Thoughts on Shutter Island [SPOILER ALERT]

So it's been a while now since Shutter Island debuted in theaters. It's also been a while since I've seen the film, so the details of chronology and so on are a bit blurry. But one thing does stand out in my memory: The incredibly clever joke the film plays on the audience.

The film turns on one key question: Is the protagonist insane, or is he trapped in a vast conspiracy? The audience is driven back and forth between these two points for the majority of the film. Indeed, for most of the movie either is at least somewhat plausible. But by the end of the film, we (the audience) have decided. The truth is clear: The protagonist is choosing the coherence of insanity, if only to avoid being a monster.

And this is precisely the joke of it all. We've decided on a reality within the film. But it is a film. It's not real. We, just like the protagonist, have created a particular coherence out of something that is not coherent and not real.

Thus, it is we that are proven to be "insane".