And not many megachurches would extend the invitation — especially if the atheist wrote a book called “I Sold My Soul on eBay.”

But at Oak Hills Church in San Antonio, senior minister Randy Frazee saw an opportunity to challenge his congregation by inviting Hemant Mehta, a self-described “friendly atheist” from Chicago, to speak with Frazee in front of thousands of Christians.

At four church services over the weekend that attracted about 8,000 people, the preacher and the atheist casually talked and laughed on the brightly lit stage at Oak Hills. Online videos of their talks were posted on the church's website, which crashed Sunday morning from the demand of so many people trying to watch.

Clean-cut and courteous, Mehta could easily be mistaken for a church youth-group leader.

“Is there anything — anything — that might change your mind?” Frazee asked Mehta at one point.