Insanity is a term often used as if it had a medical meaning, but in truth, insanity is a legal concept. Under this concept, Montresor in Edgar Allan Poe's story "A Cask of Amontillado" would certainly be classified as mentally unbalanced but would also be deemed sane under the law. This is because while the actions he takes might be considered insane by many people, he does them knowing that what he is doing is wrong.
In the Poe story, the tale is told by Montresor, who will also be the murderer, and the reader experiences his madness directly because he tells his own story. The horror story by Poe gains power by having the protagonist tell the story. This is a story that features a theme repeated in several Poe stories, that of being buried alive, and here the victim is walled up by his enemy and left to die. The fact that this theme is repeated again and again in Poe recalls his own sense of living death in his life and his fear of being entombed. Montresor's hatred of Fortunato is evident from the first line: "The thousand injuries of Fortunato I had borne as best I could, but when he ventured upon insult I vowed revenge" (Poe 1). This revenge takes a particularly horrible form, and in the story, the fact that the reader is privy to Montresor's thoughts from the first allows the reader to observe the reactions of Fortunato in a way that contributes to the horror as Fortunato discovers the fate Montresor has in mind for him. Even though Montresor tells the story, we are able to have sympathy for Fortunato as well as for the tormented Montresor.
Montresor shows from the first a concern that his action go unpunished:
I must not only punish but punish with impunity. A wrong is unredressed when retribution overtakes its redresser. It is equally unredressed when the avenger fails to make himself felt as such to him who has done the wrong (1).
Thus, Montresor both wishes to assure that the world never learns w...