This is my second watch, the first having been back in 2009, and, although I was able emotionally to the characters a lot better this time around, and although I have a bit more of a philosophical baggage now (and this movie invites a lot of philosophical thought), I still find it hard to engage with it intellectually. Maybe a straightforward way to think of it is as a reverse Plato’s cave, or perhaps Baudrillard’s notion of simulacra.
Caden becomes more and more obsessed with reproducing his life in fiction, or at least the bits of it that we see in the movie (which by itself could be seen as an idealized version of his actual life). This is clearly untenable, however, as neatly represented by the story of Sammy Barnathan, his doppelgänger: first, he moves in with Claire, showing that the fiction-reality street is two-way. Then, he becomes romantically interested in Hazel, where he really should be interested in her doppelgänger. Finally, he jumps off a building, killing himself, unlike Caden, who had tried to do the same but was stopped.
Eventually Caden realizes that his fiction has no connection to reality (the last stage of the simulacrum), and reimagines himself as a woman. At the end, his only connection to reality is a recording which tells him how to interact with the world. What a downer.