Personal identity

6. Value theory

In this final section, I investigate the implications (if any) of the metaphysics of personal identity for value theory. A contemporary philosopher, Derek Parfit, is the most well-known advocate of such implications: he argues that the most plausible metaphysics of persons yields radical conclusions for ethics and rationality (value theory).

It has, of course, long been acknowledged that there is a link between theories of persons and value theory. For example, a religious person’s belief that we are immaterial souls will obviously bear on their view of the morality of abortion and euthanasia. However, in this case, the value of persons is not called into question; what is in question is simply the extension of the concept person. The intent of Parfit’s project is far more subversive: it is to undermine the significance we currently attach to personal identity and distinctness. Whether or not it is ultimately successful, it is important to recognize the form or shape of this project.

The central feature of Parfit’s value theory is the thesis that personal identity is not, in itself, an important relation. It is various psychological relations which matter, relations which are concomitants of personal identity in the normal case (but not, for example, in the case of fission). According to this theory, it would be irrational of me strongly to prefer my own continued existence to death by fission.

I will be concerned with arguments for the thesis that personal identity is not what matters. This thesis has two strands. One strand is that personal identity over time is unimportant; the other strand is that personal identity at a time is unimportant. (These are the diachronic and synchronic strands, respectively.) The thesis that the identity of a person over time is unimportant has been taken to undermine the self-interest theory of rationality, and has implications for the tenability of trans-temporal moral notions such as compensation, responsibility and personal commitment. The thesis that the identity and distinctness of persons at a time is unimportant has been thought to lend support to utilitarianism.

The thesis that personal identity over time is unimportant implies that pure self-interested concern is irrational. That is, it is irrational for me to be especially concerned about the fate of some future person just because that person is me. It follows that the self-interest theory of rationality is false. According to this theory, which has dominated so much thinking about rationality (see Rationality, practical) there is only one future person that it is supremely rational for me to benefit: the future person identical to me. Since the self-interest theory places immense weight on a relation which has no rational significance, this theory cannot be correct.

Further, if we do not believe that personal identity over time is important, this may change our attitude to punishment, compensation and commitment. Consider a case where there are only weak psychological connections between different stages of the same life. (For example, a one-time criminal may now be completely reformed, with a new and more respectable set of desires and beliefs.) On the present view, the grounds are thereby diminished for holding the later self responsible for the crimes of the earlier self, or for compensating the later self for burdens imposed on the earlier self, or for regarding earlier commitments as binding on the later self. The truth that the earlier person is the later person is too superficial or unimportant to support the opposite view.

The thesis that the identity and distinctness of persons at a time is unimportant has been taken to imply that the fact of the ‘separateness of persons’ is not ‘deep’, and that less weight should be assigned to distributive principles. The synchronic thesis thus supports (in part) the utilitarian doctrine that no weight should be assigned to distributive principles: we should simply aim to maximize the net sum of benefits over burdens, whatever their distribution (see Utilitarianism).

These are radical claims. They are all underwritten by the thesis that personal identity is not what matters. What are the arguments for this thesis? I shall discuss one argument for the diachronic thesis (the argument from fission), and one argument for the synchronic thesis (the argument from reductionism).

Recall our earlier discussion of fission. I argued that the most plausible description of fission is that the pre-fission person is numerically distinct from the post-fission offshoots. This constitutes the first premise of the argument from fission (which I will present in the first person): (1) I am not identical to either of my fission products. The second premise is this: (2) fission is not as bad as ordinary death. This premise is taken to imply a third: (3) my relation to my offshoots contains what matters. The first and third premises jointly imply that personal identity is not what matters.

This is an interesting argument, which has had many adherents in recent years. But there is a problem with it. The problem concerns the move from the second to the third premise. The second premise is certainly true: the prospect of fission is not as bad as that of ordinary death. What grounds this premise, and what exhausts its true content, is simply that presented with a choice between those two options, virtually everyone would choose fission. Such a choice is both explicable and reasonable: after fission, unlike after ordinary death, there will be people who can complete many of my projects, look after my family, and so on. However, if the third premise is grounded in the second, the claim that my relation to my offshoots contains what matters merely reflects the innocuous truth that fission is preferable to ordinary death. This robs the argument of any radical import. Its conclusion does nothing to undermine the rationality of self-interest, or the rationality of strongly preferring continued existence to both fission and ordinary death. (This argument is not improved if it is merely asserted that fission is just as good as ordinary survival. What is the argument for this claim?)

What of the argument from reductionism? Reductionism is the view that a description of reality which refers to bodies and experiences, but omits reference to persons, can be complete. It would leave nothing out (see Persons §3). The argument from reductionism attempts to show that, if reductionism is true, the fact of the separateness of persons (the fact that you and I are distinct persons, for example) is not deep or significant, and hence less weight should be assigned to distributive principles.

The argument can be presented as follows. Suppose that reductionism is true: reality can be completely described without reference to persons. If such a complete and impersonal description is possible, how can the boundaries between persons be important? Failing an answer to this question, the argument from reductionism concludes that the boundaries between persons are not morally significant.

The validity of this argument turns on the truth of the general principle that if reality can be completely described without referring to Fs, then the boundaries between Fs cannot be of any importance. Both the interpretation and plausibility of this principle are unclear. A more definite worry is that reasons may be presented for dissatisfaction with the argument’s premise, reductionism about persons. (In particular: can our mental life really be completely described in impersonal or identity-neutral terms?) Unless those objections can be met, we should reject the argument from reductionism.

The central arguments for the thesis that identity is not what matters are both open to dispute. The failure of these arguments emphasizes how difficult it is to undermine the importance I attach to the fact that such-and-such a person tomorrow is me, and to the fact that you are not me. Unless other arguments are forthcoming, we can continue reasonably to believe that personal identity is important, and to endorse the traditional views in ethics and rationality which that belief supports.