Fetal reduction is the practice of reducing the number of fetuses in a multiple pregnancy, such as quadruplets, to a twin or singleton pregnancy. Use of assisted reproductive technologies increases the likelihood of multiple pregnancies, and many fetal reductions are done after in vitro fertilisation and embryo transfer, either because of social or health-related reasons. In this paper, I apply Joe Horton’s all or nothing problem to the ethics of fetal reduction in the case of a twin pregnancy. I argue (...) that in the case of a twin pregnancy, there are two intuitively plausible claims: abortion is morally permissible, and it is morally wrong to abort just one of the fetuses. But since we should choose morally permissible acts rather than impermissible ones, the two claims lead to another highly implausible claim: the woman ought to abort both fetuses rather than only one. Yet, this does not seem right. A plausible moral theory cannot advocate such a pro-death view. Or can it? I suggest ways to solve this problem and draw implications for each solution. There are no data in this work. (shrink)

In dicephalus conjoined twinning, it appears that two heads share a body; in cephalopagus, it appears that two bodies share a head. How many human animals are present in these cases? One answer is that there are two in both cases—conjoined twins are precisely that, conjoined twins. Another is that the number of humans corresponds to the number of bodies—so there is one in dicephalus and two in cephalopagus. I show that both of these answers are incorrect. Prominent (...) accounts of biological individuation, which treat the organism as an integrated whole, reveal that in these and other cases of conjoined twinning the ‘twins’ share a single human animal. This has a number of consequences for the debate about what we are. First, if animalism is true, individuals of our kind can be—and are—profoundly psychologically divided. Second, cephalopagus twinning does not divide animalism from its rivals, as has been claimed. Finally, animalists can reply to a vicious species of the ‘too many thinkers’ problem to which they are allegedly uniquely vulnerable. (shrink)

We examine the philosophical and ethical issues associated with conjoined twins and their surgical separation. In cases in which there is an extensive sharing of organs, but nevertheless two distinguishable functioning brains, there are a number of philosophical and ethical challenges. This is because such conjoined twins: 1. give rise to puzzles concerning our identity, about whether we are identical to something psychological or biological;2. force us to decide whether what matters from an ethical point of view is (...) the biological life of our organisms or the existence of our consciousness or mind; 3. raise questions concerning when, if ever, it is morally acceptable to sacrifice one of us to save another;4. force us to reflect on the conditions for ownership of organs and the justification of removal of organs for transplantation which causes the death of the donor; 5. raise questions about who should take decisions about life-risking treatments when this cannot be decided by patients themselves.We examine and suggest answers to these questions. (shrink)

We study the foundation of space-time theory in the framework of first-order logic (FOL). Since the foundation of mathematics has been successfully carried through (via set theory) in FOL, it is not entirely impossible to do the same for space-time theory (or relativity). First we recall a simple and streamlined FOL-axiomatization Specrel of special relativity from the literature. Specrel is complete with respect to questions about inertial motion. Then we ask ourselves whether we can prove the usual relativistic properties of (...) accelerated motion (e.g., clocks in acceleration) in Specrel. As it turns out, this is practically equivalent to asking whether Specrel is strong enough to “handle” (or treat) accelerated observers. We show that there is a mathematical principle called induction (IND) coming from real analysis which needs to be added to Specrel in order to handle situations involving relativistic acceleration. We present an extended version AccRel of Specrel which is strong enough to handle accelerated motion, in particular, accelerated observers. Among others, we show that~the Twin Paradox becomes provable in AccRel, but it is not provable without IND. (shrink)

Horgan and Timmons have argued that our intuitions about the semantics of non-moral language and moral language differ, and that while twin-earth semantic intuitions generate one result in Putnam´s twater case, moral twin-earth fails to generate comparable results for moral terms. Horgan and Timmon´s conclude from this that the semantic norms governing the use of natural kind terms differ from the semantic norms governing the use of moral terms. I will argue that Horgan and Timmons’ intuitive moral twin-earth argument fails (...) to derail the new moral realism. Further, I will discuss Boyd’s semantic theory and raise problems for it that do not rely on the use of moral twin-earth. (shrink)

