Much ink has been spilled already over Heath Ledger’s performance as the Joker, so I won’t add anything other than his statuette is already in the post. The Joker is psychotic, or at least he is intended to be. I have never dealt with a schizophrenic who was this well organized, and able to plan out an elaborate chess exchange to rival Anderssen’s ‘Immortal Game’, so the allusion of psychosis is bullshit. In reality he is quite sane, quite suicidal, but above all has come to an understanding about human nature. He commits some impressive homicides, but when his own hand is involved, you can see the boredom in his eyes. He only comes alive when he manipulates people into killing each other, which at times is all too easy. The killing is not a goal in itself, and he certainly is not interested in cash – he wishes to hold a mirror to everyone he sees, and convince the reflection that the better angels of our nature are a fabrication of our ego, the sort of thing to help us sleep at night. The way he sees it, he is only performing a public service, though one from which he derives great joy. In this way, his character resembles the corrupt police chief of Bertrand Tavernier’s Coup de Torchon – the murders are but the manifestations of human desires, and are all too easy to arrange. To thine own self be true, and so forth.
The Joker steps into a Gotham City on the verge of breaking the mafia with the help of Batman, who has applied a heavy hand to bring order. Disorder always pushes back, however, and the force required to do so unleashes a wave of terror that leaves the citizens, the cops, and the viewer reeling. The Joker has come to the realization that once you have no reason to hold back, anything is possible. With no fear of police, or Batman, or anything else, he can strike hard enough, and fast enough, to bring the panic to a critical mass, and achieve the chaos necessary to reveal true human character. Lock enough rats in a small enough cage, and they will eat one another to remain alive.
So how does one counter such an onslaught? Conventional police have no purpose here, so Batman must apply extraordinary rendition, torture, massive public surveillance, and war upon the police in order to apply justice. Though his character makes token gestures towards justifying his actions, and the nobility of sacrificing one’s moral code for the greater good, in the end the Joker wins in many different ways. Harvey Dent sings his tune, the people prepare to give in to this terrorist’s demands, and people are driven to commit murder with the greatest haste. Lastly, Batman – thick though he may be on the issue – is coming to realize that the humanity we have so grown to covet is but an artificial construct that we enjoy because it brings us comfort in our elevation above the animals. Deep down we are little more than animals with opposable thumbs (which come in handy with weaponry), and all it takes to reveal that aspect of ourselves is someone with the will to push us to that edge.
Another interesting parallel in the film is the dichotomy between the Joker and Batman, in that they must both survive or they both shall perish. Someone as dangerous as the Joker requires Batman as a sufficiently dangerous response, and justifies his existence, while Batman is what allowed the Joker to be unleashed in the first place. Without one, the other need not exist. Despite some overtures made by Bruce Wayne’s character toward retirement, he seems way too masochistic to consider quitting. He is clearly enjoying himself, though he lacks the Joker’s smile. (I'm putting this example here - SL gov needs the LTTE (War) to survive & the LTTE needs this gov (The War) to survive as well..dont they ?) The sworn enemies need each other to thrive, continually pushing against each other as they consolidate their power, as any conventional definitions of good and evil are left behind in the sandbox with the rest of the toys.