Dear John, (01)
> Whether you have a 3D or a 4D perspective, change still exists, (02)
[MW] Not really. 4-Dimensionalism has the effect of making 3D change
seem static, because it is looked at in a different way, in 4 dimensions
instead of 3. (03)
> and the distinction between extension and intension is still
> significant. (04)
[MW] Well that is true, but extensionalism in classes is quite natural
when you have dealt with change in the way that 4-dimensionalism does.
> JFS>> But even for a fixed design, the set changes with every instance
> >> that rolls off the assembly line.
> [MW] Only if you take a 3D perspective which sees what exists as
> What exists NOW.
> In any perspective, you must be able to plan for the future, talk
> about what exists NOW, or what exists in some hypothetical time
> or place that might never exist anywhere in the 4D universe. (05)
[MW] Yes. But in a 4-dimensional world view, all of this can be dealt
with extensionally, so why wouldn't you? If you are talking about the
set of cars of a particular model type, then you are talking about all
of them that ever existed or ever will exist. There are lots of other
sets that are the sets that consist of all the cars that exist for
some period of time (until a new one exists, or an old one ceases to
exist). These are all subsets of the 1st set. None of these is intentional
and changing over time. But when you have 4D objects that themselves do
not change (because time has already been taken into account in their
extension) this is a perfectly natural way to deal with classes.
> You must also be able to talk about hypotheticals that could have
> existed in the past when you're carrying out a forensic investigation
> about how some situation at some point in time and place happened
> to evolve out of some other situation at some other time and place. (06)
[MW] Well you can do the usual things with possible worlds to deal with
That, so no great problem there.
> JFS>> You can't use extensional terms such as 'set' and 'class', which
> >> change with every instance that rolls off the assembly line.
> >> It's essential to use intensional terms, such as 'category' or
> >> 'type'. Since 'type' takes one syllable instead of four, that
> >> is a good choice.
> [MW] But you can if you are a 4-dimensionalist.
> A 4D world view does not preclude change. The fundamental laws of
> physics are stated as partial differential equations that vary
> in the spatial coordinates and the time coordinate. (07)
[MW] They are just descriptions of 4D objects, just as a quadratic can
describe a line in two dimensions.
> So you can and must be able to think, talk, and plan for change
> in our actual universe. (08)
[MW] You just do what you talk about as planning for change in a different
You must also be able to talk about the
> hypothetical aspects of the universe that might or might not exist
> in any region of the actual universe. (010)
[MW] Yes. That's not a problem though, as I said above.
> Bottom line: The distinction between extensions and intensions is
> independent of any coordinate system or point of view. It is
> fundamental to any theory, language, or logic for ontology. (011)
[MW] The distinction is independent, but that does not mean you have to
use intensional objects rather than extensional ones. However, a 3D ontology
will be predisposed to an intensional approach, whereas I find with a 4D
ontology an extensional approach is more natural. (012)
> Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
> Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-
> Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
> Shared Files: http://ontolog.cim3.net/file/
> Community Wiki: http://ontolog.cim3.net/wiki/
> To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx
Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
Shared Files: http://ontolog.cim3.net/file/
Community Wiki: http://ontolog.cim3.net/wiki/
To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx (016)