As legal affairs editor for The New Republic, Jeffrey Rosen has established himself as a deft, non-polemical Supreme Court analyst. Now the George Washington University law professor extends his analysis to book length and his coverage to over two centuries of the Court’s activities. The result is a thoughtful, thought-provoking, and only occasionally textbookish study of the Court’s history and its possible future under new Chief Justice John Roberts.

Rosen’s book is the companion volume to PBS’s four-hour Series “The Supreme Court,” to be broadcast January 31 and February 7, so it aims at the proverbial general reader. Ingeniously, it tells the Court’s entire history by setting up four pairs of men, each pair including an “ideologue” and a “pragmatist.” Rosen’s argument: “A pragmatic disposition, a degree of humility and common sense, and the ability to interact well in groups…have proved over time to be more important qualities than academic brilliance or rigid philosophical consistency in determining a justice’s long-term influence.”

The first pair is familiar: Thomas Jefferson (the only non-Justice on the list) and Chief Justice John Marshall. While Jefferson sat on his Monticello mountaintop and advocated strict construction, state’s rights, and even nullification, Marshall boarded with the other justices, plied them with Madeira and wit, and for 35 years produced decision after decision (Marbury v. Madison, McCulloch v. Maryland, and so on) that legitimized the power of the federal government and the Court itself.

Rosen’s other “ideologues”—Oliver Wendell Holmes, Jr., William O. Douglas, and now Antonin Scalia—also have been loners. By contrast, John Marshall Harlan, the “pragmatist” paired with Holmes, “was an emotionalist, a moralist, a Republican proselytizer, and something of a ham, but he understood and shared the vision of the framers of the Reconstruction amendments and sought to preserve that vision from the assaults of increasingly illiberal local legislative majorities,” most famously in his 1896 dissent in Plessy v. Ferguson that foreshadowed Brown v. Board of Education.

Like Jefferson and Holmes, Douglas was brilliant. But his political ambitions and personal peccadilloes made him much less effective in the mid-20th century than Hugo Black was. And Antonin Scalia, phrasemaker and headline-seeker, has had far less influence than amiable, fair-minded William Rehnquist.

The good news, according to Rosen, is that pragmatists’ respect for precedent and concern for the Court’s credibility act as moderating influences and keep the Court from skidding toward political extremes. He thinks Chief Justice Roberts may have “many of the personal gifts and talents of the most successful justices,” and the number of unanimous decisions that his Court has produced seems to bear him out.

Then again, Rosen says, “as the public demands more details about behind-the scenes drama on the Court” and the justices become more public figures, consensus-building may be harder than ever. Cases such as the Seattle/St. Louis school desegregation cases have “5-4” written all over them and may make the indecisive Anthony Kennedy, neither “pragmatist” nor “ideologue,” the justice who matters most. We shall see.