Picking up a thread from a little while ago: >>Jonathan Colvin: That's a good question. I can think of a chess position that is >>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 purely random? 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. Jonathan Colvin
