Derek Parfit was one of the most important and influential moral philosophers of the late 20th and early 21st centuries. This Element offers a critical introduction to his wide-ranging ethical thought, focusing especially on his two most significant works, Reasons and Persons and On What Matters, and their contribution to the consequentialist moral tradition. Topics covered include: rationality and objectivity, distributive justice, self-defeating moral theories, Parfit's Triple Theory, personal identity, and population ethics.

Revisionary theories of logic or truth require revisionary theories of mind. This essay outlines nonclassically based theories of rational belief, desire, and decision making, singling out the supervaluational family for special attention. To see these nonclassical theories of mind in action, this essay examines a debate between David Lewis and Derek Parfit over what matters in survival. Lewis argued that indeterminacy in personal identity allows caring about psychological connectedness and caring about personal identity to amount to the same thing. The (...) essay argues that Lewis's treatment of two of Parfit's puzzle cases—degreed survival and fission—presuppose different nonclassical treatments of belief and desire. (shrink)

Some philosophers believe that everyday objects are 4-dimensional spacetime worms, that a person (for example) persists through time by having temporal parts, or stages, at each moment of her existence. None of these stages is identical to the person herself; rather, she is the aggregate of all her temporal parts.1 Others accept “three dimensionalism”, rejecting stages in favor of the notion that persons “endure”, or are “wholly present” throughout their lives.2 I aim to defend an apparently radical third view: not (...) only do I accept person stages; I claim that we are stages.3 Likewise for other objects of our everyday ontology: statues are statue-stages, coins are coin-stages, etc. At one level, I accept the ontology of the worm view. I believe in spacetime worms, since I believe in temporal parts and aggregates of things I believe in. I.. (shrink)

Personal identity is not always symmetric: even if I will not be a later person, the later person may have been me. What makes this possible is that the relations that are criterial of personal identity---such as memory and anticipation---are asymmetric and "count in favor of personal identity from one side only". Asymmetric personal identity can be accommodated by temporal counterpart theory but not by Lewisian overlapping aggregates of person stages. The question of uncertainty in cases of personal fission (and (...) in Everettian quantum mechanics) is also discussed. (shrink)

Following Lewis, it is widely held that branching worlds differ in important ways from diverging worlds. There is, however, a simple and natural semantics under which ordinary sentences uttered in branching worlds have much the same truth values as they conventionally have in diverging worlds. Under this semantics, whether branching or diverging, speakers cannot say in advance which branch or world is theirs. They are uncertain as to the outcome. This same semantics ensures the truth of utterances typically made about (...) quantum mechanical contingencies, including statements of uncertainty, if the Everett interpretation of quantum mechanics is true. The ‘incoherence problem’ of the Everett interpretation, that it can give no meaning to the notion of uncertainty, is thereby solved. IntroductionMetaphysicsPersonal fissionBranching worldsPhysicsObjections. (shrink)

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In his work on personal identity, Derek Parfit makes two revolutionary claims: firstly, that personal identity is not what matters in survival; and secondly, that what does matter is relation R. In this article I demonstrate his position here to be inconsistent, with the former claim being defensible only in case the latter is false. Parfit intends his famous fission argument to establish the unimportance of identity – a conclusion disputed by, among others, Mark Johnston. My approach is to critically (...) assess their debate, focusing on Johnston's reductio of Parfit's position. I contend that although Parfit's own response fails, there are other ways to save the fission argument. The unimportance of identity then comes at a cost, however, because the reductio can only be avoided by accepting either that nothing matters in survival, or else that facts about particles and forces do. Either way, relation R cannot be what matters. (shrink)

Derek Parfit’s thesis that identity doesn’t matter in survival has been extensively discussed except for its metaphysical robustness. How can we justify the abandonment of identity in the way Parfit suggests? My argument is the following. Those who want to endorse the thesis that identity doesn’t matter (and, therefore, abandon identity across time) should adopt exdurantism, i.e. a metaphysics according to which the world is composed by temporal parts each existing at a time and according to which there is nothing (...) as a numerically same entity which exists at different times. I show that the metaphysics behind Parfit’s theory is neither compatible with endurantism, according to which object persists by being wholly present at different times, nor with perdurantism, according to which entities are aggregates of temporal and spatial parts. (shrink)

I argue that perceptual content is always affected by the allocation of one’s attention. Perception attributes determinable and determinate properties to the perceived scene. Attention makes (or tries to make) our perceptual attribution of properties more determinate. Hence, a change in our attention changes the determinacy of the properties attributed to the perceived scene.

The fission of a person involves what common sense describes as a single person surviving as two distinct people. Thus, say most metaphysicians, this paradox shows us that common sense is inconsistent with the transitivity of identity. Lewis’s theory of overlapping persons, buttressed with tensed identity, gives us one way to reconcile the common sense claims. Lewis’s account, however, implausibly says that reference to a person about to undergo fission is ambiguous. A better way to reconcile the claims of common (...) sense, one that avoids this ambiguity, is to recognize branching persons, persons who have multiple pasts or futures. (shrink)

David Lewis's cohabitation theory suffered damaging criticism from Derek Parfit. Though many have defended versions of Lewis's theory Parfit's criticism has not been answered. This paper shows how to defend the cohabitation theory against Parfit's criticism.

