From: Nick Bostrom (bostrom@ndirect.co.uk)
Date: Mon Aug 31 1998 - 11:53:55 MDT
Ok, I'll try to summarize my position too.
The doomsday argument is a one application among many others of the
anthropic principle. The DA, as I understand it, does not show that
doom is likely to strike soon. What the DA does is place
interesting constraints on what views of the future and of the
universe at large are tenable. To assume an impending doomsday is one
way of taking account of the DA, but at least at our present level of
understanding there seem to be alternative interpretations, some of
which may (hopefully) fit with the transhumanist vision of the
future. Further analysis is required before we can say anything more
specific than that.
I think Robins' position can be characterized as follows: He accepts
what I call the self-indication axiom (SIA) and he thinks that also
non-observers should be included in the reference class.
As for the SIA, I think it is consistent to accept it. There are
problems - the problem with infinities and the no coincidence
argument - that I think seriously detract from the plausibility of
the SIA. But these counterarguments are inconclusive, and I do not
rule out the possibility that the SIA should be accepted. The
difference between Robin and me here seem to be one of degree of
belief or disbelief in the SIA.
Robin's view that we should include non-observers in the reference
class, on the other hand, seems incoherent to me. I have raised
several objections against this, including the
who's-the-apple-and-who's-the-pear problem. Two additional
difficulties with this view also occured to me yesterday:
(1) Using a meta-level argument: If there are all these other
inanimate objects in the reference class, how comes you are not one
of them? If you were equally likely to turn out to be a grain of
sand as an observer, then you finding yourself to be an observer
would have been extremely unlikely.
(2) What exactly are the members in the reference class supposed to
be? Are the bacteria in your body separate members or are they only
there as a part of you? If only fundamental particles are members,
then you couldn't have been a human since a human is not a particle.
Which chunks or entities count as individuals?
So I definitely do not think you can solve the reference class
problem by including non-observers. It is still unclear, however,
exactly what (e.g. posthumans?) should be included, and that is
perhaps the biggest remaining philosophical problem in anthropic
reasoning.
Nick Bostrom
http://www.hedweb.com/nickb n.bostrom@lse.ac.uk
Department of Philosophy, Logic and Scientific Method
London School of Economics
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