IN A world where ancient certain­ties are undermined daily, I thought that one clear line remained whose crossing we could all recognise: whether someone is alive or dead. But Horizon: Back from the dead (BBC2, Monday of last week) sug­gests that I have to abandon the comfort of that conviction.

Eleven years ago, a Norwegian skier fell beneath the ice, and froze. For more than two hours, her heart stopped, and an ECG detected no brain activity. But determined re­suscitation eventually encouraged her heart to beat again, and, after many years, she has fully recovered. It appears that if the brain is frozen to a particular degree before the heartbeat stops, it is protected, and can return to life; hypothermia shuts down, but also protects, the brain.

It seems that we must stop think­ing about death as a moment, but rather as a process — one that surgeons are learning to induce artificially by freezing a patient to create a window of suspended animation in which to conduct extreme medical procedures.

We saw marvellous recoveries from deep surgery that was possible only because the patient had been, as it were, briefly frozen to death on the operating table. We are getting closer to understanding how living cells determine whether to switch off, and, when we understand how this happens, then we will surely be able to manipulate the process.

Deep hypothermic arrest under­cuts our sense of the absolute separation between life and death. Precisely what happens to the soul in such situations was not explored — a pregnant area, surely, for theological speculation.

Turning from death back to life is probably how many of the subjects of The Secrets of Scientology (BBC1, Tuesday of last week) would de­scribe their journey. This was a follow-up by John Sweeney of an exposé he conducted in 2007, in which the constant surveillance and aggression that had sought to prevent his attempts to confront the organisation with its critics had finally driven him to a screaming fit.

This time round, however, he has surprising allies: two of the top people who had orchestrated the previous spoiling exercise have now left what I refuse to call a church, and were willing to confirm that every dirty trick used against his investigation had, in fact, occurred.

Scientology continues to deny it and, on the evidence of this film, routinely brands all defectors with stigma based on the recordings it makes of their “audits” (what most religions would term a confession), and subjects them to what amounts to intimidation. Students of belief systems will be intrigued by the fact that those now assisting Sweeney have not given up on Scientology itself: they are part of a movement that seeks to cleanse the faith and return it to its original purity.

In the main, this was a deeply up­setting programme, which showed how the most reprehensible human activities — especially amassing money and power — can mas­querade as religion. The re­deem­ing aspect was the courage of those who have got out, in many cases leaving behind everyone they love and the only life they have ever known.

Scientology is the classic vindi­cation of Craig’s First Law of Faith: never trust any religion whose founder died rich.