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Personal Identity and the Irrelevance of Self-Interest

Self-interest is widely regarded as an important, if not as the only, source of reasons for action, and hence it is widely held that one can rationally give special weight to one’s self-interest in deciding how to act. In what follows, I will argue against this view. I will do so by following the lead of Derek Parfit, and considering cases in which personal identity appears to break down. My argument will differ from Parfit’s, however, in that it will have a stronger conclusion, it will involve fewer assumptions, and it will be compatible with a wider range of theories of personal identity.

The family of views I will be arguing against are self-interest theories of practical rationality. These theories come in varying strengths. According to the strongest version of this view, which we may call theStrong Obligation Theory, an agent is always rationally required to giveoverriding weightto her self-interest. On this view, if  is the option that an agent expects would result in her having the best life overall, then she is rationally required to choose option . According to what we may call the Weak Obligation Theory, an agent is only rationally required give some significant degree of special weight to her self-interest in deciding how to act. On this view, if there is some option, , such that an agent expects her life would go much better, as a whole, if she were to choose  than if she were to choose any alternative to , and if there is no relevant respect in which she expects that some alternative to  would be significantly better than , then she is rationally required to choose . While the Strong and Weak Obligation theories each state that an agent is rationally required to give a certain degree of weight to her self-interest, a self-interest theory might instead state only that it is always rationally permissible to give a certain weight to one’s self-interest. According to the Strong Permission Theory, it is always rationally permissible for an agent to give overriding weight to her self-interest. And according to the Weak Permission Theory, it is always rationally permissible for an agent to give some significant degree of special weight to her self-interest. In what follows, I will be arguing against all of these theories. I will focus on the weakest of these theories, Weak Permission Theory, since if I can show that this theory is false, it will follow that the others must be false as well.

But before presenting my own argument, it will be useful to review Parfit’s closely related argument, which is directed against the Strong Self-Interest Theory.

1. Parfit’s Argument

Parfit presents the following case.

Division: Clive’s is fatally injured, as are the brains of my two brothers. His brain is cloven in two, and each half is successfully transplanted into the body of one ofhis brothers. Each of the resulting people believes that he is Clive, seems to remember living Clive’s life, has Clive’s character, and is in every other way psychologically continuous with Clive. And he has a body that is very like Clive’s.

Parfit argues that Clive cannot be identified with anyone who exists after this operation is performed, and hence that we should say that Clive does not survive this operation.

Parfit also argues that Clive ought to regard what happens to him in Division as roughly as good as what happens to him in the following case:

No Division: Clive’s is fatally injured, as are the brains of his two brothers. The right half of his brain is destroyed, and the left half is transplanted into the body of one of his brothers. After the operation, the person who has the left half of Clive’s brain believes that he is Clive, seems to remember living Clive’s life, has Clive’s character, and is in every other way psychologically continuous with Clive. And he has a body that is very like Clive’s.[1]

In the second case, Parfit argues, the person who has the left half of Clive’s brain after the operation is Clive, and so Clive survives the operation. In both cases, those who exist after the operation will have temporal parts that stand in a special kind of causal-psychological relation with the temporal parts of Clive, a relation that Parfit calls “relation R” and that involves psychological continuity and connectedness. What accounts for the fact that the person who exists after the operation in No Division is Clive, while neither of the persons who exist after the operation in Division is not Clive, is that in Division, after the operation, there are two people whose temporal parts are R-related to those of Clive, and so relation R take a branching form, whereas in No Division, there is only one person whose temporal parts are R-related to those of Clive, and so this relations takes a non-branching form. Parfit concludes that personal identity is constituted by theR-relation taking a non-branching form.

But since, on Parfit’s view, Division is about as good as No Division, and since they differ only in that in Division, relation R takes a branching form, while in No Division this relation takes a branching form, Parfit concludes that what matters primarily is the existence of relation R, not whether this relation is branching or non-branching. And an important part ofrelation R, Parfit argues, is what he calls psychological connectedness, or the existence of direct psychological relations, such as relations of remembering, by which the temporal parts of persons are connected. Thus, Parfit argues,

Connectedness is one of the … relations that give me reason to be specially concerned about my own future. It can be rational to care less, when one of the grounds for caring will hold to a lesser degree. Since connectedness is nearly always weaker over longer periods, I can rationally care less about my further future.

