THE PRINCIPLE OF SUPERPOSITION. The need for a quantum theory Classical mechanics has been developed continuously from the time of Newton and applied to an ...

: Although Dirac rarely participated in the interpretational debates over quantum theory, it is traditionally assumed that his views were aligned with Heisenberg and Bohr in the so-called Copenhagen-Göttingen camp. However, an unpublished—and apparently unknown—lecture of Dirac's reveals that this view is mistaken; in the famous debate between Einstein and Bohr, Dirac sided with Einstein. Surprisingly, Dirac believed that quantum mechanics was not complete, that the uncertainty principle would not survive in the future physics, and that (...) a deterministic description of the microworld would be recovered. In this paper I show how we can make sense of this unpublished lecture in the context of Dirac's broader philosophy of quantum mechanics, and how our present understanding of Dirac's philosophical views must be revised. (shrink)

In his [1937, 1938], Paul Dirac proposed his “Large Number Hypothesis” (LNH), as a speculative law, based upon what we will call the “Large Number Coincidences” (LNC’s), which are essentially “coincidences” in the ratios of about six large dimensionless numbers in physics. Dirac’s LNH postulates that these numerical coincidences reflect a deeper set of law-like relations, pointing to a revolutionary theory of cosmology. This led to substantial work, including the development of Dirac’s later [1969/74] cosmology, and (...) other alternative cosmologies, such as the Brans-Dicke modification of GTR, and to extensive empirical tests. We may refer to the generic hypothesis of “Large Number Relations” (LNR’s), as the proposal that there are lawlike relations of some kind between the dimensionless numbers, not necessarily those proposed in Dirac’s early LNH. Such relations would have a profound effect on our concepts of physics, but they remain shrouded in mystery. Although Dirac’s specific proposals for LNR theories have been largely rejected, the subject retains interest, especially among cosmologists seeking to test possible variations in fundamental constants, and to explain dark energy or the cosmological constant. In the first two sections here we briefly summarize the basic concepts of LNR’s. We then introduce an alternative LNR theory, using a systematic formalism to express variable transformations between conventional measurement variables and the true variables of the theory. We demonstrate some consistency results and review the evidence for changes in the gravitational constant G. The theory adopted in the strongest tests of Ġ/G, by the Lunar Laser Ranging (LLR) experiments, assumes: Ġ/G = 3(dr/dt)/r – 2(dP/dt)/P – (dm/dt)/m, as a fundamental relationship. Experimental measurements show the RHS to be close to zero, so it is inferred that significant changes in G are ruled out. However when the relation is derived in our alternative theory it gives: Ġ/G = 3(dr/dt)/r – 2(dP/dt)/P – (dm/dt)/m – (dR/dt)/R. The extra final term (which is the Hubble constant) is not taken into account in conventional derivations. This means the LLR experiments are consistent with our LNR theory (and others), and they do not really test for a changing value of G at all. This failure to transform predictions of LNR theories correctly is a serious conceptual flaw in current experiment and theory. (shrink)

A one-to-one correspondence is established between linearized space-time metrics of general relativity and the wave equations of quantum mechanics. Also, the key role of boundary conditions in distinguishing quantum mechanics from classical mechanics, will emerge naturally from the procedure. Finally, we will find that the methodology will enable us to introduce not only test charges but also test masses by means of gauges.

In this article, the rotational invariance of entangled quantum states is investigated as a possible cause of the Pauli exclusion principle. First, it is shown that a certain class of rotationally invariant states can only occur in pairs. This is referred to as the coupling principle. This in turn suggests a natural classification of quantum systems into those containing coupled states and those that do not. Surprisingly, it would seem that Fermi–Dirac statistics follows as a consequence of this coupling (...) while the Bose–Einstein follows by breaking it. In Sec. 5, the above approach is related to Pauli's original spin-statistics theorem and finally in the last two sections, a theoretical justification, based on Clebsch–Gordan coefficients and the experimental evidence respectively, is presented. (shrink)

