(This is a based on an earlier draft entry. I thought it'd be better to repost with edits than to edit the original.)

This goal of this post isn't to define RPGs. Rather it's to provide a categorical survey of defining characteristics, as suggested by various observers.

First note that all games except a very few have elements of freeform, and even those that don't still have a fiction; otherwise, they are merely (virtual) kinetic art. (By the first I mean, very few games tell you precisely what to do at every step. Chutes and Ladders does. Chess and Monopoly do not. By the second I mean that the game proposes a set of meanings--often the concept of "winning and losing"--that have no real impact outside the game.)

So what is an RPG? What distinguishes it from other games? Markus Montola has proposed some criteria for roleplaying. An earlier discussion on rec.games.frp.advocacy also comes to mind.

Lea Crowe wrote:

Specifically, I think, a wargame does not concern itself with "literary" issues: character, plot, mood, etc. In a wargame, the action is all. [1]

This may be a side point, but in the majority of (modern) wargames, action is delimited by the rules, rather than merely being guided by them. For example, you can only use the tactics of spying, seduction and assassination if there are rules for them -- you can't just come up with a "spy" unit, any more than you can arrange a Mafia hit on someone in Monopoly. [2]

Lea's first paragraph refers what I'll dub the thematic or aesthetic criterion. It's been a problem for RPGs for a long time. Arguably this criterion underlies GNS (in the sense that aesthetic goals are what GNS is about instead of formalism and procedures). It's also related to some of Markus Montola's criteria.

The second paragraph is the freeform procedure criterion. I think this is a weak criterion for RPGs but it's advanced frequently. Essentially it's the criterion which says that the vision of the world overrides formal rules, or rather the vision of the world and how it can be acted on by the players cannot be encapsulated in formal rules.

In response to Lea, I added:

--Wargames generally have unambiguously defined "victory conditions" as part of the rules. RPG's generally don't. [3]

--Wargames have well-defined conditions for when the game ends. RPG's generally don't. [4]

The third criterion, which I proposed, is the motivational criterion. The claim here is that RPGs do not provide clearcut purpose, within the game, to guide player "moves". Consider: tennis, within the game, is motivated by scoring points and winning the game/set/match. (The goal of winning the match might conceivably override the goal of winning the game. As e.g. if you make shots which your opponent can score on provided he or she exhausts herself. But there is a unitary goal guiding your strategy, tactics, and technique/skill.) Outside the game, tennis may be guided by things like trying to impress someone on the sidelines or not making your boss look bad. But the goal is in the fiction of the game and the metagame goals are achieved via the game fiction.

By this criterion, an RPG explicitly does not have a formal goal in the fiction. I think this is an essential criterion, but it is sometimes excluded (generally only provided freeform criterion is satisfied; otherwise you have a closed system that becomes boardgame-like).

The fourth criterion, above, is the endgame criterion, but I think it's been basically disproved. At most it's a special case of the third criterion. Nevertheless it's still expected by many that RPGs will either go on indefinitely, or end only when some non-formal condition is reached, such as general agreement that all the "story arcs" have been played out.

[The rest of this post remains highly sketchy. Sorry.]

Now compare: pictionary, charades, the imagine-a-journey game, etc.

added: note that I don't use the word role above. So let's read what Jonas Dagar has to say about "not an RPG" and Wittgenstein. I find it very exceedingly useful to imagine that "these games" are not being called "RPGs" or even "storytelling games". These terms imply motivation and may (1) constrict play and (2) give a designer an excuse not to really explain their game. Charades doesn't have that problem. Nor does Werewolf. So what are "these games"?

Also look at this rpg.net thread about Capes.

Inspired by a thread on RPG.net (Misconceptions about Traditional Play) I found a passage from an interview with Dave Arneson very interesting. In the RPG.net thread I'd talked a bit about the traditional social authority of the GM, how in some cases it could extend to things like choosing the game system, making up the campaign completely on his own whim, deciding what to have on the pizza, kicking people out of the game, etc. And I referred to the hilarious stories of Al Bruno (scroll down to the editoriALs) as prime examples of that sort of stuff. As if, once a "group" decided to "play an RPG" with a particular person as the GM, that was taken as implied election of a dictator. In reality I rarely played under those conditions--the closest being the awful AD&D campaign I played as a college freshman--but the taste of it lingers, and I don't find it hard to believe that it's been more or less true of many groups. So how did this start?

Well, for one thing, it goes back before RPGs. I mean, in baseball we've got umpires who not only make judgments and rulings related to the on-field action, but also have the authority to throw people out for bad sportsmanship. And we all know that whoever owns the ping-pong table gets extra say. I don't think we can really trace it back to the origin. But here's a wonderful example from the dawn of the modern RPG hobby.

Mr. Arneson: [...] I had a weekend off, so I sat up reading books, eating popcorn, and watching the boob tube. I drew up a maze and populated it with creatures. Then the next time someone showed up for Napoleonics I said that we were going to do something different.[...]

Pegasus: So historical gaming did influence you when you set up Blackmoor.

Mr. Arneson: It certainly did. We established (in our historical campaigns) the principal of having a Judge who everyone listened to and who set up the battle or campaign. That’s where we were coming from, traditional wargaming.

Pegasus: It’s nice to hear about a campaign where people listen to the Judge. I’ve seen a lot of campaigns that are a little more chaotic.

Mr. Arneson: Yes, but it took a lot of forceful diplomacy on my part (the baseball bat helped). The games were held in my basement and I have thrown out disruptive players. That way I established the fact that I was in charge and when I talk you had better listen. Then when others would Judge, I could use my influence to back them up by saying "If you don’t listen to this Judge, I’ll remove you". Before I knew it, even I was listening to the Judge whether I liked it or not.

(All emphasis mine.)