The aggregate composition and structure of nations, states, and their constituent groups was the subject of sophisticated analysis and argument long before the rise of statistics, demography, and the modern state. This chapter outlines how, from Aristotle to the late eighteenth century, classical conceptions of the state and its memberships provided a subtle and ready basis for political thought about the role and importance of human numbers. The chapter explains why the role of fertility in population growth was not a priority in this classical model, and how the modern concept of population, based on statistics of the nation-state, led to a re-evaluation of the role of reproduction. Put simply, classical approaches were concerned with the processes that form and sustain groups in society, which involve much more than reproduction. The population of a state was composed of a hierarchy of memberships and the networks that sustained or divided them. The interest in what makes for stable polities led, in the seventeenth century, to development of quantitative measures within the classical model. By the early nineteenth century, analysis of quantitative relationships without reference to the history and formation of groups became widely accepted, giving fertility a new significance.