With the emergence of quantum physics in the 1920s, the major philosophical question was, do the unobservables in quantum system have ontological status or are mere instruments for scientific prediction? The Copenhagen interpretation developed an instrumentalist thesis, contending that the unobservables are tools for making predictions concerning the observables. Thus, we cannot have knowledge of the quantum particles. However, Popper attempts a realist and an objective interpretation. As such, he criticizes the Copenhagen interpretation, developing the propensity view, which accords ontological status to subatomic particles. The main thrust of our argument in this paper is that by replacing probability possibilities with propensities, Popper positions himself as a proponent of the metaphysics of modality. It is then our objective to establish the parallelism between Popper’s Propensity Interpretation and Modal Metaphysics. To establish this contention we proceeded analytically: firstly by situating the seismic shift from macro to quantum physics, secondly by examining Popper’s critique of the Copenhagen Interpretation and thirdly by attempting a demonstration of the correlation between Popper’s propensity interpretation and modal metaphysics. The merit of this paper resides in its elucidation of the importance of metaphysics in science. It is a double challenge at the same time for antimetaphysical philosophy of science and for antiscientific metaphysics, to rethink the relationship between Metaphysics and science and invest in finding how both disciplines nurture each other. Finally, it is hoped that policy makers in Philosphy and science uses our findings to revamp the conceptualisation and practice of interdisciplinarity.
With the emergence of quantum physics in the 1920s, the major philosophical question was, do the unobservables in quantum system have ontological status or are mere instruments for scientific prediction? The Copenhagen interpretation developed an instrumentalist thesis, contending that the unobservables are tools for making predictions concerning the observables. Thus, we cannot have knowledge of the quantum particles. However, Popper attempts a realist and an objective interpretation. As such, he criticizes the Copenhagen interpretation, developing the propensity view, which accords ontological status to subatomic particles. The main thrust of our argument in this paper is that by replacing probability possibilities with propensities, Popper positions himself as a proponent of the metaphysics of modality. It is then our objective to establish the parallelism between Popper’s Propensity Interpretation and Modal Metaphysics. To establish this contention we proceeded analytically: firstly by situating the seismic shift from macro to quantum physics, secondly by examining Popper’s critique of the Copenhagen Interpretation and thirdly by attempting a demonstration of the correlation between Popper’s propensity interpretation and modal metaphysics. The merit of this paper resides in its elucidation of the importance of metaphysics in science. It is a double challenge at the same time for antimetaphysical philosophy of science and for antiscientific metaphysics, to rethink the relationship between Metaphysics and science and invest in finding how both disciplines nurture each other. Finally, it is hoped that policy makers in Philosphy and science uses our findings to revamp the conceptualisation and practice of interdisciplinarity.
Popper's program in the foundations of quantum mechanics defending objectivity and realism developed out of a profound dissatisfaction with the point of view associated with Bohr, which is usually designated the Copenhagen interpretation. Here I will argue that while Popper's aim is a noble one, his program does not succeed on two counts: he does not succeed in showing that Bohr's philosophy must be rejected as a variety of subjectivism, and his alternative interpretation of indeterminacy rests on a highly questionable assumption according to which simultaneously precise conjugate parameters are possible. Nevertheless I like Popper's propensity interpretation of probability and think that the propensity idea deserves further research. Quanta 2012; 1: 33–57.
Scientific realism does not view theoretical terms as mere instruments of experimental predictions; it grants referential status to natural kind terms with 'epistemic access' and view scientific theories and terms as corresponding to physical phenomena and entities which exist independently of observation, and as thereby being the source of objective -approximate and not absolute- knowledge of the physical realm. As a result, scientific realism is accused of ontologising the unobservables. Against this charge, scientific realism posits the idea of the dialectical relation between theoretical terms referring to the unobservables and scientific methods. The second argument made by realism is the ‘no miracle’ thesis. These arguments stand challenged by the Copenhagen interpretation of quantum mechanics. The aim of the paper is to examine the relevance of the two arguments of scientific realism in countering the idea that the existence of quantum states in the microphysical world renders realism obsolete.
Traditionally, to be a realist about something means believing in the independent existence of that something. In this line of thought, a scientific realist is someone who believes in the objective existence of the entities postulated by our best scientific theories. In metaphysical terms, what does that mean? In ontological terms, i.e., in terms about what exists, scientific realism can be understood as involving the adoption of an ontology that is scientifically informed. But according to some philosophers, the realistic attitude must go beyond ontology. The way in which this requirement has been understood involves providing a metaphysics for the entities postulated by science, that is, answering questions about the nature of what ontology admits to exist. We discuss how two fashionable approaches face the challenge of providing a metaphysics for science: a form of naturalism and the Viking/Toolbox approach. Finally, we present a third way, which adopts the best of both approaches: the meta-Popperian method, which focuses on discarding the wrong alternatives, or better saying, the metaphysical profiles incompatible with certain theories. We present the meta-Popperian method, a metametaphysical method capable of objectively assessing which metaphysical profiles are incompatible with certain scientific theories. For this, we will use quantum mechanics as a case study, presenting some previously obtained results. As our focus is on methodological questions about the relationship between metaphysics and science; with this method, we can see how science can be used to avoid error in metaphysical issues. In our opinion, this would be a way to develop a productive relationship between science and metaphysics.
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.
INTRODUCTION In his essay ‘Quantum Mechanics Without “the Observer”’ (in [20], 7–44), Popper criticizes the Copenhagen Interpretation and suggests construing the quantum theory as a ‘generalization of classical statistical mechanics’ ([20], 16). The uncertainty relations, he says, set ‘limits to the statistical dispersion … of the results of sequences of experiments’ ([20], 20) and not to what can be said about individual systems. Some strange features of orthodox microphysics are due either to a misinterpretation of probability, involving some ‘very simple mistakes’ ([20], 42); or else they are a straightforward consequence of the fact that the quantum theory is a statistical theory. For example, ‘the reduction of the wave packet … has nothing to do with quantum theory: it is a trivial feature of probability theory’ ([20], 37). The idea of probability that is presupposed in all these arguments, however, is Popper's propensity interpretation. Adopting this interpretation suffices for making clear what the quantum theory really is: a ‘generalization of classical statistical mechanics’ ([20], 16). This is Popper's position as I understand it. This position, it seems to me, is attractive enough as long as one does not carry the analysis too far. But it breaks down when confronted with all the facts which Bohr wanted to take into account. Altogether Popper's criticism and his alternative proposals once more reveal the strong points of the Copenhagen philosophy, and especially of the ideas of Niels Bohr. Today it is very difficult to find a satisfactory account of these ideas.