When I began graduate school in 1977, the history of science was mainly about theories. I had been drawn to the field by the work of Thomas Kuhn, whose famous book The Structure of Scientific Revolutions gave us such concepts as “paradigm shift.” By then, history of science had become a recognized field of historical investigation. Serious historians were expected to leave textbooks behind and examine the real work of science, including its concrete aims and resources. I worked on my dissertation and first book in this spirit. My topic was the origin of basic statistical tools and understandings articulated by mathematicians and natural scientists in the nineteenth century. This led me to social numbers by way of the Belgian astronomer and social statistician Adolphe Quetelet. He was part of my original plan, but I had not understood that the work would lead me into moral and administrative discussion stimulated by political and industrial revolutions. New ideas and understandings remained central, but I now linked them to bureaucratic tallies and debates tied to prison reform, trade policy, public health, and poor law administration.Nowadays, my colleagues often speak of a material turn, meaning that there is a new focus in the field of history of science on the stuff that scientists work with such as instruments, reagents, biological collections, filing cabinets, and calculating machines. I have welcomed this move, not least because a focus on material reality opens a still wider perspective on science and its technologies, calling attention to concrete circumstances of labor and administration that extend beyond these now-fetishized material objects. In my book on asylums and heredity I have given close attention to admission registers, patient case books, census cards, and the diverse tabular arrangements by which the data were structured. In this sense, the statistics of madness may also be spoken of as “materialized.” But it is more than that. This research required close attention to the roles of numbers and statistics in medical administration and public persuasion. Data provided a basis for accountability and lent credence to hopes for a reasoned perspective on madness. Such deeply mundane tools can play a fundamental role in ordering the world.In short, this book embodies an emerging scholarly focus on mundane realities that extend well beyond basic science. More specifically, the book got its start after I was invited to write a paper for an edited volume on the multifarious sites and sources of heredity. This request inspired me to look into the statistician Karl Pearson’s sources for statistical data on human heredity. It was a lucky choice; many in-principle good ideas lead to dead ends but this one opened up wonderfully.