Derek Parfit

(1942 - 2017)

This chapter discusses problems for informational patternism and the popular soul theory of personal identity, suggests that they are incoherent, and urges that the self does not really exist. It employs the science fiction pseudotechnology of a teleporter and presents the example of split brains from actual neuroscience cases. There are two theories about what persons are, and what is involved in a person's continued existence over time. On the Ego Theory, a person's continued existence cannot be explained except as the continued existence of a particular Ego, or subject of experiences. According to the Bundle Theory we must claim that there are long series of different mental states and events, each series being what we call one life. The split‐brain cases provide one argument for one view about the nature of persons. In the other, a person's brain is divided, and the halves are transplanted in two different bodies.

Suppose we discover how we could live for a thousand years, but in a way that made us unable to have children. Everyone chooses to live these long lives. After we all die, human history ends, since there would be no future people. Would that be bad? Would we have acted wrongly? Some pessimists would answer No. These people are saddened by the suffering in most people’s lives, and they believe it would be wrong to inflict such suffering on others by having children. In earlier centuries, this bleak view was fairly plausible. But our successors would be able to prevent most human suffering. Some optimists would also answer No . . . These [views] are, I believe, deeply mistaken. Given what our successors could achieve in the next million or billion years, here and elsewhere in our galaxy, it would be likely to be very much worse if there were no future people.

Presents actual cases of brain bisection; how we might be able to divide and reunite our minds; what explains the unity of consciousness at any time; the imagined case of full division, in which each half of our brain would be successfully transplanted into the empty skull of another body; why neither of the resulting people would be us; why this would not matter, since our relation to each of these people contains what matters in the prudential sense, giving us reasons to care about these people, which are like our reasons to care about our own future;and how it is hard to believe that personal identity, or our own continued existence, is not what matters.

One theory about rationality is the Self-interest Theory, or S. S claims that what each of us has most reason to do is whatever would be best for himself. And it is irrational for anyone to do what he knows would be worse for himself. When morality conflicts with self-interest, many people would reject the Self-interest Theory. But most of these people would accept one of the claims that S makes. This is the claim that we should not care less about our further future, simply because it is further in the future. We should not, for example, postpone pains at the foreseen cost of making them much worse. In our concern for our own self-interest, we should give equal weight to all the parts of our future. In this paper I shall discuss how a Self-interest Theorist should defend this claim.