A poet's object is not to tell what actually happened but what could or would happen either probably or inevitably.... For this reason poetry is something more scientific and serious than history, because poetry tends to give general truths while history gives particular facts.
By law of periodical repetition, everything which has happened once must happen again and again -- and not capriciously, but at regular periods, and each thing in its own period, not another's and each obeying its own law.