Public Intellectuals: A Study of Decline, by Richard A. Posner, Cambridge, Mass.: Harvard University Press, 2001. 408 pp. FEW WILL DENY that Judge Richard A. Posner is a person of immense influence: as a judge in the Seventh Circuit Court of Appeals; as an author of over thirty books and hundreds of articles on a variety of subjects; as a public intellectual much in demand as a public speaker; as a legal scholar more frequently cited in scholarly publications than even the legendary Oliver Wendell Holmes. Quite obviously when Judge Posner speaks, or writes, people will pay attention. They do so not only to see what they can learn from him but also to see where and how they can find him vulnerable. He is that kind of public intellectual--combative and inviting challenges to his pronouncements.