Power and Knowledge charts a history of three ancient scientiae in the Roman Empire — astrology, medical prognosis, and physiognomy (the art of discerning character or destiny from a person's physique). Drawing on contemporary approaches in social theory and the philosophy of science, Tamsyn Barton argues that the ancient sciences are best understood in terms of rhetoric, as their practitioners are involved in sociopolitical struggles and their disciplines are rooted in Greco-Roman cultural norms and practices.