X-Message-Number: 26683
Date: Sun, 24 Jul 2005 09:47:23 -0400
From: Thomas Donaldson <>
Subject: for Mike Perry once more

For Mike Perry once more:

No, I am not describing equivalence as compared to identity. The thing
to remember about mathematics is that it consists of abstract theories
which we apply in different contexts. We apply such theories by 
considering objects, relations, and changes in a real system by 
using one or another abstract theory.

This applies to the notion of "identity" as well as it applies to
other theoretical notions such as "linear" or "addition" or
"multiplication". And thinking this way turns out to be VERY useful.

To move to the notion of identity in human beings, notions of identity
in which I differ fundamentally from myself 1 minutes ago can be 
easily devised. After all, I breathe, fart, and touch things constantly,
and thus bring in new molecules and send out other molecules constantly.
So I am never identical to myself.

In math I raised the notion of two functions being identical even 
when they differed at a countable number of points. How could that make
them identical? Because their integrals, convolutions, Laplace 
transforms, Fourier transforms, and any other operation which integrates
the function when combined with others in any way will come out "the
same" --- again, if the result is a function (for instance) it will
be the identical function (by this definition).

How would the above notion of identity for human beings be useful? If
we really want to study inflow and outflow of energy and materials 
from our bodies, we need ways to distinguish people who normally
would be said to be the same.

Abstract theories should never ever ever be confused with real events.
That makes them MORE useful rather than less. In one sense I am the
"same" person I was when I was 10 years old, in another sense of 
identity I am not the same. WE choose the sense of identity we wish
to use; the only obligation on us when we do so is that we do not
get confused and apply two DIFFERENT senses of identity in talking
about the same subjects. I carry the same genes as I did when I was
10; I carry a subset of the memories I had when I was 10: I remembered
my name as Thomas Donaldson, then and now, recognized my sisters
and parents, and many other features remain the same. Yes, others
have changed, but in the sense of identity I am using right now
I am the "same" person.

No law prevents me also from using a different sense of identity
which says that I am a different person than the person I was when
I was 10. My knowledge and skills in various fields differs from
those I had when I was 10; my body has changed its shape and form
since I was 10. I have diseases and disabilities I did not have
when I was 10. The one point which I should not fail is that I
should distinguish these two senses of identity.

There is no such thing as identity separate from a choice, implicit
or explicit, of the different and same features which define it.
And of course to be reasonable we must try to make such a choice
explicit --- otherwise we will find ourselves tied up in knots
by the different senses of identity we have used.

           Best wishes and long long life for all,

               Thomas Donaldson

Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=26683