This discussion reminds me of a fantastic short story by Greg Egan called "The Infinite Assassin." You can find it in a short story collection called Axiomatic. Unfortunately, Amazon.com lists it as being out of print, but you might be able to find a copy at a used bookstore or lurking unsold on the shelf of one of the non-super bookstore chains.
Here are a few paragraphs.
One thing never changes: when some mutant junkie on S starts shuffling reality, it's always me they send into the whirlpool to put things right.
Why? They tell me I'm stable. Reliable. Dependable. After each debriefing, The Company's psychologists (complete strangers, every time) shake their heads in astonishment at their printouts, and tell me that I'm exactly the same person as when "I" went in.
The number of parallel worlds is uncountably infinite--infinite like the real numbers, not merely like the integers--making it difficult to quantify these things without elaborate mathematical definitions, but roughly speaking, it seems that I'm unusually invariant: more alike from world to world than most people are. How alike? In how many worlds? Enough to be useful. Enough to do the job.
How The Company know this, how they found me, I've never been told. I was recruited at the age of nineteen. Bribed. Trained. Brainwashed, I suppose. Sometimes I wonder if my stability has anything to do with me; maybe the real constant is the way I've been prepared. Maybe an infinite number of different people, put through the same process, would all emerge the same. Have all emerged the same. I don't know.
(later in the story)
Intelligence says there's some kind of whirlpool cult in Leightown, who may try to interfere with my work. I've been warned of such groups before, but it's never come to anything; the slightest shift in reality is usually all it takes to make such an aberration vanish. The Company, the ghettos, are the stable responses to S; everything else seems to be highly conditional. Still, I shouldn't be complacent. Even if these cults can have no significant impact on the mission as a whole, no doubt they have killed some versions of me in the past, and I don't want it to be my turn, this time. I know that an infinite number of versions of me would survive--some whose only difference from me would be that they had survived--so perhaps I ought to be entirely untroubled by the thought of death.
But I'm not.
(and much later)
As for heading straight for the building where my "informant" claims the mutant is dreaming, I'm not tempted at all. Whether or not the information is genuine, I doubt very much that I've received the tip-off in any but an insignificant portion--technically, a set of measure zero--of the worlds caught up in the whirlpool. Any action taken only in such a sparse set of worlds would be totally ineffectual in terms of disrupting the flow.
If I'm right, then of course it makes no difference what I do; if all the versions of me who received the tip-off simply marched out of the whirlpool, it would have no impact on the mission. A set of measure zero wouldn't be missed. But my actions, as an individual, are always irrelevant in that sense; if I and I alone, deserted, the loss would be infinitesimal. The catch is, I could never know that I was acting alone.
And the truth is, versions of me probably have deserted; however stable my personality, it's hard to believe that there are no valid quantum permutations entailing such an action. Whatever the physically possible choices are, my alter egos have made--and will continue to make--every single one of them. My stability lies in the distribution, and the relative density, of all these branches--in the shape of a static, preordained structure. Free will is a rationalization; I can't help making all the right decisions. And all the wrong ones.
But I "prefer" (granting meaning to the word) not to think this way too often. The only sane approach is to think of myself as one free agent of many, and to "strive" for coherence; to ignore short cuts, to stick to procedure, to "do everything I can" to concentrate my presence.
As for worrying about those alter egos who desert, or fail, or die, there's a simple solution: I disown them. It's up to me to define my identity any way I like. I may be forced to accept my multiplicity, but the borders are mine to draw. "I" am those who survive, and succeed. The rest are someone else.
Eric Boyd wrote:
> Hi,
>
> Dylan Durst <ddurst@levien.com> writes:
>
> <<
> You['re] still only able to make one choice. In retrospect, the only
> 'choice' you could have made is the one you did, since that is all you
> did 'choose'. Any other choice would have required a different brain
> with different memories, reactions and calculations. It would not have
> to be much different, but it would not be the same.
>
> Ramble/note to self:
> Does the idea of 'choice' stem/relate to the idea of 'linear time'?
> >>
>
> Yes! I'll take this opportunity to recommend the book I just read to
> all Virians:
>
> The Fabric of Reality, by David Deutsch.
>
> It is an attempt to see how deep an explaination of our universe our
> four most fundamental theories in science can give, if we take those
> theories seriously. His "four main strands" of explaination are
>
> (1) Quantum theory
> (2) The theory of evolution
> (3) Epistemology (specifically Popper's evolutationary theories based
> on conjecture and refutation of explainations)
> (4) The theory of computation.
>
> It is, above all, a book about the multi-verse hypothesis, and it's
> implications in the other related fields.
>
> So yes -- the idea of choice does not relate to linear time. In a
> Newtonian universe, choice is impossible, becuase the future is
> *determined* by the past. So choice has a negative relationship to
> linear time: it reveals that linear time is an incorrect explaination
> of reality.
>
> In a quantum multi-verse, choice is the essence of *your* universe.
> (since *everything* happens, what we experience is entirely determined
> by our choices -- they determine which states of the multi-verse your
> "universe" or "space-time" will include)
>
> I'll transcribe his little table on this subject:
>
> sentence:
> "After careful thought I chose to do X"
> meaning in the multi-verse:
> "After careful thought, some copies of me, including the one speaking,
> chose to do X"
>
> sentence:
> "I could have chosen otherwise"
> meaning in the multi-verse:
> "Other copies of me chose otherwise"
>
> sentence:
> "It was the right decision"
> meaning in the multi-verse:
> "Representations of the moral or aesthetic values that are reflected
> in my choice of option X are repeated much more widely in the
> multiverse than representations of rival values."
>
> sentence:
> "I am good at making choices"
> meaning in the multi-verse:
> "The copies of me who chose X, and who chose rightly in other such
> situations, greatly out number those who did not"
>
> ERiC