Human Nature defined by Aristotle and Machiavelli -

A common theme addressed by many of the authors in medieval and ancient political theory is the role of human nature in politics. Two thinkers from different time periods who have distinct views on the role of human nature are Aristotle and Machiavelli. Explain their thoughts on human nature and how it influences the political realm. How should leaders/states manage the natural impulses and desires of man?

At least 500 words per answer with 1-2 references.