One of the things we often have to do when we’re writing (especially fantasy) is make the improbable seem familiar. To do this we’re often asking the reader to suspend their disbelief but there’s really only so far we can push the reader. Often I think this is a gut-level decision on the part of the author but there’s another way I’ve started to think about it that I think can be helpful.
I think that every author, for every story, is given points — I call them credibility points. The reader is going to suspend their disbelief — it’s part of the contract we make with them because they know this is fiction and they know some things they’re just going to have to take at face value. But there’s a limit to that and this is where the points come in. The more that you ask the reader to suspend their disbelief, the more points you’re spending and you only have so many.
Here’s how it works: Let’s say you start off with 100 credibility points. My first series is about a world set several generations after the zombie apocalypse. I’m asking my readers to believe that yes, zombies exist — that’s a pretty big suspension of disbelief so I’m probably spending like 50 points on it — half of my credibility points. This means I have to be careful how I spend the rest of my points — everything else has to basically be familiar or realistic enough that the reader won’t question me much further.
Then, in my first book, I spend a few more points on the fact that it’s been about 150 years and the chain link fences surrounding the village are still standing and still able to hold back zombies. That’s probably another decent sized purchase — lets say 40 points. But then I buy back a few of those points by explaining how the fences are still around — I show the reader that the people in the village are always monitoring and mending the fences, I make my zombies “hibernate” so that there’s not always a big horde pressing against it, etc. So then maybe I’m only spending 25 points on the fence because I’ve made it a little more believable.
This leaves me 25 credibility points for the rest of my book — I can’t really keep asking the reader to suspend huge amounts of disbelief. This is where your research can come in really handy — what David was talking about recently. The more accuracy you imbue your stories with, the less you’re spending these points (and often, the more willing a reader is to trust what you’re telling them because you’ve earned that trust).
The key, to me, is spending your points wisely and often this isn’t easy. I wrote a scene in the beginning of my second book where a group of teens cross into a potentially zombie infested area and, guess what, zombies attack. Initially I had all the teens drop their weapons in a pile when they got there because they were being complacent. But this strains the credibility — and costs points — they live in too dangerous a world to be that stupid. Instead I had them keep their weapons and just stink at defending themselves (and I explained they stunk because they’d never had to do it in real life before) — that took less suspension of disbelief and cost fewer points.
This isn’t a scientific theory by any means, it’s just one of the ways I’ll look at my stories to see if I’m asking the reader too much — stretching credibility too thin. The goal is to spend as few points as possible — to weave these incredible things into the story and explain/motivate them so thoroughly that the reader doesn’t even realize they’re suspending their disbelief. That’s the goal in the end — having the reader fall fully into your world and not leave it because they don’t believe it.