All of Christopher Nolan’s other films are best understood as film noir, with the possible exception of The Prestige. Films in the noir genre, are often (always? almost always?) told from the point of view of a protagonist who thinks he knows what is going on and perhaps even believes he is in control of the events of the plot, but who, in the end, realizes that he was being conned and really had no idea what was going on the whole time. (Under this description, even The Prestige might count as a film noir.) Hence noir films eschew Hollywood endings and end tragically, as do all of Nolan’s films prior to Inception.
Inception, however, seems to belong in a different genre. On the surface at least, Inception is a heist movie. (See my earlier post about heist movies.) A heist movie is almost the exact opposite of a film noir. A heist movie is told from the point of view of a protagonist who really does always know what is going on and is really in control of the events of the plot, even the events that seems like mistakes or random accidents that benefit his opponent. In fact, we might even say that the only difference between a noir and a heist movie is perspective. A noir is told from the perspective of someone being conned, while a heist movie is told from the perspective of the con artist. Since the perspectives are different, then the ending of the story has a different valence. The same ending would be a happy ending in a heist movie and a tragedy in a film noir.
Now if the reading I suggested in my previous post is correct, then Cobb is conning on himself. The movie is, at bottom, a film noir like all of Nolan’s other films. But since both the con artist and the one being conned are the same person, if the con is successful then the surface of the movie (the part from the perspective of Cobb’s conscious self) will take the form of a heist movie. And, this might help explain the appearance of a happy ending. It’s not that Nolan is suddently feeling more optimistic than he has in the past; rather, as a heist movie, the film must have a happy ending in order to fit the genre conventions. But there are enough clues in the film to make the viewer doubt whether the ending really is happy.
Cobb’s conscious self seems to be in control, but really there are subconcious forces conning him, subconscious forces that Cobb carefully orchestrated while awake to fool himself in the dream. The happy ending itself is the con.