A fundamental principle of international law and morality is that the deliberate murder of civilians is always wrong. In war, it is a war crime. In peace, it is terrorism. No matter the justice of the underlying cause, no end can ever justify that means. This principle unites civilized people in abhorrence of both the crimes of September 11 and the Palestinian bombings of Israeli cafes, restaurants, and buses. It is the core of President Bush’s conviction that we are in a battle of good against evil.

This principle is disdained, however, by the large percentage of the Muslim world’s 1.2 billion people who support the indiscriminate murders of Israeli men, women, and children. It is also ignored by the European elites who palliate wanton massacres of Jews while excoriating unintended killings of civilians by Israeli troops seeking to root out Palestinian fighters. Most do not even attempt a forthright defense of the morality or legality of Palestinian terrorism, preferring to euphemize mass murder as "resistance."

But some apologists for Palestinian terrorists (like those for the Irish Republican Army, Italy’s Red Brigades, and others) do sketch the outlines of an argument: that the ends of stopping an imperialistic Israeli settlement policy and liberating Palestinians from Israeli occupation justify the means of attacking civilians. Repugnant as this argument is, it begins with two kernels of truth and contains a moral-relativist logic with superficial appeal. It is therefore worth confronting and refuting.

The kernels of truth are that a rule against ever targeting innocent civilians for lethal attack is hard to sustain as a moral absolute and would condemn some American and Israeli leaders. If killing 10 (or 100) innocent civilians were the only way to avert the certain deaths of 1,000 others, shouldn’t we do it? Does anyone doubt the morality of our own government’s post-September 11 policy of shooting down any civilian airliner that hijackers are about to crash into a skyscraper, and thus sacrificing already-doomed passengers to save others? If 60 years ago, German Jews or Allied infiltrators had launched suicide bomb attacks on German cafes and buses in the hope of stopping or slowing the Holocaust, would we see moral equivalence? If Ariel Sharon had ordered the extermination of Palestinian men, women, and children, would we condemn Palestinians for responding with suicide bombings?

The very notion that civilian lives are inherently more innocent or precious than the lives of (say) 18-year-old boys who enlist in the military is unsupportable. The soldiers and sailors at Pearl Harbor, and those at the Pentagon on September 11, no more deserved to die than did their mothers, fathers, or 10-year-old sisters. While military volunteers (unlike draftees) do assume the risk of combat, that makes them no less innocent than you or me; it makes them more heroic, if the war is just. The end-winning the war-is identical. The means-killing innocent people-is no less terrible if the innocents to be killed are soldiers.

So what’s the basis for the soldier-civilian distinction in the law of war? It is that, as a general rule, killing combatants (although not enemy prisoners) is more likely to help win the war than killing civilians. This distinction is sound as a matter of law, because law needs general rules. But general rules have exceptions-in life, if not always in law.

The incineration of 115,000 to 150,000 people in Hiroshima and 60,000 to 80,000 in Nagasaki (these are conservative estimates) by atomic bombs probably did more to end World War II than killing 500,000 Japanese soldiers and seamen in ordinary combat would have done. And by ending the war, these bombs saved the 1 million to 2 million (by some estimates) Americans and Japanese who would have died in an invasion of Japan. Whether the March 1945 firebombing of Tokyo ended up saving more lives than the over 100,000 it took is more debatable. So is this question: How many American military men should President Truman have been willing to sacrifice in order to avoid killing so many Japanese civilians? And what about the bombing of Belgrade during the Kosovo conflict?

The point is that in some cases, there may be a strong argument that the end of saving innocent lives can justify the means of deliberately killing civilians. One could formulate a cold-blooded moral equation along the following lines: Targeting civilians is an appropriate strategy whenever the justice of the cause multiplied by the likelihood of success exceeds the human cost, if we measure "justice of the cause" by the number of lives to be saved (or of Palestinians to be freed from Israeli occupation); "likelihood of success" by the mathematical probability that the killing will in fact help the cause; and "human cost" by the number of civilians to be killed.

Does this mean that sometimes targeting civilians is OK? Absolutely not, contends professor Philip Bobbitt of the University of Texas Law School, the author of a new book (The Shield of Achilles) that explores deeply the history of war and law: "The terrorist does not reluctantly accept the accidental killings that accompany warfare; his whole point is to kill ordinary people in order to make them fearful. If we make targeting civilians lawful, we turn our armed forces into terrorists."

Notwithstanding the likelihood that the bombings of Hiroshima, Nagasaki, and (perhaps) Tokyo ended up saving more lives than they took, Bobbitt asserts, they would have been war crimes had civilian populations been the primary targets. He acquits Truman only on the ground that these cities were in fact military targets, because they contained military facilities, a portion of Japan’s military-industrial base, and (in the case of Tokyo) the seat of the enemy regime and war machine.

I am respectfully skeptical of both contentions. And even Bobbitt is troubled by the February 1945 firebombing of Dresden (primarily by the British)-clearly not a prime military target-that killed more than 30,000 Germans (some guess 135,000). Winston Churchill himself expressed concern a few months afterward that the Dresden inferno may have crossed the line. And both Churchill and Truman brooded about the terrors they had unleashed to win the war. "Mr. President," Churchill said at a January 1953 White House dinner, "I hope you have your answer ready for that hour when you and I stand before St. Peter and he says, `I understand you two are responsible for putting off those atomic bombs. What have you got to say for yourselves?’ " Neither man expected to be rewarded with a bevy of virgins.

Historians and statesmen have long argued about the morality and legality of these attacks on Japanese and German cities. Some have pronounced Truman and Churchill guilty of war crimes. But it is beyond dispute that their bombing strategy was designed to hasten-and did hasten-both the end of an apocalyptic war in which 40 million noncombatants had already died and the demise of the evil regimes that had launched that war. If there were war crimes, there were also mitigating circumstances.

No such connection to a just cause even begins to mitigate the evil done by those who have targeted and massacred Israeli (or American) civilians. The Palestinian bombers’ primary cause is not just: It is to destroy the Jewish state by killing as many Jews as possible.

Many Palestinians do have a just cause: ending Israeli occupation, creating a Palestinian state, and living in peace. But that cause is not on the same moral plane as saving lives. Nor will it be furthered by the current attacks. Bobbitt notes, "If the 35-year Israeli occupation and Israeli settlements in occupied lands are unlawful, then Palestinian violence in those areas directed against the occupation forces is not terrorism." But be that as it may, the attacks on civilians in Israel proper are convincing moderate Israelis and Americans (who never imagined themselves agreeing with Ariel Sharon) that tight military control of the West Bank and Gaza-perhaps for decades-is the only way to contain Palestinian terrorism.

Truman and Churchill saw the bombing of cities as a "hideous" (Churchill’s word) strategy to end an even more hideous war. Today’s American and (most) Israeli leaders regret, and strain to minimize, civilian casualties in Afghanistan and the West Bank and Gaza. Meanwhile, many Arab leaders, like Nazi Germany’s, broadcast lies to inculcate their people with murderous hatred of Jews. Saudi Arabia, like Iraq, provides posthumous family financial packages for Palestinian suicide bombers. With the many decent Arabs who abhor terrorism cowed into silence, the mobs in the streets celebrate the murders of Jews. Many celebrated the murders of September 11.

We aspire, not always successfully, to be civilized. They revel in barbarity.