DURHAM, N.C.—Eben Alexander was your typical neurosurgeon. A firm believer of scientific reductionism, he thought that all thoughts originate from the brain. But this changed in 2008 when he encountered a case of near-death experience (NDE). As much as it was the complete opposite of his previous views, he couldn’t dismiss or avoid the case—it was none other than his own experience, and he had to face it and search for an explanation. Having contracted acute bacterial meningitis, which damages the neocortex—the part of the brain that is thought to involve complex cognitive functions like conscious thought—Alexander went into a...