Fourteen years ago, a woman named Arline asked me on a date. She took me to lunch in downtown Seattle, where we ate oysters and watched ferries glide away from the dock. I couldn't have imagined then what it would mean to share my life with an immigrant. It turns out that it means many things, but perhaps of most consequence is that I am constantly learning about life through the eyes of someone whose first twenty-five years were radically different from mine. Arline left Panama with her husband and three young children in 1979. Her half-sister was a U.S. citizen because she was born in...