The Ancient Greek Historians

Polybius is not less express than Thucydides in asserting the principle that accurate representation of facts was the fundamental duty of the historian. He lays down that three things are requisite for performing such a task as his: the study and criticism of sources; autopsy, that is, personal knowledge of lands and places; and thirdly, political experience.

Writing the history of the present is always a very different thing from writing the history of the distant past. The history of the distant past depends entirely on literary and documentary sources; the history of the present always involves unwritten material as well as documents. But the difference was much greater in the days of Thucydides than it is now.