From: Robin Hanson (rhanson@gmu.edu)
Date: Tue Jun 03 2003 - 06:33:00 MDT
On 6/2/2003, Harvey Newstrom wrote:
>The Doomsday Argument is silly. I don't understand how it can be considered
>a valid use of statistics in the first place. To get an accurate estimate,
>we must pull a random sample from the entire population pool. In the case
>of the Doomsday Argument, which purports to do statistical analysis on all
>populations past and future, we would need to pull random samples from all
>time periods including past and future. Any sampling which does not pull
>examples from the future is incomplete and will skew the measurement toward
>our current time. ...
One of the most interesting thing about the Doomsday Argument is that most
people have a strong negative reaction, yet the arguments they offer against
it are usually much weaker than they realize. Harvey's is no exception.
I find the argument well worth considering, but in the end unpersuasive. I
agree with the published formal critics that the DA neglects what Nick calls
the "Self-Indication Axiom". That is, the DA suggests that you consider the
various possible worlds that there could be, including worlds with varying
numbers of people in them, and suggests that you pick some sort of symmetric
or simple prior over those worlds, but that all the while you assume that
you would have existed no matter what. If you instead allow for the
possibility
that you might have never existed, and pick your symmetric or simple prior
over all worlds, including worlds where you don't exist, there is no DA.
Now Nick (Bostrom) criticizes this approach because it suggests that all else
equal you should think worlds with more people (or creatures that you could
have been) are more likely, and this could greatly favor some cosmological
theories over others. I think Nick too easily conflates possible worlds with
cosmologies; small cosmologies can be in possible worlds with many people
simply by having the world have many of those cosmologies in it.
Robin Hanson rhanson@gmu.edu http://hanson.gmu.edu
Assistant Professor of Economics, George Mason University
MSN 1D3, Carow Hall, Fairfax VA 22030-4444
703-993-2326 FAX: 703-993-2323
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