Definition
In writing an alternate history, the author makes the conscious choice to change something in our past. According to Steven H Silver, alternate history requires three things: 1) the story must have a point of divergence from the history of our world prior to the time at which the author is writing, 2) a change that would alter history as it is known, and 3) an examination of the ramifications of that change.
Several genres of fiction have been confused as alternate histories. Science fiction set in what was the future but is now the past, like Arthur C. Clarke's 2001: A Space Odyssey or Nineteen Eighty-Four , are not alternate history because the author has not made the conscious choice to change the past. Secret history, works that document things which are not known to have happened historically but would not have changed history had they happened, is also not to be confused with alternate history.
History of alternate history literature
Antiquity and Medieval
The earliest example of an alternate history is Book IX, sections 17-19, of Livy's Ab Urbe condita. Livy contemplated an alternative 4th Century BC in which Alexander the Great expanded his empire westward instead of eastward; Livy asked, "What would have been the results for Rome if she had been engaged in war with Alexander?"
Joanot Martorell's 1490 epic romance Tirant lo Blanc, written when the loss of Constantinople to the Turks was still a recent and traumatic memory to Christian Europe, tells the story of the valiant knight Tirant The White from Brittany who gets to the embattled remnant of the Byzantine Empire, becomes a Megaduke and commander of its armies, and manages to fight off the invading Ottoman armies of Mehmet II, save the city from Islamic conquest, and even chase the Turks deeper into lands they had conquered before.
19th century
One of the earliest works of alternate history published in large quantities for the reception of a popular audience may be the French Louis Geoffroy's Histoire de la Monarchie universelle: Napolon et la conqute du monde (1812-1832) (History of the Universal Monarchy: Napoleon And The Conquest Of The World) (1836), which imagines Napoleon's First French Empire victorious in the French invasion of Russia in 1811 and in an invasion of England in 1814, later unifying the world under Bonaparte's rule.
In the English language, the first known complete alternate history is Nathaniel Hawthorne's short story "P.'s Correspondence", published in 1845. It recounts the tale of a man who is considered "a madman" due to his perceiving a different 1845, a reality in which long-dead famous people are still alive such as the poets Burns, Byron, Shelley, and Keats, the actor Edmund Kean, the British politician George Canning and even Napoleon Bonaparte.
The first novel-length alternate history in English would seem to be Castello Holford's Aristopia (1895). While not as nationalistic as Louis Geoffroy's Napolon et la conqute du monde, 1812-1823, Aristopia is another attempt to portray a utopian society. In Aristopia, the earliest settlers in Virginia discover a reef made of solid gold and are able to build a Utopian society in North America.
Early 20th century and the era of the pulps
A number of alternate history stories and novels appeared in the late 1800s and early 1900s (see, for example, Charles Petrie's If: A Jacobite Fantasy ). In 1931, British historian Sir John Squire collected a series of essays from some of the leading historians of the period in the anthology If It Had Happened Otherwise. In this work, scholars from major universities as well as important non-university-based authors turned their attention to such questions as "If the Moors in Spain Had Won" and "If Louis XVI Had Had an Atom of Firmness". The essays range from serious scholarly efforts to Hendrik Willem van Loon's fanciful and satiric portrayal of an independent 20th century Dutch city state on the island of Manhattan. Among the authors included were Hilaire Belloc, Andr Maurois, and Winston Churchill.
One of the entries in Squire's volume was Churchill's "If Lee Had Not Won the Battle of Gettysburg", written from the viewpoint of a historian in a world where the Confederacy had won the American Civil War, considering what would have happened if the North had been victorious (in other words, a character from an alternate world imagining a world more like the real one we live in, although not necessarily getting all the details right). This kind of speculative work which posts from the point of view of an alternate history is variously known as a "recursive alternate history", a "double-blind what-if" or an "alternate-alternate history".
Another example of alternate history from this period (and arguably the first to explicitly posit cross-time travel from one universe to another as anything more than a visionary experience) is H.G. Wells' Men Like Gods (1923) in which several Englishmen are transferred via an accidental encounter with a cross-time machine into an alternate universe featuring a seemingly pacifistic and utopian Britain. When the Englishmen, led by a satiric figure based on Winston Churchill, try to seize power, the utopians simply point a ray gun at them and send them on to someone else's universe. Wells describes a multiverse of alternative worlds, complete with the paratime travel machines that would later become popular with U.S. pulp writers, but since his hero experiences only a single alternate world this story is not very different from conventional alternate history.
The 1930s would see alternate history move into a new arena. The December 1933 issue of Astounding published Nat Schachner's "Ancestral Voices," quickly followed by Murray Leinster's "Sidewise in Time". While earlier alternate histories examined reasonably straight-forward divergences, Leinster attempted something completely different. In his "world gone mad", pieces of Earth traded places with their analogs from different timelines. The story follows Professor Minott and his students from a fictitious Robinson College as they wander through analogues of worlds that followed a different history.
