Somewhat contra [MENTION=29398]Lanefan[/MENTION], it often doesn't matter at all if the players think different things about the fiction.
Last Sunday I GMed a session of Prince Valiant. One of the PCs is a bard/entertainer who wears "colourful clothes". What colour(s) are they? We've never specified. If I think about it I guess I think red, orange, yellow, maybe blue also. What does the player of that character have in mind? Or any of the other players?
Another PC has a jewelled sword that grants a bonus in certain social situations. What sorts of jewels? Colour? Size? Monetary value? Again, it's never come up. What colour are the horses? Ditto.
When the PCs boarded a ship to France, how long was it? How broad of beam? When it foundered on a rock shelf, and I described the water between the ship and the beach as "shallow", how shallow? As per the scenario I was using, I called for Difficulty 3 Brawn tests to get to shore unharmed. The rules describe that as a Normal difficulty, sitting between Easy and Difficult, but in this particular context it was fairly hard - Brawn 4 is above average (perhaps comparable to a 13 STR and/or CON in D&D), and the chance of getting 3+ successes on 4 coin tosses is 5/16, so we coud compare Difficulty 3 to DC 16.
Was that difficulty due primarily to the depth of the water, the wildness of the storm, the dark of the night, the slippery and harsh nature of the rocks, or - more likely - all of them in combination? The rules don't require us to specify, and different players may have been envisaging the ficiton differently in the details though no doubt the broad brushstrokes were pretty similar (eg water mostly less than head height, but big waves breaking, and hence a real danger of being dashed on the rocks).
I'm reminded of this discussion of GMing techniques from the Maelstrom Storytelling rulebook, under the heading "Literal vs Conceptual"; I first learned about this RPG from Ron Edwards's essays before picking up a copy second-hand, and while I've never played it it's certainly influenced my approach to GMing and narration:
A good way to run the Hubris Engine is to use "scene ideas" to convey the scene, instead of literalisms. . . . focus on the intent behind the scene and not on how big or how far things might be. If the difficulty of the task at hand (such as jumping across a chasm in a cave) is explained in terms of difficulty, it doesn't matter how far across the actual chasm spans. In a movie, for instance, the camera zooms or pans to emphasize the danger or emotional reaction to the scene, and in so doing it manipulates the real distance of a chasm to suit the mood or "feel" of the moment. It is then no longer about how far across the character has to jump, but how hard the feat is for the character. . . . If the players enjoy the challenge of figuring out how high and far someone can jump, they should be allowed the pleasure of doing so - as long as it doesn't interfere with the narrative flow and enjoyment of the game.
The scene should be presented therefore in terms relative to the character's abilities . . . Players who want to climb onto your coffee table and jump across your living room to prove that their character could jump over the chasm have probably missed the whole point of the story.
Commenting on this,
Ron Edwards says that "I can think of no better text to explain the vast difference between playing the games
RuneQuest and
HeroQuest." Which is to say, there are some systems which make enginnering or cartographical precision central to resolution, but there are others that don't. Certainly establishing a call to action doesn't depend upon any general uniformity or specificity of imagination. I think it does require estagblishing the situation by reference to the resolution mechanics - the plaeyrs can't answer the call if they don't know, in general terms, how their characters might fare.
Which goes back to [MENTION=5142]Aldarc[/MENTION]'s point some way upthread: RPGs have ways of establishing the emotinal "heft" of situations that are quite different from the sort of evocative composition or performances that other creative endeavours rely upon In my 4e game, for instance, if the players are committed to confronting Orcus, and I - as I did, following a successful knowledge check by the Sage of Ages - tell them his stats, then the players respond with the apposite awe, fear, etc. I don't need to evoke, by deft narration, a sense of how terrible Orcus is. The stats do that work.
Of course different systems open up and close down different sorts of possibiities in this respect. For instance, in MHRP/Cortex+ Heroic it is the state of the Doom Pool, as much as the stats of any individual antagonist, that conveys the significance of the present situation. And in Dungeon World or Apocalypse World antagonists don't quite have "stats" in the way they do in D&D or Cortex+, and so system conveys heft in different ways, sch as the plauers' perceptions of possible interactions between the moves they want to make with their PCs and the current state of the fiction that might feed into GM moves if those player-side moves fail.
This is also one reason why, in RPGing, system matters.
