John C. Purdy, a staff member of the Presbyterian Church U.S.A., has written a challenging book entitled Returning God's Call: The Challenge of Christian Living. In it, Purdy suggests that we need a new metaphor for the Christian life. He points out the inadequacy of the old metaphors such as "a soldier in God's army," "a scholar in the school of Christ," "a traveler a long the Christian way," "a citizen of the commonwealth; "and a member of Ch…