My post on being a human person has received some interesting comments. The basic point of the post is that it seems an irrational view of personhood to say that being a person consists in a stream of thought in the higher brain. This is essentially a view under which a person is a humunculus in the brain; the humunculus is the person, and because of this, when the humunculus goes away, the person goes away.
The contrary view, which I suggested, is that in human cases this person is this living animal. The point is not that 'human' and 'person' conceptually coincide (so I think the issue about orthogonality ends up being irrelevant). Nothing in this view, for instance, requires us to say that a decaying human corpse can be called a 'person' because it can be called 'human'. Nor is there anything in this view to say that 'person' is a subset of 'human', so that only human beings can be persons. The point is that personhood is in our case attributable to a living individual in virtue of its being a example of the human (and therefore potentially rational) sort of animal. It does not follow from this, by any straightforward inference, that the disappearance of rational functions is the disappearance of the person (which makes, effectively, personhood an effect of an animal body rather than an animal subject). Rather, we have to conclude that the person is this actual animal (something which accords well with what we actually do). That we don't call this actual animal a 'person' for the same reason that we call it an 'animal' isn't relevant.
Now, I said by 'any straightforward inference'. It is possible that, given the right additional suppositions, it might follow from the point made above that actual exhibition of rationality, in the sense of higher-brain activity, is a necessary condition for being a person. But it cannot be merely assumed, and the suppositions on the basis of which this conclusion is drawn must be made explicit. Indeed, as I noted in the post, those who put forward this type of argument have a moral responsibility to make those suppositions explicit and examine them, critically and carefully, to see if they actually hold up; because we know historically that this general sort of move has been made again and again in order to justify heinous behavior toward slaves, other races, women, and the mentally disabled. People who honestly believe that the sort of case involving cessation of higher-brain function is different must show that it is different. And no, making rhetorical claims about how, when higher-brain activity is taken away, we no longer have a person but a clump of meat is not showing anything; such statements are merely a dogmatic pronouncement of the position itself, of the sort I noted in the previous post.