There are three circumstances in which hard-core anti-abortion activists will permit the termination of a pregnancy: when hell freezes over; when all the seas run dry; when the moon turns into a balloon. Or more succinctly, not now, not ever, never.
Whatever their failings, they are consistent. No human tragedy, no vile act of oppression, outweighs their sincere revulsion for the act of abortion. Their position is absolute. To them, there are no exceptions, only hard cases that make bad law.
This much is obvious. But its implications for the politics of abortion need to be spelled out. Before we get into another saga of all-party committees and Green Papers and widespread consultations, we should acknowledge that the deep conflict over abortion in Irish society is politically insoluble.
Between those who believe there can be no circumstances, however extreme, that justify abortion and those who believe there must be some circumstances, however limited, in which it is permissible, there is no middle ground. It follows, therefore, that a political process which aims to find a compromise acceptable to Youth Defence and SPUC is a sham. Either it is a mere delaying tactic or it is an insult to the sincerity of the anti-abortion activists, a refusal to take their repeated declarations of total opposition seriously. Unless we recognise that these people are motivated by religious faith rather than political conviction, we will get nowhere.
That doesn't mean, however, that we don't need a public debate about abortion legislation. It just means we have to start with a clear sense of who should be talking to whom. And I would suggest that the most important dialogue to be entered into is that between pro-choice liberals, on the one side, and the large middle ground of ordinary religious believers who, at the moment, distrust both the pro-choice and the pro-life lobbies.
If a workable compromise is to emerge, it can only be one acceptable to the mainstream of decent citizens who go to church and instinctively recoil from the idea of abortion in Ireland.
And that dialogue has to start with liberals asking ourselves a hard question: what is it about us that people fear? If the answer to that question is merely that we are right and they are wrong, then it will be a very short dialogue.
If, on the other hand, the movement for "reproductive rights" examines its own tangled history, then it will recognise that there are issues on which it has been profoundly wrong and religious people have been broadly right.
What has to be acknowledged is that the pro-choice movement does have some pretty revolting antecedents, and that abortion has, historically, been mixed up with some vile attempts at social engineering. Up to 20 years ago, the heroine of the movement was Margaret Sanger, the American activist who established many of the first family planning clinics.
Sanger's motives were a complex mixture of liberal humanitarianism and disgusting, demented proto-fascism. She generally embraced the pseudo-science of eugenics - the notion that traits like violence, fecklessness and dishonesty were inherited and could be eliminated by selective breeding. Sanger wanted white Anglo-Saxon women to be encouraged to breed while immigrants, the undeserving poor and people with disabilities were to be dissuaded from doing so.
This was more than a mad idea. It was a social programme. The Nazis, of course, implemented it thoroughly. But so did some liberal, democratic societies. In the US, by 1937, 28 states had adopted eugenics sterilisation laws aimed at women for whom "procreation was deemed inadvisable". Until these laws were rescinded in the 1970s, more than 200,000 women were sterilised. The same thing, as we have recently discovered, happened in Sweden, the very model of an enlightened society.
It would be absurd to blame today's feminists for the sins of their foremothers. But it would be equally stupid not to accept that the religious groups who stood out against such practices were on the side of the angels. Or to deny that there have been good reasons for suspicions about where this liberalism might be heading.
Eugenics may be discredited but it has, in some societies, been privatised. Reproduction, in America and elsewhere, has become a consumer service. If you pay for the "perfect baby", you have a right to get it. A combination of extensive pre-natal testing and selective abortion is being used to "breed out" disabilities like spina bifida, muscular dystrophy and Down's syndrome.
Indeed, the most challenging perspective on abortion is one that has been kept on the margins of debate - that of the disability rights movement. Disability activists point to a deep irony.
On the one hand, they have succeeded to a large extent in overturning the idea that people with disabilities are defined only by tragedy and suffering. It is now, in theory at least, widely accepted that someone with, say, spina bifida, can lead a full, human life.
On the other hand, the new genetic and reproductive technologies are resulting in the practice of selective abortion to ensure that fewer and fewer such people will be born.
What do those of us who are broadly pro-choice have to say to people with disabilities who define themselves as "the constituency of the potentially aborted"? How do we accept that, for instance, sign language is a rich cultural resource, and yet face the fact that if and when a pre-natal test for deafness becomes available, a "woman's right to choose" might lead to its elimination?
How do we answer the question posed by one disability activist: "Why shouldn't deaf people, proud of their own distinct sign-language culture, elect for a deaf child and abort a foetus that would become a hearing person?"
It may be objected that all of this is a bit too complex for a society that can't even deal with the rights of raped children. But it seems to me that one reason we can't deal with raped children is that we have not thought our way through to the wider questions. The zealotry of the pro-lifers has saved us from having to discuss them at all.
And in doing so, it has led us to ignore the majority of Irish people whose genuine compassion for an abused child is held in check by an uncertainty about where that compassion might lead. Unless and until the suspicions of such people are taken seriously, an honest consensus will be impossible to achieve.
Rather than seeking an impossible compromise with the hard core of anti-abortion activists, what we really need is a debate on the proper limits of choice. A small, brave group of people genuinely open to such an exploration could do the country a huge favour by initiating a calm, complex discussion.