Re: Possible Worlds, Logic, and MWI

From: Tim May <tcmay.domain.name.hidden>
Date: Sat, 11 Jan 2003 09:51:20 -0800

On Saturday, January 11, 2003, at 01:39 AM, Eric Hawthorne wrote:

> This strict "anonymous symbols" interpretation
> is how one must treat formal logic and propositions
> expressed in formal logic too. Every time
> I read someone bemoaning how logic has difficulty with
> expressing "what is going to happen in future", I think,
> why would you expect a formal system of symbols to have
> anything to do with future time in reality?

There are excellent reasons to expect a formal system of symbols to
correctly predict future time in reality: the operation of machines,
chips, programs. Of enormous complexity, iterating for trillions of
steps in time, the outcomes are consistent and predictable.

As for someone "bemoaning how logic...future," temporal logic is an
active research area. Arthur Prior has written much about the logic of
time. Modal logic is essentially about this kind of reasoning.

Pace the point below about comets hitting planets, a formal symbol
system is not going to predict something dependent on events we cannot
see (yet) or model (yet). It would be unreasonable to expect a logic of
time to somehow predict events from outside our "knowledge cone" (like
a light cone, but for knowledge).

>
> As far as I know, there is no good formulation of
> a formal connection between a formal system and """"""reality"""""
> <-unbalanced quotes, the secret
> cause of asymmetry in the universe. How's that for a
> "quining" paragraph?

We analyze Reality in bits and pieces, in facets. We analyze planetary
motions, and now we have logical symbol models which are enormously
accurate and far-reaching in time. Granted, models of future planetary
positions cannot predict events outside the model, such as collisions
with comets not yet charted, and so on. But this is not a plausible
goal of any model.

I don't understand your "secret cause of asymmetry in the universe"
point. We understand some things about symmetry breaking in particle
physics theories, via gauge theories and the like. If you want more
than this, you'll have to expand on what you mean here.



>
> Is there? For example, "truth" is defined in formal logic with respect
> to, again, formal models with an infinite
> number of formal symbols in them. It is not defined with respect
> to some vague "correspondence" with external reality.

Actually, science is just about such correspondences with external
reality.

I haven't argued that logic alone is a substitute for science,
measurement, experimentation, refutation, correction, adjustment,
model-building.
>
> Someone was writing about "correspondence theory"
> with this goal in mind many years back, and that sounded
> interesting. I haven't read Tegemark et al. What do they say
> about the formalities of how mathematics extends to correspond to, or
> to be? external reality? To me, there is
> still a huge disconnect there.

Again, I don't understand what you mean by "there is still a huge
disconnect there."

If you are refuting Tegmark, you should read his articles first.

If you are saying that much still needs to be done, this is of course
true, fortunately.

--Tim May
Received on Sat Jan 11 2003 - 12:53:48 PST