Kristian Camilleri - Academia.edu (original) (raw)
Papers by Kristian Camilleri
Fundamental Theories of Physics, 2022
Niels Bohr and the Philosophy of Physics, 2017
The ideas in Heisenberg's paper on quantum mechanics in 1925 mark the beginning not only of a... more The ideas in Heisenberg's paper on quantum mechanics in 1925 mark the beginning not only of a new phase in modern physics, but also of Heisenberg's own philosophical journey. This thesis examines that journey between 1925 and the late 1950s by situating Heisenberg's philosophy of quantum mechanics in the context of his encounters with his contemporaries as well as the context of various strands of thought in the German-speaking world at the time. Heisenberg's early philosophical critique of the 'classical' viewpoint between 1925 and 1927 bears the decisive influence of Einstein's theory of relativity, more specifically, the positivism he saw as underpinning Einstein's emancipation from Newtonian physics. The positivist influence on Heisenberg's early attitude to quantum mechanics is evident in three ways: (a) his invocation of an observability principle in 1925 to justify the renunciation of the concept of the electron orbit, (b) an instrumentalist conception of understanding, which characterised Heisenberg's response to Schrodinger's demand for classical visualisation in space and time in 1926-7, and (c) the introduction of an operational definition of concepts such as position and velocity in 1927, in an attempt to replace the concepts of classical physics. But after discussions with Bohr and Einstein in 1926-7, Heisenberg soon recognised what we might term his `empiricist' viewpoint was problematic. In 1927 Heisenberg's thought undergoes a shift away from the `empiricist' viewpoint that had underpinned his early philosophy of quantum mechanics. The nature and scope of this transformation, which forms the central theme in this thesis, has, up until now, been poorly understood and often completely neglected. Through his discussions with Bohr, Heisenberg came to the realisation that despite their limitations, classical concepts were conditions for the possibility of the description of all experience. This marked the abandonment of his earlier attempt to replace classical concepts with quantum concepts. The recognition of the primacy of classical language forms the point of departure for much of Heisenberg's later thought, which brought him into contact with the attempts in the German-speaking world in the 1920s to reconstruct Kantian epistemology. By the mid-1930s, Heisenberg advocated a 'pragmatic transformation' of Kantian philosophy, in which classical concepts were held to be a priori in the sense that they remained the conditions for the possibility of experience, but were no longer held to be necessary or universal in a strict Kantian sense. After 1940 Heisenberg saw the paradoxes of quantum mechanics under the aegis of what can be termed a 'transcendental conception of language', according to which language is not a mere tool, but actively shapes, gives form, and objectifies, our 'reality'. The limits of a classical 'description' in quantum mechanics therefore came to signify for Heisenberg, the limits of 'objective reality'. While Bohr exerted perhaps the most important philosophical influence on Heisenberg, their intellectual relationship was characterised by disagreement and misunderstanding. This is most strikingly displayed in their respective views on wave-particle duality and complementarily. While after 1927 Heisenberg accepted Bohr's basic insight that our knowledge of the quantum world is mediated through classical language, he did not share Rohr's interpretation of complementarity. While Heisenberg certainly used terms such as 'complementarity' and wave-particle duality' in his writings, a close reading reveals that these terms had very different meanings for the two physicists. This is particularly evident in the contrast between Heisenberg's notion of wave-particle equivalence and Bohr's idea of complementarity. In bringing to light these divergences between Bohr and Heisenberg, this thesis lends further weight to the view - already advocated by scholars such as John Hendry and Mara Beller - that the so-called Copenhagen interpretation of quantum mechanics should not be thought of as a unified philosophical position, but actually comprises a number of different strands
Niels Bohr and the Philosophy of Physics, 2017
Heisenberg and the Interpretation of Quantum Mechanics By Kristian Camilleri Cambridge Uk Cambridge University Press 2009, Feb 1, 2009
was a pivotal figure in the development of quantum mechanics in the 1920s, and also one of its mo... more was a pivotal figure in the development of quantum mechanics in the 1920s, and also one of its most insightful interpreters. Together with Bohr, Heisenberg forged what is commonly known as the 'Copenhagen interpretation'. Yet Heisenberg's philosophical viewpoint did not remain fixed over time, and his interpretation of quantum mechanics differed in several crucial respects from Bohr's. This book traces the development of Heisenberg's philosophy of quantum mechanics, beginning with his positivism of the mid-1920s, through his neo-Kantian reading of Bohr in the 1930s, and culminating with his 'linguistic turn' in the 1940s and 1950s. It focuses on the nature of this transformation in Heisenberg's thought and its wider philosophical context, which have up until now not received the attention they deserve. This new perspective on Heisenberg's interpretation of quantum mechanics will interest researchers and graduate students in the history and philosophy of twentieth-century physics.
Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 2015
Abstract Over the last three decades, string theory has emerged as one of the leading hopes for a... more Abstract Over the last three decades, string theory has emerged as one of the leading hopes for a consistent theory of quantum gravity that unifies particle physics with general relativity. Despite the fact that string theory has been a thriving research program for the better part of three decades, it has been subjected to extensive criticism from a number of prominent physicists. The aim of this paper is to obtain a clearer picture of where the conflict lies in competing assessments of string theory, through a close reading of the argumentative strategies employed by protagonists on both sides. Although it has become commonplace to construe this debate as stemming from different attitudes to the absence of testable predictions, we argue that this presents an overly simplified view of the controversy, which ignores the critical role of heuristic appraisal. While string theorists and their defenders see the theoretical achievements of the string theory program as providing strong indication that it is ‘on the right track’, critics have challenged such claims, by calling into question the status of certain ‘solved problems’ and its purported ‘explanatory coherence’. The debates over string theory are therefore particularly instructive from a philosophical point of view, not only because they offer important insights into the nature of heuristic appraisal and theoretical progress, but also because they raise deep questions about what constitutes a solved problem and an explanation in fundamental physics.
Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 2009
This paper examines the interweaving of the history of quantum decoherence and the interpretation... more This paper examines the interweaving of the history of quantum decoherence and the interpretation problem in quantum mechanics through the work of two physicists-H. Dieter Zeh and Wojciech Zurek. In the early 1970s Zeh anticipated many of the important concepts of decoherence, framing it within an Everett-type interpretation. Zeh has since remained committed to this view; however, Zurek, whose papers in the 1980s were crucial in the treatment of the preferred basis problem and the subsequent development of density matrix formalism, has argued that decoherence leads to what he terms the 'existential interpretation', compatible with certain aspects of both Everett's relative-state formulation and the Bohr's 'Copenhagen interpretation'. I argue that these different interpretations can be traced back to the different early approaches to the study of environment-induced decoherence in quantum systems, evident in the early work of Zeh and Zurek. I also show how Zurek's work has contributed to the tendency to see decoherence as contributing to a 'new orthodoxy' or a reconstruction of the original Copenhagen interpretation.
Studies in History and Philosophy of Science Part A, 2015
While philosophers have subjected Galileo's classic thought exper... more While philosophers have subjected Galileo's classic thought experiments to critical analysis, they have tended to largely ignored the historical and intellectual context in which they were deployed, and the specific role they played in Galileo's overall vision of science. In this paper I investigate Galileo's use of thought experiments, by focusing on the epistemic and rhetorical strategies that he employed in attempting to answer the question of how one can know what would happen in an imaginary scenario. Here I argue we can find three different answers to this question in Galileo later dialogues, which reflect the changing meanings of 'experience' and 'knowledge' (scientia) in the early modern period. Once we recognise that Galileo's thought experiments sometimes drew on the power of memory and the explicit appeal to 'common experience', while at other times, they took the form of demonstrative arguments intended to have the status of necessary truths; and on still other occasions, they were extrapolations, or probable guesses, drawn from a carefully planned series of controlled experiments, it becomes evident that no single account of the epistemological relationship between thought experiment, experience and experiment can adequately capture the epistemic variety we find Galileo's use of imaginary scenarios. To this extent, we cannot neatly classify Galileo's use of thought experiments as either 'medieval' or 'early modern', but we should see them as indicative of the complex epistemological transformations of the early seventeenth century.
