Though you have to take valium once you're done
To further elaborate. Joker claiming to be an 'agent of chaos'. To me, that rings true. Chaos is Joker's main foundation for the world he wants to create. He's very much aware of his actions in TDK. Without rules of right and wrong, the sheer rule of living under strict authority, the world would descend into chaos.
Joker forces several people to do things they don't want to do in TDK. He forces others to kill one another for survival. So in Joker's world, if you're like him, you can live in it. Because once he sees people giving in to his chaos image and 'screw all rules' world, he thinks he's winning. Joker wants and needs to spread his ideals unto everyone. He cant understand why people are living in the social norm, and wants to change how we operate as a decent society.
That's the case of mentally ill people though, they don't see the wrong in what they're doing.
His wife. As we know from TKJ. Joker conjures things up in his mind at anything he sees. He has a vivid imagination, and can create a story in his mind that he believes is the truth, until another 'truth' enters it. I know that there is a psychological disorder that can actually cause that, but I cant be precise at what it is exactly. Some form of psychosis I think. Its living in his own fantasy world, so it might be schizophrenia.
There is nothing to suggest that Joker wasn't married, but I'm guessing it was just trying to tell Rachel a story about his scars. Using a woman he loved as an example to get the proper effect he wanted on her. Chilling
Most interesting, is why he keeps telling stories about his scars. To me, that is probably what traumatised him the most, as he keeps talking about them. Licking his lips, to get them constantly noticed? It seems like a very subtle sign of him actually crying out for help, even without him taking much notice to it.
He keeps talking about the scars, wanting them to get attention. Almost as if trying to get others to listen to his troubles. Cause he always tells a pretty pitiful tale about abuse, that others forced on to him and what he did to himself. So his personality trait of forcing others to do things to one another could stem from that.
I very much believe he scarred himself, but something (not physically someone) down the line forced him into doing it. Obviously his unbalanced mind probably conjured up some fantasy that it was somebody else. His father inflicted them on him, and he did for his wife. So to him, its not really his fault. Always blaming other people, never themselves. Common amongst people that.
Could've been caused by memories of his past coupled together by his philosophical views and delusions.
I honestly think before becoming the Joker he nearly killed himself. Most definitely by cutting his mouth open. To do that would have some significance to him. So perhaps in becoming the Joker, he tested himself in life or death, not caring if he would live or die. Thus cutting his mouth to finalize his new life.
"I believe whatever doesn't kill you, simply makes you stranger"
Batman. To Joker, Batman is his inspiration, his reason to live. In TDK, Joker saw Batman and found his purpose in life. Like in Lovers And Madmen, he finds somebody like him. Batman is his muse. Like in TDK too.
In the movie, he was obviously inspired by Batman. His plot, it always involved in the two of them coming face-to-face, exactly what Joker was hoping for, for so long. Like in the comics, Joker has that connection to Batman. No different in TDK. Even though its different ways, it was still the creator and the creation. So prior to the events of the movie, he must have seen Batman and thought to himself
"That is how we should be".