Moller’s response on immigration also leaves me unmoved.  Point-by-point reply, with Moller in blockquotes.

I agree with Caplan that we should have high levels of immigration for both moral and self-interested reasons, and that a great deal of resistance to this traces back to confused zero-sum thinking about trade and jobs, or to xenophobia.

So far, so good.

The point where we may disagree is this: I don’t think libertarianism (or its core ideas and values) entails open borders.

Without what you call “emergent moral powers,” how is that possible that libertarians doesn’t entail open borders?  In the absence of an explicit contract (such as a home owner’s association), I have no right to control who lives in my neighborhood.  So how can citizens of a country possible have a right to control who lives in their country?  Treating mere residence in my vicinity as aggression really is on par with blaming others for “breathing my air.”

Reasonable people who take seriously individual rights, limited government, and the rest, can favor borders and some restrictions on immigration, depending on the particulars.

“Depending on the particulars,” sure.  I’m not an absolutist either.  But how can your book fail to imply (a) a strong moral presumption in favor of open borders, and (b) strong residual obligations toward anyone whose mobility the government restricts?  Imagine writing one of your imaginary speeches to the community, and you’ll see what I mean.

Consider Island, a small country off the US coast. Over the years, American tourists enjoy visiting Island. Gradually, their influence becomes more and more pronounced, to the point that Island starts to lose its language (French, perhaps), American missionaries introduce what Islanders view as false gods, etc. I disagree that the people of Island have no recourse for meeting what they will see as an unwelcome threat. I don’t think it’s true that Island must accept a kind of hostile takeover by Americans.

There’s a bizarre equivocation here.  Sure, the natives have “a recourse.”  They have a right to complain about this “hostile takeover by Americans.”  They have a right to argue in favor of their way of life.  They have a right not to trade with Americans.  Unless you believe that government has emergent moral powers, though, natives who like these cultural changes and want to trade with Americans also have every right to embrace these new cultural and economic opportunities.  If the net effect – resistance by some, acceptance by others – is dramatic cultural change, the losers must accept it.  They have no right to use the government to ensure that their recourse is actually effective.  Because if they did, they’d be trampling on the rights of all the dissenters.

I think this is true even intranationally–if the Amish want to stay Amish, they don’t have to accept a mass influx of Brooklyn hipsters, supposing they have legal means of preventing this, and that their reasons are good ones. It would be hard to believe in freedom of association and think they did.

Another bizarre equivocation.  When you say “supposing they have the legal means of preventing this,” are you referring to standard contractual methods?  Or government regulation?

If you mean the former, then sure.  In the real world, however, this is utterly impractical: Unless all the Amish have signed a massive contract, individual Amish property owners retain the right to sell real estate to Brooklyn hipsters – and some are almost sure to sell.  If you mean government regulation, then you have to invoke emergent moral powers, which you explicitly reject.

Of course, none of this is to speak to the present-day US, and I agree with a great deal of what Caplan says about the moral imperatives of benefiting and being benefited by immigration. Obviously the US and Island are quite different. But the Island case suggests to me, again, that libertarian values don’t entail open borders.

“Entails” is a strong word, and “libertarian values” is a vague phrase.  But libertarianism definitely implies a strong moral presumption in favor of open borders.  Indeed, libertarianism aside, any view that rejects the emergent moral powers of the state creates a strong moral presumption in favor of open borders.  After all, almost every moral view denies that mere existence in my vicinity is blameworthy.  So unless the government has the emergent moral power of defining mere existence in my vicinity as blameworthy, how can immigration restrictions be justified?