There are several possible explanations for the widespread belief in an afterlife (the simplest being that people are taught this and believe it), but one that has gained considerable traction is the “near death experience” or NDE. Though I have never researched the issue, I know that NDEs have certain commonalities such as seeing bright lights, the sensation of moving through a tunnel towards a door or gate, out of body experiences, intense recollections of certain persons or events, and a pervasive sense of calm or peace.
The fact that people would have similar experiences during NDEs makes complete sense, given that all humans have brains and nervous systems that are similarly constructed. As the brain and nervous system shut down, it stands to reason that the manner of shutting down would induce similar types of sensations and experiences. The analogy here would be drug induced trance or fantasy states — there is a commonality to such states which arises from the fact that drugs impact each person’s brain in roughly similar ways. To the extent that such experiences are personalized, this would be due to the fact that varying degrees of conscious inputs idiosyncratically pattern the particular sensations.
This was simply a hypothesis of mine, but a recent article by Lisa Miller in Newsweek addresses these issues more comprehensively:
According to a 2000 article in The Lancet, between 9 and 18 percent of people who have been demonstrably near death report having had such an experience. And surveys of NDE accounts show great similarities in the details. People who have had NDEs describe—like some religious visionaries—a tunnel, a light, a gate, or a door, a sense of being out of the body, meeting people they know or have heard about, finding themselves in the presence of God, and then returning, changed.
Andrew Newberg is an associate professor in the radiology department at the University of Pennsylvania who has made his reputation studying the brain scans of religious people (nuns and monks) who have ecstatic experiences as they meditate. He believes the “tunnel” and “light” phenomena can be explained easily. As your eyesight fades, you lose the peripheral areas first, he hypothesizes. “That’s why you’d have a tunnel sensation.” If you see a bright light, that could be the central part of the visual system shutting down last.
Newberg puts forward the following scenario, which, he emphasizes, is guesswork. When people die, two parts of the brain, which usually work in opposition to each other, act cooperatively. The sympathetic nervous system—a web of nerves and neurons running through the spinal cord and spread to virtually every organ in the body—is responsible for arousal and excitement. It gets you ready for action. The parasympathetic system—with which the sympathetic system is entwined—calms you down and rejuvenates you. In life, the turning on of one system prompts the shutting down of the other. The sympathetic nervous system kicks in when a car cuts you off on the highway; the parasympathetic system is in charge as you’re falling asleep. But in the brains of people reporting mystical experiences—and, perhaps, in death—both systems are fully “on,” giving a person the sensation both of slowing down, being “out of body,” and of seeing things vividly, including memories of important people and past events.
Although Professor Newberg concedes this is merely a hypothesis, it has the considerable virtue of being grounded in known physiology. Whenever we are confronted with something that is hard to explain or unknown, the best practice is to begin with the simplest hypothesis that requires the fewest number of assumptions. This practice is widely known from philosophy and is essential to science — it is known as “Ockham’s Razor.”
Ironically, this principle was given to us by a 14th century theologian and Franciscan friar, William of Ockham.