The literary function of a doppelganger is typically to act as a representation of some aspect of a character, usually as an “evil twin” or in a similarly dark capacity. This may be used as a plot device to drive conflict in the story, such as an antagonist who is identical to the protagonist and whose actions result in difficulty for that protagonist. It can also be more metaphorical in nature, perhaps acting as an illusion or hallucination that reveals information about a character. In more fantastical stories, this figure may even be part of the character, perhaps the darker aspects of the protagonist that have been separated and allowed to act without conscience.
A doppelganger, a term that is borrowed from German and literally translates as “double walker,” is a figure that is physically identical to another person. In literature, this person is typically identical to a main character, often the protagonist of the story. One of the main ways in which this type of character can be used is to harass or create conflict for the protagonist. While one may be supernatural in origin, it could just as easily be an identical twin. The actions of this “other” can then result in consequences for the protagonist, creating conflict as the main character tries to undo these actions.
In some stories, a doppelganger may be more metaphorical and less literal. Someone, for example, might have a dream or experience a hallucination in which he or she sees himself or herself perform some action or say something significant. A character in a story who is keeping a terrible secret, for example, might be chastised by his or her own reflection as a symbol for his or her conscience and guilt. While a character simply talking to himself or herself can work in a story, it may be more powerful for that character to actually see a figure who represents inner conflict or distress.
A doppelganger in a story may also function in a more supernatural manner, often as an agent of mischief or representing some unacknowledged facet of a character. Robert Louis Stevenson’s Strange Case of Dr. Jekyll and Mr. Hyde, for example, uses this idea in a slightly altered way to portray the darker and more violent side of humanity. A character in a story could be split in two, with all of the violence and instinct within himself or herself materializing in a physical way. This creates direct conflict, not necessarily because people think the protagonist is acting in a certain way, but as an external representation of the character’s inner conflict or struggle that he or she must literally defeat.