Most of us opponents of a wall have focused on the idea that the wall is meant to "wall out" immigrants. But we just observed the 50th anniversary of the Berlin Wall, a wall that was meant to, and did, "wall in" residents. I think I remember co-blogger Bryan worrying that a wall on the border with Mexico might wall us in. I think this is a serious worry. If, 20 years ago, you had asked me if a U.S. president would try to persuade the head of a totalitarian country to reinstitute restrictions on residents leaving that country, I would have said "No way." Yet three years later that's exactly what President Clinton persuaded Fidel Castro to do.