Immigration is a challenge but also a measure of the confidence of a society, its preparedness for self-renewal. That confidence is low in America right now. “The dignity of a person is untouchable” — so begins Germany’s postwar Constitution, with words drawn from bitter experience. Merkel has shown the conviction that this idea can eventually be absorbed by everyone now in Germany. She will be vindicated.“The dignity of a person is untouchable” … unless she’s a German woman on New Year’s Eve in Cologne.