  In Proposition 4 Kant draws an important consequence from his characterization of repulsive forces, namely that matter is infinitely divisible (4:503). What is especially striking about this point is that it represents a significant departure from his own earlier Physical Monadology, where he had accepted attractive and repulsive forces, but denied the infinite divisibility of what ultimately constitutes matter, namely physical points or monads. It is true that part of Kant's rationale for his change of position on this point stems from the “critical turn” undertaken in the Critique of Pure Reason (and in its Second Antinomy in particular). For once one recognizes that both space and spatial properties such as divisibility are not properties of things in themselves but rather only appearances, one can reject the proposition that seems to necessitate the acceptance of simple substances, namely the idea that simple substances must precede the wholes they compose (4:506). However, Kant's proof also seems to depend, in its details, not merely on the idea that every space is filled by means of some repulsive force or other, but on the stronger claim that every space is divisible into smaller spaces that are filled by different repulsive forces.