Fission and Split Brains

If we were to connect two individuals’ brains together, how would this affect the individuals’ conscious experiences? In particular, it is possible for two people to share any of their conscious experiences; to simultaneously enjoy some token experiences while remaining distinct subjects? The case of the Hogan twins—craniopagus conjoined twins whose brains are connected at the thalamus—seems to show that this can happen. I argue that while practical empirical methods cannot tell us directly whether or not the twins share conscious (...) experiences, considerations about the locality of content processing in the brain entails that they most likely do so. (shrink)

When does a human being cease to exist? For millennia, the answer to this question had remained largely unchanged: death had been diagnosed when heartbeat and breathing were permanently absent. Only comparatively recently, in the 1950s, rapid developments in intensive-care medicine called into question this widely accepted criterion. What had previously been deemed a permanent cessation of vital functions suddenly became reversible. -/- A new criterion of death was needed. It was suggested that the destruction of the brain could indicate (...) the death of the organism in the presence of external life support. Soon the so-called brain death became the new worldwide standard. In recent years, however, doubts about this neurological criterion have been growing. Is brain death really our death? -/- This is the question that this thesis seeks to answer. To this end, we shall connect the medical debate about the definition of death to the philosophical debate about personal identity. While we will find that the destruction of its brain does in fact not correspond to an organism’s death, we shall also ask whether the assumption that we are essentially organisms is correct. May brain death be the ceasing to exist of a different entity? -/- Substituting clinical case reports and considerations about human physiology for the use of thought experiments, the thesis takes a novel and philosophically unconventional approach to the problem of what we essentially are. We shall analyse various pathological conditions and their respective effects on the bodily and mental characteristics of our existence. We will conclude that brain death is indeed our death – but for reasons entirely different from those cited in the original justification of this criterion. (shrink)

The law of successor criminal liability is simple—corporate successors are liable for the crimes of their predecessors. Always. Any corporation that results from any merger, consolidation, spin-off, etc., is on the hook for all the crimes of all the corporations that went into the process. Such a coarse-grained, onetrack approach fails to recognize that not all reorganizations are cut from the same cloth. As a result, it skews corporate incentives against reorganizing in more socially beneficial ways. It also risks punishing (...) corporate successors unjustly. -/- This Article offers a more sophisticated approach to successor liability: successors should be liable for the crimes of their predecessors only when they inherit their predecessors’ compliance vulnerabilities. In the terms developed by this Article, these successors share a “criminal identity” with their predecessors. Such an approach would incentivize corporations to structure reorganizations in ways that improve compliance and minimize the likelihood of future offenses. At the same time, it would do a better job of ensuring that. (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.

Spesso i filosofi paiono pensare di poter trarre conclusioni radicali sulla base di una semplice discussione di scenari immaginari, scenari che a volte sembrerebbero tratti da un racconto di fantascienza. Questo stile argomentativo lascia molti studenti (e anche alcuni filosofi di professione) perplessi: come può il semplice riflettere su di uno scenario immaginario permetterci di trarre conclusioni su come stanno le cose nella realtà? Questo volume cerca di giustificare l'uso di esperimenti mentali in filosofia, concentrandosi su due casi studio, entrambi (...) tratti dalla letteratura sull'identità personale: la trasformazione di un essere umano in un'entità sintetica, e la divisione di una persona in due individui distinti. (shrink)

Jason Bowers and Meg Wallace have recently argued that those who hold that every individual instantiates a ‘haecceity’ are caught up in a Euthyphro-style dilemma when confronted with familiar cases of fission and fusion. Key to Bowers and Wallace’s dilemma are certain assumptions about the nature of metaphysical explanation and the explanatory commitments of belief in haecceities. However, I argue that the dilemma only arises due to a failure to distinguish between providing a metaphysical explanation of why a fact holds (...) vs. a metaphysical explanation of what it is for a fact to hold. In the process, I also shed light on the explanatory commitments of belief in haecceities. (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.

