Re: modal logic
At 11:29 AM -0500 30/6/2000, Chris Menzel wrote:
>Sorry for the length, but most of the following is just meant to be
>informative for those who haven't yet dabbled much in modal logic and
>the surrounding philosophical issues.
Chris, I highly appreciated your clarification on modal logic and
ontology, as well as your essay on "actualism" on the Stanford
Encyclopedia of Philosophy. I believe that some notion of modality is
unavoidable for formal ontology, and I agree what you seem to
suggest, that the minimal modal logic S5 is adequate for most cases.
I would like to underline that in many cases a modal semantics is
necessary to understand an ontological axiom, but the axiom itself
does not need to be expressed in modal language. For instance, you
pointed to the generalization "Any kissing is a touching", which
needs to be understood as a necessary statement even if it is
formulated as a non-modal statement. Another example may be the
statement "Being an apple is a rigid property", which is non-modal
although the definition of rigidity is based on a modal formula.
I relied on modality and intensionality when trying to clarify the
notion of "conceptualization" that appears in Tom Gruber's definition
"An ontology is a specification of a conceptualization" (see
http://www.ladseb.pd.cnr.it/infor/Ontology/Papers/FOIS98.pdf): a
conceptualization can't be a "static" view of the world, but it
rather accounts for the way we deal with *changes* in the world, i.e.
with multiple worlds. Grasping the *meaning* of a certain term (i.e.,
its "intension") implies being able to competently use that term in
different worlds. That's why ontologies cannot avoid some notion of
possible worlds.
>There may not be anything like consensus, but as an alternative, once
>again, couldn't we define various modal extensions of the SUO which
>could be incorporated as needed? More generally, must the SUO be so
>fixed?
I agree very much. I don't believe it is necessary to agree on a
single modal logic for SUO purposes. The simplest the better, but
there is nothing strange if in some cases (deontic concepts, for
instance) we adopt a different logic...
>S5 is the most popular, but some philosophers (notably Nathan Salmon)
>have argued that it is too strong, especially with regard to the modal
>properties of artifacts.
Have you got a pointer?
-- Nicola
---------------------------------
Nicola Guarino
National Research Council phone: +39 O49 8295751
LADSEB-CNR fax: +39 O49 8295763
Corso Stati Uniti, 4 email: Nicola.Guarino@ladseb.pd.cnr.it
I-35127 Padova
Italy
http://www.ladseb.pd.cnr.it/infor/ontology/ontology.html
(***updated 2/6/2000***)