The 1967 Abortion Act never said that abortion was moral. It simply said that certain abortions would not be the concern of the criminal law. But practically that legitimised abortion for millions. So, how, do you decide the morality of abortion? Many people play a game of "ethical snap". Someone cites a case of a woman or girl in desperate poverty who wants an abortion; someone then "snaps" that with horrific photos of dead foetuses and dismembered foetal limbs.
The pro-choice people accuse the anti-abortionists of being sentimental in the operating theatre. The pro-life people accuse the abortionists of being sentimental in the counselling room. Others say it is all a matter of motives. If people have good motives that is enough. If they decide with reasonably unselfish motives, that justifies an abortion. But the Bible suggests that while bad motives make good actions morally hypocritical and wrong, good motives do not make wrong actions good. Peter, no doubt, had some good motives in opposing the way of the Cross for Jesus; but Jesus saw that activity as Satanic.
Abortion was common in ancient Greece - hence the Hippocratic Oath for doctors: "Thou shalt not give a woman a pessary to produce an abortion." It was also common in the Roman Empire. By the time of Christ abortion was well-known and common in the ancient world.
But the coming of Christ and the spread of the Christian faith brought a challenge to the practice of abortion. In the period immediately following that of the Apostles - the period of the Fathers - one of the distinctives that marked off the Church from its pagan environment was its opposition to abortion. This was a fruit of the Gospel - the extension of care to the humblest of human "beings", including human foetal life. So early canon law, and then subsequent pronouncements, in general have defended the foetus as "human" or "human on the way" and so worthy of Christian love and protection.
More recently an ethics of "justifiable foeticide" has evolved. This, too, claims a Christian basis, namely that human life itself does not have an absolute, but only a very high value. There may, therefore, be occasions when life can be taken or protection withdrawn. But such a very serious action has to be justified. As with "the just war", the right to do this cannot be presumed. It has to be argued for.
Most would agree that a serious threat to the actual life of the mother is a justifying reason. Some argue that some congenital deformity is a justifying reason (although they would argue that this has to be such that no life outside the womb can be maintained).
But these and other difficult cases are very rare. As we have seen, most abortions are for "social" reasons. That is why the issue is a serious moral issue that Christians cannot ignore. It is the taking of innocent life.
But is it innocent life? Is "human life" being destroyed in abortion or in embryo research? And why should conception be so important? What does the Bible say?
Exodus 21.22 refers to an injury to a pregnant woman. If she miscarries, the claims of the foetus are assessed as less than her own. But violence to the foetus is an offence. Mostly, however, the Bible speaks at a more general level. Ecclesiastes 11.5 says:
As you do not know ... how the body is formed in a mother's womb, so you cannot understand the work of God, the Maker of all things.
Probably the RSV translation is better - "you do not know how the spirit comes to the bones in the womb of a woman with child". This suggests that there should be a certain agnosticism or humility in our thinking about ante-natal life. We, indeed, are not facing a blob of tissue, but a divine mystery; the womb contains not only a body but a "spirit".
The philosophical and basic question is this: whose is the history of that which is in the womb - the mother's or someone else's? The Psalmist had no doubt. It was his history. He was in the womb:
For you created my inmost being; you knit me together in my mother's womb (Ps 139.13).
Isaiah said much the same thing:
Before I was born the LORD called me; from my birth he has made mention of my name (Is 49.1).
Most importantly this is the understanding of the New Testament in the birth stories of Jesus. The incarnation of the Son of God began not with his birth but with his conception.