Barack Obama is widely known as a former community organizer and as the author of The Audacity of Hope. These entries on his resume fit well with his repeated calls for change in American politics. But, for many years, Obama also taught constitutional law at the University of Chicago (where he was a colleague of mine). To understand what makes him so distinctive, and why American politics has never seen anyone quite like him before, we would do well to start with a little constitutional theory.

Some judges are minimalists; other judges are visionaries. In deciding constitutional cases, minimalists gravitate toward the least controversial grounds. They like consensus and favor incompletely theorized agreements--that is, agreements about how to settle a particular dispute in the midst of disagreement or uncertainty about the fundamental questions that underlie it. For example, they decide cases involving affirmative action and presidential power without reference to sweeping theories about equality and the Constitution's commander-in-chief clause. In the nation's history, Justice Felix Frankfurter was probably the Court's most influential minimalist. In the current era, Justices Ruth Bader Ginsburg and David Souter generally proceed as minimalists.

Not unlike the great conservative Edmund Burke, minimalists are fearful of those who are gripped by abstractions, simple ideologies, and large-scale theories. Minimalists tend to respect traditions, and they do not believe that long-standing practices should be altered lightly or without a careful analysis that includes many voices. Minimalists insist that their approach shows a kind of civic respect, because they seek to recognize--rather than to repudiate--the defining principles of ideologically diverse judges and citizens. In disputes over religious freedom, for example, they prefer results that can be accepted by believers and nonbelievers alike. Minimalists also defend their approach on pragmatic grounds. In their view, those who seek enduring change are not likely to succeed if they defy the deepest beliefs of large parts of the country. On occasion, minimalists are willing to think big and to endorse significant departures from the status quo--but they prefer to do so after accommodating, learning from, and bringing on board a variety of different perspectives. The Court's decisions banning sex discrimination emerged from a minimalist process, starting with small steps and culminating in larger ones that nearly all members of the Court, and much of the nation, were ultimately willing to endorse.

In sharp contrast, visionaries have a large-scale understanding of where the nation should be heading. They are entirely willing to press a controversial theory about, say, liberty or equality or the president's power as commander-in-chief, even if that theory offends many Americans. Visionaries object that minimalists are too cautious, too accommodating, too fearful. If visions call for wholesale rejection of the views of "the other side," so be it. Chief Justice John Marshall and Justice Hugo Black rank among constitutional law's great visionaries, having favored sweeping decisions about federal power (Marshall) and free speech (Black). On today's Court, Justices Antonin Scalia and Clarence Thomas frequently operate as visionaries, in the sense that they are entirely willing to overrule precedents in favor of their own distinctive visions of constitutional law. They would gladly overrule Roe v. Wade, and they would readily reject decades of precedents on affirmative action and campaign finance regulation.

Barack Obama is widely regarded as a visionary because of his emphasis on "change" and his soaring rhetoric, but he also has strong minimalist tendencies. In his victory speech in Iowa, Obama went out of his way to say that it is time for a president who will "listen to" those who disagree, and also "learn from" them. In The Audacity of Hope, he asks for a politics that accepts "the possibility that the other side might sometimes have a point." In a crucial passage, he refers to "the middle-aged feminist who still mourns her abortion, and the Christian woman who paid for her teenager's abortion." In this way, he suggests that across one of the nation's least tractable divides, Americans have far more in common than we tend to think.

