Re: against UD+ASSA, part 1

From: Jesse Mazer <>
Date: Tue, 02 Oct 2007 17:59:57 -0400

Pete Carlton wrote:
>>>Since barring global disaster there will be massively more observers
>>>in the future, why did you find yourself born so early? Surely your
>>>probability of being born in the future (where there are far more
>>>observers) was much much higher than your chances of being born so
>>>early among a far smaller pool of observers?
>Isn't there a major problem here with the word "you" here? To whom or what
>is it referring?
>If it is asking "Why did you, Brent, a man born in the 20th century, find
>yourself born in the 20th century?", then the answer is obvious; it's like
>asking why is twelve twelve, and not a thousand. You're not picking a
>number randomly when you ask "Why is twelve twelve?" - you're picking
>The target of your question (Brent) indeed lives at a time with a
>relatively small number of observers - if you want to talk about how
>things are in the future, maybe you should ask someone in the future...

The self-sampling assumption just argues that you are likely to get correct
conclusions if you reason *as if* you were randomly picked from the set of
all observers, not that "you" really were assigned a life randomly in some
ultimate metaphysical sense. The issue is discussed on the FAQ at, where Bostrom write:

Q3. I have memories of 20th century events, so I cannot have been born
earlier than the 20th century.

A3. We have to distinguish two "cannots" here. (1) Given the validity of
these memories then I was in fact not born <1900.[true] (2) I could not
exist without these memories.[much more doubtful].

It is indeed problematic how and in what sense you could be said to be a
random sample, and from which class you should consider yourself as having
been sampled (this is "the problem of the reference class"). Still, we seem
forced by arguments such as Leslie's emerald example (below) or my own
amnesia chamber thought experiment (see my "Investigations into the Doomsday
argument" [ ]) to
consider ourselves as random samples due to observer self-selection at least
in some cases.

>A firm plan was formed to rear humans in two batches: the first batch to be
>of three humans of one >sex, the second of five thousand of the other sex.
>The plan called for rearing the first batch in one >century. Many centuries
>later, the five thousand humans of the other sex would be reared. Imagine
> >that you learn you're one of the humans in question. You don't know which
>centuries the plan >specified, but you are aware of being female. You very
>reasonably conclude that the large batch was >to be female, almost
>certainly. If adopted by every human in the experiment, the policy of
>betting >that the large batch was of the same sex as oneself would yield
>only three failures and five thousand >successes. ... [Y]ou mustn't say:
>'My genes are female, so I have to observe myself to be female, no >matter
>whether the female batch was to be small or large. Hence I can have no
>special reason for >believing it was to be large.' (Leslie 1996, pp.

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Received on Tue Oct 02 2007 - 18:00:22 PDT

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