The most famous of all these speeches, that of Maecenas to Augustus regarding the establishment of the monarchy, is in reality a political pamphlet setting forth Dio's own views of government, and parts of it are an anachronism in the mouth of Maecenas. Again, the speech which Dio makes Caesar deliver to his officers (not to his troops) before the battle with Ariovistus has almost nothing in common with the address reported by Caesar himself.
The problem of Dio's sources for the periods before his own day has been investigated by various scholars with widely divergent results. It is clear that he has much in common with Livy, but the tendency of early investigators was to overrate Livy's influence. Schwartz has shown that down to the end of the Second Punic war Dio holds an independent course between the various traditions known to us. After this there is apparent an increasing similarity between his account and that of Livy, which becomes most marked in the periods of the civil war, and the natural inference is that Livy was here used directly as a principal source. There are important agreements also with Polybius, but no conclusive evidence of direct dependence. Sallust was almost certainly not among Dio's sources, and it is not probable that Caesar's Commentaries were used, at least to any extent. For the period of the empire Tacitus has been confidently claimed by some as an important source, particularly for the reign and