Appius Claudius Caecus
Prosopopoeiae are used mostly to give another perspective on the action being described. For example, in Cicero's Pro Caelio, Cicero speaks as Appius Claudius Caecus, a stern old man. This serves to give the "ancient" perspective on the actions of the plaintiff. Prosopopoeiae can also be used to take some of the load off the communicator by placing an unfavorable point of view on the shoulders of an imaginary stereotype. The audience's reactions are predisposed to go towards this figment rather than the communicator himself.