We address the question of whether it is possible to operate a time machine by manipulating matter and energy so as to manufacture closed timelike curves. This question has received a great deal of attention in the physics literature, with attempts to prove no-go theorems based on classical general relativity and various hybrid theories serving as steps along the way towards quantum gravity. Despite the effort put into these no-go theorems, there is no widely accepted definition of a time machine. (...) We explain the conundrum that must be faced in providing a satisfactory definition and propose a resolution. Roughly, we require that all extensions of the time machine region contain closed timelike curves; the actions of the time machine operator are then sufficiently “potent” to guarantee that closed timelike curves appear. We then review no-go theorems based on classical general relativity, semi-classical quantum gravity, quantum field theory on curved spacetime, and Euclidean quantum gravity. Our verdict on the question of our title is that no result of sufficient generality to underwrite a confident “yes” has been proven. Our review of the no-go results does, however, highlight several foundational problems at the intersection of general relativity and quantum physics that lend substance to the search for an answer. (shrink)

A number of recent papers have criticized what they call the dynamical interpretation of evolutionary theory found in Elliott Sober’s The Nature of Selection. Sober argues that we can think of evolutionary theory as a theory of forces analogous to Newtonian mechanics. These critics argue that there are several important disanalogies between evolutionary and Newtonian forces: Unlike evolutionary forces, Newtonian forces can be considered in isolation, they have source laws, they compose causally in a straightforward way, and they are intermediate (...) causes in causal chains. Here we defend and extend the forces analogy by arguing that each of these criticisms is based on a misunderstanding of Newtonian forces. Our discussion also has the interesting consequence that natural selection turns out to be more similar to forces such as friction and elastic forces rather than the more canonical gravitation. (shrink)

Cet article propose la première édition critique complète des Questions de Jean Buridan sur la Physiognomonie pseudo-aristotélicienne. L’introduction situe le texte dans la tradition physiognomonique médiévale, tout en indiquant les relations de la physiognomonie à la sémiologie, à l’astrologie et à la philosophie morale. L’édition se fonde sur trois manuscrits principaux, et un quatrième pour l’une des deux versions de la première question. Suit l’édition d’une version d’authenticité douteuse, qui recoupe en partie la version éditée, et de trois questions sur (...) la physiognomonie extraites d’un texte qui semble composite, formé de questions de Buridan ou d’esprit buridanien. (shrink)

A volume of papers inspired by the work of George E. Smith on confirmation and evidence in advanced science—from Newton's gravitation theory to the physics of molecules.

We discuss the possibility to build and operate a time machine, a device that produces closed timelike curves. We specify the spacetime structure needed to implement a time machine and assess attempted no-go results against time machines in classical general relativity, semi-classical quantum gravity, quantum field theory on curved spacetime, and in Euclidean quantum gravity. Such no-go theorems for time machines would show that, under physically reasonable conditions, CTCs cannot develop in spacetimes initially free of these pathologies. Our review indicates (...) that an investigation of the prospects of achieving no-go results has not been entirely successful in establishing such generality. At the same time, the pursuit of chronology protection results has proved to be a fruitful way to probe the foundations of classical GTR and the interface between general relativity and quantum field theory. (shrink)

Biological evolution provides a creative fount of complex and subtle adaptations, often surprising the scientists who discover them. However, because evolution is an algorithmic process that transcends the substrate in which it occurs, evolution’s creativity is not limited to nature. Indeed, many researchers in the field of digital evolution have observed their evolving algorithms and organisms subverting their intentions, exposing unrecognized bugs in their code, producing unexpected adaptations, or exhibiting outcomes uncannily convergent with ones in nature. Such stories routinely reveal (...) creativity by evolution in these digital worlds, but they rarely fit into the standard scientific narrative. Instead they are often treated as mere obstacles to be overcome, rather than results that warrant study in their own right. The stories themselves are traded among researchers through oral tradition, but that mode of information transmission is inefficient and prone to error and outright loss. Moreover, the fact that these stories tend to be shared only among practitioners means that many natural scientists do not realize how interesting and lifelike digital organisms are and how natural their evolution can be. To our knowledge, no collection of such anecdotes has been published before. This paper is the crowd-sourced product of researchers in the fields of artificial life and evolutionary computation who have provided first-hand accounts of such cases. It thus serves as a written, fact-checked collection of scientifically important and even entertaining stories. In doing so we also present here substantial evidence that the existence and importance of evolutionary surprises extends beyond the natural world, and may indeed be a universal property of all complex evolving systems. (shrink)

No More Dying: The Conquest of Aging and the Extension of Human Life. By Joel Kurtzman and Phillip Gordon. Prolongevity. By Albert Rosenfeld.

