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Australasian Journal of Philosophy Vol. 72, No. 2; June 1994 IS PSYCHOLOGY RELEVANT TO PERSONAL IDENTITY? Eric Olson Could we outlive, or be outlived by, those human organisms that are so intimately con- nected with us? Many philosophers think so, and they often tell stories like these: 'If all my psychological features were permanently wiped out, but in a way that left this human organism (the one you point at when you point at me) intact and alive, I should cease to exist and that organism would outlive me. If, on the other hand, you destroyed this organism, but only after removing my cerebrum from my head and implanting it into another, I should outlive that organism. For there would still be exactly one person who would be able to remember my life, and whose memories and character were caused in the appropriate way by mine.' According to this highly popular view, a person's persistence consists in a relation that is essentially psychological. This relation may need to be restricted in some way: perhaps I persist only if no more than one person can remember my life, or only if that person's memories are connected in a physically continuous way With my experiences. But some relation involving psychological continuity, they say, is both necessary and sufficient for a person to exist at two different times. Let us call this view the PsychologicalApproach to personal identity? Arguments for the Psychological Approach based on science-fiction stories are as common as can be. But philosophers have had much less to say about the ontological Philosophers who accept some version of the Psychological Approach include H.P. Grice, 'Personal Identity', Mind 50 (1941) pp.330-350; Mark Johnston, 'Human Beings,' The Journal of Philosophy 84 (1987) pp. 59-83; David Lewis, 'Survival and Identity,' reprinted in Philosophical Papers, Vol. 1 (New York: Oxford University Press, 1983); John Locke, An Essay Concerning Human Understanding, Book ll, ch.27; Harold Noonan, Personal Identity (London: Routledge ,1989), see esp. p.13; Robert Nozick, PhilosophicalExplanations (Cambridge, MA: Harvard University Press, 1981), ch. 1; Derek Parfit, Reasons and Persons (Oxford: Oxford University Press, 1984); Anthony Quinton, 'The Soul', The Journal of Philosophy 59 (1962) pp.393-403; John Perry, 'Can the Self Divide?' The Journal of Philosophy 69 (1972) pp.463-487; Sydney Shoemaker in Sydney Shoemaker and Richard Swinbume, Personalldentity (Oxford: Blackwell, 1984); Peter Unger, Identity, Consciousness and Value (New York: Oxford University Press, 1990); and David Wiggins, Identity and Spatio-Temporal Continuity (Oxford: Blackwell, 1967). I confess that this list may be contentious. Unger, for example, is at pains to argue against what he calls 'psychologically based' theories of personal identity. But his own view is that some sort of psychological continuity, provided that it is continuously physically realized (and that 'branching' is ruled out), is both necessary and sufficient for us to persist (see p.140). Thus his theory is a version of the Psychological Approach as I have defined it, and my arguments against that approach apply to Unger as well. Even Johnston, after a trenchant critique of views on which personal identity consists solely in psychological continuity, writes, Rather than see ourselves as minds whose particular embodiments are contingent, we will see ourselves as human beings: that is, beings which necessarily are normally constituted by human organisms, and whose conditions of survival deviate from those of their constituting organisms only because a human being will continue on if his mind continues on... [p.64] And Wiggins, who now seems to oppose the Psychological Approach, once wrote, We are not identical with our bodies... The concept which belongs to physiological sci- ence is human organism, human body, or whatever. We can imagine such things being replenished with spare hands, spare kidneys and with spare brains. The repair need not pre- 173 Downloaded by [University of Sheffield] at 10:45 21 April 2015

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Australasian Journal of Philosophy Vol. 72, No. 2; June 1994

IS PSYCHOLOGY RELEVANT TO PERSONAL IDENTITY?

Eric Olson

Could we outlive, or be outlived by, those human organisms that are so intimately con- nected with us? Many philosophers think so, and they often tell stories like these: 'If all my psychological features were permanently wiped out, but in a way that left this human organism (the one you point at when you point at me) intact and alive, I should cease to exist and that organism would outlive me. If, on the other hand, you destroyed this organism, but only after removing my cerebrum from my head and implanting it into another, I should outlive that organism. For there would still be exactly one person who would be able to remember my life, and whose memories and character were caused in the appropriate way by mine.'

According to this highly popular view, a person's persistence consists in a relation that is essentially psychological. This relation may need to be restricted in some way: perhaps I persist only if no more than one person can remember my life, or only if that person's memories are connected in a physically continuous way With my experiences. But some relation involving psychological continuity, they say, is both necessary and suff icient for a person to exist at two different times. Let us call this v iew the PsychologicalApproach to personal identity?

Arguments for the Psychological Approach based on science-fiction stories are as common as can be. But philosophers have had much less to say about the ontological

Philosophers who accept some version of the Psychological Approach include H.P. Grice, 'Personal Identity', Mind 50 (1941) pp.330-350; Mark Johnston, 'Human Beings,' The Journal of Philosophy 84 (1987) pp. 59-83; David Lewis, 'Survival and Identity,' reprinted in Philosophical Papers, Vol. 1 (New York: Oxford University Press, 1983); John Locke, An Essay Concerning Human Understanding, Book ll, ch.27; Harold Noonan, Personal Identity (London: Routledge ,1989), see esp. p.13; Robert Nozick, PhilosophicalExplanations (Cambridge, MA: Harvard University Press, 1981), ch. 1; Derek Parfit, Reasons and Persons (Oxford: Oxford University Press, 1984); Anthony Quinton, 'The Soul', The Journal of Philosophy 59 (1962) pp.393-403; John Perry, 'Can the Self Divide?' The Journal of Philosophy 69 (1972) pp.463-487; Sydney Shoemaker in Sydney Shoemaker and Richard Swinbume, Personalldentity (Oxford: Blackwell, 1984); Peter Unger, Identity, Consciousness and Value (New York: Oxford University Press, 1990); and David Wiggins, Identity and Spatio-Temporal Continuity (Oxford: Blackwell, 1967).