Personites are like continuant people but shorter-lived. Johnston argues that personites do not exist since otherwise personites would have the same moral status as persons, which is untenable. I argue that Johnston’s arguments fail. To do that I propose an alternative way to understand intrinsicness and I clarify the meaning of reductionism about persons. I also argue that a plausible ethical theory is possible even if personites have the same moral status as persons. My arguments draw on Johnston’s earlier debate (...) with Parfit about personal identity and the place of ordinary concerns in a naturalistic world. I also describe an important but metaphysics-free problem that arises from Johnston’s discussion. (shrink)

Derek Parfit famously defends a number of surprising views about "fission." One is that, in such a scenario, it is indeterminate whether I have survived or not. Another is that the fission case shows that it does not matter, in itself, whether I survive or not. Most critics of the first view contend that fission makes me cease to exist. Most opponents of the second view contend that fission does not preserve everything that matters in ordinary survival. In this paper (...) I shall provide a critique that does not rely on either of these contentions. There are other, interrelated reasons to reject Parfit's defense of the two theses. In particular, the availability of the following view creates trouble for Parfit: I determinately survive fission, but it is indeterminate which fission product I am. (shrink)

The defensibility of the extended mind thesis (EMT) is often thought to hinge on the possibility of extended selves. I argue that the self cannot extend and consider the ramifications of this finding, especially for EMT. After an overview of EMT and the supposed cruciality of the extended self to the defensibility of the former thesis, I outline several lines of argument in support of the possibility of extended selves. Each line of argument appeals to a different account of diachronic (...) personal identity. I argue that no such argument for extended selves succeeds, as no account of diachronic personal identity is both plausible and supports the view that the self can extend. Next, I consider three objections that, if successful, would undercut the preceding argument that the self cannot extend. I conclude by reflecting on the implications of the conclusion that the self cannot extend, including the prospects for EMT. (shrink)

Derek Parfit’s argument against the platitude that identity is what matters in survival does not work given his intended reading of the platitude, namely, that what matters in survival to some future time is being identical with someone who is alive at that time. I develop Parfit’s argument so that it works against the platitude on this intended reading.

The debate on personal persistence has been characterized by a dichotomy which is due to its still Cartesian framwork: On the one side we find proponents of psychological continuity who connect, in Locke’s tradition, the persistence of the person with the constancy of the first-person perspective in retrospection. On the other side, proponents of a biological approach take diachronic identity to consist in the continuity of the organism as the carrier of personal existence from a third-person-perspective. Thus, what accounts for (...) someone’s persistence over time, is the continuity of his mind on the one hand, and the continuity of his body on the other. In contrast to those views, the paper intends to show that bodily existence represents the basis of selfhood across time, both as the continuity of the experiential self and as the continuity of the autopoietic organism. On the one hand, the lived body conveys a continuity of the self from a first-person perspective, namely a pre-reflective feeling of sameness or a felt constancy of subjectivity. Moreover, an analysis of awakening and sleep shows that there is a continuous transition from full wakefulness to periods of deep sleep which may thus not be regarded as a complete interruption of subjective experience. On the other hand, this constancy converges with the continuity of the organismic life process as conceived from a third-person perspective. Thus, the experiential self of bodily subjectivity and the autopoietic self of the living organism should be regarded as two aspects of one and the same life process. Finally, the lived body also exhibits a specific form of memory that results from the continual embodiment of existence: it consists of all the affinities, capacities and experiences, which a person has acquired throughout his life. Thus, it provides a continuity of self that must not be actively produced through remembering, but rather integrates the person’s entire past in his present being and potentiality. (shrink)

Parfit has argued for the revolutionary thesis that personal identity does not matter in ordinary survival, only the R-relation does. “Reconciliationists,” such as Lewis, have tried to stop this revolution, arguing that both personal identity and the R-relation matter. The disagreement has been between those who hold that only the R-relation matters and those who hold that, in addition, personal identity matters. But there is a third option. I argue that Parfit is right that personal identity does not matter but (...) he is wrong that the R-relation matters, and the reconciliationists are wrong to think both matter since neither does. (shrink)

Given reductionism about people, personal persistence must fundamentally consist in some kind of impersonal continuity relation. Typically, these continuity relations can hold from one to many. And, if they can, the analysis of personal persistence must include a non-branching clause to avoid non-transitive identities or multiple occupancy. It is far from obvious, however, what form this clause should take. This paper argues that previous accounts are inadequate and develops a new proposal.

