Too often, when debating the very real and morally tricky question of abortion, both sides are guilty of painting both the issue and each other with broad brushstrokes, unfairly demonizing their opponents and making it hard to work on solutions to even those problems that both sides agree on. This is, obviously, unproductive.
Just to lay my biases on the table, I am firmly in favor of legal abortion, though with restrictions on late-term abortions. However, I by no means find abortion to be a good, or even morally neutral, act--merely, in far too many cases, the lesser evil. If I could genuinely reduce the demand for abortion--that is, the number of unintended and unwanted pregnancies--I would be cheerfully in favor of this. But, because of my views, I do find it easier to see the flaws in pro-life arguments than in pro-choice arguments, so make what allowances you will for this.
The major flaws I see on the pro-life side of the debate are treating a zygote as the exact moral equivalent of an infant, treating pregnant women as mere incubators instead of as moral figures in their own right, and assuming that pro-choice advocates all think of abortion as good instead of as a sometimes-necessary evil.
Not many people (relatively, at least) believe that a small clump of largely undifferentiated cells is truly the equivalent of a full-grown squalling infant. Most of the time, arguments of this nature rely on a slippery slope--the fact that there's no reasonable point at which you can say "Yesterday this was a blob of cells, but today it is an infant", except possibly at conception or birth--both points where very few people argue the line should be drawn. But we draw arbitrary lines across fuzzy moral issues all the time, out of necessity. Consider, for example, age-of-consent laws. There is no magical difference in maturity between someone who is seventeen and 364 days, and someone who is eighteen. But, in some states at least, it is a crime to have sex with the first, but it is never a crime to have sex with the second. These laws are in place because there is a very, very real difference in maturity between an eighteen-year-old and, for example, a twelve-year-old, and the line has to be drawn somewhere. Statutes of limitations are another example--you do not magically become less guilty of a crime after the statute of limitations has run out, morally speaking, but the law justly recognizes that people should not be pursued indefinitely for relatively minor crimes.
I cannot speak to the question of souls, and no one can truly know at what point we gain them. However, minds are an easier question to answer. Though there is some debate about what, exactly, constitutes evidence of a mind, there is no reliable scientific source that shows anything like meaningful development of brain activity before the second half of the pregnancy, and probably well into the second half of pregnancy. In fact, the development of a mind in a reasonable sense may not occur until as late as 2 months before birth. This implies, then, that in a meaningful moral sense, a first-trimester or early second-trimester fetus or embryo is not a person, at least not yet. This is one of the things that makes abortion substantially different from the infanticide that pro-life advocates sometimes compare it to.
The other difference is that, until relatively late in pregnancy, the mother's uterus is the only place an embryo or fetus can survive. The moment we develop a practical uterine replicator, the abortion debate will shift enormously--but, until then, we need to remember, in our arguments, that pregnant women are people rather than just incubating equipment.
Even in this day and age, pregnancy and childbirth carry serious risks. Deaths due to pregnancy or childbirth are admittedly rare with modern medical care, but not nonexistent. And considerably less rare are less serious (but still nontrivial) complications such as gestational diabetes. Even a pregnancy with no true medical complications is a severe strain on the mother's body. Pregnancy is also an emotional strain, and an economic strain. Even if a woman choses to give up the child afterwards, pregnancy itself is an enormous burden. No one should be forced to take up that burden because of a single bad decision or faulty birth-control device.
But it is largely a straw-man argument to claim that most pro-choice advocates encourage abortion. It could be that I am working from a nonrepresentative sample, but no one I know would discourage someone who thought she could handle it from bringing a pregnancy to term, absent severe risk to the mother or a severely deformed fetus; and no one I know would force any woman or girl who is even moderatelymentally competent to have an abortion. And, just to clarify, by "severely deformed fetus", I do not mean "has some problems", I mean more along the lines of "is unlikely to reach age 2" or "will have the approximate cognitive capacity of a small rodent". Pregnancy is a risk and a burden, and like most self-sacrificing choices or tasks for another's benefit, is a noble thing. Except in a very few cases, I think bearing a child to term is the morally better choice. It's just that I don't think anyone should be required to be noble, and at least early in pregnancy, I consider the right of a woman to avoid that burden more important than the fetus's right to exist.
