Most religious traditions embrace elements of monasticism, the practice of renouncing worldly pursuits to devote one's life to spiritual concerns. In a modern spin on that concept, a growing number of progressive Christians are leaving behind the materialism of Western culture to live communally and serve the poor in some of the nation's most blighted areas. Jonathan Wilson-Hartgrove, a 25-year-old divinity student at Duke University, is one of the leaders of this movement, dubbed "new monasticism." The name comes from a book titled "Living Faithfully in a Fragmented World," written by Wilson-Hartgrove's father-in-law, Jonathan Wilson, a professor of theology and...