The first point is, what exactly is the difficulty in defining Science Fiction? Well if you read the last post you'll see that in order for a determined work to be considered Science Fiction, it has to deal with certain tropes, and comply with some simple rules; however it doesn't have to fulfill all of the tropes, and the rules are so broad that they can be applied to most mainstream, or realist fiction.
So let me retake each of the tropes, one by one, and look at them to see if they can be applied to a genre other than science fiction:
- The story takes place in the future (from the authors time).
This trope can clearly apply to mainstream fiction (and therefore to many other genres), and does not necessarily mean that the story is SF. One book that comes to mind is "The Election" by Darryl Greer, or "Patriots: Surviving the Coming Collapse" by James Wesley Rawles, to name just two novels from two different genres, the first one a Political Drama, and the later is a Survivalist Novel.
- The story revolves around a given "scientific" discovery or theory.
This one is a little harder to delineate, and see if it fits with other non SF genres. Most people would argue that this is probably one of the defining characteristics of Science Fiction as a genre, but once more it can be applied to some genres (though not as many as the previous trope), such as medical thrillers like Cure by Robin Cook, which revolves around the murder of kidnapped bio-medial researcher Satoshi Machita, who was close to a breakthrough in stem cell research. If this single issue is taken out of context, than this novel would be SF.
- It involves technologies not found in our world.
Now this one I believe is closer to the mark of being SF exclusive, but once more there comes into play a different, and closely related genre, Fantasy. Some might argue that this is not the case, that Fantasy does not use any sort of technology, but this is not the case, as you can find several instances in which there is a sort of technology, which does not posses a logical or rational explanation as to its workings, but it is there. One simple example is the Ter'angreal found in Robert Jordan's Wheel of Time Series, like the much mentioned but never seen shocklances.
- Extraterrestrial beings are involved.
This is probably the only one that is definitely a staple of SF. Even in genres such as Fantasy and paranormal dramas where it is possible to find creatures other than humans, those others are not of an extraterrestrial nature (understood as coming from another planet within our universe).
- The story takes place on other planets (one or more).
Once again Fantasy comes to challenge the domain of SF on this trope, for one can say without a doubt that The Lord of the Rings takes place in another planet (maybe even an entirely different dimension or universe), but it is not a world we feel to be in our same universe; in fact the question of where exactly middle earth is is irrelevant to the story.
- Technological innovation plays a central role in the story.
In today's world technological innovation is a part of the norm, for example in Stieg Larsson's Millenium trilogy, technology plays a key role, and in fact without technological innovation such as Lisbeth's Asphyxia software the plot would very soon come to dead ends without a way out.
- Society changes up to a point where we can no longer recognize it as our own.
This is probably one of the broadest tropes employed by SF, as it can be found in so many and varied genres that it has been postulated that it should not be included on this list at all. Take once more Greer's novel mentioned before, or Kafka's The Castle, in which society has been so warped that we cannot really relate to it, and so many other examples.
- The setting for the story (backdrop)is not something found in our everyday life.
This can be applied to pretty much any sort of fiction, what differs in SF is in reality the degree to which we are, as Darko Suvin has said, estranged from our every day world.
As can be seen here each of these elements on its own can be applied to many different forms of fiction, therefore coming to a delimitation of the SF genre is not such a simple task, and most of the definitions which have been postulated so far by Academia has been contested on the grounds of not being inclusive enough, or of the opposite, of including too much. So maybe the tropes by themselves are not enough to fully define Science Fiction as a Genre, and other elements are needed, but that will be the topic of a next post, for this one seems long enough already.