In an op-ed piece for the Wall Street Journal last week, Scott Simon — the smooth, urbane host of National Public Radio’s Weekend Edition — revealed himself to be the very personification of the antiwar liberal. A convert to Quakerism who revered Gandhi and Martin Luther King, Simon wrote that "pacifism seemed to offer a chance for survival to a generation that had been stunted by the fear of nuclear extinction."

Simon, though, had come not to extol pacifism but to describe its limits. In covering the Balkan wars of the 1990s, he wrote, he had learned "the logical flaw (or perhaps I should say the fatal flaw) of nonviolent resistance: All the best people can be killed by all the worst ones." And he was baffled by his former allies’ inability to learn that lesson — even in the aftermath of September 11.

"Many of the activists I have seen trying to rouse opposition to today’s war against terrorism remind me of a Halloween parade," he wrote. "They put on old, familiar-looking protest masks — against American imperialism, oppression and violence — that bear no resemblance to the real demons haunting us now."

Most liberals, of course, are neither Quakers nor pacifists. Still, Simon’s philosophical journey is similar to that taken by an entire generation of liberals for whom antiwar sentiments — forged in the dark insanity of the Vietnam era — had been central to a sense of political self.

Much of that journey took place during the last decade, from liberals’ measured opposition to the Gulf War in 1991 to their support for humanitarian intervention in Bosnia and Kosovo in the mid to late ’90s. The presidencies of George H.W. Bush and Bill Clinton were a time for liberals to question and modify their previous unbending opposition to the use of military force.

Then came September 11. For the first time since the Gulf of Tonkin resolution of 1964, which widened the Vietnam War from an unfortunate mistake to an irredeemable tragedy, congressional liberals rallied around the flag and the president. By a unanimous vote in the Senate, and with only one dissenter in the House, Congress approved sweeping war powers for George W. Bush — the closest thing to a declaration of war since 1941, after the attack on Pearl Harbor. Massachusetts’s senators, Ted Kennedy and John Kerry, both of whom had voted against the Gulf War resolution a decade earlier, expressed strong support for the president, with Kerry going so far as to call publicly for international terrorist Osama bin Laden to be tracked down and killed.

Nothing good came out of September 11. But it is surely good for the country that liberals have reclaimed their internationalist credentials. For decades, US foreign policy had been dominated by a conservative view of the world: narrow, bullying, and arrogant. What is needed now, more than anything, is a liberal foreign policy: one that combines protection of our self-interest with respect for human rights and the right to self-determination, dedication to equality for women and minority ethnic and religious groups, and commitment to civil liberties at home and freedom abroad. Liberals, after all, led the fight against fascism and Nazism, and rebuilt Europe and Japan after World War II, thus denying Soviet communism the breeding ground it needed to fulfill its expansionist aims. And it is liberal values that will be vital to winning the war on terrorism.

Historian Arthur Schlesinger Jr. was a close observer of liberal internationalism for more than half a century. "I think most liberals understand that you have to do something," he told the Phoenix. "You can’t stand aside and turn the other cheek when 6000 people are killed. This is quite unlike the Vietnam War, and much more like the emotion of the Second World War."

Schlesinger, though, cautions that the war on terrorism cannot be guided by the desire for blind retribution. Rather, he cites one of his deepest influences — liberal theologian Reinhold Niebuhr — in describing his hopes of how this war will be fought.

"Niebuhr really had a tragic sense of history and the conflict of values," Schlesinger says. "If he were alive today, I think he would take more or less the position of realistic liberals that something has to be done, but we shouldn’t carry it too far. We shouldn’t become like the enemy and have a counter-jihad to counter their jihad."

The latest scare — anthrax — shows just how insidious this jihad against us is likely to get. Like the planes of September 11, the envelopes containing mysterious, and possibly deadly, powder take perfect advantage of our openness. Dozens, perhaps hundreds, of copycats will no doubt send harmless powder to their enemies, inspired by hatred, warped political agendas, and mental illness. Liberal values have never been more threatened, or more necessary.