Pundits puzzle over why it should be that fantasy, that nostalgic adoration of swords and sorcerers, elfin mariners whose silver ships breast the winedark starlit seas of myth, and science fiction, that futuristic admiration of lightsabers and Lensmen, space marines whose silver starships soar the starry vacuum of space, attracts much the same audience.
At first glance, one would think the two genres opposites. Upon second glance, they seem to be two suburbs of the came city of imagination, so much so that a special names, speculative fiction or SFF, has been concocted to express the mixed group. They are seated next to each other in the bookstore, and certain magazines, most notably the Magazine Of Fantasy And Science Fiction, caters to both.
Science Fiction readers and fantasy reader overlap to a degree greater than those of, for example, fantasy readers and readers of historical novels, whom one would suppose would be a natural overlap. One would suppose it natural after finishing reading Steven PressfieldGATES OF FIRE or Mary Renault's THE KING MUST DIE or Sharon Kay Penman's SUNNE IN SPLENDOR to turn to Robert E. Howard's tales of Conan the Cimmerian, or to Tolkien's THE RETURN OF THE KING or to the Lyonesse Trilogy of Jack Vance; but in truth the readers of the deeds of Hyborians, Hobbits or inhabitants of Hybras are more likely to have just finished reading about the Slans or Silkie of A.E. van Vogt rather than Centurions or Saxon of Alfred Duggan. But why?
Much ink has been spilled defining science fiction or defending definitions, but one element is at the center of all the disputes. Everything other form of genre work, from detective novels to westerns, take place in what is recognizably this world. Sciencefictioneers build new worlds.
Whatever takes place in a world whose rules and expectations are an invention of the author, and ergo should be explained by the author to the reader, is speculative fiction.
A new world is one where some counterfactual premise is treated with perfect seriousness, and the ramifications, unexpected yet logical, are drawn out. It is a world not our world, either because it is in the future, or in a past that never existed, or because our world is an illusion masking a much stranger buried reality into which the story falls.
A new world is a setting. A writer of boy's adventure stories or horror tales who uses one supernatural or unearthly element in his story is not necessarily writing fantasy; a writer of spy thrillers who introduces a plausible but unreal bit of futuristic technology is not necessarily writing speculative fiction, because the new rules of the new world need not be explained to the reader. One or two props do not a new world make.
On the other hand, if a story that would otherwise be merely a spy thriller or a crime drama includes a unreal bit of futuristic technology, and that the author has thought through the unexpected ramifications of that technology, and the author's world is depicted as having suffered those ramifications, all of which must be explained to the reader, that makes it arguably science fiction.
If the prop changes the setting, it is a new world. A current example might be the film INCEPTION. The dream-reading technology has several ramifications which the film mentions or explores: even though INCEPTION takes place in streets, hotels and icy mountain fortresses of what seem to be our modern world, it is not our world, and the film maker spent a scenes and screen-time describing the rules of his world, saying what would happen if you died in a dream, establishing the danger of limbo, explaining why the projections grow hostile, et cetera.
This definition does not count Dante's INFERNO, nor the INTERVIEW WITH A VAMPIRE by Anne Rice to be fantasy. Every one of Dante's readers knows what hell is. Every one of Anne Rice's readers knows what a vampire is. When you, the author, use stock from the warehouse of the reader's imagination, you need not explain what anything is, except, perhaps, to say in what way your particular version of hell or vampirism differs from the norm. (An Anne Rice vampire cannot turn into a bat, for example).
This definition would not count ITS A WONDERFUL LIFE or A CHRISTMAS CAROL as fantasy, even though one has an angel and an alternate timeline, and the other has time travel and ghosts.
These elements are unearthly and supernatural, but (and here is the crucial difference) angels and ghosts, visions and miracles are part of the cultural background familiar to all English readers. There are certain fantastic elements that are part and parcel of the Anglo-American commonwealth of letters that don't need to be explained because the writer did not invent them, and is not using them in an unusual way. When an angel hears and responds to the prayers overheard in the opening scene of ITS A WONDERFUL LIFE, the audience for whom the work is meant, even those who do not believe in angels, can be expected to know what these beings are. If the opening scene had an ameshashpand instead of angels, the intended audience would not have known what these beings are, and cannot be expected to know (unless the audience includes Zoroastrians).
For that matter, if you sit down to read the Mahabharata, the sage Vyasa expects you, the reader, (even if you are a Western reader) to understand the rules of his world and world-view without it being explained to you. He is not writing a fantasy in that he is not making it up: you simply have the misfortune of not being inside his expected audience. Likewise, the author of BEOWULF expects you, the reader, (even if you are a modern reader) to know the world he is describing, even if you yourself have never met the nicors or monsters or mothers of monsters, or fiery dragons that his hero meets.
