An atheist and a little girl.

*The folks at /r/atheism won't like this joke.*

An atheist was seated next to a little girl on an airplane and he turned
to her and said, "Do you want to talk? Flights go quicker if you strike
up a conversation with your fellow passenger."

The little girl, who had just started to read her book, replied to the total
stranger, "What would you want to talk about?"

"Oh, I don't know," said the atheist. "How about why there is no God,
or no Heaven or Hell, or no life after death?" as he smiled smugly.

"Okay," she said. "Those could be interesting topics but let me ask
you a question first. A horse, a cow, and a deer all eat the same
stuff - grass. Yet a deer excretes little pellets, while a cow turns
out a flat patty, but a horse produces clumps. Why do you suppose that is?"

The atheist, visibly surprised by the little girl's intelligence,
thinks about it and says, "Hmmm, I have no idea." To which
the little girl replies, "Do you really feel qualified to discuss
God, Heaven and Hell, or life after death, when you don't know shit?"

and then she went back to reading her book.