Did Einstein Really Refute Kant? Space, Time, and the Relativity of the a priori

This article examines the epistemological status of space and time in relativistic physics by taking as its point of departure a tension explicitly acknowledged by Einstein himself: that of a mode of thought that appealed in turn to Mach’s radical empiricism, to an anti-positivism close to critical idealism, and ultimately to a philosophical “opportunism” that refused any stable doctrinal allegiance. This instability is interpreted not as a biographical inconsistency but as the symptom of a problem that has remained insufficiently thematized: the reference of spatiotemporal frameworks. Drawing on the writings of Einstein, Kant, and Mach, as well as Ernst Cassirer’s interpretation of them, the analysis reconstructs a two-level theory that distinguishes the general and abstract idea of space or time, given through the form of sensibility, from the concrete referential schemata through which that idea is applied, measured, and formalized. This distinction makes it possible to argue that the relativization of reference frames in physics does not conflict with the a priori character of space and time in Kant, provided that apriority is understood as a condition of the possibility of experience rather than as the rigid determination of a particular geometrical content. The article shows that the same argumentative structure accounts for the relativity of simultaneity and for the disagreement between Einstein and Bergson over the nature of time. It ultimately proposes that Einstein’s opportunism be read as the natural consequence of a position which, rejecting both naïve realism and thoroughgoing relativism, could find satisfaction in no established school. This article forms part of a broader project by the same author entitled Philosophy of Meaning, available on PhilPapers.