Chapter 20 presents the way in which Proclus interpreted the figure of the tyrant in Plato’s dialogues. Tyranny is based on force, violates law, both cosmic and human, and is motivated by a misled desire for power, power divorced from goodness and knowledge. I argue that Proclus and other Platonists, Damascius and Simplicius, could use this interpretation of Plato to describe the political regimes of their period, in particular the rule of Emperor Justinian, as tyrannies. These tyrannies, in their metaphysical ignorance and moral turpitude, violated divine order and law in destroying pagan temples and statues. I consider finally the cases of two authors, John Lydus and Procopius of Caesarea, who describe Justinian’s rule in terms of kingship or tyranny.