Jeb Bush has proposed only admitting Christian Syrian refugees. On the face of it, it’s an obnoxious, bigoted suggestion, a clear violation of the fundamental principle of separation of church and state, and flies in the face of all this country stands for. But what if he’s right?

The problem is not so much that some of the refugees could be terrorists, although that’s certainly a possibility, e.g., the Tsarnaev brothers, as it is that they could form a potential breeding ground for future terrorists. The risk is second-generation terrorists. That seems to be the case in many of the terrorist acts in France, where those involved aren’t from the Middle East but from Belgian and Parisian tenements. Those terrorists may carry Belgian and French passports, but they self-identify based on religion or tribal affiliation, not with the country in which they were born.

That’s hard for us to get our heads around, because for the most part, we self-identify with geography. Although most of us have token affiliation with other identifiers, e.g., we still live in a predominantly Asian neighborhood or attend the Greek Orthodox Church or march in the St. Patrick’s Day Parade, if asked our first descriptor would likely be our Westphalian identity, i.e., “I am an American.” But this is a relatively new concept. If you’d stopped someone walking down the road five hundred years ago and asked him who he was, he’d have answered with the name of his local duchy or his tribe or his religion. Country wouldn’t have even been on the list. And in many parts of the world with strong tribal divisions still intact, that’s still the reality.

Unassimilated groups are a problem. I realize that flies in the face of high minded talk about diversity and all of that, but the truth is unassimilated groups have a very long history of eventually either becoming villains or victims. The Scots-Irish in the U.S. remain surprisingly unassimilated after three hundred years, and are still committing villainous terrorist acts with some frequency. Blacks in the U.S. and Jews in Europe, and sometimes Muslims in places like Serbia, tend to find themselves victims, especially when the economy goes bad. In Europe they’ve historically blamed Jews for hoarding money leading to economic downturns. In the U.S. it’s blacks and entitlements leading to the debt crisis. But it’s the same basic idea.

So it boils down to a simple question: Will the refugees we accept assimilate, adopting the predominant views of tolerance and avenues to social mobility, or will they remain unassimilated like the Muslims in France, undigested like lumps in oatmeal? If they will assimilate into the U.S., as most previous ethnic groups have done, then there’s no reason at all not to take in as many as we can absorb (plenty of room in North Dakota.) If on the other hand, they will not assimilate, then we should limit the number we accept and be very selective about those.

That obviously begs the question, then, what causes one group to assimilate and another to stay separate? Well, in some cases it’s not group-to-be-assimilated’s fault. African-Americans have tried many times to assimilate and have been rebuffed. That many have now given up and decided to exist in their own parallel culture is less an issue of not wanting to assimilate than it is an issue of not being allowed to.

But in other cases, the non-assimilation is at least by choice. Those in the group choose to keep their own language, dress, and customs, and to live in tightly defined communities. I do not have the statistics, but I suspect that is most often the case when they bring with them their own religion. Vietnamese and now Mexican immigrants seem to have assimilated relatively well, but for the most part they’re Christians. They may be Christians of a different sort and it may take some time to work them in, as was the case with Catholics in the 1800’s, but the assimilation process has worked. Other groups have been here just as long, but still maintain a much higher level of separateness. Jews have assimilated partially. Those sects that are less extreme in their religion have assimilated, but those that have very strict dress codes, customs, etc have not. Even the moderates still tend to maintain some level of reluctance to assimilate, e.g., wearing yarmulkes or insisting on marriage to those within the religion.

And again, sooner or later, unassimilated groups are often a problem. For the majority of the population or for them. Either they’ll become resentful at being marginalized and commit criminal or terrorist acts, or they’ll become a target on which society can take out its frustrations.

I’m not a Christian and I think Christianity has at least as much to answer for as Islam. They’re both aggressive, controlling, dangerous belief systems, and because followers are taught to adhere based on faith instead of logic, both religions are prone to being hijacked by assholes. However, it may well be that any country can only tolerate one such belief system at a time. By dint of history, the dominant belief system in America is Christianity, and as unpleasant as the implications of that are, the pragmatic truth may be that we should use religion as a screening criteria for immigrants.