In this Discourse Dio recounts for the benefit of his fellow-townsmen a conversation which took place between himself and certain citizens of Borysthenes in Pontus. Borysthenes was an ancient Greek trading-centre near the mouth of the Hypanis (Bug), and Dio states that he had gone there in the hope of pushing into the interior for the purpose of visiting the Getae, whose culture he was to describe in Τὰ Γετικά, a work no longer extant.
Arnim holds that Dio was in Borysthenes in a.d. 95 and suggests that his failure to reach the land of the Getae at that time may have been due to trouble between Rome and Dacia. It is plain that he had met with disappointment and that people knew of his purpose to leave Borysthenes by ship. If Arnim’s date is correct, his destination could hardly have been Prusa—despite the word οἴκαδε used by Hieroson in section 25—for in a.d. 95 he was still an exile. However, he seems to have been at home as early as a.d. 97, and Arnim supplies arguments in favour of a.d. 101 as the year in which he made this report to the people of Prusa.
The narrative opens in leisurely manner and with a natural charm somewhat reminiscent of the opening of Plato’s Phaedrus, to which, indeed, Dio may have owed also some of the ideas to which he gives expression, although for the most part he seems to be employing Stoic doctrine. In the course of his account he introduces a myth which he ascribes to the Zoroastrian lore of the Magi. That myth is responsible for not a little of the fame enjoyed by this Discourse. Dio, like Plato, was fond of myths and used them to good advantage. Some
of them at least are believed to have been his own invention; what shall we say of this one?
It would not be surprising if the Greek world of that day had some acquaintance with Zoroastrianism. The name Zoroaster occurs in Greek as early as the pseudo-Platonic Alcibiades, and Herodotus, Xenophon, Strabo, and other Greeks who antedate Dio have not a little to tell of the Magi, some of the information being demonstrably authentic. Hirzel (Der Dialog) is of the opinion that, whatever may be true of other myths in Dio, this one at least emanates from Zoroastrian sources, and Jackson (Zoroastrian Studies) shares that belief, though admitting that ‘the conception may have received some Greek colouring in its transmission.’ Whatever Dio’s indebtedness to the Magi, resemblances between their extant records and this myth are so slight as to warrant the belief that in its present form it is Dio’s own creation, in the formation of which he may have drawn upon more than one source of inspiration, among which it seems safe to suggest the Phaedrus and the Timaeus of Plato, as well as familiar Stoic concepts on related subjects.