When the twenty-first century dawned, Americans were enjoying a booming, self-confident period of affluence. But few people were paying attention to worsening poverty at home, or to the mounting levels of anger abroad.

There had been plenty of warnings. Islamic terrorists had struck repeatedly—in the 1993 bombing of the World Trade Center, in the destruction of two U.S. Embassies in Africa, and in the bombing of the USS Cole in Yemen. But despite these attacks, in the late summer of 2001 most Americans were unaware that a holy war had been declared on the United States. A fundamentalist militant named Osama bin Laden had called it the duty of every Muslim to kill Americans and work to destroy free society in the western world.

On the morning of September 11, 2001, followers of bin Laden carried out his threat with attacks on the World Trade Center and the Pentagon. One week later President George W. Bush addressed the nation: "On September the eleventh, enemies of freedom committed an act of war against our country. The advance of human freedom, the great achievement of our time and the great hope of every time, now depends on us.... Freedom and fear are at war."

America committed itself to a war against terrorism, and to an unprecedented tightening of its own national security. In the months that followed, a widespread debate took place about how to properly balance security and freedom. Historian Eric Foner explained the concern of many: "Obviously security is of tremendous importance to anybody. Remember, one of the four freedoms President Roosevelt mentioned was freedom from fear. But I think it would be self-destructive to in any significant way limit our freedoms in order to protect our security. After all, ultimately our security is supposed to protect our freedom, and if we start limiting the right to dissent, if we start stigmatizing people because they come from one portion of the world or another, or because they follow one religion or another, we may end up with a great deal of security and not nearly enough liberty."