Agree to disagree.

• Author: Bazelon, Emily
• Position: Book Review

CASS R. SUNSTEIN IS A PRIME mover behind the intensifying Senate fight over President Bush's nominees to the federal appeals courts. Sunstein has counseled the Democrats on the Judiciary Committee to stand up to the Republicans, whose "disciplined, carefully orchestrated and quite self-conscious effort has radically transformed the federal judiciary," he warned this spring in The American Prospect. "What was then in the center is now on the left," Sunstein writes in comparing the courts of 20 years ago with those of today. "What was then in the far right is now in the center; what was then on the left no longer exists."

Sunstein's forceful stance matters because he's a respected scholar (he teaches law at the University of Chicago) and because he's a restrained, thoughtful liberal (he clerked for Thurgood Marshall, but cites Sandra Day O'Connor's minimalist approach as a model). Ideology does affect the way judges vote in important cases, Sunstein has argued to senators who worry that it's unseemly to oppose a nominee simply for being too far to the right. Now he has done the research to prove his point and then some.

Most of Why Societies Need Dissent isn't about partisan politics. It's a survey of social science research about group conformity, aimed at showing why the pressures exerted by groups often lead to bad or ill-informed decision making. As a counterpoint, Sunstein demonstrates the value of naysayers, particularly those who offer new information along with wagging fingers. The book is written in the crisp, level tones of a lecture--the Oliver Wendell Holmes Lectures at Harvard Law School, to be exact, which Sunstein gave in February.

Still, Sunstein's concern about the Bush nominations explains the book's timing and its most original contribution: a study of the voting patterns of appellate judges. Along with two other researchers, David Schkade and Lisa M. Ellman, Sunstein looked at thousands of votes cast by these judges, who hear appeals in panels of three. As you might expect (unless you're a senator determined to stick your head in the sand), he and his colleagues found that in ideologically contested cases, Republican appointees tended to vote along more conservative lines and Democratic appointees tended to vote along more liberal ones. More strikingly, the judges were significantly influenced by the political affiliation of their co-panelists. For example, Democrats (to use Sunstein's shorthand for judges appointed by...