Just an idea I had.

A player has two plot-building resources: character Beliefs and a number of "Plot Points."  A Belief is a one sentence declaration of what your character honestly believes.  They would also give in-game benefits.

Before the beginning of a Scene of a single session of play, a player looks at another character's Beliefs and spends plot points on challenges to those Beliefs.  The player of the character in question can say "Yes, but..." somehow, probably with a successful roll on one of the other stats, but not "no, that challenge never happens."

Just as an example, say we're running a shoujo-manga game where everyone is allowed 3 core Beliefs.  You describe Junko's three beliefs as "I can win at any martial arts challenge," "My friends are worth dying for," and "Girly stuff makes you weak."  Someone spends plot points on a challenge to "Girly stuff makes you weak:" apparently she meets a very traditional Japanese girl that also happens to be a master of Zen archery.  Someone else challenges "My friends are worth dying for" by having her best friend snub her for a foolish reason.

This is a very rough, sketchy outline of what I'm trying to do: mostly I want a nice and Narrativist way of reducing reliance on a GM to generate plotlines.  Comments?

I like the general notion.  I think it's very nice to get that stuff clearly communicated ... out on the table where other people can contemplate it, and see how to poke at it.  There's a very natural reaction in some gamers to say "Oh, you believe that, eh?  Well, let's see you stand up for it!  How about if it's challenged in this way?  In that way?  What if I find a situation in which two of your beliefs are mutually contradictory?"

That having been said, sometimes one targets these well, and sometimes one targets them poorly.  What's the incentive (to the players) of really getting a good zing in on their target?

TonyLB wrote:
(Snip!)
...Sometimes one targets these well, and sometimes one targets them poorly.  What's the incentive (to the players) of really getting a good zing in on their target?

You know, I genuinely try not to say this often (both from humility and a rational understanding that comparatively few people actually ask the specific questions that Capes answers), but you might want to take a look at Capes.  You're very sympatico with it.  Wierdly so, if you haven't seen it yet.  Sorta eerie, really.

That's a very solid idea you've got there. And with my current projects, anything moving away from GM-centricity is a plus.  Check out the Gangster Mechanics thread a little further down for some ideas that are also inspiring and which move along a similiar line. You might find something that meshes.

As for my own suggestions:
I think what we're talking about here is akin to what Tynes and Stolze in Unknown Armies call Emotional Reality mechanics as opposed to physical reality mechanics. In which case, we're using beleifs as an excuse to make things happen in the game because they "feel right." That is certainly very exciting and rewarding for many players.

So rewarding players for having strong or more coherent beleifs may be in order. How about this:
You can use your any of your beleifs to initiate a game event at any time. You describe the event and have a say in its outcome (perhaps the more time you've used that beleif, the more say you have.) However, if someone challenges that beleif, you must accept consequences equal to the times you've used it to your advantage (perhaps this also clears the "slate" and allows you to start again.)

Arpie wrote:
As for my own suggestions:
I think what we're talking about here is akin to what Tynes and Stolze in Unknown Armies call Emotional Reality mechanics as opposed to physical reality mechanics. In which case, we're using beleifs as an excuse to make things happen in the game because they "feel right." That is certainly very exciting and rewarding for many players. /quote[]

Yes, that's what I'm going for, a way of setting up emotional and moral reality for characters in a better way than the leading national brand. 

Arpie wrote:
So rewarding players for having strong or more coherent beleifs may be in order. How about this:
You can use your any of your beleifs to initiate a game event at any time. You describe the event and have a say in its outcome (perhaps the more time you've used that beleif, the more say you have.) However, if someone challenges that beleif, you must accept consequences equal to the times you've used it to your advantage (perhaps this also clears the "slate" and allows you to start again.)

I took a look at Capes Lite, and this is very similar to how Capes Lite handles the issue.  (Capes is spookily congruent with my goals, come to that, especially since I'd never even heard of it...)

Assuming a dice pool system, maybe - roll Belief + Stat to generate plot details, each success allows you to alter the plot according to a table, with differences between Colorful, Minor and Major events?

I was also looking at the thread about player-defined stakes - from The Price Of Faliure is Dignity to The Price Of Failure is Death - and thought that a numerical rating in a Belief, say from one to five, could be a good measure of how much you're normally willing to stake on the strength of that belief - and also how many dice to add to any attempted action with the highest stakes to defend or champion that Belief.  Yes, yes, when I get the money I will order Trollbabes to see how they handle player defined stakes...

The world I want to use this system for, by the way, is a transhuman space opera.  I thought that everyone on the same side must share two beliefs: one about a frightful interstellar war and one about the transformation of humanity's form and function through AI tech, mind uploading, genetic and somatic engineering, and such.