<P> The Cluniac reform of monasteries that began in 910 placed abbots under the direct control of the pope rather than the secular control of feudal lords, thus eliminating a major source of corruption . This sparked a great monastic renewal . Monasteries, convents and cathedrals still operated virtually all schools and libraries, and often functioned as credit establishments promoting economic growth . After 1100, some older cathedral schools split into lower grammar schools and higher schools for advanced learning . First in Bologna, then at Paris and Oxford, many of these higher schools developed into universities and became the direct ancestors of modern Western institutions of learning . It was here where notable theologians worked to explain the connection between human experience and faith . The most notable of these theologians, Thomas Aquinas, produced Summa Theologica, a key intellectual achievement in its synthesis of Aristotelian thought and the Gospel . Monastic contributions to western society included the teaching of metallurgy, the introduction of new crops, the invention of musical notation and the creation and preservation of literature . </P> <P> During the 11th century, the East--West schism permanently divided Christianity . It arose over a dispute on whether Constantinople or Rome held jurisdiction over the church in Sicily and led to mutual excommunications in 1054 . The Western (Latin) branch of Christianity has since become known as the Catholic Church, while the Eastern (Greek) branch became known as the Orthodox Church . The Second Council of Lyon (1274) and the Council of Florence (1439) both failed to heal the schism . Some Eastern churches have since reunited with the Catholic Church, and others claim never to have been out of communion with the pope . Officially, the two churches remain in schism, although excommunications were mutually lifted in 1965 . </P> <P> The 11th century saw the Investiture Controversy between Emperor and Pope over the right to make church appointments, the first major phase of the struggle between Church and state in medieval Europe . The Papacy were the initial victors, but as Italians divided between Guelphs and Ghibellines in factions that were often passed down through families or states until the end of the Middle Ages, the dispute gradually weakened the Papacy, not least by drawing it into politics . The Church also attempted to control, or exact a price for, most marriages among the great by prohibiting, in 1059, marriages involving consanguinity (blood kin) and affinity (kin by marriage) to the seventh degree of relationship . Under these rules, almost all great marriages required a dispensation . The rules were relaxed to the fourth degree in 1215 (now only the first degree is prohibited by the Church - a man cannot marry his stepdaughter, for example). </P> <P> Pope Urban II launched the First Crusade in 1095 when he received an appeal from Byzantine emperor Alexius I to help ward off a Turkish invasion . Urban further believed that a Crusade might help bring about reconciliation with Eastern Christianity . Fueled by reports of Muslim atrocities against Christians, the series of military campaigns known as the Crusades began in 1096 . They were intended to return the Holy Land to Christian control . The goal was not permanently realized, and episodes of brutality committed by the armies of both sides left a legacy of mutual distrust between Muslims and Western and Eastern Christians . The sack of Constantinople during the Fourth Crusade left Eastern Christians embittered, despite the fact that Pope Innocent III had expressly forbidden any such attack . In 2001, Pope John Paul II apologized to the Orthodox Christians for the sins of Catholics including the sacking of Constantinople in 1204 . </P>

Where did the roman catholic religion come from