He has been Professor of Sociology and of Comparative Religion at the University of Washington and, since 2004, Distinguished Professor of Social Sciences at Baylor University and co-director of the Institute of Religious Studies at the university. He is founding editor of the Interdisciplinary Journal of Research on Religion. Author of numerous works, including his most recent books include: God'sBattalions. The Case for the Crusades (2009), Discovering God. The Origins of the Great Religions and the Evolution of Belief (2007) and Cities of God. The Real Story of How Christianity Became an Urban Movementand Conquered Rome (2006).