GLOOMY mid-autumn, when the natural world dies back for winter, is traditionally the time of year when people recall the dead. The church calendar marks the season with All Saints' Day and All Souls' Day, and the secular world has Hallowe'en.

The idea that human life con­tinues in some form after physical death is common to many faiths. Although there is nothing tangible that scientists can test, there is mounting anecdotal evidence of life after death taken from the witness statements of the many people who have been brought back from the brink by medical science.

Hundreds of patients who have died, in the sense that spontaneous breathing and heartbeat have stopped and measurable brain activity has ceased, have been resuscitated. Many come back to consciousness with vivid recollections of having been somewhere else, to a "spiritual" realm often equated with heaven.

The contemporary systematic study of this phenomenon can be dated to the work of the American philosopher and medic Dr Raymond Moody, who has, over 50 years, collected more than 1000 accounts of individual experiences. He helped found the International Association for Near-Death Studies, which has a continuing programme collecting cases. There is also the Near Death Experience Research Founda­tion (NDERF), which, too, collects and publishes cases.

Often, the tourists to heaven come back with remarkably similar descriptions. They talk of entering through a tunnel, at the end of which is a bright light. They discover a land of heightened colour and beautiful gardens. They see dead relatives, heavenly gates, angels, and even Jesus. Reports of visits to hell are rare.

Yet, say the sceptics, such experi­ences are no more than delusions. The images described are drawn from art, religion, and culture. The in­fluence of culture is not discounted by researchers, but it is not seen as the whole explanation. Jody Long from the NDERF accepts that each person integrates his or her near-death experience into a pre-existing belief system. "This important truth must be kept in the back of one's mind when reading these different reports."

AN INTRIGUING case has been reported recently of a Harvard neurosurgeon, Dr Eben Alex­ander, whose 15-year study of brain function had led him to side with the sceptics. He was, however, forced to re-examine his conclusions when, in 2008, he had his own hallucination (or vision), after contracting a rare form of meningitis. "If you wanted to come up with an experimental model that would best approach human death, meningitis is perfect," he says.

When he woke, he had "very powerful memories". He recalled a journey from darkness to a place of beautiful meadows. "I was a speck on the wing of a butterfly." He felt him­self leaving the universe and of "being aware of the Divine", in a place of love.

Now fully recovered from his illness and feeling able to write it up, Dr Alexander admits that it is im­pos­sible to explain his experience satis­factorily in scientific terms. "There is no good neuro-physiological explana­tion for what happened to me."

His account is entirely consistent with the thousands of reports that have been accumulated over the years. The common features noted from his research by a psychiatrist, Dr Bruce Greyson, of the University of Virginia, are: leaving the body; sensing a light; feeling a warmth; and having contact with a Christlike divine being.

One scientific explanation suggests that these memories are created when the brain comes under such stress that it is deprived of oxygen. It is a theory that was inadvertently tested when, in the 1970s, as part of their training, US Air Force pilots had their brains deprived of oxygen when subjected to the G-forces of a centrifuge. They invariably lost consciousness, and afterwards recalled seeing lights and having out-of-body sensations. None of them, however, described meeting with deceased relatives or sensing a divine presence.

THE argument that images reported from "heaven" are products of the visitor's cultural background is chal­lenged by accounts from children. They have provided information of which they could have had no prior knowledge.

Colton Burpo, from Nebraska, astonished his parents, one of whom was a Christian pastor, with his account of heaven. He was almost four years old, and seriously ill with a ruptured appendix when, in 2003, he described meeting John the Baptist, seeing angels, and sitting on Jesus's lap. That the son of a minister could come up with such obviously Christian-based stories did not surprise his parents. They were, though, taken aback by their son's accurate descriptions of them at the time he was ill. But the bombshell revelation came in a conversation between Colton and his mother. "I have two sisters," he announced. While Colton's older sister had been told of the baby her parents had lost, Colton was considered too young to know. He described how in heaven his other sister had run up to him.

IN MANY academic disciplines, such as history and law, witness evidence is the stuff of study. The physical sciences require evidence of a differ­ent kind, drawn from careful ob­servation, the collection of data, and, ideally, experiments that can be reliably repeated and controlled.

In the Bible, there are stories of the privileged few who have been granted glimpses of heaven, although, inter­estingly, in the several instances of the raising of the dead, nothing is said of what they experienced between death and being restored to life.

There is thus no consistent Chris­tian way of explaining near-death experiences. A further stumbling- block for many Christian traditions is that, sometimes, accounts from adherents of other religions in­corporate elements of their own faith tradition. "Yamraj was there sitting on a high chair with a white beard and wearing yellow clothes," one Hindu recounted. Yamraj is a Hindu god of death.

Science, too, cannot get to grips with the thousands of stories col­lected, and the remarkable consis­tencies running through them. The problem that scientists find is that the numerous personal accounts defy methodology. They are difficult to analyse in any way that enables data to be extracted or trends meaning­fully correlated.

Dr Moody has said that the most fascinating aspect of his work is the "potential bearing on the biggest question of human existence: Is there an afterlife?" He emphasises, however, that the numerous accounts do not amount to scientific evidence. "It is not yet a scientific question. It is still a conceptual question. That is, it requires logical reasoning about concepts, not scientific methods."

Those who return from death with vivid recollections find their fear of death removed. Sometimes they have a sense of being sent back for a reason. The rich man in Luke 19 was forbidden to warn his brothers of hell, but perhaps God wants us all to hear reports of heaven.

Ted Harrison is a former BBC religious affairs corres­pond­ent.