The article aims at demonstrating that in attributing the creatio ex nihilo to both Plato and Aristotle as their unanimous philosophical conviction the Treatise on the Harmony between the Two Sages deeply depends upon the Neoplatonic reading of those two philosophers. The main obstacles for such a view in the works of the two sages are Plato's assumption of a precosmic chaos in the Timaeus and Aristotle's denial of any efficient causality to the unmoved mover in the Metaphysics. Both of these points had been, however, done away with by the Neoplatonist commentators already, especially by Ammonius in his lost treatise on efficient and final causality in Aristotle the use of which in the Harmony is shown by a comparison with Simplicius. Chris...