PANETIUS, a celebrated Stoic, was a native of Rhodes, and flourished in the second century B.C. After learning grammar at Pergamum under Crates of Mallus, he settled in Athens as a student of the Stoa. Under Diogenes of Babylon and Antipater of Tarsus, the successive heads of the Stoic school, he rose to eminence and repute. The great Roman, Scipio Æmilianus, became his friend, and chose him for a travelling companion; and the Stoics, on the death of Antipater, elected him for their master. It was in this latter capacity that Panetius established his reputation as an original expounder of the ethical doctrines of his school. He modified the severely abstract maxims of the Stoa into a form more suitable for practical life; supplied their defects from the systems of Aristotle, Xenocrates, Theophrastus, Dicaearchus, and Plato; and clothed them in the fascinating garb of simile and rhetorical ornament. Rectitude was defined to be "living in conformity with our natural impulses." The virtues were divided into contemplative and active; and the useful and the honourable qualities in actions were declared to be coincident. The principal work in which Panetius embodied these principles was a treatise On Duty in three books. It is not extant, but its contents have been incorporated in the first two books of Cicero's De Officiis.