Advances in Historical Studies, 2015
In this paper I examine three emergent trends in praxis-oriented historiography that have underpi... more In this paper I examine three emergent trends in praxis-oriented historiography that have underpinned historical studies of the exact sciences covering the period from 1750 to 1960. The first of these refers to what I call "tradition-centred" histories of scientific practice. This approach focuses on the formation of "cultures of practice" characterized by distinctive epistemic styles, which distinguish them from other such cultures. The second involves "tool-centred" histories of practice. This approach focuses on the way in which tools and techniques of inquiry open up new fields of inquiry, and the way in which the crafting of new tools and the refashioning of existing ones shape the dynamics of scientific practice. The third approach I examine relates to "actor-centred" histories, which typically take the form of biographical accounts focusing on the motivations, judgments and choices of individuals that shape scientific inquiry. This provide a useful analytic framework, in piecing together a broad picture of the different ways in which scientific inquiry is shaped and structured, and to see more clearly how different historiographical approaches complement one another in enriching our understanding of scientific practice.
Synthese, 2013
This paper presents a critical analysis of Tamar Szabó Gendler's view of thought experiments, wit... more This paper presents a critical analysis of Tamar Szabó Gendler's view of thought experiments, with the aim of developing further a constructivist epistemology of thought experiments in science. While the execution of a thought experiment cannot be reduced to standard forms of inductive and deductive inference, in the process of working though a thought experiment, a logical argument does emerge and take shape. Taking Gendler's work as a point of departure, I argue that performing a thought experiment involves a process of self-interrogation, in which we are compelled to reflect on our pre-existing knowledge of the world. In doing so, we are forced to make judgments about what assumptions we see as relevant and how they apply to an imaginary scenario. This brings to light the extent to which certain forms of skill, beyond the ability to make valid logical inferences, are necessary to execute a thought experiment well.
Perspectives on Science, 2015
Over the last three decades, physicists have engaged in, sometimes heated, debates about relative... more Over the last three decades, physicists have engaged in, sometimes heated, debates about relative merits and prospects of string theory as a viable research program and even about its status as a science. The aim of this paper is to provide a deeper understanding of this controversy as a particular form of boundary discourse. Drawing on the sociological work of Thomas Gieryn and Lawrence Prelli, we bring to light the way in which protagonists appeal to, and rhetorically construct, different views about the scientific method and the scientific ethos, in an effort to legitimize or delegitimize string theory.
Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 2015
Niels Bohr's doctrine of the primacy of "classical concepts" is arguably his most criticized and ... more Niels Bohr's doctrine of the primacy of "classical concepts" is arguably his most criticized and misunderstood view. We present a new, careful historical analysis that makes clear that Bohr's doctrine was primarily an epistemological thesis, derived from his understanding of the functional role of experiment. A hitherto largely overlooked disagreement between Bohr and Heisenberg about the movability of the "cut" between measuring apparatus and observed quantum system supports the view that, for Bohr, such a cut did not originate in dynamical (ontological) considerations, but rather in functional (epistemological) considerations. As such, both the motivation and the target of Bohr's doctrine of classical concepts are of a fundamentally different nature than what is understood as the dynamical problem of the quantum-to-classical transition. Our analysis suggests that, contrary to claims often found in the literature, Bohr's doctrine is not, and cannot be, at odds with proposed solutions to the dynamical problem of the quantum-classical transition that were pursued by several of Bohr's followers and culminated in the development of decoherence theory.