We introduce a family of rules for adjusting one's credences in response to learning the credences of others. These rules have a number of desirable features. 1. They yield the posterior credences that would result from updating by standard Bayesian conditionalization on one's peers' reported credences if one's likelihood function takes a particular simple form. 2. In the simplest form, they are symmetric among the agents in the group. 3. They map neatly onto the familiar Condorcet voting results. 4. They (...) preserve shared agreement about independence in a wide range of cases. 5. They commute with conditionalization and with multiple peer updates. Importantly, these rules have a surprising property that we call synergy - peer testimony of credences can provide mutually supporting evidence raising an individual's credence higher than any peer's initial prior report. At first, this may seem to be a strike against them. We argue, however, that synergy is actually a desirable feature and the failure of other updating rules to yield synergy is a strike against them. (shrink)

Pierre Maquet1,2,6, Steven Laureys1,2, Philippe Peigneux1,2,3, Sonia Fuchs1, Christophe Petiau1, Christophe Phillips1,6, Joel Aerts1, Guy Del Fiore1, Christian Degueldre1, Thierry Meulemans3, André Luxen1, Georges Franck1,2, Martial Van Der Linden3, Carlyle Smith4 and Axel Cleeremans5.

In this paper, following an idea of Christophe Chalons. I propose a new kind of forcing axiom, the Maximality Principle, which asserts that any sentence varphi holding in some forcing extension $V^P$ and all subsequent extensions $V^{P\ast Q}$ holds already in V. It follows, in fact, that such sentences must also hold in all forcing extensions of V. In modal terms, therefore, the Maximality Principle is expressed by the scheme $(\lozenge \square \varphi) \Rightarrow \square \varphi$ , and is equivalent to (...) the modal theory S5. In this article. I prove that the Maximality Principle is relatively consistent with ZFC. A boldface version of the Maximality Principle, obtained by allowing real parameters to appear in φ, is equiconsistent with the scheme asserting that $V_\delta \prec V$ for an inaccessible cardinal δ, which in turn is equiconsistent with the scheme asserting that ORD is Mahlo. The strongest principle along these lines is $\square MP\!_{\!\!\!\!\!\!_{\!\!_\sim}}$ , which asserts that $MP\!_{\!\!\!\!\!\!_{\!\!_\sim}}$ holds in V and all forcing extensions. From this, it follows that $0^\#$ exists, that $x^\#$ exists for every set x, that projective truth is invariant by forcing, that Woodin cardinals are consistent and much more. Many open questions remain. (shrink)

In this paper, following an idea of Christophe Chalons, I propose a new kind of forcing axiom, the Maximality Principle, which asserts that any sentence φ holding in some forcing extension $V\P$ and all subsequent extensions V\P*\Qdot holds already in V. It follows, in fact, that such sentences must also hold in all forcing extensions of V. In modal terms, therefore, the Maximality Principle is expressed by the scheme $\implies\necessaryφ$, and is equivalent to the modal theory S5. In this article, (...) I prove that the Maximality Principle is relatively consistent with \ZFC. A boldface version of the Maximality Principle, obtained by allowing real parameters to appear in φ, is equiconsistent with the scheme asserting that $Vδ\elesub V$ for an inaccessible cardinal δ, which in turn is equiconsistent with the scheme asserting that $\ORD$ is Mahlo. The strongest principle along these lines is $\necessary\MPtilde$, which asserts that $\MPtilde$ holds in V and all forcing extensions. From this, it follows that 0# exists, that x# exists for every set x, that projective truth is invariant by forcing, that Woodin cardinals are consistent and much more. Many open questions remain. (shrink)

Hitchcock advances a diachronic Dutch Book argument (DDB) for a 1/3 answer to the Sleeping Beauty problem. Bradley and Leitgeb argue that Hitchcock’s DDB argument fails. We demonstrate the following: (a) Bradley and Leitgeb’s criticism of Hitchcock is unconvincing; (b) nonetheless, there are serious reasons to worry about the success of Hitchcock’s argument; (c) however, it is possible to construct a new DDB for 1/3 about which such worries cannot be raised.

Aping apes: Edgar Allan Poe's "The murders in the Rue Morgue" and Richard Wright's Native son -- Slavery's bestiary: Joel Chandler Harris's Uncle Remus tales -- Autoimmunity and ante-racism: Philip Roth's The human stain -- Ashamed of shame: J.M. Coetzee's Disgrace.

