http://www.mhpbooks.com/third-edition-of-the-oed-to-be-completed-in-2034/
It appears that John is describing the mathematical set-theoretic sense of "general" here.
It seems from John's definition that the most "general" theory would be something like:
"something exists"
I think that practical knowledge engineers consider "general" to mean "generally useful" in which case an ontology with more primitives would be one that is more generally useful, i.e. "general". It covers more cases, and, with proper editing, can be made as small and efficient as is required for any specific application.
On Jan 20, 2016 11:57 AM, "Christopher Menzel" <chris....@gmail.com> wrote:
>
> On 17 Jan 2016, at 1:47 PM, Patrick Cassidy <p...@micra.com> wrote:
>>
>> It appears that John is describing the mathematical set-theoretic sense of "general" here.
>> It seems from John's definition that the most "general" theory would be something like:
>>
>> "something exists"
>
>
> That's exactly right. "Something exists" — usually formalized as ∃x∀y y=x
Doesn't that mean "exactly one thing exists"? Not quite the same as "something exists", I think.
Gregg
On Jan 20, 2016 11:57 AM, "Christopher Menzel" <chris....@gmail.com> wrote:> On 17 Jan 2016, at 1:47 PM, Patrick Cassidy <p...@micra.com> wrote:
>>
>> It appears that John is describing the mathematical set-theoretic sense of "general" here.
>> It seems from John's definition that the most "general" theory would be something like:
>>
>> "something exists"
>
>
> That's exactly right. "Something exists" — usually formalized as ∃x∀y y=xDoesn't that mean "exactly one thing exists"?
Hmm. I'm not sure that really buys us anything. Your last formula won't do since it leaves x unbound. The first two formulae are problematic for various reasons, but the main thing is that FOL quantificational propositions are only intelligible on the presupposition that there is a domain or universe of quantification - emphasis on "there is". So the logical formalism itself depends on extra-logical, ontological presuppositions. In other words, it doesn't matter what P is in \Exists x.P - you can't treat it as a meaningful proposition without making an implicit antecedent commitment to the existence of at least one universe of quantification. Even if it's false, something must exist, otherwise it could not be false (or true).
But even that does not capture "something exists", as far as I can see. Maybe the universe of quantification is the only thing that exists. I can't see how to get to "something exists" without introducing modalities - e.g. one thing exists, but possibly others things exist too. And even if it were expressible in FOL, it would not count as a logical truth, since it's expression would depend on extra-logical concepts.
Not trolling, btw, I just find the subtleties of logic loads of fun, and virtually endless.
Gregg
On Jan 22, 2016 3:41 PM, "Christopher Menzel" <chris....@gmail.com> wrote:
>
> On 20 Jan 2016, at 4:22 PM, Gregg Reynolds <d...@mobileink.com> wrote:
>>
>> On Jan 20, 2016 11:57 AM, "Christopher Menzel" <chris....@gmail.com> wrote:
>>
>> > On 17 Jan 2016, at 1:47 PM, Patrick Cassidy <p...@micra.com> wrote:
>> >>
>> >> It appears that John is describing the mathematical set-theoretic sense of "general" here.
>> >> It seems from John's definition that the most "general" theory would be something like:
>> >>
>> >> "something exists"
>> >
>> >
>> > That's exactly right. "Something exists" — usually formalized as ∃x∀y y=x
>>
>> Doesn't that mean "exactly one thing exists"?
>
> DOH! Of course it does. :-/ What I meant to write was "∃x∃y y=x". This is of course equivalent to simply "∃x x=x" but I prefer it to the latter because one usually expresses "x exists" as "∃y y=x" — i.e., x is identical to something — and so something exists is then naturally expressed as the existential generalization of that.
>
Hmm. I'm not sure that really buys us anything.
Your last formula won't do since it leaves x unbound.
The first two formulae are problematic for various reasons,
but the main thing is that FOL quantificational propositions are only intelligible on the presupposition that there is a domain or universe of quantification - emphasis on "there is".
So the logical formalism itself depends on extra-logical, ontological presuppositions.
In other words, it doesn't matter what P is in \Exists x.P - you can't treat it as a meaningful proposition without making an implicit antecedent commitment to the existence of at least one universe of quantification.
But even that does not capture "something exists", as far as I can see. Maybe the universe of quantification is the only thing that exists.
I can't see how to get to "something exists" without introducing modalities - e.g. one thing exists, but possibly others things exist too.
And even if it were expressible in FOL, it would not count as a logical truth, since it's expression would depend on extra-logical concepts.
Not trolling, btw, I just find the subtleties of logic loads of fun, ...