Spanish Jesuit scholar, associated with the School of Salamanca. Although celebrated for his rather famous history of Spain (1592), towards the end of his life, civil and ecclesiastical authorities began to realize that Juan de Mariana was a "troublemaker". In his famous 1598 treatise, Mariana took the Salamanca "natural law" doctrines to the a famous extreme in arguing that it was "naturally right" to kill tyrannical kings. But what constitutes "tyrannical"? In 1599 and then 1605, Mariana took his thesis a step further, arguing that as private property of the subjects is private, then interference by the sovereign in private economic matters without consent of the subjects constitutes "tyranny". Oppressive taxation, of course, is an example. But, Mariana notes, so is government-backed inflation (from, e.g. the official debasement of currency), which "steals" from the subjects.
Publicly condemned in France and subsequently Spain, Mariana's works were burnt and he was eventually imprisoned in 1610, where he remained until almost the end of his life. Surprisingly, it was not Mariana's defense of tyrannicide but rather his condemnation of debasement that got him charged with treason!
Major Works of Juan de Mariana
Resources on Juan de Mariana