From: Quentin Anciaux <[EMAIL PROTECTED]>
Subject: Measure, Doomsday argument
Date: Mon, 20 Jun 2005 23:37:45 +0200

Hi everyone,

I have some questions about measure...

As I understand the DA, it is based on conditionnal probabilities. To somehow
calculate the "chance" on doom soon or doom late. An observer should reason
as if he is a random observer from the "class" of observer.

The conditionnal probabilities come from the fact, that the observer find that
he is the sixty billions and something observer to be "born". Discover this
fact, this increase the probability of doom soon. The probability is
increased because if doom late is the case, the probability to find myself in a universe where billions of billions of observer are present is greater but
I know that I'm the sixty billions and something observer.

I always thought the DA was understood in terms of absolute probability, not conditional probability. Conditional probability is supposed to tell you, given your current observer-moment, what the probability of various possible "next" experiences is for you; absolute probability is supposed to give the probability of experiencing one observer-moment vs. another *now*. The DA is based on assuming my current observer-moment is randomly sampled from the set of all observer-moments (possibly weighted by their absolute probability, although some people reason as if each observer-moment is equally likely for the purposes of the random-sampling assumption), and noting that if civilization were to be very long-lasting, it'd be unlikely to randomly choose an observer-moment of a person so close to the beginning of civilization.


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