It is now widely accepted that environmental entanglement and the resulting decoherence processes... more It is now widely accepted that environmental entanglement and the resulting decoherence processes play a crucial role in the quantum-to-classical transition and the emergence of "classicality" from quantum mechanics. To this extent, decoherence is often understood as signifying a break with the Copenhagen interpretation, and in particular with Bohr's view of the indispensability of classical concepts. This paper analyzes the
AIP Conference Proceedings, 2011
Niels Bohr famously insisted on the indispensability of what he termed "classical concepts." In t... more Niels Bohr famously insisted on the indispensability of what he termed "classical concepts." In the context of the decoherence program, on the other hand, it has become fashionable to talk about the "dynamical emergence of classicality" from the quantum formalism alone. Does this mean that decoherence challenges Bohr's dictum-for example, that classical concepts do not need to be assumed but can be derived? In this paper, we'll try to shed some light down the murky waters where formalism and philosophy mingle. To begin, we'll clarify the notion of classicality in the decoherence description. We'll then discuss Bohr's and Heisenberg's takes on the quantum-classical problem and reflect on the different meanings of the terms "classicality" and "classical concepts" in the writings of Bohr and his followers. This analysis will allow us to put forward some tentative suggestions for how we may better understand the relation between decoherence-induced classicality and Bohr's classical concepts.
Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 2006
This paper examines the development and meaning of Heisenberg's notion of wave-particle equivalen... more This paper examines the development and meaning of Heisenberg's notion of wave-particle equivalence and the way in which it differs from Bohr's more widely known notion of wave-particle complementarity. According to the statistical interpretation of the wave function, developed by Born and Pauli in 1926, the electron is treated as a particle, though it cannot be assigned a well-defined position and momentum at a given time. On the other hand, from the vantage point of quantum electrodynamics developed by Jordan, Klein and Wigner in 1927-1928, the electron is described as a quantized matter wave in three-dimensional space. Heisenberg brought these two empirically equivalent approaches together in his 1929 Chicago lectures. Whereas Bohr argued that it was necessary to use wave and particle descriptions alternatively in different experimental arrangements, Heisenberg insisted that one could interpret the quantum-mechanical equation of motion in terms of either a wave ontology or a particle ontology. Clarifying the differences between Bohr and Heisenberg provides a deeper insight into the divergent views which formed the so-called 'Copenhagen interpretation' of quantum mechanics.
Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 2007
The fractious discussions between Bohr and Heisenberg in Copenhagen in 1927 have been the subject... more The fractious discussions between Bohr and Heisenberg in Copenhagen in 1927 have been the subject of much historical scholarship. However, little attention has been given to Heisenberg's understanding of the notion of complementary space-time and causal descriptions, which was presented for the first time in Bohr's lecture at the 1927 Como conference. In this paper, I argue that Heisenberg's own interpretation of this notion differed substantially from Bohr's. Whereas Bohr had intended this form of complementarity to entail a choice between a space-time description of the electron in an atom, and defining the energy of a stationary state, Heisenberg interpreted the 'causal' description in terms of c-function in configuration space. In disentangling the two views of complementarity, this paper sheds new light on the hidden philosophical disagreements between the proponents of these two founders of the so-called 'Copenhagen interpretation' of quantum mechanics.
Perspectives on Science, 2007
This paper examines the transformation which occurs in Heisenberg's understanding of indeterminac... more This paper examines the transformation which occurs in Heisenberg's understanding of indeterminacy in quantum mechanics between 1926 and 1928. After his initial but unsuccessful attempt to construct new quantum concepts of space and time, in 1927 Heisenberg presented an operational deªnition of concepts such as 'position' and 'velocity'. Yet, after discussions with Bohr, he came to the realisation that classical concepts such as position and momentum are indispensable in quantum mechanics in spite of their limited applicability. This transformation in Heisenberg's thought, which centres on his theory of meaning, marks the critical turning point in his interpretation of quantum mechanics.
