 Our evidence for the views of the philosophers of the Middle Stoa is relatively fragmentary. The testimonia for Antipater were included in volume 3 of von Arnim (1903–05). For Panaetius, see van Staaten (1962) and for Posidonius, see Edelstein and Kidd (1972). Panaetius hovers in the background of one of the most influential books in moral philosophy up through the late 19th century: Cicero’s On Duties or De Officiis. In one of his letters to his friend Atticus (XVI. 11.4) Cicero says that he based the first two books of his work on Panaetius’ treatise of the same name. It is perhaps on this basis that some interpreters have taken Middle Stoic moral philosophy to be more “practical” than that of the Old Stoa, for On Duties concentrates on identifying proper functions in a context where it is clear we are not talking about the infallible Stoic sage. But Sedley (in Inwood, 2003) correctly points out that any work on proper functions would have just such a focus. Our evidence may constitute an unrepresentative sample of Panaetius’ work in moral philosophy.