Doppelanger

Doppelänger: A literary technique by which a character is duplicated (usually in the form of an alter ego, though sometimes as a ghostly counterpart) or divided into two distinct, usually opposite personalities. The use of this character device is widespread in nineteenth- and twentieth-century literature, and indicates a growing awareness among authors that the "self" is really a composite of many "selves." A well-known story containing a doppelgänger character is Robert Louis Stevenson's Dr. Jekyll and Mr. Hyde, which dramatizes an internal struggle between good and evil. The convention first gets established in literature through German gothic fiction of the turn of the nineteenth century, and through that tradition influenced Mary Shelley's Frankenstein.