In "The Tell-Tale Heart", what reasons does the narrator give for commiting the murders?
In "The Tell-Tale Heart" the narrator says that the idea of murdering the old man came about because of his eye:
Yes! it was this! He had the eye of a vulture....Whenever it fell upon me my blood ran cold; and so by degrees, very gradually, I made up my mind to take the life of the old man and rid myself of the eye forever.
When the narrator finally sees the eye open on the eighth night, he becomes "furious" as he gazes "upon it." Then, he hears the beating of the old man's heart, and the narrator declares that
It increased my fury, as the beating of a drum stimulates the soldier into courage.
When "the hellish tattoo of the heart increased," the narrator becomes excited to "uncontrollable terror" and has "anxiety" that the sound will be heard by a neighbor, so he throws open the lantern and rushes into the room and kills the old man. Of course, this anxiety and imagining of the beat of the heart later induces the narrator to confess his crime. His hypersensitivity, like that of Roderick Usher in another story of Poe's, leads to his demise.