One of the key episodes of history of modern physics – Paul Dirac’s startling contrivance of the relativistic theory of the electron – is elicited in the context of lucid epistemological model of mature theory change. The peculiar character of Dirac’s synthesis of special relativity and quantum mechanics is revealed by comparison with Einstein’s sophisticated methodology of the General Relativity contrivance. The subtle structure of Dirac’s scientific research program and first and foremost the odd principles that (...) put up its powerful heuristics is scrutinized with special emphasis on the highly controversial tenet of “mathematical beauty.” It is contended that despite the relentless Dirac’s remarks denigrating the controversial role of philosophy one can trace its indirect influence through Arthur Eddington’s and Hermann Weyl’s whimsical mathematical models. Accordingly, the milestones of Dirac’s research programme realization in the distinctive context of the applied epistemological doctrine are indicated. (shrink)

In 1927, Paul Dirac first explicitly introduced the idea that electrodynamical processes can be evaluated by decomposing them into virtual (modern terminology), energy non-conserving subprocesses. This mode of reasoning structured a lot of the perturbative evaluations of quantum electrodynamics during the 1930s. Although the physical picture connected to Feynman diagrams is no longer based on energy non-conserving transitions but on off-shell particles, emission and absorption subprocesses still remain their fundamental constituents. This article will access the introduction and the (...) initial reception of this picture of subsequent transitions (PST) by conceiving of concepts, models, and their representations as tools for the practitioners. I will argue for a multi-factorial explanation of Dirac’s initial, verbally explicit introduction: the mathematical representation he had developed was highly suggestive and already partly conceptualized; Dirac was philosophical flexible enough to talk about transitions when no actual transitions, according to the general interpretation of quantum mechanics of the time, occurred; and, importantly, Dirac eventually used the verbal exposition in the same paper in which he introduced it. The direct impact of PST on the conception of quantum electrodynamical processes will be exemplified by its reflection in diagrammatical representations. The study of the diverging ontological commitments towards PST immediately after its introduction opens up the prehistory of a philosophical debate that stretches out into the present: the dispute about the representational and ontological status of the physical picture connected to the evaluation of the perturbative series of QED and QFT. (shrink)

This paper describes a long-standing, though little-known, debate between Paul Dirac and Werner Heisenberg over the nature of scientific methodology, theory change, and intertheoretic relations. Following Heisenberg’s terminology, their disagreements can be summarized as a debate over whether the classical and quantum theories are “open” or “closed.” A close examination of this debate sheds new light on the philosophical views of two of the great founders of quantum theory.

Sehr verehrter Herr Professor! Ihrem Buch über die Prinzipien der Quantenmechanik verdanke ich das Verständnis für die Geschlossenheit und Schönheit dieser Theorie, einer Schönheit, die, wie mir scheint, in der abstrakt symbolischen Art Ihrer Darstellung überhaupt erst richtig zur Geltung kommt. Die starken Anregungen, die ich von Ihnen erhalten habe und für die ich Ihnen dankbar bin, haben zugleich in mir den Wunsch geweckt, Ihre Meinung über einige Gedankengänge kennen zu lernen, die sich mir beim Studium der Quantenmechanik mehr und (...) mehr aufgedrängt haben. (shrink)

Drawing on Peter Harrison's argument that individuals should be attributed a central role in analyses of the relationship between science and religion, this article proposes that an understanding of personality can help us better appreciate a person's attitudes to both science and religion. Rather than seeing an individual's attitudes to these two topics as separate, if sometimes overlapping, parts of their lives, it is suggested that both may result from psychological drives and sometimes from the same psychological drive. Two contrasting (...) case studies are employed to illustrate this proposal. First, Paul Dirac who, it is argued, was on the autistic spectrum, a personality profile that is often linked to both mathematical physics and atheism. By contrast, Michael Faraday's scientific practice and his commitment to a specific form of Christianity were underpinned by his need for security, as assured by the God‐given laws that operated in both the physical and moral domains. (shrink)

