 Reichenbach’s discussion of space and time begins with a near irony. Having argued against Kant’s effort to justify the basics of Newtonian physics a priori, Reichenbach proceeds to argue that we can know almost a priori that Newtonian theory is false. For example, Newton does not distinguish between the length of a moving segment and its length at rest, but according to Reichenbach, this is an a priori mistake: “the measurement of a segment with a measuring rod that moves relative to it requires the formulation of a new concept…The length of a moving line-segment is the distance between simultaneous positions of its endpoints.” (p. 155) And further: “It follows from the nature of the extended concept of length that the length of a moving segment is generally different from its rest-length.” To say which is the true length is “nonsense” (p. 157). Thus is Newton refuted. 