In RPGs, “the fiction” is a convenient fiction
Let’s imagine a chess game. Two players who both know the rules sit on either side of a board with the appropriate pieces on it. To play, they’ll use their knowledge of how the pieces move, their mutual knowledge of the rules and victory conditions, the current position of each of the pieces on the board, and a mutually remembered bit of information about whose turn it is to make the next move. Obviously there are a few things that could mess this game up. A freak windstorm, for example, could blow all the pieces off the board. Or maybe a loud noise will distract the players for a moment and by the time they’re ready to return to the game their memory of whose turn it is won’t match because one of them (which one!?) got confused during the interruption. Or maybe one of them will do something that uses one of the more exotic rules, like en passant, and they’ll discover that their mutual understanding of the rules of chess isn’t as mutual as they initially thought.
Now let’s imagine that one of these chess players goes on an expedition to Antarctica but still wants to play chess with his cold-averse friend. They still can! What they decide to do is set up two different chess boards, one in Antarctica and one back home, and communicate their moves back and forth through whatever form of long-distance communication they can. When Antarctica-guy physically picks up a pawn on his chessboard and moves it to a different space he just tells his friend which pawn he moved where. The at-home friend picks up the corresponding pawn on his chessboard and moves it to the corresponding place to represent his friend’s move. All the rest of the stuff is the same: the important thing about chess isn’t that there’s a single physical board between the players, it’s that there’s an agreed-upon representation of the current game-state between the players. Having a single physical board certainly makes that easier and more convenient, but the important thing about the game isn’t how it’s physically implemented, it’s how it looks to the players. Each of the players can look at “the” chessboard and make their moves based on the current game-state. It doesn’t matter if “the” chessboard is a convenient fiction for two different physical chessboards that are being kept in synch by an extra process that isn’t normally necessary.
But what if these friends realize that they don’t really like chess that much and want to play something a little more action-oriented? They decide to switch to a first-person-shooter video game played over the net. Conceptually this isn’t too different from the long-distance chess game, but there are a few details that contribute some nuance. One important difference between chess and an FPS is that the turn-based nature of chess provides an easy interface-point for long-latency communications. If it takes much longer for one player’s move to get communicated it just looks to the other player like a really long turn. Since FPSs need to maintain a smooth, continuous-action flow of play they need to have the effect of the moves represented immediately. When the Antarctic player presses his “shoot” button he’d better see his character start shooting right now! The two computers are both running instances of the game, but the other guy’s doesn’t realize the first started shooting until a message dispatched over the network gets to his computer. But maybe at the same time that the Antarctica guy decided to shoot his gun, his target pressed his “run” button and started moving. In Antarctica, the player thinks he’s shooting (right now!) at a stationary target, but at his friend’s house he thinks he’s moving (right now!) and not being shot at. From the Antarctica perspective the shot should hit (assuming the aim is good) and the target should be wounded. From the other perspective he shouldn’t be wounded at all: nobody was shooting, and even if they were his character wasn’t at the place that the bullets would hit! The two simulations aren’t perfectly consistent. But they don’t have to be! As long as they’re close enough, the players won’t notice. As a human player, the warm guy doesn’t know with perfect certainty where the Antarctica shot was aimed, so if the game has an under-the-hood mechanism that gives “hit detection” precedence to the shooter’s POV then the Antarctica computer can tell the other one not only that a shot was fired but that it hit. The at-home computer can play its “gunshot” sound effect, display the “shooting” animation for the other character, reduces the hit points of the target, and most of the time it will seem perfectly normal to the at-home player that the other character shot and hit him at his current location. The important thing to notice is that there doesn’t need to be a single authoritative game-state in a single place in order for both players to feel like they’re playing the same game with the same state. As long as it looks close enough they won’t realize that their two computers are not exactly on the same page at every instant.
As players they maintain the convenient fiction that they are in the same world because the “game” involves making decisions as if you were, just like it makes more sense to interpret what they see on their screens as a window into a 3D world rather than a bunch of pixels on a flat display. Just like it’s not useful when playing long-distance chess for them to dwell on the fact that they don’t have a single physical board between them, it’s not useful for them to dwell on the potential artifacts of network gaming (unless the distortions become so extreme that they overwhelm the suspension of disbelief and they have to give up because there’s “too much lag” over their network). By buying into the illusion of consistency between the somewhat-independent computers they can play this type of game together.
Now let’s imagine that the adventurous friend returns from Antarctica and the two of them get together to play another kind of game they enjoy, a tabletop RPG. Here they also need to maintain a sufficiently-synchronized game-state in order to play. To do so, they buy into the convenient illusion that there’s a single “fiction” or “Shared Imagined Space” between them. They probably have some concrete common physical touchstones like dice or character sheets as part of the game, but a big part of play involves their brains independently keeping track of the current game-state of imaginary people doing imaginary things, and they send messages back and forth to keep each other more-or-less in-synch (using high-tech “talking” technology). Since their brains aren’t as simple as chessboards they can’t rely on being perfectly in-synch at all times, so their game needs to be constructed in a way that encourages and eases synchronization on important points. For example, if their game has a mechanic which gives a “high ground” advantage then the players will be primed to pay special attention to character altitudes relative to each other in “the” imaginary world. Maybe their mental picture of the characters won’t agree on points like whether or not they have mustaches, but they are likely to agree on who is higher than who if they both believe that is important to the game.
Being sufficiently synchronized to game is the foundation for a functioning RPG (and the astute reader will notice how weaselly a word “sufficiently” is). Many RPG techniques and design elements serve to maintain that synchronization. For example, the “fictional trigger” in an Apocalypse World move can serve like the snap-to-grid functionality of a computer painting program to snap the “fuzzy” mental images of the different players around easily-communicated concrete templates. If my character seems close to “Going Aggro” on somebody I am pulled toward embodying that in my roleplaying because I know that the other players are watching for whether characters are Going Aggro and will understand what I’m thinking better and be more easily synchronized to what I’m imagining when they can use that concrete and mutually-understood pattern as a touchstone for how the scene should be playing out in their imaginations. Agreeing with the other players that the “Go Aggro” move should be invoked and starting the corresponding mechanical procedure gives us an explicit way to acknowledge synch-points without drawing unpleasant attention to our efforts to keep synchronized.