America is not the only great power struggling with how to handle the future of foreigners in its midst. As the Supreme Court indicated in its mixed decision Monday on Arizona’s immigration-enforcement law, the question of how we regard those who arrive on our shores has both philosophical and practical components. The philosophical argument in favor of immigration is, of course, what my colleague Steve Coll describes in Comment this week, as “America’s foundational narrative”—the notion that the unique American advantage is our commitment to absorb the best brains and ideas from abroad. But, these days, that conviction runs into versions of a less soaring, if ostensibly practical, assertion, along the lines that “we already have a domestic work force that has the same skills,” as one advocate for reduced immigration put it in the Times yesterday. (That argument, incidentally, is not well-served by a new study that confirms what every globally minded executive will tell you: the future of American innovation depends substantially on our openness to foreigners because immigrants play a role in more than three out of four patents at the nation’s top research universities.