But if I can rationally care less about my further future than about my nearer future, then I could rationally choose a greater harm in the further future over a lesser harm in the nearer future, even if this choice would make my life go worse as a whole. And this conclusion is incompatible with the strongest version of the self-interest theory, since the latter implies that we must always give overriding priority to making our lives as a whole go as well as possible.

his is Parfit’s argument against the strongest self-interest theory, in a nutshell. Though I believe that his argument has considerable force, I also believe that there are several points at which one could reasonably object to it. First, one might object that it involves an equivocation concerning “what matters in personal identity.” Parfit’s arguments seem to show that what makes our continuing to exist in the future a good thing is that it involves the existence of someone in the future whose temporal parts are R-related to our present self. Hence, Parfit seems to show that there is one sense in which relation R is what matters in personal identity: relation R explains why we should regard our continuing to exist as a good thing, or as a desirable outcome. But the reason why we should regard our continuing to exist as a desirable outcome may well differ from the reason why we should be especially concerned about our own welfare, given that we will continue to exist. By analogy, the reason why we should regard having children as a desirable outcome may differ from the reason why we should be specially concerned about the welfare of our children, given that we do have children. Thus, even if Parfit is right that relation R is what explains why continuing to exist is a good thing, one might reasonably object to the conclusion that relation R is what explains why we have special reason to be concerned about the welfare of our future self.

Second, even if we agree with Parfit that relation R is what explains why we have special reason to be concerned about our future self, and even if we likewise agree that psychological connectedness is an important part ofrelation R, and that psychological connectedness admits of degrees, we needn’t accept the conclusion that we can rationally be more concerned about those parts of our future to which we are most strongly psychologically connected. By analogy, even if one accepts the view that what explains why we have special reason to be concerned the welfare of human beings, as opposed to the welfare of cows or pigs, is that human beings have certain cognitive capacities that these other animals lack, and even if one likewise accepts the view that these cognitive capacities admit of degrees, one needn’t accept the conclusion that it is warranted to have greater concern for the welfare of geniuses who have these capacities to an extraordinarily high degree than for the welfare of people with ordinary cognitive capacities.

Fortunately, the comparison between Division and No Division allows for a much simpler argument, an argument that avoids the two objections just raised.

2. A Simpler Argument

Let us consider a special case of the choice between Division and No Division.

Happy Division: This is a version of Division in which it is assumed that Clive is 20 years old when the operation is performed, and that each of the resulting persons will live very happily for the next fifty years and then die.

Happy No Division: This is a version of No Division in which it is assumed that Clive is 20 years old when the operation is performed, and that the person who will have the left half of his brain after the operation will live very happily for the next fifty years and then die.

If Parfit is right that Division is about as good as No Division, and hence that Clive does not have much more reason to choose No Division than to choose Division, then presumably Clive likewise does not have much more reason to choose Happy No Division than to choose Happy Division.

Now suppose that Clive must choose between Happy Division and

Gamble: Clive takes a gamble. It is very likely that he will win the gamble, and in this case the gamble will have the same result asHappy No Division. But there is a small but significant chance that he will lose the gamble, and in this case he will be killed by having both halves of his brain destroyed.

If the chance of losing the gamble were zero, Gamble would be equivalent to Happy No Division. And as the probability of losing increases, Gamble progressively worsens. Hence, if Clive has at least as much reason to choose Happy Division as to choose Happy No Division, then he will have more reason to choose Happy Division than to choose Gamble. Now suppose Clive’s reasons to choose Happy Division are slightly outweighed by his reasons to choose Happy No Division. Nonetheless, so long as the difference between the strength of these reasons is sufficiently strong, Clive’s reasons to choose Happy Division will still outweigh his reasons to choose Gamble, since Gamble would involve a small but significant chance of death, and so Gamble would be considerably worse than Happy No Division. Thus, if Parfit is right that Clive has at least as much reason, or almost as much reason, to choose Happy Division as to choose Happy No Division, then Clive will have more reason to choose Happy Division than to choose Gamble. Hence, Clive ought rationally to choose Happy Division over Gamble. And indeed, this seems like the right result. For, at least prima facie, it would seem crazy to take a risk of having both halves of one’s brain destroyed simply in order to prevent the right half of one’s brain from being preserved and transplanted into another body, where the resulting person would go on to live a long and happy life.

