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Personal Identity and Brain Transplants

Published online by Cambridge University Press:  08 January 2010


My topic is personal identity, or rather, our identity. There is general, but not, of course, unanimous, agreement that it is wrong to give an account of what is involved in, and essential to, our persistence over time which requires the existence of immaterial entities, but, it seems to me, there is no consensus about how, within, what might be called this naturalistic framework, we should best procede. This lack of consensus, no doubt, reflects the difficulty, which must strike anyone who has considered the issue, of achieving, just in one's own thinking, a reflective equilibrium. The theory of personal identity, I feel, provides a curious contrast. On the one side, it seems highly important to know what sort of thing we are, but, on the other, it is hard to find any answer which has a ‘solid’ feel.

Copyright © The Royal Institute of Philosophy and the contributors 1991

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1 I have addressed these issues in ‘Persons, Animals and Ourselves’, in Gill, Christopher (ed.), The Person and the Human Mind (Oxford: Clarendon Press, 1990), 83107Google Scholar, and in ‘Against Personal Identity’ (unpublished). Other, and important, discussions are: Wiggins, D.Sameness and Substance (Oxford: Blackwell, 1980), esp. Ch 6Google Scholar, and Wiggins, D. ‘The Person as Object of Science, as Subject of Experience, and as Locus of Value’, in Peacocke, A. and Gillett, G. (eds). Persons and Personality, pp. 5674, 208–12 (Oxford: Blackwell, 1987).Google Scholar

2 I shall, from time to time, refer to this argument as BTA (short for Brain Transplant Argument).

3 There is a clarification and a hesitation I wish to express. First, I am not claiming that BTA is the strongest objection to animalism. I am, at the moment, unsure what qualifies as that. Second, since animalism has not been explicitly opposed in standard discussions, there is something misleading in saying that BTA has been the dominant argument against it. What seems fair to say though, is that BTA has been, in recent discussions, the leading objection to the standard bodily criterion approach to personal identity, which is the view amongst the standard views which is closest to animalism.

4 Parfit, Derek, Reasons and Persons (Oxford: Clarendon Press, 1984).Google Scholar

5 Wilkes, Kathleen V., Real People (Clarendon Press: Oxford, 1988)Google Scholar; see esp. Ch. 1. The book is subtitled ‘Personal Identity without Thought Experiments’.

6 Johnston, Mark, ‘Human Beings’, The Journal of Philosophy LXXXIV, No. 2 (02 1987), 5983.CrossRefGoogle Scholar

7 The brain performs important control functions for the rest of the body. In the brain transplant cases as normally envisaged by philosophers these control functions are not necessarily resumed in the new system. We might call these the brain's extrinsic functions. The intrinsic functions are the processes which characteristically occur in the brain, constituting whatever they constitute (assumed to be the sustaining of a mentally endowed subject). I hope that this note explains the significance of ‘intrinsic’ as it occurs in the discussion.

8 I hope that this stipulation makes explicit a feature which is, in fact, characteristic of standard presentations of this sort of argument. It also distinguishes BTA from a similar argument presented by Johnston (ibid. 77–80), which I hope to discuss elsewhere.

9 Williams, Bernard, ‘Personal Identity and Individuation’, in Problems of the Self (Cambridge: Cambridge University Press, 1973), 1112CrossRefGoogle Scholar. It should be pointed out that Williams was not discussing brain transplants, but, rather, the general idea of a distinctive personality, which is linked at t to body B, shifting to body C at t+n. Williams suggests that it might be a logical impossibility that body C express that personality: ‘The emperor's body might include the sort of face that just could not express the peasant's morose suspiciousness … These “could”s are not just empirical—such expressions on these features might be unthinkable’ (Williams, ibid. 12). These remarks do not pay enough attention to the crucial issue, and give prominence to a peripheral one. Suppose that we grant the possibility of a logical impossibility of the sort Williams is arguing for, then, as it stands, it amounts only to a point about the expressibility of a personality (or attitude) in a given body. It does not follow that the attitude or personality might not belong to the person with that body. Williams requires that presence involves expressibility; but he gives no reason for saying that. Whether that is so is the crucial issue. Further, if we decide that presence does require expressibility, then it will follow that, if a certain body cannot in fact express a certain attitude, then the person with the body cannot, in fact, have that attitude. This conclusion does not require that it is a logical impossibility for that body to express it.

