Ronald H. Stone taught the social ethics of Paul Tillich as the John Witherspoon Professor of Christian Ethics at Pittsburgh Theological Seminary. Hearing Tillich preach and teach at Union Theological Seminary and Columbia University inspired walks and talks with his mentor, Reinhold Niebuhr about Tillich. Stone is a past president of the North American Paul Tillich Society. During his career, he has written or edited two dozen books on religion and society.