Every country, every subnational government, and every electoral district has a designated population. Some are large and some are small. Yet in existing empirical work, population is usually treated as a background factor. In this preface, the present book’s focus on scale effects is outlined and motivated. By means of a brief comparison of the illustrative examples of the United States and Malta, it is argued that population size influences politics in a variety of ways. Since it is difficult to reach a determination about the role of scale for particular cases, this book examines scale effects at a general level, focusing on universal rather than particular causal effects. While a venerable tradition of political thought and scholarship suggests that scale is an obstacle to democracy and good governance, our findings suggest that scale has both positive and negative effects. The final section of the preface lays out the structure of this book, highlighting the themes discussed in each of the following chapters.