As Mideast turmoil spreads, a professor of international affairs says we are witnessing changing interpretations of religion and "a struggle over which interpretations have authority over whom."

The conflict between Sunnis and Shiites. It goes back nearly 1,400 years. Today it is tearing Iraq apart. But the two branches of Islam have not always been openly hostile, and in many parts of the world they live together peacefully. Lucky Severson talked with a prominent Middle East scholar about the rivalry's history, and why it has exploded recently, and what the prospects are for the future.

Read correspondent Lucky Severson's August 7, 2006 interview in Washington, D.C. with Vali Nasr, a professor in the Department of National Security Affairs at the Naval Postgraduate School in Monterey, California.