The significance of absolute space and absolute motion in the Critical philosophy is clarified by analysis of relevant passages in Kant's Metaphysical Foundations of Natural Science. Newton's absolute space is rejected in favor of absolute space conceived of as an idea of reason serving to unify the infinity of possible relative kinematic spaces. On the other hand, something like newton's concept of absolute motion (e.g., in the case of rotation) is accepted by Kant under the heading of real - as (...) opposed to illusory - motion. (shrink)