A historical theory of uncertain origin is directly relevant to how Roman historians, particularly those who wrote in Greek, understood the future of Rome: four empires have dominated the world, Rome is the fifth, signifiying either the continuation of a natural process or the end of the historical cycle. This 4+1 model of world empires occurs also in Jewish and Christian apocalyptic, deriving ultimately from the Book of Daniel, where it may be a reworking of a Zoroastrian tradition.1 So compelling was the idea for the Jews and Christians living in the Roman Empire, nursing messianic dreams, that its absence in a major Jewish thinker of the first century requires explanation.2 Among historians of Rome the model first appears as a tool of explanation and prediction in Polybius’ Greek history of Rome, then in Latin Aemilius Sura3 and Pompeius Trogus – in each of these first cases, indirectly, or in quoted fragments – then certainly in Dionysius of Halicarnassus and later Greek writers. Thus, the 4+1 scheme appears in Greek prose literature from as early as the second century BCE, around the time that the Book of Daniel was being redacted.