It is enough to make one wonder whether or not Ledger's death was do to the his inside-view obtained by method-acting. Becoming Batman's complete opposite could have been enough to ruin any man.
One haunting catch-phrase seems to echo from this character's very being:
As the Joker makes funnies about murder and burns the dreams of men, he resonates the idea of a complete comedy. Upon confronting Batman, the most prominent words are, "Why so serious?"
The Joker wants Batman to join his side. He craves the Bat to see the punchline and make some sort of hilarious comeback. Whether or not the Dark Knight understands the "joke" does not really seem to matter because in this joke's telling innocents suffer. Even though these people might not really mean anything to the Joker or personally to Batman, they mean something to someone and their lives are not worth losing. Batman knows that this is nothing worth laughing about.
The Joker flails about willy-nilly causing destruction and grief because he seems to be the only one on the inside of his joke, Batman retains his self-control. Even when the Joker tries to push the Bat over the edge and force him to show some sort of emotion and have some sort of dark humor by killing the Joker, Batman refuses. There are lines that he will not cross.
We are to have this sort of self-control.
One may say that in the Bible there are Laments, David dances (seemingly uncontrolled), Solomon lusts after a woman, Jesus tips the tables of the temple, and many more righteous people seem to remain righteous while also being uncontrolled. They have a point. Perhaps the wisdom of Solomon inspired by the Holy Spirit is right in saying that there is "A time for Everything."
But, a truly righteous man would not go against the statutes and commands of God.
Like Christ, we have the freedom of emotion but we also have self-control to remember to do what is right.
We can drink without getting drunk, we can speak without cursing, and we can love without immorality.
We can see the comedy of the joke, but if the joke is wrong, corrupt, wretched, and sinful we can choose not to laugh.
Perhaps if Ledger would have known this he would still be with us.
"We have concluded that the manner of death is... from the abuse of prescription medications."
"A man without self-control is like a city broken into and left without walls." Proverbs 25:28.
This has been part of the Dark Knight Series