In Libya, the unknown unknowns are legion. We could be helping to bring to power a government even worse than Gadhafi's or creating a new haven for Islamic terrorists. One option is shipping weapons to the rebels -- kind of like what we did in Afghanistan following the 1979 Soviet invasion.
Those weapons, as fate would have it, helped bring the Taliban to power.
We will inflame greater suspicion in the Arab world. Conservatives like to credit George W. Bush's Iraq crusade for spawning democratic movements in Arab nations. But most Arabs don't share that flattering opinion.
Following the Iraq war, Zogby International polls found that by 2006, only 12 percent of Arabs in six countries had a favorable attitude toward the U.S. Two out of three said democracy was not a genuine American goal in the Middle East.
We may harm the cause of those we want to help. One reason these new democratic movements have generated such broad enthusiasm is that they are homegrown -- not fostered by Washington at the point of a gun.
"Right now, it's not about us, and I don't want it to be about us," says Christopher Preble, director of foreign policy studies at the libertarian Cato Institute. Once the U.S. attacks, many Arabs will see it as a fight between an Arab leader and the American imperialists bent on subjugating Muslims, not a heroic struggle by the Libyan people against a dictator.
The United States has had an eventful decade in the realm of military and foreign policy. During that time, we have discovered, at a dear cost, the limits to America's power to transform the world. But we can always learn that lesson again.