According to the Psychological Account of personal identity, personal identity across time is maintained by some form of psychological overlap or continuance. I show that the Psychological Account has trouble accommodating cases of transient retrograde amnesia. In such cases, the transitivity of psychological continuity may break down. I consider various means of responding to this problem, arguing that the best available response will undercut our ability to rely on intuitions about brain transplantation to support the Psychological Account. When the Psychological (...) Account is re-interpreted in such a way as to overcome the problems posed by cases of transient retrograde amnesia, it turns out that standard brain transplantation cases involve details which are strictly irrelevant according to the theory. On the other hand, these features seem to drive our intuitions about survival in these cases. In this way, my argument undermines one of the key motivations for adopting the Psychological Account. (shrink)

Elizabeth Schechter explores the implications of the experience of people who have had the pathway between the two hemispheres of their brain severed, and argues that there are in fact two minds, subjects of experience, and intentional agents inside each split-brain human being: right and left. But each split-brain subject is still one of us.

In der Diskussion um personale Identität nehmen die einflussreichen Arbeiten Derek Parfits eine Sonderstellung ein, insofern Parfit nicht bestrebt ist, eines der gängigen Identitätskriterien zu verteidigen, sondern vielmehr behauptet, dass unsere alltäglichen wie philosophischen Vorstellungen von personaler Identität unrettbar inkohärent sind und deshalb aufgegeben werden sollten. In seinem Beitrag beleuchtet Sascha Settegast die verschiedenen Argumente, die Parfit für diese provokante These vorbringt, und unternimmt insbesondere den Versuch einer systematischen Dekonstruktion der wichtigsten Gedankenexperimente Parfits, die zeigen soll, dass sich diese Gedankenexperimente (...) auf eine Weise auflösen lassen, die unsere alltäglichen Intuitionen über personale Identität intakt belässt. Settegast entwickelt dabei die Grundzüge einer Konzeption personaler Identität, die sich einerseits von den gängigen neo-lockeanischen und animalistischen Ansätzen abgrenzt und andererseits bewusst an den zeitgenössischen Neo-Aristotelismus in der Ethik anknüpft, wie er etwa bei Philippa Foot und Michael Thomp-son anzutreffen ist. Die diachrone numerische Identität menschlicher Personen gründet nach Settegasts Auffassung darin, dass der Verlauf ihres Lebens eine zeitliche Einheit aufweist, die dadurch bedingt ist, dass ihre Lebensführung die menschliche Lebensform auf eine individuell charakteristische Weise exemplifiziert. Insofern dies aber nur durch Kultivierung der Tugen-den zu erreichen ist, handelt es sich laut Settegast bei personaler Identität letztlich nicht um eine Tatsache, die einfach vorliegt oder nicht, sondern um eine Aufgabe, die uns als Menschen gegeben ist und wesentlich darin besteht, in bewusster Orientierung auf das gute Leben hin ein stabiles, sich zeitlich durchhaltendes Selbst allererst auszubilden. (shrink)

David Lewis defends the following "non-circular definition of personhood": "something is a continuant person if and only if it is a maximal R-interrelated aggregate of person-stages. That is: if and only if it is an aggregate of person-stages, each of which is R-related to all the rest (and to itself), and it is a proper part of no other such aggregate." I give a counterexample, involving a person who is a part of another, much larger person, with a separate mental (...) life. I then offer an easy repair, which preserves the virtues of Lewis's definition without introducing any new vices. (shrink)

In “The Argument for Subject Body Dualism from Transtemporal Identity Defended” (PPR 2013), Martine Nida-Rümelin (NR) responded to my (PPR 2013) criticism of her (2010) argument for subject-body dualism. The crucial premise of her (2010) argument was that there is a factual difference between the claims that in a fission case the original person is identical with one, or the other, of the successors. I argued that, on the three most plausible interpretations of ‘factual difference’, the argument fails. NR responds (...) that I missed the intended, fourth interpretation, and that, in any case, with an additional assumption, the argument on the third interpretation goes through. I argue that the fourth interpretation, while insufficient as stated, reveals an assumption that provides an independent argument, namely, that in first person thought about future properties we have a positive conception of the self that rules out having empirical criteria of transtemporal identity. I argue that the considerations offered for this thesis fail to establish it, and that we do not bring ourselves under any positive conception in first person thought. I argue also that on the third interpretation, the first premise of the argument is inconsistent with the necessity of identity. (shrink)

