Branch theory is an ecclesiological proposition that the One, Holy, Catholic, and Apostolic Church includes various different Christian denominations whether in formal communion or not.
Anglican proponents of Anglo-Catholic churchmanship who support the theory include only the Roman Catholic, Eastern Orthodox, Oriental Orthodox, Lutheran, Old Catholic, Moravian, Nestorian and Anglican churches as branches. These church bodies have retained the historic episcopate, one of the four essential things which are required for unity with Anglicans. However, other Anglicans, including those of low, broad and high churchmanship, have "followed the major continental Reformers in their doctrine of the true church, identifiable by the authentic ministry of word and sacrament, in their rejection of the jurisdiction of the pope, and in their alliance with the civil authority ('the magistrate')". The Church of England historically considered itself "Protestant and Reformed" and cooperated with the Continental Reformed Churches, participating in the Synod of Dort in 1618β1619.