Fundamental Theories of Physics, 2022
Niels Bohr and the Philosophy of Physics, 2017
The ideas in Heisenberg's paper on quantum mechanics in 1925 mark the beginning not only of a... more The ideas in Heisenberg's paper on quantum mechanics in 1925 mark the beginning not only of a new phase in modern physics, but also of Heisenberg's own philosophical journey. This thesis examines that journey between 1925 and the late 1950s by situating Heisenberg's philosophy of quantum mechanics in the context of his encounters with his contemporaries as well as the context of various strands of thought in the German-speaking world at the time. Heisenberg's early philosophical critique of the 'classical' viewpoint between 1925 and 1927 bears the decisive influence of Einstein's theory of relativity, more specifically, the positivism he saw as underpinning Einstein's emancipation from Newtonian physics. The positivist influence on Heisenberg's early attitude to quantum mechanics is evident in three ways: (a) his invocation of an observability principle in 1925 to justify the renunciation of the concept of the electron orbit, (b) an instrumentalist conception of understanding, which characterised Heisenberg's response to Schrodinger's demand for classical visualisation in space and time in 1926-7, and (c) the introduction of an operational definition of concepts such as position and velocity in 1927, in an attempt to replace the concepts of classical physics. But after discussions with Bohr and Einstein in 1926-7, Heisenberg soon recognised what we might term his `empiricist' viewpoint was problematic. In 1927 Heisenberg's thought undergoes a shift away from the `empiricist' viewpoint that had underpinned his early philosophy of quantum mechanics. The nature and scope of this transformation, which forms the central theme in this thesis, has, up until now, been poorly understood and often completely neglected. Through his discussions with Bohr, Heisenberg came to the realisation that despite their limitations, classical concepts were conditions for the possibility of the description of all experience. This marked the abandonment of his earlier attempt to replace classical concepts with quantum concepts. The recognition of the primacy of classical language forms the point of departure for much of Heisenberg's later thought, which brought him into contact with the attempts in the German-speaking world in the 1920s to reconstruct Kantian epistemology. By the mid-1930s, Heisenberg advocated a 'pragmatic transformation' of Kantian philosophy, in which classical concepts were held to be a priori in the sense that they remained the conditions for the possibility of experience, but were no longer held to be necessary or universal in a strict Kantian sense. After 1940 Heisenberg saw the paradoxes of quantum mechanics under the aegis of what can be termed a 'transcendental conception of language', according to which language is not a mere tool, but actively shapes, gives form, and objectifies, our 'reality'. The limits of a classical 'description' in quantum mechanics therefore came to signify for Heisenberg, the limits of 'objective reality'. While Bohr exerted perhaps the most important philosophical influence on Heisenberg, their intellectual relationship was characterised by disagreement and misunderstanding. This is most strikingly displayed in their respective views on wave-particle duality and complementarily. While after 1927 Heisenberg accepted Bohr's basic insight that our knowledge of the quantum world is mediated through classical language, he did not share Rohr's interpretation of complementarity. While Heisenberg certainly used terms such as 'complementarity' and wave-particle duality' in his writings, a close reading reveals that these terms had very different meanings for the two physicists. This is particularly evident in the contrast between Heisenberg's notion of wave-particle equivalence and Bohr's idea of complementarity. In bringing to light these divergences between Bohr and Heisenberg, this thesis lends further weight to the view - already advocated by scholars such as John Hendry and Mara Beller - that the so-called Copenhagen interpretation of quantum mechanics should not be thought of as a unified philosophical position, but actually comprises a number of different strands
Niels Bohr and the Philosophy of Physics, 2017
Heisenberg and the Interpretation of Quantum Mechanics By Kristian Camilleri Cambridge Uk Cambridge University Press 2009, Feb 1, 2009
was a pivotal figure in the development of quantum mechanics in the 1920s, and also one of its mo... more was a pivotal figure in the development of quantum mechanics in the 1920s, and also one of its most insightful interpreters. Together with Bohr, Heisenberg forged what is commonly known as the 'Copenhagen interpretation'. Yet Heisenberg's philosophical viewpoint did not remain fixed over time, and his interpretation of quantum mechanics differed in several crucial respects from Bohr's. This book traces the development of Heisenberg's philosophy of quantum mechanics, beginning with his positivism of the mid-1920s, through his neo-Kantian reading of Bohr in the 1930s, and culminating with his 'linguistic turn' in the 1940s and 1950s. It focuses on the nature of this transformation in Heisenberg's thought and its wider philosophical context, which have up until now not received the attention they deserve. This new perspective on Heisenberg's interpretation of quantum mechanics will interest researchers and graduate students in the history and philosophy of twentieth-century physics.
Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 2015
Abstract Over the last three decades, string theory has emerged as one of the leading hopes for a... more Abstract Over the last three decades, string theory has emerged as one of the leading hopes for a consistent theory of quantum gravity that unifies particle physics with general relativity. Despite the fact that string theory has been a thriving research program for the better part of three decades, it has been subjected to extensive criticism from a number of prominent physicists. The aim of this paper is to obtain a clearer picture of where the conflict lies in competing assessments of string theory, through a close reading of the argumentative strategies employed by protagonists on both sides. Although it has become commonplace to construe this debate as stemming from different attitudes to the absence of testable predictions, we argue that this presents an overly simplified view of the controversy, which ignores the critical role of heuristic appraisal. While string theorists and their defenders see the theoretical achievements of the string theory program as providing strong indication that it is ‘on the right track’, critics have challenged such claims, by calling into question the status of certain ‘solved problems’ and its purported ‘explanatory coherence’. The debates over string theory are therefore particularly instructive from a philosophical point of view, not only because they offer important insights into the nature of heuristic appraisal and theoretical progress, but also because they raise deep questions about what constitutes a solved problem and an explanation in fundamental physics.
Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 2009
This paper examines the interweaving of the history of quantum decoherence and the interpretation... more This paper examines the interweaving of the history of quantum decoherence and the interpretation problem in quantum mechanics through the work of two physicists-H. Dieter Zeh and Wojciech Zurek. In the early 1970s Zeh anticipated many of the important concepts of decoherence, framing it within an Everett-type interpretation. Zeh has since remained committed to this view; however, Zurek, whose papers in the 1980s were crucial in the treatment of the preferred basis problem and the subsequent development of density matrix formalism, has argued that decoherence leads to what he terms the 'existential interpretation', compatible with certain aspects of both Everett's relative-state formulation and the Bohr's 'Copenhagen interpretation'. I argue that these different interpretations can be traced back to the different early approaches to the study of environment-induced decoherence in quantum systems, evident in the early work of Zeh and Zurek. I also show how Zurek's work has contributed to the tendency to see decoherence as contributing to a 'new orthodoxy' or a reconstruction of the original Copenhagen interpretation.
Studies in History and Philosophy of Science Part A, 2015
While philosophers have subjected Galileo's classic thought exper... more While philosophers have subjected Galileo's classic thought experiments to critical analysis, they have tended to largely ignored the historical and intellectual context in which they were deployed, and the specific role they played in Galileo's overall vision of science. In this paper I investigate Galileo's use of thought experiments, by focusing on the epistemic and rhetorical strategies that he employed in attempting to answer the question of how one can know what would happen in an imaginary scenario. Here I argue we can find three different answers to this question in Galileo later dialogues, which reflect the changing meanings of 'experience' and 'knowledge' (scientia) in the early modern period. Once we recognise that Galileo's thought experiments sometimes drew on the power of memory and the explicit appeal to 'common experience', while at other times, they took the form of demonstrative arguments intended to have the status of necessary truths; and on still other occasions, they were extrapolations, or probable guesses, drawn from a carefully planned series of controlled experiments, it becomes evident that no single account of the epistemological relationship between thought experiment, experience and experiment can adequately capture the epistemic variety we find Galileo's use of imaginary scenarios. To this extent, we cannot neatly classify Galileo's use of thought experiments as either 'medieval' or 'early modern', but we should see them as indicative of the complex epistemological transformations of the early seventeenth century.
