  It seems that awareness of disagreement can, at least in many cases, supply one with a powerful reason to think that one’s belief is false. When you learned that your sister thought the piano had been in the den instead of the living room, you acquired a good reason to think it really wasn’t in the living room, as you know full well that your sister is a generally intelligent individual, has the appropriate background experience (she lived in the house too), and is about as honest, forthright, and good at remembering events from childhood as you are. If, in the face of all this, you stick with your belief that the piano was in the living room, will your retaining that belief be reasonable?