I'm trying to define "identity"...

Let's write x~y if SAS's x and y (possibly in different universes) have
the same identity.  I propose that this relation must be reflexive,
symmetric and transitive.  This neatly partitions all SAS's into
equivalence classes, and we have no ambiguity working out whether any
two SAS's across the multi-verse have the same identity.

Consider an SAS x that splits into x1, x2 (in child universes under
MWI).  We assume x~x1 and x~x2.  By symmetry and transitivity we deduce
x1~x2.  So this definition of identity is maintained across independent
child universes.

This is at odds with the following concept of identity... 

> I am, for all practical purposes, one 
> and only one specific configuration of atoms in a specific 
> universe. I could never say that ' I ' is ALL the copies, since I 
> NEVER experience what the other copies experience

It seems necessary to distinguish between a definition of identity and
the set of memories within an SAS at a given moment.

Is it possible that over long periods of time, the environment can
affect an SAS to such an extent that SAS's in different universe that
are suppose to have the same identity actually have very little in

What happens if we "splice" two SAS's (including their memories)?

It seems to me that the concept of identity is not fundamental to
physics.  It's useful for classification purposes as long as one doesn't
stretch it too far and expose its lack of precision.

This reminds me of the problem of defining the word "species".  Although
a useful concept for zoologists it is not well defined.  For example
there are cases where (animals in region) A can mate with B, B can mate
with C, but A can't mate with C.

- David

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