Advances in Historical Studies, 2015
In this paper I examine three emergent trends in praxis-oriented historiography that have underpi... more In this paper I examine three emergent trends in praxis-oriented historiography that have underpinned historical studies of the exact sciences covering the period from 1750 to 1960. The first of these refers to what I call "tradition-centred" histories of scientific practice. This approach focuses on the formation of "cultures of practice" characterized by distinctive epistemic styles, which distinguish them from other such cultures. The second involves "tool-centred" histories of practice. This approach focuses on the way in which tools and techniques of inquiry open up new fields of inquiry, and the way in which the crafting of new tools and the refashioning of existing ones shape the dynamics of scientific practice. The third approach I examine relates to "actor-centred" histories, which typically take the form of biographical accounts focusing on the motivations, judgments and choices of individuals that shape scientific inquiry. This provide a useful analytic framework, in piecing together a broad picture of the different ways in which scientific inquiry is shaped and structured, and to see more clearly how different historiographical approaches complement one another in enriching our understanding of scientific practice.
Synthese, 2013
This paper presents a critical analysis of Tamar Szabó Gendler's view of thought experiments, wit... more This paper presents a critical analysis of Tamar Szabó Gendler's view of thought experiments, with the aim of developing further a constructivist epistemology of thought experiments in science. While the execution of a thought experiment cannot be reduced to standard forms of inductive and deductive inference, in the process of working though a thought experiment, a logical argument does emerge and take shape. Taking Gendler's work as a point of departure, I argue that performing a thought experiment involves a process of self-interrogation, in which we are compelled to reflect on our pre-existing knowledge of the world. In doing so, we are forced to make judgments about what assumptions we see as relevant and how they apply to an imaginary scenario. This brings to light the extent to which certain forms of skill, beyond the ability to make valid logical inferences, are necessary to execute a thought experiment well.
Perspectives on Science, 2015
Over the last three decades, physicists have engaged in, sometimes heated, debates about relative... more Over the last three decades, physicists have engaged in, sometimes heated, debates about relative merits and prospects of string theory as a viable research program and even about its status as a science. The aim of this paper is to provide a deeper understanding of this controversy as a particular form of boundary discourse. Drawing on the sociological work of Thomas Gieryn and Lawrence Prelli, we bring to light the way in which protagonists appeal to, and rhetorically construct, different views about the scientific method and the scientific ethos, in an effort to legitimize or delegitimize string theory.
Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 2015
Niels Bohr's doctrine of the primacy of "classical concepts" is arguably his most criticized and ... more Niels Bohr's doctrine of the primacy of "classical concepts" is arguably his most criticized and misunderstood view. We present a new, careful historical analysis that makes clear that Bohr's doctrine was primarily an epistemological thesis, derived from his understanding of the functional role of experiment. A hitherto largely overlooked disagreement between Bohr and Heisenberg about the movability of the "cut" between measuring apparatus and observed quantum system supports the view that, for Bohr, such a cut did not originate in dynamical (ontological) considerations, but rather in functional (epistemological) considerations. As such, both the motivation and the target of Bohr's doctrine of classical concepts are of a fundamentally different nature than what is understood as the dynamical problem of the quantum-to-classical transition. Our analysis suggests that, contrary to claims often found in the literature, Bohr's doctrine is not, and cannot be, at odds with proposed solutions to the dynamical problem of the quantum-classical transition that were pursued by several of Bohr's followers and culminated in the development of decoherence theory.
