Tim Lott: The top of a slippery moral slope

Anyone coming from a position of neutrality who watched Terry Pratchett's documentary on Monday, charting the assisted suicide of the motor neurone disease victim Peter Smedley would probably end up more in favour of assisted suicide than not.

It was not, to Pratchett's credit, a polemic. The writer, who suffers from Alzheimer's himself and wishes legally to be able to end his life in due course, examined very fairly some of the countervailing arguments. But there was no doubt about the purpose to the programme: to promote the cause of assisted suicide.

The arguments made in favour were clear. At its most simple, assisted suicide is about individual self-determination, and the relief of suffering in the face of outdated religious credos which insist that only God has the right to decide who lives and who dies.

Pratchett, trying for even-handedness, interviewed a taxi driver who preferred to await his death in a hospice, cared for by his family. And Pratchett's own grief at the two suicides featured – Smedley himself and the outrageously healthy-looking 42-year-old Andrew Colgan, who suffered from MS – made it clear that he took no pleasure whatsoever in seeing these untimely deaths unfold (even if he did describe Smedley's death as "a happy event").

I am instinctually in favour of assisted suicide. But the programme left me feeling uncomfortable. I have no time for the religious argument. And yet, I hesitate to fully sign up for the cause – simply because I wanted to die once, and have been enormously relieved that I never did anything about it.

Admittedly I was suffering mental rather than physical illness – in my case acute depression. I had been suffering agony for four years and saw no end in sight. But with hindsight it is plain to me that you can be very serious about your wanting to die, having taken all matters into account – and most of those around me thought I was absolutely in my right mind – then later discover that you very nearly made a literally fatal mistake.

There is a consensus that no one who is mentally ill should be allowed to be helped to kill themselves. But what about people who are in deep despair? And how close is despair to depression? Ludwig Minelli, secretary general of the suicide charity Dignitas, did not demur when it was suggested that people might want to end their lives simply out of "general weariness".

The "thin edge of the wedge" argument is somewhat convincing. Once assisted suicide is established in law, how long before the patient and their relatives decide how serious the illness has to be before the decision is taken, rather than doctors? What about in the case of a painful cancer that is perhaps not necessarily fatal, and even capable of remission, but which the sufferer no longer wishes to endure through to the possibility of a cure? Or perhaps choosing to die because an affliction is simply very painful and chronic but not fatal at all, and for which there is a hope for a cure? In other words, choosing to die out of "general weariness".

Can these decisions be left in the hands of those who may not have all the information at their fingertips – simply because they cannot see into the future? And this again is where the slippery moral slide begins. What if a patient wants to live, but feels they can't be a burden on their family? They might decide to die simply through guilt. And what if there is an inheritance involved and a ruthless family who are a bit too happy to enable the suffering one's wishes? It would be easily enough to put pressure on someone near to death.

"I would not like to live in a world where you can die more or less at any time more or less on a whim," says Pratchett. But the thick end of the wedge may be exactly that. I remain on Pratchett's "side", and I wish him well. But let no one imagine that there are any easy moral answers. Matters of life and death are never black and white.

Tim Lott's books include 'The Scent of Dried Roses'