What’s the lesson for avoiding this for a more serious-sounding theory? I typically restrict causal judgments to experimental manipulations. But maybe that is too restrictive? The only other thing I can think of is if a researcher knew so much about their subject that they could boil down the possible causes to a handful. Then maybe multiple regression with controls could help sort between them. If so, the issue with Harry Potter is that it’s one of millions of similar cultural influences that are all hopelessly tangled and so can’t be untangled with observational methods.