One of mankind's most enduring questions is the legitimate scope of state power: how far and in what ways may the government meddle with people's lives? Where lies the line that government ought not cross? For more than three centuries, the western world has answered these questions with with institutions and practices that collectively have come to be known as liberal democracy. Though deeply rooted, liberalism has stirred critical attacks from both the left and the right and it has never wholly won the day. During the past 40 years, many of liberalism's most distinguished defenders have...