When you and I are at dinner and I say "This chicken is delicious," in order for you to understand me, a lot has to be going on.
So there's this object in the real world, a roast chicken, sitting in front of us on the table.
And each of us have got a mental model of the real world. In each of our mental models, we have a representation of a roast chicken.
When I say "This chicken", that utterance references
the roast chicken in the real world, but can only do so through
the roast chicken in each mental model of the real world. Those mental roast-chicken symbols correspond to the physical real chicken; they are caused by
the physical real chicken, enabling successful reference.
Communication is only possible if (A) both of us are confident that each of us has a mental roast-chicken-symbol, and (B) both of us are confident of fact A. How can that be the case? Do we have infinitely nested mental models of each other's mental models of each other's mental models?
No, of course not; the universe has a finite capacity for information. Instead, we use a heuristic: "Any entity that can observe a physical X has a symbol for X in its mental model of the world." Each of us observes the other observing the chicken. Each of us therefore knows that each of us has a chicken-symbol.
We call knowledge of this form, gained through heuristics like "Any entity that [Situation] has [Knowledge]," manifest
. To all dinner guests, it is manifest that a roast chicken is on the table.
We call manifest knowledge in the common ground
Cool! We can talk about dinner. When I utter "This chicken," you know that I'm referring to some salient entity within the chicken-category that exists and is relevant in both of our mental models: the roast-chicken-symbol that caused by observing the physical roast chicken on the table.
So. Mental models don't have to be caused by the real world. Symbols in those models don't have to correspond to anything in the real world.
That's all linguistic pragmatics, so far. Let's talk about games! Let's talk about the Shared Imagined Space.
As we play an RPG or a game like Air Chess, through conversation, and through other performative acts like manipulating minis on a map, we make manifest facts about a hypothetical environment that does not have any correspondence to the real world. We call this common ground relating to a hypothetical environment the Shared Imagined Space.
So. We have the SIS. We construct the SIS by making facts manifest through conversation and performance.
This SIS has no correspondence to the real world.
But that doesn't mean it has no correspondence to anything
In Air Chess, there are Rules. They exist before we even start out conversation. And there's a Game State. The Game State is objective, it doesn't change because we've forgotten something about it. If we can check the game state, we can add the forgotten bits back in to our mental models.
We have a heuristic for how the rules and game state add to our common ground: "Any entity that knows the rules of Air Chess includes the mandates of those rules in their mental model of the hypothetical space that represents the game-state."
And, "Any entity that directly observes some portion of the game state includes representations of that portion of the state in their mental model of the hypothetical space."
And, "Any entity hearing an utterance that describes a change to the game state will so alter their representation of the state if and only if the described change constitutes a rules-legal move."
(And lots more, really.)
In infinite-board partially-observable asymmetric-information Air Chess, ie, a Gloracular Klokwerk Blorby RPG or maybe Strategos
, the rules and the game state cause corresponding symbols and symbolic relationships to exist in participants' mental models of the hypothetical space.
Those participants' good-faith utterances about their own mental models of the hypothetical space cause those symbols and symbolic relationships to become manifest and grounded: to be added to the Shared Imagined Space.
In a Blorby Gloracular Klokwerk game, there is a real, actual THING that exists outside of the SIS. The Game State.
We are having a conversation about the Game State. That conversation grounds and modifies the Game State.
As an epiphenomenal byproduct of this conversation, a story is produced.
In a pure No-Myth game, there is no Game State outside of the manifest, grounded Shared Imagined Space
We each have private mental models that are bigger than the SIS. I know what my character's thinking, but I haven't told the rest of the group yet. But those private representations aren't caused by, don't correspond to, don't supervene upon, any objective external construct.
Obviously, this difference isn't categorical. It's a continuum: How extensive is the Game State, what does it cover? Blorb says: the bigger, the better. No Myth says: as small as you can get away with.
In The Pool, the game state is a single number for each player.
In Sandra's D&D, it includes hundreds of pages of module content, hundreds of pages of spells, dozens of roll tables, detailed maps.
If someone else were running the same module as Sandra, in a non-Blorby way, those hundreds of pages of module content might not count as game state. They'd be mere suggestions.