A rough draft of some thoughts about how much players ought to know about the game world before playing-- and spinning out of that the implications of player knowledge at the table. This is a start of some thinking about this, so take it with a grain of salt.
Changeling: Dead Giveaways
Changeling the Lost remains one of the rpgs I love and hate at the same time. To explain why I have to give a little background on the setting. In Changeling, the PCs take on the role of people who have been kidnapped from our world. Through trickery, bad choices or random happenstance, they have been pulled over by The Keepers into an otherworldly realm. The process strips away much of the victims soul, caught on the thorns of the Hedge they're drawn through. The Keepers represent dark and awful versions of the fairy stories and the fantastic. During their “durance” these kidnap victims become transformed by their service. Then, somehow, they manage to escape from their service only to return to the real world, a changed person. Time has passed, in many cases they've been replaced by a simulacra or Fetch. Now the characters must hide their changed appearance beneath a mask of illusion. The barely remember what they suffered in the Hedge, and when they do, then run the risk of a breakdown. They must run the thin edge between trying to adapt to human society and embracing their changed nature-- all the time living in fear that their Keeper may hunt them down and steal them back.
I think that's fairly brilliant and provides for a group of characters who begin literally and figuratively lost. Their quest to learn about that world makes for a fascinating campaign: discovering how Changelings in the real world work, finding out about the existence of Fetches, meeting other kiths and seemings, realizing the dangers inherent in the Changeling society, learning about the Courts, discovering what things pose a danger to their sense of self. I love the idea of exploring all of these questions-- except that the main book tells you all of that stuff. It spells it all out, gives all of the details, provides mechanics and seems to assume players will be playing characters who have been around for a while in this society-- a strange choice.
The materials here present the players with a set of expectations. They know about the Fetches from the start and the game provides suggestions on killing or dealing with one's fetch. It talks about the possible mechanical benefits a character can gain from doing that. Right away we've moved from this being an interesting exploratory device to a bag of points which have to be cut open like a magic pinata. The main book also provides a set of expectations about other mechanical options-- Changelings can attach themselves to a business to raise its revenue and be paid for that. I had a player say they wanted to do that-- when I asked them what that would look like, how it would play out they became irritated-- “the book said I could.” They never came back with a description of how that would work and so it fell to the wayside. Changeling also presents some thematic assumptions-- not least of which is that all Fetches are evil and will screw over the PCs. But everything seems to have that underlying poisoned nature to it. Everything interesting and magical, from the Courts to potential allies to the bargains of everyday life get written in the darkest, most paranoid way. Now obviously I'm not planning on running that way, but part of the problem is that “player knowledge” of the book that presents some expectations.
Now there's a bind here I don't have a definite answer for. I do like the mechanics and options the game system does provide, and I do want players to have access to the range of them. One approach to solve that might be to play with a minimal character set up at the beginning-- more of a sketch than a full character. Then after a couple of sessions of play, let the players actually make up their characters. This has the added benefit of the group play setting up some roles and giving people an idea about how they can find their place. I do a minor variant on this process in that after the fourth or fifth session of a point-based campaign I allow players to retool or re-spend their points.
I also don't necessarily want them having to constantly ask about basic details of the setting at the table. I want players to have an understanding of the basic shape and structure of the setting, but not the details. But I do think that some games operate better with minimal player knowledge at the start-- usually games involving some kind of transformation or entry into an liminal world. For example, I think the structure and background of the Vampire universe is more interesting when encountering it without having read any of the stuff. That's how I first hit it-- with that confusion a person in that situation would have and the frisson of discovery as we played along. People told me lies about how things were and I didn't know any better. Call of Cthulhu, Mage, Delta Green, All Flesh Must Be Eaten and Grimm all strike me as games which could benefit from this approach. The best Werewolf game I had was one where I'd forgotten most of what I knew about the Werewolves. I had some player knowledge, but it had been so long I had everything mixed up in my head.
