Present-day relevance of 20th century theologian Reinhold Niebuhr, an influential, boundary-crossing voice in American public life. Niebuhr created the term "Christian realism:" a middle path between religious idealism and arrogance. Exploring his wide appeal, host Krista Tippett and three guests describe Niebuhr's legacy and ask what insights he brings to the political and religious dynamics of the early 21st century.