This definition admits of degrees. Some books and stories are more speculative fiction and some are less. The degree depends on the how much imaginative work is demanded of the reader.
Indeed, it is to be noticed that the fantasy stories invented before JRR Tolkien, such as the Third Hemisphere of Lord Dunsany, the Hybornian Age of Robert E. Howard, the Barsoom of Edgar Rice Burroughs, or the Mercury of E.R. Eddison, the World's End or other pastel landscapes of William Morris, were notably unique. These writers made new worlds. They added something new to the reader's stock of imaginary objects, people and places. They demanded a reader who was willing to imagine a whole new world.
The plethora of Tolkien imitators that followed him have earned the less admiration from readers and critics alike, not necessarily because the story-telling is good or bad, but because the world invention is not taking place. The imitators are merely following the world of Tolkien (or of Gary Gygax), taking it as a stock prop out of the warehouse of the reader's imagination. They are not adding anything new into the warehouse. They make no demand on the reader's imagination.
No doubt, dear reader, you are goggle-eyed with disbelief, thinking that Professor Tolkien did not invent any new trope or race or prop. Surely the One Ring is merely Wagner's Ring; the elves are the liosalfar of Norse Myth; the dwarves are the miners from nursery tales as old as Snow White; the dragon is older than literature; the Dark Lord is merely Satan; the Dark Land is merely Hell set in a landscape of industrial pollution.
But bear in mind out definition includes drawing out the ramifications of a counterfactual. Any fairytale might have fairies in it, but if Professor Tolkien had been writing Disney's Cinderella, we would have know the pedigree, language, letters, customs, and genealogy of the fairy godmother, including the names of the sunken islands in the West from which her people, fleeing mortal lands, dwelled for centuries in bliss, turning mice into coach-horses.
In science fiction, those stories that merely use stock props are usually called 'Space Opera' and are rightly dismissed as not making any demand on the reader's imagination.
The writers, for example, of Alexander Raymond's FLASH GORDON merely made a raid on the warehouse of the imagination where all the hoary old tropes of boy's adventure fiction were stored, and threw them together without any particular world-building at all. The ramifications of no particular element are drawn out. Ming the Merciless is merely Fu Manchu with the serial numbers filed off, crossed with any number of Oriental despots, Roman emperors or mad scientists; Princess Aura is Fah lo Suee; Prince Baron is Robin Hood, even down to the Lincoln Green and feathered caps of the Merry Men; King Vultan is a hawk-winged Viking; even the critters of planet Mongo are merely props from THE LOST WORLD by Sir Author Conan Doyle. Indeed, the world building is so incoherent that when the underground kingdom of Azura, Queen of Magic, comes on stage, and Flash Gordon turns out to be the reincarnation of her old lover, playing Callicrates to her Ayesha She-Who-Must-Be-Obeyed, the introduction of magic and reincarnation does not even jar against what has already been established about the world.
STAR WARS is likewise simply a raid on the warehouse of the imagination that adds little or nothing new to it: the Empire is the Roman Empire in space, complete with centurions and Nazi-named storm troopers; the light-sabers are kendo swords; the Jedi-Knights are space samurai with Way Cool mind powers which are not even defined in terms of what they can and cannot do. (We do not find out that telekinesis is included in the package until the second movie); the aliens are simply critters, exercises in fantastic make-up, without anything particularly alien about them. We would recognize a Vulcan from STAR TREK or a Sabacean from FARSCAPE even if they appeared out of make up under other names (such as Houyhnhnm or Spartan) but can the same boast be made of Wookies or Kalimari? No, because they have no world behind them.
This is not to say that Tolkien clones or Space Opera necessarily are not beloved and memorable and entertaining stories. Indeed, my favorite films and books of all time fall squarely into this category. But it is to say, such things are not examples of good world building.
In fact, I will go so far as to say the most popular stories of all have the worst world building. I point my finger at the DC or Marvel Universe as described by decades of comic books and graphic novels, and I point my finger at the world of Harry Potter.
No one, I hope, will argue that these monuments of imagination lack entertainment value. I argue only that the specific art of world-building, that is, the art of drawing out the unexpected but logical ramifications of the counterfactual speculation, are not present here, and, indeed, may not be needed or wanted.
