Re: zombie wives

From: Christopher Maloney <>
Date: Fri, 13 Aug 1999 22:36:08 -0400

Grudging kudos to Jacques for seeing where this question came from,
and its connection to the Quantum Suicide experiment. I haven't posted
any follow-ups for a while because I still find the whole thing quite

I agree that the concept "that one's measure is somehow distributed
among the so called computational continuations of one's brain activity"
leads inevitably to the concept of near-zombies. The description of
making a million copies of one person is a good illustration. Each of
those copies has only a one millionth chance of "being" the original
person, so we should not be as concerned when one of those dies as
when someone else, who has never been copied, dies. But is this a
refutation of the concept, by reductio-ad-absurdum? I don't think so.

I want to clarify one thing, though, in Jacques' post:

"Jacques M. Mallah" wrote:
> On Fri, 13 Aug 1999, Russell Standish wrote:
> > > referring to
> > > > t0 |
> > > > |
> > > > t1 T / \ H
> > > > / \
> > > > t2 / / \
> > > > | | \
> > > > t3 Y R B
> > >
> > > Assume that all three branches occur (two copying events).

If there are two copying events, then there is no place for a coin
toss to enter into the experiment, so the 'T' and 'H' should be
erased from the diagram. The point is still made that, at time t0,
Jane would figure:
    P(left branch, t1) = 1/2, P(right branch, t1) = 1/2
    P(Y, t3) = 1/2, P(R, t3) = 1/4, P(B, t3) = 1/4

Which would imply that the two copies of her that saw red and blue
would be less likely to be the same Jane at t0, so in some sense,
they would be less human, you might say.

Getting back to the original problem, I can think of six possible
resolutions (can anyone add to this list):

  1. The term "subjective probability" is meaningless.
      This seems to be what Wei has said, and I think I understand
      Hal to have weighed in likewise. :)

      One thing that Hal said was that we might not be able to expect
      to be able to determine the subjective probabilities given this
      particular problem, because we have no experience with copy
      machines. But we do have experience with something similar,
      "anti-copy" machines. People die all the time! According to
      Jacques, each of us can expect to die. Yet we still expect that
      we should be able to predict subjective probabilities. That's
      what physics is all about, and it seems to work pretty well.

  2. The term "subjective probability" is meaningful, but given the
      problem as stated, there is not enough information to determine

      This may be true, but I can't imagine what other information
      might make the problem tractible.

  3. Subjective probabilities can be computed, but the assumption
      that consciousness can "flow" to a continuation independent of
      time or space is flawed.

      This, I think, is Jacques' point of
      view. Though he didn't state it, I would guess that he would
      say that
          P(H, t1) = P(H, t2) = P(H, t3) = 1/2,
      and that the original Jane would necessarily feel herself to
      continue along with her original body. That is, if, in the
      above diagram, at the copying event after Jane sees Heads, we
      assume that the original Jane is the one who is shown the Red
      card, then Jane at t1 would say
          P(R) = 1, P(B) = 0
      The copy of Jane who sees the blue card is a new person, who
      was just "born" at the instant the copy was made, even though
      she has all the same memories as the original.

      If, as I suggested, the original is destroyed, and two copies
      are made, then alas, poor Jane is dead!

      I reject this option, because it seems like Cartesian dualism
      to me, to assume that there is some sort of magical res-cogitans
      that stays with the body.

  4. Subjective probabilities can be computed on the basis of the
      Strong SSA, and we get
          P(H, t1) = 1/2
          P(H, t2) = P(H, t3) = 2/3
      If this is the case, then I think we have to throw Tegmark's
      scheme using Bayesian statistics out the window. This option
      has severe metaphysical problems, though, in my opinion. I
      think Hal was saying, in his post, either this option, or
      option 1 above, but I'm not sure.
  5. Subjective probabilities can be computed, and we should expect
      the common-sense results
          P(H, t1) = 1/2
          P(H, t2) = P(H, t3) = 1/2

      It's a fair coin, after all, right?
      I think this gets Gilles' and Bruno's vote (and Russell's?)

  6. Subjective probabilities can be computed, and we should expect
      the nonsensical results
          P(H, t1) = 2/3
          P(H, t2) = P(H, t3) = 2/3
      This is what I believe is probably true. I think that there
      must be a sort of "reverse causality" at work, which would
      increase the measure of the right branch of Jane at time t1
      (the branch that sees heads, but before the copy is made).

      This still has Jacques' problem of allowing pseudo-zombies.
      If we switch to Jacques' example and assume two copying events,
      then the Jane on the left branch, at time t1, would have less
      measure than the Jane on the right (note the contrast between
      this result and the previous, where the Janes that were the
      product of the second copying operation were accorded less

      But I don't see this as a problem. What I'm suggesting is that
      each human alive today has a varying amount of "measure". It's
      incorrect to assume that each person, when they are born, is
      given a single "measure unit". By my scheme, a person with a
      terminal illness with only a few days to live would have a
      very small measure of existence, relative to others.

      I can't help wondering, often, why I find myself to be the
      particular human I am. Do you others wonder this? One thought
      I've had (please don't laugh at me too badly) is that the fact
      that I have a pretty poor memory might be significant. If I
      had a better memory, then my measure would be less, because
      fewer universes could have given rise to me. Of course, this
      reasoning probably won't work for you, but that doesn't make it
      any less valid from my perspective, which is the only one I

      I came to believe in this "reverse causality" while pondering
      the QS project I wrote about before. I started to expect that
      things would crop up in my way to prevent my being able to
      complete the project, before it came to fruition. It didn't
      (and it still doesn't) make sense to me that the measure of all
      my branches should be unaffected until the very instant that I
      carry out the experiment. Because if the assumption that I'll
      be alive after the experiment date is correct, then I can expect
      to have memories at that time of somehow having escaped. And
      I should, in general, expect to have a memory of "the most
      likely" escape route, or of one of the most likely ones, if there
      are several that are near-equally likely.

      But how can one reconcile that with the concept of continuity of
      consciousness from moment to moment? Only if there is a reverse
      causality at work.
      This theory has significant and testable implications. Viz: we
      should expect to find ourselves in a universe that will allow us
      to live forever. I.e. this leads directly to the requirement
      that the FAP is true. Just consider if time t1 and t2 are
      separated by a larger and larger time span. Consider also that
      those branches in which we cease to exist also tend to decrease
      the measure of all the observer-moments in previous subjective

      Basically, the measure of our observer-moments at the next
      instant in subjective time are weighted as the number of continous
      paths from that observer-moment to the "Omega-point". This is
      my crackpot theory. Though it's certainly hard to justify on the
      basis of the SSA on a moment-by-moment basis (the Strong SSA), I
      haven't yet found anything that contradicts it. I know that's
      not good enough, but anyway I find it the most satisfying
      result of the above thought experiment. All the other possibilities
      are problematic.

Chris Maloney
"Donuts are so sweet and tasty."
-- Homer Simpson
Received on Fri Aug 13 1999 - 19:54:08 PDT

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