If you’ve been a follower of the site for awhile, you may remember the post “Written in a Corner.” In that post, I mentioned that I would write another post addressing the topic of plausible impossibility, which is an important concept in speculative fiction writing. Of course, if you’ve been a follower of the site for awhile, you probably also have realized that I’m not always very good at following up on these post ideas that I drop in my posts in anything approaching a timely fashion. Don’t worry, I’ll get to it eventually. In this case, it’s only taken me a couple months.
Speculative fiction, in almost all cases, could not happen in our world as we know it. That’s practically one of the requirements of the genre, and that’s saying something in a genre known for having few requirements. It’s one of the things that can turn off people new to the genre, who are thrown by the way young girls occasionally wind up being able to rip the iron right out of their enemies’ blood. Of course, those of us who are assiduous speculative fiction readers are just as let down when the protagonist of some romance novel fails to summon a magic sword when confronted with danger.
Yet even the most avid readers of speculative fiction need the worlds of their stories to make sense, to have some kind of rules, and that’s where plausible impossibility comes in. The things that happen in fantasy and science fiction probably couldn’t happen in our world as we know it – that is, they’re impossible – but they have to make sense in the context of the story’s world. This is why Gandalf couldn’t just magically transport the One Ring into Mount Doom from Rivendell (so yes, plausible impossibility applies even to soft magic systems). In order for a story to make sense, it must be internally consistent.
That’s the essence of plausible impossibility: something impossible in our world, but is internally consistent and plausible within the world of your writing. This is one of the reasons that science fiction-fantasy crossovers are so challenging to write. Science fiction typically demands explanations of the things in it that don’t fit with our current understanding of the universe, and fantasy in many cases defies scientific explanation – it doesn’t defy explanation, just scientific explanation. For instance, the magic system in Harry Potter is plausibly impossible within the context of the world, but imagine if you tried to write a science fiction story involving it. Could you make a giant wand into the power core for a starship? What are the limits? How do things scale? Does the magic transport happen truly instantaneously, or does it obey the light speed barrier? If it doesn’t, then how does it address problems of paradox?
Referencing The Lord of the Rings again, since it’s an excellent example of a soft magic system, we never really get any explanations for how Gandalf’s magic works, or even why he has magic that no one else does (some information on this is expressed in The Silmarillion, which I have read once or twice, but not a lot of detail on how the magic really works). Yet there are still limits on his power – readers are not left wondering why he doesn’t just blast Sauron into a pile of sparkling ash with his gnarled staff – and it fits in the context of the world. When he uses magic, it is plausibly impossible.
Ultimately, plausible impossibility is a matter of being internally consistent. There are unique difficulties to writing soft magic systems and hard magic systems to be plausibly impossible, and different challenges still for science fiction versus fantasy, but plausible impossibility is the key to making genre fiction work. I would go so far as to argue, that even before dealing with characters, settings, and plots, you must address the issue of plausible impossibility.