They still haven’t got it.

European media and policymakers have correctly realized that the present refugee crisis is an enormous challenge to the assumptions that have guided the continent for decades, to the point of potentially breaking the European Union. But apparently they still are not prepared to confront the specifically religious revolution now under way.

This issue places me in a strange and unprecedented position. Over the past decade, I have written about the presence of Islam in Europe, arguing repeatedly that the threat of “Islamization” is overblown. Overall, I have argued, Europe’s Muslim population is presently around 4.5 percent of the whole, which by U.S. standards is in no sense a massive minority presence. It might rise to 10 or 15 percent later in the century, but the change will be gradual, allowing plenty of time for assimilation.

My moderate position on this has been heavily criticized by various right-wing outlets such as FrontPage Magazine, a publication with which I agree on basically nothing. On most issues, I find FrontPage’s tone hysterical and alarmist. Now, suddenly, I myself have to criticize that magazinefor being insufficiently concerned about Islam. These are strange times.

Here is the problem. Germany recently declared that it would take 800,000 refugees this year. That is a very large figure, but as the government points out, that is only one percent of the population of 80 million. In FrontPage,Daniel Greenfield stresses that the issue is much graver than it appears, since the refugees are mainly young men, who will massively raise the Muslim presence among that section of Germany’s population. Other writers likeChristopher Caldwell also raise alarms about the massive security threats posed by the present crisis. He warns that European politicians “are trying to pass off a migration crisis as a humanitarian crisis. It may be on the verge of turning into a military crisis.”

Both Greenfield and Caldwell are right, but they are still missing large parts of the story, which are available to anyone who has followed German media over the past two weeks. The first point made repeatedly by German officials and journalists is that no sane person really believes in that 800,000 figure for this present year. Even as Germany has introduced “temporary” border controls in the past few days, the estimates for the actual number of migrants expected continues to grow.Vice Chancellor Sigmar Gabriel now tells his party that, “There are many indications that in this year we will not see 800,000 refugees, as predicted, but a million.”

Also, such officials are explicitly saying that something like this influx will continue more or less indefinitely. Sigmar Gabriel has also said that “we could certainly deal with something in the order of a half a million for several years.” If the present experience is anything to go by, that is likely to mean something like a million a year for how long? Five years? Ten?

However obvious this may be to say, there is no logical end to this process, even if the Syrian crisis ended tomorrow. As it becomes known that Germany is so open to migrants, that fact offers an irresistible invitation to anyone living in a country roiled by violence or economic crisis, which basically means most lands from Libya to Pakistan. There is no terminal point at which the nations sending migrants would ever run out of candidates seeking refuge and asylum. And even that projection takes no account of the likely spread of open warfare and terrorism into Turkey and Egypt in the coming decade.

So let’s put those numbers in context. Germany’s population is about a quarter that of the United States, so multiply all those refugee figures by four. Imagine if a U.S. president declared that the country would commit itself to taking between two and four million new refugees and migrants, annually, over the coming years—and that over and above other forms of immigration. Even given the diversity of the U.S. population, that would represent an inconceivably large social transformation.

Germany is also describing an epochal religious revolution. That point might not be clear from reading the very extensive articles in mainstream German media that discuss every aspect of the strains posed by the crisis, but somehow never mention the words Islam or Muslim. That reticence is understandable, given that Germans, more than any people, do not want to appear nativist or racist. But despite the taboos, that religious element is critical.

Who are the immigrants? On the good side, a sizable number are Syrians who are fleeing the rise of radical Islamism in their country because they are themselves non-Muslims, or at least non-Sunnis. Before the present post-2011 meltdown, perhaps 40 percent of Syria’s people fell into the various non-Sunni categories, including a great many Christians. Their presence in Germany might actually strengthen Christian traditions.

But these non-Sunni migrants will be an ever-smaller component of a migrant wave that is increasingly and overwhelmingly Muslim. Many of the present migrants are not in fact Syrian, and they adopt that description to win the sympathy of host nations (a thoroughly understandable decision). Many are in fact Iraqis and Turks, Libyans or Afghans. All those groups, incidentally, come from countries with very young populations and extremely high fertility rates, so their numbers would likely grow rapidly in their new European homes.

Before 2015, Germany’s Muslim population was around 5 percent of the whole, potentially rising to 7 percent or so by 2030. If the present wave of migrants and refugees continues, that figure could well be 15 or 20 percent by the 2030s, and it would be rising fast. For the first time ever, we would seriously be looking at something like the Islamization of Europe that has been a nativist nightmare for a generation. And in the German context, that process would be squeezed into just a couple of decades. That is radically destabilizing.

Personally, I don’t believe that the presence of Islam in Europe need of itself be harmful or even negative, nor that it would necessarily lead to violence. But I am quite certain that numerical changes on this scale do portend a cultural and social revolution without precedent.

Shouldn’t the Germans, and other Europeans, at least be allowed to discuss this openly?

Philip Jenkins is the author of The Many Faces of Christ: The Thousand Year Story of the Survival and Influence of the Lost Gospels (Basic Books, forthcoming Fall 2015). He is distinguished professor of history at Baylor University and serves as co-director for the Program on Historical Studies of Religion in the Institute for Studies of Religion.