This book is an impressive survey of our collective and cumulative understanding of the evolution of digital communication systems and the Internet. While the information societies of the twenty-first century will develop ever more sophisticated technologies, the Internet is now a familiar and pervasive part of the world in which we live, work, and communicate. As such it is important to take stock of some fundamental questions--whether, for example, it contributes to progress, social cohesion, democracy, and growth--and at the same time to review the rich and varied theories and perspectives developed by thinkers in a range of disciplines over the last fifty years or more.