Consider the conscious states of a single subject at a time. Arguably, split-brain cases show that such states need not be jointly accessible. It is less clear that these cases also show that such states need not be jointly experienced. Michael Tye (2004) argues split-brain cases do have that implication, and Timothy Bayne and David Chalmers (2003) argue that they do not. I will develop two objections to Tye’s arguments. First, an analogy to blindsight on which he relies is questionable. (...) Second, even if his analogy succeeds, it shows only that a single person can simultaneously have two separate sets of phenomenally conscious mental states. That result fails to undermine the phenomenalunity thesis that Bayne and Chalmers defend, on which phenomenal consciousness is necessarily unified. (shrink)

This paper challenges the widely held theory that split-brain patients have ‘two-minds’ and can thus be described as being two distinct persons. A distinction is made between the singularity of mind and the coherence of mind. It is stressed that ‘a single mind’ is not something posited to explain coherence among mental contents, but is merely a mark that such coherence holds to a certain degree. However, there is no sharp dividing line regarding what counts as a single mind. It (...) is argued that mental coherence is always a matter of degree, and that our concept of a single mind can accomodate spit-brain phenomena. (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)

The article questions the assumption that conjoined twins are necessarily two people or persons by employing arguments based on different points of view: non-personal vitalism, the person as a sentient being, the person as an agent, the person as a locus of narrative and valuation, and the person as an embodied mind. Analogies employed from the cases of amputation, multiple personality disorder, abortion, split-brain patients and cloning. The article further questions the assumption that a conjoined twin's natural interest and wish (...) is separation. I first contend that separation is such a radical procedure as to render the post-separation person different from the pre-separation one. Therefore, it is not possible to benefit the pre-separation twin by the act of separation. The article concludes with a critical evaluation of the tendency in bioethics to regard ethical challenges as rivalry between individuals competing for scarce resources. (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)

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)

Most philosophers in the analytical philosophy answer the question what personal identity is in psychological terms. Arguments for substantiating this view are mainly based on thought experiments of brain transfer cases and the like in which persons change brains. However, in these thought experiments the remaining part of the body plays only a passive part. In this paper I argue that the psychological approach of personal identity cannot be maintained, if the whole body is actively involved in the analysis, and (...) that the body is an intrinsic part of what I am as a person. (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.RÉSUMÉ: Ce (...) travail traite d'abord de certaines contraintes logiques concernant l'usage de l'approche psychologique pour définir l'identité personnelle. Nous y examinons un problème touchant l'approche psychologique dans les cas de fission. Ce problème exige l'intervention d'une clause qui nie tout recours au branchement dans l'examen de la relation de co-personnalité. Nous avons rencontré certaines difficultés dans la formulation d'une teile clause. Pour conclure, nous rejetons uneformulation récente du non-branchement. Notre objection à cette formulation soulève quelques questions intéressantes concernant l'individuation de stades temporels personnels. (shrink)

Parfit’s well known book, Reasons and Persons, argues, among other things, that ‘what matters’ in regard to ‘survival’ is not personal identity but something he calls ‘relation R.’ On this basis, plus other considerations, he rejects the ‘Self-interest’ theory as to what should be our aim in life. Here I show, or try to show, that his over-all argument is seriously defective. In particular, he fails to prove that personal identity is not what matters for survival.

The Kinds of Things strongly supports the commonsense belief that in normal human life even changes in our deeply-held affections and ideals do not erode the ...

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)

Through careful analysis of a specific example, Parfit’s ‘fission argument’ for the unimportance of personal identity, I argue that our judgements concerning imaginary scenarios are likely to be unreliable when the scenarios involve disruptions of certain contingent correlations. Parfit’s argument depends on our hypothesizing away a number of facts which play a central role in our understanding and employment of the very concept under investigation; as a result, it fails to establish what Parfit claims, namely, that identity is not what (...) matters. I argue that Parfit’s conclusion can be blocked without denying that he has presented an imaginary case where prudential concern would be rational in the absence of identity. My analysis depends on the recognition that the features that explain or justify a relation may be distinct from the features that underpin it as necessary conditions. (shrink)

In this paper it is argued that the experimental data on commissurotomy patients provide no grounds for denying the singular personhood of commissurotomy patients. This is because, contrary to most philosophical accounts, there is no “unity of consciousness” discriminating condition for singular personhood that is violated in the case of commissurotomy patients, and because no contradictions arise when singular personhood is ascribed to commissurotomy patients.

Closest-continuer or best-candidate accounts of persistence seem deeply unsatisfactory, but it’s hard to say why. The standard criticism is that such accounts violate the ‘only a and b’ rule, but this criticism merely highlights a feature of the accounts without explaining why the feature is unacceptable. Another concern is that such accounts violate some principle about the supervenience of persistence facts upon local or intrinsic facts. But, again, we do not seem to have an independent justification for this supervenience claim. (...) Instead, I argue that closest continuer accounts are committed to unexplained correlations between distinct existences, and that this is their fundamental flaw. We can have independent justification for rejecting such correlations, but what the justification is depends upon much broader issues in ontology. There is no one-size-fits all objection to closest-continuer accounts of persistence. (shrink)

Hylomorphism offers a third way between animalist approaches to personal identity that maintain psychology is irrelevant to our persistence and neo-Lockean accounts that deny we are animals. A Thomistic-inspired account is provided that explains the intuitive responses to thought experiments involving brain transplants and the transformation of organic bodies into inorganic ones without having to follow the animalist in abandoning the claim that it is our identity that matters in survival nor 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 neural substrates of context effects in word perception are still largely unclear. Interhemispheric priming phenomena in word recognition, typically observed in normal subjects, are absent in commissurotomized patients. This suggests that callosal fibers may provide contextual integration. In addition, certain characteristics of human frontal cortical fields subserving sensorimotor learning, as investigated by positron emission tomography, provide evidence for contextual integration not confined to the visual system. This supports the notion of common aspects of cortical computations in different cerebral areas.