The critical reception of Joel Chandler Harris's Uncle Remus Tales has often interpreted these animal fables as allegories of American slavery. Such an approach, however, risks what Steve Baker calls the ‘denial of the animal’, which displaces animal signifiers onto human signifieds. Through readings of ‘The Wonderful Tar-Baby Story’ and ‘How the Birds Talk’, I ask what it might mean to take seriously the numerous historical, political and philosophical questions posed by the animal ‘form’ that these characters assume, including (...) Heidegger's ontological differentiation between thing, animal and human, and Derrida's displacement of the conventional Cartesian distinction between animal reaction and human response. I argue that the racist equation of blacks with mimicry relies precisely on this dubious opposition. Remus's stories thus challenge our understandings of both race and language by showing how repetition and mimicry condition every ‘human’ response. (shrink)

You and I are watching a spider crawl across the carpet. We are both aware of the spider, and aware that both are so aware. We are jointly attending to it. This collection of essays addresses a bewildering array of questions that arise regarding the notion of joint attention. How should joint attention be characterised in adults? In particular, how can we articulate the sense in which it is plausible to say that nothing is hidden from either participant in cases (...) of joint attention? What is the relationship between joint attention and the much discussed phenomenon of common, or mutual, knowledge? What account should be given of the development of the capacity for joint attention in children (and in non-human primates)? At what age is it correct to say that children are engaging in episodes of full blown joint attention? Relatedly, what is the relation between joint attention and pointing behaviour, gaze following and mutual affect regulation? Why is it that autistic children appear to exhibit a joint attention deficiency, and what might this tell us about autism, or about joint attention itself? Does the capacity for joint attention presuppose an understanding of the notion of attention, or more generally a subject of experience, and if so what is the relation between that understanding and the types of behaviour associated with joint attention? More generally, how does joint attention relate to our understanding of others? Finally, is the capacity for joint attention pivotal for the development of linguistic communication, or perhaps even a sense of objectivity—of the mind independence of the world? (shrink)

Volume 20, Issue 1, February 2019, Page 99-102.

Despite the recent increase of interest in the work of Merleau-Ponty there is still a persistent tendency to overlook the uniqueness of the philosophical position he advances in Phenomenology of Perception. In this article I present a reading of Merleau-Ponty’s account of the phenomenological reduction that explains how it is original. I do this by contrasting his presentation of the reduction with that of the early Husserl, highlighting how his emphasis on the phenomenology of the ‘perceived world’ leads him to (...) reject Husserl’s conception of phenomenology as a ‘philosophical science,’ and the Kantian language in which the this account is framed. I go on to critically discuss the interpretations of the reduction advanced by Stephen Priest and Joel Smith as examples of readings that fail to fully grasp Merleau-Ponty’s account of the ‘natural attitude’ as resting on the inherent objectivizing structure that is built into perception itself. The way that these authors misinterpret Merleau-Ponty helps to make maximally clear the profound philosophical significance that he places on the phenomenology of the ‘perceived world’. (shrink)

Un nouveau type de paternalisme s’est développé ces dix dernières années sous l’impulsion de travaux innovateurs de certains économistes comportementaux. Ce nouveau type de paternalisme, que j’appelle ici paternalisme comportemental, s’est popularisé grâce à la théorie du « coup de pouce » de Richard Thaler et Cass Sunstein et remet en question l’idée selon laquelle le paternalisme serait inacceptable dans nos sociétés. L’objet de cet article est d’évaluer sa légitimité morale sans, néanmoins, se limiter à son supposé libertarianisme. Les résultats (...) de mon investigation peuvent se résumer ainsi : bien que le paternalisme comportemental soit généralement reconnu pour son caractère libéral, il ne satisfait pas en fait les conditions de ce que Joel Feinberg nomme le « paternalisme mou ». Néanmoins, il possède des qualités morales sous-estimées par ses partisans. Il résiste d’abord très bien à la critique égalitariste d’Elizabeth Anderson. A la différence des formes traditionnelles de paternalisme, le paternalisme comportemental n’est pas dégradant et n’est pas ostracisant. Le paternalisme comportemental, enfin, peut se targuer d’être véritablement altruiste, à la condition, cependant, d’abandonner les hypothèses principales de Sunstein et Thaler. Classification JEL : A12, D64, I18, I31, K32. (shrink)

