The Roman Catholic Church, a principal world religion today in competition with other Christian faiths, had, by 1600, achieved dominance over huge swaths of Europe. A virtual monopoly in these areas, the Church captured and set rules for marriage as a religious institution, manipulated capital markets, engaged in military campaigns and pogroms to suppress competition in a variety of ways, and effectively controlled some civil governments and leaders with threats of excommunication and non-support. Most importantly, the Church developed a vertically integrated super-national organizational structure - a global firm -- with an upstream component setting policy and doctrine (the pope as CEO and curia in Rome) and a downstream church (parishes, monasteries, legates to civil governments and so on) that "sold" the primary product - assurances of eternal salvation. Economic Origins of Roman Christianity, supported by sociological and historical accounts, explains in economic terms how this medieval monopoly arose over the First Millennium. The monopoly interlude of the Middle Ages (approximately 1100 to 1517) was sandwiched between two periods of competitive organization within Christianity - essentially the first three hundred years after the birth of Christ and the post-16th century, post-Reformation period which has produced more than 2,000 "brands" of Christianity in contemporary times. The method of early Christianity to "out compete" other pagan and ethnic religions was to use apostle-entrepreneurs such as St. Paul to offer a belief product with a lowered full price as opposed to Jewish and Greco-Roman cults. That product included a well defined and happy afterlife contract with assurances of eternal salvation attached. This and other products of the Christian faith (social and charitable works and services) spread throughout the East and large parts of Europe through networking by apostles in enclaves within cities. Christ, however, had promised to return to "judge the living and the dead," and the apostles enthusiastically advertised as much. When the latter event did not materialize over three centuries in the context of a number of early competing brands of Christianity, a second critical task was necessary to ensure the survival of the sect. Credibility of Christian teachings had to be fashioned and constantly renewed to form a coherent and unified product defining what it meant to be Christian. This second task occurred at a council of bishops called by Constantine in 325CE at Nicea (in modern day Turkey) to solidify the canon of books of the Old and New Testaments and outlining what had to be believed to be a Christian. (The Council's choices were not accompanied by required interpretations of that literature.) Constantine, we maintain, accepted Christianity as a state religion largely because Christian behavior lowered many costs to the state - fewer police and social services were necessary, freeing resources to fight wars at the perimeters of Roman authority and influence. He and his successors went about forcing conversions and dismantling or demolishing competing sects, giving the booty and authority to the Christian Church established under Nicean rules. An important question remained for the early Christian church - who or what group was to manage the firm that supplied the product at Nicea? Was it to be a council of bishops mimicking the organization of the apostles or was it to be a single CEO (in the person of the pope of Rome)? Was the pope of Rome a figurehead deserving only of special reverence or did he function as the apex and director of the Church in all matters of faith and interpretation thereof? Eastern bishops (and patriarchs), including Constantine, believed that the bishop of Rome deserved some homage, but that the Church should be governed by councils of bishops. (Many Eastern Christians maintain that belief today). A long and protracted debate over the seat of Christian authority ensued throughout the First Millennium. Economic Origins provides an analysis of how the question was ultimately answered. A structure that ultimately produced a vertically integrated monopoly, one with linked "upstream" and "downstream" segments, began to develop around the bishop of Rome. Eastern dominance of Christianity in the centuries following Nicea was an effective counterbalance against the claims of Rome for a time, but ultimate capitulations to Muslim invasions crippled this area of resistance to Roman control. Additionally, missionary and religious entrepreneurs were extraordinarily successful in spreading Christianity - with Roman backing - throughout parts of Eastern Europe and the British Isles and among the pagan tribes attacking Rome and at the perimeters of the dissolving empire. The suppression of competing "Christian" and pagan sects proceeded apace as well. Assertions of Roman papal hegemony were carried forward through arrangements with Merovingian and Carolingian rulers. Few rulers, in the face of dominance of Christian subjects, could afford to deny or