Is nothing. Ultimately, we're all just molecules. You, me, Hitler, MLK, Kennedy, John Lennon, religious conservatives, everyone. Molecules. All notions of morality and emotion are just illusions and nervous impulses designed to help create more molecular combinations until eventually the earth is destroyed and the entire history of humanity becomes no more relevant to the universe than the history of garden slugs. Not much to rejoice over. Which is why when you say it that way, atheists get pissed. I know this for a fact by the way.
So it shouldn't be surprising that atheism usually - usually, not always - appeals to the liberal promise of base appetites and animal pleasures, since there's not much else it can provide. And that goes with imagination. Has anyone come away from The Golden Compass saying, "Ah, there was a deep and profound imaginative world"? Perhaps atheists. Most believers I know who read the work had trouble keeping awake.
Maybe that explains, or is explained by, Richard Dawkins' recent statement that it's high time we stop exposing our kids to fairy tales and myths and fantasy stories and anything to do with the supernatural. Say goodbye to the Tolkien, trolls, unicorns, dragons - you name it. I mean, reading fairy stories his harmful? What's that even mean? And post-Christian, post-religious thought was suppose to free us! This in a growing line of things that are harmful. Of course that's the way secularists try to impose values, declaring something harmful. When you don't have objective morality, you go for practically.
It makes me think of growing up. I remember there was this radically fundamentalist family with a preacher kid. He went about telling kids there was no Santa. Satan Clause he called him. A big lie. It was quite a news story for a while. It was framed in the liberalism of the day as that which liberalism was promising to release us from. That close minded and intolerant view of the world that would run about telling other kids what they should and shouldn't believe. Funny how things have come around. But then, given what atheism ultimately promises, should we have expected anything different?