Olson, Eric T. The Human Animal: Personal Identity Without Psychology, Oxford University Press, 1997. 'The Biological Approach,' Eric T. Olson writes, 'is the view that you and I are human animals, and that no sort of psychological continuity is either necessary or sufficient for a human animal to persist through time.' Human 'persons' are selfaware human animals which, as they aren't essentially self aware, aren't essentially persons. Ranged against this position is the 'Psychological Approach,' a family of views according to which 'some psychological relation is both necessary and sufficient for one to survive.' The Psychological Approach (PA) is sufficiently expansive to include the view that you survive because of a relation between your basic mental capacities in a physically continuous realizer. The Biological Approach (BA) merits far more attention than it has received from philosophers, and Olson's lucid defense of it is welcome. His book is full of interesting arguments of which I can consider only the most central. BA might seem to be a non-starter, Olson observes. Suppose your cerebrum is destroyed; your body persists in a vegetative state until (to take a slightly different example from Olson's) O.J. Simpson's cerebrum (not his entire brain, which would bring along the animal) is implanted in it. The resulting person is psychologically continuous with O.J., not you. He has O.J.'s apparent memories, his personality, and he acts on O.J.'s intentions. But that person is you, the person at the beginning of the story, according to BA--which is counterintuitive. Olson attempts to mitigate this intuition, though he is willing ultimately to allow its force. Nonetheless he argues that PA leads to difficulties so formidable that BA is more plausible. The Lockean Account of Personhood (LAP), put simply, is that a person is 'a rational, self-conscious being.' (104) Obviously some account along these lines captures what is interesting and 2 morally important in our concept of a 'person.' Whatever satisfies LAP is a person, regardless of its modal or dispositional properties. But human animals satisfy LAP--they are rational and self-aware, surely. As no psychological relation is either necessary or sufficient for an animal to persist, human persons can survive without any sort of psychological continuity. The 'psychologist,' therefore, must either insist that human animals have psychological persistence conditions or deny that whatever satisfies LAP is a person. As the animal preceded its psychological features, and can outlast them, the first option won't work. And if the psychologist rejects LAP, insisting that the human animal is mistaken in taking itself to be a person, then how can we know we are people? Perhaps I'm just a self-aware animal making that mistake. (106) Note, however, that BA runs into similar difficulties. My brain is as rational and intelligent as I am. When I think 'I am thinking,' my brain thinks the same thing of itself--even though, like me, it doesn't think it's a brain. As Descartes showed, a self-aware being need only recognize itself as a 'thing that thinks'; it can be mistaken about the rest of its nature. So my brain satisfies LAP. But a human animal is distinct from its brain: the animal weighs more, and it, not the brain, has hands. As many human persons are not animals, BA is false. Indeed, my brain's cerebrum satisfies LAP, too. As whatever satisfies LAP is a person, three people are writing this review--a cerebrum, a brain, and an animal. Which am I? If the 'biologist' responds that brains merely generate thoughts, animals are their subjects, so only animals satisfy LAP, the psychologist can make the same claim about animals and persons. And it's hard to deny that brains satisfy straightforwardly the predicate 'is thinking.' Consider scenario 3 S: my brain is taken from my body, which is destroyed, and placed in a vat where it is fed experiences by scientists. Can we plausibly deny that it is thinking? And if my brain is thinking in the vat, surely it was also thinking in the biological vat from which it was removed. Does it stop thinking if we implant it in a brainless body? The biologist might abandon BA and identify human persons with brains. Animals don't think (though we speak loosely as if they do), only the proper part of them that realizes thoughts satisfies 'is thinking.' But this revision threatens to slide into PA, for the cerebrum is the proper part of the brain that realizes thoughts; so (by parity of reasoning) cerebrums, not brains or animals, are persons. And we might take the Aristotelian point that a cerebrum so damaged that it no longer can function to preserve basic mental capacities is a cerebrum 'in name alone.' That is, a cerebrum