For the complete text, including illustrations, introductory quote, footnotes, and commentary on the reaction to the originally published article see Billions and Billions.
The attempt to find an ethically sound and unambiguous judgment on when, if ever, abortion is permissible has deep historical roots. Often, especially in Christian tradition, such attempts were connected with the question of when the soul enters the body--a matter not readily amenable to scientific investigation and an issue of controversy even among learned theologians. Ensoulment has been asserted to occur in the sperm before conception, at conception, at the time of "quickening" (when the mother is first able to feel the fetus stirring within her), and at birth. Or even later.
Different religions have different teachings. Among hunter-gatherers, there are usually no prohibitions against abortion, and it was common in ancient Greece and Rome. In contrast, the more severe Assyrians impaled women on stakes for attempting abortion. The Jewish Talmud teaches that the fetus is not a person and has no rights. The Old and New Testaments--rich in astonishingly detailed prohibitions on dress, diet, and permissible words--contain not a word specifically prohibiting abortion. The only passage that's remotely relevant (Exodus 21:22) decrees that if there's a fight and a woman bystander should accidentally be injured and made to miscarry, the assailant must pay a fine.
Neither St. Augustine nor St. Thomas Aquinas considered early-term abortion to be homicide (the latter on the grounds that the embryo doesn't look human). This view was embraced by the Church in the Council of Vienne in 1312, and has never been repudiated. The Catholic Church's first and long-standing collection of canon law (according to the leading historian of the Church's teaching on abortion, John Connery, S.J.) held that abortion was homicide only after the fetus was already "formed"--roughly, the end of the first trimester.
But when sperm cells were examined in the seventeenth century by the first microscopes, they were thought to show a fully formed human being. An old idea of the homunculus was resuscitated--in which within each sperm cell was a fully formed tiny human, within whose testes were innumerable other homunculi, etc., ad infinitum. In part through this misinterpretation of scientific data, in 1869 abortion at any time for any reason became grounds for excommunication. It is surprising to most Catholics and others to discover that the date was not much earlier.
From colonial times to the nineteenth century, the choice in the United States was the woman's until "quickening." An abortion in the first or even second trimester was at worst a misdemeanor. Convictions were rarely sought and almost impossible to obtain, because they depended entirely on the woman's own testimony of whether she had felt quickening, and because of the jury's distaste for prosecuting a woman for exercising her right to choose. In 1800 there was not, so far as is known, a single statute in the United States concerning abortion. Advertisements for drugs to induce abortion could be found in virtually every newspaper and even in many church publications--although the language used was suitably euphemistic, if widely understood.
But by 1900, abortion had been banned at any time in pregnancy by every state in the Union, except when necessary to save the woman's life. What happened to bring about so striking a reversal? Religion had little to do with it. Drastic economic and social conversions were turning this country from an agrarian to an urban-industrial society. America was in the process of changing from having one of the highest birthrates in the world to one of the lowest. Abortion certainly played a role and stimulated forces to suppress it.
One of the most significant of these forces was the medical profession. Up to the mid-nineteenth century, medicine was an uncertified, unsupervised business. Anyone could hang up a shingle and call himself (or herself) a doctor. With the rise of a new, university-educated medical elite, anxious to enhance the status and influence of physicians, the American Medical Association was formed. In its first decade, the AMA began lobbying against abortions performed by anyone except licensed physicians. New knowledge of embryology, the physicians said, had shown the fetus to be human even before quickening.
Their assault on abortion was motivated not by concern for the health of the woman but, they claimed, for the welfare of the fetus. You had to be a physician to know when abortion was morally justified, because the question depended on scientific and medical facts understood only by physicians. At the same time, women were effectively excluded from the medical schools, where such arcane knowledge could be acquired. So, as things worked out, women had almost nothing to say about terminating their own pregnancies. It was also up to the physician to decide if the pregnancy posed a threat to the woman, and it was entirely at his discretion to determine what was and was not a threat. For the rich woman, the threat might be a threat to her emotional tranquillity or even to her lifestyle. The poor woman was often forced to resort to the back alley or the coat hanger.
This was the law until the 1960s, when a coalition of individuals and organizations, the AMA now among them, sought to overturn it and to reinstate the more traditional values that were to be embodied in Roe v. Wade.