[from Stanley Fish's How Milton Works, 2001]
In speech act theory (as originated by J. L. Austin) . . . a "declarative" [is] an utterance that brings into being the state it names, and does so by virtue of the unique authority of the speaker (when an umpire declares "You're out," you're out, but when a fan or fellow player says it, he succeeds only in expressing his opinion).
How Milton Works