So-called antimatter in the form of elementary particles such as positive electrons (antielectrons alias positrons) and negative protons (antiprotons) has for long been investigated by physicists. However, atoms or molecules of this exotic kind are conspicuously absent from nature. Since antimatter is believed to be symmetric with ordinary matter, the flagrant asymmetry constitutes a problem that still worries physicists and cosmologists. As first suggested by Paul Dirac in 1933, in distant parts of the universe there might be entire (...) stars and galaxies made of antiparticles alone. Why not? This paper examines how the concepts of antiparticles and antimatter slowly migrated from particle physics to astronomy and cosmology. At around 1970 a few physicists speculated about an anti-universe separate from ours while others looked for the charge asymmetry in quantum processes in the early big-bang explosion of the universe. Others again proposed a ‘plasma cosmology’ that kept our world and the hypothetical world of antimatter apart. Soviet physicists and astronomers were no less interested in the problem than their colleagues in the West. The paper details the development up to the late 1970s, paying attention not only to mainstream scientific works but also to more speculative ideas, some of them very speculative. By that time the antimatter mystery remained mysterious – which is still the situation. (shrink)

The theoretical physicist Paul Dirac rejected, explicitly on aesthetic grounds, a successful theory known as quantum electrodynamics (QED), which is the prototype for the family of theories known as quantum field theories (QFTs). Remarkably, the theoretical physicist Steven Weinberg, also largely on aesthetic grounds, supports QED and other QFTs. In order to evaluate these opposing aesthetic views a short introduction to the physical properties of QFTs is presented together with a detailed analysis of the aesthetic claims of (...) class='Hi'>Dirac and Weinberg. It turns out that Dirac rejected QED, without regard to its success, because this theory fails to yield to what he perceived as beautiful mathematics, whereas Weinberg's support of QFTs is founded primarily on the physical concepts of the theories. In particular, he relies on symmetries that are the basis for the construction of the extremely successful current fundamental theories of particles physics. This success was decisive in leading to Weinberg's conviction of the beauty of QFTs. As a result of the evaluation of these approaches, the factors causing scientists to perceive a theory as being a fundamentally beautiful theory are discussed in detail. (shrink)

Ever since Thomas Kuhn's influential The Structure of Scientific Revolutions (1962), textbooks have suffered a bad reputation. They have been accused of distorting—at times purportedly—history and of feeding students with an unacceptably simplified and optimistic view of science. This attitude started to change only in recent times. With the increase of attention paid not only to how theories are conceived, but also how they are practiced, disseminated, and appropriated, historians have rehabilitated textbooks as a legitimate site of knowledge production. In (...) this paper, I adopt textbooks as an instrument to unfold multiple facets of the culture that allowed quantum physics to flourish between 1900 and the early 1930s. I organize the article around two stories about two major textbooks, i.e., Sommerfeld′s Atombau und Spektrallinien and Dirac′s Principles of Quantum Mechanics. I explore the complex pedagogical cultures underlying these two masterpieces and how they intersect local agendas. (shrink)

Everything around us is made of 'stuff', from planets, to books, to our own bodies. Whatever it is, we call it matter or material substance. It is solid; it has mass. But what is matter, exactly? We are taught in school that matter is not continuous, but discrete. As a few of the philosophers of ancient Greece once speculated, nearly two and a half thousand years ago, matter comes in 'lumps', and science has relentlessly peeled away successive layers of matter (...) to reveal its ultimate constituents.Surely, we can't keep doing this indefinitely. We imagine that we should eventually run up against some kind of ultimately fundamental, indivisible type of stuff, the building blocks from which everything in the Universe is made. The English physicist Paul Dirac called this 'the dream of philosophers'. But science has discovered that the foundations of our Universe are not as solid or as certain and dependable as we might have once imagined. They are instead built from ghosts and phantoms, of a peculiar quantum kind. And, at some point on this exciting journey of scientific discovery, we lost our grip on the reassuringly familiar concept of mass.How did this happen? How did the answers to our questions become so complicated and so difficult to comprehend? In Mass Jim Baggott explains how we come to find ourselves here, confronted by a very different understanding of the nature of matter, the origin of mass, and its implications for our understanding of the material world. Ranging from the Greek philosophers Leucippus and Democritus, and their theories of atoms and void, to the development of quantum field theory and the discovery of a Higgs boson-like particle, he explores our changing understanding of the nature of matter, and the fundamental related concept of mass. (shrink)

