RE: FIN too

From: Jacques Mallah <>
Date: Fri, 31 Aug 2001 18:45:46 -0400

>From: "Charles Goodwin" <>
>you can't apply any sort of statistical argument to your own experience
>unless you assume that you're a typical observer. But if you do that you're
>just assuming the result you want.

    Not so. You don't assume you're typical exactly, just that you are more
likely to be typical. You have no choice but to believe that, or else you
reject basic Bayesian logic.

>My objections to the QTI are more along the lines of how the mechanism is
>supposed to work - why can't you experience your own death, or just stop
>having experiences altogether, in 99.99999(etc)% of the universes that
>contain you?

    It's nice that you reject FIN! Of course, those who support it can give
(and have given) no reason, since it's a nonsensical belief.

> > From: Jacques Mallah []
>The problem is that the probability isn't 0% that you'd find yourself at
>your current age (according to the QTI - assume I put that after every
>sentence!). Because you HAVE to pass through your current age to reach
>QTI-type ages, the probability of finding yourself at your current age at
>some point is 100%.

    At some point, yes. At a typical point? 0%.

>Using your argument (assuming QTI...) then your chances of finding yourself
>at ANY age would be 0%. This imples to me that the SSA can't be used in
>this case, rather than that QTI *must* be wrong.

    Nope! It's just that with FIN, your expected age diverges. If you want
to say that's impossible, fine with me. FIN is logically impossible for a
sane person to believe!
    But there's one exception: your brain can only hold a limited amount of
information. So it's possible to be too old to remember how old you are.
*Only if you are that old, do you have a right to not reject FIN on these
grounds.* Are you that old?
    (Of course, you must still reject it on other grounds!)

>After all whether QTI is correct or not, you can imagine that it is and see
>what the results would be; and one result is that you will find yourself
>(at some point) having any age from 0 to infinity, which is consistent with
>your current observations.

    Consistent with them, but not nearly as likely in the FIN case.
Remember Bayes' theorem: the posterior favored hypothesis is the one that
would be more likely to predict your observations.

>That's OK so far. And it turns out correctly for most cases (i.e.
>99.99999999(etc)% of observers WILL turn out to have ages of infinity (if
>QTI etc)). But an infinitesimal fraction won't - including everyone you
>observe around you (the multiverse is very very very (keep typing "very"
>til doomsday) big! (assuming MWI)).

    Right. Do you think you are in an infinitesimal fraction, or in a
typical fraction?

> > In the same way, the SSA helps you guess things. It's just a procedure
>to follow which usually helps the people that use it to make correct
>It doesn't seem to help in this case though. I don't need to guess my age,
>it's a given.

    Maybe the following example will help.
    Suppose there are two possibilities:
1. 90% of people see A, 10% see B
2. 10% of people see A, 90% see B

    You see A. But you want to know whether #1 or #2 is true. A priori,
you feel that they are equally likely to be true. Should you throw up your
hands simply because both #1 and #2 are both consistent with your
observation? No. So use Bayes' theorem as follows:

p(1|A) = [p(A|1) p_0(1)] / [p(A|1) p_0(1) + p(A|2) p_0(2)]
       = [ (.9) (.5) ] / [ (.9) (.5) + (.1) (.5) ] = .9

    So you now think #1 is 90% likely to be true, if you use this procedure.
  So you will guess #1. OK, lets try and check to see if this procedure is
If #1 is true then 90% of people who use the procedure guess #1 (right).
If #2 is true then 10% of people who use the procedure guess #1 (wrong).
    Well I'd say that's pretty good, and also the best you can do.
    I gotta go.
                         - - - - - - -
               Jacques Mallah (
         Physicist / Many Worlder / Devil's Advocate
"I know what no one else knows" - 'Runaway Train', Soul Asylum
         My URL:

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Received on Fri Aug 31 2001 - 15:49:07 PDT

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