Children often play games where they try to recognize “which one of these things is not like the other.” For example, they know triangles of various dimensions are similar to one another, while a square is something different. As adults, categorization occurs just as frequently. Stories about Wimbledon are in the sports section of the newspaper, apples and cucumbers can be found in the produce section of a store, and according to taxonomists, platypuses are mammals.

Of course, classification is not always so easy: wars have been fought over what constitutes “the good life,” and “I know it when I see it” is one amusing, yet unhelpful, judicial standard for pornography. Sometimes vagaries in definition and measurement are acceptable; however, if one is interested in understanding what constitutes a community and in observing the political effects of what people perceive to be their community boundaries, then more clarity and precision are needed.

To examine how people imagine their communities and the extent to which the psychological boundaries that result from these images affect political attitudes, we need to know how to recognize a community when we see it; in other words, we need good measures of “community.” Good measures ought to fit the conceptualization laid out in Chapter 1. They would first provide information about the commonality that people believe they share with others in their community – the quality or feature that connects these individuals, such as feelings of similarity, closeness, proximity, or sympathy.