While still practising medicine he entered into relations with another master of Paris, the philosopher John of Jandun, who collaborated with him in the composition of the famous Defensor pacis (1324), one of the most extraordinary political and religious works which appeared during the 14th century.
The Defensor pacis, as its name implies, is a work intended to restore peace, as the most indispensable benefit of human society.
Deposed by the head of the Empire (April 18), and a mendicant friar, Pietro de Corbara, raised by an imperial decree to the throne of St Peter (as Nicholas V.) after a sham of a popular election (May 12), all this was merely the application of principles laid down in the Defensor pacis.
But, above all, in an unpublished work preserved at Oxford, the Defensor minor, Marsilius completed and elaborated in a curious manner certain points in the doctrine laid down in the Defensor pacis.
But the scandal provoked by his Defensor pacis, condemned by the court of Avignon in 1326, lasted much longer.
There are numerous manuscripts of the Defensor pacis extant.
Count Litzow in The Life and Times of Master John Hus (London and New York, 1909), pp. 5-9, gives a good abstract of the Defensor pacis and the relations of Marsilius to other precursors of the Reformation.
After 1282 the signoria was composed of the 3 (afterwards 6) priori of the gilds, who ended by ousting the buoni uomini, while a defensor artificum et artium takes the place of the capitano; thus the republic became an essentially trading community, governed by the popolani grassi or rich merchants.
(1316-1334)1334) to control the election of the emperor called forth the first fundamental and critical attack on the papal monarchy, by Marsiglio of Padua, who declared in his Defensor pacis (1324) that the assumed supremacy of the bishop of Rome was without basis, since it was very doubtful if Peter was ever in Rome, and in any case there was no evidence that he had transmitted any exceptional prerogatives to succeeding bishops.
Side by side with the Minorites, the spokesmen of the specifically political opposition to the papacy were the Parisian professors, Marsilius of Padua and John of Jandun, the composers of the " Defender of the Peace " (defensor pacis).
The conferring of the imperial crown by the Roman populace, the deposition of the pope by the same body, and the election of an anti-pope in the person of the Minorite Pietro da Corvara, translated into acts the doctrines of the defensor pacis.
Little is known of the condition of the subject populations of the peninsula during the Arab occupation; but we are informed that the Christians were, sometimes at least, judged according to their own laws in separate tribunals presided over by Christian judges; 2 and the mere fact of the preservation of the name alcalde, an official whose functions corresponded so closely to those of the judex or defensor civitatis, is fitted to suggest that the old municipal fora, if much impaired, were not even then in all cases wholly destroyed.
The idea of this extension originated no doubt in the fact that the Italian patricius of the 6th and 7th centuries had come to be regarded as the defensor, protector, patronus of the Church.
King Henry himself in 1521 had deigned to write an abusive pamphlet against Luther, for which he had been awarded the magnificent title of Fidel Defensor by that cultured sceptic Pope Leo X.
DEFENDER OF THE FAITH (Fidei Defensor), a title belonging to the sovereign of England in the same way as Christianissimus belonged to the king of France, and Catholicus belongs to the ruler of Spain.