Bryan Caplan frequently draws parallels between open borders and natalism. The comparison is intuitive: If we accept the argument that more people are a boon to society, then it follows that we can enjoy that boon whether newcomers are infants or immigrants.

Critics of immigration, however, frequently cite sundry “differences” between locals and foreigners as reasons why immigrants qua newcomers might be less of a boon – and indeed, more of a bane – than babies qua newcomers.

One of the reasons that I, personally, find the critics’ reasoning unpersuasive is that any trait that might convince me to deny an immigrant entry into the country is a difference that likewise ought to convince me to deport any native who held the same trait. In other words, I believe that differences between populations ought to count as much as differences across populations.

Why so?

The first reason is a simple matter of prejudice: If you believe a low-IQ “Ruritanian” is more destructive to American life than a low-IQ American, then it’s hard to avoid allegations of overt racism. Perhaps “there is more to it than that,” but if so, then the real problem isn’t actually the person’s low IQ, but rather whatever “more” there might be “to it.” Low IQ becomes a red herring, and the real issue becomes a prejudice against “Ruritarians.” If the issue is IQ – or any other particular difference – then the issue must apply equally to natives and immigrants alike. If it doesn’t, that is strong evidence of prejudice.

Another reason is a matter of empirics: Before we can even consider designing immigration policy around the differences that exist between human beings, we must first establish the following:

That the differences between people really do translate into a reduced quality of life. That locals are inarguably more different from foreigners than they are from other locals. That the government really is capable of testing for these proven differences in a way that does not threaten the rule of law for locals and immigrants alike.

Point #1 is often taken on assumption, but it ought not be. For one thing, it calls into question why any immigrant would choose to emigrate from his/her fellow natives in the first place, since the differences s/he will encounter abroad supposedly make life worse for him/her, not better. For another thing, while it’s easy to merely allege that “the immigrants” caused crime to increase in your neighborhood or property values to decrease, it is substantially more difficult to prove it. I leave the burden of proof for Point #1 on immigration’s critics.

Moreover, that proof of Point #1 must necessarily account for Point #2. We must not only prove that, say, “religious differences” adversely impact local life, but also that I am more religiously different from a Russian immigrant than I am from my neighbor. A proof for Point #1 must also account for the many positive attributes brought to a community by outsiders, including (but not limited to) cultural benefits like food, music, and literature; friendship; genetic diversity, which as a matter of pure biology strengthens the population of any species; comparative economic advantages; and so on.

Proving or substantiating Points #1 and #2 should be extremely difficult considering the high degree of cosmopolitanism in countries that are attractive to immigrants. Today, the United States, the United Kingdom, Australia, China, Spain, Singapore, etc. are more cosmopolitan than at any other time in human history. The extent to which we are different from our neighbors has never been greater than it is today. This suggests that differences have more positive effects than negative effects, and that the residents of immigrant-friendly nations don’t seem to let their differences get in the way of a high standard of living.

Point #3 is an extremely high hurdle to clear for practical reasons. It involves first proving Points #1 and #2, and then demonstrating that we can indeed detect these differences reliably and empirically. Once we’ve managed to clear this hurdle, we must wrestle with the problem that any power transferred to the state for legitimate reasons is power that can potentially be abused.

This brings me to my third and final reason why differences within a population must matter as much as differences among different populations. If, as some have suggested, social contract theory entitles a nation’s government to sculpt the cultural make-up of its citizens, then deporting native cultural chaff is no less logical a method of doing so than refusing to import foreigners who hold the same traits. Assuming we manage to prove that differences are problematic, and that we can reliably test for them, doesn’t this imply that we can take action against our fellow natives just as easily as we can against potential immigrants? Why not deport all troublemakers?

If this suggestion makes you uneasy, I can understand why. Historical examples, such as Stalinist purges and various acts of genocide seen throughout history, give us reason to think twice. I’m obviously not suggesting that we really deport people who don’t mesh well with the rest of us; I’m suggesting that if doing so is ridiculous, so, too, must it be to deny an immigrant entry under the same rationale. That, too, leaving aside the even more practical considerations of how “we” might go about determining what “our” culture is, and who gets to decide which of “our” attributes are worthy of inclusion. In terms of actual policy, outside the ambiguity of social contract theory, designing policy guidelines that result in a cultural homogeneity that even the locals would prefer over the status quo seems impractical to the point of the absurd. As Paul Crider writes:

Who decides which aspects of “traditional” society are worth preserving (at the cost of more focused and observable individual freedoms, let’s not forget) and which aspects are merely parts of inevitable cultural evolution? …Should a committee of bureaucrats be set up to decide which foreign influences are acceptable cultural adaptations, the way the French have circled their wagons around the integrity of their language? Even if such a committee were popularly elected, it’s difficult to see how that democratic mechanism would achieve any greater legitimacy than uncoordinated individual actions…. There are other influences that will impact culture, influences that cultural preservationists are less willing to stifle by coercion…. Culture, including language, social values, artistic (literary, musical, etc) expression, and political values can and do all change as a result of younger generations challenging the ideas and practices of their forebears. This process of change over generations may be exacerbated by outside influences, but it would be hard to deny that at its core it is a natural phenomenon at work even in closed societies.

Many critics of immigration base their case against open borders on the differences between groups of human beings. I have attempted to show why this problem is not unique to immigrants, that we are in fact different from other natives, too. Eliminating differences in a community of peaceful people presents prejudicial, empirical, and practical problems that most would find unsettling. Those critics who point to “differences” as a justification for restricting immigration thus have a steep burden of proof assigned to them. Until they meet it, I remain unconvinced.