Basil of Caesarea, in his polemic against astrology (Homiliae in hexaemeron 6,5−7), makes direct, creative uses of Origen’s anti-astrological treatise (Philocalia 23). My argument is based on an identical context, namely the interpretation of Gen 1:14b, and five close similarities in content, some verbatim, between Basil’s sermon and Origen’s anti-astrological polemic (and in one case a passage from De principiis). These five similarities are on the topics of the definition of genethlialogy, the system of genethlialogy, aspects, the life of the stars, and fatalism. In each instance, Basil uses Origen in a different way. These uses run the gamut from the wholesale adoption of Origen’s definition of genethlialogy to the refutation of Origen’s belief that the stars are alive. Adaptation is necessitated, not only by Basil’s inherent creativity and relative independence from Origen, but by the fact that the rhetorical form of Basil’s treatment is different from Origen’s: whereas Origen offers a commentarial treatment with a systematic question-and-answer structure, Basil’s argument is a rhetorically sophisticated diatribe, which uses sarcasm and mockery to entertain as well as persuade its audience. Basil uses Origen sometimes freely, sometimes verbatim, but always critically, to support his own goals.