Historian Ammianus Marcellinus says he was "keen and eager in plotting treachery", and describes him as "fickle flatterer" to Constantius II.
Arbitio did not take part in Julian's Persian expedition, instead retiring to live as a private citizen.
[1] In 365, Procopius, a relative of the deceased emperor Julian, attempted to seize control of the Roman Empire's eastern half from Valens.
[4] During the subsequent campaign, Arbitio encountered an old friend, Gomoarius, serving in the opposing army, and convinced him to desert to Valens.
[6] What happened to Arbitio after this time is unknown, although it is reasonable to assume that he retired, and subsequently died without taking any further part in matters of state.