Un nouveau type de paternalisme s’est développé ces dix dernières années sous l’impulsion de travaux innovateurs de certains économistes comportementaux. Ce nouveau type de paternalisme, que j’appelle ici paternalisme comportemental, s’est popularisé grâce à la théorie du « coup de pouce » de Richard Thaler et Cass Sunstein et remet en question l’idée selon laquelle le paternalisme serait inacceptable dans nos sociétés. L’objet de cet article est d’évaluer sa légitimité morale sans, néanmoins, se limiter à son supposé libertarianisme. Les résultats (...) de mon investigation peuvent se résumer ainsi : bien que le paternalisme comportemental soit généralement reconnu pour son caractère libéral, il ne satisfait pas en fait les conditions de ce que Joel Feinberg nomme le « paternalisme mou ». Néanmoins, il possède des qualités morales sous-estimées par ses partisans. Il résiste d’abord très bien à la critique égalitariste d’Elizabeth Anderson. A la différence des formes traditionnelles de paternalisme, le paternalisme comportemental n’est pas dégradant et n’est pas ostracisant. Le paternalisme comportemental, enfin, peut se targuer d’être véritablement altruiste, à la condition, cependant, d’abandonner les hypothèses principales de Sunstein et Thaler. Classification JEL : A12, D64, I18, I31, K32. (shrink)

Among early modern Christian kabbbalists such as Pico della Mirandola and Christian Knorr von Rosenroth, Kabbalah counts as part of philosophia perennis and esoteric Jewish philosophy. Bruckers differentiation between Kabbalah as esoteric Jewish philosophy and Maimonides as exoteric Jewish philosophy is taken up by Tiedemann and Hegel, and is well known to Schelling and Molitor. In opposition to this taxinomy among Christian philosophers, Jewish philosophers and scholars of »Wissenschaft des Judentums« like Salomon Munk, Manuel Joel, Hermann Cohen or Julius (...) Guttmann exclude Kabbalah from the canon of Jewish philosophy proper, exemplified by Yehuda Halevi or Maimonides. It is only after World War I that Gershom Scholem inaugurates the modern research of Kabbalah as »mysticism«, juxtaposed to philosophy and to the rationalistic traditions inJudaism. (shrink)

The Dutch system of obstetric care is often recommended for midwife-attended births, the high number of home deliveries, and the low rate of intervention during pregnancy and labour. In this contribution, the question is addressed whether processes of medicalization can be demonstrated in the Dutch midwife practice. Medicalization of pregnancy and childbirth is often criticized because it creates dependency on the medical system and infringement of the autonomy of pregnant women. It is concluded that medicalization is present in the practice (...) of Dutch independent midwives, however it is less clear and outspoken than in hospital policies. (shrink)

This volume is the first systematic presentation of the work of Albert Einstein, comprising fourteen essays by leading historians and philosophers of science that introduce readers to his work. Following an introduction that places Einstein's work in the context of his life and times, the book opens with essays on the papers of Einstein's 'miracle year', 1905, covering Brownian motion, light quanta, and special relativity, as well as his contributions to early quantum theory and the opposition to his light quantum (...) hypothesis. Further essays relate Einstein's path to the general theory of relativity (1915) and the beginnings of two fields it spawned, relativistic cosmology and gravitational waves. Essays on Einstein's later years examine his unified field theory program and his critique of quantum mechanics. The closing essays explore the relation between Einstein's work and twentieth-century philosophy, as well as his political writings. (shrink)

In an age where issues like climate change and the unintended consequences of technological innovation are high on the ethical and political agenda, questions about the nature and extent of our responsibilities to future generations have never been more important, yet simultaneously so difficult to answer. This book takes a unique approach to the problem by drawing on diverse traditions of thinking about care (including developmental psychology, phenomenology and feminist ethics) to explore the nature and meaning of our relationship with (...) the future. Demonstrating that many influential perspectives on intergenerational ethics, including positions advanced by John Rawls, Brian Barry, and Ulrich Beck are undermined by problems relating to uncertainty, it shows that an approach based on care ethics can confront the uncertain future successfully and give a viable account of the nature and scope of future-oriented responsibilities. (shrink)

