On Jan 29, 2009, at 1:00 PM, John F. Sowa wrote:  (01)
> Len and Pat,
>
> As before, I agree with Pat on this point, but I'd like to
> add a few more comments.
>
> LY>> In ordinary life their are plenty of examples of 'establishing
>> identity' from simple "hello" to solving and prosecuting crime.
>> But formal meaning of identity in CT is (in my non-mathematical mind)
>> any procedure that performs identity morphism according to definition
>> of Category (cited below).
>
> PH> We seem to be talking about two different things at the same time.
>> There is the ordinary every-day pre-formal notion of establishing
>> identity, which we do when someone calls us on the phone and we say
>> "who is this?" This means something like "figuring out who or what
>> some unknown thing or person is", where to know "what something is"
>> has never, AFAIK, been fully analyzed by linguistics and never
>> formalized, but seems to mean something like having enough
>> information about a thing to be able to mentally distinguish it
>> from other similar things, or maybe having a description of the
>> thing which is adequate for the purposes of holding a conversation,
>> or some such.
>
> There have been many volumes written about the difficulty of verifying
> identity. They cover many different fields -- philosophy of science,
> epistemology, forensics, military intelligence, security, politics,
> privacy, etc. In all these fields, the issues are extremely dependent
> on the domain, the purpose, and the degree of certainty required.
>
> In logic, these issues are masked by a simple statement, such as 
> 'x=y'.
> But that statement could be the conclusion of an arbitrarily complex
> if-then rule:
>
> If x satisfies the conditions...
> and y satisfies the conditions...
> and x and y co-occur under the conditions...
> and further evidence...
> then x=y.
>
> Many philosophers talk about "identity conditions", but trying to
> determine whether those conditions hold in any particular case can
> be extremely difficult.
>
>
> So the short answer is that it's easy to say x=y in logic, but the
> practical matter of determining whether a particular observation
> of x is sufficient to identify it as y may be challenging.  (02) 
All this is true, but I suggest irrelevant. The same can be said about 
any assertion in any ontology: in practice, it might be very hard to 
tell if it holds in any particular circumstances. But that isn't the 
central issue for ontology writing. The importance of identity 
conditions is that they state what the conditions are that need to be 
checked. Until that is done, no amount of police procedurals are going 
to work.  (03)
>
> For these reasons, I have a skeptical attitude toward talk
> about "identity conditions" as if they were a magical solution
> to some very serious issues of ontology.  (04) 
They aren't magical, but they are necessary. Several classical 
ontological disagreements can be seen as differences of opinion about 
identity conditions. For example, if you take the engine from an old 
car and use it as a planter (a real example), is it still an engine? 
Ontoclean takes questions like this very seriously, as it should.  (05)
However, the sense of "identity" being used here has nothing to do 
with category theory's sense in "identity morphism".  (06)
Pat  (07)
>
> John
>
>
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>  (08) 
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