A Machian Interpretation of the Theory of Relativity? Joseph Petzoldt’s Reading of Einstein

Even though the relationship between Einstein and Mach is well studied, the literature on the topic often overlooks that Mach never provided an interpretation for the theory of relativity. Rather, it was Mach’s pupil Joseph Petzoldt who published several works to prove that Machian philosophy constituted the correct philosophical framework for the theory of relativity. The paper reconstructs Petzoldt’s philosophy and his interpretation of the theory of relativity, also showing how his conceptions sometimes differed from that of Mach. Thus, the study also explains why Einstein expressed a favorable opinion of Petzoldt's work. On the one hand, the overall Machian tone of Petzoldt’s philosophy resonated with Einstein’s own Machian perspective. On the other hand, Petzoldt had developed the notion of Eindeutigkeit, which tended towards a stronger determinism (different from Mach's Humean conception of causality), and Einstein appreciated this deterministic version of Mach’s thought.