In his paper, ‘Twin pregnancy, fetal reduction and the ‘all or nothing problem’, Räsänen sets out to apply Horton’s ‘all or nothing’ problem to the ethics of multifetal pregnancy reduction from a twin to a singleton pregnancy. Horton’s problem involves the following scenario: imagine that two children are about to be crushed by a collapsing building. An observer would have three options: do nothing, save one child by allowing their arms to be crushed, or save both by allowing their arms (...) to be crushed. Horton offers two intuitively plausible claims: it is morally permissible not to save either child and it is morally impermissible to save only one of the children, which taken together lead to the problematic conclusion that if an observer does not save both children, then it is better to save neither than save only one. Räsänen applies this problem to the case of 2-to-1 MFPR, arguing ultimately that, in cases where there is no medical reason to reduce, the woman ought to bring both fetuses to term. We will argue that Räsänen does not provide adequate support for the claim, crucial to his argument, that aborting only one of the fetuses in a twin pregnancy is wrong, so the ‘all or nothing’ problem does not arise in this context. Furthermore, we argue that the scenario Räsänen presents is highly unrealistic because of the clinical realities of 2-to-1 MFPR, making his argument of limited use for real-life decision making in this area. (shrink)

In explicating his version of the Organism View, Eric Olson argues that you begin to exist only after twinning is no longer possible and that you cannot survive a process of inorganic replacement. Assuming the correctness of the Organism View, but pace Olson, I argue in this paper that the Organism View does not require that you believe either proposition. The claim I shall make about twinning helps to advance a debate that currently divides defenders of the Organism View, while (...) the claim I shall make about inorganic replacement will help to put the Organism View on a par with its rival views by allowing it to accommodate a plausible intuition that its rivals can accommodate, namely, the intuition that you can survive a process of inorganic replacement. Both claims, I shall also argue, are important for those who are interested in the identity condition of a human organism, even if they do not hold the view that you are essentially an organism. (shrink)

A brief account of Putnam's Twin Earth thought experiment and its significance, written for a general audience. Sadly, I can't include Helen De Cruz's drawing of it - check out the beautiful book!

In a recent paper in this journal, McCall and Lowe (2003) argue that an understanding of Special Relativity reveals that the A theorist’s notion of temporal passage is consistent with the B theory of time. They arrive at this conclusion by considering the twins’ paradox, where one of two twins (T) travels to Alpha Centauri and back and upon her return has aged 30 years, while her earth-bound twin (S) has aged 40 years. This paper argues that their (...) account of temporal passage fails to reconcile the A theoretic notion of temporal passage with the B theory of time since the B theorist is at liberty to adopt this as an account of temporal passage as understood by the B theorist. (shrink)

Horgan and Timmons, with their Moral Twin Earth arguments, argue that the new moral realism falls prey to either objectionable relativism or referential indeterminacy. The Moral Twin Earth thought experiment on which the arguments are based relies in crucial ways on the use of intuitions. First, it builds on Putnam’s well-known Twin Earth example and the conclusions drawn from that about the meaning of kind names. Further, it relies on the intuition that were Earthers and Twin Earthers to meet, they (...) would be able to have genuine moral disagreements. I will argue that the similarities with Putnam’s thought experiment are questionable and so the reliance on Putnam-like intuitions is questionable. I will then further argue that even if we accept the intuitions that Horgan and Timmons rely on, the anti-realist conclusion is not warranted due to there being more to the meaning of kind terms than the argument assumes. Once we develop the meaning of kind terms further we can acknowledge both that Earthers and Twin Earthers refer to different properties with their moral terms, and that in spite of that they can have a substantive disagreement due to a shared meaning component. (shrink)

(2002). Missing twins. Philosophy & Geography: Vol. 5, No. 1, pp. 13-17.

A presentation and analysis of the twin-earth thought experiments.

This volume will acquaint novice philosophers with one of the most important debates in twentieth-century philosophy, and will provide seasoned readers with a ...

Robert Stalnaker; XVI*—Twin Earth Revisited, Proceedings of the Aristotelian Society, Volume 93, Issue 1, 1 June 1993, Pages 297–312, https://doi.org/10.1093/ar.

