"Hard To Vary" and personal identity
I read and sorta-lightly-reviewed David Deutsch's The Beginning Of Infinity. But in this post I'm going to talk about a tangential question to which it suggested an answer. So this post is my thoughts evoked by Deutsch's book.
Transporters as abattoirs
As a way of introducing the question, I'm going to recount a
conversation that I sometimes hear in nerdspace. It starts with
someone observing that transporters
a la Star Trek "are really
death machines". Why? Because they make a copy and destroy the
original. "They kill you and make an identical twin".
Someone else (usually me) asks socratically, if this twin is so completely identical, what have you lost? Describe any test for this lost thing, other than where the guy is now standing.
The next point in the usual exchange is fraught with exasperation. I'll paraphrase it as this: In our normal experience if the body that we walk around in and whose eyes we see out of is destroyed, that's the end of us.
Then someone observes that in the normal course of events, every atom in our bodies is periodically replaced. Some faster than others, but after a few months, we have been mostly replaced with new material.
"But that's different, it's gradual"
"What's so magical about change being gradual?"
"In the transporter, there's continuity too, of information. All the relevant information reaches the other end. Otherwise it wouldn't know to how rebuild the guy there."
"But you're always conscious"
"What about when you're asleep?"
"You're alive the whole time."
"With Heisenberg uncertainty, on a short enough time-scale you're not really continuously anything."
Various other points are made. Usually this debate gets repetitive and exasperated and ends without a meeting of minds, but with a feeling that "transporters kill you" is simplistic.
And a question is left hanging in the air: Then what exactly is it that we want preserved? We value personal survival. What is X, that if we have it, we have this valuable personal survival, and if we don't have X, we don't?
It's not being materially unchanged. We change atoms all the time.
It's not physically breathing or heart-beating - we all know about coma patients.
It has something to do with being faithfully copied. But it isn't being 100% unchanged. If you could never learn anything new, that wouldn't be perfect, ideal personal survival, it'd be scarcely better than death.
Personal identity is the hardest to vary (to ourselves)
I've already given away a big chunk of the answer. We value the "hard to vary" parts of ourselves. Our atoms aren't hard to vary. Our good parts are. Almost any oxygen will do for breathing. No other set of friends or childhood memories are suitable replacements for our own.
With art, we had to ask what design terrain it was hard to vary in, and the answer seemed to be the audience's perceptive powers. But with personal identity, we are both the art and the audience.
So the criterion is self-referential. Art and explanation didn't have self-referentiality, at least not in the all-consuming way that personal identity does.
So our "hard to vary" criterion has a lot of chicken-and-egg-ness to it. We value aspects of ourselves because we appreciate them in contrast to the possible variants that we perceive - but those perceptions were in turn informed and molded by what we value. It's a path-dependent metric.
Does it fit?
It's a quick stab at a deep problem, so there's plenty of room for this idea to be misguided. But it seems about right. It doesn't fall into the trap of valuing our atoms or our continuous wakefulness, or making a frozen-in-carbonite body our ideal.
The path-dependency fits. Personal identity is full of path-dependent phenomena. Our friends and families are irreplacable to us, but we're not seriously under the impression that had our lives been different and we met another random-ish set of people, those putative other people would all have been second-rate unlike our actual friends and family.
It seems compatible with Wei Dai's observation (can't find the link) that people of all cultures have an abundance of apparently terminal values. At least, it's not obviously suspicious for there to be many hard-to-vary values. On the other hand it doesn't fall into the deontic trap of stipulating a list of terminal values, leaving us to ask "Why those?".
So I find this to be a promising theory of the value in personal identity.