“Those who insist that history is simply the effort to tell the thing exactly as it was, to state the facts, are confronted with the difficulty that the fact which they would represent is not planted on the solid ground of fixed conditions; it is in the midst and is itself a part of the changing currents, the complex and interacting influences of the time, deriving its significance as a fact from its relations to the deeper-seated movements of the age, movements so gradual that often only the passing years can reveal the truth about the fact and its right to a place on the historian’s page.”