I confess that this list may be contentious. Unger, for example, is at pains to argue against what he calls 'psychologically based' theories of personal identity. But his own view is that some sort of psychological continuity, provided that it is continuously physically realized (and that 'branching' is ruled out), is both necessary and sufficient for us to persist (see p.140). Thus his theory is a version of the Psychological Approach as I have defined it, and my arguments against that approach apply to Unger as well. Even Johnston, after a trenchant critique of views on which personal identity consists solely in psychological continuity, writes,

Rather than see ourselves as minds whose particular embodiments are contingent, we will see ourselves as human beings: that is, beings which necessarily are normally constituted by human organisms, and whose conditions of survival deviate from those of their constituting organisms only because a human being will continue on i f his mind continues o n . . . [p.64]

And Wiggins, who now seems to oppose the Psychological Approach, once wrote, We are not identical with our bodies . . . The concept which belongs to physiological sci- ence is human organism, human body, or whatever. We can imagine such things being replenished with spare hands, spare kidneys and with spare brains. The repair need not pre-

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consequences of that view. I will argue that the Psychological Approach faces ontologi- cal difficulties far more serious than its proponents have suspected. The problems arise because that view apparently entails that you and I are not human animals - - we are not members of the species Homo sapiens. If we can outlive, or be outlived by, 'our ' organ- isms, we cannot be those organisms, for a thing cannot outlive itself. But few friends of the Psychological Approach have thought carefully about what sort of beings we might be, if we are not animals, or about how we are related to those human animals that, except in science fiction, so faithfully accompany us throughout our lives. I will argue that there are no satisfactory answers to these questions. Or at any rate I will try to show that the range of possible answers is so problematic that we ought to consider giving up the Psychological Approach.

Now a few friends of the Psychological Approach have claimed that we are human organisms, avoiding the difficulty I mean to exploit. 2 They believe that, because of their intelligence, human animals have a criterion of identity radically different from that of most of their evolutionary cousins. (I take it that gazelles and goldfish do not persist in virtue of psychological continuity.)

Those philosophers believe that I have described the 'obl ivion ' and ' transplant ' cases incorrectly. Imagine once more that my psychology is destroyed in a way that does not cause death in the ordinary sense (my heartbeat, respiration, and other vital processes continue without interruption). Their view is that this human organism would not outlive me, in that case, but would cease to exist when I do (since I am that organism). The ani- mal that results from the memory-loss, they say, is numerically different from the one that suffers it?

They also believe that if my cerebrum' is transplanted into another head, carrying all my psychological features along with it, the living, breathing, but brainless human organism left behind would not be the animal once associated with me. That animal, they say, briefly becomes a naked cerebrum, a hunk of tissue which is no more a living

continuecL . . serve character-continuity or memory-continuity. But if this is the physicalistic way of look- ing at the individuation of persons then the way of physicalism is wrong. [pp.57f.; see also p.51]

This clearly implies that we could not survive radical psychological discontinuity. 2 Unger says that each of us was once a week-old fetus, which at least suggests that we are human

animals (op. cit., p.6). And Thomas Nagel, while saying that we are animals, also claims that one survives as long as the seat of one's experiences and one's capacity to reidentify oneself by means of personal memory is preserved ('I could lose everything but my functioning brain and still be me'). This suggests that the continued existence of certain psychological capacities (if not psychological continuity itself) is necessary for us to persist, and thus that our criterion of identity is not narrowly biological. (The View from Nowhere (New York: Oxford University Press, 1986) pp.40-42.) But 1 may be misreading Nagel. Several friends have tried to persuade me that I am not a 'mere' human organism but a 'func- tioning' organism (or perhaps a 'functioning' brain), where functionality implies retaining cer- tain psychological capacities and a degree of psychological continuity. This is supposed to make it clearer why a person could not become an animal (or a brain) With no capacity for thought. I do not understand their suggestion. Either the 'functioning' organism is identical with the 'non-functioning' organism that results in the 'oblivion' story, or it is not. If so, then I can persist without psychological continuity (though I may cease to be a person or a 'function- ing' animal), contrary to the Psychological Approach. If not, then biological continuity is not sufficient for an animal to persist, and their suggestion is of no help at all.

' Why not the entire brain? Transplanting the cerebrum alone gives the psychological 'transfer' effect we want, but leaves intact the autonomic nervous system, based chiefly in the brainstem, which coordinates one's vital functions.

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organism than a freshly severed arm is an organism. It is then implanted into the empty cranial cavity of another living human animal, at which point it becomes an organism once more by assimilating the vital functions of its 'host ' . The animal that receives my cortex presumably ceases to exist at this point, even though its autonomic nervous sys- tem continues to work without interruption. So their version of the story calls for at least three human animals: one (me) which has my memories throughout and is not an organ- ism at all during part of the operation; a second, which apparently comes into being when my cerebrum is separated from the rest of me; and a third, which perishes (or at least ceases to be an animal) when I, a naked cerebrum, am implanted into it?

This is a very unnatural way to describe our two cases. Quite aside from what hap- pens to me, the facts about biological continuity at least strongly suggest that in the 'ob l iv ion ' case there is just one animal, which can remember things when the story begins and can no longer do so when the curtain fails. (Or, if people are not animals, one animal is first associated with a remembering person and afterwards is associated with no such person.) And in the ' transplant ' case the physiological facts suggest that there are just two human animals, not three (or four), and that a cerebrum is simply transplant- ed from one to the other, much as a kidney might be.

