Abstract

In this paper I aim to discuss a fragment of Aristotle’s De Philosophia (fr. 21 Ross = Cic. N.D. ii, 44). After defending Cicero’s reliability as a source for the present fragment, I will focus on its contents, with particular reference to the similarities and differences between fr. 21 Ross and De Caelo A-B: my aim in this comparison is to identify two different astronomical systems underlying, on the one hand, the account of fr. 21 Ross and, on the other hand, that given in the treatise. This shift of model is in my view the actual reason for the inconsistency between these accounts. Such an inconsistency might be explained in chronological terms: the last part of the paper, indeed, develops the hypothesis that De Philosophia Γ was written before 353–350bc, namely before Aristotle got acquainted with Eudoxus’ astronomical system.