It's not easy watching a man commit suicide on camera. The public uproar over the BBC documentary Choosing To Die, in which the author and Alzheimer's sufferer Sir Terry Pratchett visits the Dignitas euthanasia clinic in Switzerland, has reopened the debate over whether or not sufferers from terminal and chronic illness should be allowed to end their own lives. In the film, we watch Peter Smedley, a British sufferer from motor neurone disease, as he swallows the killing draught; he coughs as he begins to fall asleep, and asks for water. The prim Dignitas "escort" refuses. His wife, the picture of pseudo-aristocratic dignity, holds his hand as his head begins to drop to his chest. Sir Terry sits opposite the Smedleys as they say goodbye, swallowing obvious tears. It is terribly hard to watch.

It is no harder, however, than it would be to watch a man die slowly and in pain, longing for release. Sir Terry, whose own encroaching mortality is a constant, ominous presence in the programme, concludes with wobbling lip that this was a good death -- "When we think of all the ways people can die, that would count as a result" -- and that the creepy little blue house on the Swiss industrial estate where so many come to die exists for a good reason. It is difficult not to take his point, especially when one sees how rigorous and exhausting are the checks for fitness of mind and non-coercion run by the clinic. With an ageing population suffering increasingly from protracted, agonising end-of-life conditions, now would seem precisely the time for an adult debate about assisted dying. It seems likely, however, that the debate will be messy, drawn-out and painful.

Talking about suicide has always been taboo, even in journalism, a profession not generally known for tact and discretion. It is only 50 years since the practice was decriminalised in this country, and parts of the 1961 suicide act provide that, while you can no longer be sent to jail for surviving a suicide attempt, your friends and family can be imprisoned for up to 14 years if they are suspected of assisting a suicide -- even just for offering, like brave Mrs Smedley, a loving hand to hold at the end. There is something about this subject that repels rational debate. It sticks in the craw, disgorging reason. You can't help but feel that the reason nobody wants to ask the important questions about chosen death is that nobody really wants to hear the answers.

There is a very real fear that if we talk about this properly, we might reach a conclusion that we might not want to face: that, in some cases, taking one's own life is a sane and sensible thing to do. The term that commenters keep returning to is "slippery slope": if we acknowledge that self-murder might be acceptable for the terminally ill, what about the chronically ill? What about the mentally ill? What about those who are in perfect physical health but, like a small minority of Dignitas clients, are simply "weary of life"? If everyone could die in a time and place of their choosing, might we not see the numbers of suicides rise from current averages of just over 5,000 a year to tens or hundreds of thousands, many of them young people with everything to live for?

This is a legitimate fear. At 24, I have lost several friends to suicide. I have seen many more young people with big lives ahead of them attempt to end those lives. I have intervened personally in three suicide attempts, all of them involving young adults under 22. Those incidents were frightening, painful and heartbreaking for everyone involved. Hundreds of children and young people commit suicide every year in Britain and, according to the Samaritans and Barnados, that number is rising. I believe, like the Dignitas director, Ludwig Minelli, that the "right to self-determination" includes the right to control the manner of your death as far as possible, but the thought that it might somehow become acceptable for anyone simply to give up on life genuinely chills me.

That is not, however, what a service like Dignitas is offering. Dignitas, in fact, appears to offer a civilised solution to a problem which has dogged society, not to mention the medical profession, for centuries -- injecting a merciful dose of procedural oversight into a shadowy world of unspoken pain and moral dilemma, providing one has the £10,000 to cover the clinic's costs.

The key statistic is that 70 per cent of those who make enquiries with Dignitas never call back. The knowledge that the option of a quick and painless end is there seems, in fact, to give many people the strength to carry on. There is cause to believe that oversight and legitimacy in the field of euthanasia might, in fact, reduce the number of tragic suicides, by giving desperate people back a sense of control over the end of their lives. As Nietzsche observed, the thought of suicide, considered rationally, may well be "a powerful solace: by means of it one gets through many a bad night."

We live, for now, in a society where theological dogma does not dictate policy, but the notion of suicide as a "sin" persists. The reasons behind religious proselytising against suicide -- which comes with the not insignificant metaphysical threat of hell -- are benign enough for anyone who believes that God and law can and should dictate the lives of human beings. There is, however, also a powerful argument that the "sanctity" of life is worth less if the individual living that life cannot determine its boundaries. There is an argument that a measure of formality, choice and control in death is no bad thing for a person living out their last days in pain and terror. These are arguments that, if we wish to live in a truly civilised society, we will soon collectively be obliged to consider.

Rather than consider them, however, much of the response to this documentary and the difficult issues it raises, particularly on the Christian right, has focused on the possibility of a second "slippery slope". The fear seems to be that if euthanasia were not taboo, the elderly and infirm might be encouraged to end their lives against their will, to spare their families and the state the burden of caring for them, despite the enormous bureaucracy already in place to prevent this from happening. The hypocrisy of this moral panic is unbelievable, when hospices and end-of-life care centres are facing funding cuts of 30 per cent, according to a report released in January.

The brutal truth is that we do not need to fear a world where the sick, disabled and terminally ill are denied support and treated as disposable. We are living in that world, right now.

On 10 June last year, Paul Reekie, a 48-year-old poet from Edinburgh, took his own life. Spread out on the table beside him, in place of a suicide note, were two letters: one informing him that his Incapacity Benefit had been stopped, and another informing him that his Housing Benefit had also been stopped. This government, expanding on the policies of the last, is currently forcing over a million sick and disabled people to undergo a work capability assessment performed by a private company, Atos Origin, with a £300m mandate to deny benefits to hundreds of thousands of claimants. As a result of these tests, patients in the final stages of cancer have been refused the pittance of state support that was supposed to make the end of their lives bearable.

This month, top mental health charities warned the government that the tests were already causing desperate claimants to take their own lives, and that more suicides can be expected if the scheme continues. Someone in government appears already to have accepted and made provisions for this eventuality, distributing handy suicide guidelines to staff at call-centres dealing with benefit claims. The callousness with which this is being done should shock us; it should shock us far more than as-yet-abstract idea of state-sanctioned euthanasia. Instead, we nod along as ministers and tabloid headlines inform us that these people are not worth the good money we could be pumping into tax relief for the banking system.

We need no longer fear a world where society and the state cannot be bothered to expend time and money looking after the sick, the dying and the unprofitable. We are already living in that world. We are halfway down the slippery slope, clutching for handholds of humanity. If we truly believe that all human life is precious, if we truly believe in dignity in life and in death, we should start by taking an honest look at the slow, unmerciful slaughter of a welfare state which, while ailing, has so much more to give - and considering what that says about all of us.