For these reasons I shall assume that narrowly biological (non-psychological) criteria are both necessary and sufficient for the persistence of human organisms: Thus their criterion of identity is not the one specified by the Psychological Approach, and if that Approach is true, you and I are (apparently) not animals.

But if we are not human organisms, what sort of beings are we? And how are we related to 'our ' human organisms? I will consider five ways in which friends of the Psychological Approach might try to answer these questions.

A n s w e r One You and I are not material objects. Perhaps, as Descartes thought, we are immaterial substances whose essence is thinking. If so, the way in which people and human organ- isms are related is a chestnut. It is interesting that few, if any, Cartesians have accepted the Psychological Approach : Locke (a borderline case of a Cartesian) seemed to believe

5 In fact the story requires a fourth human animal: there must have been a human being whose cerebrum was removed from his skull to make room for mine to be transplanted. That organism must have either ceased to exist, or become a naked cerebrum, depending on what the surgeons did with his brain when they removed it. Of course that organism cannot be identical with the animal into whose skull my cerebrum is transplanted, on the current proposal, for there is no psychological continuity linking them. There is a further reason for my view. The existence of fetuses (in particular, human fetuses less than about six months old, which, embryologists tell us, are not yet capable of thought), anen- cephalics, and coma patients (not to mention the brainless human organisms in the 'transplant' case) shows that psychological continuity cannot be necessary for the persistence of just any human organism, since those human beings manage to persist without it. So if psychological continuity is somehow relevant to our identity, then either different human organisms fall under different criteria of identity, or (more plausibly, if we were once fetuses or could become termi- nally comatose) the human criterion of identity is a complex disjunction of psychological and biological components - - a sort of 'best-candidate' theory. As far as I know, no philosopher has yet proposed a version of the Psychological Approach that can accommodate these cases.

7 Leibniz may be an exception. Noonan reads Leibniz as saying that psychological continuity is both necessary and sufficient for the persistence of those immaterial, individual substances (monads) that are people (op. cir., pp.62f).

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that immaterial, thinking substances (if the things that think are immaterial) could sur- vive radical psychological discontinuity, and he notoriously denied that they were peo- ple. Modern-day dualists, such as Chisholm and Swinburne, tell us that our persistence is logically independent of psychological or causal facts, and is unanalysable or sui generis2

Alternatively, a person may be neither a material nor an immaterial substance, but some sort of complex psychological event or property-instance, the subject of which is a human organism. A person is something that 'happens to ' an organism, or a way that an organism is. Roughly speaking, you and I are minds: our thoughts are not states that we are in, but rather we are composed or constituted of thoughts. Insofar as a single, partic- ular event can happen first to one substance and then to another (or insofar as a particular property-instance can be had first by one substance and then by another) a person and ' i ts ' organism can go their separate ways. 9

But consider the living organism of which my thoughts, on this view, are states. Is it not a conscious, thinking being as well? If so, how can I be certain that I am not the organism rather than the person? Probably anyone who holds this view will say that the organism does not think: to ascribe a thought to a person is to say that the thought is a part or constituent of that person, and not a state of him. Thus, no organism or brain or substance of any other kind can be said, strictly and literally, to be the subject of any psychological state whatever. I doubt that many friends of the Psychological Approach are willing to accept this highly implausible view.

Answer Two You and I are material objects coincident with human organisms. Each of us occupies the very same region of space as some organism. Nevertheless, none of us is identical with any organism, since people and organisms fall under different principles of individ- uation. If my cerebral cortex is transplanted, I shall come to coincide with a different organism from the one with which I now share my space and my matter. Should the lat- ter organism acquire a new cerebrum, it would become coincident with someone else? °

The philosopher who gives this answer is forced to deny a number of very attractive principles. For example, she must give up the widely held principle that objects cannot

Roderick Chisholm, Person and Object (La Salle, IL: Open Court, 1976) pp.108-113; Richard Swinbume in Shoemaker and Swinburne, op. cir. This seems to be Ouinton's position. It may also be Parfit's view. At any rate, Noonan reads Parfit as saying that 'All there are in reality are bundles of experiences (or "perceptions") linked together by certain relations of psychological continuity and connectedness (and causally related to happenings in brains and bodies),' which I take to mean that we are literally made up of psy- chological events (op. cit., p.121). David Wiggins defended this view in Identity and Spatio-Temporal Continuity:

[T]he principle of individaation for human body [i.e. human organism] is not quite the same as that for a person . . . . we have two things, a person and a human body, occupying.. , the same matter, and normally occupying it concurrently for the period of the life of the person. We then have two non-identical things in the same place at the same time. But this is not really a problem, because it will be found that room was carefully left for this in our refor- mulation of the principle that two things cannot be in the same place at the same time. We stipulated: two things of the same kind. [pp.48f]

See also John Pollock, How to Build a Person: A Prolegomenon (Cambridge, MA: MIT Press, 1989) pp.32-37.

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mereologically compose more than one object at once - - that is, she must admit that two or more objects can have exactly the same proper parts at the same time." For on the present proposal, each person and her coincident organism, though numerically distinct, have the very same proper parts. If this were not so, the person and the organism togeth- er would weigh more than either weighs separately. If I weighed 150 pounds and the organism coincident with me weighed the same, but was composed of wholly different atoms from the ones that composed me, our combined weight would be 300 pounds. Happily, this is not how it is with people and human organisms.