Define Your Terms
In discussing Player Knowledge, I'm using the term in a slightly broader sense than we usually do in rpg discussions, so I'm obligated to provide a reasonable definition of it (per Brad Murray's excellent comments). Usually Player Knowledge refers to the act of ignoring certain things you've heard at the table because your character wasn't present in a particular scene. But I think there are a few broader levels to that.
Mechanical Knowledge means the rules themselves. We can assume equal access to this information among the players. That may not always be the case-- some players may have bought the supplements and others haven't, but functionally there's no reason why everyone shouldn't know the rules.
Story Knowledge means awareness of events which have occurred in the game with the players present. That knowledge may be unequal-- not every scene has every characters. Some players miss sessions. The GM may handle some things away from the table or via email. Some tables may be more or less strict about how a player can pass information. In our group for example, we use the shorthand phrase “Blah.” If a player wants to tell someone's character about a something which happened where that character wasn't present, but their character was, they Blah them. At times the GM may intrude to get some clarification about how that information gets spun or may require some elaboration.
Background Knowledge: can from the flavor, description and history text within the rulebooks (or from source materials). Often this can be kept away from the players. But, as I've suggested, some games build background knowledge assumptions into the rules themselves. Background knowledge also refers to the campaign world itself from other campaigns or outside of table play. The situation becomes more complicated as a campaign rolls on. Unless the story operates with a fairly clear and direct plot, a player entering later into a game may feel lost. Now, how much that will actually impact their effectiveness will depend on how the campaign uses background knowledge vs. event knowledge vs. mechanical knowledge. If the world has existed for several campaigns, the GM needs to be careful about how much they tip the hat to previous events and characters or risk alienating new players.
Games Requiring Player Information
Some games take a deep approach to the world. The question here isn't one of volume of information-- but rather how that game background and information gets played out at the table. The depth and structure of the system means Ars Magica is a high background game. The GM will likely assume players have a knowledge of what magic looks like (beyond the mechanical aspects), what the covenants look like and what wizards do. Depending on the GM, the players may also be thrown in situations which assume some knowledge of medieval culture and society. I think that kind of assumption makes people react negatively to the idea of a historical game-- the sense that they're going to be tested on the material. But Ars Magica's a fairly unique game and one which has built up a reputation as one for the more historically minded (along with others like Chivalry & Sorcery and Pendragon). Our group played and had some sense of that, but more focused on the fantastic elements of the life of the mages themselves.
Another kind of game which assumes some background knowledge on the part of the player is something like Legend of the Five Rings. There's a great deal of background-- much of it important to playing, depending on the campaign. At the very least the campaign assumes a familiarity with the codes and ethos of the setting. Unlike the historiocity of Ars Magica, L5R presents itself as inspired by history but with its own set of important in play, non-mechanics rules. Players who cross those lines suffer consequences. Mutant City Blues also requires players have some fairly technical knowledge about the setting-- however in this case it is the Quade Diagram, detailing the relation between various super-powers. When investigating a paranormal crime, players will deduce other likely powers (or flaws) possessed by the criminals. In all of these games, players will more often make contact with plots or interactions which presume a higher level of information on their part.
In some cases we have games that don't require specific knowledge of the setting, only a general knowledge of conventions. Most general fantasy campaigns fall into this category. Even with the extensive detail and world-building of Eberron and Forgotten Realms, I'd be willing to bet most players don't operate with a great deal of knowledge about the setting. The impact of this is that players aren't called upon to have a specific knowledge of the setting-- beyond the general outlines. They won't be penalized for missteps-- the GM will fill in those gaps. Something like James Bond 007 (and other espionage games) follow the same kind of format-- players know and understand the conventions, the get the basic mission details and get rolling.
Dogs, Again With the Dogs
Dogs in the Vineyard takes another approach to player knowledge and control. The premise has characters acting as agents of the Faith in an old west-esque setting. They arrive in town, suss out problems and trying to solve them according to the tenants of their faith. The game does a nice brisk job of defining the character's backgrounds- working those into their skills. There's also a personal trial that helps shape their focus. But the general background of the setting is sketchy-- almost like a second-hand story being told about a place. There's no map, no thick details for the lands the players move through. That's deliberate. The book provides a general sense of the laws, rules and tone of the faith. But it steers away from the specific scripture. Instead players play out their judgments based more on improvised approaches to that doctrine.
