Picking up a thread from a little while ago:
>>Jonathan Colvin: That's a good question. I can think of a chess position
>>a-priori illegal. But our macroscopic world is so complex it is far
>>from obvious what is allowed and what is forbidden.
>Jesse Mazer: So what if some chess position is illegal? They are only
>illegal according to the rules of chess, but the point of the
>"all logically possible worlds exist" idea is not just that
>all possible worlds consistent with a given set of rules (such
>as our universe's laws of physics) exist, but that all
>possible worlds consistent with all logically possible *rules*
>exist. So the only configurations that would be forbidden
>would be logically impossible ones like "square A4 both does
>and does not contain a pawn".
Pondering on this, it raises an interesting question. Can we differentiate
between worlds that are (or appear to be) rule-based, and those that are
I think it is suggested that any non-contradictory universe (or
world-history) has a finite chance of appearing by chance (randomly
tunneling out of a black hole for instance).
But can we call a purely random universe "rule based"? What is the rule?
Randomness is non rule-based by definition, so the idea of a rule-based
random universe seems a contradiction.