Answer Two also entails that being a person and being a living organism are not intrinsic properties. My coincident organism and I are composed of the same matter arranged in the same way; we are in fact perfect duplicates of one another. Yet I am no organism and it i s no person. That organism is an organism, rather than a person, not because it lacks any psychological features, but merely because it has the modal property of possibly surviving obl ivion (i.e., radical psychological discontinuity). And even though I am biologically indistinguishable from an animal - - even though I am alive - - I am not an organism, but a person instead, simply because I could not survive oblivion. 1~

A further problem facing Answer Two is this: jt entails that you and I have no ade- quate reason to think that we are people. If the organism coincident with me shares all of my intrinsic properties, then presumably it can think of and refer to itself if I can think of and refer to myself. (How could it be unable to think and talk merely because it differs from me in its modal properties?) So that organism falsely believes itself to be a person. But why think that I am not making the same mistake? There would seem to be an even chance that I am the organism and not the person (and that my criterion of identity is the animal one rather than the personal one). And no acceptable theory of personal identity could have the consequence that, for all we know, you and I might not be people.

Answer Three You and I do not really exist. Thus there are no philosophical problems about what ontological category people fall under, or about how they are related to ' their ' human organisms, for when we appear to be talking about people we are in fact talking about something else. 13 Presumably those who hold this view do not believe that sentences like 'Some people have denied their own existence' are always and everywhere false - - or at least not false in the way that 'Some pixies have denied their own existence' is false. Their view is rather that sentences that appear to entail that there are people, can be made true (or at least appropriate in some sense) by something other than people. Their posi- tion is much like that of the nominalist, who claims that sentences such as ' there are

~1 Any objects (call them the xs) compose an object y if and only if each of the xs is a part of y and every part of y shares a part with one of the xs. In this definition an object is assumed to be a part of itself; aproper part of an object is a part of it that is mtmerically distinct from it.

~2 This also entails that things can differ in their modal properties without differing in their non- modal properties, a principle that many philosophers deny - - e.g. Mark Heller, The Ontology of Physical Objects (Cambridge: Cambridge University Press, 1990) p. 31.

~3 Famous philosophers who have denied the existence of people include Spinoza, Hume, and Russell. More recently this view has been defended by Jim Stone, 'Pat-fit and the Buddha: Why There Are No People,' Philosophy and Phenomenological Research 48 (1988) pp.519-532; and Peter Unger, 'I Do Not Exist' in Graham Macdonald (ed.), Perception and Identity (Ithaca: Cornell University Press, 1979).

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many properties that spiders share with insects' , can be true even though there are no abstract objects. The proponent of Answer Three, like the nominalist, must show how this is possible.

The accepted way of fulfilling this obligation is to show how the problematic sen- tences can be paraphrased into others that in some sense 'say the same thing' as those sentences, but which do not appear to entail that there are people. This task will be far easier if one accepts the existence of human organisms, for they have many of the prop- erties that figure in the problematic sentences. In that case, sentences that appear to say that there are persisting people can be paraphrased into sentences about human organ- isms standing in whatever relation the Psychological Approach says that personal identi- ty consists in. Suppose we say that, for any person x who exists now and any person y who existed at some time in the past, x--y if and only i f x now stands in R to y, where R is some complex relation involving psychological continuity. Then we could give a cum- bersome but s traightforward paraphrase of the sentence ' I spoke to my mother last week':

There are human organisms v, w, x, y, and z such that v is the present speaker and v now stands in R to w and x is the mother of y and v now stands in R to y and z stood last week in R to x and w spoke to z last week.

What makes the Psychological Approach true and its rivals false, on this view, is that such paraphrases of 'person-talk' come out true only if they involve a psychological rela- tion such as R.

Now this view has an air of paradox. Human animals are ideally suited to 'stand in' for people because they have many of the properties that people would have, if there were any people: they are intelligent and self-conscious; they incur moral responsibili- ty; they communicate with one another by speaking English; etc. But as long as there are things like that, how can anyone claim that there are no people? Apparently, what prevents those organisms from being people is that they have the wrong criterion of iden- tity: nothing that is individuated by a relation other than R could be a person. (That 's what the Psychological Approach says.) But surely it is more likely that you and I are those human organisms than that we don' t exist at all! I'

To avoid this paradox, the proponent of Answer Three must deny that there are human organisms, or anything else that is intrinsically suited to be a person. This amounts to rejecting any ontology that includes such familiar material objects as trees and tables and trout, for it would be arbitrary to accept those things but reject human ani- mals. Anyone who takes this approach faces the daunting task of explaining how our ordinary statements that appear to be about people can be true (or appropriate) even though there are no human organisms. (Not to mention how our ordinary statements that

Perhaps some philosophers who say that there are no people do not mean by this that there are no such beings as you and !, but simply that neither you nor I nor anyone else is a person. This view is not a version of Answer Three. (I find it a far less interesting view than Answer Three.) My concern in this essay is the criterion of identity for beings like you and me. I happen to believe that you and I, if we really exist, are obviously people, since the meaning of 'person' is closely bound up with the personal pronouns. But ff someone wants to claim that none of us intelligent human beings is a person, we disagree only about the meaning of a word.

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179 Is Psychology Relevant to Personal Identity?

appear to be about tables and trout can be true although there are no such things.) And even if this can be accomplished, it is a bold philosopher indeed who would sooner deny her own existence than give up the Psychological Approach.

