One of the most popular books of the 12th century — what might be called medieval infotainment — was “The Vision of Tundale.” Written by a man who claimed to have had a stroke and then, unconscious, to have been taken on a tour of heaven and hell, it was widely read not just for Christian edification but for pleasure. It described an ascension through layer upon layer of hell and then heaven, and thus through ever-increasing miraculous pleasures. Tundale sees orbs and goblets strung from gold chains in the sky, and when the angels fly through them, they make a sound like heavenly wind chimes.

Tundale yearns to stay, but his angelic guide leads him back to his body. When he wakes up from his coma, he is changed forever. He gives all his money and possessions to the poor and becomes a monk.

Sound familiar? This, in its broadest outlines, is the “plot” of “Proof of Heaven,” the runaway bestseller by Eben Alexander III, a Duke- and Harvard-educated neurosurgeon who claims to have seen heaven in 2008 during a coma induced by bacterial meningitis. (The excerpt in Newsweek last month presaged the book’s sensationalist debut.) Alexander’s experience convinced him beyond doubt of the existence not just of heaven, but of a loving God. He now hopes, as he says in his book, to “serve the greater good by helping to create the best possible future for earth and its inhabitants.”

Such visionaries have been visiting heaven for thousands of years, as I learned in the research for my book on the subject, and the outlines of their travels are remarkably similar. After a prelude in which the heavenly tourist endeavors to convince his listeners of his credibility as a narrator, he describes wonders — all the while claiming that the wonders pass description. “Words cannot express” and “language fails” are common refrains in such accounts, as they are in Alexander’s. Uniting these accounts is a sense of a conviction that the reality of the next world supersedes this one. When in heaven, Alexander receives a message from God: “I instantly understood that it was true. I knew so in the same way that I knew the world around us was real — was not some fantasy, passing and insubstantial.”

An insistence on the realness of heaven underlies all the recent bestsellers on the topic, including “90 Minutes in Heaven,” the 2004 account by an evangelical pastor of his trip to the next life after a serious car accident, and “Heaven Is for Real,” about a 4-year-old boy who travels to heaven and sees Jesus during a surgical procedure.

The disingenuous thing about Alexander’s claims is not, as neuroscientist and rationalist Sam Harris argued in a hilarious and vitriolic critique on his blog, that the doctor’s upbringing in watered-down, mainline Christianity led him inevitably to proclaim, like Tundale, the “good news” (Alexander uses the phrase) of Jesus Christ. It’s that Alexander — or his editors at Simon & Schuster — cravenly believes that his fancy degrees, his bow tie and the numerals after his name somehow lend his account more authority. The subtext of his story is something like, “Because I’m a Harvard-educated doctor, you can believe me more than those Bible Belt Christians who’ve told this story before.” As if going to Harvard inoculated a person against believing fantastical things. As if medical doctors never found their way, except through near-death experiences, to deep religious faith.

Let me be clear. I believe that Alexander “saw” what he says he saw and felt what he says he felt, and that, further, his experience was profound and life-changing for him. But no matter how many times he says the word “neurosurgeon” — 16 times in my Kindle edition — his authority on the afterlife is exactly the same as Tundale’s and every other visionary’s. To have experienced something and to have believed it to be true doesn’t make it true for Alexander or any of us. You don’t have to be a brain surgeon to know that.

But it doesn’t make it untrue, either. Even Harris, the rationalist, agrees that there are things about the universe and consciousness that are mysterious.

“I remain agnostic on the question of how consciousness is related to the physical world,” Harris wrote. “So although I am an atheist who can be expected to be unforgiving of religious dogma, I am not reflexively hostile to claims of the sort Alexander has made. In principle, my mind is open. (It really is.)”

The way I see it, heaven claims crumble when you subject them to empirical tests, which is all right, because heaven, for me, is not a matter of proof. It’s exactly the opposite: a matter of faith. For me, belief in heaven (or an afterlife, or however you want to put it) is an embrace of the mysterious, unknown nature of things; a reverence for transcendent experience; and a radical hope in eternity as well as in the possibility of ultimate justice, love and truth. That heaven is possible but not provable is sufficient.

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