Re: PhD-thesis on Observational Selection Effects

From: Jacques Mallah <>
Date: Tue, 27 Jun 2000 20:15:48 EDT

>From: "Bostrom,N (pg)" <>
>Hi, I've just submitted my doctoral dissertation titled "Observational
>selection effects and probability", which presents the first mathematically
>explicit "observation theory". I use it to resolve a range of puzzles
>related to the "anthropic principles", multiverse models, the Doomsday
>argument, etc. The text is available at
> as a MS-Word-file (77,000 words; 1.2
>KB). The abstract is pasted below. Any constructive comments, criticism or
>suggestions would be welcome. (I'm planning to write this up as a book
>accessible to a wider interdisciplinary audience, so your input would be
>come to good use.)
>Most of you who get this message will have helped me in one way or another
>during the PhD-process. I would like to say a warm Thanks! to all of you.

    Hello. First, I appreciate being acknowledged. The order must be that
of importance :)
    The paper is too verbose for may taste, already a book, but I realize
that could be due to pressure from a redundancy Ėloving professor like one I
had to deal with. I read the parts that looked most interesting.
    Now for some (hopefully constructive) criticism. First, you say your
paper presents the first mathematically explicit ďobservation theoryĒ. No
doubt a standard literature search would confirm that, convincing the old
fogies. On the everything-list and some memberís web pages, though, the SSA
is old hat. I checked and I have to admit that it was you who introduced
the term ďSSAĒ onto the list. By now though there are two long-opposed
camps, the ASSA (correct) and RSSA (idiotic). Despite the length of your
paper, I noticed you didnít discuss your view on that.
    The idea, however, is one I (and no doubt others) understood well before
I even heard of the list. Itís how Iíve always read Everett; to me he was
the first ASSAer. Youíve seen my web page discussion of the anthropic
principle (; it has
significant overlap with your paper. I might like to expand it into an
article sometime, maybe by throwing in a refutation of the RSSA. Come to
think of it, Don Pageís work (
touches on some of the same things.
    Really, this is fine because we all need to work. I guess Iím just
wondering how this is all supposed to be done properly, but still letting us
all look good :)

>It has applications in cosmology, evolutionary biology, thermodynamics and
>the problem of time's arrow, game theoretic problems with imperfect recall,
>the philosophical evaluation of the many-worlds and many-minds
>interpretations of quantum mechanics and David Lewis' modal realism, and
>even for traffic planning.

    I would have liked to see some discussion of each application. I guess
thatís for the book. Also, you could have included the stuff you and I
discussed about how the using the MWI prevents some of the counterintuitive
consequences (e.g. regarding Adam.)

>However, we discover new consequences of SSA that are more counterintuitive
>than the Doomsday argument. Using these results, we construct a version of
>SSA that avoids the paradoxes and does not lead to the Doomsday argument
>but caters to legitimate methodological needs.

    Hereís the part I really object to. Your SSA was vague (you didnít even
discuss observer-moments up to that point), but was OK as far as it went.
When you introduced the SSSA, you went off track. Your SSSA gives obviously
wrong results, such as not leading to the Doomsday argument and in the
ďgodís coin tossĒ where it gives the wrong Bayesian probability for the
coin. Nor is there any theoretical justification for not regarding all
observer-moments to be in the same reference class. (As you can tell I am
partial to the ASSA.)
    You might then ask how I would avoid the Adam-style problem. The answer
is already somewhere in the paper: if Adam is a freak, we donít need to
worry much about him. Itís in the nature of Bayesian probability that for
some people the method must backfire. And of course for most practical
applications, the MWI would come to the rescue.

                         - - - - - - -
               Jacques Mallah (
         Physicist / Many Worlder / Devil's Advocate
"I know what no one else knows" - 'Runaway Train', Soul Asylum
         My URL:

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Received on Tue Jun 27 2000 - 17:30:15 PDT

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