Historiography (or reference to professional historians's opinions) is a great way to improve the sophistication of your history essays - showing your grasp of the various debates surrounding the topic you are writing about. History is rarely clear cut - and it is important to acknowledge that a range of possible truths exist, each shaped by the different contexts or purposes in which a historian considers the events. For instance, a Marxist historian may place particular emphasis on class conflict as causing historical change - whereas a Revisionist may stress the a number of grass level, local factors. Being conscious of how these different perspectives affect your understanding of a historical situation is useful for considering a range of opinions - your argument should have a point and specific direction, yet will be improved by the qualification of considering a range of other opinions, if even simply to reject them.