A term first used in a restricted sense by Murray Leinster in "Pocket Universes" (October 1946 Thrilling Wonder), where it is a "contrivance" rather than an encompassing world. It might broadly be said that the inhabitant of any constricted environment lives in a pocket universe, whether as a child, a prisoner, a victim of dementia, a chained watcher in Plato's cave, a resident of Hell or an inhabitant of the world inside Pantagruel's mouth. It might also be suggested that the dynamic moment of escape from confinement – a leitmotiv of Western literature – almost inevitably marks the transition from a pocket universe to a fuller and more real world. In the final pages of Mark Twain's The Adventures of Huckleberry Finn (1884), when Huck figures he "got to light out for the Territory ahead of the rest", he is anticipating his "escape" from aunt Sally in order to be free of the overgoverned social organization and its conservative inwardness of gaze that she represents: a hierarchical boundedness that has many of the psychological characteristics of the pocket universe as found in sf: that Huck will almost certainly find no freedom in the Territory is a fate beyond the pages of Huckleberry Finn (see Slingshot Ending), just as life under the stars tends to be pointed at, rather than lived, as most Pocket Universe tales come to a climax. The classic movement of the sf tale is of course outward – via Conceptual Breakthroughs and all the other forms of initiation or unshackling – and in that sense most sf works contain some sort of pocket universe, implied or explicit, which initially binds and blinds the protagonist, and from which it is necessary to escape; and most sf works lose momentum if they try to inhabit the new world on offer.
Two usages of the term seem useful, one broad, the other narrower. It can be used broadly to describe an actual miniature universe pocketed within a larger explanatory frame or device – like the various godling-crafted worlds nesting within one another in Philip José Farmer's World of Tiers sequence; or like the hidden redoubts that feature in so many Lost Race tales; or like the "natural" miniature universes observed in such works as Gregory Benford's Cosm (1998); or like the set-ups in almost any of Jack L Chalker's series (e.g., the Well World sequence and the Four Lords of the Diamond tetralogy) which feature universes constructed by godlike beings as Godgame labyrinths and inhabited by victim-players who must solve their universe to escape from it; or like similar 1950s set-ups (see Paranoia) such as in Frederik Pohl's "The Tunnel Under the World" (January 1955 Galaxy) or Philip K Dick's Time Out of Joint (1958), whose protagonists are victims of artificial worlds shaped to delude and manipulate them; or like the inverse scenario in which human protagonists are the manipulators of artificial life, ranging from Theodore Sturgeon's "Microcosmic God" (April 1941 Astounding) to the sophisticated AI-Evolution of Greg Egan's "Crystal Nights" (April 2008 Interzone); or (again trivially) like any fantasy game which involves Role-Playing Game activity within a Virtual-Reality world; or in fact like any world (such as that on which John Crowley's The Deep  is set, or Terry Pratchett's Discworld) whose origins and extent reflect a sense of constraining artifice.
But none of these applications contains the one essential element that defines the true pocket-universe tale: Farmer's and Chalker's protagonists may not know the nature of the worlds in which they find themselves, but they do know that they are inhabiting some form of construct. In the pocket-universe tale as more narrowly defined, the world initially perceived seems to be the entire world, not a Keep within a larger frame, and the web of taboos preventing the truth about its partial nature being known is structurally very similar to the parental restrictions which initially hamper the move through puberty into adulthood of the young protagonists of most non-genre juveniles. It could, indeed, be argued that this move through puberty is a particular example of the Conceptual Breakthrough which arguably structures all genuine sf.
The classic Generation-Starship tale is one in which the descendants of the original crew members have forgotten the true nature of things and have instituted a repressive, Taboo-governed society which suppresses any attempt to discover the truth; it is the task of the young protagonist to break through the social and epistemological barriers stifling this world while at the same time successfully managing puberty. The pure Generation-Starship story embodies, therefore, the purest form of the concept of the pocket universe. Examples of that pure form, though central to sf, are not numerous – Robert A Heinlein's Universe (May 1941 Astounding; 1951 chap) is the most famous in the list, which includes also Brian W Aldiss's Non-Stop (1956 Science Fantasy #17; exp 1958; cut vt Starship 1959), Harry Harrison's Captive Universe (1969); but Alexei Panshin's Rite of Passage (July 1963 If as "Down to the Worlds of Men"; exp 1968), for instance, though explicitly a tale of puberty, does not suggest that there is any epistemological mystery about the nature of the asteroid-sized starship from which its heroine must escape. The growth into redemptive adulthood of Silk in Gene Wolfe's Book of the Long Sun sequence (1993-1996) soon absorbs the model into more complex concerns. A good late example of the form, such as Stephen Baxter's Ark (2009), is unlikely to emphasize the Pocket Universe/puberty linkage, which has now become a Cliché, though Paul Chafe returns to it in his Ark sequence opening with Genesis (2007).
All Post-Holocaust tales in which the descendants of survivors live in Underground habitats which they think to be the whole of reality are pocket-universe stories. The best of them is perhaps Daniel F Galouye's Dark Universe (1961), though Margaret St Clair's Sign of the Labrys (1963) and The Shadow People (1969) play fruitfully with the concept, as do Richard Cowper's Kuldesak (1972), Roger Eldridge's The Shadow of the Gloom-World (1977) and many others. In all these stories, the essential movement is from childhood constriction and taboo-driven ignorance to adult freedom and breakthrough; in Genre SF it is only more recently that ironies have significantly pervaded this pattern, as in David J Lake's Ring of Truth (1983), where a traditional enclosed world turns out to be interminably extensive, so that there is, in fact, no exit. In the great pocket-universe stories, however, there is always an out, a Sense of Wonder, a new world opening before the opened eyes.
Another kind of pocket universe may be inescapable because it inhabits a "space loop" analogous to a Time Loop. This is foreshadowed by the Fantasy garden whose paths somehow never reach the centre in Lewis Carroll's Alice's Adventures in Wonderland (1865), echoed by the similarly elusive city-square park of John Crowley's Little, Big (1981). Thus all attempts to leave the oppressive Island in "No Ships Pass" (May 1932 The Story-teller) by Lady Eleanor Smith (1902-1945) – perhaps a huis clos Afterlife realm [see The Encyclopedia of Fantasy under links below] – return the fugitive to its shores; exits from the shabby basement-room of "Eternity" in Flann O'Brien's The Third Policeman (written circa 1940; 1967) lead back into the same room or an identical one; the shared-hallucination pocket universe of Richard M McKenna's "Fiddler's Green" (in Orbit 2, anth 1967, ed Damon Knight) has a single archetypal tree which journeyers in any direction must pass again and again. More science-fictionally, Arthur C Clarke's "The Wall of Darkness" (July 1949 Super Science Stories) and Theodore Sturgeon's "What Dead Men Tell" (November 1949 Astounding) make use of topological quirks (see Mathematics); in Clarke's tale, the titular wall which presents the central challenge has, like the famous Möbius strip, no other side. The remarkable seeming pocket universe in Susanna Clarke's Piranesi (2020) presents itself as a Labyrinth-like edifice, crowded with statuary, which may extend to infinity in all horizontal directions.
For pocket universes within the literal Inner Space of the human mind, see Dream Hacking. [JC/DRL]
see also: Chronomaster; Gods and Demons; Zone.
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