Catholicism
For many the term usually refers to Christians and churches belonging to the Roman Catholic Church in full communion with the Holy See. For others it refers to the churches of the first millennium, including, besides the Roman Catholic Church, the Eastern Orthodox Church, the Oriental Orthodox Church, and the Assyrian Church of the East. And for others again it refers to “adhering to the catholic faith as it has been inherited from the earliest Christians … seeking to restore the faith and order of the primitive church”, as claimed by the Anglican Communion and other Reformation and post-Reformation churches.
The Catholic claim of continuity is based on, among other factors, Apostolic succession, especially in conjunction with adherence to the Nicene Creed.
In the sense of indicating historical continuity of faith and practice, the term “catholicism” is at times employed to mark a contrast to Protestantism, which tends to look solely to the Bible as interpreted on the principles of the 16th-century Protestant Reformation as its ultimate standard.It was thus used by the Oxford Movement.
This contrast, however, is not so clearcut for Anglican theologians such as Alister McGrath: “Anglicanism is not a ‘middle way’ between Protestantism and Catholicism. For that reason … it is neither Protestant nor Catholic, but combines the strengths of both. Yet historians such as Diarmaid McCulloch [an Anglican] have claimed that the ‘middle way’ developed in England in the late 16th century was between Lutheranism and Calvinism—two quite distinct versions of Protestantism. The ‘middle way’ which resulted was neither Calvinist nor Lutheran—but it was certainly Protestant.”
According to Richard McBrien, Catholicism is distinguished from other forms of Christianity in its particular understanding and commitment to tradition, the sacraments, the mediation between God, communion, and the See of Rome.According to Orthodox leaders like Bishop Kallistos Ware, the Orthodox Church has these things as well, though the primacy of the See of Rome is only honorific, showing non-jurisdictional respect for the Bishop of Rome as the “first among equals” and “Patriarch of the West.” Catholicism, according to McBrien’s paradigm, includes a monastic life, religious orders, a religious appreciation of the arts, a communal understanding of sin and redemption, and missionary activity.

