Science and religion have never gotten along very well. But both strive to answer one fundamental question: What does it mean to be human? Are we here thanks to a random sequence of events—just an organized blob of mud—or destined to follow a path laid down for us by a higher power? There is a middle path, though, that borrows elements from both systems of thought—a way of understanding the world that gives our inner lives and the universe meaning without a theistic belief system.

Standing firmly behind this "poetic naturalism" is Sean Carroll, the theoretical physicist who's taken readers on a journey through time in From Eternity to Here and the hunt for the Higgs-Boson in The Particle At the End of the Universe. Now he’s put together a big sprawling work of philosophy to examine that one big question. Also: whether God exists, and what happens after you die.

In his new book out tomorrow, The Big Picture: On the Origins of Life, Meaning and the Universe Itself, the 49 year-old Caltech professor assembles a framework to help him find answers to these questions. He borrows freely from great thinkers of the past and his current research in cosmology, all the while dropping in anecdotes about his own mortality on an LA Freeway near-miss, or contemplating the meaning of the transport malfunction in Star Trek’s “The Enemy Within.” WIRED talked with Carroll about what these ideas mean to him as a scientist, a self-described naturalist, and a human.

In The Big Picture, you talk a lot about poetic naturalism. What is that and how is it different than plain old atheism?

Atheism is a reaction against theism. It is purely a rejection of an idea. It's not a positive substantive idea about how the world is. Naturalism is a counterpart to theism. Theism says there’s the physical world and god. Naturalism says there’s only the natural world. There are no spirits, no deities, or anything else. Poetic naturalism emphasizes that there are many ways of talking about the natural world. The fact that the underlying laws of physics are deterministic and impersonal does not mean that at the human level we can’t talk about ideas about reasons and goals and purposes and free will. So poetic naturalism is one way of reconciling what we are sure about the world at an intuitive level. A world that has children. Reconciling that with all the wonderful counterintuitive things about modern science.

The book draws upon elements of your own life, of popular culture, particle physics, history, philosophy and cosmology. What’s the thread that binds all these themes?

It is a long book [Ed. note: 464 pages]. I cut some of it. There are two threads. One is an apologia for naturalism. I’m saying that despite appearances to the contrary in our everyday life, this world we live in is governed by laws that don’t have goals or purpose that are not sustained by anything outside the world. It is just stuff obeying the laws of physics over and over again. The other thread is that that is OK. The fact that you were not put here for any purpose, that we are collections of atoms that always obey the laws of physics is not reason to despair that life is meaningless.

Naturalism says that we were not put here for any purpose. But that doesn’t mean there isn’t such thing as purpose. It just means that purpose isn’t imposed from outside. We human beings have the creative ability to give our lives purposes and meanings. Just as we have the ability to determine what is right or wrong, beautiful or ugly. That point of view is not only allowed, it is challenging and breathtaking in its scope.

Did you change your mind about anything after writing The Big Picture?

Not very much. I think what I believe now is what I’ve always believed. I think the closest I came to changing my mind is I got a renewed appreciation for the subtlety and persuasiveness of the anti-naturalism argument. It’s always easy to hold in your mind a straw man, a vision of people that disagree with you. These are smart people who disagree with you. I tried my best to give them the benefit of the doubt and put forward the best version. I understand more why people would disagree with me.

Do you think there’s anything in your life experience; a tragedy, a near-miss on the highway, the death of someone close, that could make your views shift over time?

If evidence comes in that makes me think the world is different, I will try my best to be open to changing. There’s nothing that I wouldn't change my mind about if the evidence is really good. It’s important to note that in examples where something terrible has happened, in my experience, naturalists handle this much better than theists do. Understanding that life is finite, that it will end, that not everything happens for a reason, that there is randomness and unpredictability. It doesn’t make tragedy go away. It’s just that you are not waiting for a miracle anymore.

With your books, online videos, blogs and TV appearances, you’ve become an eminent popularizer of science. Do you take any heat from your scientist colleagues about this?

Yes. Though it’s rarely explicit. Everyone agrees that spreading science more widely is a good idea in the abstract. However there is a strong feeling that if any one person is spending time doing this they are not spending time doing serious research that they should be doing. I ignore them. Doing well is the best revenge. I just try to do good research.

Americans aren’t very science-literate. What do you think we should know about science?

The fact that science is not a list of particular facts or theories. Science is a way of getting knowledge. It’s a method. It’s a method that really relies on making mistakes. We propose ideas, they are usually wrong, and we test them against the data. Scientists do this in a formal way. It’s a way that everyone can go through life, that’s how we should be teaching science from a very young age.

__Would it help our science literacy or science itself if people could get free access to scientific papers, such as arXiv or other open-source publishing sites? __

I don’t think it makes a big difference for science literacy. They are meant for other scientists. But we have intermediaries, we have translators and communicators and writers who do look at these papers and can share them. They are always there. In biology, there’s a fiscal move toward doing something like what physicists are doing [with arXiv]. There are worries that they will misuse the system. But the system works great.

What do you hope that readers take away from The Big Picture?

I talk about the difference between awe and wonder. We often group them together. Awe makes you think about being so impressed with the world, that you don’t know what to do. You let it wash over you. Wonder is connotation, a feeling that this is amazing and I want to understand it better. I want readers to know that the world is understandable. We are not there yet, but it’s not a fundamental mystery.