This article explores the elective affinities between Actor-Network Theory (ANT) and the sociology of critical capacities. It argues that these two research programmes can be understood as symmetrical twins. We show the extent to which the exchange between Bruno Latour and Luc Boltanski has influenced their respective theoretical developments. Three strong encounters between the twin research programmes may be distinguished. The first encounter concerns explanations for social change. The second encounter focuses on the status of objects and their relationship (...) to places. The third encounter is about the concept of critique. Drawing on their long-term mutual readings, we gain insight into how pleas for symmetrical analysis raised in response to Bourdieu’s theory of fields have evolved within both ANT and the sociology of critical capacity. We conclude by relating the development of the respective research programmes to the issue of disciplinary boundaries. (shrink)

In this paper I argue against Twin-Earth externalism. The mistake that Twin Earth arguments rest on is the failure to appreciate the force of the following dilemma. Some features of things around us do matter for the purposes of conceptual classification, and others do not. The most plausible way to draw this distinction is to see whether a certain feature enters the cognitive perspective of the experiencing subject in relation to the kind in question or not. If it does, we (...) can trace conceptual differences to internal differences. If it doesn’t, we do not have a case of conceptual difference. Neither case supports Twin Earth externalism. (shrink)

Relativity allegedly contradicts presentism, the dynamic view of time and reality, according to which temporal passage is conceived of as an existentially distinguished ‘moving’ now. Against this common belief, the paper motivates a presentist interpretation of spacetime: It is argued that the fundamental concept of time—proper time—cannot be characterized by the earlier-later relation, i.e., not in the B-theoretical sense. Only the presentist can provide a temporal understanding of the twins’ paradox and of universes with closed timelike curves.

In special cases of partial twinning, two heads, each supporting a more-orless normal human mental life, emerge from a single torso. It is often argued that there must be two people in such a case, even if there is only one biological organism. That would pose a problem for ‘animalism’, the view that people are organisms. The paper argues that it is very hard to say what sort of non-organisms the people in such cases would be. Reflection on partial twinning (...) is no more comfortable for those who think we’re not organisms than for those who think we are. We may have to accept that a single person could have two separate mental lives. (shrink)

From fertilization to approximately the sixteenth day of development, human embryonic cells are said to have the capacities of totipotency and monozygotic twinning, both of which are problematic to a theory of ensoulment at fertilization. In this article I will address the problems which these capacities pose to such a theory and present an interpretation of the biological data which renders ensoulment at fertilization more plausible. I will then argue that not only is an ensoulment theory consistent with current biological (...) data on the human embryo, but it may offer an explanation for the phenomencon of monozygotic twinning. (shrink)

Digital twinning in medicine refers to the idea of simulating a person’s organs, muscles or perhaps their entire body, in order to arrive more effectively at accurate diagnoses, to make treatment recommendations that reflect chances of success and possible side-effects, and to better understand the long-term trajectory of an individual’s overall condition. Digital twins, in these ways, build on the recent movement toward personalised medicine,1 and they undoubtedly present us with exciting opportunities to advance our health. Of course, the (...) opportunities are accompanied by newfound challenges—a common refrain in discussions surrounding emerging technologies. In a recent article, Matthias Braun surveys numerous problems, including the precision of simulations, ownership and consent to the use of digital models, and issues of justice in assuring equitable access to novel medical systems.2 In particular, he places special emphasis on the notion of representation. According to Braun, proper representation naturally calls for correspondence—namely a precise model offering dynamic, real-time feedback as well as transparency, both for the patient and the practitioner, in terms of the data being employed. While technical challenges remain, these goals are quite clear and relatively uncontroversial. Where a host of questions arise, however, is in the discussion on the interaction between the represented persons and their simulations. Alongside questions regarding ownership of one’s digital twin, Braun raises the concern that ‘giving …. (shrink)

In publications in 1914 and 1918, Einstein claimed that his new theory of gravity in some sense relativizes the rotation of a body with respect to the distant stars and the acceleration of the traveler with respect to the stay-at-home in the twin paradox. What he showed was that phenomena seen as inertial effects in a space-time coordinate system in which the non-accelerating body is at rest can be seen as a combination of inertial and gravitational effects in a space-time (...) coordinate system in which the accelerating body is at rest. Two different relativity principles play a role in these accounts: the relativity of non-uniform motion, in the weak sense that the laws of physics are the same in the two space-time coordinate systems involved; what Einstein in 1920 called the relativity of the gravitational field, the notion that there is a unified inertio-gravitational field that splits differently into inertial and gravitational components in different coordinate systems. I provide a detailed reconstruction of Einstein's rather sketchy accounts of the twins and the bucket and examine the role of these two relativity principles. I argue that we can hold on to but that is either false or trivial. (shrink)

