The theory of quantum mechanics has often been thought to show an affinity with logical empiricism: in both, observation plays a central role, and questions about what is unobservable are dismissed. However, there were also strong tensions between the logical empiricism of the Vienna Circle and implications drawn from quantum physics. In the 1920s and 1930s, many physicists thought that quantum mechanics revealed a limit to what could be known scientifically, and this opened the door to a wide range of speculations, in which quantum mechanics was connected with free will, organic life, psychology, and religion—speculations in which many leading quantum physicists were engaged. Members of the Vienna Circle, such as Frank and Schlick, looked at quantum mechanics for a confirmation of their empiricist views, but they were at the same time critical about these wider implications drawn from quantum mechanics, which in their eyes were connected with broader mystical and irrational trends in society. They engaged in particular with the views of Bohr and Jordan, both of whom expressed a sympathy for logical empiricism while at the same time arguing for claims that proved hard to reconcile with the scientific world conception of the Vienna Circle.
The theory of quantum mechanics has often been thought to show an affinity with logical empiricism: in both, observation plays a central role, and questions about what is unobservable are dismissed. However, there were also strong tensions between the logical empiricism of the Vienna Circle and implications drawn from quantum physics. In the 1920s and 1930s, many physicists thought that quantum mechanics revealed a limit to what could be known scientifically, and this opened the door to a wide range of speculations, in which quantum mechanics was connected with free will, organic life, psychology, and religion—speculations in which many leading quantum physicists were engaged. Members of the Vienna Circle, such as Frank and Schlick, looked at quantum mechanics for a confirmation of their empiricist views, but they were at the same time critical about these wider implications drawn from quantum mechanics, which in their eyes were connected with broader mystical and irrational trends in society. They engaged in particular with the views of Bohr and Jordan, both of whom expressed a sympathy for logical empiricism while at the same time arguing for claims that proved hard to reconcile with the scientific world conception of the Vienna Circle.
The measurement problem in quantum mechanics first cropped up during the 1930s during a famous series of debates between Einstein and Bohr concerning the physical adequacy – or ‘completeness’ – of the orthodox (Copenhagen) theory.1 As we have seen, it is a topic central to Hanson’s thinking not only with regard to quantum mechanics but also for its wider bearing on the scope and limits of scientific knowledge, the theory-laden character of observations, and the underdetermination of theory by evidence.2 Thus it is frequently adduced in support of his proto-Kuhnian claim that scientists working within different paradigms must be thought of as observing different things or inhabiting ‘different worlds’.3 What I propose to do now is look in more detail at the arguments surrounding this topic and, especially, at various proposals – from Einstein down – for a realist construal of the quantum data (i.e., the empirical measurement-results) that would offer an alternative to Hanson’s idea of the uncertainty principle as placing an absolute limit on our knowledge of objects and events in the microphysical domain. Having set out his arguments already in chapters 4 and 5, I shall not make any further detailed reference to Hanson’s work but assume that the reader who has come this far will have them clearly in mind. Thus my purpose in the remainder of this book is to raise the question: what becomes of the paradigm-relativist approach to issues in the history and philosophy of science if it derives so much of its suasive force from an interpretation of quantum mechanics that has proved increasingly open to challenge?
In The Conceptual Development of Quantum Physics, Max Jammer observes that “certain philosophical ideas of the late nineteenth century not only prepared the intellectual climate for, but contributed decisively to, the formation of the new conceptions of the modern quantum theory”—specifically, “contingentism, existentialism, pragmatism, and logical empiricism,” which, argues Jammer “united in rejecting causality though on different grounds” and “prepared, so to speak, the philosophical background for modern quantum mechanics.” Regarding this same rejection of causality in physics in Weimar Germany—a rejection central to the quantum interpretation—Paul Forman argues that “substantive problems in atomic physics played only a secondary role in the genesis of this acausal persuasion, [and] that the most important factor was the social-intellectual pressure exerted upon the physicists as members of the German academic community.” Along these same lines, in an interview with Einstein in 1932, James Gardner Murphy said, “scientists live in the world just like other people…. They cannot escape the influence of the milieu in which they live. And that milieu at the present time is characterized largely by a struggle to get rid of the causal chain in which the world has entangled itself.” In all of these cases, the development of quantum physics is attributed to the zeitgeist of the time, with the critics adopting a “hypodermic” model wherein intellectual currents have a direct influence on scientific discovery.