Classical mechanics and quantum mechanics are two of the most successful scientific theories ever discovered, and yet how they can describe the same world is far from clear: one theory is deterministic, the other indeterministic; one theory describes a world in which chaos is pervasive, the other a world in which chaos is absent. Focusing on the exciting field of 'quantum chaos', this book reveals that there is a subtle and complex relation between classical and quantum mechanics. It challenges the (...) received view that classical and quantum mechanics are incommensurable, and revives another, largely forgotten tradition due to Niels Bohr and Paul Dirac. By artfully weaving together considerations from the history of science, philosophy of science, and contemporary physics, this book offers a new way of thinking about intertheory relations and scientific explanation. It will be of particular interest to historians and philosophers of science, philosophically-inclined physicists, and interested non-specialists. (shrink)

Quantum electrodynamics is the theory of electrons and other elementary charged particles, interacting through the exchange of light quanta. Albert Einstein introduced the light quantum in 1905, but for about three decades physicists applied quantum ideas mainly in theories of the structure and behavior of matter, not to electromagnetic radiation itself, which was always treated semi-classically. This began to change after 1923 with the discovery of the Compton effect and its kinematic description by Arthur Compton and Peter Debye, based on (...) the light quantum. In this paper we review the study of high-energy radiation that led to Compton's discovery. We discuss the analysis of the intensity distribution of Compton-scattered radiation that together with the ''new'' quantum theory beginning in 1925, resulted in the development, especially by Pascual Jordan and Paul Dirac, of a quantum theory of electromagnetic radiation in interaction with matter. (shrink)

Examples of uniformly moving charge distributions that possess conserved electromagnetic stress tensors are exhibited. These constitute stable systems with covariantly characterized electromagnetic mass. This note, on a topic to which Paul Dirac made a significant contribution in 1938, is dedicated to him for his 80th birthday.

Two hundred years ago, Friedrich Schleiermacher took critical issue with Immanuel Kant's intellectual notion of intuition as applied to human nature (Wellmon 2006). He found it necessary to modify—"hermeneutically," as he said—Kant's notion of anthropology by enabling it to include as human the new and strange human tribes Captain Cook found in the Pacific South Seas. A similar hermeneutic move is necessary if physics is to include the local contextual empirical syntheses of relativity and quantum physics. In this hermeneutical revision (...) the synthesis is formed around the notion of a Hilbert Vector Space as the universal grammar of physics, adding to it the dynamic of the Schrödinger equation, and representing empirical "observables" by projection operators that map the subspaces of definite measurable values. Among the set of observable projection operators, some pairs share the same subspace, commute with one another, and share a common laboratory setting. Other pairs do not share this property and are described as being mutually complementary. Complementary symmetries introduce into the discursive language of physics the commonsense notion of contextuality. The new synthesis, proposed by Eugene Wigner, John von Neumann, and (in his own way) Paul Dirac, brought physics into the community of common language and established it as a work of general human achievement. 1. (shrink)

It has been almost eighty years since Paul Dirac delivered a lecture on the relationship between mathematics and physics and since 1960 that Eugene Wigner wrote about the unreasonable effectiveness of mathematics in the natural sciences. The field of cosmology and efforts to define a more comprehensive theory have changed significantly since the 1960s; thus, it is time to refocus on the issue. This paper expands on ideas addressed by these two great physicists, specifically, the ultimate effectiveness of (...) mathematics to describe nature. After illustrating how theoretical physic predicted discoveries, the concepts of established theories are summarized. Then, the “world equation” which combines all key physics theories is conceptually described. As the possible last piece of the puzzle, String Theory is briefly defined. And last, a cursory overview of an extreme proposal is presented — the world as a mathematical object. However, there is no fundamental reason to believe that math will allow mankind to completely comprehend nature. If math does not provide a comprehensive theory, nature will retain her secrets. (shrink)

