As the U.S. Supreme Court has entered its tenth term with John G. Roberts Jr. as chief justice, it is an apt time to take stock of its work. Uncertain Justice by Laurence Tribe and Joshua Matz provides a superb opportunity to do so. At once accessible and erudite, the book provides an introduction to the high court's key decisions for general readers, while at the same time offering thoughtful analysis that will interest lawyers and Court watchers. Tribe, a Harvard law professor, is one of the nation's foremost constitutional scholars and Supreme Court advocates; Matz is his former student, now clerking for Justice Anthony M. Kennedy. Throughout the book, the authors emphasize the principled commitments that drive the justices' conclusions. Just "account[ing] for what the Constitution requires," they explain, "may seem straightforward enough," but "... a lot of hard cases are hard because the Constitution gives no simple rule of decision for the cases in which one [constitutional value] is truly at odds with another." Moreover, the authors say, although "[t]he nine justices also practice their own form of politics ..." it is "[n]ot the low and occasionally demoralizing politics of our endless partisan struggle but a high politics of constitutional principle, in which they compete to define the framework of our fundamental law." In thematically organized chapters addressing hot-button topics such as equal protection, campaign finance, and executive power, the authors push readers to move past bumper-sticker reactions and recognize the complexity of the legal issues involved. They also highlight areas of law such as privacy and unconstitutional conditions in which the Court's usual coalitions have broken apart, defying efforts "to reduce the justices' views to political caricature." For a public inclined to view law as simply the continuation of partisan politics by other means, this careful exposition of the justices' opinions is a useful corrective. The book's overall theme regarding the Court, however, is uncertainty (as reflected in its title). Back in 2005, Tribe discontinued work on the third edition of his celebrated constitutional law treatise because he believed the material defied effective synthesis. "[W]e find ourselves," he wrote then, "at a juncture where profound fault lines have become evident at the very foundations of the enterprise." Surveying the work of the current Court, Tribe and Matz find that deep uncertainty remains endemic. They write: "In some important domains of constitutional law, a majority of the Roberts Court stands on the brink of revolution yet seems profoundly uncertain about whether and how to proceed. In other domains, it has already initiated major changes whose long-term effects are clouded in mystery." One key example is the Court's blockbuster decision in 2012 on the constitutionality of the Affordable Care Act. (Nat'l Fed'n of Indep. Bus. v. Sebelius, 132 S. Ct 2566 (2012).) Although Chief Justice Roberts saved the Affordable Care Act by agreeing that "shared responsibility payments" for individuals without insurance were a valid federal tax, he voted with the Court's conservatives to recognize limits on congressional power to regulate interstate commerce. Uncertain Justice deftly explains how this Commerce Clause holding drew strength from deep-seated concerns about economic liberty and federal power, yet few commentators at the time predicted that the Court would embrace it. Each "strand" of the Court's analysis - economic liberty and federalism - might well augur "a more active role for the Court in matters once left mainly to democracy," the authors conclude. Time will tell. The Court will indeed revisit the Affordable Care Act this term; see King v. Burwell (pending as No. 14-114).) Tribe and Matz rightly note that such uncertainty is inherent in the Court's role: "[S]ince the Court makes new law in many contested domains of American life, even the justices cannot know with any great certainty how the opinions they fashion will shape the future of the Republic." Nevertheless, personnel matters a lot too. Whether seeds planted in decisions such as the Affordable Care Act case grow into robust branches of doctrine or wither into forgotten anomalies may well depend on which way the Court's ideological balance tips with future appointees. Moreover, there is another level of uncertainty that attends the Court's work. Some central issues today - questions about military detention and surveillance, for example, or about privacy and intellectual property amid dizzying technological changes - were not readily foreseeable even when President Clinton's two appointees (Justices Stephen G. Breyer and Ruth Bader Ginsburg) took their seats, let alone when Justice Kennedy was confirmed in 1988. The key fault lines of the future may or may not be those that consume our attention today. Zachary Price is a visiting assistant law professor at UC Hastings in San Francisco. He clerked for Justice Anthony Kennedy in 2005-06.