Interpret the "Dark Knight" scene where the Joker threatens to blow up the two ferries?

Question

One ferry is full of prisoners, the other full of civilians.

The Joker will allow the ferries to blow each other up, but after 15 minutes, if they haven't decided, he blows both of them up.

What does it say about Gotham's most-wanted scum-bags and the innocent, noble civilians?

Answer 1

That they're not how the Joker thought them to be, they cared about each other and would risk their lives for another Gotham member

Answer 2

Actually, this is a form of the "Prisoners Dilemma" a problem in game theory. It was originally framed by Merrill Flood and Melvin Dresher working at RAND in 1950.

In its "classical" form, the prisoner's dilemma (PD) is presented as follows:

Two suspects are arrested by the police. The police have insufficient evidence for a conviction, and, having separated both prisoners, visit each of them to offer the same deal. If one testifies ("defects") for the prosecution against the other and the other remains silent, the betrayer goes free and the silent accomplice receives the full 10-year sentence. If both remain silent, both prisoners are sentenced to only six months in jail for a minor charge. If each betrays the other, each receives a five-year sentence. Each prisoner must choose to betray the other or to remain silent. Each one is assured that the other would not know about the betrayal before the end of the investigation. How should the prisoners act?

With Batman, instead of prisoners, it is ships of captives, and if one betrays the other, the other dies, but if neither betrays, they both live.

The web site below gives a detailed explanation of the Dark Knight and Game Theory.

So what it says is that cooperation is more beneficial than detonation.

Answer 3

Although the Joker had already placed judgment on everyone of Gotham city and found them not worthy to live, the others (those on the ferries) could not bring themselves to that conclusion, even when their lives were at risk.  They were better people than the Joker thought they were.  

ADDED:  The Joker is trying to prove that people are selfish and worthless.  

Batman/Joker

Batman refuses to kill anyone intentionally.  He feels everyone is worth protecting, even the Joker while the Joker feels that everyone is worth destroying.  (The Joker must have had an absent, uncaring mother!)

Answer 4

In his exact words, the Joker says,

"Tonight you're all going to be a part of a social experiment.  Due to a bunch of diesel fuel and ammonium nitrate, I'm ready to blow you all sky high.  Anyone attempts to get off their boat, you all die!  Each of you has a remote, blow up the other boat.  At midnight, I blow you all up.  If, however, one of you decides to press the button, I'll let that boat live.  So who's it gonna be? Harvey Dent's most wanted scumbag collection?  Or the sweet, innocent civilians?  You choose!  Oh, and you might wanna decide quickly because the people on the other boat may not be so noble."

As far as the unstoppable force meeting an immovable object, Batman was the unstoppable force, ridding Gotham City of all of it's criminals.  he even had the mob running scared:

JOKER: I know why you guys choose to have your little group therapy sessions in broad daylight.  I know why you're afraid to go out at night.  The Batman.

The Joker was the immovable object: the only criminal that Batman couldn't get rid of.

BRUCE: Criminals aren't complicated, Alfred, we just need to figure out what he's after.

ALFRED: ...and this may even be a man you don't quite understand.  Some men aren't looking for anything logical, like money.  They can't be bought, bullied, negotiated or reasoned with.  Some men just want to watch the world burn.

As far as the Joker's goal, he was trying to prove that deep down everyone is at least a little bit like him, he also wanted to thwart Gotham City's restoration(REMEMBER: the city is trying to restore order after it was overrun by criminals).  His best chance at doing that, he realized, was by bringing down Harvey Dent.  If he showed the people of Gotham that they couldn't rely on elected leaders, they would lose hope in their city's government and think that the only way to get their city back was to follow in Batman's footsteps and fight criminals with their bare hands, breaking the law themselves, which would lead to an anarchist society:

BATMAN: This city just showed you that it's full of people ready to believe in good.

JOKER: Until their spirit breaks completely.  Until they get a good look at the REAL Harvey Dent, and all the heroic things he's done.  You didn't think I'd risk losing the battle for Gotham's soul in a fist fight with you, did you? No, you need an ace in the hole.  Mine's Harvey.

HOPE THIS HELPS!!

Answer 5

When the citizens and the cons decided not to blow each other up, it showed that gotham still had hope to become a better city. The Joker was trying to prove that, when chaos is introduced to a society, the population falls into anarchy. Joker is the unstoppable force because he societies always progressively move into anarchy, just like Rome, and Batman is the unmovable object because he refuses to be corrupted. Joker, at least in The Dark Knight, was trying to overthrown society and show that having plans is pointless.