Gustave Dore via Art Passions

In this illustration for Dante's "Paradiso," the poet beholds heaven's highest realm.

What if God is a microbe, and we're just the hosts for the creatures made in Its image? A neuroscientist and self-described "possibilian" offers 40 thought-provoking possibilities for the afterlife in a slim book called "Sum."

The questions that David Eagleman deals with at his day job at the Baylor College of Medicine in Houston are already pretty far-out: How do our brains construct reality? Why does our perception of time's flow change? Why do some people "see" music or associate numbers with colors?

But even at work, some of Eagleman's ideas are so far-out they have to be put aside ... until he goes home and writes about them.

"In some sense, I use my literary fiction as a channel to explore ideas that I come up with during the day," he told me.

For example, consider how the data in your brain determines your identity. "For a long time, there's been this open question of what it would be like to be someone else - or to be something else," he said. "Once you're John Malkovich, you wouldn't remember what it's like not to be John Malkovich."

That spawned Eagleman's little story about cross-species reincarnation, titled "Descent of Species": Suppose you admired the strength and beauty of horses, and you got the chance to become a horse in your next life. Once you become a horse, would you have enough wits to appreciate that life, or even enough wits to choose the life after that? And if that's the case, what unwitting demigods might we humans have been in our past lives?

Other stories play off the fact that existential meaning doesn't scale well. "What would happen if we showed Shakespeare to a dog or a bacterium?" Eagleman asked. "It's pointless, because what's meaningful to you changes by spatial scale."

For example, a microbial God might reserve the afterlife strictly for microbes, with humans merely serving as part of the scenery. Or the universe might be ruled by a cosmic Giantess who is as indifferent to our fate as we are to the fate of an amoeba.

None of Eagleman's 40 tales is longer than five pages, and they all have a clever twist of karmic justice (or injustice) worthy of "The Twilight Zone."

Eagleman also notes that each story contradicts all the others - which he says is "the metamessage of the book." It's not a strictly scientific point of view, but it's a point of view that allows for multiple possibilities when it comes to life's deepest question.

"The idea that people will tell their stories with certainty, and fight and die over those stories, is just so ludicrous - because it's so much bigger than that," Eagleman said.

When it comes to his personal views on the afterlife, Eagleman shies away from calling himself an atheist, or a deist or theist. Instead, he prefers the term "possibilian." So do a lot of other people, it turns out. Eagleman's reference to "possibilianism" in an NPR interview spawned Facebook groups and a Web site for like-minded fans, and now he's planning to write a book titled "Why I Am a Possibilian."

But first, he's planning to finish a book on "the secret life of the unconscious brain," titled "Dethronement." In a sense, it's a book about your inner zombie - that is, all the processes that go on behind the scenes beneath your consciousness. He's also co-written a book about synesthesia, delving into the ways that your different senses cross wires with each other. (For instance, why do some people associate the number 4 with orange? Personally, I think 4 is blue.)

"What I'm hoping to do is write fiction and nonfiction alternately so that they synergize," Eagleman said.

Neuroscience certainly provides enough factual fodder for fiction. At his day job, Eagleman studies vision perception and time perception.

"In both those issues, reality ain't what you think it is," he said. "We can make you think something lasted longer or shorter than it really does, something happened before when it really happened afterward. The brain is not just passively recording some river flowing past. Our brains are constructing time."

With all that material to work with, Eagleman isn't likely to run out of stories anytime soon.

"All it takes to grow a neat scientific idea into fiction," he observed, "is to extrapolate it to where it matters in everyday life."

Now it's your turn. Do you have stories to share, either about the possibilities for the afterlife or about the weird workings of the brain? Feel free to share them as comments below.

More encounters with the afterlife:

• Near-death experiences: What really happens?
• Discuss near-death experiences on Newsvine
• Your views on out-of-body experiences
• Your views on the meaning of heaven