Models of idealistic societies pervade the history of political thought from ancient times to the present. How can these models contribute to our thinking about political life in our non-ideal world? Not, as many political theorists have hoped, by performing a normative function -- by giving us reasons to accept particular political principles for the purpose of regulating our thought and behavior. Even still, idealistic models can sharpen our thinking about politics by performing a conceptual function -- by helping us (...) clarify and interpret the concepts we use to describe and evaluate political behavior and institutions. These insights point to a more incisive and judicious approach to political inquiry, in which explanatory and normative modes of thought are tightly intertwined. (The manuscript is under review. I have uploaded the table of contents, chapters 1 and 2, and the bibliography. Chapter summaries are available from my website.). (shrink)