Well, since we’re on the topic of the personhood of non-human entities, here’s an article by Margaret Somerville, a Canadian law professor, arguing that we shouldn’t apply the concept of “person” to non-human animals (via the First Things blog):

My reasons for rejecting personhood for animals include that it would undermine the idea that humans are “special” relative to other animals and, therefore, deserve “special respect.”

Professor Somerville cites the views of Peter Singer, among others, to show that attributing “personhood” to animals would blur the boundary between humans and non-human animals which would lead to bad consequences, such as euthanasia. This is because Singer, et al. understand personhood to be a category that is tied to having certain capabilities (e.g., for self-reflection). By this criterion, some animals would count as persons, but not all humans will (e.g., infants, the severely mentally disabled).

Prof. Somerville rejects this capabilities approach to defining personhood and says that the category should be restricted to only (and all) human beings:

The contrasting approach, which I believe is the one we should continue to uphold, is that all humans are persons (at least, as the law stands at present, those humans who have been born) and only humans are persons. This accounts for using the words “human being” and “person” interchangeably. Universal human personhood means that every human being has an “intrinsic dignity” that must be respected that comes simply with being human; having that dignity does not depend on having any other attribute or functional capacity. This is a status approach to who is a person.

The closest Prof. Somerville comes in identifying any substantial human characteristic that justifies ascribing personhood to (only) us is to say that “we humans have a ‘human spirit,’ a metaphysical, although not necessarily supernatural, element as part of the essence of our humanness.” But without further specification, this is either a reversion to some variant of the capabilities definition or essentially an arbitrary decision to confine the label “person” only to humans. After all, traditional philosophy and theology typically defined the “human spirit” precisely in terms of the sort of capabilities (rationality, free will, etc.) that Prof. Somerville earlier rejected as necessary conditions for personhood. It seems that what she’s advocating is a kind of metaphysical fiction–that we act “as if” human beings have an essentially undefinable metaphysical spark that confers personhood.

For my money, if we want to say that humans, qua humans, are more valuable than non-human animlas, then we’d do well to drop “person” as a moral category altogether. There is just no non-question-begging bright line to be drawn between persons and non-persons that includes all and only humans in the category of persons. If you say that “person” means an entity with properties x, y, and z, then you simply can’t rule out the possibility that some animals will end up counting as persons and some humans won’t. But if, on the other hand, you’re just going to restrict “person” to human beings by fiat, then why do you need the concept of person in the first place? What philosophical or moral work is it doing?