How to Create Catharsis
Assuming that the theory of catharsis is correct, obviously the best way to achieve it is to create strong negative emotions in your stories. Ideally, of course, you would do this through tragedy, since that was believed to be the most cathartic art form in ancient Greece.
Writing tragedy is difficult, in part because we in the modern world have so few examples of it to serve as models. There are a couple of key elements, though, that need to be present in order for a story to count as tragedy in the classical sense. First, of course, it needs a sad ending. No matter how bad things get, it isn’t a tragedy if things get better in the end. Your hero needs to be ultimately destroyed by the story, and the forces of evil, chaos, etc., must prevail.
Second, the hero needs to be brought down by something human – something that exists in all of us. Think, for example of a tragic superhero story. In such a story, the superhero would be strong enough to defeat monsters and super-villains of all kinds, but would ultimately succumb to a human failing like selfishness, overconfidence, loneliness, or depression.
When to Use Catharsis
Catharsis is a theory intended to explain why human beings enjoy negative emotions in art. Thus, it applies primarily to drama, literature, art, and to some extent music. However, it’s entirely possible that the theory of catharsis could also explain the value of negative emotions in non-fiction writing as well.
If you’re writing a history paper about the Holocaust, for example, it might be true that you are helping your reader achieve catharsis by evoking the negative emotions associated with those events. However, this shouldn’t affect the way you write such a paper: your goal in a paper is to be clear, informative, even-handed, and above all persuasive; it isn’t to create catharsis. If you set out with the goal of creating catharsis, you may very well end up writing a paper that’s too emotional to be effective as a formal essay.