DJ: How do you respond to that, Peter?

PS: That's an interesting position and there is certainly a consequentialist element to it, and obviously people who are not consequentialists very often do make consequentialist arguments — we couldn't live without doing so. I accept that. I suppose that I'm not as confident as Nigel seems to be that the best way to reduce child abuse and elder abuse is to prohibit euthanasia at the end of life. If you have a situation in which somebody doesn't actually want to go on living, but they don't have any means of ending their own life, and at the same time they are a burden to their family, leaving the carer to become desperate, one could imagine that abuse could occur. That would be a kind of a double tragedy — both for the person who was not able to choose to end his life and he was then a further burden on the family, which then had led to abuse. So, I think yes, that can be a problem. When women have children that they don't want to have, that can also be a source of child abuse.  That's a reason for respecting women's autonomy over whether they are going to give birth to a child or not.

I was also interested in where you think that we should draw the line, conservatively, as you said, around 18 weeks. I also think that somewhere around that point — and I wouldn't commit to exactly 18 weeks — but somewhere around that point, where you do have the beginnings of the development of brain activity and perhaps conscious awareness, I agree that there is something else there to worry about — a sentient being. We should be very concerned about that, at the very least not to inflict unnecessary pain on that being if an abortion is going to occur. I would agree that at that 18-week stage it should only occur for important reasons. You would hope that very few abortions are carried out at that stage.

I do think that these considerations are relevant, but I'm not so convinced that prohibitions on other forms of killing, or killing at other stages of life is the best way to achieve the goals that you and I both share about reducing the abuse of both children and old people.

DJ: Peter, in some of your writing you are very clear, and you even talk about a new commandment, that the worth of human life varies. This flies in the face of the whole Judaeo-Christian tradition, which relies on the idea of the "sanctity of life". How do you answer the charge that once you open the door to subjective judgments about the values of different lives, there is no stopping place? Above all, you are not taking proper account of what Immanuel Kant called the "radical evil" that exists in the world, that human beings are capable of doing terrible things. Is your calculus really a strong enough safeguard against man's inhumanity to man?

PS: First, you said the words "once I have opened that door" — that is the door when one says that some human lives are not to be valued the same as others, or not equal to others. My response to that would be that the door is already open and it's not possible to close that door in any society that has  modern methods of healthcare, because they are going to have to make decisions about whether to prolong some lives or not. There really is no debate in any developed society that we do that — we turn off life support on some patients whose lives we could prolong.