From: Nick Bostrom (bostrom@ndirect.co.uk)
Date: Tue Aug 25 1998 - 12:50:10 MDT
Lee Daniel Crocker wrote:
> A realistic
> set of propositions would be something more like {there will be fewer
> than 100 billion persons, there will be 100-200 billion persons, there
> will be 200-300 billion persons, ...} up to a suitable upper bound
> chosen empirically based on the size of the planet or universe.
> Without changing the results, this is equivalent to a set of urns with
> {1 ball, 2 balls, 3 balls, ... N balls}, where N is the multiple of
> 100 billion persons we choose as our upper limit. If we then assign
> equal initial probabilities to each of those urns
For the purposes of the DA, we should assign "priors" given by
empirical considerations. Korb and Oliver had a similar point like
the one you are making here. (I have a more detailed reply in "Alive
and Kicking" (http://www.hedweb.com/nickb/doomsday).)
> Let's say we had such evidence--that advanced
> civilizations really seemed to grow to a random size from 100 billion
> to 100 billion billion, and then collapse.
Then the no outsider requirement is not satisfied and the DA is
weakened in proportion to the number of existing alien civilizaions.
> Would the fact that we
> find ourselves numbering less than 100 billion truly give us reason
> to suspect we are among the unfortunate slated to perish soon? That
> depends upon whether or not the question is being asked by someone
> who _fairly chose our civilization to pick on_ by offering this bet.
In a sense you are betting against yourself when you decide how to
plan your life in view of your estimates of how long our species will
survive.
_____________________________________________________
Nick Bostrom
Department of Philosophy, Logic and Scientific Method
London School of Economics
http://www.hedweb.com/nickb n.bostrom@lse.ac.uk
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