Co‐Hyperintensionality

Co‐hyperintensionality, or hyperintensional equivalence, is a relation holding between two or more contents that can be substituted in a hyperintensional context salva veritate. I argue that two strategies used to provide criteria for co‐hyperintensionality (appeal to some form of impossible worlds, or to structural or procedural equivalence of propositions) fail. I argue that there is no generalized notion of co‐hyperintensionality that meets plausible desiderata, by showing that the opposite thesis leads to falsity. As a conclusion, I suggest to take co‐hyperintensionality as a primitive and I provide a general criterion of co‐hyperintensionality whose content depends on each hyperintensional notion we aim to formalize.