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Conférence de Roberto Angeloni


For a neo-Kantian interpretation of Niels Bohr’s philosophy of physics

par Roberto ANGELONI,

Mercredi 11 juin 2014 , 15:00, salle Kasimir Malevitch, 483A
Université Paris Diderot

In the first few decades of the twentieth century, physics underwent a revolution, as the theory of quantum mechanics, formulated during these years, replaced classical mechanics as the framework theory of physics. Quantum mechanics is an empirically successful theory that has been the springboard for substantial advances in theoretical physics and in technological applications, and promises more innovations to come, as exhibited by the burgeoning field of quantum information. Yet, in spite of this success, there is not, and never has been, consensus on how to understand the conceptual changes that the quantum revolution has brought. The project I want to carry on seeks deeper understanding of the conceptual shift from classical to quantum mechanics via a re-examination, in light of recent philosophical work, of the thought of Niels Bohr, a physicist who was a key figure in the creation of the theory, and who struggled mightily to understand the implications of the new physics. Specifically, this project aims at developing a neo-Kantian reading of Niels Bohr’s interpretation of quantum mechanics. To this end, I shall make use of the dynamical Kantianism developed by Michael Friedman, and Ernst Cassirer’s philosophy of symbolic forms.
In the eighteenth century, Immanuel Kant saw Newton’s laws of motion and gravitation as the ultimate and definitive stage of science. On Kant’s view, aspects of Newtonian physics—in particular, Euclidean geometry as the geometry of physical space, and deterministic laws of nature— took on an a priori status ; that is, it was thought that they could be justified independently of experience. According to Kant, this was because they formed conditions for any possible knowledge.
At the turn of the twentieth century, changes in physics cast doubt on some of these aspects of the Newtonian framework and, as a consequence, the Kantian philosophy. Einstein’s special theory of relativity suggested revisions of our concepts of space and time, and his general theory of relativity took this further, invoking non-Euclidean geometries. The discovery of the quantum of action also seemed irreconcilable with a Newtonian framework. Some philosophers, rather than abandoning the Kantian philosophy entirely, sought to modify it. Among them was Ernst Cassirer, who held that the objectivity of knowledge consists foremost in the correlation between procedures of observation and empirical data. In this view, the concept of function becomes central. Michael Friedman built on the work of Cassirer, and developed a dynamical Kantianism, in which the a priori becomes relativized. According to Friedman (and to Jan Faye, 2008), the discontinuity of the black body spectrum was considered by Bohr as a well-established empirical fact, which was elevated to a priori principle in his model of the atom. From then on, a continuous struggle began of enlarging the model to deal with atoms with higher numbers and to reach a proper theory, which could explain the dynamics of elementary particles.
Starting from Friedman’s considerations, I will take into account Planck’s quantum of action in its possible transition from empirical element to constitutive a priori principle in the successive stages of development of the quantum theory. The philosophical relevance of a constitutive a priori principle during scientific transitions may be a stronger explicative keyword in the foundation of quantum mechanics. It is here evident that this project also will serve the philosophical-historiographical purpose to investigate what kind of conceptual changes occurred (if any) in the quantum theory. Moreover, the application of the neo-Kantian framework will allow the evaluation of such method of historiographical analysis.

Salle Malevitch, 483A, bâtiment Condorcet,
4, rue Elsa Morante, 75013 Paris.
Métro ligne 14 / Station : Bibliothèque François Mitterrand
Métro ligne 6 / Station : Quai de la Gare
RER C / Station : Bibliothèque François Mitterrand
Bus 64 / Arrêt : Tolbiac-Bibliothèque François Mitterrand
Bus 62 & 89 / Arrêt : Avenue de France ou Bibliothèque François Mitterrand (terminus)
Bus 325 / Arrêt : Watt.

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