I just saw it about a month ago for the first time. It was very interesting, and I think I could have much fun just making up various theories for it, like noticing that there are five layers, and seeing if they line up to the five stages of greiving--denial, anger, bargaining, despair, and acceptance.
If you accept that the reality (the top layer) in the beginning wasn't really reality, it would work as denial, the violent rainy city works pretty well for anger, the pulling of the crazy gambit is a pretty good match for bargaining, the bleak snowfield is rather fitting for despair, as is the apparent loss of the mission, and the final layer is where Cobb seems to finally accept the loss of Mal.
The biggest problem I'm having is tying the ending into that theory. if I could add that in a compelling way, I could rally buy into my theory, but for now, I more just toy around with it.
As a side note, ever since reading the Star Trek: TNG novel I, Q, there's a part of me that wants to analyze a lot of the media I encounter in the terms of Kubler Ross's model.
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I just figure it ended with reality. There's really not any point in doubting your reality. It only causes problems, because you have nothing to base reality off of. If you can't trust your senses, then you have no way of creating any empirical data, and you'll always have no information.
It's like in real life. Sure, maybe nihilism *sounds* reasonable, but no one is actually a nihilist.
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