Kant's analysis of scientific knowledge – as articulated especially in his Metaphysical Foundations of Natural Science of 1786– is based on a sharp distinction between “pure” and “empirical” parts. The pure part of scientific knowledge consists of physical geometry (which, for Kant, is of course necessarily Euclidean geometry), more generally, the totality of applied mathematics presupposed by Newtonian physics (viz., classical analysis), Galilean kinematics (the classical velocity addition law), and the Newtonian laws of motion. In short, the entire spatiotemporal framework of Newtonian physics-what we now call the structure of Newtonian space-time – belongs to the pure part of natural science. The empirical part then consists of specific laws of nature formulated within this antecedently presupposed framework: for example, and especially, the law of universal gravitation and, more generally, the various specific force laws that can be formulated in the context of the Newtonian laws of motion.

Kant holds that the pure part of scientific knowledge consists entirely of synthetic a priori judgments. It does not represent merely conceptual knowledge but rather results from applying the conceptual faculty of pure understanding to the distinct sensible faculty of pure intuition. (This is what Kant calls the “schematism” of the pure concepts of the understanding.) The synthetic a priori judgments belonging to the pure part of scientific knowledge then represent the conditions of possibility of the empirical part: the former must be in place before the latter have well-defined meaning and truth value (“relation to an object”) in the first place.