Moritz Schlick's reading of Poincaré's theory of relativity

Résumé En

My discussion of Schlick's view of Poincaré's theory begins with a review of the difference between Einstein's and Poincaré's theories, that turns on the form of light-waves as judged by observers in inertial frames of reference. I summarize the evolution of Poincaré's philosophy of geometry in the early years of relativity theory, which Schlick ignored throughout his life, and in the second section of the paper, I recall Schlick's discussion of Poincaré's views on the relativity of space, in which Schlick focused on similitude relations, at the expense of relations of covariance. I then take up Lindemann's preface to the English translation of Schlick's Raum und Zeit in der gegenwärtigen Physik, where the issue of the shape of light-shells in inertial frames is raised. It is this very issue, I suggest, which distinguished most sharply Poincaré's theory of relativity from Einstein's special theory of relativity, and may have prompted Schlick to move away from Poincaré's neo-Kantian conventionalism towards an Einsteinian empiricism with constitutive principles.