A reader asks:
I read your article on “What Is the Libertarian Theory of Parental Obligations?” I liked it very much, and I agree with almost everything. I just have one concern: is a person a person from conception?
My dictionary defines person as a human being regarded as an individual. If that is the definition, then yes- clearly both a zygote and a foetus are persons, since they are human beings and can be regarded as individuals. One can also define person in terms of a normative claim: a person is a human being with rights. On this definition, also yes: zygotes and foetuses are "persons" since they are self owners and have rights.
Some people use the term person differently, to imply something along the lines of a human who demonstrates certain capabilities or behaviours. If, for example, you think that one is not a "person" until one demonstrates rational thought, then neither zygotes, foetuses, nor newborns would be "persons" on that kind of definition.
What happens in the debate about abortion is that pro-choicers equivocate between this alternative definition and their own normative claim, thereby smuggling in their normative claim so that it looks like a neutral description. They use a (sometimes hidden or just assumed) premise that rights are based on the acquisition of certain capabilities or behaviours (such as rationality). Following this, they define person as a human who demonstrates the required capabilities or behaviours to be granted rights.
Since I deny the premise, I also reject this definition. But those who do want to use this definition need to bite the bullet and accept that not just foetuses but also newborns cannot be persons, according to their definition. This is why any justification of abortion is also a justification of infanticide because you cannot logically deny rights to the unborn without also denying them to newborns.
The only coherent framework of rights is inherent rights. Human beings start out as self owners from the beginning because an individual always has the best claim to his own body (even when he is still a zygote). Everyone must start with the presumption of rights for all other individuals they encounter. One can only deny rights to another legitimately if that other individual has committed an act of aggression.