Answer Four You and I are organisms; but we may not always be the same organisms. Imagine that my cerebrum will be transplanted tonight. Then I am the same person as the man who will have my cerebrum tomorrow, but not the same organism; and I am the same organ- ism as the man who will have an empty cranium tomorrow, but not the same person. The re la t ion same person, on this v iew, sa t i s f ies the cr i ter ion laid down by the Psychological Approach: I shall be the same person as the man who has my cerebrum tomorrow because he and he alone will then be psychologically continuous with me as I am now. The relation same organism, on the other hand, has different criteria of satis- faction: I am the same organism as the man who will have an empty cranium tomorrow because he and I are connected in some narrowly biological way. Although I am now the same person as ' this ' human organism (the one I am now most intimately connected with), tonight that animal and I shall go our separate ways, for the man who gets my cerebrum will be neither the same person nor the same organism as the man with the empty cranium. Tomorrow I shall be the same person as a different human organism, one that is presumably waiting today with an empty cranium.

On this view, the predicates ' is the same person as ' and ' is the same organism as' do not express 'classical ' or 'absolute ' identity, for that relation entails absolute indiscerni- bility. I cannot be absolutely identical with the man who gets my cerebral cortex, for I am now the same organism as myself but not the same organism as he; nor can I be absolutely identical with the man who will have an empty cranium, for I am the same person as myself but not the same person as he. So I am not absolutely identical with anyone who exists after the operation. Since the Psychological Approach entails that in some important sense I survive the operation, it cannot be a theory about absolute identity.

In fact the present proposal is coherent (and different from previous answers) only if there is no such relation as absolute identity. If there were, I should be either absolutely identical with ' this ' human organism or absolutely distinct from it. If we are identical, whatever is true of me is true of that organism; so I have a cerebral cortex tomorrow only if that organism has a cerebral cortex tomorrow, contrary to our hypothesis. If this organism and I are absolutely distinct, then two distinct material objects now occupy the same place and share the same matter, a view that we have already discussed.

If there is no such relation as absolute identity, then the unqualified predicates ' is identical wi th ' and 'is distinct from' are semantically incomplete, like the predicate ' is to the left of'. We can ask whether Ohio is to the left of New York on a standard map looked at right-side-up; but it is meaningless to ask whether Ohio is to the left of New York simpliciter, for there is no such relation as being absolutely to the left of. The pre- sent proposal says that we can ask whether Ohio and New York are the same state or the same land-mass; but it is meaningless to ask whether they are identical or distinct sim- pliciter, for there is no such relation as being absolutely identical or distinct. (Moreover, if there is no absolute identity, there is no absolute cardinality: we cannot simply ask

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whether Ohio and New York are two. We can ask only whether they are two states, two land-masses, or two of some other kind.)

As far as I can see, Answer Four can be worked out consistently, and it avoids many of the difficulties the other answers face. But relative identity is highly controversial, and I doubt that many friends of the Psychological Approach will cheerfully accept it. It faces problems regarding reference and de re modality. '5 Nor is it clear that we can real- ly understand the view that there is no absolute identity, particularly s ince our under- standing o f identity seems so closely bound up with Leibniz ' s Law (i.e., the indiscerni- bility of identicals). 16

N o w there are circumstances that may make it useful or appropriate to say that the same human animal can be different people at different times. We may say, for example, that Jones is no longer the person he was before he had his stroke, or before his conver- sio.n to Zen Buddhism. This may appear to support Answer Four. But it is clear that we can account for this without rejecting absolute identity. Jones ' psychological transforma- tion does not compel us to deny that he and his survivor are strictly, numerically identi- cal; indeed, our use of the name ' Jones ' (or the pronoun ' h e ' ) to denote both the man who lost his mind and the survivor implies that they are identical. The simplest way to understand this purely psychological or legal sense o f personal identity is to say that 'be ing a particular person ' is a property that a human animal (or anything else capable of being a person) may have for a while and then cease to have. If an animal is Jones at one time and Smith later on, we say that Jones is the same person as Smith just in case the animal ' s psychological states at the, two t imes in question are appropriately related. But either way, ' Jones ' and 'Smi th ' denote the same human organism. 17

A n s w e r Five People, organisms, and other material objects do not strictly persist, but are temporally extended, ' four-dimensional ' objects. A material object, on this view, is s tretched out in

15 For a discussion of relative identity and reference, see Peter van Inwagen, 'And Yet There Are not Three Gods but One God' in Thomas Morris (ed.), Philosophy and the Christian Faith (Notre Dame: University of Notre Dame Press, 1988).

De re modality comes in in the following way. On standard theories of modality, to say that I might have been six feet tall is to say that there is a possible world such that, if that world had been the actual world, I myself should have been six feet tall. Here the reference of ' r in other worlds is understood in terms of classical identity. But on Answer Four, I am both a person and an organism; and it is possible for an organism to survive oblivion but not possible for a person to survive it. So what does it mean to say that I could (or could not) survive oblivion? Here is a possible solution: qua organism, I could survive oblivion, because there is a possible world in which a being that is the same organism as I am survives oblivion; but qua person, I could not survive oblivion, for there is no world in which someone who is the same person as I am sur- vives oblivion. This view is very like counterpart theory with multiple counterpart relations (see below), for it entails that modal predicates such as 'could survive oblivion' are ambiguous in the same way as the 'is ' of identity is ambiguous: it expresses a different modal property for every relative-identity relation. Which modal property is intended on a given occasion of utterance (why 'I could survive oblivion' is false rather than true) is presumably determined by the con- text.

16 The classic discussion of this matter is Wiggins' Identity and Spatio-Temporal Continuity, see esp. pp.l-5.

17 This view is not a version of the Psychological Approach, since it entails that you and I are human organisms and that our strict, numerical persistence is the persistenc e of a human organ- ism, and so does not consist in psychological continuity. I persist if and only if this human ani- mal persists, although I may later be a different person, or not a person at all.

