As commenter Mike Suarez so cogently writes in this blog thread, we need to be very careful about the "hidden" meanings and assumptions buried in the terms we use. I believe we can learn from observing the history of how the abortion question is framed.
Years ago, the central questions was "when is the human soul formed?" At what point does the tissue within a pregnant woman become a person?
Over the years, the issue has been re-framed as "when does life begin?" Which is an easier question on one level, but which avoids the essential uncertainty of the moral question.
I believe many, if not most, people base their views on abortion on biblical concepts. Most believe the Bible doesn't mention abortion, and thus argue from a "well, God likes life" position.
I urge them to consider the Old Testament's Numbers 5:11-31, in which God sets the procedure for what to do if a husband suspects his wife of infidelity. Obscurely written and even more obscurely translated, God tells us that the wife is to be given "bitter waters" and if she doesn't miscarry, she's innocent. In other words, God says "give her an abortificant."
Which pretty much flies in the face of the "life begins at conception and is sacred" position.
If, because of the terminology, you think that section isn't about abortion, try to determine what else it could possibly be about.
I don't think this bit of scripture ends the discussion, but I think that those who oppose abortion on Judeo-Christian beliefs should deal with it in their analysis.
As someone (Karen Armstrong?) once said on "Speaking of Faith" - if you are going to pursue truth, you have to be prepared to change your mind."
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