It helped, a little. But some thoughts:
One of my biggest immediate questions about the end is how we can get there with no Observers. There are at least three key points in Peter's life influenced by September: interrupting Walternate when he created the cure for Peter's illness, saving Peter from drowning in Blueverse, and convincing Peter that it was okay to believe in Olivia's love for him in Amberverse. Take away any one of these things, and we change the outcome of the story drastically. I can accept that Peter himself being a paradox within the Amberverse somehow protected him from the effects of the first two, but not the third. We also have the problem of how Walter mailed the tulip and (presumably) got the video to Peter, which once again seems most likely to have been the work of September, who would not have existed to run that errand.
It also seems to me that Peter's absence from Amberverse causes a whole host of problems in terms of the events of the first three seasons. If Peter wasn't there, what was the impetus for Olivia and Walter to cross universes? How was the machine activated in Redverse if Henry never existed? The solution that seems neatest to me is that history was not altered, only the memories of people in both 'verses, and the Blueverse became the Amberverse in 2010, not 1985.
(As an aside: isn't the new Redverse also a different timeline from the original? The differences are much more subtle, of course; the main thing I see is a change in Walternate, who has not spent the last twenty years obsessed with getting revenge on the other universe for stealing his son. He seems less ruthless, more willing to compromise.)
The "history never changed, only people's memories of it" explanation also gives a possible reason why Peter was not completely erased: because those events did actually happen, he still existed in Olivia's memories, and to a lesser extent Walter's, and that was enough for Olivia (or the machine -- that's never made clear) to grab onto and pull him back into her 'verse. Maybe that solves the issue of Obserververse, too (it all still happened the way we saw it play out, but everyone's memories of events are changed), but that doesn't seem as neat to me, somehow.
Or maybe my problem is simply that I'm trying to apply simple logic and cause-and-effect to explain Fringe. ;) I'm willing to admit that might be the case. But I'd rather come up with a theory that works, if I can.
(Crosspost from Tumblr.)
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