Fission and Split Brains

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.

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)

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.

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)

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.

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)

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)

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)

This is a critical review of Raymond Martin's 'Self-Concern' (1998), focusing especially on his criticism of Parfit's use of fission thought-experiments and his own 'fission rejuvenation' thought-experiment.

Thought-experiments in which one person divides into two have been important in the literature on personal identity. I consider three influential arguments which aim to undermine the force of these thought-experiments – arguments from David Wiggins, Patricia Kitcher and Kathleen Wilkes. I argue that all three fail, leaving us to face the consequences of splitting, whatever those may be.

I consider, and rebut, the argument from "twinning" - that zygotes can't be considered human individuals as two or more such individuals could be (sometimes are) produced from one zygote.

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.

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)

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)

Disagreements about the criteria for personal identity are usually discussed by means of thought experiments, which describe counterfactual science fiction situations, in order to test the explanatory force of the different accounts. In this paper the basic analyzes of the survival of persons through time are presented and the higher plausibility of psychological criteria to solve the puzzle cases is stressed. I argue that because of their capability to account for fission and fusion cases psychological criteria rooted in a four-dimensionalist (...) framework are in a more advantageous position than those grounded on a continuants ontology. (shrink)

This paper defends Parfit's "theoretical" view of personal identity against Christine Korsgaard's objections grounded in practical identity.

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)

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.

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)

This article criticizes a range of assumptions that proponents of brain death usually share. It argues that one of the main contentions made in defense of brain death – that the brain is necessary for integrated functioning in a human organism – is mistaken. It then sketches an alternative account of human death that distinguishes between the biological death of a human organism and the death or ceasing to exist of a person.

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)

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)

Imagine that you and a duplicate of yourself are lying unconscious, next to each other, about to undergo a complete step-by-step exchange of bits of your bodies. It certainly seems that at no stage in this exchange of bits will you have thereby switched places with your duplicate. Yet it also seems that the end-result, with all the bits exchanged, will be essentially that of the two of you having switched places. Where will you awaken? I claim that one and (...) the same person possesses both bodies, occupies both places and will experience both awakenings, just as a person whose brain has been bisected must at once experience both of the unconnected fields of awareness, even though each of these will falsely appear to him as the entirety of his experience. I also claim that the more usual apparent boundaries of persons are as illusory as those in brain bisection; personal identity remains unchanged through any variation or multiplication of body or mind. In all conscious life there is only one person - I - whose existence depends merely on the presence of a quality that is inherent in all experience - its quality of being mine, the simple immediacy of it for whatever is having experience. One powerful argument for this is statistical: on the ordinary view of personhood it is an incredible coincidence for you (though not for others) that out of 200,000,000 sperm cells the very one required on each occasion for your future existence was first to the egg in each of the begettings of yourself and all your ancestors. The only view that does not make your existence incredible, and that is not therefore (from your perspective) an incredible view, is that any conscious being would necessarily have been you anyway. It is a consequence that self-interest should extend to all conscious organisms. (shrink)

Recent work in personal identity has emphasized the importance of various conventions, or ‘person-directed practices’ in the determination of personal identity. An interesting question arises as to whether we should think that there are any entities that have, in some interesting sense, conventional identity conditions. We think that the best way to understand such work about practices and conventions is the strongest and most radical. If these considerations are correct, persons are, on our view, conventional constructs: they are in part (...) constituted by certain conventions. A person exists only if the relevant conventions exist. A person will be a conscious being of a certain kind combined with a set of conventions. Some of those conventions are encoded in the being itself, so requiring the conventions to exist is requiring the conscious being to be organized in a particular way. In most cases the conventions in question are settled. There is no dispute about what the conventions are, and thus no dispute about which events a person can survive. These are cases where we take the conventions so much for granted, that it is easy to forget that they are there, and that they are necessary constituents of persons. Sometimes though, conventions are not settled. Sometimes there is a dispute about what the conventions should be, and thus a dispute about what events a person can survive. These are the traditional puzzle cases of personal identity. That it appears that conventions play a part in determining persons’ persistence conditions only in these puzzle cases is explained by the fact that only in these cases are the conventions unsettled. Settled or not though, conventions are necessary constituents of persons. (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.

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)

It is generally thought that there are certain persons to whose welfare we should give special weight. It is commonly held, for example, that we should give special weight to our own welfare. On the strongest version of this view, we should always give overriding weight to our own welfare, and so, in considering any set of alternatives, we should always prefer the one in which we fare best. Many people would reject this strong view, for two reasons. First, many (...) people would hold that impersonal reasons (such as reasons of total utility) can sometimes outweigh, or at least counterbalance, reasons of self-interest. Further, many people think that reasons deriving from special personal relations can sometimes outweigh, or at least counterbalance, reasons of self-interest. We can, however, formulate a much weaker, and much more plausible, version of the self-interest view that avoids both these problems. Let’s first define a person’s kin as anyone in the person’s extended family (including himself). And let’s define a person’s kith very broadly as anyone with whom that person has ever interacted. We can now formulate the weak version of the self-interest view as follows. (shrink)

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)

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)

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)

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)

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)

. Cognitive science challenges our understandings of self and freedom. In this article, adapted from a chapter in Minding God: Theology and the Cognitive Sciences , I review some of the scientific literature with regard to issues of self and freedom. I argue that our sense of self is a construct and heavily dependent on the kind of brain that we have. Furthermore, understanding the issue of freedom requires an understanding of the findings of cognitive science. Human beings are constrained (...) to be free; our biology in no small way determines the kinds of freedom that we are able to have. (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’ 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)

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)

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.