It’s a worthwhile distinction as far as it goes. Ultimately, the “best” argument in defense of abortion is an appeal to agnosticism–that we don’t know when there is a new human. Their best argument fails because of the Deerhunter principle–meaning it is immoral to shoot into rustling bushes without knowing what it is you are unleashing deadly force on.
Watch out for people who try to play various popes and Church doctors against each other over “ensoulment”. The Church has addressed this explicitly. I blogged about it here:
–If one has spent much time refuting arguments in favor of abortion, then they have likely encountered a ploy whereby various popes and prominent churchmen are pitted against each other over *ensoulment *(when newly-conceived humans receive their souls.) The defenders of The Hopeless Position “reason” that this back-and-forth demonstrates confusion in the Church over the issue, and therefore the evil of abortion is not an absolute moral norm, but merely current policy.
For a while I thought somewhere in Church documents there was something that explicitly rejects the idea that the evil of abortion stands or falls on ensoulment, but I could not locate it. Someone at the Catholic Answers’ forums found it. In the Declaration on Procured Abortion footnote 19:This declaration expressly leaves aside the question of the moment when the spiritual soul is infused. There is not a unanimous tradition on this point and authors are as yet in disagreement. For some it dates from the first instant; for others it could not at least precede nidation. It is not within the competence of science to decide between these views, because the existence of an immortal soul is not a question in its field. It is a philosophical problem from which our moral affirmation remains independent for two reasons: (1) supposing a belated animation, there is still nothing less than a human life, preparing for and calling for a soul in which the nature received from parents is completed, (2) on the other hand, it suffices that this presence of the soul be probable (and one can never prove the contrary) in order that the taking of life involve accepting the risk of killing a man, not only waiting for, but already in possession of his soul.So next time you get the Pope Sixtus-vs.-Gregory-in-a-steel-cage-death-match objection, shoot it down with this.–