This article deals with the Copenhagen interpretation of quantum mechanics and its epistemological discussion by Ernst Cassirer and Richard Hönigswald. The starting point is Cassirer's treatise Determinism and Indeterminism in Modern Physics, published in Stockholm. Both philosophers and several physicists were involved in the subsequent exchange of letters. From a physical point of view, the Copenhagen interpretation was particularly criticised by v. Laue and Einstein. Both demanded a revision of the foundations of quantum mechanics or a critical examination of essential physical concepts. The epistemological implications of the Copenhagen interpretation were rejected, in particular that the interactions between observation, the observed and the observer in quantum physics experiments should lead to a renunciation of the concept of causality or an objectively unambiguous description of natural processes. Cassirer argues here that quantum mechanics fulfils the epistemological requirement of transforming ontological “concepts of things” into epistemological concepts of relations and is therefore compatible with the neo-critical approach he advocates. At the same time, Hönigswald was working on two major treatises on the structure of physics and the concept of causality. Here he undertakes an epistemological foundation of physics as a whole. A transcendental foundation of the concept of experience and its specifications in principles such as contemplation, observation or experiment appears to be called for. Hönigswald therefore essentially rejects the Copenhagen interpretation, as it draws epistemological consequences by physical means and thus inadmissibly reverses the transcendentally necessary relations of justification. These arguments are examined and could be used for a current discussion on the epistemological foundations of quantum mechanics and physics as a whole. A post-Neo-Kantian, transcendental philosophical foundation of scientific knowledge, especially of modern physics, seems possible and necessary.
This article deals with the Copenhagen interpretation of quantum mechanics and its epistemological discussion by Ernst Cassirer and Richard Hönigswald. The starting point is Cassirer's treatise Determinism and Indeterminism in Modern Physics, published in Stockholm. Both philosophers and several physicists were involved in the subsequent exchange of letters. From a physical point of view, the Copenhagen interpretation was particularly criticised by v. Laue and Einstein. Both demanded a revision of the foundations of quantum mechanics or a critical examination of essential physical concepts. The epistemological implications of the Copenhagen interpretation were rejected, in particular that the interactions between observation, the observed and the observer in quantum physics experiments should lead to a renunciation of the concept of causality or an objectively unambiguous description of natural processes. Cassirer argues here that quantum mechanics fulfils the epistemological requirement of transforming ontological “concepts of things” into epistemological concepts of relations and is therefore compatible with the neo-critical approach he advocates. At the same time, Hönigswald was working on two major treatises on the structure of physics and the concept of causality. Here he undertakes an epistemological foundation of physics as a whole. A transcendental foundation of the concept of experience and its specifications in principles such as contemplation, observation or experiment appears to be called for. Hönigswald therefore essentially rejects the Copenhagen interpretation, as it draws epistemological consequences by physical means and thus inadmissibly reverses the transcendentally necessary relations of justification. These arguments are examined and could be used for a current discussion on the epistemological foundations of quantum mechanics and physics as a whole. A post-Neo-Kantian, transcendental philosophical foundation of scientific knowledge, especially of modern physics, seems possible and necessary.
This article revisits Ernst Cassirer’s philosophy of quantum physics as developed in his last epistemological work Determinismus und Indeterminismus in der modernen Physik (1936), in particular his main thesis which posits that causality can be maintained in quantum theory, provided its object is re-conceptualized. I study the ranking of the principle of causality in Cassirer’s hierarchy of physical knowledge, and show that its role is both constitutive and regulatory. This is linked to Cassirer’s rejection of the Kantian faculty of intuition. I review other characteristics of Cassirer’s conception of physical theory (in particular holism) and analyze in detail how Cassirer manages to shift from an observationalist interpretation of Heisenberg’s relations (negative, as a lack of information) to a constitutive interpretation (positive, as a new definition of the object) of these relations. I conclude by showing that Cassirer’s interpretation of quantum theory is more promising than Friedman’s Kant-inspired « relativized a priori » conception.
This chapter repeats for quantum mechanics the comparison carried out for relativity in Chapter 5. Its thesis is that the same three interpretative families, neo-Kantian, empiricist and scientific realist, reappear in the philosophical reception of quantum mechanics, but in a more radical form, because the dispute now reaches the meaning of the quantum state, of probability and of measurement. The chapter first identifies what the formalism established in Chapter 4 leaves open and treats the Copenhagen framework as a point of departure rather than a unified doctrine. It then reconstructs the neo-Kantian interpretation (the Kantian affinities of Bohr’s complementarity, Cassirer, Grete Hermann and contemporary transcendental perspectives), the empiricist interpretation (Heisenberg’s observability principle, instrumentalism, Schlick, Frank, Reichenbach and van Fraassen’s constructive empiricism) and, on equal terms, the realist interpretation: Einstein and the EPR argument, Popper’s propensities, the de Broglie–Bohm theory, Bell’s beables and local causality, realist modal interpretations, and the Everett and collapse programmes. The realist family is the most developed of the three in quantum mechanics, but it is also internally plural: it affirms that the theory refers to a mind-independent reality while disagreeing about whether that reality consists of particles, fields, propensities, branching worlds or definite and possible properties. On this basis the chapter compares the three interpretations of causality and of stationary action. Causality appears as a relativized condition of objective description, as a statistical relation without surplus content, or as an objective but non-local structure; stationary action appears as a coordination axiom of quantum dynamics, as an empirically equivalent formulation, or as a real dynamical structure that in Bohm’s theory directly guides motion. The result confirms the pattern of Chapter 5 and identifies the precise point, the relation between quantum possibility and actuality, from which the BBMT bridge of Chapter 7 will start.
