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Full Idea
Extensionalists hold that quantifiers in predicate logic presuppose the existence of whatever objects can be referred to by constants or bound variables, or enter into true predication of properties.
Gist of Idea
Extensionalists say that quantifiers presuppose the existence of their objects
Source
Dale Jacquette (Intro to 'Philosophy of Logic' [2002], §4)
Book Ref
'Philosophy of Logic: an anthology', ed/tr. Jacquette,Dale [Blackwell 2002], p.5
A Reaction
I have strong sales resistance to this view. Why should a procedure for correctly reasoning from one proposition to another have anything whatever to do with ontology? A false world picture can be interconnected by perfect logic.
| 13606 | Humean conceptions of reality drive the adoption of extensional logic [Ellis] |
| 13821 | Extensionality is built into ordinary logic semantics; names have objects, predicates have sets of objects [Bostock] |
| 13362 | If an object has two names, truth is undisturbed if the names are swapped; this is Extensionality [Bostock] |
| 9458 | Extensionalists say that quantifiers presuppose the existence of their objects [Jacquette] |
| 21719 | Extensionalism means what is true of a function is true of coextensive functions [Linsky,B] |