 The role of the medium is not essential, but is only a kind of resistance, and thus motion in the void is both theoretically possible and confirmed by the observation of the spheres. Avempace contradicts Aristotle and advances a doctrine that Galileo will later prove to be  right.[22]  The similarity with Philoponus’ doctrine is clear, but an influence is not certain (Lettinck 1994: 549). Said El Bousklaoui shares the view that Avempace’s doctrine although similar to Philoponus’s it is not inherited from it (Bouskaloui 2020). Bousklaoui links the impetus theory to movement by itself, “spontaneously”, but this view needs further development.  