Dear John, (01)
> I agree that some concept or mechanism such as possible worlds
> is necessary to apply a set-based approach to hypothetical
> reasoning or any reasoning about plans for the future.
>
> But as I said, using the term 'extensional' when talking about
> possible worlds is highly misleading. In fact, Montague called
> his version of logic that talked about sets of possible worlds
> and sets of things in them IL -- Intensional Logic. (02)
MW: And Lewis called them Modal Realism, and was definitely thinking
extensionally.
>
> MW> The good news for me is that having taken on board possible
> > worlds, I get a very good return for my ontological commitment.
>
> I agree that the method can work. But I just want to clarify
> the point that what makes it work are the *intensional* aspects. (03)
MW: I don't and never have had a problem with intensional definitions
that pick out particular sets. I have only ever said that the sets the
pick out have extensional identity, and that this is independent of how
you have defined them.
>
> MW> ... if I want to talk about 2 eyed sheep and 4 legged sheep
> > and determine if they are necessarily the same, then I need
> > only use sets that that go across all possible worlds.
>
> But those sets are purely imaginary. (04)
MW: Lewis would disagree with you. He claims that they are real and not
imaginary, hence modal realism. This is really a feature of 4
dimensionalism though. In 3D only the present exists, and neither the
future or past do, whereas with 4D both the past and the future exist as
well as the present. I am therefore not surprised that he chooses to
claim the possible worlds exist too. On the other hand I am indifferent,
since it seems to me to make no difference. (05)
What does make a difference is that the membership of these sets is
unknowable - we do not have access to other possible worlds. (06)
> Your operations are
> logical manipulations based on the axioms and descriptions
> of those possible worlds. You are doing the same kind of
> reasoning that Montague and others call 'intensional'. (07)
MW: Yes of course. When did I ever say otherwise?
>
> MW> I can see that these sets are...
>
> The word 'see' in that sentence is metaphor. (08)
MW: Of course. I thought you liked metaphor and analogy. (09)
> Nobody can
> actually observe an imaginary world or anything in it. (010)
MW: That is not enough to make it imaginary. I can't see the past
either. (011)
Regards (012)
Matthew West
Information Junction
Tel: +44 560 302 3685
Mobile: +44 750 3385279
matthew.west@xxxxxxxxxxxxxxxxxxxxxxxxx
http://www.informationjunction.co.uk/
http://www.matthew-west.org.uk/ (013)
This email originates from Information Junction Ltd. Registered in
England and Wales No. 6632177.
Registered office: 2 Brookside, Meadow Way, Letchworth Garden City,
Hertfordshire, SG6 3JE. (014)
_________________________________________________________________
Message Archives: http://ontolog.cim3.net/forum/uom-ontology-std/
Subscribe: mailto:uom-ontology-std-join@xxxxxxxxxxxxxxxx
Config/Unsubscribe: http://ontolog.cim3.net/mailman/listinfo/uom-ontology-std/
Shared Files: http://ontolog.cim3.net/file/work/UoM/
Wiki: http://ontolog.cim3.net/cgi-bin/wiki.pl?UoM_Ontology_Standard (015)
|