What makes a person a person, Baker contends, is having a first person perspective (FPP). When a human organism starts having an FPP, something that's a person essentially starts to exist. The organism doesn't have personhood essentially; rather it starts to constitute a distinct entity, an entity that is essentially a person. I am such an entity and you are too. Non-human animals aren't persons, fetuses aren't persons, and at the end of life, if our FPP is extinguished before death, we go out of existence before organic death.
Now you could quarrel with the science here. Maybe some non-human animals do have FPPs. But let's not go there--let's suppose Baker is right about human uniqueness. Even granting that, I'm out of synch with her eagerness to intensify that difference, to make it "ontological"--
My claim is this: However the first-person perspective came about, it is unique and unlike anything else in nature, and it makes possible much of what matters to us. If even makes possible our conceiving of things as mattering to us. The first-person perspective -- without which there would be no inner lives, no moral agency, no rational agency -- is so unlike anything else in nature that it sets apart the beings that have it from all other beings. The appearance of a first-person perspective makes an ontological differences in the universe. (p. 163)She's not satisfied with the thought that humans and dogs are dramatically different. It's not enough to simply say "normal, mature humans have an FPP and dogs don't." That, to her, doesn't do justice to the difference. We must be in an entirely different ontological category from dogs. I suspect she would actually like to be able to consider us immaterial, to make the difference even more dramatic, but she settles for our essential personhood, because she's a materialist. The idea is not only that you should be able to look at your dog and see something in a different ontological category, though that's important to her. You must also be able to say that you were never an entity in that category, and you will never become an entity in that category.
I personally feel perfectly satisfied with merely factual differences between myself and dogs. I have an FPP and probably they don't. I don't need to ontologize the difference and make it starker (this makes me think of Instagram filters, for some reason!). If at the end of life my FPP fades, and very old JK starts seeing the world as a dog does, I don't think that will prevent that individual from being me. If baby JK once saw the world as a dog does, that fact doesn't make me think "that wasn't me." Baker seems to be guided by some sort of moral imperative to draw the sharpest possible lines between persons and non-persons, but I think there are moral costs to doing so. The heavy duty line drawing would surely undermine fellow feeling between ourselves and animals, our future elderly selves, our elderly parents, people with severe cognitive disabilities, etc.
It seems to me we've given enough significance to personhood if we just say that human beings are a kind of creature the normal, mature members of which are persons throughout a major stage of their lives. It's part of my humanity that, if all goes well, I'll spend a lot of my life with the characteristics of personhood. That strikes me as a more accurate representation of the facts than saying that I am essentially a person--that my very existence hinges on retaining the properties associated with personhood.
And now for a more technical objection. Baker thinks persons are constituted by animal bodies, but not identical to them. Persons have some of their properties derivatively--on account of the properties of their animal bodies. We have our weights, for example, derivatively. On the other hand, she thinks persons also have some of their properties non-derivatively or independently. Our FPPs and the abilities associated with them are non-derivative. In fact, she thinks, I have an FPP independently, and the organism that constitutes me has it derivatively. This is taking persons very, very seriously--as having their own independent causal powers.
The Constitution View allows that many of our causal powers are independent of the causal powers of our bodies (i.e., are independent of the causal powers that our bodies would have if they did not constitute persons). Dean Jones [the person] has the power to cut the departmental budget; twenty-one-year-old Smith has the power to buy beer; I have the power to send e-mail from home (p. 218)Imagine the development of a human being over time. At some time or other, the baby crosses the Rubicon. At t minus 1, there was no FPP. At t there is an FPP. There's a change in causal powers. The baby's not cutting budgets, buying beer, or sending e-mail, but what? Well, maybe reacting to a mirror differently. Suddenly, a person is on the scene, merely constituted by the baby-organism, says Baker. And (Baker says) these new causal powers belong to the new person independently; they are not derived from the constituting body.
Why not derived? I think the gloss in the parentheses makes very little sense. The new causal powers are independent (she says) because they are "independent of the causal powers that our bodies would have if they did not constitute persons," she writes. They're independent (period) because they're independent of a certain portion of our bodily causal powers. Which ones? The "animal" ones, the ones we'd have if we didn't constitute persons. I would have thought they could only be independent (period) if they're independent of all of our bodily causal powers, including those associated with the abilities that make us persons.
The whole story here starts to fall apart, when you think about that moment when a person comes into existence. The baby must surely have some new brain activity for the FPP to emerge. This, says Baker, makes another entity come into being, an entity that's essentially a person. But the FPP emerges in the brain. It's got to be true that the baby-organism has that FPP, even if the new entity, the person that's essentially a person, does as well. Why does having a certain brain property that generates an FPP not just generate the further property in the baby of being a person, as opposed to inducing the existence of another entity? You can say it's more intuitive to suppose a person exists, since that allows for essential personhood (which the organism lacks) but that doesn't make it so.