Like all minimalists, Obama believes that real change usually requires consensus, learning, and accommodation--a belief directly reflected in many of his policies. He favors aggressive action on climate change, but he has shown an interest in nuclear power and he insists on "a market-based strategy that gradually reduces harmful emissions in the most economical way." Unlike most Democratic senators, he acknowledges that large increases in the minimum wage might "discourage employers from hiring more workers," which helps explain his enthusiasm for the Earned Income Tax Credit, an anti-poverty policy with Republican roots that supplements wages but does not have disemployment effects. Rejecting the orthodoxy of many Democrats, Obama does not want to excise religion from the public sphere. He insists only that "[w]hat our deliberative, pluralistic democracy does demand is that the religiously motivated translate their concerns into universal, rather than religion-specific, values." In 2005, Obama voted with Republicans in favor of the Class Action Fairness Act, which increases the rights of defendants in class action suits. After he received an e-mail from a pro-life doctor, Obama softened his website's harsh rhetoric on abortion, writing: "[T]hat night, before I went to bed, I said a prayer of my own--that I might extend the same presumption of good faith to others that the doctor had extended to me." In a letter to Daily Kos, discussing the appropriate tone to be taken by public officials, Obama wrote, "Americans are suspicious of labels and suspicious of jargon. ... They don't think that corporations are inherently evil."

On some topics, his approach overlaps with the Third Way thinking associated with Bill Clinton and the Democratic Leadership Council. But Obama has no interest in "triangulation." He does not insist on compromise as such. His brand of minimalism has its own audacity and takes a distinctive form. In the constitutional domain, and in ordinary politics, minimalists tend to be downbeat, even a bit dull, and they insist on small steps. But there is nothing downbeat or dull about Obama. And even as he tries to incorporate diverse viewpoints, he is willing to think big. Some of his policy proposals are bold, not incremental. His plan for energy independence, for example, is extremely ambitious, calling for a $150 billion expenditure on clean fuels and for a series of public-private partnerships designed to promote efficiency and conservation.

But Obama's visionary thinking is not adequately captured in his policies. It is found instead in his insistent rejection of the standard political categories, in a way that recognizes their obtuseness, their debilitating effect on actual problem-solving, their tendency to entrench the status quo, and the violence they do to American pluralism and diversity. Recall the most important passage from his keynote address at the 2004 Democratic Convention: "We worship an awesome God in the blue states, and we don't like federal agents poking around our libraries in the red states. We coach Little League in the blue states, and, yes, we've got some gay friends in the red states. There are patriots who opposed the war in Iraq, and there are patriots who supported the war in Iraq."

"Visionary minimalist" may sound like an oxymoron, but in fact--and this is the key point--Obama's promise of change is credible in part because of his brand of minimalism. He is unifying, and therefore able to think ambitiously, because he insists that Americans are not different "types" who should see each other as adversaries engaged in some kind of culture war. Above all, Obama rejects identity politics. He participates in, and helps create, anti-identity politics. He does so by emphasizing that most people have diverse roles, loyalties, positions, and concerns, and that the familiar divisions are hopelessly inadequate ways of capturing people's self-understandings, or their hopes for their nation. Insisting that ordinary Americans "don't always understand the arguments between right and left, conservative and liberal," Obama asks politicians "to catch up with them." Many independents and Republicans have shown a keen interest in him precisely because he always sees, almost always respects, and not infrequently accepts their deepest commitments.

To the extent that Obama is able to call simultaneously for change and reconciliation, it is in significant part for this reason. And to the extent that Obama's candidacy is producing a kind of national exhilaration not seen in many decades, his practice of anti-identity politics is a key factor. For him, reconciliation is change, and it is also what makes change possible. Recall that minimalists are willing to endorse large shifts from the status quo--after diverse people have been heard, learned from, and brought on board.

Obama's minimalism thus has a clear pragmatic purpose. The challenges of health care reform, Iraq, economic growth, climate change, and energy independence cannot possibly be met well, and perhaps cannot be met at all, without cross-cutting coalitions. Real transformations require a degree of consensus. Obama's point also has intrinsic and not merely instrumental importance, and for one simple reason: It says something deeply true, and long neglected, about how Americans actually understand themselves. If Obama's visionary minimalism turns out to have enduring power, it will be for that reason.

Cass R. Sunstein is a contributing editor to The New Republic and coauthor of the forthcoming Nudge: Improving Decisions About Health, Wealth and Happiness. He has been an occasional, informal adviser to Barack Obama. This article appeared in the January 30, 2008 issue of the magazine.