[PotatoPancakes]

> The “discursive hygiene” picture of fallacy theory sees fallacies as mistakes that a good arguer will avoid. Indeed, armed with a new toolbox of Latin names for fallacies, eager students all too often delight in spotting fallacies in the wild, shouting out their Latin names (ad hominem!; secundum quid!) as if they were magic spells. This is what Scott Aikin and John Casey, in their delightful book Straw Man Arguments, call the Harry Potter fallacy: the “troublesome practice of invoking fallacy names in place of substantive discussion”. However, they note another, less wholesome reason why some may be interested in fallacy theory. If one’s aim is not so much discovering the truth as winning an argument at all costs, fallacy theory can provide a training in the dark arts of closing down a discussion prematurely, leaving the impression that it has been won.

TL;DR: the Harry Potter fallacy is thinking that shouting out a named fallacy (e.g. "That's an ad hominem!") makes you instantly win a debate, as though you were casting a magic spell.