Smart, intellectually consistent cases for immigration restriction are in short supply these days. U.S. President Donald Trump’s voters claim that the president only wants to stop illegal immigration, even as Trump’s policies take aim at the legal variety. Fringe figures on the right resuscitate century-old arguments about the inferiority of non-Western cultures or make poorly supported claims about the perils of racial diversity, even as the president sneers at immigration from “shithole” countries.

Given its provocative title, one might expect Reihan Salam’s new book, Melting Pot or Civil War? A Son of Immigrants Makes the Case Against Open Borders, to be yet another jeremiad warning that modern immigrants—unlike those good immigrants of ages past—are failing to assimilate and that race war looms. In fact, it is something completely different: a thoughtful, well-informed, mostly economic argument for limiting low-skilled immigration. In a marketplace of ideas dominated by shouting and bad faith, Salam’s book, although not without its flaws, is a much-needed injection of calm rationality.

AN OPEN-AND-SHUT CASE

Salam’s case for immigration restriction is fairly simple. Mass immigration of low-skilled laborers—farm workers, child-care workers, gardeners, and so on—will create an economic underclass in the United States. In the past, waves of poor laborers from Ireland, Italy, and elsewhere eventually clawed their way to the middle class, but this time, Salam says, will be different. The rise of automation and globalization means that low-skilled labor will be devalued as never before—gone will be the good manufacturing jobs of yesteryear, replaced by insecure, low-paid work. The children and grandchildren of today’s low-skilled immigrants will become a permanent pool of surplus labor.

Salam prophesies that the negative consequences of this will go beyond mere economic inequality. Because most low-skilled immigrants to the United States, indeed most U.S. immigrants in general, are nonwhite, many of them from Latin America, there will be a racialized aspect to the underclass. When generation after generation of poor Hispanic Americans find themselves unable to catch up to prosperous whites, society will fracture along racial lines—the “civil war” referenced in the book’s title.

In order to avert this disaster, Salam calls for policies to shift the mix of U.S. immigration from low-skilled labor to the higher-skilled variety. Immigrants who come with the education, money, or smarts to succeed in the U.S. economy—and to pass that success on to their descendants—will help restore the legendary “melting pot” of the days of old, as Salam argues that economic assimilation leads to cultural acceptance.

This argument stands out from those of many other immigration restrictionists for several reasons. It clearly springs not from racial animus but from humanism and patriotism. Salam is obviously concerned for the welfare of the poor and the cohesion of American society. He eschews common tropes, talking points, and buzzwords and instead reveals a deep knowledge of the academic literature. Salam’s proposed solution—a system that admits prospective immigrants based on skills instead of family ties—is good policy. In short, if you read one book making the case against increased immigration, Melting Pot or Civil War? should be it.

There is certainly some evidence to support Salam’s basic thesis. The children of Hispanic immigrants do tend to close part of the income gap with whites, but then the convergence stops and the ethnic gap persists. In contrast, Asian immigrants—many more of whom were selected for their skills rather than their proximity to the United States—tend to surpass whites in earning power by the second generation. It matters who comes. There’s also evidence that skilled immigrants are much more quickly accepted by the native population in many countries, reducing the chances of a nativist backlash. Then there’s the salutary example of Canada, which has focused on taking in skilled immigrants from a wide variety of sources, and which so far, at least, has not suffered the same kind of nativism now gripping the United States and several European countries.

Then again, Salam’s narrative—low-skilled immigration leading to a racialized underclass and social strife—doesn’t seem to describe the U.S. experience in recent decades. The late 1960s and the early 1970s were a time of great social chaos. Riots torched the hearts of Chicago, Los Angeles, Detroit, Newark, Washington, D.C., and other U.S. cities. Violent crime soared to heights unmatched anywhere else in the developed world. Hundreds of bombings rocked cities across the country every year. But those were decades in which the U.S. foreign-born population was at an all-time low. In contrast, the 1990s and 2000s—when the foreign-born population soared again—saw plunging crime rates, an apparent end to large-scale rioting, and a relative lack of interest in radical politics. The big cities most transformed by Hispanic immigration, such as Houston, Los Angeles, and San Diego, became far more peaceful than before (a fact Salam acknowledges in the case of his own New York City). This seeming negative correlation between the number of immigrants and social breakdown, although it doesn’t disprove Salam’s basic idea, should make us hesitant to accept it as an overarching theory of social division.

