 Thomas Aquinas’ Commentary on the Sentences (II, d.1 q.1 a.5) is a good example of the impact of Arabic sources. Among the arguments cited from Averroes in favour of eternity are that there is always another moment in time before a moment in time; that only motion can be the cause of a change from rest to motion; that if the world had a beginning, a vacuum would precede the world (Comm. magnum De caelo III.29, Comm. magnum Phys. VIII.8,9,11,15). Avicenna is cited by Thomas as holding that God’s will is unchangeable and never starts anew (an argument advanced also by Averroes), and that it is impossible that God precedes the world in duration, because this implies that time existed before the world and before movement (Metaphysics IX.1). These arguments clearly influenced Thomas’ conclusion that the eternity thesis is the most probable in philosophical terms. However, just like creation, eternity escapes full demonstration. From the standpoint of faith, the eternity of the world is false and heretical. In his treatise On the Eternity of the World, Thomas Aquinas, in contrast to most of his contemporaries, defends the possibility of an eternal creation, thus approaching the position of Avicenna and other Neoplatonic thinkers.