Harvard professor Samuel Huntington's "class of civilizations" hypothesis --- a provocative preview of a 21st century in which religiously shaped cultural conflicts define the fault-lines of world politics --- created a considerable intellectual stir when it was first published in 1993. It also caused an allergic reaction in the Vatican that persisted for over a decade, which always seemed to me puzzling.

Perhaps some churchmen, reading about the controversy over the book rather than reading the book itself, imagined that Huntington was prescribing a clash of civilizations. In fact, the mild-mannered professor was simply describing what seemed to him the most dynamic forces shaping world affairs today.

Another curiosity of the reaction inside the Vatican was that Huntington's was the first analysis in decades in which a world-class scholar took religious conviction seriously as a factor in global politics --- which, one might have thought, would have commended it to the Holy See's diplomats. But there is religious conviction and there is religious conviction. And doubtless Huntington's detailed description of Islam's "bloody borders" raised eyebrows in a Vatican already concerned about the pressures being put on Christian communities by radical Islamists along a fault line of conflict running from the west coast of Africa through Sudan and Pakistan and on to East Timor.

Given that background, a single adverb stands out dramatically in Pope Benedict XVI's January 9 address to the diplomats accredited to the Holy See. In the course of discussing the relationship of truth to politics, Benedict referred to "today's global context, in which attention has rightly been drawn to the danger of a clash of civilizations." Rightly been drawn. Not "incorrectly..." Or "mischievously..." Rightly.

This realistic appraisal of the contemporary world scene came not a month too soon. As I write in the second week of February, the publication of cartoons of the prophet Mohammed in a hitherto obscure Danish newspaper has ignited a "planetary intifada" (as French commentator Bernard-Henri Levy put it, with only slight exaggeration).

Encouraged by Islamist clerics and political scoundrels like Syria's Bashar Assad and Iran's Mahmoud Ahmadinejad, protesters have burned embassies and consulates, aroused mass demonstrations that have led to casualties and fatalities, intimidated European governments --- and murdered Father Andrea Santoro, whose teenage assailant shouted "God is great" while shooting the Italian priest in the back as he prayed before the altar of his small church in Turkey.

I have no brief for the cartoons, any more than I had a brief for the far more vulgar "Piss Christ." And yes, there was something ironic about passionate defenses of "free speech" in countries like France, where a parliamentarian was recently sentenced to a heavy fine because he had publicly proposed that "heterosexuality is morally superior to homosexuality." But arguments about the legal boundaries that should or should not be erected against "art" that religious believers find offensive, or arguments about the nature of Europe's soul-withering de-Christianization and its relationship to the rise of radical Islam within Europe, can be engaged at another time. At this particular moment, a few basic markers must be laid down.

The West cannot acquiesce supinely to the demand of radical Islamists that their standards of the appropriate are to be imposed in the West --- or else. Nor can the West acquiesce to the Islamists' defense of violence, assault and murder in the name of "rage." Nor can the West accept the radicals' suggestion that entire nations are to be held responsible for the arguably boorish behavior of some of their citizens, which would imply a level of governmental control of cultural life that is incompatible with a free society.

State-controlled media throughout the Islamic world regularly print and broadcast unspeakably vicious anti-Christian and anti-Semitic images. Will the Muslim leaders who have rightly condemned violence as a response to cartoons --- King Abdullah of Jordan and Grand Ayatollah Ali Al-Sistani of Iraq, to name two --- take the next step and call for a reform of the ways in which the media in Islamic countries depict Christians and Jews?

That would be one positive development to come out of this otherwise dismal affair, which has ominously broadened Islam's "bloody borders."

George Weigel is a senior fellow of the Ethics and Public Policy Center in Washington, D.C.