If a person, A, branches into B and C, then it is widely held that B and C are not identical to one another. Many think that this is because B and C have contradictory properties at the same time. In this paper, I show why this explanation cannot be right. I argue that contradictory properties at times are not necessary for non-identity between descendants, and that contradictory properties at times are not sufficient for non-identity. I also argue that the (...) standard explanation cannot be salvaged by a shift to personal time. Appeals to a lack of continuity, or to the absence of unity of consciousness likewise fail. Rather, B and C are non-identical simply because A branched into B and C. Why branching should be problematic for personal identity remains a deep puzzle though I offer some tentative suggestions. (shrink)

If we are physical things with parts, then accounts of what we are and accounts of when composition occurs have important implications for one another. Defenders of restricted composition tend to endorse a sparse ontology in taking an eliminativist stance toward composite objects that are not organisms, while claiming that we are organisms. However, these arguments do not entail that we are organisms, for they rely on the premise that we are organisms. Thus, sparsist reasoning need not be paired with (...) animalism, but could instead be paired with other accounts according to which we are composites. The embodied mind account—a version of the brain view—is one such account. Replacing the premise that we are organisms with the premise that we are embodied minds, in arguments that otherwise parallel those supporting animalist sparsism, yields an account according to which composite objects include thinkers, but perhaps nothing else. Since animalism has implausible implications about scenarios which are handled better by the embodied mind account, this approach is preferable to animalist sparsism. Furthermore, the role of mental features in sparsism makes embodied mind sparsism the more reasonable conclusion. Meanwhile, adopting sparsism allows the embodied mind account to dodge objections that may not be as easily avoided by it or other versions of the brain view if not paired with sparsism. These include objections about brains that are not persons, inorganic part replacement, and another form of part replacement that might seem to allow one to get a new brain. (shrink)

Pummer : 43–77, 2014) ingeniously wraps together issues from the personal identity literature with issues from the literature on desert. However, I wish to take issue with the main conclusion that he draws, namely, that we need to rethink the following principle: Desert.: When people culpably do very wrong or bad acts, they deserve punishment in the following sense: at least other things being equal they ought to be made worse off, simply in virtue of the fact that they culpably (...) did wrong—even if they have repented, are now virtuous, and punishing them would benefit no one. :43–77, 2014: 43–44) Pummer offers an argument that is intended to show that this principle, along with widely-held views about personal identity, entails an inconsistent triad of propositions. I agree. But I think Pummer's argument attacks a straw man. I believe that no-one holds Desert, at least as it is stated, and that once the principle is stated correctly it is easy to see that no inconsistent triad follows from it. So, Desert does not need rethinking. It just needs to be stated correctly. (shrink)

I respond to David Shoemaker's arguments for the conclusion that personal identity is irrelevant for death. I contend that we can accept Shoemaker's claim that loss of personal identity is not sufficient for death while nonetheless maintaining that there is an important theoretical relationship between death and personal identity. I argue that this relationship is also of practical importance for physicians' decisions about organ reallocation.

Lynne Baker's concept of a first-person perspective is not as clear and straightforward as it might seem at first glance. There is a discrepancy between her argumentation that we have first-person perspectives and some characteristics she takes first-person perspectives to have, namely, that the instances of this capacity necessarily persist through time and are indivisible and unduplicable. Moreover, these characteristics cause serious problems concerning personal identity.

