I agree with ender that a fetus is a human life (it's scientific fact, but is worth noting when debating this topic). While a fetus is not a "person" in the legal or even colloquial sense, it will be one absent an intervening event (natural or otherwise).
By way of analogy, imagine a great uncle is in the hospital and declared brain dead. The family gathers by the bed to say goodbye. It is acceptable to pull the plug in such a situation because he is basically considered dead. But imagine if suddenly an eyelid fluttered or a finger moved, should we rush to pull the plug before he potentially and miraculously obtains consciousness? No. We are only pulling the plug because of a near certainty that won't happen. Contrast this with a fetus, which in all great likelihood, will attain consciousness. It does not suddenly become more moral depending on when the human life is killed - though it may seem more palatable.
Abortion is more complicated by the fact that it does have a huge impact on the mother's (woman's) life. And unlike the great uncle, a fetus was not previously conscious or considered a person. Depending on the stage, it might not be more than a bundle of non-specialized cells. There is a qualitative difference. Thus even many of the most pro-life of people will be able to make exceptions for rape and incest - because the fetal life is not exactly considered on par with that of the woman carrying it.
CP3, I always appreciate your forceful arguments. But that it can be easier to end a pregnancy than to raise a child doesn't add up to a whole lot in answering questions about morality or public policy. That there are bad parents or kids who in your judgment would be better off never having been born also doesn't answer any question about morality or public policy.
theprequelsrule, your argument that opposition to abortion is rooted in oppressing women doesn't pass the smell test. It is true that women were oppressed in many ways throughout history - even legally considered property of husbands - and I suppose even a woman's pregnancy could have been used to that end. But that doesn't mean the conception of fetal life as precious and human is rooted in oppression of woman.
You propose:
There is only one question that should be asked when it comes to abortion: should a woman have the final say over the fate of something inside her?
Should we ever ask what that "something" is? Reducing it to such vague and simplistic terms does not clarify the issue.
As conceded, it is not an easy issue. Morally, it is difficult to justify abortion - unless the woman herself will die (and even then we could have a prolonged philosophical debate). If we try to make it a more 'practical' matter in which two lives are at stake (like a hypothetical in which two live are at stake and only one can be saved) and try to balance a woman whose "health is severely at risk" with that of the fetus it's tricky to say when mental health is "severely at risk" for that woman who was raped (I'd hate to try to make that determination).
A fetus is not the same as a person, but it is more than a random clump of cells or a defective kidney. When a woman is raped, it is foolish and harmful to force a woman to abide the result of violence upon her. Allowing abortion in this case may be difficult to justify morally, but public policy should take account of the messy and inconvenient nature of reality. Note, this is different from saying that since reality is messy and inconvenient, we shouldn't make many rules at all.
There is no denying the general right of a person to exercise autonomy over their body. But like all rights - it is not absolute. Pregnancy is a unique condition involving another life. When a woman permits herself to become pregnant she takes on a responsibility. Men also take on a responsibility when they cause a woman to become pregnant (intentionally or not).
So where I end up, is believing that abortion should be discouraged and limited, but not outlawed. I can't formulate a complete and ideal set of laws on the topic, but this is where my views are anchored.
Ultimately, the debate over abortion is probably blown out of proportion. Polls show that 70-80% of people in the US want at least some restrictions on abortion. Yet the debate tends to turn into whether abortion should be entirely legal or entirely outlawed. And despite there being broad agreement that abortion should be restricted (for reasons other than oppressing women, presumably), the country is split about evenly as to whether they consider themselves "pro-choice" or "pro-life." In other words, there are probably people using either label who have practically the same moral and public policy views.
The answer to theprequelsrule's question above best indicates whether one identifies as pro-choice. Just as asking whether a fetus is a precious human life indicates whether one is pro-life. These questions do not dictate policy solutions to difficult problems. I can't turn a blind eye to the fact that a fetus is a human life.
P.S. If you love long-winded posts (and parantheticals) you will love my post.