defy the authority or sanction of the Roman bishop. Thus, a vertically integrated structure, common to economic firms, developed between the upstream rule makers and the downstream parish priests, monks and papal attachés to civil rulers. Rules and directives flowed downstream, and church revenues and wealth flowed upstream to Rome with opportunistic behavior at the lower levels severely condemned and punished (excommunication was and is a common tool). This well-known economic system - sometimes called "Cesaropapism" in the context of Roman Catholicism because it imitated the Roman imperial system - involved economic and political reciprocity between civil rulers (for example, Martel, Pippin, or Charlemagne) and the Roman pope of the moment. Civil authorities traded protection of and allegiance to the Roman papacy for approbation by the Roman bishop of the legitimacy, credibility and panache of their rule. By the time of Charlemagne and the early ninth century, the church made great strides toward becoming a vertically integrated monopoly. Despite the Viking invasions of the ninth century, tapering off in the tenth, and in spite of continued disputes with the Eastern branch of Christianity, the Roman Church emerged to dominate religion in much of Western Europe. Opposition to Roman assertions led to schism with the Eastern Church in 1054. Latin Church missionaries and priests brought Christian beliefs and customs to pagans just as the Roman imperial government conquered nations through "Romanization," bringing Roman customs, laws and institutions to the vanquished. The structure of Roman Christianity in fact bears strong resemblance to the secular Empire it replaced, with an imperial leader designated pontifex maximus, which later became a papal title. The ensuing monopoly, most strikingly asserted in the eleventh century by Pope Gregory VII over Christian belief and practices, lasted until the early 16th century and the Protestant Reformation, when competition again entered and characterized the market for Christian belief. Roman Christianity had to face and engage in competition in the post-Reformation era, but Economic Origins makes clear (in Chapter 8) that the issues faced by the First Millennium Church and the structure established in that era have raised controversy today. The Roman church, despite a competitive environment, maintains the top-down economic organization established in its first thousand years. It remains faced with issues related to provision and maintenance of credibility in its product and the prevention of downstream opportunistic or untoward behavior and "unsanctioned teachings" at the lower levels of the church. There are challenges to Church interpretations of Nicene doctrines as well. Church attendance and membership is declining in most advanced nations with growth observed primarily in the third world. The pedophilia crisis, for one issue only, has challenged credibility in the Church's teaching in a number of countries. Cafeteria Catholics have tended to pick and choose a belief system and claim to remain Roman Catholic. Claims of papal infallibility (established in 1871) have extended to interpretations of the Old and New Testaments and policies regarding issues such as married priests, women priests, and gay rights and marriage. The Church, in some matters throughout history, has had to choose between literal and metaphorical interpretations of the Testaments and policies of the Church. Maintenance of credence, for example, has required evolutionary and metaphorical interpretations of Leviticus (25:44-46) where slavery is sanctioned or Luke (12: 47-48) where the beating of slaves is also given written approval in the New Testament. In Exodus (35:2) death was the sentence for working on the Sabbath. The literal interpretation of Genesis has been strained and twisted to accommodate Galileo and Darwin with the Vatican now admitting that life might well exist on other planets - a position for which Giordano Bruno burned in 1600 under the Roman Inquisition. With Roman Catholics of the developed world in the vanguard of supporting such policies as gay marriage and married or women priests, credibility in the product as established and interpreted in the top-down structure of the Church might suggest some new interpretation of Scripture and policies might emerge on these issues. Economic Origins of Roman Christianity, eschewing normative positions on these matters, concludes that many contemporary problems faced by Roman Christianity are the progeny of developments in the emergence of First Millennium Christianity. It is in that era when the nature of the Christian product was fashioned and agreed to (if not its full interpretation), when apostle-entrepreneurs promulgated the belief structure attached to that product, and when the top-down organization of the Church required policing of the downstream sellers of the doctrine of Roman Christianity evolved. That structure remains to influence policy even in a highly competitive Christian environment today.