Received: 11-11-11 / Accepted: 21-03-12The opuscule De aeternitate mundi contra murmurantes is Aquinas’s only work dedicated entirely to the problem of the eternity of the world. Written in 1270 the work contains its more complete thought on the subject. In this work Aquinas’s proposes that the world could be both created and eternal, even if the catholic doctrine proposes that the world was created in a single moment. Aquinas’s goal is to show that this is a possible rational alternative even if the doctrine says otherwise. On this matter, Aquinas’s position defends Aristotle’s physics. The argumentative subtleties of the work, based on its rough metaphysical language and lack of historic context, may alienate contemporary readers. This article is logic commentary of the text with the intention of organize and clarify Aquinas’s arguments.