In the reign of Augustus, we are told in the Gospel According to Mark, there went out a decree from Caesar Augustus that all the world should be taxed. The author of the Gospel was presumably aware that the Principate did not literally cover the world. Augustus, his successors, their advisors and associates, and the Roman people of the time were certainly aware of it. Yet the famous Gospel expression aptly conveyed a sense that, nearly without exception, the Roman system included within its orbit all of the world that really mattered. Once Cleopatra clasped the asp to her bosom, the last of the powers that had previously contested the Mediterranean basin was subjected to Roman rule; all that remained were client states under Roman domination. On its various frontiers, the empire might trail off into the lands of forest tribes, or mountain tribes, or desert…