Interpolation for First Order S5

An interpolation theorem holds for many standard modal logics, but first order S5 is a prominent example of a logic for which it fails. In this paper it is shown that a first order S5 interpolation theorem can be proved provided the logic is extended to contain propositional quantifiers. A proper statement of the result involves some subtleties, but this is the essence of it.

• Type: Journal
• Year: 2002
• Where: JSYML
• Authors: Melvin Fitting
• Keywords: JSYML 2002, Logic, Order S5 Interpolation, Standard Modal Logics