How Common Is Common knowledge?

einstein thacoOne  issue I always have when I’m on the players’ side of the table is with common world and game knowledge. How much does my character actually know about the monsters or magic in the world he lives in? Does my character know in-depth info about the political structures of the megacorp he is working against, or just that they have them like any large company? Will saying that having basic knowledge of the sort he could obtain in his
home village mean the GM makes him a prison-bitch he is denied gaming opportunities that a different background might have allowed, or will it be something he can shrug off as he advances and grows?

Coming to a mutual understanding of exactly what is common knowledge for your game is not an easy task. Gaming books provide lots of information that is necessary for playing but might not be readily knowable by the characters. What is known to one class or type of character might not be known to another, but many of the dangers they will face together require teamwork and interaction. Each player likely thinks of common game and world knowledge in a different way and is thus operating on a different page than the rest. There are a lot of places for pitfalls to develop when it comes to common knowledge.

Like Einstein Says – It’s All Relative
So how does a group deal with common knowledge in a consistent way? I don’t think it is possible to ever have a single truly definitive answer. Setting, game mechanics, and personal play style are going to be factors of every situation where common game world knowledge comes up. Every situation where game and world knowledge comes up has multiple people’s interactions, and each one of those interactions can  affect the game and the story at the table. Take this example: A publisher gives a creature a very high damage resistance, maybe even regeneration. He places a line in the monster’s description that they have a vulnerability to a certain type of metal. This piece of knowledge is now out there somewhere, but in order to use it the players must know it and their characters, more importantly, must know it. Is this tidbit of knowledge meant to be a treasured golden bullet that the PCs learn after hardship? Is it well known to the cavalries of brave soldiers who protect the frontline from these monstrosities and thus the metal is in high demand? Will the players glean this knowledge from reading over the book? If they do, can and would their characters have it and thus know to modify their weapons with the metal? The context of the knowledge within the world is extremely important, but only really to that one situation it is relative to. To a person in a far off country where that creature is not a threat, the previous metal might be nothing more than a paperweight.

This is one of the primary reasons why common knowledge is so hard to lock down in a game. Too laissez faire of an attitude about common knowledge and many of the challenges that lack of knowledge intensified are cakewalks. If it is assumed that characters know about any magical item the player reads about, then characters seek out such things. Not always a bad thing, but possibly a free pass to acquire that killer app for the game. The reverse, too restrictive, and first party characters are nearly wiped out by level draining undead because they don’t know enough to run away. The joys and perils of the game? Absolutely! But it cannot be denied that the accessibility of the game and world knowledge is a major game changer.

Well Defined Setting Knowledge Is Always Helpful
Sometimes the setting and mechanics present things to help you out when it comes to common game world knowledge. Eberron books are written with a very in-world feel and lots of instances of in-world narrative that suggest what people might know. If you are reading it inside of an Eberron book, then it is likely that the character might be able to read it somewhere within the world as well. This is probably the thing that makes me love Eberron the most. I can generally pick out what my character would know without having to make a roll. Generally, I’m going to be on the same page as my Game Master who has read the same books.  Giving lots of hints as to what the common people know is great, but there is one thing better.

Some books will tell you straight out what is known to the people and what is hidden from the general populace. When it is laid out like this it is easy to determine what characters know. Sometimes the game books mix mechanics and setting information, giving you a target that you have to roll for in order to get knowledge of that level about a world instance. This can be handy, if only in the sense that it helps a group gauge what sort of knowledge is present in the world for a character with a particular score in a relevant area.

