Book excerpt: Robert Dahl's Preface helped launch democratic theory fifty years ago as a new area of study in political science, and it remains the standard introduction to the field. Exploring problems that had been left unsolved by traditional thought on democracy, Dahl here examines two influential models--the Madisonian, which represents prevailing American doctrine, and its recurring challenger, populist theory--arguing that they do not accurately portray how modern democracies operate. He then constructs a model more consistent with how contemporary democracies actually function, and, in doing so, develops some original views of popular sovereignty and the American constitutional system.