THERE HAVE always been beggars outside palaces, and comfortable people have always preserved their capacity for happiness by screening out other people's pain. But this self-protective instinct seems particularly powerful at the moment, as genocide unfolds slowly in Sudan's western province of Darfur. The world knows, and on Friday the United Nations Security Council acknowledged, that Sudan's government is responsible for burnings of villagers, systematic rapes and murder by starvation. It knows that these atrocities continue. And yet outsiders are content with measures that won't stop the appalling suffering. They issue statements but refuse to send adequate relief supplies. They condemn violence but refuse to send peacekeepers to protect civilians.

How to explain this numbness? There are excuses for inaction -- or, more charitably, "caution" -- and they deserve to be confronted one by one. The first is that outsiders must respect Sudan's sovereignty, for sovereignty is the basis of orderly international relations. States threaten their neighbors only if they espouse aggressive foreign policies, this argument goes. What they do within their own borders is their own concern, and meddling establishes the dangerous principle that intervention is generally acceptable. As Henry Kissinger has argued in another context, the legal doctrine of national sovereignty and the principle of noninterference -- both enshrined in the U.N. Charter -- emerged at the end of the devastating Thirty Years War, the 17th-century conflict during which perhaps 40 percent of the population of Central Europe perished in the name of competing versions of universal truth. Humanitarian intervention leads to "virtue run amok."

This "realism" has always had a tenuous hold on American foreign policy for the good reason that this nation is founded upon universalist principles. But it seems particularly misplaced in the age of international terror, when respecting the sovereignty of failed states such as Afghanistan is not a viable option. The attacks of Sept. 11, 2001, demonstrated that what states do within their own borders can affect international security. Sovereignty is therefore a less useful principle than it once was, and Kofi Annan, the U.N. secretary general, has commissioned a study on ways of updating it. Refusing to save hundreds of thousands of people in Darfur out of defer- ence to an already tattered doctrine seems unwarranted.

Then there is the argument that foreign policy must be conducted "in the national interest," and that saving people in Darfur fails that test. There is an admirable democratic quality to this argument: The elites who run representative governments should make policy that reflects the outlook of the voters whom they represent. But do ordinary voters really oppose action? A recent PIPA-Knowledge Networks poll of 892 Americans found that, if the United Nations were to determine that genocide is occurring in Darfur, 57 percent would favor foreign intervention, including American intervention, while only 32 percent would be opposed. The nation's interests are in fact broader and more compassionate than the national-interest argument implies.

Finally, there is the fear that foreign intervention in Sudan, especially one led or orchestrated by the United States, could trigger a popular backlash throughout the Muslim world. If this were correct, it would be extremely serious: The war against terrorism is a battle for Islamic hearts and minds. But the basis for this fear is shaky. It is true that Egypt's government opposes foreign intervention in its southern neighbor, not least out of a cynical belief that its own security and economic interests are served by an unstable Sudan. It is true, equally, that Sudan's Islamic government has greeted talk of Western intervention with a pledge to repel the "crusaders." But the key to winning hearts and minds throughout the region is not to defer to the autocratic government of Egypt, still less to Sudan's rulers, whose victims in Darfur are after all Muslims. In contemplating intervention in Sudan, Arab opinion must be considered. But it's not clear that this means that intervention should be ruled out.

Perhaps there are other arguments for "caution" in the face of Darfur's genocide, and we invite President Bush and other leaders to come forward and explain them. According to officials at the U.S. Agency for International Development, up to 30,000 people in Darfur have died violently, 50,000 have died of disease and malnutrition, and the death toll is likely to reach at least 300,000. The reasons for non-intervention had better be as powerful as those astonishing numbers.