Probably educated at Padua, Marsilius was rector of the university of Paris in 1313. His philosophical fame rests on Defensor Pacis (‘Defender of the Peace’, 1324, trs. under the same title, 1956), a devastating indictment of Papal claims to temporal power. Marsilius defends an Aristotelian theory of the political state as subserving the good life. Law is essentially the coercive power of the state necessary to promote this end. The people therefore form the only legitimate source of political authority. The positivist and republican implications of all this were well before their time; in 1326 Marsilius was forced to flee to the court of Louis of Bavaria and was branded a heretic by Pope John XXII.