Parfit

Derek Parfit (1942-2017)

Parfit taught at All Souls College, Oxford University. He made important contributions to the fields of ethics and metaphysics. In his book Reasons and Persons, Parfit investigates a range of problems dealing with ethics, time and endurance through time and personal identity.1 The first part of the book deals with moral stances that are either directly or indirectly self-defeating. Part Two deals with issues in rationality and time. Part Three explores personal identity, and Part Four investigates the consideration of our actions on future generations. A conclusion toward which he argues is that, generally speaking, our ethical reasoning would be more sound if we could learn to take ourselves less personally. That book was published in 1984, two years after Collins’s book. Both Collins (1982) and Parfit (1984) build upon ideas outlined in Parfit’s 1971 article called “Personal Identity.”2

Statement of the problem

In the opening section of his article, Parfit states what his agenda is: “My targets are two beliefs: one about the nature of personal identity, the other about its importance.”3

First, about personal identity there is the belief that the question about identity must have an answer. That is, the belief is that there should not be cases in which it is impossible to decide whether two conscious states belong to the same person.

This belief might be expressed as follows: “Whatever happens between now and any future time, either I shall still exist, or I shall not. Any future experience will either be my experience, or it will not.”4

The implication of this belief, says Parfit, is that

It makes people assume that the principle of self-interest is more rationally compelling than any moral principle.5 And it makes them more depressed by the thought of ageing and of death.6

Second, about the importance of this concern with identity there is the belief that “unless the question about identity has an answer, we cannot answer certain important questions (questions about such matters as survival, memory, and responsibility.)” About that Parfit says:

Against this second belief my claim will be this. Certain important questions do presuppose a question about personal identity. But they can be freed of this presupposition. And when they are, the question about identity has no importance.7

Parfit does not claim that he can definitively prove that these two beliefs are false; he will be content to show that they pose some real problems and that it would therefore not be irrational to abandon these beliefs.

Discussion of the first belief

The belief to be discussed is: “Whatever happens between now and any future time, either I shall still exist, or I shall not. Any future experience will either be my experience, or it will not.” To show that there is a problem with this belief, Parfit refers to a thought experiment in which a scenario is given in which it becomes very difficult to decide whether or not some future experience belongs to a formerly existing person. The thought experiment, originally devised by David Wiggins, goes like this:

My brain is divided, and each half is housed in a new body. Both resulting people have my character and apparent memories of my life. What happens to me? There seem to be only three possibilities: (1) I do not survive; (2) I survive as one of the two people; (3) I survive as both.

Alternatives 1 and 2 are immediately dismissed as highly improbable. If my thoughts and memories and personality and so on continue, then why should it be said that I do not survive? And if they continue equally in two different bodies, how could I possibly prefer one alternative to the other? This leaves the third alternative as the most likely.

There is bound to be initial resistance to the third alternative, because we are accustomed to thinking of a person has having only one consciousness, not two of them simultaneously. And yet there have been cases where the links between the two hemispheres of the brain are severed, and people who have had the operation report that what they experience is two simultaneous trains of thought and experience. Neuropsychological experiments suggest that each hemisphere supports a flow of consciousness, and that both of these are experienced at the same time. If this situation is irreversible, then we begin to feel tempted to say that there are now two persons existing simultaneously. We would then say that the person who was once united has continued to survive as two persons. So there is no reason to rule this possibility out.

There is one further alternative, which Parfit ends up preferring:

The alternative, for which I shall argue, is to give up the language of identity. We can suggest that I survive as two different people without implying that I am these two people.8

The main reason that Parfit gives for preferring this new alternative is that the perplexity posed by Wiggins’ thought experiment now disappears. Instead of having a question that has three possible answers, each of which seems contrary to reason, we can dismiss the question as one that need not be answered, because it rests on a false presupposition.

