Re: SUO: Logic and Ontology
On 3/5/02 17:20, "Leo Obrst" <lobrst@mitre.org> wrote:
> Yes, I would agree that if you assume extensionality, as Bill suggests,
> you are nearly to the end of your chain, Matt. But many people have real
> problems with this assumpton.
>
> I too received this Axiomathes issue (and I too have a problem with the
> extensionality assumption), but have not yet read the Cocchiarella
> article (though I am usually sympathetic to his views). But I didn't
> think that was Lewis's view: geez, Bill, I thought nearly the opposite,
> will have to review. I just thought Lewis took a realist position wrt
> possible worlds.
That's true - about as real as you can get. But if you look at Counterpart
Theory, his quantifiers range over all the objects, not just the ones at a
world - it's a completely standard first-order theory so you don't have the
world-bound truth values of Kripke semantics.
What he does is have a special predicate for which things are at a given
world. So, all the beer for him is just all the beer - or the class of all
bits of beer. It's only that some worlds will have beer as parts of them
(for him if I understand correctly they literally are 4D parts) and some
won't. He deals with modal phenomena by introducing all of these possible
(excuse me - counterpart) beers, some of which correspond to the beer in the
actual world and some that don't.
.bill