He has been denounced as a heretic for saying the human consciousness survives when the heart and brain cease to function.
Dr Peter Fenwick is no crank - he's an eminent neuro-psychiatrist, academic and expert on epilepsy and brain disorders. But to a number of his peers in the medical community, he is a man with outlandish ideas.
The 71-year-old remains unruffled by the furore. When asked why his peers in the science community are so vituperative, he replies simply: "Fear that magic will come back into science, and an inability to tolerate ambiguity."
Critics object that research into deathbed phenomena is qualitative - drawn from reports of patients and carers - rather than evidence-based. And Fenwick himself was a sceptic once, a highly respected academic and clinician. In 1985 a patient was referred to Fenwick following an operation that had gone wrong. The patient had found himself leaving his body and hovering over his hospital bed.
He told Fenwick he had journeyed down a long tunnel towards a bright light before being pulled back "into my body again".
"I didn't really believe in near-death experience," says Fenwick. "But after seeing this patient I thought, we'd better have a look."
He began collecting stories and in 1987 presented the results on television. Within days he had 2,000 letters, each telling a personal story of near-death experience.
Since then he has written a book, The Truth in the Light, with wife Elizabeth, interviewed countless patients who have 'come back', and continued to collect reports.
They tell of dying patients being greeted by dead relatives. A girl reported "knowing" the moment her brother had died. There were many reports of a bright light floating above dying patients, or tunnels leading toward it.
Scientists have rational explanations for these phenomena, which include neurotransmitter changes in the body as it is closing down, and the suggestibility of patients and relatives.
Fenwick acknowledges these, and the physical explanation of light phenomena, "but that doesn't explain why the light is repeatedly and consistently associated with love, peace and compassion."
A relatively few people - about 10% is the generally agreed figure - have some sort of near-death experience. The ingredients don't seem to change, nor the numbers; so why does someone of Fenwick's intellect persevere?
Doesn't he lose heart with the unproveability of it?
"No," he smiles. "I felt a little while ago that perhaps we know all there is to know. But not any more. If, when all brain functions are down, the patient is able to receive information, then it follows that the mind can act independently of the brain.
"We must be able to demonstrate this objectively if we are to move forward; it's vital for neurological science and our understanding of human consciousness."
Fenwick says there is interesting work looking at what happens to relationships, sense of self and so on in people who have had a near-death experience. "People report being more spiritually aware, more concerned with family, happier."
He adds, "The area of spiritual care needs much more education. We recognise childbirth as a transcendent event - a baby becoming itself, changing the lives of those around it. Death, surely, is similarly significant and yet we are reluctant to look at it." How does he anticipate his own death? His face lights up. "Oh, I'm enormously interested. I'd love all the grandchildren gathered around the bed."
And all the phenomena you can muster? "Oh yes, that would be perfect."