This chapter explores the relation between logical positivism and the early development and interpretation of quantum mechanics. Despite frequent claims to the contrary, we find that logical positivism did not influence physicists’ view of quantum mechanics until well into the 1930s, if at all. Special emphasis is given to Niels Bohr due to his central role in the understanding of the new physics. While Bohr was in contact with several central figures of logical positivism and on several occasions expressed his agreement with them, we find that Bohr developed his main ideas concerning quantum mechanics well before this contact was made. Instead, this chapter speculates that it was Bohr who tried to influence logical positivism: Bohr believed that understanding quantum mechanics provided us with a general philosophical lesson to which the logical positivist would be responsive. Because of similarities in viewpoints, Bohr apparently had hoped that this might compel the logical positivists to join him in the attempt to extend his ideas of complementarity and contextualism beyond quantum mechanics.
The political attitude and the ideology of a very small elite of physicists (Niels Bohr, Werner Heisenberg, Max Born and view other) played a major role in the construction of the Copenhagen Interpretation of quantum mechanics in the 1920s.Lastly, the hegemonic standard acausal Copenhagen Interpretation of quantum mechanics abandoned the principle of causality in quantum mechanics and opened a very wide door to mysticism, logical fallacies and wishful thinking in physics and in science as such.Historically, the Second International Congress for the Unity of Science (Copenhagen, June 21-26, 1936) tried to solve the problem of causality within physics but without a success.Thus far, 80 years after the Second International Congress for the Unity of Science this publication will expel Bohr's and Heisenberg's dogma of non-causality out of quantum mechanics and re-establish the unrestricted validity of the principle of causality at quantum level and under conditions of relativity theory by mathematizing the relationship between cause and effect in the form of the mathematical formula of the causal relationship k.In contrast to Bohr, Heisenberg and other representatives of the Copenhagen interpretation quantum mechanics, a realistic interpretation of quantum theory grounded on the unrestricted validity of the principle of causality will expel any kind of mysticism from physics and enable a quantization of the gravitational field too.
For over nine decades, quantum mechanics has profoundly shaped our understanding of nature, offering explanations for the stability of atoms, the formation of mole cules, the properties of materials, and phenomena such as light or radioactivity. It is essential to modern technologies—from microchips to lasers—and underpins the physics of elementary particles. Yet, despite its successes, it remains a deeply mysterious theory, confronting a central enigma: why does the quantum world behave so differently from everyday reality? Elements such as superposition and quantum entanglement—which allow particles to exist simultaneously in multiple states or remain interconnected regardless of distance—contradict classical world intuitions. This gap between microscopic and macroscopic behavior has given rise to what is known as the “measurement problem,” raising fundamental questions about the nature of reality. Diverging interpretations have led to two major schools of thought: anti-realism, promoted by Niels Bohr, which holds that reality depends on the observer and their interaction with measurement instruments; and realism, supported by Albert Einstein, which argues that quantum mechanics is incomplete and that eality exists independently of observation. Bohr’s complementary philosophy and Heisenberg’s uncertainty principle were central to the formulation of the “Copenhagen interpretation,” which became dominant in the 20th century. However, the persistent opposition of scientists like Einstein and Schrödinger inspired generations of physicists to seek a unification between quantum mechanics and relativity, culminating in new theories such as loop quantum gravity and string theory. Thus, the debate between realism and anti-realism remains alive, and philosophy continues to play a crucial role in exploring the new foundations of physics.
Many of the pioneers of quantum mechanics – notably Planck, Einstein, Bohr, de Broglie, Heisenberg, Schrodinger, Born, Jordan, Landé, Wigner, and London – were seriously concerned with philosophical problems. In each case one can ask a question of psychological and historical interest: was it a philosophical penchant which drew the investigator towards a kind of physics research which is linked to philosophy, or was it rather that the conceptual difficulties of fundamental physics pulled him willynilly into the labyrinth of philosophy? I shall not undertake to discuss this question, but shall cite an opinion of Peter Bergmann, which I find congenial: he learned from Einstein that “the theoretical physicist is … a philosopher in workingman's clothes” ([1], q. v.). The problems with which I am preoccupied concern the philosophical implications of quantum mechanics – either epistemological, bearing on the extent, validity, and character of human knowledge; or metaphysical, bearing on the character of reality. Although quantum mechanics is not a system of philosophy, one can wonder whether it is susceptible to coherent incorporation in a philosophical system. I propose to examine the thought of three masters of quantum mechanics – Bohr, Heisenberg, and Schrödinger – not with a critical or historical intention, but in hope of finding some enlightenment concerning the problems posed by contemporary physics. I can say in advance that enlightenment will continue to elude us; nevertheless, the ideas of Bohr, Heisenberg and Schrödinger are rich and evocative for new studies.