Astrology presents the clearest example of this nexus of power, knowledge, and rhetorical intent. Its practitioners enjoyed a close relationship with imperial power, and its doctrines and imagery, as Barton demonstrates in her pages on the significance of capricorn in imperial iconography, became part of the symbolic currency of empire. The fact that casting the emperor's nativity was a capital offense merely confirms this intimacy between perceptions of the stars and perceptions of power. In these conditions, Barton demonstrates, astrological writers preened and strutted in agonistic competition for pupils, influence, and credibility. Clarity may not have been a desideratum of ancient astrologers, but it is a great merit of Barton's presentation of their work.
Astrologers behave like sophists.
Physiognomists sometimes were, as the case of Antonius Polemo shows. Physiognomy, in fact, has affinities with rhetorical theory, and in particular the doctrine of ethos or presentation of character. Against them rhetoricians could define themselves and their largely male, citizen audience, and in their undesirable image they could shape their enemies. Medicine, finally, presents the most complex example, both conceptually and in richness of documentation. Barton chooses to concentrate on Galen, who more than any other ancient physician gives us an explicit account of his epistemological and rhetorical program.