When does an individual human's life begin?

Yesterday the FDA approved Plan B—the morning-after pill—for over-the-counter sales to 17-year-olds (though not until certain labeling changes are made). Web information about Plan B stresses that the method "isn't effective if you're already pregnant, and it won't terminate an existing pregnancy." According to the prescribing information document, it works "principally by preventing ovulation or fertilization.... In addition, it may inhibit implantation."

Does this mean Plan B is an abortifacient? Can there be an abortion without a pregnancy? And when does an individual human's life begin?

Last August Tom Brokaw asked Nancy Pelosi when she believes life begins, and she has been widely criticized for her answer: "I would say that as an ardent, practicing Catholic, this is an issue that I have studied for a long time. And what I know is, over the centuries, the doctors of the church have not been able to make that definition."

Pelosi was half right: theologians have indeed differed widely as to the exact time of "ensoulment," that is, when the soul enters the body and the fetus becomes human. Nevertheless, as Michael J. Gorman has shown in Abortion and the Early Church: Christian, Jewish and Pagan Attitudes in the Greco-Roman World, from its earliest days the church has opposed abortion, even though abortion was frequent in the Greco-Roman world. And the Catholic catechism is clear about what the church teaches today: "Human life must be respected and protected absolutely from the moment of conception"-- which the church defines as the moment of fertilization.

Conception, however, can mean implantation rather than fertilization, and that is the meaning used by writers of Plan B's ad copy.

After the human egg is fertilized, from eight to eighteen days go by until it completely implants in the uterus and pregnancy begins. According to the definition used by many in the scientific community, until a fertilized egg has implanted in a woman's uterus, she has not conceived and is not pregnant, even if the fertilized egg is in her body. And if she is not pregnant, abortion is not possible. Therefore, it is reasoned, Plan B pills do not cause abortions.

The question remains, of course: does Plan B take human life? Is the fertilized egg a human person before pregnancy occurs? This is a question of faith, not science. For Christians who believe that human personhood begins with fertilization, Plan B is morally wrong. Other Christians, who also consider themselves pro-life and anti-abortion, argue that human personhood begins with implantation; for them, Plan B may be morally neutral.

As one who has favored the first group, let me give a few arguments on behalf of the second. In some ways, implantation may be a better model than fertilization of when embodied life--the union of dust and spirit--begins.

First, human beings are more than genetic codes: we require community and nourishment in order to live. Implantation brings the developing cells into community with their mother and provides them with food and hormones and everything else they need.

Second, each human being is a unique and unrepeatable individual. Until implantation is achieved, the developing cells may split into twins or triplets. Individuality is not assured until the cells attach to the uterus.

Third, fertilization can occur in a laboratory, but--so far, at least--no baby will result unless at some point implantation occurs.

And yet the fertilized egg has its very own DNA, and perhaps this is reason enough to consider it fully human. To some, though, that sounds rather disembodied. Does a cell with a DNA code have infinite value, the same as cells that have burrowed into their mother's womb and established a relationship with her that she feels in every part of her body? Is human nature based in a code or in a relationship?

These are important questions with implications not only for the morning-after pill, but also for assisted conception and embryonic stem-cell research. The answers to these questions are not as clear as some of us would like. They can't be found in the Bible or in scientific journals, though both sources contribute to our understanding of the issues involved. Christians of good faith disagree. As human beings who thrive in community, we need to keep our voices down and listen to others, as we would have others speak softly and listen to us.