Christopher Nolan, the director and co-screenwriter, is a man deeply interested in the idea of human beings driven to self-destruction by their own obsessions and noble (or at least, they're convinced that they're noble) intentions--the avenging amnesiac of Memento, the sullied and sleepless detective of Insomnia, the dueling magicians of The Prestige1--so the decision to allow him to helm the Batman film franchise should probably have been a foregone conclusion. Batman Begins wasn't so much a reinterpretation of the character as it was a reintroduction; making it clear once and for all that this hero of ours is not dashing, is not debonair, is in fact simply a damaged soul clinging to the edge of his sanity with one hand.
The tragic part being, he chooses to be there.
The Dark Knight takes that premise further, making Batman aware that the longer he stays there the more likely it is that somebody or something will wrench those fingers open, or he will simply decide to let go.
And so what we see from Batman in this film is the transformation of his obsession to end crime and corruption into an obsession to lay down his sword and return to the world of daylight, of humanity, of emotional connection. We see Bruce Wayne almost desperate to believe in Harvey Dent because he wants to believe that Batman was only a temporary measure until Gotham was ready to take care of itself.
Which is why the tragedy of Dent's physical and mental transformation into Two-Face is not only Dent's tragedy, but Batman's as well...it marks the moment that he realizes he can never go back (something the Joker said to him previously).
And let us speak of the Joker, taking only a moment to heap more plaudits upon the dizzying, unpredictable performance of Heath Ledger. Although his merciless bank heist represents the sort of capers one expects from even the tamest Joker stories (although the tamest ones would have left his henchmen unconscious and arrested, not coldly executed), the true introduction of the character begins with the horrific disappearing-pencil trick and never lets up for a second afterwards. There is no remorse, there is no reason. There is no truth to anything he says and yet everything he says is true. He doesn't simply exist outside of the lines, he exists outside of the coloring book, and from his vantage point everything he sees is only waiting for whatever crayons he decides to use. Why must the sky be blue? Why must the grass be green? Why so serious?
We do not get, as in other Joker origins, the idea that Batman inadvertently created his nemesis both by causing the accident that drove him mad and by being such an outrageous force for good that it could only be matched by an equally outrageous force of evil. The Joker that Nolan gives seems more like something that was perhaps bound to happen anyway but accelerated its own emergence upon realization that the scales needed a counterweight. He is mad, and acutely aware of the facets of his madness...through that prism he understands that the roaring nightmare whisper of Batman's voice is only the facsimile of primal, natural force--whereas his own insanity is the real thing. He is, as he explains later to Dent, a dog chasing cars...he does what he does because he is compelled to and lacks whatever voice tells most of us to not do so.
The crux of his strategy against Batman is to make him turn off his own such voice. He doesn't, in fact, want the Batman dead, but he does want him destroyed.
And whom the gods would destroy, they first make mad.
The Joker both wins and loses, in the end--he fails to destroy Batman, but he effectively destroys Bruce Wayne, checkmating him into shutting down whatever avenue there was back to a normal life. The Joker forces Batman, as he forces everybody else he encounters, to make a choice and then live or die with the consequences of that choice...Batman could not kill the Joker, and so they are damned to dance forever in the stalemate, like two kings left alone on the board hopping back and forth along single squares, neither careless enough to get within striking distance of the other.
If Batman had killed the Joker when he first had the chance, Dent would never have been transformed, Rachel would not have died, and this chapter could have ended with Batman removing the suit and leaving care of the city to its worthy District Attorney. The choice that the Joker effectively foists upon his foe is that between the hero or the human being, and by choosing to abide by his principle of not killing, Batman emerges as the primary persona, and Wayne the alter ego--now and forever.
The Dark Knight, as a film, is about what one is forced to sacrifice in the pursuit of a better world, and about those who laugh maniacally at you, giving you reasons why you're insane to even try.
Nolan's protagonist is, in the end, a hero not because he fights villains, but because he considers all that he has to give up in order to be a hero, and then chooses to be that hero anyway.
Yes, Batman replies. You're right. I probably am insane.
Let's see what good can come of that.
1The Prestige was by far my favorite film of 2006, a film I found so deeply enervating that it directly inspired me to write Contraption. Thus far, The Dark Knight is tied at first with Wall E for 2008.