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Re: [ontolog-forum] The Relation Between Logic and Ontology in Metaphysi

To: "John F. Sowa" <sowa@xxxxxxxxxxx>, Ingvar Johansson <ingvar.johansson@xxxxxxxxxxxxxxxxxxxxxx>
Cc: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Fri, 16 Mar 2007 11:01:10 -0500
Message-id: <p06230907c2206bf3ea1e@[]>
>Fine.  We can all agree on that:
>  > I certainly agree that ontological considerations might
>  > play a role in the choice of an appropriate formalism.
>And the converse is also true:  the formalism can affect
>or bias the choice of ontological categories and the
>way they are developed, studied, and used.    (01)

Well, its hard to argue against a "can", but I 
think this point is easily overblown. I would 
say, in response, that a judicious and reasonably 
sophisticated use of FOL is capable of expressing 
any ontological view that can be described in 
English; that there is no *inherent* ontological 
bias in FOL. From which it follows that we should 
not conclude, from observations such as this, 
that we need to be actively searching for better 
formalisms, or feel obliged to use a variety of 
'more suitable' formalisms for various 
ontological perspectives.    (02)

So for example, Ingvar Johansson wrote:
" I happen to think that the dominance of first-order
predicate logic in the brains of many analytic metaphysiciains mislead
them into false ontologies. They take away the difference between
natural kinds and properties (since it is not visible in 'Fa'), and they
do not allow different modes of existence (since these cannot be seen by
means of the existential quantifier)."    (03)

Well, maybe: but even if this phenomenon (a) does 
indeed sometimes happen, and (b) really is an 
error - which of course is open to endless 
debate, as it has been for the last two millennia 
-  it is not *impossible* to make these 
distinctions in FOL. Natural kinds can be viewed 
as a special type of logical property, for 
(F a) & (IsNaturalKind F)
or, one could adopt a description-logical style 
of expression and distinguish between mere 
logical predication (F a) and natural-kind as a 
special relation of class membership (Kind a F), 
perhaps with an axiom which relates natural kinds 
to their weaker (merely extensional) associated 
predications:    (04)

(forall (x y)(if (Kind x y)((propertyOf x) y) )    (05)

(all axioms written in the CLIF dialect of ISO Common Logic).    (06)

As for "modes of existence", I confess to being 
one of those with a misled brain, not 
understanding what is meant by this phrase; but I 
am sure that if it were to be explained more 
thoroughly, I could find a way to render it into 
FOL reasonably briskly.    (07)

Pat    (08)

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