London doesn’t feel like a city under siege. The restaurants are crowded. Outdoor tables at the pubs are overflowing, with customers spilling out onto the streets. The throngs are thick in Piccadilly. Young people cluster around and cling to the statute of Eros like so many barnacles on a ship. Favorite tourist haunts are well-haunted. Double-decker buses are full. The tube is running more or less on schedule. And Al-Jazeera is readily available on hotel cable television.

But there are signs: Police personnel armed with automatic weapons patrol St. James Park, the Mall, Parliament Square, and Trafalgar Square. Visitors are put through bag checks at sites of historic importance and crowded hot spots like Madame Tussaud’s. All police leaves have been canceled as London’s Metropolitan Police conduct the most full-scale operations since World War II. More than 6,000 police officers patrol the London trains.

On the BBC, the shooting death of a Brazilian immigrant, Jean Charles de Menezes, in London on an expired visa with what police allege was a forged stamp on his passport, vied with the latest news of the terrorist threat for top story. Menezes was shot seven times in the head as he allegedly fled from crack undercover police. Despite the tragedy of Menezes’s death, the commissioner of the Metropolitan Police, Sir Ian Blair, defended the shoot-to-kill policy, as did 67% of the public in opinion surveys. The reason for aiming for the head, said Sir Ian, is that shooting a suicide bomber suspect anywhere else on his body might lead either to inadvertent triggering of the explosives or, though wounded, prompt the bomber to ignite the explosives himself. Using Tasers to subdue a suspect under such circumstances is also very dicey, police officials indicated, and for the same reason. Prime Minister Blair, though indicating he was “desperately sorry” for the shooting error, asked for public understanding of the inordinately difficult and dangerous job facing the Metropolitan Police.

Other visible anti-terrorist measures include targeted, not random, searches of tube travelers carrying packages and rucksacks. Those defending the policy declared it made little sense to pore over the belongings of little old ladies when one is trying to stop suicide bombers, as there is a particular demographic associated with terrorist activity. Complaints about all this – at least those that made it into the letters columns of newspapers – seemed rather muted by comparison to the uproar that would attend any such openly stated non-random policy in America.

At the same time, the “Blame Iraq, America, and Tony Blair” crowd is in full flower, with precious few making the important distinction between a causal relationship linking Britain’s Iraq policy and suicide bombers, by contrast to a contributing circumstance. The prime minister has the nuance down – “No, I don’t think this government is to blame for these terrorist acts. The terrorists are to blame. But, of course, the perpetrators of an ‘evil ideology’ use the Iraq war, and much else, to their own ends” – but members of the British press that bays at Mr. Blair’s heels like bloodhounds after an escaped convict, appear unmoved by Mr. Blair’s calm reason.

Editorial opinion to this point, with few exceptions, is uniformly condemnatory of the terrorists. But the caveats are quite interesting, with some columnists suggesting the Islamists might just have a point about Western cultural decadence and that perhaps we in the West should do a bit more inward searching about our overly permissive societies. More common – and remarkable to American eyes – are the critiques of Islam qua Islam, with suicide bombers and terrorists construed not so much as a perverted version of the faith but an appeal to it.

Phillip Blond and Adrian Pabst, writing in the International Herald Tribune, proclaimed:

“Regarding classical Islam, the oft-quoted remark that Islam is a religion of peace is false. It is historically illiterate to claim that war is foreign to Islam and it is theologically uninformed to argue that jihad is merely a personal inner struggle with no external military correlate. On the contrary, Islam is linked from the beginning with the practice of divinely sanctioned warfare and lethal injunctions against apostates and unbelievers.”

The authors go on to point out that the Prophet himself was a military leader whose vision of Islam was inescapably theocratic – a policy that “expanded – through warfare – all over the known world,” until all had come under the “house of Islam.” Until such time, non-Islamic lands were part of “dar al-harb,” or the “house of War.”

Agreeing that there might well be something about Islam itself that gives aid and comfort to terrorist bombers, A.N. Wilson, in the Evening Standard, went on to launch a generalized rant against religion. Christians were once a bunch of violent bastards, too, he opined, until the “Enlightenment drew its sting by compelling it to modify truth claims.” That is historic ignorance on Mr. Wilson’s part, of course, as the high-medieval tradition was comfortable with the so-called “double-truth” doctrine, namely, that there could be truths differently expressed that might appear to clash but, in fact, did not. It would be rather tricky to account for the growth of science in the Middle Ages, acknowledged by all serious historians of the subject, if scientific truths were thoroughly disowned and discredited by theological truths. The upshot of this sort of commentary is, of course, that Islam needs to be yanked into modernity – and quick – just as other religions have been defanged.

