According to one anthropology, the mother is at least but also more than her fetus’ owner: she is also, ceteris paribus, its natural protector. It is a unique kind of ownership, and the effort to understand the fetus as homesteadable land that _becomes_ a rights-bearer (rather than is one from conception) is (in my opinion) as morally tone-deaf an enterprise as the one that purpoprts to regard it as a “trespasser.”

The Rothbardian-Blockian treatment of abortion prescinds from anthropology and ontology and, of course, theology. It therefore burkes the issue of the value of human persons apart from, indeed prior to, their status as “owners” and “owned.” It presupposes self-ownership — which it selects cafeteria-style from the Christian worldview-menu and then dresses up in secular garb — and leaves the individual free to shop around for a metaphysical home for that presupposition. A very modern gambit, one that generates problems that cannot be resolved on the terms it insists upon. For more of my assertions, which cannot, of course, be defended in a combox, see my sixteen comments appended to Wisniewski’s original critique of Block: http://libertarianpapers.org/2010/16-wisniewski-block-on-abortion/