And if the problem is not the number of immigrants but the mix of skills they bring, Salam’s book seems curiously timed. Net immigration from Latin America, particularly from Mexico, collapsed about a decade ago and, thanks to low fertility rates and rising per capita GDP throughout the region, is unlikely to bounce back. The average education level of people moving to the United States has risen rapidly; immigrants are now considerably more likely than their native-born counterparts to have a bachelor’s degree. Salam mentions this trend but, strangely, gives it little consideration.

If the problem of mass low-skilled immigration was a one-off, driven by temporarily high fertility rates and poverty in Latin America combined with the long, porous U.S.-Mexican land border, why worry about it now? Salam does not call for a Trump-style mass expulsion of undocumented immigrants; in fact, he wants a general amnesty. So why shouldn’t we regard the low-skilled immigration boom of the 1980s, 1990s, and early 2000s as a problem already solved? Salam could have made a case that rapid population growth in Africa will eventually create another wave of immigration pressure, but he misses this opportunity. As a result, an unanswered question hangs over the book: Why is immigration still worth worrying about at all?

Another weakness of this book stems from its intended audience. Salam spends quite a lot of time rebutting the idea of “open borders.” But except for a few progressive firebrands, essentially no one on the political left is explicitly advocating for the abolishment of all immigration restrictions. The open borders case is instead a darling of intellectual libertarian circles. Much of Salam’s case seems directed toward these libertarians—for example, rebutting the idea that open borders are the best way to help the world’s poor.

But although they might be common in Salam’s elite conservative circles, libertarian intellectuals are a nonfactor in national politics, marginalized on the right and almost unknown on the left. Thus, Salam’s message seems sometimes ill tailored to the broader immigration controversy. He occasionally gets lost in the weeds of complex economic arguments, spending a fifth of the book speculating about the impact of automation and another full chapter discussing alternative ideas for helping the developing world. This is stimulating stuff to a policy wonk but makes the book feel a bit less broadly relevant.

A better approach would have been to argue that pro-immigration activists on the left, despite not explicitly endorsing open borders, are creating a de facto open borders standard by opposing every concrete attempt to restrict low-skilled immigration. That case was certainly there for the making—after all, if every attempt to enforce borders falls before a moral outcry, do borders really exist?—but Salam misses the chance to make it.

FITTING IN

Because Salam focuses so much on the economics of immigration, he also misses the chance to make a more subtle, cultural argument for closing the gates. The most poignant passage in the book comes in the introduction, when Salam, whose parents are Bangladeshi immigrants, recalls feeling ucomfortable and afraid after a terrorist attack by Akayed Ullah, a Bangladeshi radical in New York City. Although no one persecutes Salam because of his ethnic similarity to the terrorist, he nevertheless sees uneasy similarities between Ullah’s background and his own, and he worries that the problems in Ullah’s life reflect broader failures of integration. This anecdote hangs over the rest of the book, posing an unspoken question: If immigration were cut off, would people like Ullah find it easier to assimilate into American society?

With continued Bangladeshi immigration, even of the high-skilled variety, Bangladeshis might always retain some connection to that ethnic expatriate community. That connection would be both a blessing and a curse, as it might result in some white Americans, or members of other more well-established groups, regarding Bangladeshi Americans as perpetual foreigners in their own land. But if immigration from Bangladesh ceased, then over time, Bangladeshis might become well established in their own right, just as Germans, Italians, Irish, and other groups once did after immigration from those countries trickled off—and the idea of associating them with Bangladeshi nationals would come to seem ludicrous.

Salam doesn’t base his case for restriction on the notion of accelerating the melting pot for the descendants of skilled immigrants—indeed, he calls for continued high-skilled immigration. Still, the idea is always in the background. Would cutting off all immigration—not just the low-skilled variety—cause xenophobia and racism against Asian Americans, Hispanic Americans, and other such groups to fade, forging Americans of all races into a new, unified identity? Or would restrictions effectively declare Asians and Hispanics to be undesirables, forcing them to endure a painful, submissive half assimilation into a white mainstream that would never quite accept them?

I don’t have an answer to that momentous and painful question. And it’s a shame that Melting Pot or Civil War? never attempts to tackle it, because without that cultural dimension, the book isn’t quite as bold or as personal as its subtitle implies. It’s the son of high-skilled immigrants making a complex economic argument that U.S. immigration should look more like his own family. There’s nothing wrong with that—indeed, Salam’s arguments for shifting to a more skills-based immigration policy are strong ones. But as the Trump administration takes steps to keep out skilled immigrants, it would be nice to know where Salam stands on the issue.