I report a study that investigated ideas about critical thinking across three disciplines: Philosophy, History and Literary Studies. The findings point to a diversity of understandings and practices, ones that suggest the limitations of a more generic approach. I argue that a more useful conception of critical thinking is as a form of "metacritique"--where the essential quality to be encouraged in students is a flexibility of thought and the ability to negotiate a range of different critical modes. (Contains 3 figures.)