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Re: [ontolog-forum] Ontology and methodology

To: "John F. Sowa" <sowa@xxxxxxxxxxx>
Cc: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Mon, 19 Mar 2007 10:37:45 -0500
Message-id: <p06230907c2245cbbb68a@[]>
>Dear Chris, Matthew, John, Adrian, and Florian,
>I thought that all those issues had been settled decades ago    (01)

They have been being discussed that long, but they never get settled.    (02)

>CP> Would there be a single object (John), who is an instance
>  > of both employee and person, in your scheme of things?
>  > I think you need this to get your sub-type relation.
>Of course.
>CP> This enables me to allocate responsibility to the employee
>  > but not to the person.
>We don't have two individuals here.  There is only one.
>If I'm assigned a task as an employee, it's my task, not
>the task of some virtual employee.
>MW> This is also what we now do with a 4-dimensionalist
>  > approach.  However, it is this approach that also demonstrates,
>  > as I explained to Duane that employee is not a subtype of
>  > person, taking person as the person-for-the-whole-of-their-life.
>Subtype has a very clear and simple definition:  X < Y
>means that every instance of X is an instance of Y.    (03)

I would prefer to say that it implies this, but subtype is actually 
somewhat stronger. Not every occassion of one category being included 
in another need be viewed as a subtyping. BTW, this 'intensional' 
perspective gives more efficient reasoning, as well as being more 
natural.    (04)

>This is true in a 3-D version and in a 4-D version.  When a
>person stops being an employee, there is no employee.  But
>as long as a person is an employee, that employee is one
>and the same individual as that person.    (05)

That doesn't make sense in a 4-d framework, or else its false. You 
are using the 3-d (continuant, temporal) notion of 'same' here (shown 
by the weasel phrase "as long as"). In the 4-d way of talking, 
identity is timeless and holds between temporally extended entities. 
A temporal part of an instance is not usually an instance.    (06)

>MW> Let us look at a couple of possibilities here:
>This definition covers every case.  It is true in a 3-D
>version and in a 4-D version.  It implies that the entire
>spatiotemporal extent of Employee is included in the
>spatiotemporal extent of Person.    (07)

Not unless you conflate class membership with temporal parthood. I 
think Matthew is keeping these ideas separate.    (08)

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