David M. O’Leary is a Jesuit priest and a senior lecturer in comparative religions and medical ethics at Tufts University in Medford, Mass. He contributed articles on heaven and hell to The Encyclopedia of Religious and Spiritual Development.

The Rev. Maria Erling is a Lutheran pastor and an associate professor of the history of Christianity and global missions at the Lutheran Theological Seminary at Gettysburg in Gettysburg, Pa. She contributed a chapter on mainline Protestants in New England to Religion and Public Life in New England: Steady Habits Changing Slowly.

David Hackett is an associate professor of religion at the University of Florida in Gainesville. He is an expert on American religious history and the sociology of religion.  

Walter Sundberg teaches church history at Luther Seminary in St. Paul, Minn., and has written about religion, politics and trends in American religion.

Dale Soden is a history professor at Whitworth University in Spokane, Wash. He contributed a chapter on mainline Protestants, Catholics and Jews in the Pacific Northwest to Religion and Public Life in the Pacific Northwest: The None Zone.

Mark Shibley is a sociologist at Southern Oregon University in Ashland, Ore. He has studied spirituality in the Pacific Northwest, historically the region with the greatest number of religiously unaffiliated people in the United States, and contributed a chapter on the subject to Religion and Public Life in the Pacific Northwest: The None Zone.

Patricia O’Connell Killen teaches American religious history at Pacific Lutheran University in Tacoma, Wash. She is the co-editor of Religion and Public Life in the Pacific Northwest: The None Zone. She is an expert on people in that region who claim no religious affiliation.

John L. Jackson Jr. is the Richard Perry University Professor of Communication, Africana Studies and Anthropology in the Standing Faculty of the Annenberg School for Communication and the Standing Faculty of the School of Arts and Sciences at the University of Pennsylvania. He has researched the beliefs and practices of Black Hebrews.

Ferenc Szasz is an associate professor of history at the University of New Mexico and author of Religion in the Modern American West.