What changes? There are no changes. Authoring is not changing the fiction - it is bringing it into being.Whether the DM or players make the changes is completely beside the point.
To me this seems to miss [MENTION=27160]Balesir[/MENTION]'s point about immersion.There is zero perception on my part that this Schrodinger's aspect of whether it was or was not the one ring was ever in play. I have never discussed the books or movies with anyone and received the slightest indication that they felt that a character not knowing a truth within the fiction made that truth in doubt to the larger story.
I want the experience of being in the story that way.
For Gandalf and Frodo, sitting in Bag End, the truth is not known. There is doubt - and the possibility that the ring is not the One.
So experiencing being in the story would mean experiencing that doubt - which, mechanically, means not knowing how the dice will roll.
To me (and, in light of his post, I think also [MENTION=27160]Balesir[/MENTION]), learning the GM's pre-authored fictional truths is not experiencing being in the story at all, but rather having the meta-experience of learning the content of an already-written story.
Relating this back to the example that you described as changing: the players in my BW game, both for themselves and in character, are wondering and debating the nature of the mage PC's brother. Was he evil before he was possessed?
Unexpectedly, when looking for something quite different (the mace), they find the black arrows in his (now ruined) private workroom. This is a new, and hitherto unexpected, sign which suggests (i) that he was evil before being possessed, and (ii) that he had some connection to the killing of the elven ronin PC's master. It is new to the characters. And it is new to the players - so, for instance, they don't have to play at being shocked, because they are shocked.
The revelation wouldn't be more shocking if I (as GM) had decided it in advance.
I think this is the sot of thing that Balesir was intending to get at in his reference to immersion and discovery.
In the "player driven" game that uses scene framing, "fail forward" etc, the events are also reflective/expressive of "character driven" action in your sense of that term - the unfolding events also reflect the unfolding of the PC.the fact that we have a "player driven" option, in which the character drives the action, and the player has an avatar of a character, that "character driven" means "character drives events". It is a drift in language use I was trying to elucidate here. "Character driven" has little to do with how events unfold. Character driven stories are rather the opposite - they are less about how events unfold, and more about how *character* unfolds.
Which is to say that, in the terms I'm using, "character driven" and "player driven" are more orthogonal than we might at first think.
<SNIP>
Ultimately, "I get to author things," is not a guarantee of anything, including player engagement.
It's true that, in fiction generally, there can be character-driven stories where the events are not driven by the character, but I think that has to be harder to pull off in RPGing (doesn't it?) because of the place of player action declarations in RPG play. If players are declaring actions for their PCs, then player and hence PC choices drive events (but, in scene-framing, "fail forward" play are also expressive of the character in the "character driven" sense). But if events are not driven by character choices, then it becomes much harder for the game to be character driven, because of the divorce between the authorship of events (the GM) and the authorship of the character's inner responses (the player).
On "authoring" in general, I'm not advocating for player authorship in this thread. (Though it can have a place, I think.) In all the examples of play I've given and linked to, the framing of challenges and the authorship of the backstory is primarily with the GM. I see the discussion in this thread as not being primarily about the identity of the author, but the timing of the authorship.