[extropy-chat] Re: cryonics (was: Science and Fools)

Hal Finney hal at finney.org
Thu Mar 24 18:43:34 UTC 2005

I have two problems with the notion of "identity as continuity", which
suggests that even an apparently successful cryonics revival would be
a new person who is a mere copy of the old one.

The first problem is that this view tends to see identity in black and
white terms.  Either some future person is the same identity as me, or
they are not.  There is no room for the idea of someone being partially
the same identity as me, say 90% or 30% or some other percentage.
Instead, in this view there is an actual "fact of the matter" about
whether someone is the same identity as me.  It's not just a matter of
definition or perspective.  If my future replacement's identity is not
the same as mine, then I have died in a real, factual sense.

The problem is that this position is vulnerable to a sorites attack.
This is the greek paradox which says that day turns gradually into
night, you can never identify an instant at which it ceases to be day
and becomes night, yet day seems fundamentally different from night.
The resolution to this paradox is to recognize that day is actually
not fundamentally different from night, but that both are simply the
same thing, to different degrees.  Day has more sunlight than night,
and there is a gradual change in the amount of sunlight between them.

In the case of identity, it is possible to set up a series of thought
experiments which provide a similar gradual degree of changes between
situations where identity is preserved and where identity is lost.
For example, if someone believes their identity would be lost if the
atoms in their brain ceased motion by being frozen, you can imagine a
series of cases in which the atoms are merely cooled to different degrees.
When they are not cooled at all, identity is preserved.  When they are
cooled all the way, identity is lost.  And there are an essentially
infinite degree of gradations between the two.  It seems inconceivable
that identity will be preserved at one temperature, but completely lost
at an infinitesimally lower temperature.

If someone is OK with freezing but is concerned about disassembly and
reassembly, we can similarly imagine a series of cases where different
numbers of atoms are removed and replaced, from none to all of them.
Most other models for identity can be attacked in the same way.

The point is that any boolean or binary notion of identity is inconsistent
with the nature of reality, which is essentially continuous and "sloppy".
The apparently discrete and fixed nature of our identity is something of
an illusion, and as we pursue these thought experiments it is easy to
show that the seemingly sharp dividing line between systems that share
our identity and those that don't is actually blurred and fuzzy.

That's the first problem I have with this view.  The other is somewhat
related in that it also has to do with the discrete nature of identity
and the position that certain transformations preserve it completely,
while others destroy it 100%.

The problem is that there is apparently no objective way to measure,
detect or report the degree of identity preservation in a transformation.
There is no identity meter that we can attach to a brain.  Not only
are there no objective ways to detect it, it is apparently not even
subjectively perceivable.  You can imagine a cryonics patient who wakes up
and thinks he is the same person he was before.  All of his memories and
personality traits are the same as the person was before he was frozen.
Yet, to a believer in this model of identity, he is not the same person.
But he can't detect this fact by introspection.  He doesn't feel the
loss of identity.  Only by philosophical reasoning can he deduce that
his identity must have changed and that the original person was dead.

The problem is that, if we believe that there is an actual fact of the
matter about whether identity is preserved through some transformation,
we might be wrong about what transformations are OK.  And there would
be no way to tell if we are wrong!  We can't tell objectively and we
can't tell subjectively.

Worse, since identity preservation has no objective or subjective
consequences, there is no reason for evolution to have made identity
preservation a priority.  If we accept the possibility that we are wrong
about the facts, and add the absence of any evolutionary pressure to
make identity preservation match our desires, it is entirely possible
that our identities are far more fragile than we suppose.  What would
stop our identity from being lost every night when we go to sleep, with
us having a new identity in the morning?  How could we be sure that this
is not happening?  Nothing in our perception or memories upon awakening
would give us a clue.

Or even worse, what if our identities are not even being preserved from
second to second?  What if every second, we (in some sense) die and
are replaced by a new person?  We wouldn't even know!  Yet, throughout
the world, a terrible tragedy is occuring on a scale so vast that we can
barely imagine it (balanced by the equally marvelous miracle of new birth,
I suppose).

The problem, then, is that it is philosophically fragile to to adhere
to a model of identity which has no objective or subjective effects.
There are too many possibilities, none of which can be ruled out by any
conceivable experiment or perception.  This is not a basis for making
decisions about actions.

These are the problems I have with this simple model of identity.
The first can be dealt with by going to a more sophisticated, gradual
model, based on degrees of identity.  However, this may be unattractive
for those who prefer the simple and clean view of yes-or-no identity,
which in some ways matches our naive perceptions.  The second is harder
to deal with because it goes directly to the abstract and imperceivable
nature of identity.  If not even the possessor of an identity can tell
when it is lost, does it really exist enough that it should be a guideline
for actions?


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