How we cite our quotes: All quotations are from The Dark Knight.
Quote #4
ALFRED: Some men aren't looking for anything logical. They can't be bought, bullied, reasoned or negotiated with. Some men just want to watch the world burn.
Rules can be imprisoning when you think of them as the only way to do things. Here Alfred points out that the Joker's so dangerous in part because Bruce is looking at him through a particular set of expectations… which are basically unspoken rules. Yeah, the Joker likes breaking those too.
Quote #5
BATMAN: I want the Joker.
MARONI: From one professional to another, if you're trying to scare somebody, pick another spot. From this height, the fall wouldn't kill me.
BATMAN: I'm counting on it.
This is a great straight-up look at how the Batman adheres to some rules (don't kill anyone) while cheerfully breaking others (don't menace Mafia bosses if you're not a cop).
Quote #6
THE JOKER: See, their morals, their code... it's a bad joke. Dropped at the first sign of trouble. They're only as good as the world allows them to be. I'll show you, when the chips are down, these...these civilized people? They'll eat each other. See, I'm not a monster, I'm just ahead of the curve.
Here's the really scary part: the Joker isn't just interested in flaunting the rules of civilization: he wants civilization to give them up too. Even worse, he thinks it's inevitable, and accordingly, he's going to make it happen. Sleep tight, kids.