Moritz Schlick’s interpretation of the causality principle is based on his understanding of quantum mechanics and on his conviction that quantum mechanics strongly supports an empiricist reading of causation in his sense. The present chapter compares the empiricist position held by Schlick with Bas van Fraassen’s more recent conception of constructive empiricism. It is pointed out that the development of philosophy of science from Schlick’s understanding of logical empiricism to constructive empiricism reflects a difference between the understanding of quantum mechanics endorsed by Schlick and the understanding that had been established by the time of van Fraassen’s writing.
Moritz Schlick’s interpretation of the causality principle is based on his understanding of quantum mechanics and on his conviction that quantum mechanics strongly supports an empiricist reading of causation in his sense. The present chapter compares the empiricist position held by Schlick with Bas van Fraassen’s more recent conception of constructive empiricism. It is pointed out that the development of philosophy of science from Schlick’s understanding of logical empiricism to constructive empiricism reflects a difference between the understanding of quantum mechanics endorsed by Schlick and the understanding that had been established by the time of van Fraassen’s writing.
Moritz Schlick’s interpretation of the causality principle is based on Schlick’s understanding of quantum mechanics and on his conviction that quantum mechanics strongly supports an empiricist reading of causation in his sense. The present paper compares the empiricist position held by Schlick with Bas van Fraassen’s more recent conception of constructive empiricism. It is pointed out that the development from Schlick’s understanding of logical empiricism to constructive empiricism reflects a difference between the understanding of quantum mechanics endorsed by Schlick and the understanding that had been established at the time of van Fraassen’s writing.
Quantum mechanics is a paradigmatic example of a scientific theory seemingly demanding ‘an interpretation’. What is it to ‘interpret’ a physical theory? Bas van Fraassen has recently argued that the attitude towards the task of interpreting science can be used to demarcate two otherwise similar epistemic stances: empiricism and naturalism. He claims that while empiricists are committed to the task of interpretation, naturalists cannot make sense of interpretation from outside the scientific theory. Naturalists, it seems, would have to be quietists about interpretation. Chapter 6 investigates in what form, if any, naturalists can make sense of the task of interpretation in the case of quantum mechanics. Doing so will shed light on the question whether interpretation of physical theories is a distinctively philosophical task, and what its purpose might be. It suggests that the aim of interpreting theories is to enhance our understanding, and that this task is not exclusively philosophical.
In this article I will focus on the debate on the causality principle that originated in the light of quantum mechanics concerning Moritz Schlick and Karl Popper. The discovery of quantum mechanics led to a broad debate on the interpretation of the principle of causality. Schlick proposed that it should be understood as an empirically verifiable postulate, and therefore with limits regarding causal indeterminacy in quantum physics. This approach had an influence on some scientists, especially Werner Heisenberg. However, Popper would develop a different way of understanding science because of the role played by unverifiable elements in theories that can nevertheless be falsified. It is precisely the discussion around the principle of causality that opens up different ways of understanding science. I will first try to analyse Schlick’s argument in the context of the debate that was taking place in the late 1920s in the light of the new quantum mechanics; secondly, I will look at the reception that Schlick’s idea of causality had in Heisenberg and the Copenhagen Interpretation; thirdly, I will analyse Popper’s argument against Schlick’s interpretation; finally, I will try to see the resonances of this debate in Heisenberg and other physicists.
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.
The discovery of quantum physics opened a broad debate on the epistemological status of the principle of causality. In this article, I analyze the problem of causality in Heisenberg by distinguishing two levels of philosophical explanation in his thought. As a philosopher of science, his understanding of causality is closely linked to Moritz Schlick, although he will later adopt a neo-Kantian view of the a priori. As a philosopher of nature, Heisenberg recovers the notion of potency to understand the wave function. My thesis is that this notion of potency could have allowed him to elaborate a realistic and nondeterministic theory of causality, but the identification of causality and determinism (in Schlick’s line) did not lead him to such a conclusion.
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.