Nonetheless, three points emerged that loosely correspond to my own working definition of "science fiction." These are individually necessary but insufficient criteria, jointly sufficient to classify something as a work of science fiction.
First, a futural orientation. Science fiction for me is about an imagined future or an imagined alternate present, rather than about an imagined past. This is mainly a tonal issue, I think: fantasy, the principal "other" against which this criterion is directed, tends to evoke a sense of a world long gone, while science fiction looks towards something that is to come, or could have come had something been slightly different.
Second, a thematic of technological difference. There has to be some kind of change in technology, and this change -- and its implications, usually including social implications -- has to constitute an important thread that the novel/film explores. It's not enough for there to be different technology, though; something like Star Wars certainly has different technology (lightsabers, hyperdrive, etc.) but these things don't seem to affect the conditions of possibility for action in any significant way. One could tell Star Wars without the spaceships and laser guns and the like and not lose too much of the story (although you'd lose the special effects); the same is not true with Star Trek, as the technology both enables the whole cosmos (no warp drive, no Enterprise) and forms a significant issue that is addressed in numerous ways throughout the megatext of films and TV episodes and novels -- most notably in the continual return to the Prime Directive as a way of handling relationships between the Federation and less technologically advanced civilizations.
Contrast also the Star Wars use of faster-than-light travel with what Stephen R. Donaldson does with the notion in his Gap series; where Donaldson gets into sociological and other implications of the technology, Lucas treats it like he treated the internal combustion engine in American Graffiti: people jump in their cars/spaceships and turn the key, and off they go (broken hyperdrive issue throughout ESB aside, since Han Solo tinkering with the engine is kind of like a teenager tinkering with his car: neither one is about the technology per se).
It's also important for me that the difference be technological, and not magical. The difference is that technology inhabits a "disenchanted" world -- one in which there are mundane rules that reliably produce results, and there is nothing that can't be known in principle (although there might be things that are empirically not known or incompletely understood -- a common theme of much science fiction, actually). Weber points out that living in a disenchanted world means that even if you don't know how the train works, you have a sense that you could find out -- and that the explanation would not involve supernatural forces or mystical/divine intervention. Now, one can have disenchanted worlds that aren't science fiction, even disenchanted worlds that involve "magic." Harry Potter comes to mind, since "magic" there is just another subject in which people specialize and are educated (I do not think that the notion of "being born with the gift" makes HP less disenchanted, since the same might be said of the ability to program a computer or play baseball; talents and inclinations don't mark a system as "enchanted" in the way that an absence of calculable rules and procedures does).
Third, a plausible connection to the present. This is the trickiest criterion, I think, since the definition of "plausible" is a matter of some dispute. It might mean that the technology depicted in the film/novel can't be inconsistent with what we presently know (the Heinlein criterion from his definition that I posted earlier -- although Heinlein pushes that a lot in his later works with his creation of the Burroughs Improbability Bus that permits passage between alternate timelines, which is a pretty extreme interpretation of the many-worlds hypothesis of quantum mechanics…), or it might mean that we need some kind of developmental path from our science to that of the novel/film (often mediated by that conventional sci-fi narrative device, the Man From The Past Who Finds Himself In The Future, glossed as John Chriton in Farscape [Man From Earth Who Falls Into A Wormhole And Ends Up On The Other Side Of The Galaxy] or as the future character with an oddly convenient interest in Old Earth, a.k.a. our present). The basic point is that there has to be some way that the imagined future looks like it might have developed from ours, or that it is connected to ours in such a way as to make it a legitimate modification of some of our world's scientific rules.
This is a fuzzy criterion. Heck, all three of these are fuzzy. The point of a genre-bounding discussion like this, I think, is not to answer the question as much as it is to elucidate points of debate and contention that can be explored in connection with specific works later on; the definition in question is ideal-typical in the Weberian sense, and deviations from it, or ambiguous cases that push its boundaries, are where it demonstrates its interpretive utility.
As an exercise, consider whether the following works are science fiction or not, and why:
- The Lord of the Rings
- The Chronicles of Narnia
- Stephen R. Donaldson's Chronicles of Thomas Covenant
- Iron Council, by China Mieville (see the discussion over at Crooked Timber about this precise issue, among other things)
- Star Wars, with and without the expanded universe novels
- Kurt Vonnegut's Cat's Cradle
[Posted with ecto]