The view that there must be an Unmoved Prime Mover is at the core of Aristotle’s cosmology. Theophrastus was the first to object to this theory. He paved the way for the objections addressed by Pseudo-Justin, who devoted a whole treatise to undermining some of the basic tenets of Aristotle’s cosmology (Confutatio dogmatum quorundam aristotelicorum). The focus of this paper is on Pseudo-Justin’s critical analysis of Aristotle’s UPM thesis. After providing the bulk of Pseudo-Justin’s criticism, I argue that at least part of his most important objections is reasonable, inasmuch as they are based on Aristotelian assumptions. My main concern is with the argumentative and conceptual framework within which the Pseudo-Justin’s discussion of Aristotle takes place: I hold that Pseudo-Justin engages philosophically with Aristotle. On the other hand, Pseudo-Justin is not always charitable when citing passages from Aristotle. I claim, though, that he does so within reasonable limits and as it would be done by any philosopher interested in making a critical analysis of what another one says.