The Missing Political Ideology of Open Borders
I fully agree with Bryan Caplan in favor of Open Borders as an economic, moral or legal issue. But there remains the political issue.
The real problem with mass immigration is that of birth citizenship. Immigrants don't just partake in the economy, they change the polity. And not only will the current prevailing ideology not allow a permanent second class of hereditary metics—such a situation isn't stable, and leads to revolutions.
The descendants of immigrants organized as the Roman Plebs, whose activity made descendants of the original settlers rich Patricians. But eventually they demanded more political rights, which led to repression, civil wars, and the eventual fall of the Republic.
A world where citizenship is decoupled from either heredity or geography would be very different from what we have today. The prevailing ideologies would have to be very different—and probably the military technologies, too. Military technology has so far always favored large territories with relatively thin borders, though not so large that political coordination becomes harder than political enforcement. How do you deal with mass conflicts in a world of Open Borders?
Think of it: there will always be people with mortally incompatible values. Muslims and Jews. Collectivists and Individualists. etc. Integration requires a strong authority above—or else you soon enough have a civil war between neighbors. Segregation soon leads to territorial polities again, the rivalry between which will soon enough lead to warring countries settling borders based on the outcome of military engagements.
Also, if you want a world where people can freely cross borders—remember that it goes both ways. It should allow not just barbarians flocking to seek a better life among more civilized people, but also more civilized people crossing into territories currently dominated by barbarian thugs, topple the thugs in power, and settle peacefully, which entails imposing their civilized order over the barbarians who would disturb it.
In any case, the first and most difficult step to achieve Open Borders is ideological—finding and spreading an ideology that enables peaceful coexistence, including the identification and repression of those who would destroy the peace. An ideology strong enough to replace the Westphalian Nation States. Strong with deadly weapons. And ideology that can acknowledge differences between peoples without explaining any and all differences as oppression and turning them into conflicts. An ideology where accepting new neighbors, or your neighbors having more children, does not grant them increased political power over you and your children. The ideology of Property Rights.
I have argued before that in a world where Naturally and Artificially Intelligent agents with wildly and widely different capabilities exist, a winner-takes-all political ideology, whether "democratic" or not, will necessarily lead to an all-out-war with much discrimination, repression, revolution, and even genocide, every time new peoples or new kinds of AIs come into contact. But the root problem is not the new peoples (via immigration) or new kinds of AIs (via innovation). It is the political ideology. "Democracy" will lead you to genocide, again. Only Property Rights can save you.
“All honest people are welcome to live here, or anywhere. All dishonest people are welcome to die here, or anywhere.” — Libertarian Open-Borders, Open-Hunt Policy