Marcus Aurelius seems to have been about eighteen years of age when the correspondence begins, Fronto being some thirty years older.[16] The systematic education of the young prince seems to have been finisht, and Pronto now acts more as his adviser than his tutor. He recommends the prince to use simplicity in his public speeches, and to avoid affectation.[17] Marcus devotes his attention to the old authors who then had a great vogue at Rome: Ennius, Plautus, Nævius, and such orators as Cato and Gracchus.[18] Pronto urges on him the study of Cicero, whose letters, he says, are all worth reading.