Ernest Hemingway often spoke about his "iceberg theory" of story-telling, which involved leaving out expository details. Poe did the same thing many years earlier, and for the same reason. Exposition, like description, impedes drama. (Henry James is often quoted for saying: "The ever important murmur, 'Dramatize it, dramatize it!') Poe avoids all unnecessary exposition with the fiction that Montresor's entire narrative is communicated in secrecy to a confidante whom he addresses in the opening paragraph as "You, who so well know the nature of my soul."