The best explanation of the government shutdown impasse points to two factors. The first involves information, or what people think they know. The second involves incentives, or what motivates people.

From research, we know that when like-minded people speak with one another, they tend to become more extreme, more confident and more unified - the phenomenon known as group polarization. One reason involves the spread of information within echo chambers.

If you are in a group whose members think the Affordable Care Act is horrible, you will hear many arguments to that effect and very few on the other side. After a lot of people have spoken, Obamacare will seem worse than merely horrible; it might well be taken as a menace to the republic. The House of Representatives has been a case study in group polarization.

In a free nation, of course, no member of Congress can really spend life in an echo chamber. They are aware that people disagree with them. To appreciate what is happening in Washington, we have to understand a bit more about the nature of political beliefs. It turns out that when people's convictions are deeply held but false, efforts to correct those views can backfire. Such efforts tend to entrench and fortify those very convictions.

When the news media correct a false proposition (say, that Iraq had weapons of mass destruction, or that George W. Bush banned stem-cell research), both conservatives and liberals may become even more committed to that proposition. Partisans and extremists know what they know, and efforts to correct what they know make them firmer still (and angrier to boot). It is for this reason that the beliefs of some of the most extreme House Republicans, and their constituents, appear almost immune to correction.

With respect to incentives, elected officials are often motivated by one goal above all: to get re-elected. They are focused on their own electoral prospects, not those of their party. They know they have to answer to their constituents, not to the nation as a whole.

Within the Republican Party, many members of Congress have no reason to fear a challenge from the left. There is no chance that they will lose their seat to a Democrat, and a moderate Republican isn't going to run against them. The only threat is from the right. With respect to any issue, the main question may well be whether, in the view of the most extreme conservative voters, the legislators will "cave" to President Barack Obama or instead stand up for their convictions. Is it any wonder many are willing to run the risks of a shutdown?

Some political scientists insist that elected officials are solely motivated by the goal of being re-elected, but this view is too simple. We should acknowledge that many officials are committed to principles. They want to do what they believe to be right. It is here that information matters. Elected in a wave of conservative outrage, fueled in part by some beast called Obamacare, many House members are standing on principle.

Because of what they think they know, they sincerely believe that the health-care law is a clear and present danger. For the nation, the problem is that beliefs of this kind create a clash of absolutes - and make compromise or accommodation unusually challenging.

The framers of the Constitution fully appreciated these risks. Indeed, their document was designed to ensure against situations of precisely the kind the nation is now facing.

James Madison, the father of the Constitution, was concerned above all about the risks of faction, which he defined as citizens "united and actuated by some common impulse of passion, or of interest, adverse to the rights of other citizens, or to the permanent and aggregate interests of the community."

Madison hoped it would be possible "to refine and enlarge the public views, by passing them through the medium of a chosen body of citizens, whose wisdom may best discern the true interest of their country, and whose patriotism and love of justice will be least likely to sacrifice it to temporary or partial considerations."

It is an understatement to say that this kind of refinement and enlargement is not occurring. We will not see them unless the most extreme partisans are able to move out of their echo chambers, and unless the incentives of those members are significantly altered.

Cass R. Sunstein is the Robert Walmsley University professor at Harvard Law School and a Bloomberg View columnist.