The Impossibility of Certain Higher-Order Non-Classical Logics with Extensionality

Although this paper does not directly reference work done by Ed Gettier, I feel that it is an appropriate contribution to this volume in that it deals with two of the great intellectual loves of Ed’s life, higher-order logic and modal logic, and it deals with them in a ‘logic-chopping’ way that I rightly or wrongly think would please Ed.