At the opening, on 28 June, after the singing of theVeni Creator Spiritus, Innocent IV preached on the subject of the five wounds of the Church and compared them to his own five sorrows: (1) the poor behaviour of bothclergy andlaity; (2) the insolence of theSaracens who occupied the Holy Land; (3) the GreatEast-West Schism; (4) the cruelties of theTatars in Hungary; and (5) the persecution of the Church by the Emperor Frederick.
The council of Lyon was rather poorly attended. Since the great majority of those bishops and archbishops present came from France, Italy and Spain, while theByzantine Greeks and the other countries, especiallyGermany, were but weakly represented, the ambassador of Frederick,Thaddaeus of Suessa, contested itsecumenicity in the assembly itself.[4] In a letter, Innocent IV had urgedKaliman I of Bulgaria to send representatives. In the bullCum simus super (25 March 1245), he also urged theVlachs,Serbs,Alans,Georgians,Nubians, theChurch of the East and all the other Eastern Christians not in union with Rome to send representatives. In the end, the only known non-Latin cleric present was Peter, thebishop of Belgorod and vicar of themetropolitanate of Kiev, who provided Innocent with intelligence on the Mongols prior to the council. His information, in the form of theTractatus de ortu Tartarorum, circulated among attendees.[5]
The condemnation of the emperor was a foregone conclusion. The objections of the ambassador, that the accused had not been regularlycited, that the pope was plaintiff and judge in one, and that therefore the whole process was anomalous, achieved as little success as his appeal to the future pontiff and to a truly ecumenical council.[6]
At the second session on 5 July, thebishop of Calvi and a Spanish archbishop attacked the emperor's behaviour, and in a subsequent session on 17 July, Innocent pronounced the deposition of Frederick. The deposition was signed by one hundred and fifty bishops and theDominicans andFranciscans were given the responsibility for its publication. However, Innocent IV did not possess the material means to enforce the decree.
The Council of Lyon promulgated several other purely disciplinary measures:
It prepared thirty-eight constitutions which were later inserted byBoniface VIII in his Decretals, the most important of which decreed a levy of a twentieth on every benefice for three years for the relief of the Holy Land.[8]
Among those attending wasThomas Cantilupe who was made a papal chaplain and given a dispensation to hold his benefices in plurality.[9]
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Bellitto, Christopher M. (2002).The General Councils:A History of the Twenty-One Church Councils from Nicaea to Vatican II. Paulist Press.ISBN978-0809140190.
Biller, Peter (2000).The Measure of Multitude: Population in Medieval Thought. Oxford University Press.ISBN978-0198206323.
Dondorp, Hary; Schrage, Eltjo J.H. (2010). "The Sources of Medieval Learned Law". In Cairns, John W.; du Plessis, Paul J. (eds.).The Creation of the Ius Commune: From Casus to Regula. Vol. 7. Edinburgh University Press.ISBN978-0748638970.
Hefele, Karl Joseph von (1913). H. Leclercq (tr.).Histoire des conciles d'après les documents originaux.(in French and Latin).Vol V, part 2. Paris: Letouzey, 1913.
Maiorov, Alexander V. (2019). "The Rus Archbishop Peter at the First Council of Lyon".The Journal of Ecclesiastical History.71 (1):1–20.doi:10.1017/s0022046919001143.S2CID211652664..
Martínez, H. Salvador (2010).Alfonso X, the Learned. Translated by Cisneros, Odile. Brill.ISBN978-9004181472.
Richardson, Carole M. (2019). "The Cardinal's Wardrobe". In Hollingsworth, Mary; Pattenden, Miles; Witte, Arnold (eds.).A Companion to the Early Modern Cardinal. Brill. pp. 535–556.ISBN978-9004310964.