(THE TENNESSEAN) - Constitution Day on Sept. 17 is a uniquely American holiday, far more unique than the Fourth of July. Many countries celebrate an independence day. But only the United States has a 226-year-old written constitution that authoritatively shapes its national life.

Other countries, such as France, have lived under many different regimes, so that for them the nation is something distinct from its form of government. Not so for Americans, who have lived since the 1780s under the same regime, a remarkable fact, the significance of which seems to escape us. We revere our Constitution blandly, without troubling ourselves to know very much about it, and without reflecting much about what it says about our national identity.

Ties of race, religion and ethnicity have never been what bound Americans. We think of "diversity" as a recent issue, but the conduct of American life has always involved the negotiation of profound differences. Our Constitution took it as given that such differences and our human imperfections would generate conflicts. Ambitious individuals and power-hungry interests would always be among us, and their dangerous energies had to be properly channeled.

Our Constitution is, accordingly, short on soaring rhetoric, and long on procedure, laying out the complex rules of political engagement. Behind the familiar formula of "checks and balances" is a powerful idea: rather than trying to prevent conflict, this Constitution would presume conflict and even institutionalize it, thereby directing its effects to the general good. Like an internal combustion engine, the Constitution uses the explosions within its chambers to drive the effort of American governance. But for that very reason it is not conducive to smooth or unanimous action flowing from centralized power. Indeed, the craving for centralized unanimity is precisely what it most distrusts.

This aspect of the American system is ill-understood at home and abroad. When I gave a lecture in Ankara at the height of the Iraq War, a Turkish questioner wondered whether the intense conflict then going on in Washington meant that the American system was falling apart. When I responded, "But this is how the system is supposed to work," and that congressional resistance to the president can be entirely proper and legitimate, the audience was incredulous. I would tell that audience precisely the same thing today, about Republican congressional resistance to President Obama on various policy fronts. Such conflict can be a sign of health rather than weakness. It would be good if more Americans understood the ways in which the corrective energies of their system actually operate, instead of seeing endemic conflict in Washington in despairing terms.

But for conflict to be constructive, there has to be one point of agreement: prior acceptance by all parties of the Constitution's overarching authority. There can be no successful game without durable rules. And when push comes to shove, our Constitution has functioned remarkably well as the umpire of last appeal in contentious public debates. Its authority remains indispensable. It deserves to be celebrated - and to be better understood.

Wilfred M. McClay is the founding co-director of the Center for Reflective Citizenship at the University of Tennessee at Chattanooga. He is one of the founding board members of the Jack Miller Center for Teaching America's Founding Principles and History.