How we cite our quotes: All quotations are from The Dark Knight.
Quote #4
BRUCE WAYNE: I knew the mob wouldn't go down without a fight, but this is different. They crossed a line.
That line can seem pretty arbitrary here, but it also indicates that the Joker is playing on another level. He's not simply seeking to evade justice, like the gangsters are. He wants to destroy the very notion that justice exists.
Quote #5
JAMES GORDON JR.: Did Batman save you Daddy?
GORDON: Actually this time, I saved him.
Batman's not the only one doing right and administering justice out there. Gordon's laying it all on the line too, and sometimes he's the one who gets to run in and save the day.
Quote #6
GORDON: No matches on prints, DNA, dental. Clothing is custom, no labels. Nothing in his pockets but knives and lint. No name, no other alias.
The Joker's lack of a past suggests that he exists outside the system completely. Therefore, its notions of justice don't apply to him, and—more frighteningly—that he has the freedom to bring it all down if he wants.