Madness is the emergency exit. You can just step outside, and close the door on all those dreadful things that happened. You can lock them away…forever." The Joker
...My point is, I went crazy. When I saw what a black, awful joke the world was. I went crazy as a coot! I admit it! Why can't you?
It's all a joke! Everything anybody ever valued or struggled for... it's all a monstrous, demented gag! So why can't you see the funny side? Why aren't you laughing?
All it takes is one bad day to reduce the sanest man alive to lunacy. That's how far the world is from where I am. Just one bad day." The Joker - The Killing Joke