To this period belongs also the _Centón Epistolario_, a series of a hundred letters purporting to be written by Fernán Gómez de Cibdareal, physician at Juan II.'s court. It is obviously modelled upon the _Crónica_ of Juan II.'s reign, and the imitation goes so far that, when the chronicler makes a blunder, the supposed letter-writer follows him. The _Centón Epistolario_ is now admitted to be a literary forgery, due, it is believed, to Gil González de Ávila, who wrote nothing of equal excellence under his own name. In these circumstances the _Centón_ loses all historic value, and what was once cited as a monument of old prose must now be considered as a clever mystification—perhaps the most perfect of its kind. Contemporary with Cervantes and Lope de Vega was the greatest of all Spanish historians, JUAN DE MARIANA (1537-1624). The natural son of a canon of Talavera, Mariana distinguished himself at Alcalá de Henares, was brought under the notice of Diego Láinez, General of the Jesuits, and joined the order, whose importance was growing daily. At twenty-four Mariana was appointed professor of theology at the great Jesuit College in Rome, whence he passed to Sicily and Paris. In 1574 he returned to Spain, and was settled in the Society's house at Toledo. He was appointed to examine into the charges made by Léon de Castro against Arias Montano, whose Polyglot Bible appeared at Antwerp in 1569-72. Montano was accused of adulterating the Hebrew text, and among the Jesuits the impression of his trickery was general. After a careful examination, extending over two years, Mariana pronounced in Montano's favour. In 1599 there appeared his treatise entitled _De Rege_, with official sanction by his superiors. No Spaniard raised his voice against the book; but its sixth chapter, which laid it down that kings may be put to death in certain circumstances, created a storm abroad. It was sought to prove that, if Mariana had never written, Ravaillac would not have assassinated Henri IV.; and, eleven years after publication, Mariana's book was publicly burned by the hangman. His seven Latin treatises, published at Köln in 1609, do not concern us here; but they must be mentioned, since two of the essays—one on immortality, the other on currency questions—led to the writer's imprisonment.