The Dreaded Knowledge Roll
No matter how well defined the setting knowledge might be, there are always going to be instances where you have to test whether your character knows something specific. In those instances it becomes time for the Dreaded Knowledge roll!!! Why dreaded? Once again, it is relative. It all depends on how your group handles it. Some groups play by the rules that if a person fails a roll to know or remember something, then there is no chance to have that knowledge until a new opportunity to learn occurs. When the piece of knowledge is infinitely important in that one moment when the roll is made failure can be devastating. Does the tech know that the type of fuel MunsterTreeOfKnowledgerods he bought for the ship leak deadly radiation? Does the PC who is of a monstrous race know about the xenophobic (read torches and mob) tendencies of the country they are travelling to? Failing that knowledge roll can sometimes cause major issues, but it can also cause great opportunities for play experiences that rely on roleplaying and quick wits. Failure can be fun, when seen from the right angle. In contracts, sometimes, having too much knowledge too easily accessible can be the problem. Being able to make a roll and know a particular thing can undermine opportunities to engage the characters in the story. If a character makes a roll and identifies the handwriting of the true villain, then the planned scenarios to hassle the PCs in their investigations and reveal the true scope of the treachery might be lost. A good Game Master will rework the story and find ways to make it meaningful, but knowledge can be the most dangerous thing out there.

Hash It Out Beforehand – Roleplay It After The Fact
So one thing I realized as I was writing this is that every instance is going to be relative to the situation. Too much or too little knowledge can be good or bad, in equal measure. Every group’s play style is going to deal with game and world knowledge differently. The only thing I can really say for certain about the issue of common knowledge is that it should be addressed by the group, preferably before the game starts. I’m a fan of including something about what most characters know in the Game Charter (which is really just a better term for Social Contract). Saying something as simple as “You probably know a little bit about monsters of low levels and the war. You can make a roll for more info if you’ve got a relevant skill.” provides a baseline for players to work off of and starts everyone off on the same page.

That will at least get everyone on the same page to start, but it isn’t going to eliminate all the issues. When disagreements or contentions about whether certain knowledge is common or knowable come up I have one suggestion. Let the piece of knowledge stand (information is tricky in that the effects of knowing something can’t really be taken back) but justify it with roleplaying. A player read about the special monster killing metal and the Game Master wanted that to be a secret revealed in-game? Even though the player might try to keep it out of game, some part of his mind is going to be working on how to make use of that knowledge. So let it become in-game, but make the player pay for it with a good story about how he overheard soldiers talking in a bar or actually listened to the ravings of the madwoman who said her aluminum pitchfork drove the monster away.

Most issues with common knowledge come when it isn’t commonly known what is considered common knowledge. What kind of experiences have you had with common knowledge in your games? Any instance where knowing or not knowing something had a major impact? How does your group handle determining what is well known and what isn’t?

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John Arcadian is a writer, gamer, art director, web designer, crafter, and kilt-wearer. You can find more of his writings on gaming over at For web-design projects, check out
  1. unwinder     | Reply

    If I was reading a campaign book, and I knew that my players had access to the campaign book, and the campaign book said that the monster’s weakness was aluminum, then the book would be wrong.

    Because it’s my campaign, and I say it’s bronze.

  2. Rafe     | Reply

    Interesting. It’s been a long time since this has come up for me in a significant way. Again, I play Burning Wheel and it addresses knowledge issues with -wises, such as Fortress-wise, Family Secrets-wise, Corrupt Officials-wise, Wine-wise, Rich Young Lady-wise, Countryside-wise, whatever.

    You then have two options when rolling it: You can either create the fiction you want (“There’s an abandoned fortress over that ridge where we can rest up.” – Fortress-wise, or Ruins-wise, etc) or you can seek information from the GM, as per D&D and other systems.

    The first option is what makes it awesome. The GM doesn’t have any specific plans for that town up ahead? Well, one of your players might. “The town’s been crawling with religious zealots recently and there’s no end of tension between them and the townsfolk.” (Converts-wise, Faithful-wise, Rumour-wise, etc) Sweet! Now there’s something there, and whaddaya know… it matters to at least one player.

    One could introduce the same sort of idea (the other side of the Knowledge check “coin,” in other words) to D&D pretty easily.

    I really like the “Hash It Out Beforehand Then Roleplay” part, John. I think that’s the best option for just about any system.

  3. mougoo     | Reply

    Though I’ve not logged my requisite Burning Wheel hours in yet, I’m with Rafe on the “creating the fiction you want” option (a great turn of phrase, by the way). Sure, the GM can abuse the player by telling her she couldn’t know something, or get burned when the player rolls well to know something he really shouldn’t know… but it always seems far more interesting to say to the player, “How does your character know that fire overcomes a troll’s regeneration?”

