Many of the politicians who think the US should stop accepting Syrian refugees have put forward an elegant-sounding alternative: Syrian refugees should simply be housed in neighboring countries instead. After all, other Middle Eastern countries are both geographically closer and — at least in the eyes of US politicians — culturally similar to Syria, so it makes sense to keep refugees somewhere they'll be more comfortable.

Ted Cruz has endorsed this solution: "We should be resettling them humanely in Middle Eastern countries that are majority Muslim," he said last week. Donald Trump has endorsed a (much weirder and much less clear) version: He wants a "safe space" cleared in the Middle East for Syrian refugees, somehow paid for by Saudi Arabia. Wyoming Rep. Cynthia Lummis was one of several House Republicans who said this week that it would be more "humanitarian" to keep Syrian refugees "close to home" than to allow them to come to the US.

There's one problem with this plan: It's more or less what's happening already. The overwhelming majority of Syrians who have fled their home country aren't being permanently resettled in the US, Europe, or anywhere else. They're being held in "temporary" refugee camps — many of which have been open for several years— in neighboring countries.

It's funny that politicians aren't acknowledging these camps, because they're the main source for refugees who eventually come to the US. The UN Office of the High Commissioner for Refugees identifies possible refugees the US might be willing to take in and refers them to American officials. That kicks off the 18-month to two-year screening process that (with luck) results in a refugee coming to the States. It's the failure of those camps, in large part, that's led so many Syrian refugees — some of whom have left refugee camps — to try to seek asylum in Europe, overwhelming European border officials, creating security risks, and causing the US's current refugee freakout.

Most Syrian refugees are staying in the region

Of the 4.2 million Syrian refugees, the overwhelming majority are in three countries: Turkey, Lebanon, and Jordan. All three of those are majority-Muslim countries, all of them border Syria, and (depending on your definition) all are in the Middle East.

As you can see from the graphic above, the number of refugees the US is even considering accepting — let alone the (much lower) number it's actually on pace to accept — is a drop in the bucket compared with the refugee burden other countries are bearing. But there is a very important difference between the two. In the UN's terminology, Turkey, Lebanon, and Jordan are "second countries" — they're the places refugees flee to when they're leaving Syria. The US (and other countries resettling Syrian refugees) are "third countries" — countries that deliberately agree to take on refugees to live there permanently.

Temporary refugee life is often miserable enough to be worth risking life and limb to leave

Resettlement in third countries is resource-intensive because it's supposed to be permanent: Refugees need housing, financial support, language training, and, eventually, a job. Meanwhile, in the places refugees initially flee to, the goal is to keep refugees alive and relatively safe until they can return to their home countries — or, failing that, until they can successfully integrate into the country they happen to be in.

Specific proposals, like Cruz's, acknowledge this difference: Cruz wants refugees resettled, he just wants it to happen in other Middle Eastern countries. There is a legitimate critique there: International human rights organizations have condemned rich Gulf countries like Saudi Arabia for not agreeing to resettle enough (or any) Syrian refugees. (The countries in question have presented their own stats arguing that they are, in fact, hosting Syrian refugees; the NGOs don't think those stats are reliable.) But it's not clear to anyone (except perhaps Donald Trump) how the US refusing to accept Syrian refugees would induce Saudi Arabia to start accepting them. After all, there are so many refugees not being resettled now that the US refusing to resettle any wouldn't add much to the total.

The problem is that not all countries that have to deal with millions of refugees want to integrate them, or are even able to do so. There's a lot of variation in how the countries with the most Syrian refugees are dealing with their refugee populations: Turkey is slowly beginning to allow Syrians to work in Turkey, for example, while in other countries camps are essentially locked away from the outside world. That puts the UN (and wealthier countries) on the hook for feeding and housing the refugees indefinitely. Nor is refugee-camp life something any refugee wants to lead forever. Living in temporary shelter, being fed by an international organization, and never getting a job? It's better than living in Syria, but it's not something anyone wants to do for the rest of her life.