Stephen Edelston Toulmin, philosopher and historian of science, pioneer in the logical analysis of substantive argumentation, was educated in physics and philosophy at Cambridge, where he studied with Paul Dirac, John Wisdom and Ludwig Wittgenstein. Cambridge, Issac Newton’s university, remained his philosophical home: he always was very critical of the way that philosophy was done at The Other Place, as Oxford is known there. The only philosopher whom he really revered there was John Austin – although it is (...) necessary hastily to add that he deeply respected Gilbert Ryle and Isaiah Berlin. Like the latter, he considered himself a “public intellectual”. As such he was delighted to be invited to become a contributor to Encounter and later, from the mid-1960s a regular contributor to The New York Review of Books. He was fascinated by Wittgenstein, attending as many of his classes as he could, but had no interest in becoming close to him. Both the idea of discipleship and Wittgenstein’s dominating personally were uncongenial to him. Like Wittgenstein and Berlin he was never at home among professional philosophers . On occasion his relationships with philosophers could be stormy indeed as was the case with Sir Karl Popper and Nelson Goodman. He prided himself on being an amateur and was only mildly disturbed when “experts” chided him as a bungler. His deepest belief was that professional philosophers do not determine what the real problems of philosophy are; rather those problems arise out of conundrums in human life. That meant for him engaging in intense dialogues, with physicists, psychologists, psychoanalysts, medical doctors, lawyers, musician artists and, of course, historians of science. (shrink)

For more than a century the notion of a pre-established harmony between the mathematical and physical sciences has played an important role not only in the rhetoric of mathematicians and theoretical physicists, but also as a doctrine guiding much of their research. Strongly mathematized branches of physics, such as the vortex theory of atoms popular in Victorian Britain, were not unknown in the nineteenth century, but it was only in the environment of fin-de-siècle Germany that the idea of a pre-established (...) harmony really took off and became part of the mathematicians’ ideology. Important historical figures were in this respect David Hilbert, Hermann Minkowski and, somewhat later, Albert Einstein. Roughly similar ideas can be found also among British theorists, among whom Arthur Eddington, Arthur Milne, and Paul Dirac are singled out. Although largely limited to the period 1870–1940, the paper also considers Max Tegmark’s recent hypothesis of the universe being a one-to-one reflection of mathematical structures. (shrink)

Many scientists and philosophers of science think that beauty should play a role in theory selection. Physicists like Paul Dirac and Steven Weinberg explicitly claim that the ultimate explanations of the physical world must be beautiful. And philosophers of science like Peter Lipton say that we should expect the loveliest theory to also be the most likely. In this paper, I contend that these arguments from loveliness bear a striking similarity to Thomas Aquinas’s arguments from fittingness; both seem (...) to presume that the most beautiful theory is also the most probable. To do this, I first layout the explanatory virtues that are commonly thought to be constitutive of a lovely theory. Second, I elucidate Aquinas’ arguments from fittingness and show how they work in light of his account of beauty. Lastly, I connect the two kinds of aesthetic arguments and show the extent to which they overlap. (shrink)

