The Theory of Relativity and the Dispute for Interpretative Supremacy

This chapter moves the investigation from the physical description of relativity to its philosophical interpretation. Its thesis is that the same successful physical theory has sustained three coherent and mutually irreducible interpretations: neo-Kantian, logical-empiricist and scientific realism. The chapter first identifies the guiding question of each tradition and then reconstructs, as briefly as the argument allows, the historical dispute for interpretative supremacy over relativity: Natorp and Sellien held that Kant was unaffected; Schlick, that he was refuted; Cassirer and the early Reichenbach, that the a priori must be relativized; and the logical-empiricist settlement of the 1920s absorbed the constitutive a priori into convention. Friedman’s relativized a priori shows that the neo-Kantian option remains alive. The realist interpretation, historically the least explicit because it long remained the implicit attitude of physicists, is then reconstructed on equal terms: from Boltzmann, Planck and Minkowski, through Einstein’s empirical, holistic and realist position and the critical and structural realism of Schlick, Meyerson and Russell, to the scientific realism of Sellars, Putnam and Boyd and its debates on the conventionality of geometry and the ontology of spacetime. Scientific realism affirms that relativity refers to an independent physical reality but does not by itself fix the ontology of that reality; this openness is the point from which the BBMT bridge of Chapter 7 will start. On this basis the chapter compares how the three traditions interpret the two transversal principles established in Chapters 3 and 4. Causality appears as a constitutive condition of objective temporal order, as an empirical ordering supplemented by convention, or as an objective structure of spacetime; stationary action appears as a coordinating principle of law-formation, as an economical reformulation without surplus content, or as a deep structure of physical reality. The result is restricted to the philosophy of science: agreement on the physics does not produce agreement on its meaning. The hermeneutical classification of these interpretations is reserved for Chapter 8.