It seems plausible that (i) how much punishment a person deserves cannot be affected by the mere existence or nonexistence of another person. We might have also thought that (ii) how much punishment is deserved cannot increase merely in virtue of personal division. I argue that (i) and (ii) are inconsistent with the popular belief that, other things being equal, when people culpably do very wrong or bad acts, they ought to be punished for this—even if they have repented, are (...) now virtuous, and punishing them would benefit no one. Insofar as we cannot deny (i), we are either forced to abandon the popular belief in desert, or else allow that personal division could, as I put it, “multiply desert.” Some may not find the latter, considered by itself, troubling. But I argue that the thesis that division multiplies desert faces a potentially serious problem, which arises in the context of personal fusion. It is difficult to see how to maintain a particular family of desert views in light of the cases here presented. (shrink)

In some quarters, it is held that Anscombe proved that a zygote is not a human being on the basis of an argument involving the possibility of identical twins, but there is surprisingly little agreement on what her argument is supposed to be. I criticize several extant interpretations, both as interpretations of Anscombe and as self-standing arguments, and offer a different understanding of her conclusion on which the non-specificity of creation processes and their goals is at issue.

Können wir als Personen irreversible Gedächtnisverluste überleben? Wie steht es mit Teletransportationen? Wie mit jahrelangem Einfrieren? Fragen wie diese sind weit davon entfernt, bloße Denksportaufgaben für Science-Fiction-Fans zu sein. Vielmehr verraten uns Antworten darauf, welche unserer Eigenschaften uns wirklich wichtig sind und was unser Wesen ausmacht. -/- Unglücklicherweise beantworten Vertreter unterschiedlicher Theorien personaler Identität diese Fragen auf völlig verschiedene Weise. Manche schöpfen die Plausibilität ihrer Positionen aus phantasievollen Gedankenexperimenten; anderen sind dieselben Gedankenexperimente für eine ernsthafte Einbeziehung in die philosophische Theoriebildung (...) schlicht zu wirklichkeitsfern. Es überrascht daher kaum, dass jene Anhänger unterschiedlicher Theorien einander oft wenig zu sagen haben. Im ersten Teil des Buches wird untersucht, unter welchen Umständen Gedankenexperimente aussagekräftige philosophische Werkzeuge sind. Auf der Basis dieser Analyse werden die diversen zeitgenössischen Theorien personaler Identität dann im zweiten Teil einer Neubewertung unterzogen – nicht ohne dass dabei mit vielen selbstverständlich erscheinenden Überzeugungen aufgeräumt wird. (shrink)

According to Principles of Sufficient Reason, every truth (in some relevant group) has an explanation. One of the most popular defenses of Principles of Sufficient Reason has been the presupposition of reason defense, which takes endorsement of the defended PSR to play a crucial role in our theory selection. According to recent presentations of this defense, our method of theory selection often depends on the assumption that, if a given proposition is true, then it has an explanation, and this will (...) only be justified if we think this holds for all propositions in the relevant group. I argue that this argument fails even when restricted to contingent propositions, and even if we grant that there is no non-arbitrary way to divide true propositions that have explanations from those that lack them. Further, we can give an alternate explanation of what justifies our selecting theories on the basis of explanatory features: the crucial role is not played by an endorsement of a PSR, but rather by our belief that, prima facie, we should prefer theories that exemplify explanatory power to greater degrees than their rivals. This guides our theory selection in a manner similar to ontological parsimony and theoretical simplicity. Unlike a PSR, our belief about explanatory power gives us a prima facie guiding principle, which provides justification in the cases where we think we have it, and not in the cases where we think we don't. (shrink)

Martine Nida-Rümelin has argued recently for subject-body dualism on the basis of reflections on the possibility of survival in fission cases from the literature on personal identity. The argument focuses on the claim that there is a factual difference between the claims that one or the other of two equally good continuers of a person in a fission case is identical with her. I consider three interpretations of the notion of a factual difference that the argument employs, and I argue (...) that on each of them the argument either begs the question or is unsound. (shrink)

