Unanswerable and irrelevant
As far as what the Bible says - "Thou shalt not kill."
The problem with this quote is that it's incomplete: Thou shalt not kill
what? It's pretty clear from the context that at the time it was written it meant "Thou shalt not kill fellow tribesmen": anyone who was not a member of the tribe in whose holy book this was written, was fair game. As were slaves, I suppose, as well as females. Nowadays there seems to be a consensus, though I've never actually seen it stated, that it means "Thou shalt not kill a human being" -- though quite a few people who claim to follow this teaching seem to be rather enthusiastic about killing human beings whom, again, they regard as members of other tribes.
Thus the endless argument over abortion in our culture: Is a fetus, or zygote, or whatever other name is applied to the pre-birth being whom most everyone seems to agree will be a human being after birth, human? If yes, then abortion must be prohibited by the commandment quoted above; if no, then it's not a problem. Endless energy, and endless trees and electrons, have been devoted by partisans on both sides to "proving" their preformed, and hardly disinterested, opinions on the matter.
The very title of this now 20+ page thread is an example of the (sometimes deliberate) lack of precision in many discussions of the issue: What is really being asked is "Who disagrees with Paul that
human life begins at conception?" In so many of these arguments, what I find most interesting is what is
unstated: premises and assumptions.
Here's an alternative look at the subject: When I became formally a Buddhist, I took on the Five Precepts which all Buddhists, lay and monastic, commit to follow. The first of those is commonly stated as "Do not kill." Literally (in the original Pali language) it reads "I undertake the precept to refrain from destroying life." Note that it does not say that the precept applies only to "human life" or any other definable type of life. Just "life".
As for "when life begins" -- or began -- that's one of the questions the Buddha famously refused to answer (along with others like "How big is the universe?"), stating only that the answer is inconceivable to the ordinary human mind. And, he said, it was irrelevant to his work, which was to share and teach the methods he had found which enable one to reduce, prevent and eliminate suffering.
In addition, for a Buddhist the question of "When did life (human or otherwise) begin?" is irrelevant to the First Precept, because it's not about whether or what kind of life is being destroyed, it's about the actor's intention, which determines the character of the act. There is no "sin" in Buddhism, but there is a distinction between what the Buddha called "skillful" and "unskillful" acts: the former tend toward reducing, preventing and eliminating suffering, while the latter tend toward increasing, creating and proliferating suffering -- which is exactly the opposite of what the Buddha, and those who follow his Path, want to accomplish.
While it is true that destroying life, in any form, causes the life destroyed to suffer, this again is not the real point of the Buddha's teaching. If it were, then, like Christians (and even non-Christian members of this culture), Buddhists would be drawn into endless arguments over whether or how much different forms of life are capable of experiencing suffering. For a sincere Buddhist, the Dalai Lama's observation that all creatures have in common the desire to avoid suffering and seek happiness is sufficient.
However, since it is the Buddha's understanding that everything we do comes back to us, one way or another (this is called the Law of Karma), the point of his teaching in the First Precept is this: If we believe we can reduce, prevent, or eliminate our own suffering by destroying life, in any form, we are committing an unskillful act, whose consequences we must eventually experience ourselves. Not because some stern deity will see to it, but as impersonally and inexorably as stepping on a rake and being hit on the forehead by the handle. If you do not wish to suffer, do not cause suffering.
Of course, this view depends on the assumption that destroying life causes suffering. Does it? Well, if I destroy your life, will you experience that as suffering, i.e. an experience you'd rather avoid? Q.E.D.
Having to deal responsibly with the consequences of our actions when we'd rather not is one form of suffering. From the Buddha's point of view, to avoid this "suffering" by destroying life, especially considering that this life was created by our own act, is certainly unskillful. Thus, in nearly all cases, a woman who commits an abortion (or hires it done) is morally no different than a burglar who is caught in the act and kills the witness. "See, I was forced to do it!" doesn't cut it. If you can't do the time, don't do the crime.
As I wrote above, I do not know of any abortion promoter who was aborted emself. (Though I do know of several abortion survivors who are vocal in their opposition to the practice -- which I find somehow unsurprising.) However, by simple logic, I find the conclusion unavoidable that anyone who commits an abortion, as a deliberate, intended act, must emself experience the consequences -- i.e. be the abortee next time around.
So for me, the issue is simple: just another instance of the Golden Rule. When "human" life begins is not the issue; the issue is whether one is behaving responsibly or not. We may believe we can escape suffering by "externalizing" it onto another creature, but ultimately this is a delusion.
