Re: Objection to the Doomsday Argument?

From: Hal Finney (hal@rain.org)
Date: Fri Aug 14 1998 - 13:31:10 MDT


Doug Bailey, <Doug.Bailey@ey.com>, writes:
>
> Thanks for the comments Nick. I think what I am attempting
> to articulate is that I don't see how any species can apply
> the DA and not conclude that its extinction is imminent. Can you
> provide details or characteristics of an entity and its species
> where the entity could apply the DA to its situation and not
> reach the "doom" conclusion?

Many times I've convinced myself that I have a refutation for the DA,
only to decide on further consideration that it is more difficult than
it seems.

In this case I think Doug's comment is correct, although it is not
a matter of a "species" applying the DA but rather a member of the
species.

However the point is that for most members of most species, the conclusion
is correct. For most of them, it is true that they are about in the middle
of the set of members of their species. That's just the law of averages.
So of all those species members who apply the DA to conclude that "doom
is imminent" (specifically, that they are about halfway along in the
membership of their species), most of them are correct.

One possible escape, then, is to suggest that we are special because
we are living in the time when the DA was just recently discovered.
We are not a typical member of a long-lived species who learns about a
DA which was discovered ages ago. If we were then it would be correct
that the odds are that we are halfway along the species' existence. But
we are not a random selection, we are special because this is the first
era when the DA has been discovered. Every species must go through such
an era, and for those observers who live in exactly that era, it tells
them nothing about the expected time remaining for their species.

This argument would be a bit stronger if the DA had been discovered more
recently. However it has only been popularized within the last couple of
years and so we really are the first people to be faced with it.

I don't care for formulations of the DA which act as though I might
have been born at different times. This raises thorny problems about
the meaning of identity, whether I could be said to be the same person
if I were born thousands of years in the future.

Rather, it is simpler to say that for most observers the DA will be valid.
However, it will not be valid for those observers who are specially chosen
as being part of a certain milestone in the history of their race - the
discovery of fire, or of writing, or of the DA. You can easily imagine
that the universe is such that most species do not discover fire halfway
along their history, and the same reasoning applies to the discovery of
the DA.

Hal



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