Density, Dynamics, Mechanics

As Kant shows, the dynamic forces Repulsion and Attraction combine as bodies of infinite possible degrees of density, ranging from absolutely solid, to absolutely empty.  In contrast, the bodies that populate fields of mechanical causality are all absolutely solid, separated by absolutely empty spaces.  Furthermore, Newton's 2nd Law of Motion, holds only for absolutely solid bodies, for, e. g., when impacted upon, a body of lesser density might get smashed and remain where it is, thereby violating the Force-Acceleration correspondence entailed by that Law.  Thus, Mechanics is derived from Dynamics, as a special case of the latter, a relation that is implicit, but remains underdeveloped, in Kant's classifications of the natural sciences.