The present paper seeks to take up the suggestive thesis of Sorabji and Dales 011 the true origin of the arguments against the eternity of the world put forward by Bonaventure in his Commentary on the Sentences. This thesis maintains that the arguments presented by Bonaventure based on paradoxes about the infinite would not be his, but would come from a long and so far little known tradition of thought that goes back to John Philoponus, a Christian philosopher of the sixth century A.D. who would have formulated for the first time a defense of the ex nihilo creation of the world and its temporal beginning by turning around the Aristotelian arguments about the infinite. In order to test this thesis, we will briefly investigate the vehicle of transmission of Philoponus's arguments to Bonaventure in the 13th century, probably Arab and Jewish sources from the early Middle Ages, and -later- to start a comparative study between some relevant passages of the Commentcny 011 the Sentences and the De Aeternitate Mundi contra Prochnn and other texts of John Philoponus to determine the degree of similarity in the argumentative lines and the philosophical doctrine that Bonaventure would have gathered from the Alexandrian philosopher for the formulation of his reasoning against the eternity of the world.