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.

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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.
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.