This entire post is a spoiler. Stop reading if you have not seen Inception, because 1) I will reveal major plot points and 2) It will make no sense.

The literary critic Frank Kermode famously argued that all successful works of art have the ability to inspire multiple interpretations. We read the classics, he said, because we believe they say more than the author meant. In other words, it is the ambiguity of art - this ability to inspire arguments and blog posts - that makes it so interesting.

Inception, of course, is all about the ambiguity. (Those who parse the wobbles of the spinning top in the final scene have missed the entire point of the scene.) This doesn't mean the movie is a masterpiece - I personally thought it was a smart summer blockbuster but no Dark Knight. That said, I found this interpretation, by Devin Farci, to be mostly convincing:

Every single moment of Inception is a dream. I think that in a couple of years this will become the accepted reading of the film, and differing interpretations will have to be skillfully argued to be even remotely considered. The film makes this clear, and it never holds back the truth from audiences. Some find this idea to be narratively repugnant, since they think that a movie where everything is a dream is a movie without stakes, a movie where the audience is wasting their time. Except that this is exactly what Nolan is arguing against. The film is a metaphor for the way that Nolan as a director works, and what he's ultimately saying is that the catharsis found in a dream is as real as the catharsis found in a movie is as real as the catharsis found in life. Inception is about making movies, and cinema is the shared dream that truly interests the director. I believe that Inception is a dream to the point where even the dream-sharing stuff is a dream. Dom Cobb isn't an extractor. He can't go into other people's dreams. He isn't on the run from the Cobol Corporation. At one point he tells himself this, through the voice of Mal, who is a projection of his own subconscious. She asks him how real he thinks his world is, where he's being chased across the globe by faceless corporate goons.

What I like about this interpretation of Inception is that it also makes neurological sense. From the perspective of your brain, dreaming and movie-watching are strangely parallel experiences. In fact, one could argue that sitting in a darkened theater and staring at a thriller is the closest one can get to REM sleep with open eyes. Consider this study, led by Uri Hasson and Rafael Malach at Hebrew University. The experiment was simple: they showed subjects a vintage Clint Eastwood movie ("The Good, The Bad and the Ugly") and watched what happened to the cortex in a scanner. The scientists found that when adults were watching the film their brains showed a peculiar pattern of activity, which was virtually universal. (The title of the study is "Intersubject Synchronization of Cortical Activity During Natural Vision".) In particular, people showed a remarkable level of similarity when it came to the activation of areas including the visual cortex (no surprise there), fusiform gyrus (it was turned on when the camera zoomed in on a face), areas related to the processing of touch (they were activated during scenes involving physical contact) and so on. Here's the nut graf from the paper:

This strong intersubject correlation shows that, despite the completely free viewing of dynamical, complex scenes, individual brains "tick together" in synchronized spatiotemporal patterns when exposed to the same visual environment.

But it's also worth pointing out which brain areas didn't "tick together" in the movie theater. The most notable of these "non-synchronous" regions is the prefrontal cortex, an area associated with logic, deliberative analysis, and self-awareness. Subsequent work by Malach and colleagues has found that, when we're engaged in intense "sensorimotor processing" - and nothing is more intense for the senses than a big moving image and Dolby surround sound - we actually inhibit these prefrontal areas. The scientists argue that such "inactivation" allows us to lose ourself in the movie:

Our results show a clear segregation between regions engaged during self-related introspective processes and cortical regions involved in sensorimotor processing. Furthermore, self-related regions were inhibited during sensorimotor processing. Thus, the common idiom ''losing yourself in the act'' receives here a clear neurophysiological underpinnings.

What these experiments reveal is the essential mental process of movie-watching. It's a process in which your senses are hyperactive and yet your self-awareness is strangely diminished. Now here's where things get interesting, at least for this interpretation of Inception. When we fall asleep, the brain undergoes a similar pattern of global activity, as the prefrontal cortex goes quiet and the visual cortex becomes even more active than usual. But this isn’t the usual excitement of reality: this activity is semirandom and unpredictable, unbound by the constraints of sensation. (This is usually blamed on those squirts of acetylcholine, an excitatory neurotransmitter, percolating upwards from the brain stem.) It’s as if our cortex is entertaining us with surreal cinema, filling our strange nighttime narratives with whatever spare details happen to be lying around. Furthermore, the dreaming state is accompanied by an increase in activation in a wide range of "limbic" areas, those chunks of the cortex associated with the production of emotion. This is why even the most absurd nightmares cause us to wake up in a cold sweat. We care about what happens in our dreams, even when what happens makes no sense.

I'd argue that Inception tries to collapse the already thin distinction between dreaming and movie-watching. It gives us a movie in which most of the major plot points are simultaneously nonsensical - Why are we suddenly watching a thriller set in the arctic? Why are all the subconscious mercenaries such bad shots? Why don't Cobb's kids ever age? - and strangely compelling, just like a dream. And so we bite our fingernails even though we "know" it's just a silly movie. Thanks to the subdued activity of the frontal lobes and the excited visual cortex, we sit in our plush chairs munching on popcorn and confuse the fake with the real. We don't question the non-sequiturs or complain about the imperfect special effects or the shallow characters. Instead, we just sit back and watch and lose track of the time together. It's almost as if we're being manipulated by Dom Cobb himself, as he effortlessly travels deep into our brain to plant an idea. But this Dom Cobb - we'll call him Christopher Nolan - doesn't need a specially formulated sedative. He just needs a big screen.

Image: Screengrab from the movie trailer.