A doppelganger — also written "doppelgaenger" or "doubleganger" — is quite simply a double. It can be a ghost or physical apparition, but it is usually a source of psychological anxiety for the person who sees it. The word comes from the German Doppelgänger, literally meaning "double-goer," and has found widespread use in popular culture.
Many different types of doppelganger have arisen in cultures around the world. A doppelganger may be an "evil twin," unknown to the original person, who causes mischief by confusing friends and relatives. In other cases, the double may be the result of a person being in two places at once, or even an individual's past or future self. Other times, the double is merely a look-alike, a second individual who shares a strong visual resemblance. The goals of the doppelganger often depend on the role it plays for the original person.
In folklore, the doppelganger is sometimes said to have no shadow or reflection, much like vampires in some traditions. These doubles are often malicious, and they can haunt their more innocent counterparts. They may give bad advice or put thoughts in their victim's heads. Seeing one's own doppelganger or that of a friend or relative is usually considered very bad luck, often heralding death or serious illness. In some traditions, a doppelganger is considered a personification of death.
In Freudian psychoanalysis, the doppelganger is often viewed as an aspect of an individual's self that he or she is struggling to control. The double usually has both similar and opposing characteristics to the original. In other words, the double will be recognizable as the individual, but will act differently, often in an extreme manner. Often, the repressed aspect of the psyche that the double represents must be confronted and ultimately defeated in order for it to go away.
In Literature and Film
Doppelgangers appear often in various forms of fiction, from stories of mistaken identity to more supernatural phenomena in works of science fiction, fantasy, and horror. Robert Louis Stevenson's The Strange Case of Dr. Jekyll and Mr. Hyde is a famous example of the doppelganger in literature. Alfred Hitchcock's movie Psycho features Norman Bates, whose image often appears in mirrors and windows, suggesting there is more to him than just a mild-mannered hotel manager.
There are many famous accounts of doppelgangers in history. Guy de Maupassant's short story "Lui?" (called "The Terror" in English) tells of the writer's own experience with a double. English poet John Donne claimed to have met his wife's look-alike in Paris shortly before his daughter was stillborn. Poet Percy Bysshe Shelley and American president Abraham Lincoln both reportedly saw doppelgangers shortly before their deaths; Shelley saw his in a dream and Lincoln as a second face in his mirror.