Online research in philosophy

This paper approaches the scientific realism question from a naturalistic perspective. On the basis of a historical case study of the work of James Clerk Maxwell and Ludwig Boltzmann on the kinetic theory of gases, it shows that scientists’ views about the epistemological status of theories and models typically interact with their scientific results. Subsequently, the implications of this result for the current realism debate are analysed. The case study supports Giere’s moderately realist view of scientific models and theories, based on the notion of similarity, and it highlights the crucial role of model users. The paper concludes with a discussion of Boltzmann’s Bildtheorie, the sophisticated form of realism that he developed in response to the scientific problems of kinetic theory.

: 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 definition 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.

In this paper, I argue that Heisenberg's mature philosophy of quantum mechanics must be understood in the context of his epistemological project to reinterpret and redefine Kant's notion of the a priori. After discussions with Weizsäcker and Hermann in Leipzig in the 1930s, Heisenberg attempted to ground his interpretation of quantum mechanics on what might be termed a 'practical' transformation of Kantian philosophy. Taking as his starting point, Bohr's doctrine of the indispensability of classical concepts, Heisenberg argued that concepts such as space, time and causality can be regarded as 'practically a priori', in so far as they remain the conditions for the possibility of experience and even of 'objective reality', though they are not universal and necessary in a strictly Kantian sense. We cannot avoid using classical concepts in the description of experiments in quantum theory, despite the fact that there are limits to their applicability. Such concepts are, for Heisenberg, historically contingent, yet indispensable in our time, because we have no other language through which we can describe and conceive of the interaction between 'object' and 'measuring device'.

Recent literature on Bohm's alternative to mainstream quantum mechanics may create the misleading impression that, except for perfunctory dismissals, the theory was ignored by the physics community in the years immediately following its proposal. As a matter of fact, Einstein, Pauli, and Heisenberg all published criticisms of Bohm's theory, explaining their reasons for not accepting the theory. These criticisms will be discussed and evaluated in this article.

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.

Orthodox quantum theory is the theory propounded in the late 1920’s, principally by Bohr, Heisenberg, and Pauli. It is, in essence, what is taught in our university courses in quantum physics. It is epistemological and pragmatic: it consists of rules designed to allow us to compute expectations pertaining to our future experiences on the basis of the knowledge that we have extracted from our past experiences. This approach is proclaimed in the opening words of Niels Bohr’s 1934 book “Atomic theory and the description of nature”.

In this paper, we discuss various aspects of Heisenberg’s thought on hidden variables in the period 1927–1935. We also compare Heisenberg’s approach to others current at the time, specifically that embodied by von Neumann’s impossibility proof, but also views expressed mainly in correspondence by Pauli and by Schroedinger. We shall base ourselves mostly on published and unpublished materials that are known but little-studied, among others Heisenberg’s own draft response to the EPR paper. Our aim will be not only to clarify Heisenberg’s thought on the hidden-variables question, but in part also to clarify how this question was understood more generally at the time.

Wolfgang Pauli (1900-1958) was one of the greatest physicists of the past century. He played a leading role in the development of modern physics and was known for his ruthless intellectual integrity. Pauli first became famed through the publication of his encyclopaedia article on the theory of relativity (Pauli, 1921) when he was still a student of Sommerfeld's. Einstein much admired this article, which remained a classic.

In this paper I argue that demonstrative induction can deal with the problem ofthe underdetermination of theory by evidence. I present the historical case studyof spectroscopy in the early 1920s, where the choice among different theorieswas apparently underdetermined by spectroscopic evidence concerning the alkalidoublets and their anomalous Zeeman effect. By casting this historical episodewithin the methodological framework of demonstrative induction, the localunderdetermination among Bohr's, Heisenberg's, and Pauli's rival theories isresolved in favour of Pauli's theory of the electron's spin.