211).  If we want to say that there
are aleph-1 "lines" or "threads" in the group---I would
suggest dropping those phrases in favor of "a measure
of aleph-1", then, to be sure, any bifurcations also
measure aleph-1.

> But it disagrees with most of 
> what I've read about MW, such as Michael Price's FAQ:
> 
> <Can we regard the separate worlds that result from a 
> measurement-like interaction (See 
> <http://www.hedweb.com/manworld.htm#measurement>"What is a 
> measurement?") as having previous existed distinctly and merely 
> differentiated, rather than the interaction as having split one world 
> into many? This is definitely not permissible in many-worlds or any 
> theory of quantum theory consistent with experiment. >

I certainly agree that we shouldn't speak of them "previously
existing distinctly".  On the other hand, it has seemed useful to
speak of some "portion" of the stream as becoming distinguished
from the rest, when we want to describe branching.

Lee