Twelve years ago the British media got wind of a London gynecologist who performed an elective reduction on a twin pregnancy reducing it to a singleton. Perhaps not surprisingly, opinion on the moral status of twin reductions was divided. But in the last few years new evidence regarding the medical risks of twin pregnancies has emerged, suggesting that twin reductions are relevantly similar to the reductions performed on high‐end multi‐fetal pregnancies. This evidence has appeared to resolve the moral debate.In this (...) paper I look at the role of clinical evidence in medical ethics. In particular I examine the role of clinical evidence in determining what counts as a significant harm or risk. First, I challenge the extent to which these empirical claims are descriptive, suggesting instead that the evidence is to some degree normative in character. Second, I question whether such empirical claims should count as evidence for what are essentially difficult ethical decisions – a role they appear to play in the case of elective reductions. I will argue that they should not, primarily because the value‐laden nature of this evidence conceals much of what is ethically at stake. It is important to recognize that empirical evidence cannot be a substitute for ethical deliberation. (shrink)

In publications in 1914 and 1918, Einstein claimed that his new theory of gravity somehow relativizes the rotation of a body with respect to the distant stars and the acceleration of the traveler with respect to the stay-at-home in the twin paradox. What he showed was that phenomena seen as inertial effects in a space-time coordinate system in which the non-accelerating body is at rest can be seen as a combination of inertial and gravitational effects in a space-time coordinate system (...) in which the accelerating body is at rest. Two different relativity principles play a role in these accounts: the relativity of non-uniform motion, in the weak sense that the laws of physics are the same in the two space-time coordinate systems involved; what Einstein in 1920 called the relativity of the gravitational field, the notion that there is a unified inertio-gravitational field that splits differently into inertial and gravitational components in different coordinate systems. I provide a detailed reconstruction of Einstein's rather sketchy accounts of the twins and the bucket and examine the role of these two relativity principles. I argue that we can hold on to but that is either false or trivial. (shrink)

Hilary Putnam's Twin Earth thought experiment has come to have an enormous impact on contemporary philosophical thought. But while most of the discussion has taken place within the context of the philosophy of mind and language, Terence Horgan and Mark Timmons (H8cT) have defended the intriguing suggestion that a variation on the original thought experiment has important consequences for ethics.' In a series of papers, they' ve developed the idea of a Moral Twin Earth and have argued that its significance (...) is that it has the resources to undermine naturalistic versions of moral realism.' H8t T don't hold back in their assessment. "Moral Twin.. (shrink)

Some philosophers argue that, because it is subject to twinning and fusion, the early human embryo cannot hold strong moral standing. Supposedly, the fact that an early human embryo can twin or fuse with another embryo entails that it is not a distinct individual, thus precluding it from holding any level of moral standing. I argue that appeals to twinning and fusion fail to show that the early human embryo is not a distinct individual and that these appeals do not (...) provide us with plausible reasons for denying the strong moral standing of the early human embryo. I recognize one possible exception to this general assessment, a particular version of the appeal to fusion. Embryo fusion that results in tetragametic chimerism provides some reason for doubting the early human embryo's moral standing. But twinning and fusion are otherwise irrelevant in this context. (shrink)

During the first 16 days after fertilization, the developing embryo has the capacity to separate into two genetically identical embryos, or monozygotic twins (triplets, etc.). Because of this capacity, philosophers typically argue that the pre-16 day embryo is not a human being. On a Biological Account of Personal Identity (BAPI), which considers us human beings as essentially organisms, the development of the embryo into an organism at 16 (or 21) days marks our origins. The development of an embryo into (...) an organism is also said to mark the point at which the embryo loses its potential to give rise to monozygotic twins. This is considered a strength of the Biological account of our origins. I will argue here that it is the BAPI's own criteria that will have to allow cases of monozygotic twinning occurring even after 16 days, and that in virtue of this a Biological Account faces twinning puzzles usually reserved for earlier accounts of our origins. (shrink)

Mark Timmons and Terry Horgan have argued that the new moral realism, which rests on the causal theory of reference, is untenable. While I do agree that the new moral realism is untenable, I do not think that Timmons and Horgan have succeeded in showing that it is. I will lay out the case for new moral realism and Horgan and Timmons’ argument against it, and then argue that their argument fails. Further, I will discuss Boyd’s semantic theory as well (...) as attempts to improve upon it, raise serious problems for these semantic accounts, and suggest an alternative view that accounts for our use of moral terms. (shrink)

It is widely believed that Twin-Earth-style thought experiments show that the contents of a person's thoughts fail to supervene on her intrinsic properties. Several recent philosophers have made the further claim that Twin-Earth-style thought experiments produce metaphysically necessary conditions for the possession of certain concepts. I argue that the latter view is false, and produce counterexamples to several proposed conditions. My thesis is of particular interest because it undermines some attempts to show that externalism is incompatible with privileged access.

