Causality, realism and the two strands of Boltzmann's legacy (1896 - 1936)
Michael Stöltzner
My thesis investigates a debate between Vienna and Berlin about the view that the basic laws of nature are genuinely indeterministic that started long before the advent of quantum mechanics. It involved two different readings of Ludwig Boltzmann's legacy statistical mechanics and two different answers to how causality and ontology ought to be combined. Having adopted Ernst Mach's weak notion of causality, the local Viennese tradition could more easily contemplate ontologies for irreducibly statistical laws that were different from classical physics, while the Berlin tradition departed from Planck's reading of the Kantian tradition, according to which strictly deterministic laws represented an indispensable basis even for probabilistic theories.\nVienna Indeterminism, as I shall call the first reading, became characteristic for a series of physicist-philosophers connected to the Institute of Physics at the University of Vienna, among them Franz Serafin Exner, Erwin Schrödinger, Philipp Frank and Richard von Mises. It involved the acceptance of the highly improbable events admitted by the second law of thermodynamics, an assent to Mach's definition of causality in terms of functional dependencies, an empiricist shift of the burden of proof on the determinist's shoulders, and the adoption of the relative frequency interpretation of probability. Planck and his student Moritz Schlick initially rejected all of these creeds.\nWhile the Viennese reading of Boltzmann's legacy made it possible to accept probabilistic laws as genuine laws years before the advent of quantum mechanics, Schlick had to take a strictly verificationist tack to reconcile his views on probability with the failure of a Kant-inspired notion of causality enforced by the changes in physics. Until his death however, Schlick remained committed to the Spielraum interpretation of Johannes von Kries, compensating his qualified acceptance of indeterminism with an emphasis on the limits of language that were enforced by Heisenberg's uncertainty relations.\nIn view of claims that scientists' abandonment of determinism and causality was triggered, or at least enhanced, by external factors, among them the anti-scientific Weimar milieu and Bohr's power politics, the reconstruction of the philosophical debates between Vienna and Berlin requires historical contextualization. To this end, I initially recapitulate the Forman thesis and the discussions ensuing from it. Most important among them are the recent books of Cushing and Beller that, rejecting Forman's strong claims, nevertheless deny any constructive influence of the scientific aspirations of German physicists on the philosophical debates about causality and indeterminism in the 1920s.\nAgainst this picture, I argue that the philosophical aspirations of physicist-philosophers were rather genuine and followed influential role models, among them Helmholtz and Mach. They represent a characteristic trait of the German-speaking scientific world and were expressed in academic addresses and in the publication of popular writings. After 1913, this philosophical discourse was conducted, to an increasing extent, on the pages of Die Naturwissenschaften. In a separate chapter, I study the role of philosophical and cultural matters in this journal, which can hardly be separated from the personality of its founding editor Arnold Berliner. At about 1930, this discourse among physicist-philosophers partly merged into scientific philosophy, as conducted by Logical Empiricists, and the newly founded Erkenntnis.\nOne of the characteristic features of the discourse among physicist-philosophers was that they were not strictly indebted to philosophical schools but rather willing to form strategic alliances. Such alliances emphasized one philosophical aspect that was considered pivotal at the time which other features, often expressing severe disagreements of content, were played down. This process can be witnessed at the end of the discussion between the Viennese and the Berliners in the 1930s, at a time when Schlick had already become the center of the Vienna Circle. Being confronted with a plethora of "metaphysical" misinterpretations and having taken the linguistic turn, Frank and Schlick formed a strategic alliance on the 1936 Copenhagen Congress for the Unity of Science. It brought them into opposition with Schrödinger's quest for a modification of quantum mechanics, although Schrödinger continued to be a staunch advocate of indeterminism. This year thus signifies the end of the coherence of Vienna Indeterminism, a tradition that reaches back to the publication of Boltzmann's Lectures of Gas Theory.
•Jan 1, 2003•6 citations