As I stated in a previous article, the Virginia Catholic Conference mentions abortion as an intrinsic evil issue to be addressed in considering who to vote for. Apparently, this is part of a nationwide discussion - one joined by Fr. Charles Curran, who challenges whether abortion is the primary intrinsic evil, given that there is some doubt about when ensoulment occurs. You can read how National Catholic Reporter covered his talk at http://ncronline.org/news/politics/curran-how-bishops-challenge-abortion-laws-flawed.
I disagree with Curran, who quotes St. Thomas Aquinas on ensoulment. So far, neuroscientists have not found the kind of "soul" that Aquinas would expect. Biologists have found, however, that after gastrulation, the developing embryo seems to be acting intentionally toward an end in a way that is not present before that point. Under an Aristotelean, this seems to be evidence of a vital force or soul. This would mean that abortion is wrong, but not artificial birth control or stem cell research.
Curran talks about giving the woman the benefit of the doubt on the abortion question. I don't see this as a question of doubt, but rather as a question of feasibility. It is simply not possible to regulation first trimester abortions where the fetus is recognized as a legal person without investigating every miscarriage - which society would reject. Giving fetuses status would also impact malpractice in this area in such a way as to force obstetricians to not treat first trimester pregnancies at all. Carving out exemptions would simply make any abortion law moot, so such a law would not be practical. Indeed, one could argue that a right to life is meaningless until independent life is possible - at least with assistance. Week 23 seems to be the best marker in this case - although this has nothing to do with ensoulment but instead with the ability to enjoy the right granted.