In this dissertation, I attempt to provide some new evidence in favour of the claim that meaning is normative—specifically, for the claim that semantic judgments or ascriptions of meaning are action-guiding. I attempt to achieve this by developing an analogue of the Moral Twin Earth argument advanced by Horgan and Timmons which I call the ‘Meaning Twin Earth’ argument. In the course of the dissertation, I outline Kripke’s 1982 sceptical argument for the thesis that there are no meaning facts in (...) virtue of which ascriptions of meaning are true or false and highlight how the claim that meaning is normative is necessary for that argument to succeed with the kind of generality that Kripke intends. I then explain how one of Kripke’s main arguments against dispositionalist accounts of meaning can be viewed as a kind of open question argument. This argument is ultimately a failure, but nonetheless, I argue that the argument can be revised in a way that does pose a genuine threat to dispositionalist accounts of meaning by using an analogue of Horgan and Timmons’ Moral Twin Earth argument. I claim that a Meaning Twin Earth scenario yields linguistic intuitions that, in my view, are best explained by invoking the claim that meaning is normative. These intuitions constitute evidence against both reductive dispositionalism and anti-normativism about meaning. I forestall several potential objections to the Meaning Twin Earth argument drawn from Plunkett and Sundell, Copp, Merli, and Baker. In closing, I consider two broad options for a normativist account of semantic judgment: an expressivist form and a rationalist form. I argue that, provisionally, McDowell’s rationalist version of factualism about meaning faces a less serious challenge than Gibbard’s expressivist alternative. (shrink)

We understand metahistory as an approach that studies how histories within a particular discipline have been written and focus on insider scientists’ reconstructions of twin research. Using the concept of ethical-political affordances we suggest that such histories are based on a management of resources that prove to be beneficial for representing one’s own research traditions in a positive light. Instead of discussing information on the context and intellectual life of pioneers of the twin method, which include high-caliber eugenicists and Nazi (...) ideologues, and on how the twin method has been used and abused, insider scientists’ accounts present twin research as neutral, objective and void of any kind of political connotations. We show how important leaders of German twin research have been historically managed, and how their contributions have been distorted and omitted. Reasons for historical revisionism by omission and for selectively revised accounts of the past are discussed. Suggestions for writing accounts of the twin method are included and focus on the necessity of self-reflection, considerations regarding one’s own ethical-political inclinations, and review of the existing historical literature. In analyzing these connections, we attempt to understand how science, politics and history interact. (shrink)

In a recent paper in this journal, McCall and Lowe (2003) argue that an understanding of Special Relativity reveals that the A theorist’s notion of temporal passage is consistent with the B theory of time. They arrive at this conclusion by considering the twins’ paradox, where one of two twins (T) travels to Alpha Centauri and back and upon her return has aged 30 years, while her earth-bound twin (S) has aged 40 years.Does this reconcile the A theoretic (...) notion of temporal passage with the B theory of time? I argue not. (shrink)

The Twin Paradox is not a new topic. What is new in this article is that it is an exercise toward interpretation that is functional, in the sense discovered by Lonergan in Method in Theology. The author being interpreted is P. Tipler; and the primary document is taken from his well known textbook. I try to lay out the basic argument in a way that reveals the operative insights, as well as the significant oversights. As it turns out, it would (...) seem that there is neither theoretical basis nor experimental evidence for the alleged “slowing of time” for the high speed traveler. (shrink)

