In this paper, the author spells out St. Bonaventure's magisterial teaching on the possibility of an eternal world, found in his 'Commentaria in II Sententiarum', d. 1, p. 1, a. 1, q. 2. The entirety of this 'quaestio' is treated at length in order to delineate its structure and indicate its reliance on both theological and philosophical premises. Hence, the twofold dependency of St. Bonaventure's position on Scripture and on arguments against an actual infinity is made clear. The author concludes with a Thomistic response to the Seraphic Doctor's position, based solely on the Angelic Doctor's late treatise 'De aeternitate mundi', in which St. Thomas endeavors to place the eternal world question on purely philosophical grounds and also doubts the plausibility of arguments against the possiblity of an actual infinity.