These are extraordinary times in the history of freedom. In the Arab Spring, we have seen the broadest challenge to authoritarian rule since the collapse of Soviet communism. The idea that Arab peoples are somehow content with oppression has been discredited forever. Yet we have also seen instability, uncertainty and the revenge of brutal rulers. The collapse of an old order can unleash resentments and power struggles that a new order is not yet prepared to handle. Some in both parties in Washington look at the risks inherent in democratic change—particularly in the Middle East and North Africa—and find the...