[ontolog-forum] Existential Commitment in Logic: a Tabula Rasa

[Thomas Johnston <tmj44p@xxxxxxx>]

Pat, John, All:

I accidentally deleted the entire thread, including your responses to my comment of the 18th. So please re-post them. Nonetheless, this gives me a chance to jump out of the details, and try to see what the big picture looks like, at this point in the discussion.

1) Quine and most other logicians are find with associating ontological commitment with the existential quantifier. Arthur Fine (an outlier on this issue, I would think) prefers to associate ontological commitment with the universal quantifier. But those quantifiers, as quantifiers, are associated with "All" and "Some", and so calling the latter the "existential quantifier" begs the question I raised.

2) Sometimes, in natural language, we want to say "All ...." in a context in which we presuppose, and want and believe others to understand that we are presupposing (cf. Grice), the existence of what is referenced by the NP of the statement. At other times, we presuppose that the reference of the NP does not exist, and want and believe others to understand that we are presupposing that the reference of the NP does not exist. Same thing for "None ..." statements, same thing for "Some ..." statements, same thing for "Some ... not" statements. It was my belief that we want to be able to say all these things in natural language that led to my original question. 

3) I think Pat offered a distinction between "exists" and "really exists". This is a classic move to avoid accepting the conclusion of a specific syllogism; break the middle term in two. He makes a felicitous terminological suggestion: associate "ontological commitment" with "really exists", and commit to it by explicitly using "really exists" as a predicate. (I think this commits Pat to Anselm's Ontological Argument, but I'm not sure.) The other term he offers is "referential commitment", which he associates with the "exists" that logicians tie to the "Some" quantifier. And he explains referential commitment as ontological commitment relativized to a specified universe of discourse. That's a very nice move, and the explanation is persuasive. But it doesn't work for ordinary un-typed FOPL, since the universe of discourse for that logic (I think) is [Everything that Exists and Nothing that Doesn't]. However, perhaps when we talk about dragons, in natural language, Gricean conventions lead us to a presupposition of a universe which is not the "real" one", but is rather the real one supplemented with some fictitious entities (e.g. Tolkien's universe).

4) So I'm ok with this: NPs have referential commitment no matter what universe of discourse their statements are relativized to. But NPs have ontological commitment relativized only to universes of discourse which contain as referents things we believe really exist. This feels like an elaborate tautology to me, but it's what I make of Pat's distinction between referential and ontological commitment, and I don't know any non-tautologous way of stating it.

5) Referential commitment is made with referring expressions such as names. It is no more closely tied to the "Some" quantification than it is with the "All" quantification. This seems obvious to me but, I believe, does not seem obvious to either of you. But intuitions, expressed as "seems obvious" or otherwise, are not arguments. FOL, as John said, ain't broke. OK. But I'd add that FOL isn't a Swiss Army knife. It has limitations, illustrated by the extensive work done on various forms of intensional logics.

6) Prior to Pat's referential vs. ontological commitment distinction, I said that I thought ontological commitment could be made with specific uses of the "All" quantifier, and withheld from specific uses of the "Some" quantifier. Now I will use Pat's distinction and say: referential commitment can be made with any NP, regardless of whether "All" of "Some" is the quantifier used with it. But this is to rephrase my original intuition, so I suppose that the intuition you both share is different.

7) I had things I wanted to say about Pat's reply last night. One I will mention here is that, in my original quotation from the SEP Ontological Commitment article, I was not trying to pull the wool over anyone's eyes by leaving off the phrase "According to the third objection to sufficiency". I realize how lonely it is, where I stand on this, and never meant to suggest anything else.

8) I am grateful for this extended discussion. I now have a much better understanding of why I asked the original question, and where in the beautiful labyrinth of formal logic I might end up (at the Minotaur?) if I continued down the path of separating commitment from quantification.

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