I want to be a good doctor for my patients. And the question of when to follow one's judgment and when to follow protocol is central to doing the job well--or to doing anything else that is hard. You want people to make sure to get the stupid stuff right. Yet you also want to leave room for craft and judgment and the ability to respond to unexpected difficulties that arise along the way. The value of checklists for simple problems seems self-evident. But can they help avert failure when to problems combine everything from the simple to the complex?