Re: Can anyone explain this to a layman please?

From: Edward Green (spamspamspam3_at_netzero.com)
Date: 12/29/04 

Date: 28 Dec 2004 17:26:30 -0800

whopkins@csd.uwm.edu wrote:

> There is no such thing as "a priori" probability when talking about
the
> whole universe. There only probability for the entire universe is
> after the fact. And that's always 100% -- unless there actually is
no
> universe. So, it's not Uncle Al wrongly conflating things that are
> different: it's you wrongly disflating things that are the same.

Oh, don't be a stick in the mud. There are at least three -- and
counting -- possible interpretations of Hawkings remark as reported by
the OP. There is the possibility that he has some concrete
(mathematical) model of a "big-bang type event" in mind, which happened
to have probabilistic elements. Combined with the assumption he had
some model of "our sort of universe" which lived in the outcome space
of the first model, then the statement is perfectly concrete.

Then there is the pedantic "apostiori probability" of observing our
sort of universe given that we observe our sort of universe. It seems
kind of silly to point this out, but there you have it.

Then there is the possibility that Hawking's "probability" was purely
Bayesian, as Tadchem suggests: that Hawking's subjective prior on our
universe having originated in a big-bang event is 95%.

There may be some point in elucidating these posibilities, posited on
the assumption that there is any point in Usenet discussion, which is a
doubtful premise. But there is no point at all in riding various
academic hobby-horses.

Relevant Pages

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