Re: modal logic and possible worlds

From: Bruno Marchal <marchal.domain.name.hidden>
Date: Mon, 19 Aug 2002 16:27:56 +0200

George Levy wrote:



>I have been following the latest very scholarly exchange involving
>different logical models in relation to the MWI, however I fail to
>see how it relates to my own perception of the world and my own
>consciousness unless I think according to those formal systems which
>I think is unlikely.
>
>Using different logical models to describe possible worlds is
>interesting but isn't it true that if the problem of consciousness
>(as an observer, and definer, for these worlds) is to be addressed,
>then the only logic that matters is the one in my, or in your, own
>head? Of all these logical models which one is the "right" one? Are
>all of them "right?"


One thing is sure. Those modal logics are right for the consistent machines.
This is essentially what Godel (followed by Lob, ...) proves.
The rest is a matter of definition.
Can we find those logic by pure introspection? The S4 first person: yes (it
happens all the time from Heraclite to "toposes" ...
The G and G* logics? Not at all, they formalize by construction the most
counter-intuitive feature of the computationalist hypothesis.


>When Copernicus formulated the heliocentric system, he didn't go
>around saying that a "new" logic had to be used to explain the
>central position of the sun. He simply used a physical model. People
>just had to accept the new paradigm that the Earth "moves" even
>though they do not feel the Earth move. Can't we just accept the
>fact that the world - and our consciousness - "split" or "merge"
>even though we do not feel them "split" and "merge?" It seems to me
>that if we define a good physical model, then classical probability
>could do the job of formulating the decision theory desired by Wei.


I think all the problem relies in the question "what is a physical model"?
Even what is a "physical reality"? Does that exists in some absolute sense?
With the comp hyp, that's doubtful, as I am used to argue.
I think this is coherent with your relativism, as we concluded before,
independently of comp!

Bruno
Received on Mon Aug 19 2002 - 07:34:54 PDT