By AL WEBB

c. 2012 Religion News Service

LONDON (RNS) A controversial Oxford University professor billed by many as the world's "most famous atheist" now says he is not 100 percent sure that God doesn't exist -- but just barely.

In a 100-minute debate with Archbishop of Canterbury Rowan Williams, Richard Dawkins surprised his online and theater audiences by conceding a personal chink of doubt about his conviction that there is no such thing as a creator.

But, to the amusement of the archbishop and others, the evolutionary biologist swiftly added that he was "6.9 out of seven" certain of his long-standing atheist beliefs.

Replying to moderator Anthony Kenny, a noted English philosopher, Dawkins said, "I think the probability of a supernatural creator existing (is) very, very low."

Dawkins, author of "The God Delusion" and other best-sellers, is a leader of the "New Atheist" movement that aggressively challenges belief in God and criticizes harm done in the name of religion.

"What I can't understand is why you can't see (that life started from nothing and) is such a staggering, elegant, beautiful thing, why would you want to clutter it up with something so messy as a God," Dawkins told Williams, according to The Daily Telegraph account.

The archbishop, who heads both the Church of England and the worldwide Anglican Communion, replied that he "entirely agreed" with the "beauty" part of Dawkins' statement -- but said "I'm not talking about God as an extra who you can shoehorn onto that."

Richard Dawkins & Rowan Williams The Archbishop of Canterbury discuss Human Beings & Ultimate Origin, 23rd February, Oxford, moderated by Anthony Kenny.