Intensionality and hyperintensionality

Roughly speaking, the extension of an expression is what it picks out in our world: an object for a name, a set of objects for a predicate, and so on. Sometimes information about the extensions of terms is not enough to fully specify how those expressions contribute to the truth-value of sentences that they appear in. Many hold there is a further aspect of meaning, the intension of an expression. This is enough to at least determine the extension of an expression in any possible circumstance. Increasingly, theorists are recognizing distinctions between expressions that have the same extension in any possible worlds: these distinctions are known as hyperintensional distinctions.

A number of philosophical disagreements are framed in terms of these questions, in the philosophy of language and beyond. There are issues about whether we even need to go beyond extensional language for a theory of the world, and if we do so whether we need hyperintensional distinctions as well, and if so for what. There are also questions that arise about what framework we should employ for an intensional semantics, or a hyperintensional one.