Abstract

The principles of Kant's pure physics (conservation of quantity of matter, inertia, equality of action and reaction) are a priori in the same sense as are the principles of the understanding. We account for the empirical content of physics by showing that the pure principles operate as rules for generating wellformed empirical descriptions, and as rules for analysis of motion. The relationship between the metaphysics of matter and empirical descriptions is neither deductive, nor as loose as Buchdahl alleges. Belief that a priori principles will apply to empirical cases requires acceptance of methodological presuppositions, chief among which is the principle of affinity.