Noted scientist and best-selling novelist Alan Lightman, a Memphis native, asks what are the boundaries between science and religion, the two greatest forces that have shaped human civilization. What are the different kinds of knowledge in science and in religion? And how do we come by those different kinds of knowledge? Members of the Faith in Memphis panel respond.

On the way to appreciating the kind of knowledge that religion produces, we might consider, briefly, the kind of knowledge that math produces. Math, we presume, produces an empirical kind of knowledge, a kind of knowledge that is rooted in a shared reality, since math is merely the symbolic description of what really happens in the real world. “2 + 2 = 4″, then, is a mathematical kind of knowledge, because the logical premises of the mathematical expression correspond with arrangements of quantities that we can all reproduce readily with bananas, automobiles, and one-legged dogs.

But math is not so straightforward. What is the square root of negative one? The math we learn in elementary school says there is no such thing. It’s like Santa Claus. You can say there’s a square root of negative one, but you’d just be saying.

On the other hand, saying that there is a square root of negative one makes possible all sorts of things we call “knowledge”. The electrical wiring in our houses and the computer hardware that we use to write interrogations of epistemology depend on saying that there is a square root of negative one. “Imaginary numbers” — that’s what mathematicians really call things like √-1 — lie at the root of a kind of knowledge on which we all, collectively, depend.

Marcus du Sautoy, a real-life, Oxford University mathematician, says this about √-1: “We could have said, ‘this number doesn’t exist’. But we say, ‘no, come on, let’s imagine something that would work.’” Imaginary numbers exist not to express what we have to think, but to express what we can think.

Imaginary numbers aren’t simply practical. Some mathematicians say that Euler’s Identity, which uses an imaginary number, is math’s most beautiful equation. They use that word, mathematicians do: beautiful.

And no wonder. There’s something about math — especially the math of imaginary numbers — that’s like art.

Religion, too, is like art. Religion, like poetry, like painting, like music, does not affirm what we have to think, but appeals to us through the ways it expresses what we can think.

Perhaps there’s a distinct difference between the knowledge that “2 + 2 = 4″ represents and the knowledge that “god exists” represents. If so, we might very well speak of different kinds of knowledge. But the concept of “knowledge” may be useless if it is infinitely divided into categories and subcategories that are distinctly different from each other.

Perhaps “knowledge” is one, and it arises from the uniquely human creativity of thought that we find in math and biology and epics and physics and sonatas and scriptures. When science, art, and religion really work, they don’t settle for what is, but similarly see what can be.