Click on the following link to listen to (or read) a 2005 NPR interview with Frank Miller, writer of Batman: Year One: http://www.npr.org/templates/story/story.php?storyId=4704766
An interesting quote from the interview:
CONAN: To be both Bruce Wayne and the Batman, does one or both of them have to be crazy?
Mr. MILLER: Well, my own personal theory is that everybody's crazy, but I would say not really. And as a matter of fact, Batman and Bruce Wayne are both characters who believe in sanity and, you know, in a sane world, but they believe that it only makes sense when you force it to. So there's a touch of the fascist in them, and there's a--he saw all sense ripped out of his life when his parents were murdered in front of his eyes, and he has come back and said, `I'm going to make the world make sense.' That's Batman.