It's true that most refugees would rather be in their home countries safe and sound, but very few refugees are interested in living out their lives in a UN tent city. Presented with the opportunity to make a better life for themselves elsewhere — whether that's applying for resettlement in the US or another country or crossing into Europe without papers — many of them take the chance.

Europe is struggling to screen asylum seekers because there are so many of them — many of whom have left refugee camps

Some of the refugees who have come into Europe over the past year, both over the land route in the Balkans and by crossing the Mediterranean Sea, have journeyed directly from Syria without trying to live anywhere else. But many of them have been registered refugees living in Turkey, Lebanon, Jordan, etc. They decided it was worthwhile to give up their protected refugee status under the UN by leaving their camps or countries — and risking their lives on a dangerous border crossing — just for the hope of making it to Europe. That should give you some idea of how terrible conditions are for many Syrian refugees in the region — or just how compelling the prospect of making a permanent better life for yourself is, compared with the ongoing uncertainty of refugee life.

But not all people coming into Europe are from Syria, or are refugees. This is where the difficulty comes in. People don't sort themselves into easy buckets of "legitimate refugees," "economic migrants," and "infiltrating terrorists." Countries have a humanitarian obligation to accept refugees who seek asylum in their countries, regardless of whether they have legal status in the country when they arrive. Their laws and national security obligate them to reject the other two groups. So Europe — just like the US did last summer, when large numbers of Central American families entered the US to seek asylum — has to figure out how to separate legitimate refugees from everyone else.

That's not an easy process under the best of circumstances. It's certainly not easy for Greece and Italy, the two countries that have been most overwhelmed by refugees and migrants over the past couple of years. Both Greece and Italy have had their own issues as countries, and neither of them has anywhere near the resources required to vet refugees thoroughly, house and monitor everyone while tracking is completed, issue papers to the refugees who check out, and deport the ones who don't.

The fewer permanent options refugees have, the worse the security problem at Europe's borders will get

The EU has been struggling to solve the problem of screening refugees effectively and humanely, but it certainly hasn't solved it yet. As a result, Greece and Italy simply aren't capable of screening refugees well enough to prevent potential threats from coming through. That's been demonstrated by the Paris attacks of last week: none of the attackers have yet been identified as Syrian refugees (although one is known to have crossed into Greece using a forged Syrian passport), but the presumed planner of the attacks, a Belgian native who'd been fighting with ISIS in Syria, was able to get back into Europe before the attacks without being apprehended by the authorities.

It would be a lot easier for Greece and Italy (and other European countries) to deal with migrants if they were confident that nobody coming in was a legitimate refugee. But they can't be confident about that — many, if not most, of them are. And that's because the options that are already available to them in the Middle East are simply so unappealing that they are willing to take the risk.

Those options, it's important to note, include the possibility of getting to resettle in the US. Very few Syrian refugees even get flagged by UNHCR for potential resettlement in the US — the UNHCR has only referred about 22,000 refugees to US officials. But that's still 22,000 people who have a very strong incentive to stay where they are, because if they leave the UN camp (for example) they're registered in, they lose their refugee status and their shot at resettlement. If the US were to unilaterally declare that it was going to stop taking Syrian refugees, those 22,000 people would have much less reason to stay put rather than taking their chances in Europe.

The irony of America's refugee-centric response to the Paris attacks is that Europe really does have reason to be concerned about who's coming into the continent from the Middle East — because it's so hard for European countries to process the tens of thousands of people coming in. The US refugee process is entirely different: It takes place far from the US itself, it has the luxury of taking years to conduct security checks, and the US can refuse to accept a refugee for any reason (whereas someone claiming asylum can't be sent back to a country that could persecute her).

The US isn't accepting enough Syrian refugees to solve the crisis; there are still millions of people forced to choose between indefinite temporary life in Turkey or Lebanon and the risky reward of asylum in Europe. But if the US accepts zero refugees, that crush of people will only get worse — and Europe would have even more trouble telling the "legitimate" refugees from everyone else.