----- Original Message -----
From: Patrick Leahy <jpl.domain.name.hidden>
To: Alastair Malcolm <amalcolm.domain.name.hidden>
Cc: EverythingList <everything-list.domain.name.hidden>
Sent: 24 May 2005 22:10
Subject: Re: White Rabbit vs. Tegmark
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> This is very reminiscent of Lewis' argument. Have you read his book? IIRC
> he claims that you can't actually put a measure (he probably said: you
> can't define probabilities) on a countably infinite set, precisely because
> of Cantor's pairing arguments. Which seems plausible to me.
It seems to depend on whether one can find an intrinsic ordering (or
something similar), such that relative frequency comes into play (so prime
numbers *would* be less likely to be hit). As implied by my paper this would
suggest a solution to the WR problem, but even if no ordering is possible or
is irrelevant - the simple Cantorian situation - then there would be no WR
problem anyway. (I have read hopefully the relevant passages in 'On the
Plurality of Worlds' - I would think you are mainly referring to section
2.5; he doesn't actually mention either 'measure' or 'probability' here as
far as I can see - more like 'outnumber', 'abundance' etc.)
> Lewis also distinguishes between inductive failure and rubbish universes
> as two different objections to his model. I notice that in your articles
> both you and Russell Standish more or less run these together.
Lewis' approach to the inductive failure objection is slightly different,
with the result that he can deploy a separate argument against it. Where he
says
"Why should the reason everyone has to distrust induction seem more
formidable when the risk of error is understood my way: as the existence of
other worlds wherein our counterparts are deceived? It should not." [p117]
... he is basically saying that from a deductive-logic point of view we have
some degree of mistrust of induction anyway, and this will not be affected
whether we consider the possible worlds (where induction fails) to be real
or imaginary.
However, it is the (for me) straightforward 'induction failure' objection -
that the world should in all likelihood become unpredictable from the next
moment on - that I address in my paper, (which in many ways more
closely links to Lewis's 'rubbish universe' objection); my mentioning of
'rubbish' is in the different context of *invisible* universes, which is in
the appendix argument concerning predomination of simpler universes.
Alastair
Received on Wed May 25 2005 - 12:39:54 PDT