A theory of radical interpretation gives the meanings of all sentences of a language, and can be verified by evidence available to someone who does not understand the language. Such evidence cannot include detailed information concerning the beliefs and intentions of speakers, and therefore the theory must simultaneously interpret the utterances of speakers and specify (some of) his beliefs. Analogies and connections with decision theory suggest the kind of theory that will serve for radical interpretation, and how permissible evidence can (...) support it. (shrink)