The rapid adoption of digital technologies has revolutionized business operations and introduced emerging concepts such as Digital Twin (DT) technology, which has the potential to predict system responses before they occur, making it an attractive option for smart and sustainable tourism. However, implementing DT software systems poses significant challenges, including compliance with regulations and effective communication among stakeholders, and concerns surrounding security, privacy, and trust with the use of big data. To address these challenges, this paper proposes a documentation framework (...) for architectural decisions (DFAD) that applies the concept of big data governance to the digital system. The framework aims to ensure accountability, transparency, and trustworthiness while adhering to rules and regulations. To demonstrate its applicability, a case study and three case scenarios on the potential use of Mobile Positioning Data (MPD) in Indonesia for DT technology in smart and sustainable tourism were examined. The paper highlights the benefits of DFAD in shaping stakeholder communication and human–machine interactions while leveraging the potential of MPD to measure tourism statistics by Statistics Indonesia since 2016. Not only the documentation framework promotes compliance with regulations, but it also facilitates effective communication among stakeholders and enhances trust and transparency in the use of big data in DT technology for smart and sustainable tourism. This paper emphasizes the importance of effective big data governance and its potential to promote sustainable tourism practices. The multidisciplinarity approach on political science, software engineering, tourism, and official statistics provides an opportunity for academic contribution and decision-making processes. (shrink)

Seventeenth-century authors frequently infer the attributes of time by analogy from already established features of space. The rationale for this can be traced back to Aristotle's analysis of time as ?the number of movement?, where movement requires a prior understanding of spatial magnitude. Although these authors are anti-Aristotelian, they were concerned, contra Aristotle, to establish the existence of ?empty space?, and a notion of absolute space which fit this idea. Although they had no independent rationale for the existence of absolute (...) time, it seemed to go with absolute space, and they drew on a long tradition of space-time parallelism in securing this. (shrink)

We recapitulate (Section 1) some basic details of the system of implicative BCSK logic, which has two primitive binary implicational connectives, and which can be viewed as a certain fragment of the modal logic S5. From this modal perspective we review (Section 2) some results according to which the pure sublogic in either of these connectives (i.e., each considered without the other) is an exact replica of the material implication fragment of classical propositional logic. In Sections 3 and 5 we (...) show that for the pure logic of one of these implicational connectives two – in general distinct – consequence relations (global and local) definable in the Kripke semantics for modal logic turn out to coincide, though this is not so for the pure logic of the other connective, and that there is an intimate relation between formulas constructed by means of the former connective and the local consequence relation. (Corollary 5.8. This, as we show in an Appendix, is connected to the fact that the ‘propositional operations’ associated with both of our implicational connectives are close to being what R. Quackenbush has called pattern functions.) Between these discussions Section 4 examines some of the replacement-of-equivalents properties of the two connectives, relative to these consequence relations, and Section 6 closes with some observations about the metaphor of identical twins as applied to such pairs of connectives. (shrink)

A case study of an ethical dilemma concerning twin nine-year-old sisters in a persistent vegetative state is presented. This is illustrated by the use of a systematic ethical framework to examine the case and the resolution, which was ultimately obtained with nurse—parent interrelations, using the human becoming nursing theory.

The twin paradox (i.e. the reasoning made by the traveling twin, reversing the reasoning made by the earthbound twin, by which it is he who should be older) can be resolved by taking into account the relativity of simultaneity. However, simultaneity depends on a convention about the one-way velocity of light provided that the Reichenbach-Grünbaum hypothesis, is time. So far the resolution has been presented only for the Einstein convention. We show that for all possible choices of the relevant synchronization (...) parameters the calculations performed by both twins yield the same final results when carefully taking into account the relativity of simultaneity according to the conventions they have chosen. Since the final results do not depend on any of the synchronization parameters, the Reichenbach-Grünbaum hypothesis is thereby supported. (shrink)

Robert Stalnaker; XVI*—Twin Earth Revisited, Proceedings of the Aristotelian Society, Volume 93, Issue 1, 1 June 1993, Pages 297–312, https://doi.org/10.1093/ar.

This paper presents a framework for analysing perceptual Twin Earth thought experiments. Visual content normally has an analogue character, and it is argued in this paper that this sets certain constraints on the extent to which Twin Earth thought experiments can be successful. The argumentation in the paper is developed by using examples from visual spatial content. It is argued that visual spatial content can only be “twin-earthed” in a very limited way. Whereas the metrics of space can be twin-earthed, (...) visual experience has a structure that means that it can only be the vehicle for representing entities with geometrical structures. (shrink)

