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.


--Stathis Papaioannou

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