Time travel as a means of creating historical divergences
This period also saw the publication of the time travel novel Lest Darkness Fall by L. Sprague de Camp where an American academic travels to the Italy of the Ostrogoths at the time of the Byzantine invasion led by Belisarius. De Camp's work is concerned with the historical changes wrought by his time traveler, Martin Padway, thereby making the work an alternate history. Padway is depicted as making permanent changes and implicitly forming a new time branch.
Time travel as the cause of a point of divergence (creating two histories where before there was one, or simply replacing the future that existed before the time traveling event) has continued to be a popular theme: in Bring the Jubilee, by Ward Moore, the protagonist, who lives in an alternate history in which the South won the Civil War, travels through time and brings about a Union victory in the Battle of Gettysburg.
When a story's assumptions about the nature of time travel lead to the complete replacement of the visited time's future rather than just the creation of an additional time line, the device of a "time patrol" is often used. Such an agency has the grim task of saving civilization every day, every hour, with patrol membersepicted most notably in Poul Anderson's "Time Patrol"--racing uptime and downtime to preserve the "correct" history. This is eventually revealed to be the one in which humanity transforms itself into a benevolent super-species that, amongst other achievements, creates time travel to ensure its own existence.
This can lead to terrible moral dilemmas. In Delenda Est, the interference of time-travelling outlaws causes Carthage to win the Second Punic War and destroy Rome. As a result, there is a completely different Twentieth Century -- "not better or worse, just completely different". The hero, Patrol Agent Manse Everard, must return to that period, fight the outlaws and change history back, restoring his (and our) familiar historyut only at the price of totally destroying the world which has taken its place, and which is equally deserving of existence. The stakes are the highest imaginable: billions of lives balanced against other billions of lives, for one man to decide. "Risking your neck in order to negate a world full of people like yourself" is how the hero describes what he eventually undertakes.
A more recent example is Making History by Stephen Fry, in which a time machine is used to alter history so that Adolf Hitler was never born. Despite this however, a different leader resulted in Nazi Germany being more successful than it was under Hitler, with the Germans winning World War II and now in a Cold War with the United States.
Cross-time stories
H.G. Wells' "cross-time"/"many universes" variant (see above) was fully developed by De Camp in his 1940 short story "The Wheels of If" (Unknown Fantasy Fiction, October 1940), in which the hero is repeatedly shifted from one alternate history to another, each more remote from our own than the last. This subgenre was used early on for purposes far removed from quasi-academic examination of alternative outcomes to historical events. Fredric Brown employed it to satirize the science fiction pulps and their adolescent readersnd fears of foreign invasionn the classic What Mad Universe (1949). In Clifford Simak's Ring Around the Sun (1953), the hero ends up in an alternate earth of thick forests in which humanity never developed but where a band of mutants is establishing a colony; the story line appears to frame the author's anxieties regarding McCarthyism and the Cold War.[citation needed]
Also in the late 1940s and the 1950s, however, writers such as H. Beam Piper, Sam Merwin, Jr. and Andre Norton wrote thrillers set in a multiverse in which all alternate histories are co-existent and travel between them occurs via a technology involving portals and/or paratime capsules. These authors established the convention of a secret paratime trading empire that exploits and/or protects worlds lacking the paratime technology via a network of James Bond-style secret agents (Piper called them the "paratime police").
This concept provided a convenient framing for packing a smorgasbord of historical alternatives (and even of timeline "branches") into a single novel, either via the hero chasing or being chased by the villain(s) through multiple worlds or (less artfully) via discussions between the paratime cops and their superiors (or between paratime agents and new recruits) regarding the histories of such worlds.
The paratime theme is sometimes used without the police; Poul Anderson dreamed up the Old Phoenix tavern as a nexus between alternate histories. A character from a modern American alternate history Operation Chaos can thus appear in the English Civil War setting of A Midsummer's Tempest. In this context, the distinction between an alternate history and a parallel universe with some points in common but no common history may not be feasible, as the writer may not provide enough information to distinguish.
Paratime thrillers published in recent decades often cite the many-worlds interpretation of quantum mechanics (first formulated by Hugh Everett III in 1957) to account for the differing worlds. Some science fiction writers interpret the splitting of worlds to depend on human decision-making and free will, while others rely on the butterfly effect from chaos theory to amplify random differences at the atomic or subatomic level into a macroscopic divergence at some specific point in history; either way, science fiction writers usually have all changes flow from a particular historical point of divergence (often abbreviated 'POD' by fans of the genre). Prior to Everett, science-fiction writers drew on higher dimensions and the speculations of P. D. Ouspensky to explain their characters' cross-time journeys.