What happens to a person in a case of fission? Does it survive? Does it go out of existence? Or is the outcome indeterminate? Since each description of fission based on the persistence conditions associated with our ordinary concept of a person seems to clash with one or more platitudes of common sense about the spatiotemporal profile of macroscopic objects, fission threatens the common-sense conception of persons with inconsistency. Standard responses to this paradox agree that the common-sense conception of persons (...) is unstable, differing over which part of the conception requires revision. I will show that this entrenched view of fission is not compulsory. I will develop a solution to the paradox that maintains the consistency of the common-sense conception of persons on the basis of an ontology of persons and other ordinary objects as double-layered compounds. Each of various descriptions of the outcome of personal fission is compatible with principles about the spatiotemporal profile of persons, because the descriptions and the principles manifest different perspectives on persons and are made true or false by different ontological components of the latter. What holds for the fission of persons, holds for the fission of other kinds of objects. (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)

Brain bisection raises the intriguing question about how many minds the split-brain patients have. Thomas Nagel and Derek Parfit, who have brought this question into consideration, come to similar conclusions in response to it. They both argue that the question has no answer, that there simply isn’t any countable number of minds that the split-brain patients have. In addition, Parfit argues that the split-brain cases can be adequately described only if we adopt a certain particular view about the metaphysical nature (...) of a person. The goal of this paper is to clarify both of those views and, in particular, to explain why Parfit’s preference for one model of personhood does not determine how many persons survive brain bisection. (shrink)

According to Sider’s stage theory a subject about to undergo personal fission should expect to experience each outcome simultaneously as distinct persons. How is the subject to make sense of this ? I argue that their most paradigmatically self-interested future-directed behaviour, betting for personal gain, ought to be exactly the same as in equivalent games of chance where the possible outcomes correspond to the fission output branches. So this novel form of expectancy, albeit strange, can be a reliable guide to (...) action. (shrink)

Some analyses of personal fission suggest that an informed subject should expect to have a distinct experience of each outcome simultaneously. Is rational provision for the future possible in such unfamiliar circumstances? I argue that, with some qualification, the subject can reasonably act as if faced with alternative possible outcomes with precise probabilities rather than multiple actual outcomes.

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)

(No abstract is available for this citation).

Some philosophers have argued that so long as two neural events, within a subject, are both of the same type and both carry the same content, then these events may jointly constitute a single mental token, regardless of the sort of causal relation to each other that they bear. These philosophers have used this claim—which I call the “singularity-through-redundancy” position—in order to argue that a split-brain subject normally has a single stream of consciousness, disjunctively realized across the two hemispheres. This (...) paper argues, against this position, that the kind of causal relations multiple neural events bear to each other constrains the mental tokens with which functionalists who are realists can identify them. (shrink)

Most versions of the psychological-continuity approach to personal identity (PCA) contain a 'non-branching' requirement. Recently, Robert Francescotti has argued that while such versions of PCA handle Parfit's standard fission case well, they deliver the wrong result in the case of an intact human brain. To solve this problem, he says, PCA-adherents need to add a clause that runs contrary to the spirit of their theory. In this response, I argue that Francescotti's counterexample fails. As a result, the revision he suggests (...) is not needed. (shrink)

In this paper I will provide a hylomorphic critique of Jeff McMahan’s “An Alternative to Brain Death.” I will evaluate three puzzles—the dicephalus, the braintransplant, and the split-brain phenomenon—proposed by McMahan which allow him to deny that a human being is identical to an organism. I will contend thatMcMahan’s solution entails counterintuitive consequences that pose problems to organ transplant cases. A Thomistic hylomorphic metaphysics not only avoids these unwelcome consequences and provides solutions to the three puzzles but in doing so (...) allows for an alternative definition of death. Since McMahan has constructed his definition of death around his own metaphysics, alternative metaphysics, in this case a hylomorphic metaphysics, allow for an alternative definition of death. (shrink)

When one considers one's own persistence over time from the first-person perspective, it seems as if facts about one's persistence are "further facts," over and above facts about physical and psychological continuity. But the idea that facts about one's persistence are further facts is objectionable on independent theoretical grounds: it conflicts with physicalism and requires us to posit hidden facts about our persistence. This essay shows how to resolve this conflict using the idea that imagining from the first-person point of (...) view is a guide to centered possibility , a type of possibility analyzed in terms of centered worlds. CiteULike Connotea Del.icio.us Digg Reddit Technorati What's this? (shrink)