Parfit observes that there are many instances in which we do not feel we need to answer the question of whether A and B are identical. We do not feel a need to decide whether the England before 1066 was the same England as the England after 1066; we do not feel a need to say whether a machine is the same machine when it undergoes changes of parts.

Discussion of the second belief

The belief to be discussed is: “unless the question about identity has an answer, we cannot answer certain important questions (questions about such matters as survival, memory, and responsibility).” Parfit’s strategy will be to show that we can meaningfully talk about survival, memory and responsibility without reference to the concept of identity.

Parfit begins with a discussion of kinds of relation. Identity is always a one-one relation. That is, it is a binary relation in which exactly one term satisfies the relation when another term is specified. For example, x=y+1 is one-one, because for every value of x there will be exactly one value of y that makes the statement true. But x>y is one-many, since for every value of x there are infinite values of y that are of lesser value than x.

Identity is a one-one relation. For any term there will be exactly one term that is identical to it. But survival, as Wiggins’ thought experiment shows, can be one-many. One person with a brain whose hemispheres have not be severed survives as two persons when the hemispheres have been severed.

Another way of stating all this is that personal identity is all or nothing, while personal survival can be a matter of degrees. So when a person is, say, 80 years old, we can ask whether the 15-year-old girl she once was has survived. And we don’t feel cheated when the answer is “Well, to some extent she has survived. Many of the personality traits she had at age 15 are no longer present, but in other ways she is the same old girl she used to be.” This kind of answer is not available to us when we insist on asking “Is she, at the age of 80, identical to the person she used to be at the age of 15?”

Parfit’s conclusions

Parfit claims that his argument, if accepted, will have two consequences:

  1. When the notion of personal identity is no longer in the picture, then ethical problems are no longer reduced to a dilemma of deciding whether it is better to act out of self-interest or out of general interest. All ethical problems now become simply deciding what is of general interest.
  2. The worry about what will happen after death seems to be intensified by the belief that there is only one self, and that either this will survive or it will not. But this worry, claims Parfit, is not entirely natural. Rather, it is one that arises from the presupposition that there is a single self in the first place. If this presupposition can be seen to be at least questionable, then the idea that some aspects of what one now is will survive while others will not is not likely to produce much anxiety.

Now that the views of John Locke and Derek Parfit have been examined, let us see how these views of Western philosophers might be applied to traditional Buddhist views of non-self (anātman).


  1. Derek Parfit, Reasons and Persons, (Oxford: Clarendon Press, 1984). ↩︎
  2. Derek Parfit, “Personal Identity,” Philosophical Review 80, no. 1 (1971):. In this module I shall refer to the pagination of a reprint of the article in Derek Parfit, “Personal Identity,” in Metaphysics: Contemporary Readings, ed. Michael J Loux, (London: New York: Routledge, 2001). ↩︎
  3. Parfit, “Personal Identity,” p. 374. ↩︎
  4. Parfit, “Personal Identity,” p. 374. ↩︎
  5. Some moral philosophers, such as the eighteenth-century Christian minister Joseph Butler (1692‒1752), have argued that the most rational form of ethics is to pursue what one recognizes, in a moment of “cool self-interest” to be to one’s advantage. The key here for these philosophers is that when one takes a dispassionate look at what one’s real interests are, one will know that it is in one’s interests to look out for the needs of others. But one does not take care of others for their sake, but for one’s own sake. ↩︎
  6. Parfit, “Personal Identity,” p. 374. ↩︎
  7. Parfit, “Personal Identity,” p. 375. ↩︎
  8. Parfit, “Personal Identity,” p. 377. ↩︎

Works cited

  • Parfit, Derek. “Personal Identity.” Philosophical Review 80, no. 1 (1971):
  • ________. Reasons and Persons. Oxford: Clarendon Press, 1984.
  • ________. “Personal Identity.” In Metaphysics: Contemporary Readings, ed. Michael J Loux, 374‒394. London; New York: Routledge, 2001.

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