Catholicism is the largest Christian Church, claiming about 1.07 billion members as of 2003. Catholicism is structured into 22 distinct Churches, all of which are in communion with the Pope. Each Church within Catholicism is headed by a bishop known as a patriarch. A patriarch is responsible for ordaining new bishops and establishing new diocese. The largest of these Churches is the Roman Catholic Church, whose patriarch is the Pope, bishop of Rome.
Catholicism views itself as being in historical and doctrinal continuity with Jesus and the 12 Apostles. This expresses itself in several ways within Catholicism. Catholicism holds bishops are the successors to the apostles, and that all Catholic bishops can eventually trace their ordination back to one of the apostles (who in turn is traced back to Jesus).
Catholicism before the Schism with Eastern Orthodoxy
Before the Schism of 1066 Christianity existed as what is sometimes called "the great Church" with most Christians, apart from a few notable exceptions, living within the confines of the Roman Empire. During the third and forth centuries the Eastern and Western halves of the Roman Empire began to experience increased tension as they drifted apart culturally and linguistically. These changes would become solidified after the barbarian invasion and the eventual collapse of the Western Roman Empire in the fifth century. The repercussions of this cultural split were felt within the religious outlooks of Eastern and Western Christians even before the 1066 schism. In what was formerly the Western Roman Empire, administrative power began to be consolidated in Rome by the Pope as most of the social services provided by the Empire began to collapse. This would lead Pope Gregory the Great to establish a bureaucratic system known as the Vatican today.
While not officially part of the Roman Empire anymore, the Pope was canonically required to have his ordination approved by the Eastern Roman Emperor until the title was bestowed on Charlemagne in 800. During this period the filioque would become uniformly added to the creed in the Western Church. These two developments drove the Eastern and Western Church further apart. Eventually, in 1066, the Eastern and Western Churches severed official ties. This took place when a representative of the Pope attended the feast of St. Andrew in Byzantium. During feastal liturgy he delivered a bull (without the Vatican's knowledge) excommunicating the Eastern Church for refusing to add the filioque to the creed and ordaining married men (which the Western Church had ceased to do by this point). While the Easter Church excommunicated the Vatican's representative and not the Western Church, the two Churches had become too different in character to maintain any kind of official unity. With the exception of the Maronite Catholic Church, Catholicism would remain a strictly Western Institution until after the Counter-Reformation.
Catholicism during the Middle Ages
During the Middle Ages in Western Europe the relationship between the secular and the religious, instead of being conceived of as two different spheres, was viewed as two different yet overlapping ways of codifying time. As a result the Catholic Church had a large role to play in the organization of the public order. The Church, under prompting from the Byzantine Empire who was facing military threats from the Muslims, organized a series of military campaigns known as the crusades. Within Western Europe however, the Church would also create The Peace of the Church, which would limit the extent to which secular rulers would be able to go to war with one another. This was applied with varying success. Because of the loss of much of the infrastructure of the Roman Empire monasteries would be one of the few places where an education could be obtained, although there were a few secular schools usually located in royal palaces. This would change towards the end of the Middle Ages. Several factors contributed to this, the largest being the revitalization of European cities, the founding of the universities, and rise of mendicant religious orders. Additionally, in the thirteenth century classical texts that had been lost in the West began to circulate again.
Catholicism during the Renaissance
The Renaissance was both a time of great discovery as well a time of political, religious, and social uncertainty. Some of these the latter issues need to be explored to understand some of the events that occurred within Catholicism during the Renaissance and to understand the cultural milieu of the Reformation. The capital of the Byzantine Empire fell during the fifteenth century. This caused an influx of refugees from the Byzantine Empire. This had a destabilizing effect on Western European economies. Also severe freezing affected crop production in Norther Europe. Not only did this increase These refugees also brought with them religious texts and patterns of spirituality that had been absent in Western Europe for quite some time. During the renaissance there was a period during which there were three active Popes. Many Church abuses began to develop during this period. While there had always been some abuse within the Church, there were also active movements within the Church to reign it in (especially monastic reform). However the sheer volume of abuse, the already depressed economic conditions, as well as a particularly several particularly corrupt Popes, made this especially troublesome. During the 1510-20's Martin Luther began to protest many of these absuses and what he saw as theological problems with Church doctrine. He was excommunicated 1521, and began the Protestant Reformation.
The Counter-Reformation and Early Modern Period
The counter-reformation (also known as the Catholic Reformation) was initiated by the Council of Trent. The Council of Trent would redefine several key theological issues that had contributed to the spread of the Reformation, as well as defined several new dogmas, viz. that there are only seven Sacraments, that Justification is not by Faith only, and that both Scripture and tradition are authoritative for Catholics. During the Counter-Reformation Cathoicism engaged in a series of reforms and new initiatives. For example the period gave rise to several new Religious orders such as the Jesuits and the Ursaline Sisters. The period also saw some of the first missionary efforts to take place since the crusades, most of which were along trade lines to the Americas and the Far East. Catholicism during the early modern period would also face new challenges as the European economic and political situation transformed from feudal kingdoms and manor economies into capitalist nation-states. During the 1700's, for example, the canonization of Saints was moved from the local diocese to the Vatican in order to ensure that it did not become a tool of political leaders.