Ungrounded Dispositions in Quantum Mechanics

Mauro Dorato

Abstract. After some suggestions about how to clarify the confused metaphysical distinctions between dispositional and non-dispositional or categorical properties, I review some of the main interpretations of QM in order to show that – with the relevant exception of Bohm’s minimalist interpretation – quantum ontology is irreducibly dispositional. Such an irreducible character of dispositions must be explained differently in different interpretations, but the reducibility of the contextual properties in the case of Bohmian mechanics is guaranteed by the fact that the positions of particles play the role of the categorical basis, a role that in other interpretations cannot be filled by anything else. In Bohr’s and Everett-type interpretations, dispositionalism is instrumentalism in disguise.

Alexander H Klotz

CHRISTOF WETTERICH

William M. Simpson

The wave function of quantum mechanics can be understood in terms of the dispositional role it plays in the dynamics of a distribution of matter in three-dimensional space (or four-dimensional spacetime). There is more than one way, however, of specifying its dispositional role. This paper considers Suárez’s theory of ‘Bohmian dispositionalism’, in which the particles are endowed with their own ‘Bohmian dispositions’, and Simpson’s theory of ‘Cosmic Hylomorphism’, in which the particle configuration comprises a hylomorphic substance which has an intrinsic power. I argue that Bohmian dispositionalism fails to capture intuitively correct counterfactuals about what would happen in Small Worlds which have only a small number of particles, but that this problem is avoided by Cosmic Hylomorphism, in which the cosmic power manifests a teleological process.

Bruno Gnassounou, Max Kistler

Given the controversial status of the various interpretations of non-relativistic quantum mechanics (QM for short), it may seem crazy to use the philosophy of quantum physics to try to learn some lessons about the prevailing problems in the literature on dispositions and causal powers. However, such an attempt seems worthwhile for at least three reasons. The first is more internal to the philosophy of QM. Apart from a seminal paper by Robert Clifton and Constantine Pagonis (1995), who investigated the issue of dispositional properties in Bohmian mechanics, very little has been done to shed This neglect seems particularly surprising, especially if one considers that some of the founding fathers of quantum physics, notably Werner Heisenberg, have made direct reference to Aristotelian potentiae to refer to and interpret the elusive nature of the atomic and subatomic world ‘in se’, that is, before measurement: ‘Such a probability function [i.e. the statistical algorithm of quantum theory] combines objective and subjective elements. It contains statements on possibilities, or better tendencies (“potentiae” in Aristotelian philosophy), and such statements are completely objective, they don’t depend on any observer the passage from the “possible” to the Some years before, Henry Margenau3 had already characterized the properties of quantum systems as merely latent, in contrast to the properties intervening in the description of classical systems, which are always definite even when they are merely dispositional. Similarly, Karl Popper4 and Nicholas Maxwell5 have defended some sort of a propensity interpretation of probability, and a view of quantum reality essentially characterized by irreducibly probabilistic propensities. Influenced by this tradition, Michael Redhead’s influential textbook on the philosophy of QM distinguishes among three different interpretations of the theory, the second of which presupposes real propensities and potentialities and attributes to measurements the function of ‘converting latent values in possessed values’.6 Clearly, for this second interpretation to make less than an instrumentalistic sense, one needs to construe potentialities and dispositions as real properties of systems. Consequently, it seems important to try to get a firmer grasp of the sense in which QM might need irreducible dispositions to shed light on the nature of the properties of quantum systems before measurements, in particular when the state of such systems is not an eigenstate of the relevant physical observable.

William A. Ponce, Nicolas F. Raigoza