I'm a little curious as to what makes a story linear or non-linear. When I played Oblivion, I distinctly remember the main quest progressing from A to B to C to E, etc. Sure, at any time I could stop and go do something else, but when I came back to it, it was still the next step in the sequence. If that's not linear, I don't know what is.
I think it varies a bit depending on who's talking
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My take is that Morrowind and Oblivion were semi-linear, in that you didn't have to complete all quests in a prescribed order. However,
each quest had to be completed in a prescribed order, and the quests were essentially independent of each other. It didn't actually change anything in one quest if you took time off to do another.
Dragon Age 2 and was rather more linear because there were a couple of choke-points in the story. You had to complete all the quests in a chapter, because they didn't carry over to the next. Mass Effect 2 was even more linear because it had even fewer side quests than Dragon Age 2, and they tended to be doled out as you progressed through the entirely linear main story.
The Witcher 2 (which I've only just started, so I don't know a lot about it) seems to be almost completely linear. However, it does have the rather hard to pigeonhole feature that the events that occur throughout the linear story are altered by your actions earlier in the story. Other RPGs do have that, but to nothing like the same extent end with nothing like the same sense of events just occurring as they will.
If there are any truly non-linear RPGs, where you can perform quests in any order and the actions you take in one quest will effect events in another (or the other way round, if you do the quests in a different order), then I haven't heard of them. And I suspect that and RPG like that could only be produced by a bunch of brilliant and warped minds
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