I'd like to sum up my arguments here.
ParametersAbortion is a complicated subject. In this post, I'm only going to address whether abortion "should," in general, be legal, at least early in the pregnancy. This post is not a discussion of whether abortion is a good thing, Roe v. Wade or any other court decision, states' rights, late-term abortion, so-called "partial birth" abortion, a potential father's rights, age of consent, parental notification, federal or state funding, waiting periods, or anything else not specifically addressed in this post. Please keep comments constrained to the general topic so as not to get bogged down in a million tiny arguments.
Burden of JustificationMark appears to begin with the assumption that the onus of justification for their position lies on the supporters of legal abortion (SLAs.) He has this backwards. Because opponents of legal abortion (OLAs) wish to criminalize an action, the burden of justification is on them. If I wanted to start a movement criminalizing the practice of eating popcorn in movie theaters, the onus would be on me to justify my position, and not on the popcorn-eaters to justify theirs.
"Abortion is Murder"There are two problems with the argument that abortion should be criminalized because it is murder:
1) It's circular. "Murder" is by definition an unlawful killing, so this argument is akin to claiming that abortion should be criminalized because it's criminal. "Abortion is murder" is no more meaningful then "killing in self-defense is murder," "the death penalty is murder," or "war is murder."
2) "Murder" refers to the killing of a person. However what constitutes a "person" with respect to murder is exactly what this debate is about. The OLA side of the debate argues that a fetus or embryo is, from the moment of conception, a legal and moral person, while most on the SLA side argue that it's not until later on. The following analogy makes clear that even the majority of the people on the OLA side make a moral distinction between fetuses and post-birth persons:
Suppose there is a fire in a fertility clinic. You are the only adult present, but there is one child and a container with 5,000 embryos in the clinic. You can only save one of them -- which do you choose?
Only the most passionate extremist would save the embryos instead of the child, so clearly, most OLAs make a moral distinction between embryos and post-birth people. Killing embryos is therefore not in the same moral category as killing children, even for them.
"My Religion Opposes Abortion"This is not sufficient reason for abortion to be criminalized. Your religion no doubt opposes idolatry as well, but nobody remotely reasonable is arguing that idolatry should be illegal.
"Embryos Have Souls"This is an attempt to rescue the "abortion is murder" argument. If an embryo or fetus has a soul, a majority of people will agree that killing it should be prevented. I won't object to this argument on (non-)religious grounds since even an atheist can see "soul" as a useful metaphor, but there is one insurmountable problem with this argument: there is no consensus opinion for when an embryo or fetus gets a soul. Since a "soul" is undetectable by instruments, there is no empirical way to determine when it enters the body.
Furthermore, religions disagree with each other and, even within religions, opinions vary widely:
1) Orthodox Catholicism
2) Protestant groups, not having a central authority figure, are hard to speak for. However, many protestants and protestant groups are in favor of at least some form of legal abortion, so it's obvious that either they don't believe the soul is imparted at fertilization, or that the presence of a soul is insufficient to criminalize abortion. A notable except are the Baptists, of which a large majority are against legal abortion.
3) Judaism clearly holds that an early fetus does not have the same status as a person. For example, in the Torah it states that a person who kills a woman's fetus must pay monetary damages (rather than being treated as a murderer.) Furthermore, Jewish law mandates abortion if the mother's life is in danger. Conservative Judaism allows abortion "if a continuation of pregnancy might cause the woman severe physical or psychological harm, or when the fetus is judged by competent medical opinion as severely defective." Reform Judaism, the largest denomination of Judaism in America, holds that "[i]n all circumstances, it should be [the mother's] decision whether or not to terminate a pregnancy, backed up by those whom she trusts (physician, therapist, partner, etc.)"
4) As an atheist who can see "soul" only as a metaphor, I would be hard-pressed to believe that an embryo has a soul before it even has a brain, for example. Therefore I cannot oppose early-stage abortion on that basis.
"Actions Must Have Consequences"This argument is so weak I wouldn't include it, but Mark devoted a whole post to it. An excerpt:
...God's green earth is not a playground merely for children and consequences are incurred with every action and every choice we make. Sex is a choice. Pregnancy is a possible consequence every time we participate. The argument that do-overs should and can be applied to pregnancy is basically an admission that this (sex) is an activity which is to be encouraged between (post-adolescent presumably) children (of all ages). When we raise our children, if we free them from the consequences of their actions remain childish and never grow up.
This argument fails as justification for criminalizing abortion because we as a society do not criminalize certain activities merely to punish people for engaging in other ones. For example, suppose a 19-year-old girl binge drinks at a college party and suffers from alcohol poisoning. Would anybody argue that it should be illegal for a doctor to pump her stomach because it would be "basically an admission that [binge drinking] is an activity which is to be encouraged [in] (post-adolescent presumably) children (of all ages)?" Of course not. While society has a vested interest in preventing binge drinking among teenaged girls, it cannot criminalize a medical procedure simply because the procedure alleviates one of binge drinking's natural consequences. (Of course, abortion is not comparable to pumping one's stomach in general, but the distinction between them is not relevant to this particular argument.)