This question is more than a mind-bender. For thousands of years, certain people have claimed to have actually visited the place that no eye has seen, and no human mind has conceived, and their stories very often follow the same narrative arc. A lot of people talk about encountering a being of light. Tales like these are thrilling in part because their tellers hold the passionate conviction of religious converts: I saw it, so it must be true. According to a Gallup poll, about 8 million people claim to have had a near-death experience (NDE), and many of them regard this experience as proof of an afterlife—a parallel, spiritual realm, more real, many say, than this one. It’s an inversion, almost, of the old philosophical puzzle: If a tree falls in the forest and there’s no one there to hear it, does it make a sound? If you are certain that you saw something (or felt something or heard something), does it mean that it’s empirically proven? And if you are predisposed to want to see something, are you likelier to see it, the way Harry Potter saw his dear departed mother in Hogwarts’s magic mirror? And finally, if you see something while you are stressed or unconscious or traumatized in some way, does that circumstance delegitimize the veracity of your vision? This is the trouble with NDEs as a field of scientific study: you can’t have a control group. Most people on the brink of dying do die (and so cannot describe what that process is like), and those who survive approach the brink in such different ways—car accident, stroke, heart attack—that it’s impossible to compare their experiences empirically. But over the years, science has posited a number of theories about the connection between visions of heaven and the chemical and physical processes that occur at death. Since at least the 1980s, scientists have theorized that NDEs occur as a kind of physiological defence mechanism. In order to guard against damage during trauma, the brain releases protective chemicals that also happen to trigger intense hallucinations. This theory gained traction after scientists realized that virtually all of the features of an NDE—a sense of moving through a tunnel, an out-of-body feeling, spiritual awe, visual hallucinations, intense memories—can be reproduced with a stiff dose of ketamine, a horse tranquiliser frequently used as a party drug. If our conscious experience totally depends on the brain, then there can’t be an afterlife—when the brain is gone, the mind is gone. But it’s not that simple. Even when the brain seems to be virtually disabled, people are still having these experiences. there may be a great deal more to mind and consciousness. If we could prove there is life after death, you might view yourself and your life with a renewed sense of wonder and appreciation for what you have now.