From Hobbes and Hegel to John Stuart Mill and John Rawls, the seminal figures of Western political theory are united in their almost complete neglect of the topic of immigration. No doubt they have their reasons. Who among them witnessed anything like the global refugee crisis of 2015? Or the anxieties about national identity that it inflamed? Be that as it may, with hostility toward immigrants and refugees fueling the “Brexit” movement and the presidential campaign of Donald J. Trump, we could use some deep thinking right now about the relationship between the state and its citizens. This deep thinking would no longer start with the assumption that we already know who is included in that relationship (thanks for nothing, John Locke!), but rather would inquire how, in light of often conflicting values like local democracy and global justice, we should go about figuring that out.

On the case is the political philosopher David Miller. His timely book STRANGERS IN OUR MIDST: The Political Philosophy of Immigration (Harvard University, $35) may not be the first treatise of its kind, but it aims to be the first to combine such an abstract approach to the topic with such a strong dose of realism. Make no mistake: Miller is a humane, social democratic Oxford University professor — a softy. But he does not wish away such stubborn, unfortunate facts as social prejudice and failed states, and he wrestles with the issue of immigration from that hard-­bitten perspective. He comes down in favor of a state’s right — except when human rights are threatened — to close its borders to outsiders, and proposes four principles that should govern states’ selection policies when they do choose to admit immigrants.

Miller’s first principle is what he calls “weak cosmopolitanism.” A weak cosmopolitan believes in the equal worth of all human beings but sees this as morally compatible with giving special consideration to our compatriots. The argument is simple: The radical changes to our behavior required by a strong cosmopolitanism — which holds that we have an obligation to treat all people the same — would entail abandoning too much of what gives shape and meaning to our lives in the first place (our families, communities and so on).

In the context of immigration, strong cosmopolitanism mandates an international “open borders” policy, whereas weak cosmopolitanism dictates only that a country’s policy cannot violate anyone’s human rights and sometimes must actively protect them, as with people fleeing genocide. Apart from that, a weakly cosmopolitan state does not have an obligation to accept any would-be immigrants. What it does have to do, out of respect for them as human beings, is provide defensible reasons for declining them. As an extreme example, Miller cites the European Union’s controversial decision in 2014 to direct fewer resources to rescue missions for migrants on rickety boats in the Mediterranean. Even if you disagreed with the policy, its rationale — that the rescue missions were creating a perverse incentive for these dangerous journeys and thus ultimately imperiling more lives — was both reasoned and consistent with a belief in the value of all human life.