Schoolchildren in the 1950s practiced diving under desks in case the Soviets launched the Bomb. Today, parents in some school districts are being asked for permission to administer potassium iodide to their children in a nuclear emergency. How did the United States, long after the Cold War ended and Russia’s missiles were redirected, come to such a pass?

The short answer is 9-11. But at least two lessons may be drawn from the manifest vulnerability demonstrated that day.

One is that we are at war and must fight back. President Bush communicated this effectively with his “evildoers” rhetoric, his promise to hunt the terrorists down one by one no matter how long it takes and by establishing a new government agency for homeland security.

The other lesson asks, “Why the hatred?”

Such a question is difficult so close to 9-11 and, in wartime, invites attacks on one’s patriotism.

But asking unpopular questions is the hallmark of real leaders. John F. Kennedy’s “Profiles in Courage” reminds us of some in our nation’s history: Thomas Jefferson splitting with George Washington over foreign policy, Henry Clay risking defeat by searching for compromises on slavery, Sam Houston alone among Southern senators opposing the Kansas-Nebraska concessions to the South, and Abraham Lincoln, first among equals in the American pantheon.

What are the causes of terrorism and anti-American hatred? Unless this is asked, and the question is generally absent from contemporary discussion, how can intelligent, dispassionate and effective responses be shaped?

If the commission investigating the events leading up to Sept. 11 focuses mainly on intelligence failures and not on policy failures, it too will be a failure. This is not the place to explore specific answers.

Historians and policy-makers will no doubt disagree over what responsibility the United States bears for the violence-producing conditions in the world. Some say we have no responsibility at all; others that we brought it on ourselves.

Of the two, denial is more dangerous because it obscures questions of responsibility and reinforces the popular domestic view that the United States is a force only for good in the world, the defender of liberty and democracy, the best country on Earth and probably in history.

These beliefs are the stuff of which war fever, not effective policy, is made.

The United States drew the wrong lesson from 9-11. Instead of emphasizing that the American people, given the half-life of hatred, may never again be free from attacks unless we stand for peaceful and fair change, our leaders turned toward war. What if this decision produces thousands more casualties in the United States and more carnage as far into the future as one can see? How wise will the president’s war policy seem then?

Searching for peaceful answers in the Middle East and elsewhere is harder than being goaded into war by hopeless fanatics, but history teaches that it is often the question not asked that leads to disaster. More than 58,000 names on the Vietnam War Memorial in Washington attest to the wisdom of pausing before choosing war as a solution.

John F. Manley is a professor emeritus of political science at Stanford University.