Re: Objection to the Doomsday Argument?

Robin Hanson (
Tue, 18 Aug 1998 10:55:00 -0700

Nick B. writes:
>> >The conclusion of the self-indication axiom is even stronger:
>> >if infinite universes are possible, then it is a priori *certain*
>> >that the universe is infinite.
>... read "prob one" and "prob zero" if you want -- you
>still get a heavy conclusion. Do you accept it? That sitting in your
>armchair you can ascertain that the probability that the
>universe is infinite is one? (And it's hard to see how this
>conclusion could be changed by any empirical evidence.)

The conclusion depends on whether I assign a zero or non-zero prob to infinite universes. This "prior" can be "posterior" to other considerations. It's not at all obvious to me that other evidence can't influence this.

This is typical stuff when you have proabilities about infinities; I don't see that this should bother me more here than elsewhere.

Robin Hanson RWJF Health Policy Scholar, Sch. of Public Health 510-643-1884 140 Warren Hall, UC Berkeley, CA 94720-7360 FAX: 510-643-2627