How the United States responds to this week's terrorist attacks in New York and Washington involves the most difficult, and in some ways the profoundest, questions a nation and its leaders can face:
To what extent is retaliation justified, especially when the attackers are difficult to pinpoint? Are the attacks on the World Trade Center and the Pentagon "acts of war," requiring a declaration of war in return, even though no single nation may be responsible? Perhaps most difficult, how does America balance justice and the rule of law - foundations upon which this country was built - with the deeply emotional attraction of revenge for its own sake?
In practical terms, the options are limited. These might include: limited military attacks involving bombers and cruise missiles (as the Clinton administration tried against Afghanistan and Sudan), assassination of those thought to have plotted the attacks, invading any country suspected of being directly responsible, rallying the world community to declare war on terrorism, or changing certain aspects of US diplomatic policy.
But each includes its own set of difficulties, and even hard-nosed military and intelligence experts see Tuesday's massive attacks on American soil in philosophical terms involving the nation's essential values. "It takes a Plato or an Aristotle to look at this one," says Stanley Bedlington, a retired senior counterterrorism analyst with the CIA.
Historians, ethicists, and religious leaders often place such incidents in the context of "just war" theory - the belief that any response be limited to military targets or personnel. "Just because somebody murders our people doesn't allow us to murder theirs," says G. Scott Davis, professor of religion and ethics at the University of Richmond, Va. This includes assassinating those considered to be dangerous enemies, which the US has disavowed.
For many in Washington, exiled Saudi Osama bin Laden is the prime suspect, and Afghanistan - where the suspected terrorist is living under the protection of a government ruled by the Taliban Islamic militia - is very likely complicit in Mr. bin Laden's activities.
"This was too elaborate to have been carried out by a bunch of guys in a garage somewhere," says Paul Bremer, the former ambassador who chaired the National Commission on International Terrorism last year. "At the very least, there was a state or states looking the other way while the planning went on."
Just hours after the attacks, President Bush made it clear that a state need not have "sponsored" terrorism in order for it to be the target of retaliation. "We will make no distinction between the terrorists who committed these acts and those who harbor them," he told the American people from the White House Tuesday night.
On Capitol Hill, lawmakers express deep anger and frustration at what many see as a security and intelligence failure. Still, many lawmakers take a cautious approach to any quick military retaliation.
"The issue now is, what is a proportionate military response to something like this?" asks Rep. Jane Harman (D) of Calif., a member of the House Select Committee on Intelligence. Moreover, US officials know that even a proportionate military response can bring further risks.
"You target those governments that harbor terrorists, and then prepare yourself for a protracted conflict," warns Rep. Richard Neal (D) of Mass. "There are embassies around the globe that have never been terribly protected. So, there's a risk for Americans."
Like Mr. Bremer, many lawmakers believe that any military response should be robust and thorough - including Afghan government targets, if bin Laden is culpable and if that country succored him. Sen. Bob Graham, (D) of Fla., chairman of the Senate Intelligence Committee, goes as far as to suggest that this country's self-imposed ban on assassinations "ought to be revisited." But other experts see this as the route to further counterattacks, including those against innocent civilians - as some say is now happening in the Middle East, where Israel has specifically targeted certain Palestinian leaders.
"As a counterterrorist technique, assassination is not only immoral, but ineffective in accomplishing its stated goal: the deterrence of terrorism," Vincent Cannistraro, former chief of CIA counterterrorism operations, wrote in The Washington Post recently. "And it comes back to haunt the perpetrators in ways they never expected."
To some experts, the main response needs to be more diplomatic than military.
"The most constructive response for the president and government would be to become much more engaged in the Middle East," says Emilio Viano, a terrorism expert at American University in Washington.
"The region has been neglected," he adds, "and to the extent we have been involved, it has been increasingly interpreted as acting on the side of Israel."
"There is tremendous rage among Palestinians, and that has fueled the fires of fundamentalism," explains Professor Viano. "It would be more constructive to go to the root of all of this, and that is the Israeli-Palestinian conflict."
Going to the root of a problem that has simmered - and often flared - for decades and generations is difficult under far simpler circumstances than American now finds itself confronting.
And a military response, whether it is a quick retaliation or a protracted response meant to permanently change the geopolitical landscape, nonetheless brings with it the questions of balancing a nation's fundamental values.
"We have to be true to our principles, take into account the fact that people will be vulnerable and without offense and themselves at risk," says former CIA and FBI director William Webster. "We should avoid doing to them what they did to us, which is to take innocent lives."
Staff writers Gail Chaddock and Howard LaFranchi in Washington contributed to this report.