Originally Posted by BatLobsterRises
A goal or a philosophy is not the same thing as a motive. Ultimately Joker didn't have a motive, or if he did, we're not privy to it. Hence why he tells the multiple choice version of his origin.
"You didn't think I'd risk losing the battle for Gotham's soul in a fist fight with you. Noooo, you need an ace in the hole. Mine's Harvey"
"I'll show you, when the chips are down these civilized people, they'll eat each other"
Joker's philosophy is his motive. Just as Ra's philosophy about justice and balance was his motive.
His multiple choice origin story is the nod to the comics where Joker is so insane that he remembers his past differently.