On Fri, May 24, 2013 12:25, William Frank wrote: (01)
> More to the point, for me, what are the practical implications of limiting
> existential quantifiers to a particular category of the things we talk
> about? (02)
The implication is the type of logic that may be used. Depending upon
the limitations, you are restricted to first order logic, some form of
Description Logic, or something else. (03)
> In other words, how does it *help* to not let people say, 'there exists a
> rule, there exists a color, there exists a category of binary relations,
> called symetric relations? (Or, am I mistaken, and this is all OK --
> but if it IS OK, then what is not OK?). (04)
This is all OK in higher-order logic. BTW, your third example either
names the relation, thus collapsing the "there exists" or it provides
an additional label for the class. (05)
(thereExists ?PredicateClass
(and
(isa ?PredicateClass Class)
(genls ?PredicateClass BinaryPredicate)
(prettyString ?PredicateClass "symetric relations")
(thereExists ?PREDICATE
(and
(isa ?PREDICATE ?PredicateClass)
(isa ?PREDICATE KinshipRelation)
(?PREDICATE DonFoxvog DougFoxvog)
(?PREDICATE DougFoxvog DonFoxvog)))))) (06)
> I believe that some people seem to think that if a computer
> cannot decide if a statement is true or false, then it should
> be disallowed, so they do not like anything but restricted kinds
> of first order logic, (07)
Computers can decide whether many higher-order logic statements
are true, given appropriate reasoners. In an open-world system
lots of statements are unprovable, but not necessarily false -- the
data is merely not in the system. (08)
> so I think I understand the nature of their view,
> as a practical matter, (even though I think that
> this view is pernicious). But you seem to have a theory about
> ontological languages that I just can't see what it will do. (09)
> ( I am not sure whether you choose to identify
> 'individuals' based on a relationship
> between those things and phenominological experience
> or between them and physics
> (which do seem to me to be miles apart, even though both are hard
> to grasp), but however you pick out the individuals from the
> non-individuals, how does it make people's understanding
> and description of
> the world easier and different from what it would be otherwise? (010)
People normally take "individual" merely to mean a "non-class" thing
that can be referred to. If one can refer to predicates, then predicate
is a subclass of individual. If one can not refer to metaclasses, then
every class instance is an individual. If one can refer to metaclasses,
then there are instances of classes that are themselves classes, and
thus not individuals. (011)
People brought up in DL often use the term "instance" to mean the
class of things that their logic allows to be instances of a class, i.e.,
non-predicate individuals. As such they equate the terms and may use
the term "individual" when they mean an instance of something. (012)
As far as i am concerned, identifying something as an "individual",
is merely stating that it is not a class. (013)
-- doug foxvog (014)
> On Fri, May 24, 2013 at 11:17 AM, Matthew West
> <dr.matthew.west@xxxxxxxxx>wrote:
>
>> Dear John,
>> Yes of course they are.
>> > MW
>> > > This [traffic laws] is about social construction. The rules are
>> still
>> > > classes of activity, but there is a social agreement about what they
>> > > apply to.
>> >
>> > I agree. But I also believe that habits and social agreements are
>> real
>> (i.e.,
>> > I'm happy to use existential quantifiers to refer to them).
>>
>> Regards
>>
>> Matthew West
>> Information Junction
>> Tel: +44 1489 880185
>> Mobile: +44 750 3385279
>> Skype: dr.matthew.west
>> matthew.west@xxxxxxxxxxxxxxxxxxxxxxxxx
>> http://www.informationjunction.co.uk/
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>>
>>
>>
>>
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>
>
> --
> William Frank
>
> 413/376-8167
>
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