RE: Self Sampling Assumption (was: my objection to the Doomsday argument)

From: gts (gts_2000@yahoo.com)
Date: Tue Apr 29 2003 - 20:51:58 MDT

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    Ramez Naam wrote:

    > From: gts [mailto:gts_2000@yahoo.com]

    >> If SSA is false then DA fails immediately, but then so do a lot of
    >> common sense ideas that we take as obvious fact. And therein
    >> lies the rub.
    >
    > So what is there to support the Self Sampling Assumption?

    Let's start with this example (I'm making this example up as I write):

    You and 99 other people are standing shoulder to shoulder in a line. Someone
    from behind the line places green or yellow hats on the heads of everyone in
    the line, including you. You and everyone else in the line are now sporting
    a hat, but none of you know which color of hat you have, and none of you
    know the colors of the hats of others.

    All you know is that 90% of the hats are green.

    Now someone asks you to guess the color of your own hat.

    Would you guess green? Of course you would. You would reason that given that
    you are a random sample of the 100 people in the line, and that given that
    90% of the hats are green, you are very likely to be wearing a green hat.
    You made this guess using the Self-Sampling Assumption (SSA). And you were
    right to make that guess.

    > In particular, what is there to support the assumption that
    > you are a random sample from a population that includes
    > *future* sentients not yet born?

    Okay, now imagine that 1,000,000,000 people will join the line at some
    distant future time. Everyone will lose their hats at that future time, but
    everyone will then be given new hats in the same ratio of green to yellow.
    After those people are added and given hats you will be asked once again to
    guess the color of your own hat. Someone asks you now (before the extra
    people are added) if you plan to change your guess from green to yellow.
    Will you change your guess? Of course not. 90% of all people ever to join
    the line will have green hats. You will continue to abide by the
    Self-Sampling Assumption (SSA) even despite the fact that most people
    in the sample are not yet born.

    -gts

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