Walter Lippmann might be the defining example of a public intellectual. He profoundly influenced public and political debate in America during the twentieth century. A prolific journalist and columnist, he also published ten major books and even more edited collections and compilations. The best of these were thought-provoking disquisitions on public opinion, communications, politics, international relations, and the ways in which liberal thought has developed in the United States. His was, argues Tom Arnold-Forster, ‘a six-decade commentary on the vicissitudes of politics’.