This week, Angela Merkel proclaimed that Germany is a Christian nation and that the Muslim faith doesn’t really have a place in it. Ferdinand and Isabella made a similar declaration about Spain about 500 years ago before conquering Granada and driving the last of the Muslims off of the Iberian Peninsula.
We are still pretty clumsy when it comes to religion in the West. Maybe we'd do better going back to the distinction between objective and subjective reality than talking about which religions should be allowed and which should not.
Subjective reality is the domain of religion. It is the domain of personal revelations and convictions, opinions, tastes, and personal values. The experience of subjective reality is a large part of what it means to be human. No humane society can dismiss it or claim that it isn't "real."
What has made the West since the Enlightenment such a wonderful place to live is that this subjective reality is subordinated to objective reality. The objective realities of science, democracy, and economics define our modern world.
The subjective colors what scientists study, but good science means testable hypotheses. Science is objective. The subjective influences how people vote, but in a democracy it is votes that can be counted that determine what politicians hold office and what policy becomes law. Democracy is objective. And finally, the subjective influences what people do for a living or what goods and services they buy, but it is dollars that can be counted that determine which careers are funded and which goods are made. Economics, too, is objective.
Although the West rests on the subjective, it is objective reality that has the final vote in defining our world.
And that, it seems to me, is all that matters. As long as any subjective reality - from Christianity to Islam to atheism - only has access to the public realm through the front door of objective reality, we're likely to live in a "good" society.
And this leads to the conclusion that is rarely made. During the Enlightenment, Christianity was radically redefined. It was no longer the force that Constantine defined as the basis for rule; instead, it became a way that people made sense of their individual lives. Christianity - once the basis for theocracy as oppressive as anything found in the history of Islam - was reformed. To become fully a part of the West, Islam will have to go through a similar re-definition. Turkey alone proves that this is not impossible, much less the presence of so many Muslims living peacefully in the West.
This is not a matter of getting the right subjective reality. This is simply a matter of never letting any subjective reality rule over objective reality. It is this more than the particulars of religion that form the basis of the modern West.