Pat Hayes wrote:
>> Pat Hayes wrote:
>>>> Pat Hayes wrote:
>>>>
>>>>>>> (forall (c)(ist c (that (rains))))
>>>>>>> In IKL, a relation with no arguments is itself a proposition, so
>>>>>>> one could write it without the "that":
>>>>>>>
>>>>>>> (forall (c)(ist c rains))
>>>>>>
>>>>>> Just a syntactic feature?
>>>>>
>>>>> Yes, essentially. It is way that the use/mention distinction
>>>>> applied to propositions comes out in the IKL syntax.
>>>>
>>>> So if
>>>> (that (rains))
>>>>
>>>> is equivalent to
>>>> rains
>>>>
>>>> , is
>>>> (that (dead osama))
>>>>
>>>> equivalent to
>>>>
>>>> "dead osama"
>>>> ?
>>>
>>> I guess it might be if that last expression were legal IKL syntax,
>>> but it isn't. You can only get away with this trick when the relation
>>> has no arguments. (01)
So it is quite the opposite: it *is* legal, but not equivalent to the
other expression. (02)
>>
>> Why would this not be syntactically legal? You do use quotes to
>> delimit names that include spaces, right? "osama bin laden" is legal
>> syntax, and "dead osama" is not??
>
> Sorry, you are quite correct. I was reading your quotes as part of the
> email, not part of the IKL. But then these are not equivalent: in fact
> they are not logically related at all, any more than Patrick is related
> to trick. As you say:
>
>> The problem I see is that IKL could not consider (that (dead osama))
>> equivalent to the (syntactically legal!) "dead osama" because the
>> latter is understood as an atomic name, so it would not be parsed into
>> "dead" and "osama".
>
> Yes, exactly.
>
>> But you can well say
>>
>> (= "dead osama" (that (dead osama)))
>>
>> , can't you?
>
> You can say it as an axiom, but it's not a logical tautology. This is:
>
> (= "dead osama" (that ("dead osama")))
>
> but of course (dead osama) and ("dead osama") have no logical
> relationship to one another. (03)
Of course. (04)
vQ (05)
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