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Re: [ontolog-forum] Ontological Assumptions of FOL

To: "Chris Partridge" <mail@xxxxxxxxxxxxxxxxxx>
Cc: "'[ontolog-forum] '" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Tue, 20 Mar 2007 11:30:54 -0500
Message-id: <p0623090ec225b8fcf500@[]>
>>  >Pat Hayes schrieb:
>>  >>
>>  >>  Well, I can see a lot of problems with this. If
>>  >>  you believe, for example, that all spatiotemporal
>>  >>  entities are in some sense physical, you will get
>>  >>  into trouble.
>>  >
>>  >Let me from my philosophical corner just add one long sentence: No
>>  >famous philosophical ontologist who posits physical (material) things in
>>  >space and time has argued that everything that exists in space and time
>>  >is physical (material); for instance, many claim that property instances
>>  >*inhere in* physical things, but this does not mean that these
>>  >spatiotemporal instances *are* physical entities.
>>  Possibly. Nevertheless, frankly, the opinion of
>>  famous philosophical ontologists on matters like
>>  this is of less interest than what actual written
>>  and deployed formal ontologies say about it. One
>>  can reasonably claim, and indeed ontologies have
>>  claimed, that anything spatiotemporal has a
>>  spatiotemporal extent, and any spatiotemporal
>>  extent contains a kind of physical stuff, so...
>Are you sure this is phrased right. What about vacuums? Surely they do not
>contain stuff - where stuff is material in the normal everyday sense. Or am
>I missing something?    (01)

I guess that would require one to consider 
"vacuum" a kind of stuff. I'd be happy to do 
that. Until a few years ago, there was a company 
on the south bank of the Thames which sold vacuum 
to hospitals. They had their own vacuum supply 
pipes under the Thames. There are huge spherical 
tanks at NASA-Ames whose function is to hold 
vacuum. Dewar flasks are full of vacuum. Vacuum 
could be defined as the stuff with zero density, 
for example.    (02)

BTW, the general idea of which this is the 
limiting case, that negative pressure is real, is 
built into the English word "suck". Try talking 
about sucking a milk shake through a straw in 
correct physical terms, using positive 
atmospheric pressure, and see how complicated it 
gets. The very idea that the atmosphere exerts 
pressure was only figured out 2.5 centuries ago, 
and seemed incredible at the time.    (03)

>If this is what the ontologies claim - aren't they just wrong (or,
>misguided, or ...)    (04)

Who is to say what is right or wrong here? There 
is no fact of the matter. If it is consistent and 
useful to regard vacuum as a kind of stuff, then 
by all means an ontology may do so. I suspect 
that is easier to describe it that way, than 
having to write special vacuum-exceptions into 
otherwise quite compact and useful axioms. 
(Particularly as such exceptions lead to serious 
reasoning problems, eg having to 'prove' that 
things are non-vacuum whenever any reasoning 
about materials gets done.)    (05)

There are many other examples of where an 
ontological decision is a toss-up between two 
ways of describing the same reality. Consider the 
time-line. Is there a future point at infinity? 
Its often useful to say there is, since that 
means that all intervals can be described as a 
pair of endpoints. Mathematicians typically have 
no problem with this idea, but philosophically 
trained ontologists tend to get their knickers in 
a twist wondering what 'kind' of temporal thing 
that point can be. I side with the mathematicians 
in this case. (BTW, backward oriented 'negative' 
intervals are also extremely useful things to 
have in a temporal ontology, but very few extant 
temporal ontologies allow them.)    (06)

>I thought formal ontologists tended to equate concrete and spatio-temporal
>rather than stuff and spatio-temporal. And that there tended to be little
>more here that that concrete things were spatio-temporal.    (07)

I have trouble understanding what is concrete about a pure vacuum, myself. :-)    (08)

Pat    (09)

>  >
>>  BTW, what exactly does 'inhere' mean? Apparently
>>  X may inhere in Y and Y have a quality that X
>>  lacks (physicality), so why does it follow that
>>  if X inheres in Y and Y is spatiotemporal, that X
>>  is spatiotemporal? (Probably we should take this
>  > offline, if you feel like replying :-)
>>  Pat
>>  >/Ingvar J
>>  >
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