Re: Objection to the Doomsday Argument?

Nick Bostrom (
Tue, 18 Aug 1998 02:03:47 +0000

Hal Finney wrote: <>

> Doug Bailey, <>, writes:

> > If we apply the Bayesian analysis used by the DA to other classes
> > of objects we get some fairly alarming results. What if we apply
> > the DA to the number of scientific discoveries that have been
> > made? Are we to conclude that virtually all of the discoveries
> > that we have been made have already been made? To conclude
> > otherwise would be to violate the "typical" assumption that's
> > embedded in the current analysis of the DA.

I think Hal explains it very well. I just want to add that if we try to apply the DA to other classes of objects we have to be careful. (Astrophysicist Richard Gott, who independently discovered the doomsday argument, calls this general argument form 'the delta t argument'.) We have to make sure that we are not neglecting some underlying correlation. For example, when I explained the DA to one friend, he asked: "So I should expect that that tree over there will live approximately as long as it has already lived?" Well, that doesn't follow. The reason that tree was selected was that it was big and salient. The young trees in the garden did not have the same chance of being selected.

Nick Bostrom
Department of Philosophy, Logic and Scientific Method London School of Economics