Ecclesiastical polity is the operational and governance structure of a church or Christian denomination. It also denotes the ministerial structure of the church and the authority relationships between churches. Polity is closely related to Ecclesiology, the study of doctrine and theology relating to church organization.
Issues of church governance appear in the first chapters of the Acts of the Apostles; the first act recorded after the ascension is the election of Matthias to replace Judas Iscariot. Over the years a system of episcopal polity developed.
During the Protestant Reformation, arguments were made that the New Testament prescribed structures quite different from that of the Roman Catholic Church of the day, and different Protestant bodies used different types of polity. It was during this period that Richard Hooker wrote Of the Laws of Ecclesiastical Polity to defend the polity of the Church of England against the Puritans.
Use as a Term
"Ecclesiastical polity" is used in several closely related senses. Most commonly it refers to the field of church governance in the abstract, but it also can refer to the governance of a particular Christian body. In this sense it is used as a term in civil law. "Polity" is sometimes used as a shorthand for the church governance structure itself.
Types of Polity
Though each church or denomination has its own characteristic structure, there are three general types of polity.
Churches having episcopal polity are governed by bishops. The title bishop comes from the Greek word episkopos, which literally translates into overseer.  In regard to Catholicism, bishops have authority over the diocese, which is both sacramental and political; as well as performing ordinations, confirmations, and consecrations, the bishop supervises the clergy of the diocese and represents the diocese both secularly and in the hierarchy of church governance.
Bishops in this system may be subject to higher ranking bishops (variously called archbishops, metropolitans, and/or patriarchs, depending upon the tradition; see also Bishop for further explanation of the varieties of bishops.) They also meet in councils or synods. These synods, subject to presidency by higher ranking bishops, may govern the dioceses which are represented in the council, though the synod may also be purely advisory.
Note that the presence of the office of "bishop" within a church is not proof of episcopal polity. For example, in Mormonism, the "bishop" occupies the office that in an Anglican church would be occupied by a priest.
Also, episcopal polity is not usually a simple chain of command. Instead, some authority may be held, not only by synods and colleges of bishops, but by lay and clerical councils. Further, patterns of authority are subject to a wide variety of historical rights and honors which may cut across simple lines of authority.
Many Reformed churches, notably those in the Presbyterian and Continental Reformed traditions, are governed by a hierarchy of councils. The lowest level council governs a single local church and is called the session or consistory; its members are called elders. The minister of the church (sometimes referred to as a teaching elder) is a member of and presides over the session; lay representatives (ruling elders or, informally, just elders) are elected by the congregation. The session sends representatives to the next level higher council, called the presbytery or classis. In some Presbyterian churches there are higher level councils (synods and/or general assemblies). Each council has authority over its constituents, and the representatives at each level are expected to use their own judgment. Hence higher level councils act as courts of appeal for church trials and disputes, and it is not uncommon to see rulings and decisions overturned.
Presbyterian polity is, of course, the characteristic governance of Presbyterian churches, and also of churches in the Continental Reformed tradition. Elements of presbyterian polity are also found in other churches. For example, in the Episcopal Church in the United States of America governance by bishops is paralleled by a system of deputies, who are lay and clerical representatives elected by parishes and, at the national level, by the dioceses. Legislation in the general convention requires the separate consent of the bishops and of the deputies.
Members may be sent from the congregation to associations that are sometimes identified with the church bodies formed by Lutherans, Presbyterians, Anglicans, and other non-congregational Protestants. The similarity is deceptive, however, because the congregationalist associations do not exercise control over their members (other than ending their membership in the association). Many congregationalist churches are completely independent in principle. One major exception is Ordination, where even congregationalist churches often invite members of the vicinage or association to ordain their called pastor.
It is a principle of congregationalism that ministers do not govern congregations by themselves. They may preside over the congregation, but it is the congregation which exerts its authority in the end.
Congregational polity is sometimes called "Baptist polity", as it is the characteristic polity of Baptist churches.
Polity, Autonomy, and Ecumenism
Although a church's polity dictates how it is governed and how its ministers figure in that governance, it need not have any implications on relationships between church bodies. The unity of the church is a doctrine central to ecclesiology, but since the divisions between churches presuppose a lack of mutual authority, the internal polity does not directly provide answers on how these divisions have been handled.
For example, among churches with episcopal polity, different theories are expressed:
- In Catholicism the church is viewed as a single polity headed by the pope.
- In Eastern Orthodoxy the various churches retain formal autonomy but are held to be unified by shared doctrine and conciliarity (that is, the authority of councils, such as ecumenical councils, Holy Synods and the former standing council, the Endemusa Synod.)
- In Anglicanism the churches are autonomous, though more than half the membership are organizationally united in the Anglican Communion, which has no powers of governance.
- Catholic Church hierarchy
- Structure and polity of the Seventh-day Adventist Church
- Organizational structure of Jehovah's Witnesses
- Connectionalism (Methodist Polity)
- New Testament Church Government - A Look at the Biblical Eldership