Heaven has an edge over every other construct of the human imagination because, built into the design, alongside the fabulous promise that we can, after all, live forever, is a catch. We can never try it out and report back. There are no return tickets. And, before Richard Dawkins points it out, yes, of course, that means that even if every single one of us is ultimately disappointed when we catapult into oblivion, we have no way of warning those who come after us.
That, at least, is the theory. But when we are told that sneak previews are impossible, we instinctively try to find a way round the restriction. So on the cover of this week's Newsweek, neurosurgeon Dr Eben Alexander, who has taught at Harvard Medical School, boldly announces to the world that he has cheated death, visited Shakespeare's "undiscovered country from whose bourn no traveller returns", and come back to tell us all in his imaginatively titled book, Proof of Heaven.
In 2008, Alexander was struck down by meningitis and spent seven days in a coma. Science says that, during this ordeal, everything should have gone blank since his neocortex wasn't functioning. But this celestial Columbus claims that, while apparently flat out, he was actually on "a hyper-vivid and completely coherent odyssey" to the final frontier. He floated over fluffy clouds, met "transparent … shimmering beings" and was guided through this timeless world by a beguiling female. It was all, he writes reassuringly, "an immense void, completely dark, infinite in size, yet also infinitely comforting".
At least he didn't mention a bright white light, but in every other way his account contains just about heavenly cliche known to humankind. Proof of Heaven may have a certain cachet because its author is, by profession, "a man of science", and therefore, by the crude logic of our secular, sceptical 21st-century society, better placed than most to see through the ultimate claim of religion, but this book sounds like pretty run-of-the-mill near-death experience literature.And there's plenty of it around. The International Association for Near-Death Studies, founded in 1981, claims to speak for a constituency of 15 million in the US alone. In hugely popular books such as psychologist Raymond Moody's Life After Life, thousands of travellers report back on an extra-terrestrial world of painlessness, mysticism, peculiar light and beautiful but intangible guides to a divine pleasure dome.
What is most remarkable about these accounts is how similar they are to each other and to a whole literature that stretches back through the centuries. Once, the very same topography was part of the beatific vision, fashioned by Christian theologians such as Saint Augustine as a heavenly landscape to frame the face of God.
The similarities prompt one of two responses. Either it must be true because so many people say it is. Or they are borrowing from each other one of the biggest collective delusions we have ever known. Or, perhaps, there is a third, more plausible explanation.
At its most simple, all of these pictures of after-life touch on the most basic of human needs, something that predates written language, philosophy and even religion itself. From the time the first Neanderthal sat next to the lump of dead protein that had been his or her mate and realised that something had to be done about the smell of rotting flesh, we have wanted there to be something more, something beyond death. When that body was put into a ditch, or pushed over a ledge into a ravine, the one left behind looked into the void and ached.
The myths, traditions and literature, the shamans and soothsayers, the priests and popes, the poets, writers and dramatists, have subsequently all tried to picture an after-life to take the sting out of that yearning. And, lest I be accused of having a closed mind (which I don't), of the uncertainty. Alexander, then, is just the latest in a long line.
There has, though, always been a tension in such fevered – or coma-induced – imaginings. For what most religions have taught is that heaven, paradise, nirvana, jannah, or whatever they have called it, is ineffable, beyond words, beyond imagination.
Photograph: Ron Edmonds/AP