I think Matt Franck is being too hard on Charles Krauthammer on the ensoulment point.
From a (Catholic) theological point of view, to say that a being is a “person” is actually the same thing as saying he (or she) has a “spiritual nature,” which, for embodied beings such as ourselves, is the same as saying that he (or she) has a “spiritual soul.” Dogs, precisely because they do not have spiritual souls, are not persons. A space alien who had a spiritual soul would be a person.
Moreover, it is a truth accessible to reason unaided by divine revelation that human beings have a spiritual nature, in the sense of being rational and free and having a soul that is not reducible to matter. So that Krauthammer is precisely correct when he says that the question of whether some being is a person can be “restated in theological terms” as whether he has a spiritual soul. The theology in question is natural theology.
Nor is it a good idea to sneer at the concept of ensoulment as “magical.” It is Catholic doctrine that every human being receives his or her spiritual soul immediately from God rather than the soul being simply generated by natural biological processes (the error of “traducianism”) precisely because the spiritual soul is not reducible to matter. In that sense, every human being is indeed “ensouled” at some point. Catholic theologians in modern times have generally said that ensoulment happens at conception. But the concept of ensoulment is not “magical” or something to be embarrassed about.
It is understandable that pro-lifers are sensitive to the (false) claim that opposition to abortion is based on revealed religion. But the idea of personhood and a rational (i.e. spiritual) nature that qualitatively distinguishes us from lower forms of life is, as I noted above, a truth accessible to “the natural light of reason.”
