On Thu, 18 Apr 2002, Wei Dai wrote:

> On Thu, Apr 18, 2002 at 04:15:48PM -0700, Brent Meeker wrote:
> > I don't see this.  You seem to be making a proof by contradiction - but I
> > don't see that it works.  There is no contradiction is assuming that there
> > is an algorithm that correctly predicts your decision and then you make
> > that decision.  You only arrive at an apparent contradiction because you
> > suppose the there is some left out part, "the rest of your brain", that
> > was not taken into account by the algorithm.  This is what I meant by
> > incoherent.  All that really follows is that *if* there were such an
> > algorithm you would necessarily do what it predicted.  If the universe is
> > deterministic and computable, such an algorithm must exist.  The only
> > conclusion I see is that if you executed this algorithm you would
> > loose the feeling of free will (of course you would have predicted this).
> I think I stated the idea badly before. Let me state it differently: there
> is no algorithm which given the mathematical description of any universe
> and the location of an intelligent being in it, always predicts his
> decision correctly. Suppose this algorithm exists, then we can construct
> (the mathematical description of) a universe where someone runs the
> algorithm on himself and then does the opposite of what it predicts, which
> is a contradiction.

Keeping to the idea of a deterministic universe - wouldn't the
mathematical description of the universe include a description of the
brain of the subject.  And if the universe is computable it follows that
the behavoir of the subject is computable.  If the person, or anyone else,
runs the algorithm predicting the subjects behavoir - an operation that
will itself occur in the universe and hence is predicted - and *then the
subject doesn't do what is predicted* there is indeed a
contradiction.  But the conclusion is only that one of the assumptions is
wrong.  I'm pointing to the assumption that the subject could "then do
the opposite of what it predicted" - *that* could be wrong.   Thus
saving the other premises.   

Obviously the contradiction originates from assuming a deterministic
universe in which someone can decide to do other than what the
deterministic algorithm of the universe says he will do.

Brent Meeker
Time is the best teacher; Unfortunately it kills all it's students!

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