(1) Immigration from countries where jihadist sympathy is high; (2) Turkey and the E.U.

There's a hot debate over what Western countries should do about immigration from countries where jihadist sympathy is relatively high (not necessarily a majority, but a considerable minority). I'm not sure what the right answer is.

On one hand, I don't like excluding good people, or even treating them differently, because of the evil attitudes (and possible evil behaviors) of their compatriots. That's not how I'd prefer that our government treat people. And excluding immigrants on this basis can deny the United States many prospective future Americans who can help promote America's prosperity, influence and greatness. Indeed, when it comes to action within the United States, the government generally can't discriminate against people based on their national origin or the views of the people who share that national origin. That's generally a good approach, and while it doesn't categorically carry over to immigration decisions, there's much to be said for it.

On the other hand, I don't want to let in people who will either commit terrorist acts (or help others who do) or who may push my nation's policies in a bad direction. When you let in immigrants, you are letting in your future rulers—especially because you're letting in their children (present and future) and their children's children. This concern is especially strong to the extent that one's country has abandoned a focus on assimilating immigrants and has instead focused on fostering multiculturalism (though of course even a policy of assimilation has never been complete, especially as to religious minorities). And it is also especially strong for smaller countries than the United States, where even a few hundred thousand immigrants might make a big difference, especially in particular areas. This might counsel in favor of sharply limiting immigration from such countries, whether by instituting very demanding screening mechanisms, allowing only immigration by people with professional skills that are needed in the United States, capping the total immigration from a country or something else.

Let me offer one way of thinking about the problem, and ask you, our readers, what you think about it:

Turkey has long wanted to join the European Union. Its recent political instability and repression seems likely to take this off the table for now. But say Turkey gets over that, has free and democratic elections, and ends up looking relatively stable and democratic at least for a modest time.

Now Turkey is overwhelmingly Muslim, and it's a big country—with 75 million people, or the equivalent of 15 percent of the E.U.'s population of 500 million. And assume that, if Turkey joins the E.U., Turks will be free to move to any E.U. country and to become citizens of any E.U. country. (That's a bit of an oversimplification, as I understand it, but assume that this will end up being so, since I suspect that as a practical matter it will be fairly likely.)

The decision to include Turkey would thus affect European politics much as open immigration from Turkey would. First, Turks would become more easily able to immigrate to European countries, which would affect the politics of those countries. Second, Turkey's accession into the E.U. would be tantamount to the immigration of all Turks into the E.U. (even if not into particular countries in the E.U.) and would thus affect E.U. politics. (One distinction between the Turkey/E.U. issue and the immigration issue, of course, is that one can decide whether to allow immigration on an immigrant-by-immigrant basis, whereas letting Turkey in is all-or-nothing. At the same time, there are limits on the ability to really carefully investigate each would-be immigrant.)

Turkish Muslims also appear to have relatively little sympathy for jihadists; but there is a small percentage—but a large number, given Turkey's large population—that does seem to have such sympathy. A 2013 Pew Research report, for instance, reports that 23 percent of Turks thought that "suicide bombing and other forms of violence against civilian targets" could be "justified in order to defend Islam from its enemies," either often (3 percent), sometimes (12 percent) or rarely (8 percent); 70 percent said this could never be justified. This is an imperfect marker of jihadist sympathy, to be sure, but it's one such marker; let's use it for now.

Which of the following would be your view?

1. When E.U. residents and politicians are deciding whether to let Turkey join the E.U., it's illegitimate for them to consider how many Turks sympathize with jihadists. Such judgments based on people's attitudes—especially attitudes closely tied to religion—are improper, even in such foreign policy decisions. Even if there had been more support for jihadism in Turkey, that couldn't be considered in deciding whether to let Turkey in. And if you think this about the Turkey/E.U. accession decision, you'd presumably also think this as to decisions about whether to allow immigration from countries, even those where the support for jihadism is higher.

2. E.U. residents and politicians can legitimately consider, in this context, how many Turks sympathize with jihadists, but the actual numbers are so small that they shouldn't prevent allowing Turkey into the E.U. Had the numbers been much larger, then Turkey should indeed be not allowed into the E.U.

Suboptions: (A) It's likewise legitimate to consider such statistics when deciding whether to allow immigration from countries, such as Egypt, where the support for jihadism is materially higher (the answer to the suicide bombing question in Egypt, for instance, was 11 percent often, 18 percent sometimes, 28 percent rarely, 40 percent never). (B) Even though such statistics are legitimate to consider as to the Turkey/E.U. accession question, considering them is not legitimate as to immigration from particular countries.

3. E.U. residents and politicians can legitimately consider, in this context, how many Turks sympathize with jihadists, and the numbers are large enough that the E.U. shouldn't allow Turkey to join. As to deciding on immigration from particular countries, same suboptions A and B as in item 2 above.

I'd love to hear your thoughts on this and, of course, especially your brief explanations for your conclusion.