    Perhaps she heard stories as a child. From whom? Boom–the GM has a hook for a future story. Maybe the trolls are pissed that some retired adventurer is revealing their weaknesses to children in the characters hometown, and so attack the town, and your characters have to intervene. Or perhaps the character was in the militia and defended a town against troll marauders. The GM can then reason that the trolls know as much about the character as the character does about the trolls–perhaps the trolls know the militia tactics well and get a numeric advantage against the character.

    Of course, the former example is fun and story-driven, but the latter example runs the risk of not being “fair.” So, for me, the latter example is where the “knowledge check” roll comes in. The GM can invite the player to explain how he could know the information, then make a roll. If he succeeds, he knows and can act on the information. If he fails, he knows and can act on the information, _and_ some penalty arises out of the circumstances of the backstory.

    This can work the other way, too… if the GM sees a player metagaming (attacking the troll with fire), the GM can call for a knowledge check in the above manner. This way, if a player chooses to act on something, he doesn’t have to later pretend to forget about it–he just has to be willing to live with the consequences.

    And, let’s face it, the consequences are generally what makes the game fun.

  4. Gamerprinter     | Reply

    As a general reply I’d say consider this in the Real World Today, the majority of people are more educated so we know about all kinds of things. Combine that with information dessimination – internet, television, new things and new ideas are spread much faster.

    In a fantasy world (most likely) neither case is true. Consider how little one knew 50 years ago, 100 years ago, 500 years ago – compared to now. The average person didn’t know what was going on in the next town. Only the most educated had a wider idea, and even they did not have widespread knowledge. The discoveries in one place my not get around the world for a century.

    Common knowledge in a medieval fantasy world is pretty slim. I never let my PCs get away with that. I have a problematic PC that tries to incorporate his knowledge of metal alloys in trying to create new weapons and armor. I constantly remind him, that he knows it, but his character has no idea. Even if he were a dwarf, he would be more knowledgeable than the average character, but he wouldn’t have the player’s knowledge regarding such technology.

  5. BishopOfBattle     | Reply

    In my campaign, I’ve always treated player knowledge AS character knowledge. It helps that my group is generally new to roleplaying games and so doesn’t have the same knowledge base more experienced players have. But if a player knows that werewolves are weak against silver, then that’s great, their character heard a story one time about that and that’s how they know.

    If the discovery of the special metal that can be used to combat these creatures is a major part of the plot, then I see two solutions. A) The enemy has mutated an immunity to that metal, so they have to discover a new way of combating them. B) Create an all new baddy (but use the same stats and behaviours of the original creature), they’re not werewolves, they’re the dreaded Wyzers, who change into animals on full moons, but there’s rumors that they have a weakness to something!

  6. mougoo     | Reply

    @BishopOfBattle – Has this method of approaching character knowledge ever created feelings of exclusion among relatively less experienced players, or story continuity problems?

  7. Scott Martin     | Reply

    This line drives my wife crazy. She has a serious issue with players using out of character knowledge… and usually takes a sharp view of what’s justified. In part that’s because the rest of the group embraced metagame information to an annoying degree while she still didn’t know– but it also robs the monsters of their something special if their weaknesses are all known OOC.

    I like the compromise above: if you take advantage of a weakness, you have to narrate a flashback (or something) explaining how you learned. Solid die rolls (or skill levels) are very helpful at getting everyone on the same page.

    One great way to encourage sticking to IC knowledge is to reward players for not using their special knowledge. Bennies, an extra action point, or immediate willpower recover are all great ways to say “atta boy”. If you combine that with unwinder’s solution: it’s vulnerable to one metal, not necessarily the one printed in the book– you can keep people on their toes and reward the discover in game.

  8. BishopOfBattle     | Reply

    @mougoo – I have not personally had any issues with the setup. I’m reletively new to GMing though so I wouldn’t consider it all encompassing. My successes with it could be as much the setting (Shadowrun) is pretty easy to grasp, the fact that the more knowledgable / experienced group members are also good players in that they help ensure everyone is having a good time, or it could be that the pieces of information in our plots that DO matter aren’t things that you would read out of a book and are instead fictitious backgrounds and connections and details.

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John Arcadian