If the moral objection to abortion is that it kills innocent persons, then you are right, the circumstances of conception should be irrelevant.

An important philosophical article by Judith Jarvis Thomson, "A Defense of Abortion" (originally published in Philosophy and Public Affairs in 1971 and widely reprinted) argues that in some circumstances, killing innocent persons is permissible. Those special circumstances are when the life of another is dependent on some huge personal sacrifice of an individual who did not voluntarily take on that responsibility. Thomson argues that when pregnancy occurs against the will of the pregnant woman (rape is clearly an instance of this, and Thomson argues that contraceptive failure is also an instance) it is morally permissible to abort (although it would be morally admirable to go through with the pregnancy).

Perhaps, such positions concerning abortion are based on the idea that a developing fetus is very morally valuable, but not equal in moral value to a fully developed human being. Therefore, something like the great emotional pain involved in being forced to carry a child conceived as the result of rape might be enough to justify an abortion. But, very few things other than the life of the mother or rape would be adequate to justify an abortion.

Or, perhaps, such views on abortion are mainly developed based on political pragmatism.

There are some practical reasons for using viability as the standard for when a fetus may no longer be aborted. In particular, the viability of a fetus means that its life could be sustained without the mother's involvement -- which makes it much easier for others to effectively intervene. With scientific and technological advances, of course, life outside of the womb has become possible at earlier and earlier stages, so that disallowing abortion in cases where the fetus could survive apart from the mother'sbody would effectively disallow abortion during most of a woman's pregnancy.

Moral reasons for emphasizing viability are largely due to the idea that human beings have a right to autonomous existence (an existence which is not dependent on the desires of others) only insofar as they are capable of autonomous existence. (Compare: I have a right to make my own choices only insofar as I am capable of making my own choices.) This rationale is problematic, however, since (a) no baby, let alone a seriously premature baby, is capable of living independently of the desires of others, and (b) even for adults, independence from the desires of others is never complete.

There are a few points that may be relevant to your thinking:

1) There is a substantial difference between 32 weeks and 36 weeks in terms of development, long term prognosis, etc. It is also uncommon for a newborn to be as responsive to social cues as you suggest. Typically "social smiling" doesn't occur until a full term baby is four to six weeks old. It is a mistake, I think, to generalize even about healthy fetuses from the vivid example you've just witnessed.

2) The cases of abortion Tiller performed were typically cases in which the fetus or mother faced significant medical complications. Would you feel differently if your cousin (once removed) was born to live with a disability that would cause constant and untreatable pain? How would you feel if your cousin's life was in danger, or if she faced a permanent and profound disability if she continued her pregnancy? Are there no cases in which you can imagine a late term pregnancy justifiably terminated?

3) It might be interesting to read some of the statements by physicians who provide abortions at Physicians for Reproductive Health and Choice: http://prhc.org, or some of the comments on the memorial page for Dr. Tiller linked to that site.

Let's try some analogies. Suppose U.S. citizens have a constitutionally guaranteed right to vote for President, congressional representatives, etc. Now suppose that anyone who sets up or runs a voting booth is prosecuted for violating a law that says providing outlets for voting is illegal. It seems that this law would violate our constitutional rights. Or try it with the Second Amendment. In general, it is unconstitutional to bar selling guns as well as buying them, presumably since it would violate our right to bear arms if there were no way to get them. Accused defendents' right to legal counsel would be violated if it were illegal to practice law. And so on.

I think that the way you set up the question, by supposing women have a right to abortion, suggests the answer: it would violate that right to make laws entirely restricting doctors from providing abortions.

However, if you did not make that initial assumption about women's right to abortion, then it seems there is nothing inconsistent about outlawing the "selling" of abortions even if the "buying" were not outlawed, though it's unclear why such a double-standard would be in place.

Sometimes this is put as a challenge to those who argue that abortion is morally equivalent to first-degree murder: if you really believe that, then you should advocate punishing women who get abortions as murderers (i.e., not only punishing abortion providers). Of course, some might be willing to bite this bullet. Others might offer arguments for why abortion is wrong but not as wrong as murder. And others would say that the challenge illustrates the moral and legal difference between murdering a (fully-formed) person and aborting a fetus.

