In the introduction of the short story, "The Tell-Tale Heart," by Edgar Allan Poe, the narrator tries to convince the reader of his sanity. He says that he is nervous and has been, but that he is definitely not mad (insane). He goes on to tell the audience exactly how they should know he is not crazy. First, he says that his senses were sharper than normal, especially his hearing. It was so good, in fact, he says,
"I heard all things in the heaven and in the earth. I heard many things in hell. How, then, am I mad? Hearken! and observe how healthily---how calmly I can tell you the whole story." (Poe 1)
The narrator goes on to tell the reader all about his plan to kill the old man because of his eye. In trying to convince everyone of his sanity, he ends up doing just the opposite.