 Like most medieval natural philosophers, Kilvington accepts Aristotle’s general rules for change to occur, stating that: 1) there cannot be a change without an active capacity (virtus motiva) and a passive capacity (virtus resistiva), because without resistance, motion would not be temporal; 2) the proportion of an active capacity to a passive one must be the proportion of maioris inequalitatis, that is, it must be greater than one. These conditions are sufficient for the occurrence of natural local motion. Kilvington is primarily interested in the description of the natural motions of a mixed and simple body both in a medium and in a vacuum. In his discussion of various motions, such as the motion of the Earth or the motion of weights, he often relies on the laws of statics presented in the works of Jordanus de Nemore, Archimedes, and Euclid (DM: 221, 223, 239–40).