It is now widely accepted that environmental entanglement and the resulting decoherence processes... more It is now widely accepted that environmental entanglement and the resulting decoherence processes play a crucial role in the quantum-to-classical transition and the emergence of "classicality" from quantum mechanics. To this extent, decoherence is often understood as signifying a break with the Copenhagen interpretation, and in particular with Bohr's view of the indispensability of classical concepts. This paper analyzes the
AIP Conference Proceedings, 2011
Niels Bohr famously insisted on the indispensability of what he termed "classical concepts." In t... more Niels Bohr famously insisted on the indispensability of what he termed "classical concepts." In the context of the decoherence program, on the other hand, it has become fashionable to talk about the "dynamical emergence of classicality" from the quantum formalism alone. Does this mean that decoherence challenges Bohr's dictum-for example, that classical concepts do not need to be assumed but can be derived? In this paper, we'll try to shed some light down the murky waters where formalism and philosophy mingle. To begin, we'll clarify the notion of classicality in the decoherence description. We'll then discuss Bohr's and Heisenberg's takes on the quantum-classical problem and reflect on the different meanings of the terms "classicality" and "classical concepts" in the writings of Bohr and his followers. This analysis will allow us to put forward some tentative suggestions for how we may better understand the relation between decoherence-induced classicality and Bohr's classical concepts.
Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 2006
This paper examines the development and meaning of Heisenberg's notion of wave-particle equivalen... more This paper examines the development and meaning of Heisenberg's notion of wave-particle equivalence and the way in which it differs from Bohr's more widely known notion of wave-particle complementarity. According to the statistical interpretation of the wave function, developed by Born and Pauli in 1926, the electron is treated as a particle, though it cannot be assigned a well-defined position and momentum at a given time. On the other hand, from the vantage point of quantum electrodynamics developed by Jordan, Klein and Wigner in 1927-1928, the electron is described as a quantized matter wave in three-dimensional space. Heisenberg brought these two empirically equivalent approaches together in his 1929 Chicago lectures. Whereas Bohr argued that it was necessary to use wave and particle descriptions alternatively in different experimental arrangements, Heisenberg insisted that one could interpret the quantum-mechanical equation of motion in terms of either a wave ontology or a particle ontology. Clarifying the differences between Bohr and Heisenberg provides a deeper insight into the divergent views which formed the so-called 'Copenhagen interpretation' of quantum mechanics.
Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 2007
The fractious discussions between Bohr and Heisenberg in Copenhagen in 1927 have been the subject... more The fractious discussions between Bohr and Heisenberg in Copenhagen in 1927 have been the subject of much historical scholarship. However, little attention has been given to Heisenberg's understanding of the notion of complementary space-time and causal descriptions, which was presented for the first time in Bohr's lecture at the 1927 Como conference. In this paper, I argue that Heisenberg's own interpretation of this notion differed substantially from Bohr's. Whereas Bohr had intended this form of complementarity to entail a choice between a space-time description of the electron in an atom, and defining the energy of a stationary state, Heisenberg interpreted the 'causal' description in terms of c-function in configuration space. In disentangling the two views of complementarity, this paper sheds new light on the hidden philosophical disagreements between the proponents of these two founders of the so-called 'Copenhagen interpretation' of quantum mechanics.
Perspectives on Science, 2007
This paper examines the transformation which occurs in Heisenberg's understanding of indeterminac... more This paper examines the transformation which occurs in Heisenberg's understanding of indeterminacy in quantum mechanics between 1926 and 1928. After his initial but unsuccessful attempt to construct new quantum concepts of space and time, in 1927 Heisenberg presented an operational deªnition of concepts such as 'position' and 'velocity'. Yet, after discussions with Bohr, he came to the realisation that classical concepts such as position and momentum are indispensable in quantum mechanics in spite of their limited applicability. This transformation in Heisenberg's thought, which centres on his theory of meaning, marks the critical turning point in his interpretation of quantum mechanics.