  Like the polemic against Proclus, Against Aristotle is mainly devoted to removing obstacles for the creationist. If Aristotle were right about the existence of an immutable fifth element (ether) in the celestial region, and if he were right about motion and time being eternal, any belief in creation would surely be unwarranted. Philoponus succeeds in pointing to numerous contradictions, inconsistencies, fallacies and improbable assumptions in Aristotle’s philosophy of nature relating to these claims. Dissecting Aristotle’s texts in an unprecedented way, he time and again turns the tables on Aristotle and so paves the way for demonstrative arguments for non-eternity. One such argument is reported by Simplicius (In Phys. 1178,7–1179,26 = Contra Aristotelem, Fr. 132). It relies on three premises: (1) If the existence of something requires the preexistence of something else, then any one thing will not come to be without the prior existence of the other. (2) An infinite number cannot exist in actuality, nor be traversed in counting, nor be increased.  (3) Something cannot come into being if its existence requires the preexistence of an infinite number of other things, one arising out of the other. From these not at all un-Aristotelian premises Philoponus deduces that the conception of a temporally infinite universe, understood as a successive causal chain, is impossible. The celestial spheres of Aristotelian theory have different periods of revolution, and in any given number of years they undergo different numbers of revolutions, some larger than others. The assumption of their motion having gone on for all eternity leads to the conclusion that infinity can be increased, even multiplied, which Aristotle himself held to be absurd.