While many justifications for alternate histories involve a multiverse, the "many world" theory would naturally involve many worlds, in fact a continually exploding array of universes. In quantum theory, new worlds would proliferate with every quantum event, and even if the writer uses human decisions, every decision that could be made differently would result in a different timeline. A writer's fictional multiverse may, in fact, preclude some decisions as humanly impossible, as when, in Night Watch, Terry Pratchett depicts a character informing Vimes that while anything that can happen, has happened, nevertheless there is no history whatsoever in which Vimes has ever murdered his wife. When the writer explicitly maintains that all possible decisions are made in all possible ways, one possible conclusion is that the characters were neither brave, nor clever, nor skilled, but simply lucky enough to happen on the universe in which they did not choose the cowardly route, take the stupid action, fumble the crucial activity, etc.; few writers focus on this idea, although it has been explored in stories such as Larry Niven's All the Myriad Ways, where the reality of all possible universes leads to an epidemic of suicide and crime because people conclude their choices have no moral import.
In any case, even if it is true that every possible outcome occurs in some world, it can still be argued that traits such as bravery and intelligence might still affect the relative frequency of worlds in which better or worse outcomes occurred (even if the total number of worlds with each type of outcome is infinite, it is still possible to assign a different measure to different infinite sets). The physicist David Deutsch, a strong advocate of the many-worlds interpretation of quantum mechanics, has argued along these lines, saying that "By making good choices, doing the right thing, we thicken the stack of universes in which versions of us live reasonable lives. When you succeed, all the copies of you who made the same decision succeed too. What you do for the better increases the portion of the multiverse where good things happen." This view is perhaps somewhat too abstract to be explored directly in science fiction stories, but a few writers have tried, such as Greg Egan in his short story The Infinite Assassin, where an agent is trying to contain reality-scrambling "whirlpools" that form around users of a certain drug, and the agent is constantly trying to maximize the consistency of behavior among his alternate selves, attempting to compensate for events and thoughts he experiences but he guesses are of low measure relative to those experienced by most of his other selves.
Many writerserhaps the majorityvoid the discussion entirely. In one novel of this type, H. Beam Piper's Lord Kalvan of Otherwhen, a Pennsylvania State Police officer, who knows how to make gunpowder, is transported from our world to an alternate universe where the recipe for gunpowder is a tightly held secret and saves a country that is about to be conquered by its neighbors. The paratime patrol members are warned against going into the timelines immediately surrounding it, where the country will be overrun, but the book never depicts the slaughter of the innocent thus entailed, remaining solely in the timeline where the country is saved.
The cross-time theme was further developed in the 1960s by Keith Laumer in the first three volumes of his Imperium sequence, which would be completed in Zone Yellow (1990). Piper's politically more sophisticated variant was adopted and adapted by Michael Kurland and Jack Chalker in the 1980s; Chalker's G.O.D. Inc trilogy (1987-89), featuring paratime detectives Sam and Brandy Horowitz, marks the first attempt at merging the paratime thriller with the police procedural[citation needed]. Kurland's Perchance (1988), the first volume of the never-completed "Chronicles of Elsewhen", presents a multiverse of secretive cross-time societies that utilize a variety of means for cross-time travel, ranging from high-tech capsules to mutant powers. Harry Turtledove has launched the Crosstime Traffic series for teenagers featuring a variant of H. Beam Piper's paratime trading empire.
The concept of a cross-time version of a world war, involving rival paratime empires, was developed in Fritz Leiber's Change War series, starting with the Hugo Award winning The Big Time (1958); followed by Richard C. Meredith's Timeliner trilogy in the 1970s, Michael McCollum's A Greater Infinity (1982) and John Barnes' Timeline Wars trilogy in the 1990s.
Such "paratime" stories may include speculation that the laws of nature can vary from one universe to the next, providing a science fictional explanationr veneeror what is normally fantasy. Aaron Allston's Doc Sidhe and Sidhe Devil take place between our world, the "grim world" and an alternate "fair world" where the Sidhe retreated to. Although technology is clearly present in both worlds, and the "fair world" parallels our history, about fifty years out of step, there is functional magic in the fair world. Even with such explanation, the more explicitly the alternate world resembles a normal fantasy world, the more likely the story is to be labeled fantasy, as in Poul Anderson's "House Rule" and "Loser's Night."
In both science fiction and fantasy, whether a given parallel universe is an alternate history may not be clear. The writer might allude to a POD only to explain the existence and make no use of the concept, or may present the universe without explanation to its existence.
Major writers explore alternate histories
In 1962, Philip K. Dick published The Man in the High Castle, an alternate history in which Nazi Germany and Imperial Japan won World War II. This book contained an example of "alternate-alternate" history, in that one of its characters is the author of a book in which the Allies won the war.
It was followed by Vladimir Nabokov's Ada or Ardor: A Family Chronicle (1969), a story of incest that takes place within an alternate North America settled in part by Czarist Russia, and that borrows from Dick's idea of "alternate-alternate" history (the world of Nabokov's hero is wracked by rumors of a "counter-earth" that apparently is ours). Some critics believe that the references to a counter-earth suggest that the world portrayed in Ada is a delusion in the mind of the hero (another favorite theme of Dick's novels). Strikingly, the characters in Ada seem to acknowledge their own world as the copy or negative version, calling it "Anti-Terra" while its mythical twin is the real "Terra." Not only history but science has followed a divergent path on Anti-Terra: it boasts all the same technology as our world, but all based on wat