2010 Meeting of the Canadian Society for the History and Philosophy of Science - 28-29 May 2010, Concordia, Montreal

28 May 2010, 4:15-6:00 PM
Room MB 2-435 Session B4

PANEL dedicated to the retirement of Mario Bunge: Realism and determinism in Physics/ Réalisme et déterminisme en physique

PANELISTS (in order of presentations): Mario Bunge, Vesselin Petkov, Louis Vervoort, Laurent Jodoin (please click on thumbnail)

Richard Arthur's allocution for the retirement of Mario Bunge

Mario Bunge: Is quantum mechanics indeterministic?
  Nearly everyone believes that the quantum theory is indeterministic. The reason is that its state function is interpreted as a probability density. However, there are reasons to believe that this conclusion was hasty and simplistic. The aims of this paper are to argue for the following theses. First, the birth of statistical physics in the nineteenth century suggested that, although causal determinism à la Laplace is no longer tenable, a broader conception of determinism, as lawfulness plus non-creation ex nihilo, is defensible. Second, standard quantum mechanics has two aspects on the same footing: a causal aspect symbolized by the hamiltonian, and a stochastic aspect represented by the state function. For example, any model of a scattering experiment includes both the force that scatters the incident particles, and the state function that describes the resulting scattering. Third, Bohm’s 1951 theory was not thoroughly causal because it retained the state function as basic or primitive. One moral of this story is that the world is objectively half-causal and half-random. Another moral is that the determinism problem must be distinguished from the question of realism. Even if causality were totally absent, as Hume thought, the external world would exist on its own: if it did not, it would be senseless to explore it.

Vesselin Petkov: Realism and explanation – the necessary common ground for a genuinely fruitful interaction between science and philosophy of science
  The collaboration between scientists and philosophers of science is not what it should be. Although there are various reasons for that I suggest that sharing an explicit realistic view on the nature of scientific theories and a comprehensive view on scientific explanation can provide the minimal common ground for collaboration between scientists and philosophers of science that can produce tangible results. It is usually assumed that scientists are overwhelmingly realists but this is not always the case, especially in fundamental physics, since physicists often doubt whether theoretical concepts reflect anything real. This tendency in theoretical physics is best demonstrated in a recent article by N. David Mermin in which he insisted on not considering the “most successful abstractions to be real properties of our world.” To demonstrate how productive the interaction of scientists and philosophers of science can be, I will discuss two examples: (i) endurantism versus perdurantism (how physicists can help philosophers resolve a debate), and (ii) the nature of the quantum object (how philosophers of science should abandon their secondary role in the pursuit of scientific knowledge and start actively participating in the advancement of science by carrying out rigorous conceptual analyses of open questions in science).

Louis Vervoort: A frequentist interpretation of probability
  In the following we propose an interpretation of probability that aims at rendering explicit the fundamental notions of the frequency interpretation of Venn, von Mises, and others. We will argue that (objective) probability can only be defined for events that can be repeated in similar conditions, and that exhibit ‘frequency stabilization’. We will partition probabilistic systems into object, environment, and probing subsystem, and show that such partitioning allows to solve paradoxes. By the same token, we will be able to derive a definition of what ‘similar events’ are – a problematic concept in traditional interpretations -, and point out an analogy between quantum systems and classical ones.

Laurent Jodoin: Mesure quantique et entropie / Quantum measurement and entropy
  L’entropie thermodynamique implique une compatibilité macroscopique entre différents états microscopiques (Tolman 1938). L’entropie quantique est liée au couplage avec l’environnement, c’est-à-dire l’appareil de mesure (Jancel 1963). Mais la réponse apportée à l’interaction système-appareil de mesure par la thermodynamique, d’une part, et par la mécanique quantique, d’autre part, est différente : l’une prédit une diminution et l’autre une augmentation de l’entropie. Ainsi, l’identification de l’entropie thermodynamique et de l’entropie quantique selon l’interprétation de von Neumann est mal fondée, voire erronée (Shenker 1999). En effet, cette identification implique la possibilité (absurde) d’une machine à mouvement perpétuel. Or, la conception de l’entropie quantique selon l’interprétation de von Neumann implique la matrice densité r qui représente « toute l’information disponible sur le système » – et cette information ne peut être « ignorée ». Il est soutenu ici que cela pose des problèmes à l’interprétation subjective de la théorie de la mesure en mécanique quantique.

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