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time much as a road is stretched out in space; like an event, it fills an interval of time, and is composed of earlier and later temporal parts. Facts about what properties I have at a given time are facts about the properties of the temporal part of me that 'occurs ' then: for me to be hungry now is for me to have a hungry part that 'occurs ' now (just as for Water Street to be narrow at the town line is for it to have a narrow part that lies at the town line). Thus my identity through time is not the existence of a single object at dif- ferent times, but consists in the fact that many distinct 'person-stages' that occur at dif- f e ren t t imes are p a r t s of a s ing le , f o u r - d i m e n s i o n a l pe rson . A c c o r d i n g to the Psychological Approach, person-stages will be parts of the same person just in case they stand in some psychological relation. Thus a person is, roughly, a mereological sum of psychologically interrelated person-stages. TM

On this view, human people and human animals are related in a rather complex way. Ordinarily the temporal parts or ' s tages ' of a person will also be stages of a human organism? 9 But the stages of a person may not all be stages of the same organism. If my cerebrum is transplanted tonight, the stages of me that occur tomorrow - - the ones that can remember what happens to my present stages - - will not be parts of the human organism that my present stages are parts of, for tomorrow's stages of that organism have an empty cranium and cannot remember anything. This organism and I shall have gone our separate ways, much as two roads may diverge after overlapping (sharing their parts) over a portion of their length.

Like most philosophers, the friends of temporal parts typically accept the principle that objects cannot have more than one mereological sum at once: no two objects can have exactly the same proper parts at the same time. Attractive as this principle is, it complicates the account of people, for it entails that this human organism and I are numerical ly identical if we share all of our proper parts. Thus most people presumably are organisms: if I never suffer oblivion or have my cerebral cortex transplanted, my c a r e e r m a y o v e r l a p e x a c t l y w i t h t ha t o f th i s h u m a n an ima l . 2° H o w e v e r , the Psychological Approach seems to entail that people and human organisms (or people and

~8 This is the view favoured by Lewis, and more recently by Noonan. An object x is a mereological sum or fusion of certain objects (call them the ys) just in case

the ys compose x - - that is, just in case each of the ys is a part of x and every part of x shares a part with one of the ys.

19 If 'person' must be defined as an aggregate of appropriately related 'person-stages', the four- dimensionalist owes us an account of 'person-stages' that says more than simply that they are more or less momentary, 'temporal cross-sections' of people. Lewis assumes without argument that 'person-stages' are stages of human organisms, and this is clearly the natural thing to say. But if there are such things as upper halves of human animals (or of human-animal-stages), and mereological sums of people (person-stages) and their clothes, as the standard four-dimensional- ist ontology implies, we seem to be left without any reason to deny that those things are people, or person-stages. (Since they have working brains and speaking apparatus as parts, they seem to be able to think and speak.) But I won't press this difficult point. Lewis considers this a virtue of his view of personal identity. See 'Counterparts of Persons and their Bodies' reprinted in Philosophical Papers, Vol. I (New York: Oxford University Press, 1983).

It may be that our careers do not quite coincide exactly. The Psychological Approach appar- ently entails that I am essentially capable of entering into that psychological relation th/tt figures in the individuation of people. If so, 1 was never a four-month-old fetus, since (embryologists tell us) a foetus is not capable of thought or sensation at that stage in its development. So, according to the Psychological Approach, I probably began to exist several months after this organism did. (I hope to explore this issue in another paper.) But then I am identical with a proper temporal part of that organism, and the point is the same.

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proper parts of human organisms) necessarily differ in their modal properties: organ- isms, but not people, for example, can survive oblivion. How can a person and an organ- ism be strictly numerically identical, yet have different modal properties?

The four-dimensionalist must say that the modal difference is only apparent. She can save appearances by adopting a sophisticated version of counterpart theory? J Ordinary counterpart theory says that a sentence like 'You might have been an astronaut' is true just in case there is a possible world in which there is a counterpart of you that is an astronaut. A counterpart of you in a world is something that resembles you in certain ways specified by the context of the modal sentence. Since any two things are similar in some respects, different contexts invite us to construe our modal claims in terms of dif- ferent counterpart relations. This provides a way out of the present difficulty: when we say that an organism (which may also be a person) could survive oblivion, we are saying that some possible world contains an organic counterpart of that organism (something that resembles it in biological respects) that survives oblivion. When we say that a per- son (who may also be an organism) could not survive oblivion, we are saying that no possible world contains a personal counterpart of her (something that resembles her in 'personal' respects) that survives oblivion. Thus, if some of my organic counterparts are not my personal counterparts, it may be possible for me, qua organism, to survive obliv- ion, even though this is impossible for me qua person. (For example, imagine a world in which a personal counterpart of me, Tim, drinks from the waters of Lethe. The human animal who survives this, Tom, may be an organic counterpart of me, since he resembles me very closely in biological respects. That would make it the case that qua animal I could survive oblivion. But Tom is not my personal counterpart, since his mental life is so very different from mine during the latter part of its life. In fact, according to Lewis, Tom is not a person at all. Tim, of course, ceased to exist when he drank of Lethe. He consists of the temporal parts of Tom that 'occurred' before that fateful moment.)

Of course, counterpart theory with multiple counterpart relations entails that there is no such property as possibly surviving oblivion, since the predicate 'possibly survives oblivion' is ambiguous until a counterpart relation is specified - - much as the unquali- fied predicates 'are identical' and 'are distinct' are ambiguous according to the relative- identity theorist. Perhaps this amounts to rejecting de re modality. (One might describe the relative identity thesis as a rejection of identity.) But friends of counterpart theory typically do not see this as a disadvantage; they believe that their theory captures the sense of our modal discourse better than any other.

