On Thu, 18 Apr 2002, Wei Dai wrote:
> On Thu, Apr 18, 2002 at 12:26:21PM -0700, Brent Meeker wrote:
> > Perhaps "contradictory" is too strong a word - I should have stuck with
> > "incoherent". But it seems you contemplate having different wishes about
> > the future evolution of the world and you want to find some decision
> > theory that tells you what action to take in order to maximize desirable
> > outcomes. But if the world is already determined, then so are you actions
> > and your decision processes. Thus are actions and decision processes are
> > supposed to be determined in two completely different ways - one at the
> > level of physical processes of the universe, the other at the level of
> > desires and decision theory. These two are not necessarily contradictory,
> > but to avoid contradiction you need to add the constraint on the decision
> > theory you follow that it agree with what your actions are as defined by
> > the mathematical description of the universe.
>
> While you're contemplating a decision, you have no way, even in principle,
> of determining the action that agrees with the mathematical
> description of the universe. Therefore as a normative matter, adding "the
> constraint on the decision theory you follow that it agree with what your
> actions are as defined by the mathematical description of the universe"
> doesn't do anything.

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Exactly. So what does the assumption about the complete mathematical
description add?
> As a positive theory, decision theory is going to be wrong sometimes (e.g.
> not predict what people actually do), but it may be able to make up for
> that with conceptual elegance and simplicity.
Hmm. Maybe I misunderstood your objective. I thought it was to decide
what action to take - not to predict what some person will do.
Brent Meeker
"Imagine the Creator as a low comedian, and at once the world becomes
explicable."
-- HL Mencken