Before their empire fell, the Romans built walls.
They began by erecting barriers along the border following the death of the Emperor Trajan in 117 A.D., notably Hadrian's Wall, which belted Britain. Later emperors erected internal walls, even around the great city itself, to ward off barbarians. After 300 A.D., the Emperor Diocletian effectively converted the entire Roman populace into feudal serfs, walling them off from internal movement in a vain effort to stabilize the chaotic economy.
Despite the cautionary tale of Rome, building walls, both literal and figurative, has remained a habit of great powers in decline -- the fateful course taken not only by Ming China, but also Soviet Russia, and even Great Britain.
Sadly, many Americans are all too eager to repeat history.
Witness the immigration bill slowly making its way through Congress, and the feverish reactions it has inspired. In exchange for granting undocumented workers a path to citizenship, Republicans have demanded a so-called "border surge" that would double the number of patrol agents in the Southwest and build an extra 700 miles of fencing. Due to bipartisan prejudice against so-called "low-skill" migrants, the legislation is also loaded with dangerous new government controls over the labor market. The Senate bill, for example, requires employers to post new jobs on a Labor Department website, certify that no citizen is displaced, and surrender wage-setting to bureaucrats. Nevertheless, the conventional wisdom is that the bill will open a floodgate of foreigners. The Heritage Foundation issued an outlandish warning about the supposed multi-trillion-dollar fiscal burden of new immigrants, practically suggesting that the Statue of Liberty be melted down for the border fence.
Isolationism, unfortunately, is not limited to one policy or one party. Liberals have been skeptical of free trade for decades now. Less than 10 percent of House Democrats voted for the Central American free trade agreement in 2004. And Democratic politicians, including President Obama during his re-election campaign, routinely hype the danger of multinational firms outsourcing jobs.
Before the Fall, a Wall
The psychological impulse to protect a nation's wealth and culture from foreign contamination is an example of what behavioral economists call "loss aversion" - the idea that people are more concerned about what they might forfeit than gain from change. History tells us that with great power comes great loss aversion.
Take the fate of Ming China, the world's most fabulously wealthy civilization in the 15th century. The empire cut itself off from foreign trade after the 1430s, an action urged by Mandarin bureaucrats in order to clip the power of the merchant class, their rivals at court. Court intrigue is also revealed by the extension of China's Great Wall, and the abrupt termination of the voyages of Admiral Zheng He, both reflecting the Confucian attitude that foreign barbarians offered nothing of value. The following centuries saw China transform into a weak and isolated time capsule.