In judging Diodorus, then, one must judge him as a Roman of the first century B.C., not as a European of the twentieth century A.D. And if we bear this in mind, we shall find, after scanning his pages, that Diodorus was by no means marked among his fellows by simple credulity of the unquestioning type which accepts whatever is told it without subjecting it to criticism. Diodorus, to be sure, tells us fabulous tales as to the origin of the world and the creation of its various peoples; but he explicitly forewarns us that he tells these tales, not as matters of his own belief, but in order to make an historical record of the opinions current among the different nations themselves as to their own origin.
These tales seem to us fabulous, grotesque, absurd; but we have no reason to doubt that many of them seemed equally mythical to Diodorus himself; and modern criticism should not forget that there is one other myth tale of the creation of the world and the origin of a particular race, which, had Diodorus known it, he would doubtless have narrated with the rest, and viewed with the same scepticism which he shows towards the others, as being fabulous, grotesque, and absurd, but which would have been accepted by the critics of all Christendom, in every age prior to our own, as the authentic historical record of the actual creation of the earth, and as the true account of its chosen people.
In a word, modern criticism should bear in mind, when reproaching Diodorus and others like him for their credulity, that the accepted faith of nineteenth-century Europe would have seemed to Diodorus as absurd and fabulous and mythical as any tale which he has to tell us can seem to the twentieth-century critic.
And as to the mistakes of Diodorus in the more strictly historical portions of his narrative, these also must be viewed with a certain toleration by every candid critic when he reflects upon the vast preponderance of those cases in which the records of Diodorus are worthy of the fullest credence. In considering these matters, it is very easy, indeed, to generate myths that befog our view of the true status of an ancient author. Thus, for example, it was once traditional to regard Thucydides as the most candid, just, and impartial historian who has ever lived; but it can hardly be in doubt that the real reason why this estimate has grown up about the name of Thucydides is the fact that, as Professor Mahaffy points out, Thucydides is the sole authority for the history of most of the period of which he treats. It has even been admitted by Müller that in the early portion of the first chapter of Thucydides, where he treats on Grecian history in general, and up to the Peloponnesian War, he does not manifest the same impartiality which distinguishes him in the later portions of his narrative. But it is precisely in this earlier chapter that Thucydides deals with events that are recorded by other historians. It is here, and for the most part here alone, that his story can be checked by data from other authors. Could we similarly check the story of the Peloponnesian War in general, it can hardly be in doubt that we should come across at least some discrepancies which would have tended materially to modify the almost idolatrous estimate of Thucydides that came to be, and long continued to be, unquestionably associated with his name.