In this chapter Peter Biller revisits his arguments in The Measure of Multitude (2000) about the questions that twelfth- and thirteenth-century scholars and their students asked about the multitude. Their discussions were informed by the Bible and the writings of Aristotle then available and set within an age of extraordinary population increase, a shift in civic structures and political entities, and an increasing awareness of the relative, diminished size of Latin Christendom in relation to the rest of the world. Next the chapter considers how this body of thought continued after 1300, as new universities were founded and increasing numbers of literature men settled in towns and cities across Europe. Everything changed with the catastrophic mortalities of the Black Death from 1347. Through the thirteenth century, the avoidance of offspring had become of increasing concern, while after the Black Death concerns shifted to a scarcity of people, prevalence of marriage, and numbers of children. Procreation within marriage was encouraged for the common good. The ways that ordinary people experienced the multitude can be glimpsed through prescriptive pastoral writings and observations about, for instance, numbers of regulated midwives, lists of marriages and deaths and relative numbers of births.