So I saw Watchmen a couple of weeks ago. Was depressed when I saw it; good film to see when you're depressed. Lived up to the comic book, at least the comic book as it survived in my memory from reading it once back in '88 or so. The one thing that really nagged at me, though (and possibly my depression at the time exacerbated it), was Dr. Manhattan's decision to leave Mars and come back to Earth.
He hears Miss Jupiter's origin story and suddenly gets awestruck by the amazing coincidences that go into making each human being: the patterns this creates convince him of the miracle of life, and so he loses his nihilism and comes back to save humanity. Or something like that. I didn't buy it. All of those coincidences could be just that: coincidences. They only seem miraculous because he's starting from the reality of Miss Jupiter. But that's the wrong starting point: start with the coincidences and everything reverts to random. One of those coincidences doesn't happen and you just don't get Miss Jupiter, that's all. You get someone else, or no one at all. No big loss to the universe. Dr. Manhattan of all people should understand that.
I reread the comic book a few days later, and three things struck me that helped me make sense of that moment.
First, in the comic book the moment is set up better. I don't buy Dr. Manhattan's decision in the comic book, either, but at least there they do a little more groundwork for it, by having it follow Rorschach's origin story (which was curiously absent from the movie), and particularly his speech about why he chose the mask he did, and his relationship to morality. There's no absolute right or wrong, no meaning, just whatever pattern we choose to impose upon random events; but Rorschach chooses to impose. We get this discussion, then we get Dr. Manhattan's epiphany, which is also about seeing patterns.
Second, and related, is the awareness this creates that Dr. Manhattan might be wilfully imposing a pattern where he knows there is none. I.e., he wants to see meaning. He's intentionally starting from the wrong starting place (Miss Jupiter's existence). Maybe he's not as alienated from his original humanity as he thought. Maybe that's what the smiley face in the Martian sand means (and it's there in both comic book and movie): it's just a random product of rocks and shadows and whatnot, but we humans will anthropomorphize anything into a smiley face. Maybe this is a tip-off that we're not supposed to necessarily buy Dr. Manhattan's epiphany: he's lying to himself.
Third, and this is true in both movie and comic book, it doesn't matter. He has his epiphany, reembraces humanity, and comes back to save the world - and he doesn't. Nothing he does from that point forward makes any difference. He can't even stop Rorschach from posthumously spilling the beans. The big blue naked guy is a red herring.