What is the theme in Arkham Asylum by Grant Morrison?

The central theme of Arkham Asylum is madness and human psychology. The story divides the human mind into two impulses: a rational impulse and a chaotic impulse; the good and the evil; the ego and the id. Two-Face embodies this dichotomy. He is physically and mentally divided into good and evil. Batman and the Joker together represent the two sides of the mind. Batman is the controlled, rational ego, while the Joker is the chaotic, irrational id. Batman struggles against falling into the Joker's mad world throughout the story, while Arkham fights a similar struggle within himself.