A Fluid Early Structure, and a Later Rule About Marriage

The clearly defined threefold ministry of bishop, priest, and deacon that Holy Orders confers today was not fully fixed from Christianity's earliest years; New Testament and early patristic sources describe overlapping and locally varying titles and roles, elders and overseers among them, and it took the first several centuries of the church's development for these to settle into the stable, universally recognized three grades ordination now confers. One significant later development, rather than an original apostolic requirement, is mandatory celibacy for parish priests in the Western church, a discipline that developed gradually over the medieval period and was progressively tightened and enforced by a series of church councils and papal decrees rather than being imposed all at once, becoming firmly settled Latin church practice by the high Middle Ages.

Eastern Orthodox and Eastern Catholic practice took a different path on this specific point and preserves it to the present day: a man may be ordained a married priest, though marriage after ordination is not permitted, while bishops in Orthodox practice are drawn only from the celibate or monastic clergy, a rule that produces a genuine and long standing difference in ordinary parish life between Western Catholic practice and the Christian East on a question the earliest church had not settled in either direction.