Diodorus, a native of central Sicily, had come to Egypt to compile a historical magnum opus. Historians, he knew had been divided by Polybius into two categories: those who immerse themselves in the actuality of events, drawing the material for their works from their own concrete experiences (these alone, said Polybius, being worthy of esteem), and those who take an easier course, seeking out some ‘city well supplied with libraries’ where they can sit at their desks, consult an atlas, and travel, as Ariosto would have put it, ‘with Ptolemy the geographer’. Diodorus was of the latter school. But as Polybius’s ideas were much in vogue among the Greek and Roman public, it was as well to display some first-hand experience, and Diodorus accordingly fabricated a series of voyages he had never made. The philosophical proem to his work tells us that the author has travelled through much of Asia and Europe, undergoing all manner of hardships and dangers, in order to behold in person everything, or as nearly as possible everything, of which this history treats. We are well aware that the majority of historians, including some of the best known, have made numerous geographical errors. These words of severe reproof were in fact taken verbatim from Polybius. His journey to Egypt was the sole voyage Diodorus had ever made.