 Belief states are important because they are involved in explaining, predicting, and rationalizing behavior. Perry provided a host of memorable cases that make this point. Here's one. Consider two people who both utter to themselves the sentence ‘I am being attacked by a bear’. All other things being equal, both people will act in similar ways. There is a common explanation of their behaviors only in terms of their shared belief states, as they apprehend distinct propositions, each believing a proposition about himself. Furthermore, it is crucial to how our agents act that they grasp the relevant singular proposition in a first-person way and not, say, as one would if one saw one's own reflection in a mirror with the reflection of a bear sneaking up without realizing that the person being seen is oneself. So, explanation, prediction, and rationalization are all sensitive to belief states. To quote Perry on this point: