X-Message-Number: 26697
Date: Tue, 26 Jul 2005 09:14:58 -0400
From: Thomas Donaldson <>
Subject: more on identity and equivalence

To Mike again!

Sorry, Mike, but your abstract definition once more fails to produce
a clear notion of identity AS DISTINCT FROM what you call equivalence.
How do we work out that every member of set A also belongs to set B,
and presumably vice versa? As a guess, something is a member of 
set A if it has characteristics x,y,z, and a member of B is it has
those same characteristics. Infinite lists of characteristics
won't work here, either.... not just for practical reasons, but for
the simple reason that even the possession of ONE characteristic
raises the same problems about identity. 

There is a lesson here that bears a lot on discussions of whether
we survive or not --- survive our suspension, for instance. No one
so far has insisted that we retain ALL PREVIOUS characteristics 
upon our revival. Nor has anyone claimed that we survive if the
opposite happens.

In my previous discussion of this subject I gave a short discussion
of what I was at age 10. I would suggest that we take this notion
as a definition of survival of cryonic suspension, too: we may not
retain all our memories, but we retain some, particularly important
ones to us. If our abilities differ from those we had before our
suspension, they will have come as developments of abilities we
had before our suspension. As for our memories and abilities,
their survival will resemble the normal survival of both: upon
our revival and recovery, we'll still be able to ride a bike if
we knew how to do so before, and ditto for playing a piano.

Yes, in a sense we're continuous from the time when we were 10.
Specifically because our repair may require a loss of physical
continuity, I will say that survival by my definition does
not require physical continuity, but does require a continuity
of memories and abilities as I describe it above.

Again, this definition also contains the requirement that duplicates
which satisfy the same definition for identity do not exist. Note
that such duplicates might have different memories and abilities
from you after your revival, but will have the same relation given
above to yourself before suspension. In that sense I require that
you be unique. I will add, as a reason for this clause in my definition,
that failure to be unique will change almost everything about you
by changing your relations with others and any possessions you 
had before suspension.

Finally, THIS IS A DEFINITION. It is not an axiom or rule of any
kind. Anyone who wishes to propose additions, changes, or alternatives
is welcome to do so.

              Best wishes and long long life for all,

                   Thomas Donaldson

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