A European at this Christmas season must feel a little like a Roman enjoying one of the last Lupercals of the pagan era. The old religion still fills the public space of society. It still possesses its old wealth and the great temples in the centres of towns, and national leaders still profess their adherence to its teachings.

Elites still disdain the old religion’s new eastern competitor, the religion of migrants and the poor. Its houses of worship are found in cheap suburbs, far from the pomp and glitter of the central cities.

The new competitor’s holidays are ignored by the state and observed only by its own believers. But every year there are more and more of them.

The great historian Bernard Lewis has predicted that at current trends, Islam will replace Christianity as Europe’s predominant religion within the next 50 years. Some skeptics doubt this prediction. They argue that Europe’s Muslim population must succumb to the same forces of modernization and secularization that have emptied Europe’s Christian churches.

Perhaps these skeptics are right. But whether Europe is fated to move toward an Islamic future or a secular one, equally post-Islamic and post-Christian, there is one future predicted by nobody: a revival of the ancient Christian faith that defined European civilization for 1,500 years.

Whatever the future holds, nobody should assume that the transition from one era to the other will be peaceful or easy. Last month’s Muslim rioting in France, this month’s clashes between old-stock Australians and Muslim immigrants on the beaches of Sydney—these may well be portents of a troubled future. It took only a century for the rulers of Rome to switch from persecuting Christianity to banning its rivals.

I belong to a religious community often and horribly persecuted by European Christianity. Under Islam, by contrast, Jews were usually tolerated and sometimes even protected. Does the history of the past offer any comfort for the future?

Only if we believe that the Islam of the future will resemble the Islam of the past. And the evidence indicates pretty strongly that this will not be so.

The anti-Jewish incitement preached in contemporary mosques, the surge of anti-Jewish violence in European cities with large Muslim minorities, the Holocaust denial urged by the governments not just of Iran but also of Egypt and Saudi Arabia, the blunt threats of nuclear annihilation of the Jews heard from the government in Teheran—these tell us more about what is to come than the benign practices of the lost Muslim past.

And here in North America, the omens are likewise ominous. It remains impossible to obtain an unequivocal denunciation of anti-Jewish violence from the major North American Islamic groups. When a federal jury earlier this month deadlocked at the trial of Sami al-Arian, the alleged head of Palestinian Islamic Jihad in the United States, major Islamic groups like the Council on American Islamic Relations hailed the verdict with only a discreet cough over al-Arian’s “sometimes controversial” views—and an endorsement of his “right to hold opinions not shared by the majority.”

The Muslim Political Action Committee likewise applauded the non-conviction of al-Arian despite a “negative political environment.”

And what were those “sometimes controversial views”? On Jan. 22, 1995, two Islamic Jihad suicide bombers detonated themselves at an Israeli bus stop, killing 19 people and wounding 65. On Feb. 1, 1995, al-Arian signed a fundraising letter seeking money so that operations like that committed by “the two mujahedin who were martyred for the sake of God” could continue. This may not necessarily have been illegal—the U.S. law banning fundraising for foreign terrorist organizations would not be enacted until later in 1995. But legal or illegal, it expresses a murderous anti-Semitism against which no major North American Muslim group has raised its voice.

Life in Christian societies has seldom been easy for Jews. But even at its persecuting worst, Christianity always acknowledged its own descent from Judaism—and always preserved a place for Judaism, if not for Jews, in its theology and teaching.

Islamic theology, by contrast, taught that the Jews deliberately falsified the Torah and the Bible to conceal the fact that Abraham was a Muslim who lived in Arabia and preferred Ishmael over Isaac. It carried over large passages from Jewish scripture directly into the Koran and other sacred writings while furiously denying any connection with the Jewish past. However kindly Islamic societies have treated Jews, Islam the religion has no place for Judaism.

Combine the hostility to Judaism taught by Islamic theology with the hostility to Jews felt by contemporary Muslim societies—and you arrive at a frightening conclusion: When the Christian era draws to its end in Europe, so too will end the era of European Jewry.