Anacyclosis is a theory of political evolution based on three good types of government and three malignant types. Respectively, these are monarchy (rule of one), aristocracy (rule of few), democracy (rule of many), and tyranny, oligarchy, and ochlocracy (mob rule or mobocracy).
The theory began with Plato and Aristotle, and was continued by Greek historian Polybius, who recorded it in Book VI of The Histories. The theory is generally attributed to Polybius. Machiavelli described the theory in Discourses on Livy.
Sequence as described by Polybius
First, society begins with a monarchy. In the beginning the king is a good and wise ruler, but his successors become tyrants, prompting the higher class to overthrow the monarchy and institute an aristocracy. As the descendants of the aristocrats come into power, they become power-hungry and corrupt, and turn into oppressive oligarchs. This prompts the people to finally remove the oligarchs and take over the government themselves, forming democracy. But democracy degrades and becomes mob rule, and out the chaos of mob rule a new monarch rises up, thus beginning the cycle anew.