Poe's most psychologically compelling story, "William Wilson" explores the ways in which we wrestle with the contradictions within ourselves and how we view our own flaws.
We meet William Wilson as a young boy, when he meets a boy in his school who shares his name, dresses just like him, and even shares the same birthday (and, incidentally, the same birthday as Poe himself). William is annoyed by the boy; his new companion is bossy, tells him what to do, and imitates his voice, though he can't speak louder than a whisper. Thus, he plans an attack on the other William Wilson, but when he sneaks into the kid's bedroom he finds his rival's face has changed, and what he sees terrifies him.
William meets the second William again when he begins conning people at gambling. William #2 exposes his vice, forcing him to leave Oxford. The last time William sees his tormentor, he is at a masquerade bash; there, he finds William #2 dressed in the same costume, and, furious at his presence, he decides to stab him. After the murder happens, William looks into a mirror and sees himself bleeding before hearing his rival admit defeat: “In me didst thou exist—and, in my death, see by this image, which is thine own, how utterly thou hast murdered thyself.”
Many people point to this compelling tale of dual selves as one of Poe's most personal, as William shares a birthday with Poe and is afflicted by the same gambling addiction which forced Poe to leave the University of Virginia after just one semester. Did Poe, like William, assassinate his own conscience so that his vices could reign supreme? Being that Poe reportedly died of "brain swelling," which was a euphemism for alcoholism at the time, it seems like an unfortunate possibility.