Among those few proponents of the Psychological Approach who have tried to say anything about how human people retate to human organisms, Answer Five has proved the most popular. Its popularity may be well deserved, for the ontology of temporal parts has great philosophical utility quite aside from its applications to personal identity.

Answer Five is not without its problems, however. Some philosophers find incoher- ent the very idea that a material object could be temporally extended. 22 (We understand

This is the solution Lewis prOposes in 'Counterparts of Persons and their Bodies'. See, for example, P. T. Geach, 'Some Problems about Time' reprinted in his Logic Matters (Berkeley: University of California Press, 1972) pp.302-317; P.M.S. Hacker, 'Events and Objects in Space and Time', Mind 91 (1982) pp.l-19; Judith Jarvis Thomson, 'Parthood and Identity Across Time', The Journal of Philosophy 80 (1983) pp. 201-220; Peter van Inwagen, 'Four-Dimensional Objects', Norms 24 (1990) pp.245-255.

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what it is for a baseball game, say, to fill the interval between noon and two p.m, and to consist of an earlier half and a later one; but how could a concrete material object - - you, for example - - literally fill an interval of time, and have as parts an earlier half and a later one?)

But these matters are not well understood, and I will focus instead on a different problem. Most of the theoretical advantages of the temporal-parts ontology require us to endorse the principle that every matter-filled spacetime region contains its own material object. This principle entails that there are many more people than we would otherwise have thought. Suppose for the sake of argument that you occupy the precise spacetime region S. There are many matter-filled regions distinct from S yet indistinguishable from it by any practical means: regions that include a quark not in S or exclude an electron that S includes, for example, and regions some fraction of a second longer or shorter.than S. If each of these regions has its own object, each contains a person - - or at any rate a thinking, conscious being - - numerically distinct from you. So whenever you try to refer to yourself, many other beings (infinitely many, if time is infinitely divisible) simultaneously try to refer to themselves. What linguistic convention enables you, by saying ' I ' , to pick out just one of them, and the same one each time? Perhaps each ordi- nary utterance of a personal pronoun in fact refers ambiguously to all of the appropriate 'candidates'. But if no unambiguous, singular reference to people is possible, then, strictly speaking, there cannot be such a person as you or I.

The four-dimensionalist may reply that this systematic ambiguity of personal refer- ence is really quite harmless, for anything we might ordinarily say of you will be true of all of the beings we ambiguously pick out when we try to refer to you. If we say, in the appropriate circumstances, that you are six feet tall, that you expect rain, or that you exist, what we say really is true, for all the beings that the pronoun 'you' ambiguously denotes are six feet tall, expect rain, and exist. So this view, radical though it is, does not contradict any of our ordinary beliefs or statements about people. ~

But many things that we ordinarily and truly say about you are not true of all the 'candidates' we ambiguously denote. Suppose you say, truly, that you were alive in 1980, and that you will take a bath tomorrow. Now the present stage of you that makes this utterance is a part of many beings that did not exist in 1980, and a part of many more that will not exist tomorrow. Some of the beings that include your present stage began to exist just ten years ago, and countless others will cease to exist between now and tomor- row. What prevents your utterance of ' I ' from referring to them? (They are not people, you may say, because they are proper parts of people. But people or not, how could this merely relational property prevent them from referring to themselves?) If every refer- ence to you denotes ambiguously all of the 'candidates' for being you, your statement that you were alive in 1980 is neither true nor false, since some of those 'candidates' were alive in 1980 and others were not.

Perhaps this problem would not arise if the use of our demonstrative ' I ' (and other personal pronouns) were tied to the concept person (qua maximal aggregate of psycho- logically connected person-stages). If this is so, our ' I ' does not refer to non-maximal aggregates, however articulate and intelligent they may be. But what justifies our confi-

z~ This is Lewis' view; see 'Survival and Identity', pp. 64f.

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dent belief that we are the maximal aggregates, rather than the non-maximal ones? If the latter falsely believe themselves to be maximal, couldn't we be making the same mis- take?

I have no doubt that devoted friends of temporal parts could devise an even more ingenious hypothesis about the semantics of personal reference, according to which their theory does not conflict with our ordinary beliefs or undermine their justification. But four-dimensionalism is sometimes thought to provide a simple and elegant solution to ontological problems about people. This is clearly not the case. At least one philosopher has claimed that an ontology according to which there are, strictly speaking, no compos- ite, inanimate objects such as tables and chairs is 'literally incredible', even if it can be shown that this does not conflict with any ordinary, non-philosophical beliefs?' Anyone of this opinion should reject for the same reason an ontology according to which there are, strictly speaking, an infinite number of people wherever we say, in ordinary lan- guage, that there is one.

The four-dimensionalist might try to avoid these difficulties by giving up the princi- ple that every matter-filled spacetime region contains an object. She would thereby for- feit all of the general advantages of an ontology of temporal parts for the sole purpose of accommodating the Psychological Approach to personal identity. But while this move would presumably reduce the number of candidates for the reference of ' I ' as I utter it, what guarantees that the number of candidates is one? And what guarantees that the 'right' candidate 'wins ' - - that the sole candidate for the reference of ' I ' has the proper- ties that I have, and did not begin, to exist just five minutes ago? If some matter-filled spacetime regions don't contain an object, which ones do, and which ones don't? Until she can at least begin to answer these questions, the four-dimensionalist has not explained how people and human organisms are related.

I believe that anyone who accepts the Psychological Approach is committed to one of these five accounts of the ontological status of human people and their relation to human organisms. There may of course be other accounts consistent with the Psychological Approach that have not occurred to me, or whose merits I have overlooked. But these five seem to me to be the only serious candidates. The Psychological Approach entails that one of these accounts, or some other that I have not considered, is true.

