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 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.
Cet article revient sur la philosophie de la physique quantique d’Ernst Cassirer telle que développée dans son dernier ouvrage épistémologique Determinismus und Indeterminismus in der modernen Physik (1936), et sa thèse principale selon laquelle la causalité est conservée dans la théorie quantique, moyennant une re-conceptualisation de son objet. Il étudie la place du principe de causalité dans la hiérarchie de la connaissance physique selon Cassirer, et montre son rôle à la fois constitutif et régulateur, qui est lié à la disparition de la faculté kantienne de l’intuition chez Cassirer. Il passe en revue d’autres caractéristiques (holisme notamment) de la conception cassirérienne de la théorie physique. Il revient en détail sur la manière dont Cassirer parvient à passer d’une interprétation observationnaliste (négative, en tant que manque d’information) à une interprétation constitutive (positive, en tant que nouvelle définition de l’objet) des relations de Heisenberg. Il conclut avec le caractère prometteur de la conception de Cassirer pour faire droit à la théorie quantique, par rapport à une conception du type « relativized a priori » à la Friedman-Kant.
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.
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.
Determinismus und Indeterminismus in der modernen Physik (DI) is one of Cassirer’s least known and studied works, despite his own assessment as “one of his most important achievements” (Gawronsky 1949, 29). A prominent theme locates quantum mechanics as a yet further step of the tendency within physical theory towards the purely functional theory of the concept and functional characterization of objectivity. In this respect DI can be considered an “update”, like the earlier monograph Zur Einsteinschen Relativitätstheorie: Erkenntnistheoretische Betrachtungen (1921), to Substanzbegriff und Funktionsbegriff (1910), a seminal work considering only classical and pre-relativistic physics. But how does DI cohere with the three volumes of The Philosophy of Symbolic Forms (1923–29) providing a systematic survey of symbolic meanings in diverse aspects of culture, each with its own mode of “objectification” via self-created signs and images? Cassirer’s “phenomenology of cognition” via distinct types of symbolic form locates Dirac’s Principles of Quantum Mechanics (1930) as an exemplar within physical theory of purely symbolic thought, a realm of pure relations and their correlated meanings. In particular, Dirac’s characterization of the new notion of “physical state” in quantum mechanics by a “symbolic algebra of observables” severed from particular representations points to a limiting pole of the Bedeutungsfunktion, the third and highest mode of symbolic formation.
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’.
This paper compares Cassirer´s and Bohr´s views on symbolic knowledge in quantum physics. Although both of them consider quantum physics as symbolic knowledge, for Cassirer this amounts to a complete renunciation to intuition in quantum physics, while according to Bohr only spatio-temporal images may provide the mathematical formalism of the theory with physical reference. We show the Kantian roots of Bohr´s position and we claim that his Kantian concept of symbol enables Bohr to account for the sensible content of quantum theory as well as for its systematic relation to classical physics.