Political Arithmetick. — Raising Leviathan. The brutish world of Thomas Hobbes. — Lesser Forces. The mechanical philosophy of matter. — The Law of Large Numbers. Regularities from randomness. — The Grand Ah-Whoom. Why some things happen all at once. — On Growth and Form. The emergence of shape and organization. — The March of Reason. Chance and necessity in collective motion. — On the road. The inexorable dynamics of traffic. — Rhythms of the Marketplace. The shaky hidden hand of economics. — Agents of Fortune. Why interaction matters to the economy. — Uncommon Proportions. Critical states and the power of the straight line. — The Work of Many Hands. The growth of firms. — Join the Club. Alliances in business and politics. — Multitudes in the Valley of Decisión. Collective influence and social change. — The Colonization of Culture. Globalization, diversity and synthetic societies. — Small Worlds. Networks that bring us together. — Weaving the Web. The shape of cyberspace. — Order in Eden. Learning to cooperate. — Pavlov's Victory. Is reciprocity good for us? — Towards Utopia? Heaven, hell and social planning. — Epilogue. Curtain call.

Are there "natural laws" that govern the ways in which humans behave and organize themselves, just as there are physical laws that govern the motions of atoms and planets? Unlikely as it may seem, such laws now seem to be emerging from attempts to bring the tools and concepts of physics into the social sciences. These new discoveries are part of an old tradition. In the seventeenth century the philosopher Thomas Hobbes, dismayed by the impending civil war in England, decided that he would work out what kind of government was needed for a stable society. His solution sparked a new way of thinking about human behavior in looking for the "scientific" rules of society. Adam Smith, Immanuel Kant, Auguste Comte, and John Stuart Mill pursued this idea from different political perspectives. But these philosophers lacked the tools that modern physics can now bring to bear on the matter. Philip Ball shows how, by using these tools, we can understand many aspects of mass human behavior. Once we recognize that we do not make most of our decisions in isolation but are affected by what others decide, we can start to discern a surprising and perhaps even disturbing predictability in our laws, institutions, and customs.