Fortunately, we can avoid choosing between these five answers and the ontological difficulties they incur. We need only give up the Psychological Approach and accept instead a quite unsophisticated, perhaps even simple-minded, v iew of ourselves. Suppose that you and I are, in a straightforward sense, human animals: each of us is numerically identical with a member of the species H o m o sapiens. Our persistence through time does not consist in psychological continuity, or in any relation involving psychology; rather the narrowly biological criterion of identity that applies to other ani- mals is true of us as well. 25

This is how Unger (having repented of his former ways) appraises van Inwagen's ontology at p.123 fn. of Identity, Consciousness and Value. More precisely, narrowly biological continuity is both necessary and sufficient for the persis- tence of a (human) person. If cerebrum transplants are absolutely impossible perhaps there can- not be psychological continuity without biological continuity, and psychology is not entirely irrelevant to our persistence. This seems to be Wiggins' view in Sameness and Substance (Cambridge, MA: Harvard University Press, 1980).

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Here we have a far simpler and more attractive view of the ontological status of human people, and of their relation to human organisms, than any- account that is consis- tent with the Psychological Approach. What may surprise us about this proposal is that psychological considerations turn out to be completely irrelevant to our persistence, except in the derivative sense that in most actual cases psychological continuity accom- panies biological continuity. (Radical psychological discontinuity is almost always accompanied by the death of the organism, and vice versa.) Thus psychological continu- ity is merely excellent but fallible evidence for personal identity. Only by accepting a theory of personal identity based on biology alone, with no psychological ingredient at all, can we avoid the choice between answers One through Five. 26 For the persistence of a human animal has nothing to do with psychology.

Of course, this means that many philosophers' reactions to the famous science-fiction stories I have discussed are mistaken. Someone who loses all of her memories or even her capacity for thought and consciousness does not thereby cease to exist, on this view, although she may cease to be a person and her existence may lose all value to her. (She may even become a 'different' person in the legal or psychological sense that we should no longer attribute to her the individual rights and .responsibilities that accrued to her before she lost her memories.) No relation involving psychological continuity is neces- sary for our persistence.

Nor can a person be 'transplanted' from one human organism to another. If my cere- brum is transplanted into another head, I simply lose the capacity for thought and con- sciousness, while someone else - - a numerically different being - - comes to enjoy my (apparent) memories, my personality, my political opinions, and the rest of my psycho- logical features. (Whether that person deserves to be treated in some or in all respects as if he were me is of course a further question.) But I no more 'go along with' my trans- planted cerebrum than I should 'go along with' my liver if it were removed from my abdomen - - even i f that cerebrum continues to support consciousness throughout the operation. I could survive the loss of my cerebrum, together with my capacity for thought and consciousness, in the same way that I could survive the loss of my liver, along with my capacity to purify my blood. Either of these losses may eventually cause my death. But neither logically necessitates my demise. Surprising as this may be to philosophers steeped in the recent literature on personal identity, I believe that these are

A view of this sort is proposed by van Inwagen in Material Beings (Ithaca: Cornell University Press, 1990) §§14-16. Michael Ayers also defends this view in Locke (London: Routledge, 1990) Vol.lI, pp.290ff.

One might think that we could avoid choosing among answers One to Five by accepting another rival to the Psychological Approach, namely the view that there is no informative crite- rion of personal identity at all, but that this relation is unanalysable or sui generis (i.e. that there are no non-trivial or observable necessary and sufficient conditions for our persistence). But unless the identity of human animals (and presumably of our evolutionary cousins as well) is also unanalysable, and does not, as we might have thought, consist in a relation of biological continuity, this view also has the consequence that you and I are numerically distinct f~om 'our' human organisms. And defenders of this 'Simple View' of personal identity, as it is often called, typically claim that it does not apply to material objects across the board, but only to peo- ple. Thus they also owe us an account of the ontological status of people, and of their relation to human organisms. Most actual proponents of the Simple View seem to be Cartesian dualists, and so accept a version of my Answer One. See, for example, Richard Swinburne, 'Personal Identity', Proceedings of the Aristotelian Society 74 (1973-74) pp.231-248, and Personal Identity, op. cit.

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simply facts that we must live with. I am not denying the importance of thought in ontology and other areas of philoso-

phy. Our psychological capacities are remarkable, and make us unique among terrestrial beings; moreover they give our lives meaning and make us people. Nor do I deny that psychological continuity plays an important role in determining our attitudes towards the past and future. I deny only that our psychological features have anything to do with the conditions under which we persist. I deny that the importance of thought and psycholog- ical continuity is sufficient reason to conclude that we are beings whose essence is think- ing, or psychological continuity.

Given that we are material beings, we are intrinsically much more like chimpanzees, horses, or even oysters, than we are like non-biological thinking beings such as gods, angels, and intelligent machines made of wire and silicon (if there could be such thinking things). And we should expect an object's criterion of identity to bear some interesting relation to its intrinsic nature. If we suppose that we have our criterion of identity in common with gods, angels, or electronic thinking machines, rather than with chim- panzees, horses, and oysters, it seems to me that we are pretending to be something that we are not, and refusing to accept our place as biological beings in the natural world. This refusal has a long and fascinating history, and I should not know how to defend my conviction that i t is a delusion (and a rather arrogant one at that). But friends of the Psychological Approach should know that they are in an important sense placing them- selves above nature? 7

415 Greenwood Place Syracuse N Y 13210

Received February 1993 Revised May 1993

z7 I am grateful to Jos6 Benardete, Jonathan Bennett, Sam Levey, Peter van Inwagen, and several anonymous referees for their comments on earlier versions of this paper.

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