One such is Nicholas Winton, a 29-year-old British banker who, in December 1938, canceled a holiday vacation to volunteer to help trapped refugee children escape the Nazis in Czechoslovakia. He is believed to have personally saved the lives of more than 600 children, demonstrating that even in the worst of times, any one of us can make a profound and positive difference. We are living through the worst refugee crisis since the Second World War, with millions displaced from conflict zones in Ukraine , Afghanistan, Syria, and beyond. Many of these are children, and it is easy to despair when...