Schaff, Philip. History of the Christian Church (The Complete Eight Volumes in One). Amazon Kindle Edition, 2014.
Volume 2, Ante-Nicene Christianity A.D. 100-325, “Chapter 4. Organization and Discipline of the Church” Loc. 13792-14769 (part 2).
§44. Origin of the Episcopate.
Schaff observes that two, instead of one, office of leadership emerged in the second century. We had previously seen the presbyterate, an eldership. In the second century, an episcopate emerged. It has remained with us to the present. “Episcopacy in the full sense of the term requires for its base the idea of a real priesthood and real sacrifice, and an essential distinction between clergy and laity. Divested of these associations, it resolves itself into a mere superintendency” (Schaff 2014, Loc. 13938). Schaff ascribes this development to the end of the apostolic period. In the absence of apostles, bishops took on additional responsibility for doctrine. Some emerged as overseers of other bishops (Schaff 2014, Loc. 123944). Schaff finds this shift beginning in the early second century (Schaff 2014, Loc. 13957). Some others find it as an early development present during the apostolic period. A difficulty which emerges is the use of the words, which is often interchangeable. Identification of individuals and their roles is speculative, at best, as Schaff shows from a number of examples. There are many reasons to see a second century development as a natural oranizational moves (Schaff 2014, Loc. 13998). The distinctions, however, remain vague. Schaff concludes that the episcopacy is a descendant of both the apostolic office and the office of elder (presbyter) and was largely in place by the mid second century (Schaff 2014, Loc. 14018). It did not grow uniformly. Some areas had more bishops, some had few. The office served as one who would unify the church around historic doctrine and practice (Schaff 2014, Loc. 14037). The bishops and deacons would deal with poverty and suffering, caring for the whole body of Christ (Schaff 2014, Loc. 14050).
Schaff cautions against confusing this early episcopacy with later heirarchical customs. In this time period the bishops were not very strictly separate from the presbyters (Schaff 2014, Loc. 14057). That was a later development.
A quick organizational note is in order. Schaff’s work is lengthy and exhaustive. Rather than making an attempt at a quick overview, I will be shifting to summarize smaller portions more closely, as I have with this unit.