Unity is the categorical imperative of the church. It is not just the church's bene esse, but its esse. In addition to being a theological concept, unity has become a raison d'etre of various structures that the church has established and developed. All of these structures are supposed to serve the end of unity. However, from time to time some of them deviate from their initial purpose and contribute to disunity. This happens because the structures of the church are not a part of its nature and can therefore turn against it. They are like scaffolding, which facilitates the construction and maintenance of a building without actually being part of it. Likewise, ecclesial structures help the church function in accordance with its nature but should not be identified with the church proper. This book considers the evolution of some of these church structures and evaluates their correspondence to their initial rationale. It focuses on particular structures that have developed in the eastern part of the Christian oecumene, such as patriarchates, canonical territory, and autocephaly, all of which are explored in the more general frame of hierarchy and primacy. They were selected because they are most neuralgic in the life of the Orthodox churches today and bear in them the greatest potential to divide.