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)

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)

Many have claimed that split-brain patients are actually two persons. I maintain that both the traditional separation argument and the more recent sophistication argument for the two persons interpretation are inadequate on conceptual grounds. An autonomy argument is inadequate on empirical grounds. Overall, theoretical and practical consequences weigh heavily in favor of adopting a one person interpretation.

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)

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)

We investigated binocular rivalry in the twocerebral hemispheres of callosotomized(split-brain) observers. We found that rivalryoccurs for complex stimuli in split-brainobservers, and that it is similar in the twohemispheres. This poses difficulties for twotheories of rivalry: (1) that rivalry occursbecause of switching of activity between thetwo hemispheres, and (2) that rivalry iscontrolled by a structure in the rightfrontoparietal cortex. Instead, similar rivalryfrom the two hemispheres is consistent with atheory that its mechanism is low in the visualsystem, at which each hemisphere conducts (...) asimilar analysis of its half of visual space. (shrink)

Sydney Shoemaker argues that the functionalist theory of mind entails a psychological-continuity view of personal identity, as well as providing a defense of that view against a crucial objection. I show that his view has surprising consequences, e.g. that no organism could have mental properties and that a thing's mental properties fail to supervene even weakly on its microstructure and surroundings. I then argue that the view founders on "fission" cases and rules out our being material things. Functionalism tells us (...) little if anything about personal identity. (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)

In "Consciousness Explained," Dennett (1991) denies that split-brain humans have double consciousness: he describes the experiments as "anecdotal." In attempting to replace the Cartesian Theatre of the Mind" with his own "Multiple Drafts" view of consciousness, Dennett rejects the notion of the mind as a countable thing in favour of its being a mere "abstraction." His criticisms of the standard interpretation of the split-brain data are analyzed here and each is found to be open to objections. There exist people who (...) have survived left ["dominant"] cerebral hemispherectomy; by Dennett's criteria, they would not have minds. (shrink)

(No abstract is available for this citation).

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)

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. (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).

Contra Derek Parfit’s psychological continuity theory, I argue for an externalist conception of what matters in the survival of persons over time. Specifically, I claim that what matters in the survival of persons is the continuation of what I call their “life trajectories.” This condition on the quasi-continuation of the diachronic identity of persons comes from considering the implications of what certain kinds of cases of “complete virtual immersion”-- the immersion of a psychological subject in a completely virtual world, a (...) world in which experiences are de-correlated with events in the objective world. This hypothesis results in some fairly strong conditions on the synchronic identity of persons, conditions that demonstrate that psychological continuity over time is insufficient for having what matters in survival. Of course, the idea that externalist constraints are important in a complete account of what is metaphysically necessary for maintaining persons and what matters in their survival is not new, but I propose my own specific theory about how to understand these constraints. What’s more, I explain in detail why incorporating externalist constraints in an account of what matters in survival proves to rule out fission as a case in which we have what matters equally as much as we do in single case, and unlike the traditional way of rejecting these cases, I do so without requiring a commitment to an identity theory of what matters. The view I offer can also explain our reactions to different virtual immersion scenarios. Therefore, simply on explanatory grounds alone, my view is to be preferred over pure psychological continuity theories. (shrink)

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)

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)

Parfit’s Branch Line argument is intended to show that the relation of survival is possibly a one-many relation and thus different from numerical identity. I offer a detailed reconstruction of Parfit’s notions of survival and personal identity, and show the argument cannot be coherently formulated within Parfit’s own setting. More specifically, I argue that Parfit’s own specifications imply that the “R-relation”, i.e., the relation claimed to capture of “what matters in survival,” turns out to hold not only along but also (...) across the branches representing the development of a reduplicated person. This curious fact of ‘interbranch survival,’ as I call it, has gone unnoticed so far. The fact that the R-relation also holds across branches creates a trilemma for Parfit’s approach. Either the envisaged notion of personal identity is circular, or the R-relation fails as a reconstruction of the common sense notion of survival, or talk about persons ‘branching’ (being reduplicated etc.) remains semantically empty. In the paper’s last section I suggest that my criticism does not detract from the larger systematic significance of Parfit’s argument. The argument is simply terminologically miscalibrated. Even though Parfit’s branch line argument fails to establish the conceptual separability of survival and identity, it can be used to show the separability of sameness and numerical identity, which should have similar implications for meta-ethics as the original argument. (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)

Many theories of personal identity allow for the metaphysical possibility of fission. In 1981 Nozick proposed a theory of personal identity called ‘the closest continuer view’ (CCV) that denies fission in the case of persons but allows fisson in the case of human beings. CCV may thus appear to reduce ‘person’ to a nonmetaphysical, practical notion. Against this I argue that CCV is an externalist metaphysical theory that purports to solve a problem that is insurmountable within the confines of an (...) internalist metaphysics of personal identity. (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.

Conc 2: Charitable reconstructions are available. Conc 3: But these lead to worrying results. (POM) Conc 4: Further weakening prevents it from playing the “survival is intrinsic” role in fission arguments.

Most views of personal identity allow that sometimes, facts of personal identity can be borderline or indeterminate. Bernard Williams argued that regarding questions of one’s own survival as borderline “had no comprehensible representation” in one’s emotions and expectations. Whether this is the case, I will argue, depends crucially on what account of indeterminacy is presupposed.

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.

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)