What are the limits of the episcopacy?

St. Basil the Great emphasizes that there should be a bishop for every city. In his letter to Amphilochius, he thanks him for helping in finding a new bishop for the church in Iturea and says, “It is preferable for the leader of the city to be an experienced person, capable of bearing the responsibility of managing every detail, but under the condition that he is a servant of God, not shaming us in anything and not seeking his own interests over the interests of others, so that he may save them.” It is most probable that he is speaking here about the bishop of a major city, as he continues saying, “If the matter was difficult, let us strive to give small cities or towns which were previously episcopal centres, to appropriate leaders, and therefore we ordain a bishop over the major city.”