In this comprehensive study of the modern American public intellectual - that individual who speaks to the public on issues of political or ideological moment - Richard Posner charts the decline of a venerable institution that included worthies from Socrates to John Dewey. With the rapid growth of the media in recent years, highly visible forums for discussion have multiplied, while greater academic specialization has yielded a growing number of narrowly trained scholars. Posner tracks these two trends to their inevitable intersection: a proliferation of modern academics commenting on topics outside their ken. The resulting scene - one of off-the-cuff pronouncements, erroneous predictions, and ignorant policy proposals - compares poorly with the performance of earlier public intellectuals, largely nonacademics whose erudition and breadth of knowledge were well suited to public discourse. Leveling a balanced attack on liberal and conservative pundits alike, Posner describes the styles and genres, constraints and incentives, of the activity of public intellectuals. He identifies a market for this activity - one with recognizable patterns and conventions but an absence of quality controls. He also offers modest proposals for improving the performance of this market - and the quality of public discussion in America today.