 The temporal motion of a simple body in a vacuum is the most difficult to explain. In the opinion of Averroes, a simple body such as a piece of earth has an elementary form, prime matter, and different quantitative parts. Because form cannot resist matter, no resistance can come from its qualitative parts. But there can be resistance coming from its quantitative parts resisting one another. This time Kilvington uses Grosseteste’s idea, recognizing that the temporal motion of a simple body in a vacuum is possible due to the internal resistance that arises when the peripheral parts of a body that move along oblique lines resist its central parts moving along straight lines. Such an internal resistance produces motion, and does not impede; nevertheless, it guarantees temporal motion. Consequently, if a vacuum existed, the natural motion of a simple body would be possible. Moreover, the speed of such a motion would be the fastest, since there is no external resistance to be overcome (Jung-Palczewska 2002a: 169).