And yet in many places abortions of such a fetus can be done legally. And I believe that the law does relate to the potential. It is what we use to relate the value of "rights", from this all things extend.I'm not going to go on with this any further because I'm getting sucked into another abortion debate and I hate abortion debates. They tend to make me angry and I dislike getting angry. OTOH, your post is reasonable and deserves an answer. So, one last post and then I'm off this thread.
We are dealing with two separate questions here. One is the moral decision an individual -- a woman, in this case -- might make about a particular embryo or fetus. The other is the ethical and legal question of what behavior do we allow and what do we prohibit. I'm solely interested in the latter: the former takes care of itself, in my view.
The legal question can't be reduced to a discussion of potential, I don't believe. It's a question of individual rights and freedom. Given our legal and ethical heritage, there is only one question we can ask: at what point does the developing fetus gain legal personhood and the protection of law?
I, personally, prefer to keep the government out of it until such time that consensus is clear and irrefutable. Very few people wouldn't give a 35 or 36 week fetus legal status, for example: I'm quite willing to concede that consensus exists there.
We have laws against drunk driving because of the potential loss of life, and regulate accordingly. If one is driving drunk and does take a life we consider it murder regardless of intent, because of the loss of the potential of the life taken. If we do not take potential interaction into account there is nothing at all to mourn. If one is driving drunk and takes a fetus regardless of what week, in some places, it can be considered murder. In others that potential has yet to find voice in law.
I think an attempt to separate potential from ethics is impossible, it is that thing by which we determine the value of what was taken through what we consider wrong action.