Probably the best known and arguably the most influential political philosopher of all time; the arguments about the coherence, influence and intention of Machiavelli (1469-1527) are all over the place.
Was he writing critically and satirically of the Medici or was he trying to get into their good graces by praising them? Are his writings coherent or self-contradictory? (After all when you have Alexander Hamilton, John Adams and Thomas Jefferson all quoting him in support of their positions, you have a strange set of bedfellows.) Was he an empiricist, a realist or an idealist?
If I do not believe that a just society can be achieved by allowing its citizens to cite their ends to justify their means, I cannot accept that a just society can exist by allowing its leader(s) to do so.