The History Channel examines the mental landscape of Batman with select interviews from writers and various experts in the psychology field. Insight is given on the motivating forces that drive the Joker, Catwoman, and the other villains of Gotham City.
I always felt Batman had a great curiosity about the Joker because he hadn’t ever come across someone like him before. This is another character like himself that will not compromise whatsoever. The Joker wants to see that everybody has a price, that nobody is pure and that even Batman can be bought or leveraged in such a way that he would compromise his principles.
The Joker has an agenda of a chaos, he’s a unique villain in that he is not necessarily after money or power, or any of those traditional things, that’s really the hardest kind of evil to fight because you can’t bargain with it.
-Danny Fingeroth, author Superman on the Couch
Batman says philosophically we can acknowledge an imperfect world, we can acknowledge that we have to step outside of social norms but that doesn’t make the social norms meaningless. The Joker says the presence of random injustice means that there is no justice. The fact that innocents can be destroyed means that there is no innocence. The Joker isn’t just threatening him physically, he’s threatening the premise of Batman’s existence, that’s why it’s such an epic discussion that they’re having and it’s played out physically, it’s played out in punches and gun fights.
-Benjamin R. Karney, Professor of Psychology, UCLA