Todd Akin and the Republican platform have highlighted the "personhood" movement to legally define fertilized eggs as human beings with the same constitutional rights born children have.
Proponents argue their case on religious grounds, so it's worth asking what the Bible says about it.
The Bible doesn't talk about abortion, but it does say when a human being's life begins.
Genesis 2:7 is clearest. The first human became a "living being" (nefesh hayah, "a living breath") when God blew into its nostrils and it started to breathe. Human life begins when you start breathing, biblical writers thought. It ends when you stop. That's why the Hebrew word often translated "spirit" (ruah) -- "life force" might be a better translation -- literally means "wind" or "breath."
But what about babies in the womb?
A few passages talk about someone called by God before birth: "The LORD called me from the womb. From the innermost parts of my mother, God named me ... and said to me, 'You are my servant Israel, in whom I'll be glorified" (Isaiah 49:1-3).
Here, the one called is the nation Israel, not an individual. A nation of course can't occupy a womb. The language is figurative not literal. It isn't describing prenatal biology or pinpointing when human life begins. It's affirming God's power and Israel's calling to a special mission in the world.
Other passages make the same point by saying someone's called by God before they're even conceived (Genesis 18:9; 1 Samuel 1:17; Luke 1:31). I've not heard anyone make the case, based on these texts, that human life begins before conception.
It's hard to ask biblical texts the modern question, "when does human life begin?" because the Bible has a very different understanding of human reproduction. Biblical writers don't talk about sperm fertilizing eggs. They talk about male "seed" planted in fertile female ground. Just as a seed becomes a plant when it emerges from the ground, so too a man's planted seed becomes another human being when it emerges from the womb.
The only verses I know that address the legal status of "seed" in the womb come in a brief section of case law.
Exodus 21:22-25 describes a case where a pregnant woman jumps into a fight between her husband and another man and suffers injuries that cause her to miscarry. Injuries to the woman prompt the normal penalties for harming another human being: an eye for an eye, a tooth for a tooth, a life for a life. Killing the woman is murder, a capital crime.
The miscarriage is treated differently, however -- as property loss, not murder. The assailant must pay a fine to the husband. The law of a life for a life does not apply. The fetus is important, but it's not human life in the same way the pregnant woman is.
My impression is that most Americans have a more nuanced and conservative view than the Bible does on this, though we're getting at the same idea: an important moral and legal line is crossed when the fetus can survive outside the womb.
For the Bible, that's when a child is born and starts breathing. For many of us today, it's when a fetus becomes "viable" -- somewhere between 21 and 27 weeks into the pregnancy, thanks to our amazing medical technology.
If something goes wrong late in the pregnancy and the fetus dies, we call it "still birth" and, by law, issue a death certificate.
If the pregnancy ends early on, we call it "miscarriage." It's traumatic, a terrible loss, but most of us think of it differently than we think of a still birth. We don't require death certificates for miscarriages.
Recognizing this difference, the Supreme Court in Roe v. Wade created the "trimester" system to sort through the legal implications of the constitutional "right to privacy" they said we all have as Americans.
The justices ruled that the early and late stages of pregnancy are morally and legally distinct.
Early on, in the "first trimester," the embryo undeniably is human life, but it's not "a human being" in the normal sense of the term. At this stage of pregnancy, a woman's right to privacy trumps any responsibility the state might have to protect the embryo by interfering with the woman's decision to terminate the pregnancy.
Late in the pregnancy, certainly by the "third trimester," however, the child has reached a stage of development that changes its moral and legal status. To protect the rights of the viable fetus, states can put serious limits on a woman's right to abortion, though they must continue to respect her right to self-defense, to terminate the pregnancy to save her own life or prevent serious injury.
In the ambiguous middle of the pregnancy, the "second trimester," the state has to balance the right to life of the unborn with the right to privacy of the woman, a balance that continues to tip toward the fetus as the pregnancy progresses. In this stage, our constantly improving medical technology plays an important role in the moral-legal equation.
Roe doesn't require "abortion on demand" until the moment of birth. Rather, abortion is illegal in most states once the fetus is viable (normally 24 weeks into the pregnancy), unless it's necessary to save the life of the mother or prevent serious physical or mental harm.
I think the moral reasoning of Roe and subsequent Supreme Court decisions reflects what many of us actually think: the moral status of the fetus changes over the course of the pregnancy.
Advances in medical technology affect our opinions about when exactly the line is crossed. But most of us think there's a difference between a recently fertilized egg and a late-term unborn child.
I think that's true even of many people who consider themselves "pro-life." It's implied in their willingness to allow abortion in cases of rape or incest.
No one would argue that a mother can kill the child she just bore because it was conceived through rape or incest. If we really think a recently fertilized egg is morally and legally exactly the same as a child recently born, how can we possibly allow these exceptions for abortion?
Whatever Mitt Romney's reason for supporting "personhood" legislation, his argument that abortion is OK in cases of rape and incest implies that he doesn't really believe that a fertilized egg is morally and legally the same as a born child.
I long for a world where unintended pregnancies and abortions are rare, where every woman controls her own sexuality, contraceptives are easily available for those who wish to use them, and couples make reproductive choices responsibly, with mutual respect and love.
I respect, though I disagree with the conviction of many Americans that a human being's life begins at conception. And I share their belief in the sanctity of life.
I appreciate the biblical view that a human being's life begins at birth. But modern science and medical technology give me a more nuanced and conservative conviction.
The moral view that underlies Roe v. Wade -- that a line is crossed when a fetus becomes "viable" -- seems most plausible, morally defensible, and consistent with the spirit of the biblical view.
I hope that view continues to prevail.