Rules order almost every aspect of our lives. They set our work hours, dictate how we drive and set the table, tell us whether to offer an extended hand or cheek in greeting, and organize the rites of life, from birth through death. We may chafe under the rules we have, and yearn for ones we don't, yet no culture could do without them. In Rules, historian Lorraine Daston traces their development in the Western tradition and shows how rules have evolved from ancient to modern times. Drawing on a rich trove of examples, including legal treatises, cookbooks, military manuals, traffic regulations, and game handbooks, Daston demonstrates that while the content of rules is dazzlingly diverse, the forms that they take are surprisingly few and long-lived. Daston uncovers three enduring kinds of rules: the algorithms that calculate and measure, the laws that govern, and the models that teach. She illustrates how rules can change--how supple rules stiffen, or vice versa, and how once bothersome regulations become everyday norms. Rules have been devised for almost every imaginable activity and range from meticulous regulations to the laws of nature. Daston probes beneath this variety to investigate when rules work and when they don't, and why some philosophical problems about rules are as ancient as philosophy itself while others are as modern as calculating machines.