Intervention Effects Follow from Focus Interpretation*

The paper provides a semantic analysis of intervention effects in wh-questions. The interpretation component of the grammar derives uninterpretability, hence ungrammaticality, of the intervention data. In the system of compositional interpretation that I suggest, wh-phrases play the same role as focused phrases, introducing alternatives into the computation. Unlike focus, wh-phrases make no ordinary semantic contribution. An intervention effect occurs whenever a focus-sensitive operator other than the question operator tries to evaluate a constituent containing a wh-phrase. It is argued that this approach can capture the universal as well as the crosslinguistically variable aspects of intervention effects, in a way that is superior to previous approaches. Further consequences concern other focus-related constructions: multiple focus data, NPI licensing, and alternative questions.