To be a human being is to be a social being, part of a human society. Nothing is a better example of a "social" concept than the very concept of murder. It is not a mere killing, it is a special intentional killing, not part of justified war or a legal process regarding crimes against humanity, or the administration of euthanasia. And it is a crime, which means it is not allowed by society, determined by society, and punished society. After it has been done by one or more members of society to other members of society. And the justification for the punishment is that it will lower the number of such crimes committed within society in the future of that society. The universal definition and prohibition of murder are noted especially in advanced societies of the last few thousand years, for example Babylonian, Hebrew, and Roman law schemes. Animal species not much different from human genetically may feature an activity like murder as a normal advancement protocol. It has long been my guess that the first legal prohibitions of murder were not originally intended to provide people with rights (the right to life) but rather than to keep the hierarchies of society stable and the operations of society efficient. Prohibiting murder in general (if not necessarily in all cases as we would define them now--even fairly large societies had ritual killing) is therefore and obviously the first step in creating a mass society, a great civilization.
Since a human being is a social being, it is unavoidable that the life of a human being begins at birth. That is when a human being enters society. What is created by conception is not a social being but a biological one, scientifically known as zygote, which grows through several phases, but becomes part of human society, a bio-social entity known as a child, at birth.
I have no problem with abortions, I think safe and hygenic abortions are a good idea in all cases where children are unwanted by their mothers*, and should be free and encouraged in those cases. One should not feel guilty about needing or having had an abortion. I have no problem with an abortion up to the point of natural birth, following my understanding of when the life of a human being begins. However I consider schemes which only consider abortion to be legal until the point of fetal viability also to be quite reasonable, and I find Roe V Wade to have been real world legal greatness of the highest order. Lawyers familiar with Roe have often praised it.
(*The father's body is not involved even immediately before conception. The father's interest ought be legally immaterial. However, a father who wants a child, and can afford to support it, can possibly persuade the woman to carry the child. A father who didn't want the child has an unavoidably weak hand, I think it is not unreasonable if he be committed to support even a child he didn't want, though each case may need to be considered in its details. The mother's physical burden is greater, so each sex has its burden.)
Mostly unrelatedly, I also believe the human population needs to be reduced, as quickly as possible, but not harming human or non-human beings, from current 7 billion to somewhere around 3 billion under ideal circumstances. It's hard to believe such a harmless reducly could ever happen, but it obviously could do so reasonably quickly if each person is would choose or could be restricted to fathering or birthing one child. I believe preferences are easily moved by society, a society committed to such change could easily do so without the use of physical force. The problem is only that so many entities in society are opposed to such change because population growth is what makes them great (or, less charitably, it is what they feed on). Religious entities the most common offender here. Nations have been so also.
With anthropogenic carbon forcing underway, which threatens great catastrophes in the near future, a smaller number even might be preferable. I have also heard estimates of the best number which ranged down to 0.5 billion, and personally I long held the notion that 1 billion would be best and most sustainable human population.
We could also solve our global warming problem with drastic we use energy, so why blame the birthing of children? Because it isn't happening either way, and likely to make the changes we need to make both kinds of changes will be needed to minimize suffering.
Given that, I especially would have the law not encourage birthing in any way, including by restricting abortion in any way. The only limitation with the importance of this is that allowing free, or even payed abortions (I would government pay all costs associated with having an abortion, including access to the abortion center--reimbursing patient travel costs if needed) wouldn't really make that much difference in the overall birth rate. The bigger wins are in other areas, educating women, access to conception and family planning services, changing the social acceptance of such things (as well as the need for these changes). Abortion is small potatoes in managing global population.
Since it is comparatively unimportant in that scheme, the principal motive for making abortion free is compassion for the mother, the unborn, and the would-otherwise-be-unconceived. Availability of abortion is also of great concern to compassionate potential fathers. I believe in all cases where a woman would prefer abortion, it would probably be better if she had one, for all concerned. The unborn may lose the potential of becoming a human life, though most likely a tragic human life of unneeded suffering.
Would I choose to lead a tragic life of unneed suffering? No. Would I want to create a tragic life, when I would otherwise have a later opportunity to create a fine one? I try to make the choices that lead to the greatest happiness and the least suffering. If terminating one unborn life makes it possible to create one later with far better chances for happiness with minimum suffering, I would go for it. In my calculus the unconceived has as much moral authority as the unborn.
Anyway, tonight at the Texas Freethought Convention debate I did not hear an argument like mine from the pro-choice advocate favored by me and most people in the room. Instead he relied on an entirely different argument to defend abortion, an argument which also demonstrates the need for free abortion but without explicitly making ANY claim about the beginning of the life of a human being. I hadn't heard this argument before, and I think it is also a fine one. I wonder, however, why the debater did not choose to make any statement wrt to the beginning of human life. I beleive my version, as described above, but I haven't heard it debated in any debates, perhaps there is a weakness I am missing.
The argument this debater made was to start with the question, should a parent be compelled to give up a kidney to save the life of his or her child? The obvious answer is that it might be wonderful if parents did this in many cases, but in no way should we legally compel people to do such things. Abortion is a similar situation. In no way should we compel a woman to have her body used to support the life of another being, regardless of whether that being is a zygote, fetus, or child.
This indeed may be a better argument than mine, so I can see that a debater would choose to emphasie it, and even exclusively rely on it. However at no point would he be nailed to saying that a human life actually begins, so he did not contradict me in any way either. Really, the implied beginning of life in his argument is viability. If a birthed fetus is viable, then it is human, otherwise not.
I felt sorry for the anti-abortionist, who had come to her position despite being an athiest, and particularly that she had to make her argument before a mostly unsympathetic audience. But she basically used stock arguments, assertions really, about the beginning of life at conception,* and therefore the need to prohibit abortion, with the same penalties as murder, even in cases of rape, incest. On danger to the mother's life, she immediately dismissed all claims of psychiatric illness or stress, only in cases where the mother would a decion have to be made as to which one to save. Then she showed particularly gruesome pictures of post-abortion remains. Considering the latter, or even the whole by my value system, which actually cares how well people feel, I found her whole presentation disgusting.*
The argument (and her personal motivation, as an Asian) about the need to control abortion for the sake of societies which prefer men so much? So she would have women and unborn children suffer for the sake of their stupid and unchanging society? Actually, as some people have pointed out, these defective social preferences are self-curing, and women need not be made to suffer in the process. Soon, women will be quite valued, at last. There will be no other option left to these societies.
(The presentation of gruesome pictures relies on the natural queasiness people have when initially unexposed to such pictures, and on sentimentality for the human form. It should always be recalled that excessive population growth has not only eliminated available resources but literally made many animal species extinct. So we happily make other species extinct, but cannot bear to see our own blood.)