Short version for the people who are saturated in AD&D lore: The Machine of Lum The Mad makes a good metaphor for running a game.
For everyone else? Well, let’s pull up a chair and start with the titular contraption.
So among the many things that littered the Dungeon Master’s Guide for Advanced Dungeons & Dragons way way back in the day was an artifact called the Machine of Lum the Mad. Now, most artifacts were designed to really see what the players could do to break a campaign. Ridiculous powers, weird drawbacks — the sort of things that would trigger highly experimental play. But the Machine was perversely special. It was described as having 60 levers, 40 dials and 20 switches, about half of which still worked. It could do just about anything — if you had the right combination of levers, dials and switches. DMs were encouraged to map this out.
Let’s pause and marvel at the insanity of this. So say there are 30 working levers, 20 working dials and 10 working switches. If you try to figure out how many combinations of those switches alone are possible (like “off on on off off on off off on on”) I think you get somewhere around 512. Now add dials — and by add I guess I mean multiply. All those 512 combos, multiplied by the on-off combos of the set of dials. Now switches. In other words, the only sane approach to adjudicating the Machine is to figure out a few specific combinations, those you intend to reveal, and ad-lib the rest.
Sort of like adjudicating a world, really.
Running a roleplaying game is a fascinating exercise. There’s not much like it. Writing books or plays or building train sets are in some ways less limiting, because you don’t have to worry about the word “playable,” but at the same time they aren’t like the Machine. Unless you are an extreme believer in the idea that your characters do unexpected things, when you write a novel you can generally stick to the characters you’d planned. You might have to devise a character when you figure out that you really do need to have a police officer show up and ask questions. But when running a game, players may stop and talk to anyone, walk into any building. They might ask what the bar’s specialty drinks are, if the bartender’s hot, and if there are any taxidermied animals hanging around that they can mess with. They might ask what the latest opera in town is, or who their Senator’s mistress might be and where they could find her.
And you have no idea what questions they might ask. If the world is an infinite combination of levers, dials and switches, then the players are the ones finding the combinations and running them through the Machine. It’s like writing a novel and then having your readers ask you about things you’d never considered — the life of the man who cut the heroine off in traffic, the menu at the coffee shop mentioned in passing, what the local schools are like.
It does something to your brain, I think. Those of us who operate the Machine are very like creators in other media — we are compelled to accumulate ideas, keep notebooks, rehearse lines. Because that’s the joy of playing a tabletop RPG — that you can try any combination of levers, dials and switches, and someone will tell you what the Machine does. And although you can let the players discover combinations, encouraging them to try prepared content, you can never be sure they won’t just pull something completely random. And that’s when your familiarity and confidence with the world will allow you to determine what the Machine spits out. Or an idea from your notebook, swimming back into your brain. Or you pull out something completely random, staring at a nearby household object like Verbal Kint with a fistful of dice and ad-libbing at the speed of light.
Or you can stammer “Nothing happens,” and the players will nod sagely and say “ah, that combination must be burned out.” It’s always an option. But I think many of us, in our hearts, feel terrible if it comes to that. After all, we wouldn’t have sunk so much effort and creative energy into a Machine of that complexity if we didn’t want to see it in action.
Of course, it’s arguable that building a Machine of this complexity and then passing out tickets to come and play with it means that we’re all mad anyhow.