At the end of the film, when Teddy explains to Lenny how he (Lenny) killed John G a long time ago and keeps creating little puzzles for himself so he can do it over and over again, Nolan's interpretation (
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Granted, Teddy is definitely a manipulative character and there's no question that he's been using Lenny, but I think the whole films works far better both in terms of the basic narrative and especially in terms of theme if Teddy is telling the truth in that scene. If you take Teddy's end-of-the-movie explanation at face value, like I do, then Memento is making a depressing but satisfying statement about how Lenny is making a conscious choice to live in a never-ending quest for revenge as a way of giving his life meaning. If you go with Nolan's interpretation, that theme evaporates and the whole movie becomes about what a #### Lenny is, which isn't anywhere near as good IMO.