Re: Contexts and quantifiers in KIF (Chris Menzel)
From: (Chris Menzel)
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Subject: Re: Contexts and quantifiers in KIF
To: (sowa)
Date: Wed, 14 Apr 1993 23:17:52 -0500 (CDT)
Cc:,, interlingua@ISI.EDU, srkb@ISI.EDU
In-reply-to: <> from "sowa" at Apr 14, 93 12:11:44 pm
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You wrote in your response to Jim:

: My basic point is that there is only one world, and that is the real live
: concrete one we live in.  A possibility exists only as a model:  either a
: mental model in some person's brain, a data structure in a computer system,
: an abstract set-theoretic construction in a mathematical formalism, or a
: physical analog that simulates the behavior of some other system.  

Despite your decisive and authoritative tone, you are of course just
expressing one among many competing philosophical views on the
metaphysics of modality here.  There are in particular entirely
rigorous and philosophically respectable accounts of worlds according
to which there are many possible worlds in addition to the actual
world, and which are just as real.  For example, Prior (and Kit Fine,
following him) defined a world to be a "maximally possible"
proposition, i.e., a proposition W such that for any proposition p,
either W entails p or W entails not-p, but not both.  On this view,
then, ALL possible worlds, the actual one included, are abstract
entities, viz., propositions.  (Which is not, of course, to say that
the physical universe is an abstract entity; to call THAT the actual
world, in the context of this view, would be an equivocation.)  This
view of course assumes a metaphysics of abstract propositions that you
would no doubt reject; nevertheless the view is entirely consistent
and, for simple-minded platonists like me, quite appealing.

: The use
: of the word "world" for any of these structures is a metaphor, ...

Which, again, is not to say that there aren't any rigorous,
NONmetaphorical notions of possible worlds.

: ...and like all
: metaphors it can help to clarify some points, but it can also cause serious
: confusion if taken literally.  David Lewis, for example, is a smart man, but
: I believe that he has spread around an enormous amount of confusion by not
: distinguishing the literal and metaphorical uses of the word "world".

Lewis is entirely clear on the distinction; when he says "world"
(unlike Prior and his ilk), he means--in as literal a sense as you
please--a mereological sum of physical objects just like our physical
universe (though perhaps with far more or far fewer objects, and very
different laws and properties), but spatially and temporally unrelated
to our universe.  In the usual fashion, then, he takes necessity to be
truth in all such worlds, possibility truth in some.

: I have found that one of the easiest ways to clarify a philosophical problem
: is to restate it in different terms that avoid some of the loaded connotations
: of a misleading metaphor.

My point in a nutshell: to label all world talk as metaphorical begs
some big questions.

: If you do a global change of the word "world" 
: to almost any other term -- "model", "data structure", "set theoretic
: construction", or "whatchamacallit" -- all of the formal properties of the
: theories by Kripke, Montague, and others are preserved...

This simply cannot be done if the notion of a world has been given
some sort of analysis as in Prior's account.  If I've *identified*
worlds with propositions or some other sort of abstract entity, or
even with Lewisian worlds, then by definition they are not models,
data structures, etc. (unless of course those happen to be the things
I've identified as worlds).  What you say is perhaps true for
unanalyzed world talk, but not in general for a given world *theory*.

: I definitely agree that talk about possibility is more than a mere 
: discussion about words.  But instead of saying that modal language is about 
: alternative worlds, I say that it is about alternative models of the world.

If by an alternative model of the world you mean a model that *could
have been* a model of the way things are, then (subject to a lot of
qualifications) this is roughly my own view.  Note however that
modality (though not world talk) remains an unanalyzed primitive for
you.  I think that is a Good Thing.

: > 3.  There is a significant sense in which the following sentence is true:
: > 'Bush could have been re-elected, although he was not.'  Here the 'could' 
: > reflects not a logical possibility but a "causal" or "historical" one.  
: > Much of our ability to learn from the past involves our understanding of 
: > What would have happened instead if ....  Perhaps the most interesting use 
: > of modal data structures is to describe precisely the causal 
: > consequences of 
: > of roads not taken (what are all the differences that makes?).
: >The possible 
: > worlds here are REAL to the extent that the modal statements
: > (i.e., it COULD have been ...) are TRUE.
: I agree with everything in that paragraph execept the sentence "The possible
: worlds here are REAL...."  That word "REAL", even when capitalized, has no
: meaning other than a general term of approbation.  

I took Jim not so much to be confessing his belief in possible worlds
as to be insisting that modal statements have a genuine, objective
truth value.  The issue starts getting fuzzy when we ask in virtue of
WHAT are such statements determinately true or false.  World talk
comes in real handy as a sort of pseudo-explanation (my biases are
showing).  But it is natural; why do we intuitively allow that certain
propositions are possible and others--your being a prime number,
say--not?  Mustn't there be SOMETHING in virtue of which some
propositions are genuinely possible and others not?  Worlds provide a
seductive answer: a proposition is possible BECAUSE there's some world
in which it is true.  My own view is that there may not ultimately be
anything more to say about why a certain statement is possible other
than that it is just so.  But that takes us down another path.


Christopher Menzel		    Internet ->
Philosophy, Texas A&M University    Phone ---->   (409) 845-8764
College Station, TX  77843-4237	    Fax ------>   (409) 845-0458