This paper concerns the relationships between persons, brains, behaviour, and psychological explanation. Tye defines a ‘psychological framework’ (PF) as a set of token beliefs, desires, intentions, memories, streams of consciousness, higher-order mental states, etc., that ‘form a coherent whole’ and against which a creature’s ‘behavior can be explained’ (p. 141). A person is the subject of such a psychological framework. Each person has one PF, and with each new PF there is a new person. Meanwhile materialism tells us, according to (...) Tye, that brains are the bearers of mental states. In other words, ‘each person is a brain’ (p. 142) — or rather a ‘global physical state of the brain,’ since Tye believes that a single brain might realize multiple PFs and thus constitute multiple persons. Most of this paper simply assumes Tye’s account of personal identity, in order to expose certain contradictions within what Tye says about personhood in split-brain subjects. Towards the end of the paper, however, I turn to alternative accounts of persons. While a method of individuating persons grounded in scientific psychology would identify persons with psychological frameworks, as Tye does, perhaps an account of personhood grounded either in a non-psychological science, or in non-scientific psychology, would better fit the interests we have in personal identity. (shrink)

Tyler Burge argues on the basis of an account of memory that the notion of quasimemory cannot be used to answer the circularity objection to psychological accounts of personal identity. His account implies the impossibility of the "Parfit people," creatures psychologically like us who undergo amoeba-like fission at the age of twenty-one, with only one offshoot allowed to survive, and who have "quareers," made up of the career of the original person and the career of the sole survivor, that exhibit (...) the same sort of psychological continuity that characterizes normal human careers, and are such that epistemic warrant is preserved across the episodes of fission and often involves quasimemories that are not memories. But what he says about memory does not support the denial that such creatures are possible. Where he thinks de se attitudes are necessary, de se * attitudes, indexed to quareers instead of to careers, would serve equally well. It is further argued that the circularity objection to psychological accounts can be answered without appeal to the notion of quasi-memory. Because of the internal relations between the causal profiles of mental states and the persistence conditions of their possessors, in principle there can be a "package deal" definition that simultaneously defines both. (shrink)

According to conventional wisdom, the split-brain syndrome puts paid to the thesis that consciousness is necessarily unified. The aim of this paper is to challenge that view. I argue both that disunity models of the split-brain are highly problematic, and that there is much to recommend a model of the split-brain—the switch model—according to which split-brain patients retain a fully unified consciousness at all times. Although the task of examining the unity of consciousness through the lens of the split-brain syndrome (...) is not a new one—such projects date back to Nagel’s seminal paper on the topic—the time is ripe for a re-evaluation of the issues. (shrink)

ABSTRACT We begin by discussing some logical constraints on the psychological approach to personal identity. We consider a problem for the psychological approach that arises in fission cases. The problem engenders the need for a non-branching clause in a psychological account of the co-personality relation. We look at some difficulties in formulating such a clause. We end by rejecting a recently proposed formulation of non-branching. Our criticism of the formulation raises some interesting questions about the individuation of person stages.

Abstract: Those who endorse the Psychological Continuity Approach (PCA) to analyzing personal identity need to impose a non-branching constraint to get the intuitively correct result that in the case of fission, one person becomes two. With the help of Brueckner's (2005) discussion, it is shown here that the sort of non-branching clause that allows proponents of PCA to provide sufficient conditions for being the same person actually runs contrary to the very spirit of their theory. The problem is first presented (...) in connection with perdurantist versions of PCA. The difficulty is then shown to apply to endurantist versions as well. -/- . (shrink)

Hylomorphism offers a third way between animalist approaches to personal identity, which maintain that psychology is irrelevant to our persistence, andneo-Lockean accounts, which deny that humans are animals. This paper provides a Thomistic account that explains the intuitive responses to thought experiments involving brain transplants and the transformation of organic bodies into inorganic ones. This account does not have to follow the animalist in abandoning the claim that it is our identity which matters in survival, or countenance the puzzles of (...) spatially coincident entities that plague the neo-Lockean. The key is to understand the human being as only contingently an animal. This approach to our animality is one that Catholics have additional reason to hold given certain views about purgatory, our uniqueness as free and rational creatures, and our having once existed as zygotes. (shrink)

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)

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)

A reply to a comment by Paul Tappenden (BJPS 59 (2008) pp. 307-314) on S. Saunders and D. Wallace, "Branching and Uncertainty" (BJPS 59 (2008) pp. 298-306).

