It is a common critique of John Milton’s Paradise Lost that Satan is the unintended hero. Sympathetic, eloquent, and fascinating, the most evil being in all of time became, in the hands of a master poet, a tragic figure. Because of his portrayal of Satan in the work, William Blake said of Milton that he was, “of the Devil’s party without knowing it.” A well told story can turn even the most wicked character into someone with whom we might wish to empathize—whether the author intended it that way or not. As it is with Milton’s Satan, so it seems to be with Joaquin Phoenix’s Joker.
Depicting villains and offering honest examinations of sins are crucial functions of telling good and moral stories. As G. K. Chesterton wrote on the topic, “If the characters are not wicked, the book is.” Wickedness is not benign, though, so the way in which it finds expression in our stories—and in the characters in our stories—is something to which we should always pay close attention, because our stories work also on us.
https://christandpopculture.com/dancing-with-miltons-satan-the-joker-and-a-fascination-with-evil/