For liberals, immigration is a reality teeming with potential

When it comes to whether and how to regulate the economy, Western societies have a history of liberal theory upon which to rely. But when it comes to immigration, there is not much in the liberal tradition to which they can turn. As a result, in both Europe and the United States, much of the debate over immigration is dominated by illiberal voices, the most insistent belonging to politicians who promise to protect the cultural integrity of the homeland against the presumed degeneracy of the alien.

Xenophobia is an illiberal response to immigration from the right, but multiculturalism represents much the same thing from the left. Many multicultural theorists, although committed to openness toward immigrants, are not committed to the openness of immigrants to their new home. For them, newcomers, living in an environment hostile to their way of life, need to preserve the cultural practices they bring with them, even if some of those practices - for example, arranged marriages, gender segregation, religious indoctrination - conflict with liberal principles. Group survival counts more than individual rights in the moral accounting of many multiculturalists.

One way to maintain a commitment to openness when addressing the vexing question of national borders is to recognize that cosmopolitanism is a two-way street. Immanuel Kant teaches us that the circumstances in which we find ourselves must always be judged against the circumstances in which, but for chance, we might have found ourselves.