But this misses the central point, namely, whether there exists within a faith a strong prophylaxis against fanatical violence. The Sermon on the Mount is unlikely to become a terrorist manifesto anytime soon. Unfortunately, there are sayings and deeds from the Prophet that can be turned to the purpose of killing innocent civilians, even as there are sayings and deeds of the Prophet that point in the other direction. This makes the task of Muslim moderates all the more difficult, necessary, and critical.

So where are British Muslims in all this? There are mixed signals. The day after the July 7 attacks, the Muslim Weekly, based in London, published a lengthy article by Abid Ullah Jan entitled “Islam, faith and power,” “the gist of which was that Muslims should strive to gain political and military power over non-Muslims, that warfare is obligatory for all Muslims, and that the Islamic state, Islam and Sharia [Islamic law] should be established throughout the world. It concluded with a veiled threat to Britain,” this according to Patrick Sookhdeo in an article in the Evening Standard. (Mr. Sookhdeo is described as the director of an Institute for the Study of Islam and Christianity.)

There are spokesmen for the British Muslim community who have stepped forward to condemn the attacks in clear and unequivocal terms. Among these, many expressed deep frustration that their own warnings over the years to British officials about what was going on in radicalized centers, like the notorious Finsbury mosque, went unheeded. The British policy of permitting hate-filled rhetoric and (in effect) suicide-bomber training to take place in their midst, now seems suicidally misguided.

But not all Muslims agree with the government’s hardball policy. Indeed, an uneasy undercurrent pertains. Large numbers of Muslims surveyed view the suicide bombers as religious heroes. And the most senior Islamic cleric in Birmingham, Mohammad Naseem, chairman of the city’s central mosque, prompted anger and embarrassment in the city and police officials standing at his side during a joint news conference after police seized one of the suspected July 21 would-be bombers in Birmingham, when he launched into a tirade during which he called Mr. Blair a “liar,” claimed that Muslims “all over the world have never heard of an organization called Al Qaeda,” and even questioned whether the July 21 suspects whose DNA was found at the scene and whose images were caught on CCTV cameras were the right people at all. Designed to “help calm fears of racial or religious tension” following the arrest of Yasin Hassan Omar, the suspected would-be bomber, the imam’s words seemed designed to have quite the opposite effect – all of this according to a full account in the Daily Telegraph.

Officials fully expect a third wave of attacks, perhaps this time against the trains rather than the tube or buses. Occasionally, Heathrow and Gatwick are mentioned as possible targets, making the casual security process at Heathrow rather inexplicable: “Oh, keep your jacket on, luv”; “No need to remove the shoes” – and the like. Those who “beeped” – as did I – receive a perfunctory pat-down (no wanding) as we made our way. This didn’t quite seem the path of enhanced vigilance.

Airport security is, perhaps, the least of it. Far more problematic is how the Brits are going to square their tough search out and arrest policy with actually convicting, punishing, or deporting the unapologetically violent. New legislation along the lines of the Patriot Act is being proposed. But it may be for naught given the fact that the British have incorporated the European Convention on Human Rights into British law. The prime minister himself once held this as his highest achievement, something he may live to regret. For the European Convention belies no apparent awareness that free societies under threat must make complicated trade-offs between individual rights and collective security.

One notable speaking out for the convention and against new legislation is Cherie Booth, Queen’s Counsel, the prime minister’s wife, who opined in a speech to lawyers and diplomats in Malaysia, after both the successful and failed attacks, that judges were society’s upholder of “ethical responsibilities” and that even with the London bombings, government “must act strictly in accordance with the law.” Patrick Hennessy, in an article in the Sunday Telegraph, portrayed all this as “Blair v. Blair,” arguing that there may be a genuine clash between the two Blairs on these matters, for the prime minister has expressed the view that lawyers are currently “thwarting the Government’s drive to bring in much-needed anti-terrorism legislation.”

How the Brits will eventually sort this out is not at all clear. Much depends on whether Mr. Blair sticks to his guns and on just how long the current, fragile national consensus holds. In the meantime, as this great world city carries on, analogies to the bombings of London by the Luftwaffe in World War II are daily brought to bear by the generation that must now confront a deadly internal threat. Listening to excerpts from Winston Churchill’s stirring wartime speeches, one feature of the renovated War Cabinet Rooms exhibits, sounded much less like history than present reality.

Ms. Elshtain is the Laura Spelman Rockefeller professor of social and political ethics at the University of Chicago and is the author most recently of “Just War Against Terror: The Burden of American Power in a Violent World” (Basic Books, 2003).