Different people will have different views about this, but I think the obvious thing to say is this. Taking the potion you described harms a person who will one day exist. Having an abortion does not harm a person who will one day exist. So that is the difference: In the one case, a person is harmed, but not in the other. That person does not exist at the time the harm is done, but I think you are correct that the person does not need to exist at that time to be harmed.

To see the importance of this, note that a similar case can be described even if the woman takes the potion before any child is conceived. In that case, no independent life exists at all, and yet it seems as if taking the potion is morally objectionable, for much the same reason.

There are complications here, surrounding the idea that the woman's behavior is wrong even if no child is ever conceived, on the ground that she risked harming someone. But I'll leave it to you, and others, to work this out. One important point is that, so far as I can see, "X risked harming someone" does not imply "There is someone X risked harming", any more than "X was baking a cake when she died" implies "There was a cake that X was baking when she died." (X died before any such cake came into existence.)

Let's agree that, from the moment of conception, we have a living thing -- and, if the parents are human, this living thing belongs to no other species than homo sapiens. So what? That fact doesn't in itself determine the moral status of the product of conception.

Here's one possible view: as the human zygote/embryo/foetus develops, its death becomes a more serious matter. At the very beginning, its death is of little consequence; as time goes on its death is a matter it becomes appropriate to be more concerned about.

In fact, that view seems to be exactly the one most of us take about the natural death of human zygotes/embryos/foetuses. After all, few of us are worried by the fact that a high proportion of conceptions spontaneously abort: few of us are scandalized if a woman who finds she is pregnant by mistake in a test one week after conception is pleased when she discovers that the pregnancy has naturally terminated a few days later. Similarly for accidental death: suppose a woman finds she is a week pregnant, goes cross-country horse riding, falls badly at a jump, and spontaneously aborts. That might be regrettable, but we wouldn't think she'd done something terrible by going riding and running the risk. (Compare: we do think it is a matter for moral concern that there are high levels of infant mortality in some countries; we would be scandalized by a woman celebrating the death of an unwanted newborn baby: we would be appalled at someone risking the life of nearly nine-months old foetus by going in for some potentially dangerous sports.)

So: our attitudes to the natural or accidental death of the products of conception seem to suggest that we regard them as of relatively lowly moral status at the beginning of their lives, and of greater moral standing as time passes. It would be consistent with such a view to take a similar line about unnatural deaths. For example, it would be consistent with that to think that using the morning-after pill is of no moral significance, while bringing about the death of an eight month foetus is getting on for as serious as killing a neonate, with a gradual increase in the seriousness of the killing in between.

Now, the point I'm making here isn't that this "gradualist" view is right (actually, I think it is, but you don't have to agree for present purposes). The point is that it that it isn't obvious that it is wrong. In other words, it isn't obvious that an all-or-nothing attitude to members of the species homo sapiens has to be right. It is not obvious that agreeing that the products of human conceptions are also human means that we should assign them all the moral weight we give to developed human beings. There's room for argument.

The idea of giving rights to fetuses as soon as they are capable of consciousness is, I think, discussed in the literature. Fetuses have a functioning central nervous system very early in pregnancy (typically before pregnancy is detected) and possibly consciousness of some sort starts at this point. Probably you should also be willing to extend your ideas about the importance of consciousness to human rights later in life (e.g. to comatose patients).

Some writers on abortion argue that fetuses have rights to life before the onset of consciousness, and perhaps you might be interested at looking at these e.g. Don Marquis.

I wonder what you mean when you say that "many people attempt to devalue the controversy "?

I suppose that it is true that a lot of people are not at all tempted by either "end of the field" -- if that means holding at one end that abortion is tantamount to murder, or holding at the other end that even very late abortions are morally insignificant. Many people think that the moral status of an zygote/embryo/foetus increases as time goes by -- the natural or unnatural death of the immediate product of conception is of little or no consequence, the natural or unnatural death of a foetus near term a matter of very serious concern, with a sliding scale in between. If you take this "gradualist" view -- a rather attractive one, I think -- the loud controversy between extremists at either end will indeed seem wrongheaded: it's not that the gradualist ignores the controversy, or merely ducks out from taking sides, rather she thinks that there is a third option.

I've written a bit more about that kind of gradualism in answer to an earlier question here.