Inception is one of those movies people theorize about, so here’s my take. I have not read about it or looked it up except to check the characters’ names, so this is based solely on what I got from watching it. Needless to say, tremendous spoilers follow for those who have not seen it.
It’s all a dream. Ariadne (Ellen Page) is leading an inception on Cobb (Leonardo DiCaprio). The entire film is that inception, and we never see reality.
In reality (which I will label “level 1”), the details of Cobb’s wife and past are basically as we’ve been shown. To help him get over her death and move on, someone has arranged an inception to implant him with that idea. (We don’t know who arranged this, or why; more on that later). The characters we meet as Cobb’s team are actually Ariadne’s team.
When the inception process is explained in the film, we’re told the characters must go three levels in— a dream within a dream within a dream— to get deep enough to implant the idea. Well, that’s not deep enough on someone as skilled as Cobb. To make this work, they must go five levels in, and they can only do that through what the film calls “running with Mr. Charles”. They must turn Cobb’s subconscious against him and trick him into going deeper by convincing him he is running an inception of his own on someone else.
The highest “reality” we are shown is actually a dream (level 2). In this level, Cobb is a vigilante on the run. The forces out to get him are actually projections— his defense system. (Mal makes that comparison toward the end.) He is given a strong incentive to perform an inception on Fischer— who, in level 1 reality, may not even exist.
Ariadne presents her dream-self to Cobb as someone who will become his confidant. Because she is a neophyte, he can trust her. Because she relies on his guidance, he is not threatened by her. Because she is a prodigy, she can swiftly “learn” everything she needs to know without contradicting the above. And she is recommended to Cobb by Cobb’s mentor and father figure; we are told later that someone’s relationship with their father informs the path to their subconscious.
Ariadne’s bond with Cobb doesn’t come from curiosity or happenstance. Her goal all along is to get into Cobb’s head and deal with his issues. When she wants more info or has strong feelings about how to proceed, she isn’t just concerned; she’s hitting him up for information and trying to direct his path. When she catches him sneaking dreams with his dead wife, she caught that on purpose.
Levels 3, 4, and 5 are presented as the inception on Fischer. This is all one big red herring; what’s presented to us as Fischer’s journey is really Cobb’s. The “real” (level 2) Fischer is sedated on the 747. In his dream (level 3), he is kidnapped, and everybody goes to sleep in the van, leading to level 4. On this level, Cobb informs Fischer that he is dreaming. (Fischer thinks level 3 is reality, and Cobb thinks level 2 is reality.) Browning is framed so that Fischer will have an excuse to go into Browning’s head. There are several levels of deception on level 4: Fischer thinks he’s going into Browning’s head, Cobb is using that belief to get deeper into Fischer’s head, and Ariadne is using THAT belief to get deeper into Cobb’s head.
On level 5, Mal shoots Fischer. The film portrays this as a huge problem that can potentially strand everybody in limbo. Not true! It was all part of the plan. Cobb had to believe that his irrational refusal to accept his wife’s death had led to disaster, making his problem as urgent as possible. This is achieved when his refusal to shoot Mal, even though he knows she’s not real, leads to her shooting Fischer and endangering everybody. The stakes are finally high enough so that Cobb has both a reason to go one level deeper and a reason to sort his problems out, once and for all. (At the very start of level 5, Cobb wonders what’s there for Fischer, and Ariadne says “what’s there for you?”)
It is Ariadne’s idea for her and Cobb to go one level deeper. In level 6, Cobb finally learns to let Mal go. THIS is his inception! In a dream within a dream within a dream within a dream within a dream, he is implanted with the idea that his dream-wife is not his real wife and that he must move on; this idea, implanted so deeply, will grow in him.
Meanwhile, Fischer’s inception works too: his father tells him on level 5 to be his own man, and on level 3, Fischer tells us that the dream made him realize he needs to do that. When Fischer wakes up on level 2, he just thinks he’s had an inspiring dream about his father and fellow passengers, not knowing it was all an elaborate attempt to change how he thinks about his father. Cobb got his end of the deal, and could finally go home to his kids.
When the film ends, Cobb wakes up. The entire film has been a dream that helped him realize how he needs to handle his wife’s death. Ariadne’s work is done.
As for who arranged the inception, and why? It doesn’t really make a difference. Maybe someone benevolent wanted to help Cobb move on. Maybe someone stood to gain from Cobb’s emotional breakthrough, similar to Saito’s reason for ordering the inception on Fischer. Maybe Cobb was in “limbo” the whole time, and this was a rescue mission. But I had a thought about this— the final thing I realized before writing this post.
We don’t know what’s happened in level 1 since Mal’s death. All we really know is that Cobb feels guilty about it. But reuniting with his kids is such a strong motivation on level 2 that it’s probably true on level 1 as well. On level 2, he can’t see them because he’s on the run from the law, but since that’s just his self-defense system, that can’t be true of level 1. So what’s another reason why he might be separated from his kids, and might need to work through Mal’s death before seeing them again?
It’s a bit obvious, but it fits: Cobb’s inability to deal with Mal’s death has driven him insane. He’s probably in an asylum, and probably wishes he could go back to his kids and a normal life. Ariadne’s motivation is probably therapeutic. When Cobb wakes up in level 1 and has learned to cope with Mal’s death, he will have been healed.
And in the asylum, he is, of course, inmate #528491.