Ernst Cassirer's Determinism and Indeterminism in Modern Physics (DI; Cassirer, 1936/1956) constitutes a major but systematically overlooked transformation in the philosophy of quantum mechanics. Against interpretations that treat the text as a late application of his earlier structuralism, this article argues that quantum mechanics forces a fundamental reconstruction of causal order and scientific objectivity. Following the dissolution of Laplacean determinism, causality is no longer directed at ‘things’ in the world, but functions as a regulative demand that experience be rendered intelligible. Accordingly, causal order does not map to a pre-given reality but is progressively constituted from within experience through recursive processes of functional co-ordination (Zuordnung). This reconstruction culminates in a participatory account of objectivity organised through three mutually conditioning levels – measurements, laws, and principles. The upshot is that physical objects emerge as invariant nodes within relational structure; objects are fixed as objective relations. On this basis, the article shows that neither epistemic nor ontic structural realism adequately captures Cassirer's position and develops in response a provisional functional ontology in which a co-ordinating subject and an indeterminate relational domain jointly constitute the transcendental conditions of objectivity. The article concludes by situating DI within a broader participatory tradition in the foundations of physics, arguing that Cassirer's recursive and observer-dependent account of objectivity anticipates key developments in second-order cybernetics and participatory approaches to quantum mechanics.
This work presents a historical-epistemological analysis of the foundations of quantum mechanics. From a philosophical point of view, the relationships between quantum mechanics and scientific realism are highlighted, as well as the influence of the neo-positivist philosophy of the first decades of the 20th century. The great significance of measurement in the context of quantum mechanics is underlined, as an essential element in providing a coherent description of reality moving from the microcosm to the macrocosm, as well as the role that the measurement apparatus and the consciousness of the observer assume during the act of measurement, the ontological problem, the problem of the objectification of the wave function and the problem of the definition of discernibility. This is followed by an overview of the most important alternative proposals to the standard interpretation (Copenhagen interpretation), with particular reference to hidden variable theories, and other alternatives to standard quantum mechanics that profoundly modify the vision of reality, such as the Everett’s many-worlds theory, the QBism, the unified holistic approach.
The Copenhagen interpretation of quantum theory is investigated from a philosophical point of view. It is justified the opinion that the philosophical attitude the Copenhagen interpretation is based on is in principle inevitable for a real comprehension of quantum theory. This attitude is mainly related to epistemological arguments. However, the measurement problem often seems not to be treated clearly enough within the interpretation. By referring to the property of the necessity to use macroscopic measurement instruments obeying classical concepts it is made the attempt to solve the measurement problem. According to this consideration the indeterministic character of quantum theory seems to have its origin in a lack of knowledge and thus it appears in a similar but more principle way than in statistical mechanics. It is emphasized the ontological character of the uncertainty relation and the related non locality of quantum theory suggesting that the existence of a position space is not as fundamental as the assumptions of general quantum theory.
This article examines the epistemological views of key quantum physicists of the Copenhagen circle (Niels Bohr, Werner Heisenberg and Léon Rosenfeld). The discussion begins with a presentation of their conception of measurement, indeterminacy and complementarity, and goes on to focus on their views regarding the nature of being and knowledge. The author identifies the basic areas of consensus in the Copenhagen circle as well as the disagreements and disputes that arose between its members. Three main points are argued: (1) The fundamental epistemological consensus in the group was that subject and object are inseparable; that the subject participates in the formation of images of reality, which are multiple and depend on how the subject is concretely constituted historically; the disagreements within the group did not arise with logical inevitability from the principles of quantum mechanics but largely stemmed from ideological clash in the Cold War context. (2) Being linked to specific configurations of the subjects, knowledge is always relative; but it does not follow that knowledge is illusory or inadequate; on the contrary, it is the pretension of attaining the ultimate nature of things “in themselves” that leads to devaluation of any concrete knowledge. (3) The world is something external, generally independent of our desires and will, but at the same time is constructed as concrete objects through the specific configuration of each concrete subject.