On Thu, Apr 18, 2002 at 05:39:39PM -0700, Brent Meeker wrote: > 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.
Consider what the prediction algorithm would have to do. It basicly has to simulate the entire history of the universe from the beginning until it reaches the point where the subject makes his decision. Now what if the subject has a copy of the algorithm in his brain and tries to run the algorithm on himself? The algorithm would go into an infinite recursion trying to simulate itself simulating itself ... If you have only a finite amount of time and computational power with which to reach a decision, there is no way you can complete a run of the prediction algorithm within that time. So again you have to make the decision without being able to predict your choice from the mathematical description of the universe.