The article examines the development of physics research in Ukraine on the example of the Ukrainian Institute of Physics and Technology (UIPT). Founded on the initiative of the eminent physicist Abram Ioffe, the UIPT has gradually become one of the world’s leading research institutions. During 1928–1938, many important events took place at the institute, which became markers for the development of physics in Ukraine and the USSR as well as in the world. An experiment on the fission of atomic nucleus (...) using artificially accelerated protons confirmed the validity of the intentions to reorient research towards nuclear physics. The involvement of foreign specialists in the work of the UIPT contributed to the informal consolidation of scientific thinking in physics. Outstanding physicists of the world such as Boris Podolskyi, Oleksandr Weisberg, Konrad Weiselberg, Friedrich Houtermans, Laszlo Tisza, Fritz Lange, Victor Weisskopf, George Placzek, Paul Dirac, Georgii Gamov, Niels Bohr, Paul Ehrenfest, and others worked here for longer or shorter periods. Niels Bohr, Ivar Waller, Milton S. Plesset, Evan J. Williams, and Leon Rosenfeld made reports at the theoretical conferences of UIPT. As a result, in the late 1920s and during the 1930s, an informal society of physicists from around the world was formed in Kharkiv. The consolidation of talented scientists has accumulated traditions, centuries of experience, and practical knowledge in the field from many scientific schools around the world. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Philosophy and Rhetoric 34.2 (2001) 177-178 [Access article in PDF] Book Review Quantum Dialogue: The Making of a Revolution Quantum Dialogue: The Making of a Revolution. Mara Beller. Chicago: U of Chicago P, 1999. Pp. xv + 365. $35.00 cloth. This book presents a critical discussion of the development of quantum physics in the early part of the second quarter of the twentieth century. The opening statement of the (...) first chapter, a quotation attributed to Werner Heisenberg--"Science is rooted in conversations"--sets the tone for the whole book.The book is divided into two parts: "Dialogical Emergence" and "Rhetorical Consolidation." An introductory chapter, "Novelty and Dogma," outlines what is new for quantum theory as compared with what is already accepted in physics. Another six chapters build upon the various relationships between the people and ideas that led ultimately to the acceptance of a number of principles to explain a large variety of physical phenomena at the atomic level. The next six chapters generally show how a vocal group of scientists put forward the "Copenhagen Interpretation"; these scientists used the rhetorical skills of Niels Bohr and often unjustly criticized other views significant to the development of quantum mechanics. The final two chapters relate to later philosophical and historical implications of the development of quantum theory as discussed by the scientists themselves, as well as philosophers and historians of science, including the author.Mara Beller carries out a rather unique discussion of the scientific ideas and the social relationships among the scientists. She has carefully studied many of the original letters between the leading scientists at the time--Niels Bohr, Max Born, Paul Dirac, Albert Einstein, Werner Heisenberg, Wolfgang Pauli, Erwin Schrodinger--and numerous others who were not so well known. In particular, she discusses how these scientists influenced each other. A prime example is carefully developed in the early chapters of the book, where Beller discusses Heisenberg's work on matrix mechanics. After Heisenberg learned of Schrodinger's wave mechanics, he strongly denied the use of this rival method. As a result of discussions with [End Page 177] Bohr, Pauli, and others, however, many elements of wave mechanics began to appear in matrix mechanics in somewhat hidden forms. As quantum theory evolved in the following years, aspects of both wave mechanics and matrix mechanics came together in complementarity, due largely to the influence of Bohr. Yet, Beller questions, in the second part of the book, whether much of the process of assimilation by Bohr was one sided, so that the Copenhagen interpretation always came out the stronger.This book has scientific merit for both students and professionals in the physical sciences. During the intervening three quarters of a century since the founding years of quantum mechanics, many fundamental ideas have come to be accepted as basic concepts in chemistry, physics, material science, and related fields in engineering. In fact, the acceptance of the usefulness of quantum mechanics is so strong that many of ideas are seen as an integral part of the field itself, to the point that the proceeding concepts in early quantum theory are often neglected. This situation is rather unfortunate. It arises in part from the contemporary educational system, in which only the most immediate examples relevant to a particular field are used. The discussions in this book bring forward a completely different side of the development of quantum theory, which in many ways continues right up to the present. Here, the philosophical and social sides are stressed over the practical applications. Above and beyond this strength, the presentation could be understood by many people outside the physical sciences even though many of the scientific objectives may not be so very apparent. Quantum Dialogue is recommended to all readers who have an interest in the issues that arose during the early years of quantum theory's development. David E. Miller Department of Physics The Pennsylvania State University... (shrink)