But if we accept either of the strong versions of the self-interest theory, andif we agree with Parfit that Clive would not survive Happy Division but that he would survive Happy No Division, then we cannot maintain that Clive ought rationally to choose Happy Division over Gamble. For according to the strong versions of the self-interest theory, it is at least rationally permissible, if not rationally required, to give overriding weight to one’s self-interest in deciding how to act. And if Clive would not survive Happy Division but would survive Happy No Division, then while Happy Division would result in his surely ceasing to exist at the tender age of twenty, Gamble would make it very likely that he would live very happily to the age of seventy. And so Clive should expect his life to go better as a whole if he chooses Gamble than if he chooses Happy No Division. Hence, if Clive gives overriding weight to his self-interest, or how well his life goes, then he will choose Gamble over Happy Division. Thus, the Strong Obligation version of the self-interest theory, according to which one is always rationally required to give overriding weight to one’s self-interest, has the highly counterintuitive implication that Clive is rationally required to choose Gamble over Happy Division. And the Strong Permission version of the self-interest theory, according to which it is always rationally permissible to give overriding weight to one’s self-interest theory, has the counterintuitive implication that Clive could rationally choose Gamble over Division.

Thus, if we agree with Parfit about the conditions under which someone survives, and if we also agree with Parfit that Clive has about as much reason to choose Division as to choose No Division, then we can run a very simple argument against the strong versions of the self-interest that avoids the objections to Parfit’s original argument that we considered earlier. However, even this simpler argument involves some assumptions that one might reasonably reject. For one might hold that if Parfit is right in claiming that Clive would survive in Division but not in No Division, then he cannot be right in denying that Clive has much more reason to choose No Division than to choose Division. For one might hold that how much reason an agent has to choose an option can depend at least in part on the degree to which this option would achieve one’s rational goals or objective. And one might hold that Clive could rationally have goals or objective that could be fulfilled in No Division, but that could not be fulfilled in Division. One might hold, for example, that Clive could rationally have the aim thatherun the Boston Marathon, or that he to marry Peggy-Sue. On Parfit’s view, if Clive chooses No Division, he will survive, and so he may well run the Boston Marathon and marry Peggy-Sue, but if he chooses Division, then he will not survive, and so he will not run the marathon or marry his beloved. Of course, someone very like him may marry Peggy-Sue or run the marathon, but this would not fulfill his aim that he do these things. Hence, one might hold that if Parfit is right about personal identity, then Clive may well have significantly stronger reason to choose No Division than to choose Division.[2]

Suppose, however, that we accept Parfit’s views about survival, and that we also accept his view that Division would be about as choiceworthy as No Division. In this case, as we have seen, we must reject the strong versions of the self-interest theory, according to which it is rationally required, or at least rationally permissible, to give overriding weight to one’s self-interest. But we needn’t reject the weak versions of the self-interest theory, according to which it is rationally required, or at least rationally permissible, to give a significant degree of special weight to one’s self-interest. For choosing Happy Division over Gamble is compatible with giving suchspecial weight to one’s self-interest. For one might hold that while Gamble is significantly better than Happy Division with respect to self-interest, Happy Division is significantly better than Gamble with respect to other important considerations, such as total utility. After all, Happy Division is sure to result in a total of 100 years of happy life, while Gamble will result in either fifty years or zero years of happy life, depending on whether the gamble is won or lost. Thus, even if the weak self-interest theories are true, and Clive is rationally permitted, or even rationally required, to give significant weight to the reasons of self-interest that favor Gamble, it may be that he should also give significant weight to other kind of reasons that favor Happy Division, and that, taking all these reasons into account,he should choose Happy Division over Gamble.

Thus, in order to argue for the rejection of the weak versions of the self-interest theory, we will need a stronger argument.[3]

3. Divide and Torture

Suppose that Clive must choose between the following two options:

Single Torture:As in Happy No Division, at the age of twenty, the right half of Clive’s brain is destroyed, and the left half is transplanted into the body of one of his brothers whose brain has been fatally injured. And after the operation, the person who has the left half of Clive’s brain is psychologically just like Clive. However, in the present case, after the operation, this person undergoes fifty years of excruciating torture and is then killed.