has such powers essentially, and something that no longer can (or cannot yet) realize them is a 'cerebrum' in a derivative sense: 'that which composed (or will compose) a cerebrum.' So if you are a cerebrum, arguably you survive because of a relation between your basic mental capacities in a physically continuous realizer. But, Olson asks, if PA is true, what is the relation of persons to animals? Psychologists agree that persons are material objects located in the vicinity of human animals; yet the view that the person is 'constituted' by the animal (as the statue is constituted by the lump of bronze) is 'incoherent,' Olson argues. As person and animal are made of the same atoms, in virtue of what do they have different modal properties? What explains the animal's ability to persist through changes the person cannot survive? Suppose a duplicating machine makes a double of Olson out of different matter: it must make of the same atoms distinct objects with different modal properties, an animal and a person. 4 How, Olson asks, does it bestow these different properties on the person? Once again, however, BA has similar problems. I survive in S. If I'm the brain (B), however, I was never the animal (A) from which B was taken, for B was always distinct from A and I share all of B's properties. If BA is true, therefore, A must survive, too. Indeed, as A's 'central control system' remains intact, I've described the limiting case of amputation. After the amputation, however, B is all that's left of A, so A and B are made of the same atoms. Nonetheless they are distinct: A preceded B, and A, not B, once had feet. Indeed, if BA is true, A and B must have different modal properties too. For if B is implanted in a brainless body, I survive; therefore A survives. As there can't be two human animals in the same place and time (as Locke maintains, x constitutes y only if x and y are of different 'kinds'), A must be identical to the resulting animal. Therefore A, not B, will have hands if the implant takes place. In virtue of what do they have these different dispositional properties? Or suppose the duplicator creates in another vat a double of Olson's brain. As this new brain (B*) is realizing thoughts, something satisfies LAP; there is a person in the vicinity (call him 'Joe'). Suppose Joe = B*. Later, the scientists implant B* in a brainless body; Joe survives. As Joe and B* share all their properties, Joe, after the implant, weighs only five pounds. But the resulting animal weighs more; it's no different in any important way from other human animals. Therefore Joe is not that animal; nor is he, after the implant, another animal. (If, after the implant, B* is an animal, the animal that results from the implant contains an animal, its brain, as a proper part, and so do we all.) But Joe, after the implant, is no different from any other human person: there is a functioning brain in a functioning 5 animal, just as in you and me. So if Joe isn't an animal, neither are we. If BA is true, therefore, Joe must be something other than B*, an animal (A*) that comes into being when and where B* does. As Joe survives the implant, so does A*, which (as we saw earlier) must be identical to the resulting animal; so A*, not B*, can have hands and weigh 150 pounds. Consequently, if BA is true, the duplicator must make of the same atoms two objects, a brain and an animal, with different modal properties. How does it bestow these distinct features on the animal? These thought experiments would seem to refute BA unless the biologist embraces objects made of the same atoms but having different modal properties. I think Olson's best hope of escaping his own charge of 'incoherence' is to observe that his argument against PA contains a suppressed premiss: modal differences supervene on structural differences. This is hardly self-evident. Perhaps distinct Aristotelian universals, Man and Brain, enmatter the same stuff, producing structural duplicates with different modal features. In any case, Olson's argument seems more a threat to BA than to PA. For the psychologist has options other than constitution to offer as an answer to the question: What is the relation of persons to animals? A person might be identified with a cerebrum, which, as I suggested earlier, persists only so long as it preserves basic mental capacities. In sum, The Human Animal represents an important beginning: BA warrants further consideration, and the objection that PA leads to ontological difficulties is certainly worth pursuing. So far, however, Olson's arguments invite forceful responses, and his book, while well worth reading, is incomplete in ways that I hope he will remedy. Jim Stone, Philosophy, The University of New Orleans jstone@uno.edu