For most of its history, Christianity had a powerful representation in Europe, Africa, and Asia, and much of what is now referred to as "the Islamic world" was once Christian, according to the latest book by Penn State history and religious studies professor Philip Jenkins.

Read an excerpt from Anglican Communion in Crisis: How Episcopal Dissidents and Their African Allies Are Reshaping Anglicanism, by Miranda K. Hassett.

The Holy See has played an active global role for centuries. It has permanent observer status at the United Nations and has all the rights of full UN membership except voting.

Read more of Kim Lawton's interview about the Vatican and foreign policy with J. Peter Pham, director of the Nelson Institute for International and Public Affairs at James Madison University.