‘Greek political science studied constitutions and generalized the relation between human nature and political associations. Perhaps the most powerful instrument was the theory of recurrent cycles. Monarchies tend to degenerate into tyranny, tyrannies are overthrown by aristocracies, which degenerate into oligarchies exploiting the population, which are overthrown by democracies, which in turn degenerate into the intolerable instability of mob rule, whereupon some powerful leader establishes himself as a monarch and the cycle begins all over again. This is the version of political science we find influentially expounded by a later Greek called Polybius whose main concern was to explain the character of Roman politics to his fellow Greeks; other versions of a political cycle are to be found in Plato and Aristotle.’
Minogue, Kenneth. Politics. Oxford: Oxford University Press, 1995. (Pg 16).