The first reaction one might have in hearing about this is an assumption that such doctrine would be absolute, fundamentalist and violent in nature. But the game suggests a goal for the players: the preservation of the community as a whole. The players have to find a way to do that in the face of escalating problems. And they may disagree on a solution which provides another source of interesting tension. I think this sketchy approach is an interesting one: it outlines things lightly not to provide mystery but instead room for the players to develop and create the setting. I imagine different DitV campaign would look and feel vastly different. The GM's actually told not to plan and create-- their job consists solely of setting up a problem for the players to deal with, and adding complications as they go along. There's no world-building in the conventional sense.
As a middle ground, we might consider something like the toolkit which is All-Flesh Must Be Eaten. In a strange way, this serves a generic system-- but for doing Zombie games. Obviously you can detatch Unisystem from this, but there's no core Unisystem book. Of course there are completely open games-- ones in which the players build the universe as it goes along. There might be a few ground rules but you have a collaborative discovery and building. I've never played any of those (but I'd like to) so I can't really comment on Open Games
Mounting Spoilers on Samurai
Legend of the Five Rings has this massive problem with the mixing of GM and Player specific knowledge-- providing spoiler level info everywhere. In the early Way of the Clans series we get important player-oriented information and mechanics mixed in with revelation of secrets from the background. Even the later Secrets of the Clans series does this-- there's clearly player centered information in the books but also setting breaking ideas and information if the GM decides they want to use that as is. Walking the Way, one of my favorite sourcebooks for the series, offends egregiously on this count. Each spells receives a thick description and then on the page following, a short adventure or scenario. So if a player wants to read the spell material, the potential adventures a GM might use is right across. It seems like this could have been easily solved with a player and then a GM section breaking the two apart. That's never a great solution-- as putting things together invites the reading. But it is better than what we ended up with.
*Player shouldn't read the GM material. True, but the temptation is there. And in some books like L5R, the players can be reading along and suddenly hit things they shouldn't have-- without any real warning.
*Don't worry about it, players can play as if they didn't know. That's true, but if your goal is to make things evocative and interesting, then even the best play-acting in this case is stilted. As I mentioned with the Changeling material, I think it is hard to capture that wonder once the bottle's been opened.
*The GM can change things. Yes, obviously. But if the GM's has to change things, that sort of contradicts the point of actually buying the material. You might change a few things, with the idea that this approach will keep the players on their toes, but that creates a distracting guessing game. Players can get confused about what's changed, what's accepted and how to play. This can lead to them simply disconnecting from the setting.
*The Players shouldn't buy these things. There's a contradiction in that I'm actually glad that most of my players don't buy game materials. On the one hand, I want the game to succeed and sell books but on the other hand I'd like to be able to pull back the curtain on some things myself. There's a strange business contradiction in these game lines. If something's built for a GM, then you've only targeted a small portion of the audience. If it targets GM and player, then you run the risk of putting out info which can undercut the story. And, of course, player-centered information tends to be more rules and character creation options. There's the risk of rules and power creep if the companies continue to move down this path.
My Favorite Approach
A few supplements handles these problems with other approaches. TSR's Gazetteer series for the Known World provides one option. Most (but not all) of these folio supplements included a separate Players Book for the particular nation or culture covered. This provided a general background, map, cultural considerations and usually some mechanical notes for players coming from there. Since these books came saddle-stapled separately from the main book, they could easily be distributed to the players. That's not a bad approach-- and I've seen some PDF-only games which have done the same thing, either as a freebie or as one of several pdfs bundled together. City of Lies had a similar approach, but with a different frame. You have a player knowledge book, but one assembled from various in-game sources. It provided color within the context of the game and also suggested many mysteries. Half-the charm of this was letting the players tease out the secrets. Another supplement I've mentioned is the Kaiin Player's Guide. It takes an open-information approach with a description and discussion of the city-- there is no GM's guide. Everything is presented out in the open with the idea that players will grab on to the loosely described threads and bits to make them their own.