In the debate on assisted suicide, we are all ultimately on the same side: we all want to limit suffering.

Compassion motivates all those who are genuinely interested in the debate. There is all the difference, however, between limiting suffering and ending life.

Committed supporters of assisted suicide have to as ask themselves two fundamental questions. First, how much risk to the vulnerable are they prepared to accept in order to facilitate suicide by the invulnerable? Secondly, where to draw the line in determining what suffering "qualifies" for assisted suicide?

No safeguard can ever be 100 per cent effective. As well as the clear abuses, there would also be the inevitable subtle pressures on those whose illness or condition met the criteria. On a recent BBC Radio 5 Live phone-in, Michael, who has motor neurone disease, explained how he is asked several times a week whether he would consider assisted suicide.

He said: "It makes one feel like I should be contemplating it for sake of the health service or my family watching what I'm going through. And I'm afraid that it will extend into the social conscience that people almost expect assisted dying."

There is a real danger of this societal pressure subtly eroding free choice from within. And this is something that no safeguard could ever protect against. Legalising an action normalises it so that it often becomes expected.

A journalist with spinal muscular atrophy wrote something similar in the New York Times: "I've lived so close to death for so long that I know how thin and porous the border between coercion and free choice is, how easy it is for someone to inadvertently influence you to feel devalued and hopeless, to pressure you ever so slightly but decidedly into being 'reasonable,' to unburdening others, to 'letting go.'"

Palliative care is undergoing constant improvements: pain is increasingly well managed and a more holistic approach to end-of-life care is being taken. But there is still suffering and death is being put forward as the answer. But if death is a proportional response to suffering, where does it stop? Why should some types of suffering make someone eligible for assisted suicide but not other types of suffering? We see this in Belgium with an ever increasingly broad definition of suffering. Recently, twins who were losing their sight, a patient who suffered a botched sex-change operation and a young woman suffering from anorexia: all were subject to euthanasia.

An even more scary case is that of Eva. Talking about her request for euthanasia, she said, "The fact that I don't function very well in our society, that's my fault only. It's my thoughts, it's my feelings, it's how I experience life. That is no one else's responsibility but mine. I blame no one. The battle is done. I admit it for myself. It ends here." Her request was granted, and she was given a lethal injection, aged 34. She didn't fit in, and so she asked to die.

In Belgium and the Netherlands, there has been an incremental extension of euthanasia legislation. Proponents of assisted suicide will point to Oregon and say there has been no extension of the legislation there yet but, in Europe, we are in a very different culture. Oregon is surrounded by states that do not permit assisted suicide and so it is already sticking its neck out. But here in Scotland, we have Belgium and the Netherlands just across the North Sea with such extreme practices that anything we introduce would almost pale into insignificance and there would be nothing really holding us back.

The push for assisted suicide comes from a genuine concern for suffering that we all share but at the cost of unjust risk to the vulnerable and with no clear boundaries. Here in Scotland, we like to think of ourselves as guardians of justice and compassion; this is our chance to show that we mean it. This is our chance to show that every life matters, that everyone is valuable.