I waded in late to Katievs's abortion thread on the member feed -- rather than risk running it off the rails -- I thought I'd start my own.
Despite caring deeply about abortion, I have a hard time articulating a position on it. My reason is simple: I find both of the logically consistent positions on it to be morally troubling and downright terrifying in their implications.
The sanctity-of-life variety of the pro-life position argues that all individual humans are fully-ensouled persons from the moment of conception. They are, therefore, of equal moral value to the rest of us. As the Catechism of the Catholic Church puts it:
Human life must be respected and protected absolutely from the moment of conception. From the first moment of his existence, a human being must be recognized as having the rights of a person - among which is the inviolable right of every innocent being to life.
As beautiful as I find that idea, it means that when my girlfriend and I get married and start trying to have kids, nearly a half-dozen fully-ensouled persons are likely to die as a result of our efforts (22% of all conceived zygotes fail to implant). Not to put too fine a point on it, but I would find that -- and the fact that our government sanctions mass-murder of children -- utterly horrifying.
The alternative can best be called the "personhood" argument argument, which holds that we have moral value only by virtue of the level of our moral and intellectual cognition. Or, as professor Peter Singer puts it:
[The argument that a fetus is not alive] is a resort to a convenient fiction that turns an evidently living being into one that legally is not alive. Instead of accepting such fictions, we should recognise that the fact that a being is human, and alive, does not in itself tell us whether it is wrong to take that being's life.
Therefore, babies and young children are of no moral consequence and can be killed with no more concern than we might grant a cow. That, too, I find horrifying (more so than the other position, for the record).
As much as I dislike it, this is why I'm morally most comfortable with what I concede is an intellectually squishy position: that our emotional intuition about the increasing value of human life -- rising sharply during pregnancy and then leveling out over time -- is correct. This why we send flowers to a friend who has had an early miscarriage, but stop everything when the same friend's toddler dies.
As such, I'm comfortable with keeping abortions legal during the first trimester, and am equally uncomfortable with allowing mid- to late-term abortions (the usual caveat of danger to the mother's life aside). I don't particularly like this position, but it's the only one that lets me sleep at night.