The paper by Gurova takes issue with the claim of Meehl that ‘understanding makes it normal’ is a fallacy in diagnostic reasoning [1,2]. Her paper prompts the more general question of appropriate methods for testing whether a specific way of reasoning in making a clinical diagnosis is fallacious. So prompted, I will compare the methods that the Gurova paper deploys with some of requirements for testing whether a particular way of reasoning is fallacious. It should become clear in this comparison that the dictum ‘understanding it makes it normal’ per se is insufficient to proclaim whether reasoning by it is fallacious.