Unifying physics by describing a variety of interactions – or even all interactions – within a common framework has long been an alluring goal for physicists. One of the most ambitious attempts at unification was made in the 1910s by Gustav Mie. Mie aimed to derive electromagnetism, gravitation, and aspects of the emerging quantum theory from a single variational principle and a well-chosen Lagrangian. Mie’s main innovation was to consider nonlinear field equations to allow for stable particle-like solutions (now called (...) solitons), and he clarified the use of variational principles in the context of special relativity. The following brief introduction to Mie’s work has three main objectives. The first is to explain how Mie’s project fit into the contemporary development of the electromagnetic world view. Part of Mie’s project was to develop a relativistic theory of gravitation as a consequence of his generalized electromagnetic theory, and our second goal is to briefly assess this work, which reflects the conceptual resources available for developing a new account of gravitation by analogy with electromagnetism. Finally, Mie was a vocal critic of other approaches to the problem of gravitation. Mie’s criticisms of Einstein, in particular, bring out the subtlety and novelty of the ideas that Einstein used to guide his development of general relativity. (shrink)

The authors survey some debates about the nature and structure of physical theories and about the connections between our physical theories and naturalized metaphysics. The discussion is organized around an “ideal view” of physical theories and criticisms that can be raised against it. This view includes controversial commitments regarding the best analysis of physical modalities and intertheory relations. The authors consider the case in favor of taking laws as the primary modal notion, discussing objections related to alleged violations of the (...) laws, the apparent need to appeal to causality, and the status of probability. The “ideal view” includes a commitment that fundamental physical theories are explanatorily sufficient. The authors discuss several challenges to recovering the manifest image from fundamental physics, along with a distinct challenge to reductionism based on acknowledging the contributions of less fundamental theories in physical explanations. (shrink)

We address the question of whether it is possible to operate a time machine by manipulating matter and energy so as to manufacture closed timelike curves. This question has received a great deal of attention in the physics literature, with attempts to prove no- go theorems based on classical general relativity and various hybrid theories serving as steps along the way towards quantum gravity. Despite the effort put into these no-go theorems, there is no widely accepted definition of a time (...) machine. We explain the conundrum that must be faced in providing a satisfactory definition and propose a resolution. Roughly, we require that all extensions of the time machine region contain closed timelike curves; the actions of the time machine operator are then sufficiently "potent" to guarantee that closed timelike curves appear. We then review no-go theorems based on classical general relativity, semi-classical quantum gravity, quantum field theory on curved spacetime, and Euclidean quantum gravity. Our verdict on the question of our title is that no result of sufficient generality to underwrite a confident "yes" has been proven. Our review of the no-go results does, however, highlight several foundational problems at the intersection of general relativity and quantum physics that lend substance to the search for an answer. (shrink)

This paper is an enquiry into the logical, metaphysical, and physical possibility of time travel understood in the sense of the existence of closed worldlines that can be traced out by physical objects. We argue that none of the purported paradoxes rule out time travel either on grounds of logic or metaphysics. More relevantly, modern spacetime theories such as general relativity seem to permit models that feature closed worldlines. We discuss, in the context of Gödel's infamous argument for the ideality (...) of time based on his eponymous spacetime, what this apparent physical possibility of time travel means. Furthermore, we review the recent literature on so-called time machines, i.e., of devices that produce closed worldlines where none would have existed otherwise. Finally, we investigate what the implications of the quantum behaviour of matter for the possibility of time travel might be and explicate in what sense time travel might be possible according to leading contenders for full quantum theories of gravity such as string theory and loop quantum gravity. (shrink)

The cosmological constant problem stems from treating quantum field theory and general relativity as an effective field theory. We argue that the problem is a reductio ad absurdum, and that one should reject the assumption that general relativity can generically be treated as an EFT. This marks a failure of naturalness, and an internal signal that EFT methods do not apply in all spacetime domains. We then take an external view, showing that the assumptions for using EFTs are violated in (...) general relativistic domains where Λ is relevant. We highlight some ways forward that do not depend on naturalness. (shrink)

Suppose we believe that God created the world. Then surely we want it to be the case that he intended, in some sense at least, to create THIS world. Moreover, most theists want to hold that God didn't just guess or hope that the world would take one course or another; rather, he KNEW precisely what was going to take place in the world he planned to create. In particular, of each person P, God knew that P was to exist. (...) Call this the "standard" conception. Most theists find the standard conception appealing. Unfortunately, the view seems to conflict with the equally appealing idea — call it "temporal actualism" — that there are no "future" individuals beyond those that already exist in the present moment. For, on this view, for any historical person P, prior to creation, there was no such person as P and hence nothing about P for God to know. Hence, in particular, God couldn't have known that P was to exist. This is of course not a new problem. But past solutions to it are highly problematic. In this paper, after canvassing previous approaches, I will propose a solution that seems to preserve both temporal actualism and a suitably robust form of the standard conception while avoiding the pitfalls of the past. (shrink)