For over two decades John Green's vocation has been ministering to inner-city men on the margins of society. Green didn't set out to be another Dorothy Day or Mother Teresa, and would be quick to tell you he hasn't become one. Struck by the words of Micah 6:8 and the act of a homeless man who gruesomely ended his life in Green's presence, Green vowed to constantly ask himself: How can I live justly? To whom do I show mercy? How may I walk humbly with...