Dear Pat and Chris, (01)
> > I suspect that you two may know more than me in many areas - and
> it
> > is quite
> > a while - maybe 10 years - since I researched this in any depth.
> >
> >>> MW: Yes, I had worked that out too. I also like extend this to
> >>> think of
> >>> branching worlds. So, for example, that all the possible worlds
> from
> >>> here have up to here as a part, and have different parts
> hereafter.
> > Etc.
> >
> > What is interesting is how the branching links mereology and
> > identity - and
> > enables transworld objects.
> > I think that one will need to deal with situations here where a
> > temporal
> > stage of person can be simpliciter part of several different
> people
> > (their
> > different futures) - but only a temporal stage of one person in
> one
> > possible
> > world/history.
>
> Right. There are some cases that have been discussed in (at least)
> moral philosophy, involving identical twins, which at a very early
> stage of fetal development, in some cases, were one blastula. If
> life
> begins at conception, this is a difficulty. (See why I decided to
> leave philosophy? :-) (02)
MW: What I like about 4D is that it allows this to be explained without
giving rules that forbid it as a matter of principle, but which also
does not make or force a choice about which twin, or either or neither
or both split from which. It just allows the situation to be described.
>
> > One could also have several histories of a person (or whatever)
> > where no
> > part overlapped (as the divergence occurred before they were
> born).
> > After a person ceased to exists, s/he would be part of ALL the
> > subsequent
> > diverging worlds.
> > But maybe (like 4D) it is a case of getting used to the
> consequences
> > of a
> > position.
>
> There is a possibility much explored in science fiction, involving
> a
> 'matter transporter' which in fact disassembles its input, beams
> all
> the needed information to the output device which then rebuilds an
> exact replica; but then one of them goes wrong and leaves the
> original
> intact, so 'the' person splits into two replicas. See 'Rogue Moon'
> by
> Algys Budris, for example. (03)
MW: Again, as with the twins, 4D allows this possibility to be described
without judgement. (04)
It is interesting that branching is something that can happen within a
world as well as in a transworld sense. The Ship of Theseus is the
classic example. It seems to me that transworld branching is
straightforward though once you have established the different branches
belong to different possible worlds, which will be the usual case. The
possible world is a selector of branches.
>
> >
> > I also think that branching may have some uses, but not be a full
> > replacement for the Lewis apparatus - as one might want a
> similarity
> > where
> > there is no (potential for) identity at any time in the past, so
> the
> > histories never meet.
>
> The maximal ideal construction allows for this case. (05)
MW: I don't understand what you mean here. Could you explain further
please?
>
> > Or, another example, how far back the divergence occurred may not
> be
> > a good
> > measure for how similar we want to say situations are.
>
> True, but in general, we should distinguish temporal
> alternativeness
> from the alternativeness that gives rise to other modal notions. (06)
MW: If I understand you both, then this is simple for me. Things either
have a shared temporal part across possible worlds or they don't. If
they do you can talk about trans-world identity, if they don't then you
can't. You might be talking about similarity or some other such
relation, but it is not identity, and should not be conflated into the
same problem space.
>
> >
> > For some references see
> > http://plato.stanford.edu/entries/identity-transworld/ - '4.3
> > Transworld
> > identity and conditions for identity over time'- (cf. Brody, B.,
> 1980,
> > Identity and Essence, Princeton, NJ: Princeton University Press.,
> > 114-15;
> > 121 or Mills, E., 1991, "Forbes's Branching Conception of
> Possible
> > Worlds",
> > Analysis, 51: 48-50.)
> >
> > PH> Indeed, but (what I especially like) is that it gives many
> other
> > ways
> >> to 'branch', eg outwards spatially from a locally described
> >> situation,
> >> or backwards in the time-direction, when figuring out how
> something
> >> that did happen could have happened.
> >
> > I believe that this is the way temporal logics often work (and
> some
> > interpretations of physics - though this way out of my field).
> When
> > I looked
> > briefly, temporal logics used the metaphor of histories and
> > branching, but I
> > did not find any full-blooded 4D interpretation. (Pat am I right?
> I
> > did not
> > look very closely.)
>
> Well, I've not been reading actively for a while, but the last time
> I
> looked, future-branching was the most common case. That gives you
> Priors S4 logic, if its done straightforwardly. Certainly most of
> the
> AI planning formalisms assume a fixed past (often starting with
> state-
> zero). The most sophisticated case Ive seen has two independent
> Kripke
> relations, one giving a linear tense and the other being a
> possibility
> between entire world-lines.
>
> > But, to answer Pat's question, maybe there is room for a full-
> > blooded 4D
> > interpretation of branching.
>
> I think there is also a connection to the Barwise/Perry notion of
> 'situation', which is singular in that it is 'partial' compared to
> a
> Kripke/Lewis possible world. Chunks of 4D seem to have this
> quality.
> But this is all very vague at present. (07)
MW: Sounds interesting. Happy to be a sounding board if you do any work
on this. (08)
Regards (09)
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/ (010)
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. (011)
_________________________________________________________________
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 (012)
|