Literally, "double-walkers". To meet one's own supernatural double (or Scots "fetch") was traditionally an unlucky or fatal portent; a well-known treatment of this theme is Edgar Allan Poe's short story, "William Wilson" (in The Gift: A Christmas and New Year's Present, anth 1839 dated 1840), a tale that manifests the recurrent, compulsive focus of the Gothic (see Gothic SF) on Doppelgangers. Even when rationalized through sf devices – typically Time Travel – such encounters can still seem ominous, as when the protagonist of Isaac Asimov's The End of Eternity (1955) is filled with irrational dread by almost meeting his earlier self. Likewise, time-travelling characters in Dragonflight (fixup 1968) by Anne McCaffrey inadvertently trouble their younger selves with perceived portents. Participants in the Changewar of Fritz Leiber's The Big Time (March-April 1958 Galaxy; 1961 dos) are known as Doublegangers, having been split off from their timebound lives (which continue) to operate outside consensus reality. More genuinely alarming are doppelgangers which permanently replace human characters: Alien "pod people" in Invasion of the Body Snatchers (1956) or Robots in The Stepford Wives (1974).
A minor version of this frisson accompanies characters' sighting of human doubles which are about to be substituted for nefarious purposes, as in E E Smith's First Lensman (1950), James H Schmitz's A Tale of Two Clocks (1962; vt Legacy 1979), and very many Pulp-magazine and Comics scenarios: virtually every Superhero proves to have at least one exact double. Doubles are a staple of Ruritanian fiction and occasionally feature in straight sf, such as Robert Heinlein's Double Star (February-April 1956 Astounding; 1956). Shapeshifters (which see) often have the ability to become any selected person's double.
Exact doubles generated by side-effects of Matter Transmission or intentional Matter Duplication – as in Algis Budrys's Rogue Moon (1960; vt The Death Machine 2001) – raise more genuinely disturbing questions of personal Identity, as to a perhaps lesser extent does the potential coexistence of multiple instances of an Uploaded personality in Cyberspace (see Avatars). Apparent doppelgangers may also be found in Parallel Worlds – as in Keith Laumer's Worlds of the Imperium (1962 dos) – although their presence on a Counter-Earth in the film Doppelganger (1969) seems wildly implausible. [DRL]
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