>Jonathan Colvin wrote:
>
>> >>While I'm a supporter of Tegmark's Ultimate Ensemble, I think
>> >it is by
>> >>no means clear that just because everything that can happen does 
>> >>happen, there will necessarily be a world where everyone becomes 
>> >>omniscient, or lives for ever, or spends their entire life
>> >dressed in a pink rabbit outfit.
>> >>"Everything that can happen does happen" is not synonymous with 
>> >>"everything we can imagine happening does happen". Worlds
>> >where we live
>> >>forever or become omniscient or are born dressed in a pink
>> >rabbit suit
>> >>may not be *logically possible* worlds. Just as there is 
>no world in 
>> >>the multiverse where 2+2=5, there may be no worlds in the 
>multiverse 
>> >>where I live forever or spend my entire life dressed in a
>> >pink rabbit suit.
>> >>
>> >>Jonathan Colvin
>> >>
>> >Stathis: I don't see this at all. It is not logically possible that 
>> >there is a world where 2+2=5 (although there are lots of 
>worlds where 
>> >everyone shares the delusion that 2+2=5, and for that matter worlds 
>> >where everyone shares the delusion that
>> >2+2=4 while in actual fact 2+2 does equal 5)
>>
>>Isn't that a contradictory statement? "It is not logically possible 
>>that there is a world where 2+2=5" AND "there are lots of 
>worlds where 
>>.... in actual fact 2+2 does equal 5".
>
>Yes, it is contradictory as written. What I should have said 
>was that 2+2= (whatever it actually is) independently of time 
>and space, but while it is not logically possible for this sum 
>to amount to anything else in any world, it is possible that 
>one or more sentient beings in some world are systematically 
>deluded about the value of the sum.
>
>>, but how is it
>> >logically impossible that you live your whole life in a pink rabbit 
>> >suit? If anything, I would rate such worlds as at least on 
>a par with 
>> >the ones where pigs fly, and certainly more common than the ones 
>> >where Hell freezes over.
>>
>>I didn't say that it *was* logically impossible for such a world to 
>>exist; I said that it *might* be that such a world is logically 
>>impossible. Just because we can talk about such a world does not mean 
>>that it is logically possible.
>>
>>Here's a (limited) analogy. If I show you are particular 
>mid-game chess 
>>position, with a certain arrangement of pieces on the board, it is 
>>generally not possible to tell whether the position is a logically 
>>possible chess game (ie. corresponds to a legal chess 
>position) without 
>>knowing the entire history of the game up to that point. There are 
>>certainly particular arrangements of pieces that it is impossible to 
>>reach given the axiomatic starting positions and the rules of chess.
>>
>>It is equally possible, I would suggest, that there *might* 
>be certain 
>>arrangements of matter that will not be reachable in *any* formal 
>>system; universally undecidable propositions, to use a Godelian term. 
>>My pink buny suit universe might be one such.
>>
>>Jonathan Colvin
>
>OK, I agree with this in principle. However, I can't think of 
>any such logically impossible worlds. With quantum tunneling, 
>matter popping into existence from the vacuum, and so on, it 
>really does look like everything conceivable is possible.

At first glance that would seem to be the case. But isn't there a problem?
If we consider worlds to be the propositions of formal systems (as in
Tegmark), then by Godel there should be unprovable propositions (ie. worlds
that are never instantiated). This seems in direct contradiction to the
actual existence of everything conveivable, does it not? 

Jonathan Colvin

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