TDK is an allegory for post 9/11 America.
Spoilerage? We'll make it white for those who haven't seen it:
We're all depending on people who are not pure-as-the-driven-snow, they have capabilities that sometimes go too far and we have to trust/hope that they won't utilize them. The Joker is terrorism, and his motivations are either mysterious and/or not worth the effort of investigating (let's leave religion out of this one, and I think we can). America itself == Harvey Dent (he even looks like Uncle Sam!). We need a symbol of goodness and right and even though that thing might not *actually* be good and right all the time and is corruptible, we take it as the symbol of good and right because, well, we need it.
...and something about the growing economic power of China fits in there too.
Highlight it to read.
Incredible. see it in IMAX if you can.