Is Metaphysical Naturalism Viable?

On February 1st, 2013 at Purdue University, Dr William Lane Craig participated in a debate with Dr Alex Rosenberg on the topic, "Is Faith In God Reasonable?" Over 5,000 people watched the event on the Purdue University campus along with tens of thousands streaming it live online from around the world. In this clip, Dr Craig responds to metaphysical naturalism which asserts that only physical things exist.