Taking negotiation as "discussion aimed at reaching an agreement" one rhetorical consequence I have noticed - in part through our debate in this thread - is an implication that such agreement is contingent.
It's contingent on the discussion.
One purpose of perceptual systems - speaking roughly - is to produce shared cognition of real states of affairs. That is, when you and I look at a thing, we both see the same thing and form - in some rough sense, at least - the same belief about what we are seeing. (Of course there are optical illusions and other tricks of the light - it's not a surprise that chess boards and pieces, playing cards, dice, etc are generally designed to minimise such problems by using crisp designs, clearly contrasting colours, etc.)
The Australian philosopher David Armstrong used to say that
to perceive is
to come to believe by way of the senses. Whatever one thinks of this as a philosophical account of perception, it captures the notion that when perception is going well, the resulting cognitive process and content is
constrained by something "external" and hence not voluntary.
Imagination is, by its very nature, not apt to produce the same sort of convergence of belief, precisely because imagination is "active" or "creative" in a way that perception is not. What I choose to imagine is up to me. Suppose I imagine a situation or a series of events - how I imagine
what comes next is up to me.
From the above, it follows: the way to get two people to agree on the state of a chess game is to show them the same board with the same pieces. Notice that they can do this themselves, without the need for any third party,
by manipulating their own pieces on their own board.
(Cue someone mentioning blindfold chess. Blindfold chess is like mental arithmetic or mental geometry: it is the generation of logical consequences from starting premises plus the periodic introduction of new geometric propositions ("Knight to ab3"). We don't need to solve the philosophical problem of the difference between (i) logic and mathematics and (ii) empirical knowledge to notice that, having read the first four chapters of LotR, you can't work out what happens next simply by using geometric or arithmetic reasoning.)
How do you get two people to agree on what happens next, after the first four chapters of LotR? You can introduce a third person who tells them what to think: ie JRRT, who has written the fifth chapter. But now we have a storyteller and an audience, not a RPG.
In a RPG, how do we get two people to agree on what happens next? They talk about it; and sometimes they use rules and other mechanics. They regulate their talk by principles of "ownership" and authority that are sensitive - often in quite subtle or idiosyncratic ways - to
what is being talked about, or to
what just happened in the fiction, or to
what just happened in the real world such as a die throw.
The preceding paragraph captures what is at stake, and the reason for using the word "negotiate" to describe it. There is no implication that agreement is hard to reach; or will not be reached. Though obviously sometimes it is not - RPG play seems prone to "bust up" in ways that chess play does not, and understanding the different ways in which the two forms of game play establish and resolve position makes it fairly obvious why this difference obtains.
If you or anyone else wants to introduce a more nuanced vocabulary for describing the different ways in which conversation between RPG participants generates agreement on the shared fiction, based on phenomenological or other principles, go for it! Though personally I don't at this stage see how that will have much bearing on the sorts of design questions Vincent Baker is interested in addressing.