A key objection to naturalistic versions of moral realism is that the (meta)semantics to which they are committed yields incorrect semantic verdicts about so-called Moral Twin Earth cases. Recently, it has been proposed that the Moral Twin Earth challenge can be answered by adopting a neo-Aristotelian semantics for moral expressions. In this paper, I argue that this proposal fails. First, however attractive the central claims of neo-Aristotelianism are, they do not for us have the status of analytic constraints on the (...) use of ethical expressions, as they must if they are to block Moral Twin Earth counterexamples. Second, even when the neo-Aristotelian’s claims are taken as non-negotiable analytic constraints, the semantics faces a dilemma: if characteristic human functioning is understood in an ethically neutral way, the semantics yields an incorrect intension for ‘good human.’ If human functioning is understood in an ethically partisan way, the semantics fails to avoid problematic Moral Twin Earth counterexamples. (shrink)

A number of philosophers defend naturalistic moral realism by appeal to an externalist semantics for moral predicates. The application of semantic externalism to moral predicates has been attacked by Terence Horgan and Mark Timmons in a series of papers that make use of their “ Moral Twin Earth ” thought experiment. In response, several defenders of naturalistic moral realism have claimed that the Moral Twin Earth thought experiment is misleading and yields distorted and inaccurate semantic intuitions. If they are right, (...) the intuitions generated by Moral Twin Earth cannot be appealed to in arguments against externalist moral semantics. The most developed case against the Moral Twin Earth argument that follows this strategy is found in a paper by Stephen Laurence, Eric Margolis and Angus Dawson. Here I argue that their attack on the Moral Twin Earth thought experiment fails. Laurence, Margolis and Dawson have not shown that we have reason to distrust the semantic intuitions it generates. (shrink)

The author reviews one of the more intriguing articles in the stem cell research issue of the journal Metaphilosophy (April 2007), “Killing Embryos for Stem Cell Research,” by Jeff McMahan. He begins by recapitulating McMahan’s argument against the proposition that we are essentially individual human organisms. He then turns to two main critiques of the argument. First, he shows that the term “essentially” is insufficiently defined by McMahan and, more important, if we take the typical explication of the concept by (...) modal metaphysicians, then the claim “we are essentially human beings” is true—contrary to McMahan’s argument. Second, the author offers a counterexample to McMahan’s implicit acceptance of the principle that only beings who have developed the capacity for self-consciousness are the proper subjects of moral worth. The author presents a regenerative therapy example to show that McMahan’s commitment on this point is counterintuitive. National Catholic Bioethics Quarterly 8.2 (Summer 2008): 255–264. (shrink)

"Twin earth" examples have motivated a number of proposals for the lexicography of kind terms in natural languages. It is argued that these proposals create unacceptable difficulties for the analysis of de dicto propositional attitudes. A conservative solution of the twin earth problems is then proposed according to which they reflect pragmatic features of language use rather than semantic features of lexical content.

In this paper I revisit an important response to the Moral Twin Earth (MTE) challenge: The Common Functional Role strategy (CFR). I argue that CFR is open to a revenge problem. MTE-cases allegedly show that two linguistic communities can be in genuine disagreement even when they are regulated by distinct families of properties. CFR provides a way to reconcile the intuition that the two communities are in genuine disagreement with the claim that the use of moral terms by both communities (...) is causally regulated by different families of properties. This is done by identifying a functional role that those families of properties both fulfill. Still, even if CFR is successful, its proponents need to face a serious revenge problem. Roughly, it could be that the families of properties that regulate each community are equally perfect realizers of the relevant higher-order functional state. I suggest that the proponent of CFR faces a dilemma: either CFR has controversial implications about first-order moral theory, or CFR needs to be coupled with substantive and parochial empirical/metaphysical assumptions to avoid those implications. (shrink)

Terence Horgan and Mark Timmons have written a number of articles where they use their Moral Twin Earth thought experiment to attack the new moral realism. The new moral realism is based on advances made in the philosophy of language that allows us to introduce synthetic definitions of moral terms. The Moral Twin Earth thought experiment relies in crucial ways on the use of intuitions. Specifically, it relies on the intuitions that were Earthers and Twin Earthers to meet, they would (...) be able to have genuine moral disagreements. Horgan and Timmons rely on that intuition when they argue that the meaning of the relevant terms on Earth and Twin Earth must be the same. I will argue that we can accept that Earthers and Twin Earthers can have genuine moral disagreement while at the same time claim that the terms they use have different referents and so different semantic meaning. That is, having genuine disagreements does not require that the semantic meaning or the reference of the terms used in the debate being the same. (shrink)