Abstract

The theory of space-time developed in Kant’s Critique of Pure Reason and his Metaphysical Foundations of Natural Science is connected to Leonhard Euler’s proof of invariance under Galilean transformations in the “On Motion in General” of the latter’s 1736 Analytical Mechanics. It is argued that Kant, by using the Principle of Relativity that is the output of Euler’s proof as an input to his own proof of the kinematic parallelogram law, makes essential use of absolute simultaneity. This is why, in the Transcendental Aesthetic, he observes that “our theory of time explains as much a priori knowledge as the general theory of motion displays.” In conclusion, it is shown that the same proof-method, under a different definition of simultaneity, leads to the parallelogram law of the “Kinematic Part” of Einstein’s 1905 “On the Electrodynamics of Moving Bodies”.