Decision theory aims at a general account of rationality covering humans but to begin makes idealizations about decision problems and agents' resources and circumstances. It treats inerrant agents with unlimited cognitive power facing tractable decision problems. This book systematically rolls back idealizations and without loss of precision treats errant agents with limited cognitive abilities facing decision problems without a stable top option. It recommends choices that maximize utility using quantizations of beliefs and desires in cases where probabilities and utilities are (...) indeterminate and using higher-order utility analysis in cases of limited access to probabilities and utilities. For agents burdened with mistakes, it advocates reasonable attempts to correct unacceptable mistakes before deciding. In decision problems without a stable top option, a topic of game theory, it proposes maximizing self-conditional utility among self-supporting options. In games of strategy, the new principles lead to solutions that are Pareto optimal among equilibria composed of jointly self-supporting strategies. Offering an account of bounded rationality, the bookmakes large strides toward realism in decision theory. (shrink)

" Quel contraste! quel brusque passage! La hiérarchie, la dis¬cipline, l'ordre que l'autorité se charge d'assurer, les dogmes qui règlent fermement la vie : voilà ce qu'aimaient les hommes du dix-septième siècle. Les contraintes, l'autorité, les dogmes, voilà ce que détestent les hommes du dix-huitième siècle, leurs successeurs immédiats. Les premiers sont chrétiens, et les autres antichrétiens ; les premiers croient au droit divin, et les autres au droit naturel ; les premiers vivent à l'aise dans une société qui se (...) divise en classes inégales, les seconds ne rêvent qu'éga-lité. Certes, les fils chicanent volontiers les pères, s'imaginant qu'ils vont refaire un monde qui n'attendait qu'eux pour devenir meilleur : mais les remous qui agitent les générations successi¬ves ne suffisent pas à expliquer un changement si rapide et si décisif. La majorité des Français pensait comme Bossuet ; tout d'un coup, les Français pensent comme Voltaire : c'est une révolution.Pour savoir comment elle s'est opérée, nous nous sommes engagés dans des terres mal connues. On étudiait beaucoup le dix-septième siècle, autrefois ; on étudie beaucoup le dix-¬huitième siècle, aujourd'hui. A leurs confins s'étend une zone incertaine, malaisée, où l'on peut espérer encore découvertes et aventures. Nous l'avons parcourue, choisissant pour la borner deux dates non rigoureuses : d'une part, les environs de 1680, et d'autre part, 1715...". (shrink)

General information -- The animals themselves -- Philosophical arguments -- Laws -- Political realities -- Social realities -- Education and the arts -- Contemporary sciences -- Major figures and organizations in the animal rights movement -- The future of animal rights.

pGiven the long-standing and deeply rooted intertwinement between reason and philosophy, there is a pressing need to reappraise our operative conceptions of rationality and critical inquiry in the wake of the transition from foundationalism to postfoundationalism.nbsp; For while opening up exciting new vistas, this transition poses perplexing problems regarding how we might go about justifying our knowledge claims without the possibility of recourse to incontrovertible foundations, indubitable starting points, or algorithmic procedures.nbsp; The challenge is all the more acute given that (...) the turn to language and intersubjectivity that characterises this transition has fostered the proliferation of a diversity of competing and allegedly self-validating worldviews, that render the encounter with difference an indispensable feature of the contemporary epistemological landscape while reinforcing the threat of relativism and groundlessness./ppThrough engaging with the work of Juuml;rgen Habermas, Hans-Georg Gadamer and Michel Foucault, three theorists widely recognized as major contributors to the contemporary debate, the present paper responds to these problems by seeking to delineate the constitutive features of a dialogically-oriented conception of rationality and critical inquiry capable of meeting postfoundationalist needs.nbsp; In the process, it reinforces the advantages of the reading these theorists as complementary rather than as oppositional, as has typically been the case./p. (shrink)

Modeling involves the use of false idealizations, yet there is typically a belief or hope that modeling somehow manages to deliver true information about the world. The paper discusses one possible way of reconciling truth and falsehood in modeling. The key trick is to relocate truth claims by reinterpreting an apparently false idealizing assumption in order to make clear what possibly true assertion is intended when using it. These include interpretations in terms of negligibility, applicability, tractability, early-step, and more. Elaborations (...) are suggested about their precise formulations, mutual relationships, and truth-aptness. (shrink)