EDINBURGH, Scotland – Some critics of Tony Blair have pounded on the point that one of the four bombers had been identified by the security people as mischievously connected with aggressive elements of the Muslim community. So why had they not brought him in?

The innocence of the question recalls the questioning of J. Edgar Hoover by the Warren Commission in 1964, inquiring into the assassination of President Kennedy. Was it not known to the FBI that Lee Harvey Oswald had been active in a pro-Castro political organization in New Orleans? Yes, we knew that. Didn’t we know that he had left the U.S. Marines and declared himself a communist, marrying a Russian girl and setting out to live in the Soviet Union before returning home? Yes, we knew that. Wasn’t it known that he had traveled to Mexico City, where he might have conspired with Fidelistas to break U.S. laws? Yes, we knew he had been there. Well, how come on Nov. 22, 1963, he was squatting there in the Texas School Book Depository, a Mannlicher-Carcano rifle in his hands, at liberty to assassinate the president of the United States?

Mr. Hoover said that if everyone in America at the security risk level of Lee Harvey Oswald were secluded when the president passed by, we would have a politically intolerable situation. He gave the number of people in Chicago who, applying a hypothetical Oswald security meter, we’d have to segregate, and that number (was it 2,000?) sobered the house, and the commission moved on to the challenge of protecting a president other than by identifying and removing from the scene everyone who might wish him dead.

Hot critics of the vulnerability of London on July 7 edged into a different question: Hadn’t the government encouraged the bombers by the PM’s endorsement of U.S. policy in the Iraq war? Chatham House, a British think tank, encouraged such thought by observing that the British were now riding as a “pillion passenger” in the U.S. war tank, incurring enemies while abandoning freedom of movement. Mr. Blair replied that Britain is engaged in counterterrorist activity, and was several times singled out for Al Qaeda violence before the Iraq war even began.

The detailed examination of the movements of the four bombers tells of their awesome coordination, calling to mind the 19 Arabs who arranged life so as to meet only a few minutes separated aboard four airliners reoriented to plunge into buildings in New York and Washington. The British terrorists even seemed to pause, flukily, to appear on the camera screen at King’s Cross station, each one carrying a rucksack with explosives, just before three of them descended into the underground system, one headed west, one south, one east, to detonate their bombs at 8:50 a.m., the fourth one heading for a bus to do the same an hour later. That kind of coordination is not effected by random encounters, and we are required to think about the nature of the challenge: four very young men, resolutely set on death for themselves, provided only that there be at least 10 deaths of innocent British citizens for each of their own.

Mr. Blair, whether riding as pillion passenger or as guide, needs to contend against such persons at whatever scale they present themselves – riding in the tubes of London, or flying high over the skies of Manhattan or Washington, or coordinating in a laboratory of biological, chemical or nuclear horror. We have to hope that sanity will break through. What Islamic voice – we are entitled to ask over and over – can break through to those consciences awry, to tell them they cannot accomplish the end of the Western world? And that in pursuit of that goal, they are committing their own suicide, and enhancing the kind of impatience toward Islam which could doom their co-religionists by the tens of thousands, to deaths as bloody as they are bent on inflicting on others?