In this article, I take a new look at the problem of Calasiris’ ‘duplicity’ as depicted in the long autobiographical narrative he delivers to Cnemon in Books 2-5 of Heliodorus’ Aethiopica. A close parallel for Calasiris’ self-presentation can be found in an unlikely source: the medical case histories of the doctor Galen. Through a comparison of Calasiris’ narrative with those of Galen, I demonstrate that both narrators employ similar ‘deceptive’ strategies to showcase their observational and deductive skills to their audience. Calasiris’ foregrounding of such ‘rational’ methods and his downplaying of the prophetic power that others attribute to him suggest that, despite the Aethiopica’s religious trappings, its ideal reader is a secular one.