In Eben Alexander's best-selling book Proof of Heaven: A Neurosurgeon's Journey into the Afterlife (Simon & Schuster), he recounts his near-death experience (NDE) during a meningitis-induced coma. When I first read that Alexander's heaven includes “a beautiful girl with high cheekbones and deep blue eyes” who offered him unconditional love, I thought, “Yeah, sure, dude. I've had that fantasy, too.” Yet when I met him on the set of Larry King's new streaming-live talk show on Hulu, I realized that he genuinely believes he went to heaven. Did he?

Not likely. First, Alexander claims that his “cortex was completely shut down” and that his “near-death experience ... took place not while [his] cortex was malfunctioning, but while it was simply off.” In King's green room, I asked him how, if his brain was really nonfunctional, he could have any memory of these experiences, given that memories are a product of neural activity? He responded that he believes the mind can exist separately from the brain. How, where, I inquired? That we don't yet know, he rejoined. The fact that mind and consciousness are not fully explained by natural forces, however, is not proof of the supernatural. In any case, there is a reason they are called near-death experiences: the people who have them are not actually dead.

Second, we now know of a number of factors that produce such fantastical hallucinations, which are masterfully explained by the great neurologist Oliver Sacks in his 2012 book Hallucinations (Knopf). For example, Swiss neuroscientist Olaf Blanke and his colleagues produced a “shadow person” in a patient by electrically stimulating her left temporoparietal junction. “When the woman was lying down,” Sacks reports, “a mild stimulation of this area gave her the impression that someone was behind her; a stronger stimulation allowed her to define the ‘someone’ as young but of indeterminate sex.”

Sacks recalls his experience treating 80 deeply parkinsonian postencephalitic patients (as seen in the 1990 film Awakenings, which starred Robin Williams in a role based on Sacks), and notes, “I found that perhaps a third of them had experienced visual hallucinations for years before l-dopa was introduced—hallucinations of a predominantly benign and sociable sort.” He speculates that “it might be related to their isolation and social deprivation, their longing for the world—an attempt to provide a virtual reality, a hallucinatory substitute for the real world which had been taken from them.”

Migraine headaches also produce hallucinations, which Sacks himself has experienced as a longtime sufferer, including a “shimmering light” that was “dazzlingly bright”: “It expanded, becoming an enormous arc stretching from the ground to the sky, with sharp, glittering, zigazgging borders and brilliant blue and orange colors.” Compare Sacks's experience with that of Alexander's trip to heaven, where he was “in a place of clouds. Big, puffy, pink-white ones that showed up sharply against the deep blue-black sky. Higher than the clouds—immeasurably higher—flocks of transparent, shimmering beings arced across the sky, leaving long, streamerlike lines behind them.”

In an article in the Atlantic last December, Sacks explains that the reason hallucinations seem so real “is that they deploy the very same systems in the brain that actual perceptions do. When one hallucinates voices, the auditory pathways are activated; when one hallucinates a face, the fusiform face area, normally used to perceive and identify faces in the environment, is stimulated.” Sacks concludes that “the one most plausible hypothesis in Dr. Alexander's case, then, is that his NDE occurred not during his coma, but as he was surfacing from the coma and his cortex was returning to full function. It is curious that he does not allow this obvious and natural explanation, but instead insists on a supernatural one.”

The reason people turn to supernatural explanations is that the mind abhors a vacuum of explanation. Because we do not yet have a fully natural explanation for mind and consciousness, people turn to supernatural explanations to fill the void. But what is more likely: That Alexander's NDE was a real trip to heaven and all these other hallucinations are the product of neural activity only? Or that all such experiences are mediated by the brain but seem real to each experiencer? To me, this evidence is proof of hallucination, not heaven.

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