Let’s just get the obvious out of the way and start with HP Lovecraft, shall we?
The oldest and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown.
As a side note, I’ve always found this quote to be richly ironic coming from Lovecraft, as I’ve never found his stuff terribly frightening with one or two possible exceptions (“The Whisperer in the Darkness” and “The Haunter of the Dark”). Usually his stories consist of a weirdo, a monster, and the monster coming to eat/claim/drive mad said weirdo. Once you’ve read one or two of them, you’ve got the formula down (with rare and important exceptions–“The Call of Cthulhu”, “The Shadow Out of Time”, and others, but those stories were always more ‘cool’ than ‘scary’, anyway). The ‘unknown’ and the fear thereof becomes significantly undermined if you already know, in loose detail, what’s going to happen.
At the heart of it, though, Lovecraft is spot-on. What is really, truly frightening is not knowing what you’re up against or how to combat it. If you doubt it, ask yourself this: if you saw an elephant walking down the street, would you be scared? Now, would you be more or less scared than if you saw an elephant walking down the street and had no idea what an elephant was at all? The second, clearly, and Lovecraft understood this. It’s just that his ability to plot didn’t quite keep up with his understanding of what makes something frightening.
In the end, if we’re trafficking in horror quotations, I prefer one by Stephen King:
The thing under my bed waiting to grab my ankle isn’t real. I know that, and I also know that if I’m careful to keep my foot under the covers, it will never be able to grab my ankle.
~from Night Shift
So, here’s the challenge in horror: to get your readers to believe, even for a moment, that there’s something there to grab them by the ankle. That’s more than simply the unknown. That’s the unknown that knows about you. That’s the unknown and the immediate. Lovecraft’s characters, who go wandering off over hill and over dale to seek out their madness, they’re asking for it. By contrast, that VHS tape in The Ring is right there, on your living room table. You just need to pop it in and aren’t you curious about it, after all? I can not know about elephants, but I won’t be scared of one until it’s stomping through my neighborhood. I need to believe that it’s possible. I need to draw the shades to keep the man-eating giant from looking inside.
I am not, by self-identification, a horror writer. I think part of it is because I’ve never had a horror book scare me, so I don’t quite get it. I’ve been told that things I’ve written and done have been creepy or scary, but I confess to not really understanding what they mean all the time. That said, I like horror. It’s fun to scare people. It is a rare and unique challenge.
Very soon I’m going to be starting up a gothic horror RPG (Ravenloft is the setting, for you nerds out there, and I’m using the FATE system), and I’ve been wracking my brain on how, when, and why to scare my players. One of the basic tricks is, of course, keeping them in the dark. You need to keep the enemy unknown to keep it scary; as soon as it makes its first on-screen appearance, it loses it’s magic. In RPGs, where players are so often obsessed with the minutiae of statistics, stunts, and dice, this is especially important. I can never describe something as a ‘vampire’ and have it work as a terrifying foe. I need to keep it’s identity in the dark for as long as possible, giving the players the sense that something is going to grab their ankle without actually making the swipe. It’s at that moment–at the moment when the scaly, taloned hand grasps the ankle, that ‘horror’ evaporates. We are then, at that precise moment, in an action scene.