Contemporary philosophers writing on the issue of personal identity agree that, whatever is disputable about fission cases, there is little doubt that, if there could be fission, there would be psychological continuity between the original person and her offshoot (if the branching is one-one), or between the original personand her offshoots (if the branching is one-many). The belief is one with a long history dating back to John Locke; it has, over time, acquired the status of self-evident truth. This paper (...) is not an attempt to refute this deeply rooted belief, though I think the near universal acceptance of it is rather unfortunate. My main goal in what follows is to make an initial case for three forms of psychological discontinuity that I believe would exist between the fission ancestor and the offshoots. If I am right about the existence of the three forms of psychological discontinuity, contemporary Lockeans on the issue of personal identity will need to rethink their position, or so I will argue in the last section of the paper. (shrink)

Most contributors to the debate about brain death, including Dr. James Bernat, share certain assumptions. They believe that the concept of death is univocal, that death is a biological phenomenon, that it is necessarily irreversible, that it is paradigmatically something that happens to organisms, that we are human organisms, and therefore that our deaths will be deaths of organisms. These claims are supposed to have moral significance. It is, for example, only when a person dies that it is permissible to (...) extract her organs for transplantation.It is also commonly held that our univocal notion of death is the permanent cessation of integrated functioning in an organism and that the criterion for determining when this has occurred in animals with brains is the death of the brain as a whole – that is, brain death. The reason most commonly given for this is that the brain is the irreplaceable master control of the organism's integration. (shrink)

One problem that has formed the focus of much recent discussion on personal identity is the Fission Problem. The aim of this paper is to offer a novel solution to this problem.

Derek Parfit's “reductionist” account of personal identity (including the rejection of anything like a soul) is coupled with the rejection of a commonsensical intuition of essential self-unity, as in his defense of the counter-intuitive claim that “identity does not matter.” His argument for this claim is based on reflection on the possibility of personal fission. To the contrary, Simon Blackburn claims that the “unity reaction” to fission has an absolute grip on practical reasoning. Now David Lewis denied Parfit's claim that (...) reductionism contravenes common sense, so I revisit the debate between Parfit and Lewis, showing why Parfit wins it. Is reductionism about persons then inherently at odds with the unity reaction? Not necessarily; David Velleman presents a reductionist theory according to which fission does not conflict with the unity reaction. Nonetheless, relying on the distinction between person level descriptions of first-person states and the first-person perspective itself, I argue that Velleman's theory does not eliminate fission-based conflict with the unity reaction. Footnotesa * Earlier versions of this paper were presented at the philosophy departments at Rutgers University and Bowling Green State University. I am indebted to many members of these audiences, and to the other contributors to this volume, for their comments—especially Frank Arntzenius, Michael Bradie, David Copp, John Finnis, Jerry Fodor, Brian Loar, Barry Loewer, Colin McGinn, Fred Miller, Mark Moyer, David Oderberg, Marya Schechtman, David Schmidtz, David Sobel, and Sara Worley. Special thanks to David Sanford. I am also grateful to graduate students in my seminar at Bowling Green during the spring of 2003, for urging me to take seriously the grip of the unity reaction; I am especially grateful for the comments of Nico Maloberti, Jonathan Miller, John Milliken, Robyn Peabody, Jennifer Sproul, Jessica Teaman, and Sherisse Webb. (shrink)

In this introduction to the special issue of Theoretical Medicine and Bioethics on the topic of personal identity and bioethics, I provide a background for the topic and then discuss the contributions in the special issue by Eric Olson, Marya Schechtman, Tim Campbell and Jeff McMahan, James Delaney and David Hershenov, and David DeGrazia.