The World of Harry Potter has witches in pointy hats who ride brooms, warlocks with magic wands, and no one unfamiliar with Halloween would fail to know or recognize these props. However, the world of the magicians is entirely unmagical, even to the point of being staffed with stuffy English bureaucrats and schooled by strict English schoolmasters.
The fairy-world elements are merely jokes or mockeries of England, with owls for postmen, gold for pounds, dementors for policemen, and so on. Indeed, the whole appeal of J.K. Rowlings world, the reason why it is so accessible to readers of every age, is that the fairy world has no elements of faerie, nothing of unearthliness or strangeness, nothing of wonder or horror or reverence or awe in that world and that setting at all: it is completely pedestrian, and makes not a single demand on any reader's imagination. I am not criticizing! This is one of many things the author did right to make her books the most popular in the decade. But there is no world built here. The fairy world is run not by the Wise of Roke, the Istari of the Uttermost West, and certainly not by Oberon, Ozma or Aslan, but by the officious and ineffective Ministry of Magic.
Imagine the real difference that would obtain in a judicial system where a technique as effective as the magic lasso of Wonder Woman for forcing witnesses to tell the truth obtained, or where the love potions that drove Tristran and Iseult to death were available in every apothecary shop.
The truth potions and love potions of Harry Potter's world, if the author were writing speculative fiction, would have endless ramifications in every area from courts of law, to courtship, to courting, to notions of courtesy.
But the author is not interested in world building. The magic of the magical world leaves not only the muggle world unchanged in Harry Potter, the enchanted version of England is not different from the fields we know, they merely use sink spells and house elves rather than dishwashing machines. They clean their forks and platters.
Likewise, the world of DC comics or Marvel is our world, not futureworld or fairyland.
While it may strain credulity, one of the accepted tropes or conventions of the superhero genre is that the world not be changed by the presence of the supernatural, supernormal and supertechnological heroes. (I would argue that WATCHMAN by Alan Moore is arguably science fiction, not superhero fiction, because it sets aside that convention, and dares to have the world change.)
The world defended by the Justice League of America or the Teen Titans has extraterrestrials, Amazons, mindreaders, witches, cyborgs, and reincarnated Egyptian princes with antigravity wings, but none of these inventions, discoveries, or fantastic elements has any effect on the world outside (except perhaps for a secret military, espionage or police teams using futuristic weapons).
Count the changes and ramifications of his world caused by Michael Valentine Smith, the Man from Mars in Heinlein's STRANGER IN A STRANGE LAND, and compare them to the non-changes and non-ramifications caused by the Martian Manhunter or Superman; compare the difference between the world unchanged by the Metal Men or the Doombots or Brainiac and the much-changed world described in Asimov Robot stories; compare the invaded Earth of HG Wells' WAR OF THE WORLD or Arthur C. Clarke's CHILDHOOD'S END with the invasions by Thanagar or Apokalypse.
Compare the world of Robert Sheckley's IMMORTALITY INC., where the existence of reincarnation changes everything, with that of Hawkman, where the existence of reincarnation changes nothing.
In a story with world building, the invention of the antigravitic ninth metal would change everything, from floating buildings to the means and methods of warship, to aerospace travel, to the size of women's hats.
The Justice League satellite is also equipped with a Star Trek style teleportation beam to transport the heroes to and from their various missions; Nightcrawler of the X-Men is likewise a teleportationist. Compare and contrast the utilization of teleportation in Justice League with stories by Alfred Bester or by Larry Niven.
Niven and Bester were writing science fiction, not Space Opera, because they thought through the implications of teleportation, from where the excess momentum goes when you teleport form the pole to the equator, to how you could lock up a criminal who can jaunt to any spot he can see.
The secret of world building is the secret of details. In the same way that the invention of the stirrup ushered in the Era of Knighthood, the invention of gunpowder ushered it out, and along the way everything, from the details of castle construction to the social and legal mores of feudalism changed and adapted, so too is the writer of speculative fiction beholden to change everything in his fictional world, and think through the ramifications the reader will not see until you show him.
You might protest that deducing and devising all the implications and ramifications of a new technology or the reality of mystical otherworldly magic is too much work for the poor author of speculative fiction. Well, the writers of regency romances are given the task of learning the period of the Regency, because the readers expect it. The writers of mysteries have to figure out the crime, and plant the clues, and the red herrings, all in advance, and think through all the ramifications there. The writers of navy stories are well expected to know the difference between the head in the ship and the bow in a ship, and the writers of pirate tales should know what a Privateer is, or where Tortuga lies.
Your mission as a writer of speculative fiction is to speculate.