I came across a remark in a lit-crit book, THE NARRATIVE OF REALISM AND MYTH, where author Greg Lucente argued that “myth” described worlds where time and space could be transcended, while “realism” described worlds where they could not be transcended. I’ve always felt that formula could have application to SF and fantasy, but others’ mileage may vary.Lucente's use of the term "myth" in this lit-crit book is highly idiosyncratic-- possibly even more so than my own, which I'll get to later. I wouldn't use "myth" this way myself, but I think that he's onto something by saying that's a mental distinction on the way readers think about time and space, specifically with regard to the differences in science fiction and fantasy.
It's beyond question that both genres are grounded in producing a wide spectrum of marvelous effects, many of which go far beyond the perimeter of known science. Some practitioners of science fiction don't hold with venturing into that "terra incognita;" allegedly at one point in his life, the late L. Sprague de Camp vowed that he wouldn't write any space-opera stories because he didn't believe in the real-world possibility of "hyperspace" and similar devices.
De Camp and his "camp" are certainly in the minority, though. For most practitioners of science fiction, it doesn't really matter whether or not mankind ever discovers a method of scientifically transcending the boundaries of time and space and so building galactic empires. Devices like "hyperspace" are tools by which authors can tell stories, whether they're wild adventure-epics like STAR WARS or relatively realistic dramas like Joe Haldeman's THE FOREVER WAR.
Nevertheless, though the majority of SF-writers perforce make up their technologies, their alien life-forms, etc., out of whole cloth, they don't entirely toss out the basic notion of science fiction, which is that scientific innovation proceeds out of incremental advancements in technological knowledge. No matter many SF-miracles a given writer may pull out of his hat, the general expectation for the genre is that space and time cannot really be transcended, only circumvented. Indeed, as heady as STAR WARS is, with its infusions of quasi-magic and mysticism, one of the original film's charms is that the characters exist in a world where machines get old and break down-- which is the very reason Luke Skywalker's uncle needs to buy a pair of new droids.
Now, fantasy is much less unified in its appeal than science fiction, and even the type I usually address here-- the "otherworldly fantasy"-- is divided into at least two major types, the "nonsense fantasies" of Lewis Carroll and similar authors, and the "mythic fantasies" of Tolkien, Lewis, Howard and many others. Putting aside the first type as irrelevant to this discussion, I would say that mythic fantasies usually (though not inevitably) endeavor to reproduce a mythology of magic and/or sorcery. This mythology is usually the source of the fantasy-author's miracle-making "devices." In rare instances some authors will introduce something comparable to the miracle-technology of straight science fiction, as when Lin Carter mixes Burroughsian technology with sorcerers in a work like THE WIZARD OF LEMURIA, his initial "Thongor" novel.
Not all mythic fantasies appeal to magical beings like Lewis' "Aslan" or Tolkien's "Valar." Nevertheless, writers who invoke miracles of magic and sorcery usually have to posit some source for their sorcerers' powers, and the default position is that the sorcerers earn or acquire powers from gods, demons, faeries, or comparable beings.
Such beings may not always be immune to the ravages of time and space, as we see in Neil Gaiman's AMERICAN GODS. Nevertheless, the dominant trend in mythic fantasy is one of "essence precedes existence"-- in other words, that a being like Aslan exists independently of the mundane realities he inhabits.
In Ursula LeGuin's Earthsea novels, LeGuin's protagonist repeatedly stresses that the nature of magic is essentially one of "uncreating," or at least reordering, the nature of the created universe. This takes the exact opposite philosophical position from that of science fiction, which is more along the line of "existence precedes essence."
More in Part 2.