According to the Psychological-Continuity Account of What Matters, you are justified in having special concern for the well-being of a person at a future time if and only if that person will be psychologically continuous with you as you are now. On some versions of the account, the psychological continuity is required be temporally ordered, whereas, on other versions, it is allowed to be temporally unordered. In this paper, I argue that the account is implausible if the psychological continuity is (...) allowed to be temporally unordered. I also argue that, if the psychological continuity is required to be temporally ordered, it cannot plausibly be purely psychological (in the sense that the psychological continuity is not required to be caused through spatio-temporal continuity of a brain). The upshot is that no plausible version of the Psychological-Continuity Account of What Matters is purely psychological. So psychological continuity is not what matters in survival. (shrink)

En este artículo se plantea una reconsideración de la elección del reduccionismo de Parfit en Razones y personas como la posición que mejor explica el vínculo de dos sucesos mentales separados en el tiempo. Sin embargo, veremos cómo Parfit basa dicha elección en la consideración de la noción de persona como una sustancia, lo que en principio deja fuera cualquier otra perspectiva. El problema aparece cuando éste no considera apropiadamente el origen histórico de la pregunta en Locke, donde la noción (...) de “persona” se caracteriza en función de la “conciencia de sí”, lo que abre la posibilidad de entender dicha noción a partir de su naturaleza modal en vez de sustancial. En esta medida, se verá cómo esta tercera alternativa incluye una explicación de la conciencia de sí que podría considerarse más razonable bajo los propios términos de Parfit. (shrink)

Both arguments are based on the breakdown of normal criteria of identity in certain science-fictional circumstances. In one case, normal criteria would support the identity of person A with each of two other persons, B and C; and it is argued that, in the imagined circumstances, A=B and A=C have no truth value. In the other, a series or spectrum of cases is tailored to a sorites argument. At one end of the spectrum, persons A and B are such that (...) A=B is clearly true; at the other end, A and B are such that the identity is clearly false. In between, normal criteria of identity leave the truth or falsehood of A=B undecided, and it is argued that in these circumstances A=B has no truth value.These arguments are to be understood counterfactually. My claim is that, so understood, neither establishes its conclusion. The first involves a pair of counterfactual situations that are equally possible or tied. If A=B and A=C have no truth value, a counterfactual conditional with one of them as consequent and an antecedent that is true in circumstances in which either is true should have no truth value. Intuitively, however, any such counterfactual is false. The second argument can be seen to invite an analogous response. If this is right, however, there is an important disanalogy between this and the classical paradox of the heap. If the disanalogy is only apparent, the argument shows at most that the existence of persons can be indeterminate. (shrink)

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How does the concept of a person affect our beliefs about ourselves and the world? In an intriguing recent addition to his established Reductionist view of personal identity, Derek Parfit speculates that there could be beings who do not possess the concept of a person. Where we talk and think about persons, selves, subjects, or agents, they talk and think about sequences of thoughts and experiences related to a particular brain and body. Nevertheless their knowledge and experience of the world (...) is unaffected, in that it is largely like our own. It is their view of ‘themselves’ that is different (and superior) to ours. My paper critically assesses this ‘impersonal beings’ hypothesis through an examination of Parfit’s construal of the concept of a person. I argue that Parfit’s understanding of the concept of a person undermines his impersonal beings hypothesis. (shrink)

How should we count people who have two cerebral hemispheres that cooperate to support one mental life at the level required for personhood even though each hemisphere can be disconnected from the other and support its "own" divergent mental life at that level? On the standard method of counting people, there is only one person sitting in your chair and thinking your thoughts even if you have two cerebral hemispheres of this kind. Is this method accurate? In this paper, I (...) argue that it is not, and I advocate an alternative I call the Multiple Person View. (shrink)

This seminal contribution to Kant studies, originally published in 1982, was the first to present a thorough survey and evaluation of Kant's theory of mind. Ameriks focuses on Kant's discussion of the Paralogisms in the Critique of Pure Reason, and examines how the themes raised there are treated in the rest of Kant's writings. Ameriks demonstrates that Kant developed a theory of mind that is much more rationalistic and defensible than most interpreters have allowed.

The purpose of this thesis is to provide a brief examination of the historical accounts of philosophical theories of personal identity and show the influence that each has had on the development of contemporary theories. In doing so, the thesis explores the problems associated with these theories, attempting to establish a meta-theory of personal identity. What is demonstrated is that the fundamental problems of personal identity arise from issues related to the use of language, as well as assumptions involving the (...) concept of personhood. By demonstrating that our understanding of personhood is relative to frameworks of understanding based on assumption, the meta-theory states that propositions made about persons are not factual statements, but are, rather, matters of contingency. As such, propositions about persons contain truth-value only within a particular frame of reference that is based on these assumptions. Therefore, the problems that traditionally arise in theories of personal identity -- problems with dualism, the mental criterion, and bodily criterion -- result from a flawed approach to the problem altogether. The conclusion is that it is possible to construct a theory of personal identity, but not the theory of personal identity. (shrink)