According to Charles Poulet (1985), the official split between Eastern and Western Christianity in the fourth century B.C.E. had long been foreshadowed. The Emperor Constantine who made Christianity the official religion of the Roman Empire effectively established what would become the Eastern or Byzantine Catholic or Orthodox Church. There were actually two distinct Christian churches beginning in this era, with one subject to the emperor in Constantinople and the other subject to the Bishop of Rome (later known as the pope). Despite a number of official church councils called at places such as Nicea, Sardica, and Cappadocia, the Eastern and Western Churches were unable to unify.
Earle Cairns (1981) notes that between 313 and 590, the Old Catholic Church, in which each bishop was an equal, became the Roman Catholic Church in which the Bishop of Rome won primacy over other bishops. The structure of the Roman Catholic Church and its canon reflects imperial Rome and use of the liturgy in Latin. In contrast, the Eastern Church, centered in Constantinople, used Greek or local languages for its liturgies and rituals. According to Cairns (1981), the split between East and West was brought about less by political or territorial quarrels than theological disagreements over such issues as the nature of the Trinity, the progression or lack thereof of Father, Christ, and Spirit, issues of celibacy for the priesthood and the treatment of the Eucharistic bread (Fisher, 1999).
In the Western part of the Roman Empire, religious power became more and more centralized in the pope in Rome and other higher officials. The Byzantine East was more democratic with less distinction between clergy and laypeople. Its highest official, the patriarch of Constantinople, was largely a titular head and the East did not recognize the Roman pope's claim to universal authority in the Church. Perhaps most significantly, "by the early Middle Ages,...