 Einstein’s lectures on relativity in Berlin in 1917–18, attended at the time by Reichenbach and a handful of others, provided a shock to Reichenbach’s viewpoint. The Theory of Relativity and A Priori Knowledge, published in 1920, is an attempt to identify neo-Kantian doctrines that must be abandoned and to articulate what can be salvaged. Twenty-five years before, in his dissertation published in 1897, Russell had undertaken a similar project in connection with non-Euclidean geometry, arguing that constant curvature is the geometrical synthetic a priori. In 1902, Poincaré’s Science and Hypothesis essentially supplemented Russell’s view with the opinion that the choice of constant curvature geometry is underdetermined; the choice of one such geometry rather than another can always be compensated by a change of physics to save the phenomena. Without mentioning Russell or Helmholtz, Reichenbach takes general relativity to have refuted both Poincaré’s geometrical conventionalism and Kant’s geometrical apriorism. Most of the book addresses general epistemological issues discussed above rather than issues about physics per se. 