Typically, the question “Is there a God?” does not come up on late-night TV. But Wednesday night was different.

Stephen Colbert is one of comedy’s most devout Catholics—he even teaches Sunday school. Ricky Gervais is one of its most outspoken atheists, happily getting into a philosophical debate with anyone on Twitter who disagrees with him.

On Wednesday, they met on the Late Show couch, and Colbert presented Gervais with what he thought was a simple question: “Why is there something instead of nothing?”

“That makes no sense at all,” Gervais replied, denying the premise of Colbert’s inquiry right off the bat. “Surely, the bigger question is not why but how,” he said. “Why is irrelevant, isn’t it?”

Asked by Colbert if there is a “demiurge” that started everything, Gervais said, “Outside of science and nature, I don’t believe so.” He described himself as an “agnostic atheist,” meaning “no one knows if there’s a God.”

“So technically, everyone’s agnostic. We don’t know,” Gervais continued. Colbert couldn’t help but agree on that point. “An agnostic atheist is someone who doesn’t know if there’s a God or not, as no one does,” he said, adding, “Atheism is only rejecting the claim that there is a God. Atheism isn’t a belief system.”

Gervais summed up atheism this way: “You say there’s a God. I say, can you prove that? You say no. I say I don’t believe you, then.”

If Colbert believes in one God, then “there are about 3,000 to choose from” if you go back through history, Gervais said. “Basically, you deny one less God than I do,” he told Colbert. “You don’t believe in 2,999 Gods. And I don’t believe in just one more.”

“I know that I can’t convince you that there is a God, nor do I really want to convince you that there is a god,” Colbert said, explaining that he personally has a “strong desire” to direct his “gratitude” for life “towards something or someone.”

When Gervais brought up how difficult it is for some people to believe the Big Bang Theory, Colbert tried to describe that belief as similar to faith. Instead of having faith in God, he suggested, Gervais has faith in Stephen Hawking.

But that’s when Gervais went in for the kill. “Science is constantly proved all the time,” he said. “If we take something like any fiction, any holy book, and destroyed it, in a thousand years’ time that wouldn’t come back just as it was. Whereas if we took every science book and every fact and destroyed them all, in a thousand years they’d all be back, because all the same tests would be the same result.”

“That’s good,” Colbert had to admit. “That’s really good.”

He may not have convinced Gervais that God exists, but Gervais may have done just a little bit to make Colbert question his faith.