10 The success assumption also provides a counter to another criticism of this stage in the transplant argument (which I owe to L. J. Cohen.) It might be said that acceptance of the intuition that the resulting subject is the same person as the person who donated the brain rests on the quite general principle that a person is tied to his living brain. This general principle, it might be alleged, is not plausible, since in some circumstances, it gives counter-intuitive results. An example would be that of a child born with severe brain disease, who is given a new brain straight after birth; it is claimed, we would treat that as the child receiving a new brain, and not as the creation of a different person. A proponent of the transplant argument would reply that there is no essential commitment to the general principle in endorsing the intuition about the successful case. This sort of example, and also less-than-successful cases, are, however, certainly relevant when considering the general account of identity which someone who accepts the brain transplant argument would go on to develop.

11 I do not mean to imply that the notion of metaphysical possibility is free of all doubts and difficulties. I think of myself as merely endorsing the conventional approach.

12 I was lead to think that this reply was worth investigating partly because it amounts to saying about whole brain transplants what, it seemed to me, David Wiggins had suggested, in Sameness and Substance, should be said about fision and fusion (see Sameness and Substance, 169–70 and 221)Google Scholar. Thus he seemed to be maintaining that fision and fusion were not genuine metaphysical possibilities. Indeed, I thought that it was a motive for the account of person-hood that is offered that it looked likely to have that consequence. However, he has informed me that this is not a completely accurate understanding of his suggestion, and so it would be wrong to regard the present section as a discussion of an application of an idea of his.

13 I have been helped in formulating this by some remarks of David Wiggins.

14 Wilkes, , op. cit. (n. 5), 1.Google Scholar

15 Wilkes, ibid. 2.

16 She should have subtitled it—personal identity without the consideration of impossible cases.

17 Wilkes, , op. cit. (n. 5), 37.Google Scholar

18 Since A is a general assumption, further details can always be requested, but that does not amount to a significant unclarity as to what has been assumed, because it may well be that further details are simply irrelevant.

19 Wilkes, , op. cit. (n. 5), 47.Google Scholar

20 In making this proposal I am relying on the standard interpretation of what a theory of personal identity is. The strongest case which could be made for a recommendation like Wilkes's would be to argue for a novel interpretation of the problem, relative to which impossible cases are irrelevant.

21 Johnston, , op. cit. (n. 6), 59.Google Scholar

22 The case is one where we have a machine into which two people can enter. It scans their mental characteristics and, somehow, switches these characteristics between the people. It can work on one person, wiping clean his brain and inducing a new set of characteristics not based on a set already possessed by an individual.

23 Johnston, , op. cit. (n. 6), 70Google Scholar. The reason is that the first verdict shows that bodily continuity is not necessary, and the second that psychological continuity is not.

24 Ibid. 63.

25 Ibid. 70.

26 To deny the fourth premise in BTA is not to solve all the problems that brain transplants generate. In particular, I have not said what happens to the animal which donates the brain. The particular question is what our verdict should be if a new brain is transplanted into the skull vacated by the old one.

27 Earlier versions of this paper were presented in Oxford, Liverpool, and Lampeter, and the discussion on each occasion was very helpful. I am especially grateful to John Campbell, O. R. Jones, Michael Martin, Derek Parfit, and David Wiggins for their responses. I am also grateful to Brian Garrett and Galen Strawson for comments, and to David Cockburn for advice and patience.

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