A tyrant, in the modern English usage of the word, is an absolute ruler who is unrestrained by law, or one who has usurped a legitimate ruler's sovereignty. Often portrayed as cruel, tyrants may defend their positions by resorting to repressive means. The original Greek term meant an absolute sovereign who came to power without constitutional right, yet the word had a neutral connotation during the Archaic and early Classical periods. However, Greek philosopher Plato saw tyrannos as a negative word, and on account of the decisive influence of philosophy on politics, deemed tyranny the "fourth and worst disorder of a state."Tyrants lack "the very faculty that is the instrument of judgment"—reason. The tyrannical man is enslaved because the best part of him (reason) is enslaved, and likewise, the tyrannical state is enslaved, because it too lacks reason and order.

Autocracy is a system of government in which absolute power is held by the ruler, known as an autocrat. It includes most forms of monarchy and dictatorship, while it is contrasted with democracy and feudalism. Various definitions of autocracy exist. They may restrict autocracy to cases where power is held by a single individual, or they may define autocracy in a way that includes a group of rulers who wield absolute power. The autocrat has total control over the exercise of civil liberties within the autocracy, choosing under what circumstances they may be exercised, if at all. Governments may also blend elements of autocracy and democracy, forming an anocracy. The concept of autocracy has been recognized in political philosophy since ancient times.