Why Are the Orthodox Churches Genuine Churches?
How does one counter the Eastern Orthodox belief that it is the one, holy, catholic, and apostolic Church?
As far as we are concerned, following the important document Dominus Jesus on the nature of the Church, published under St. John Paul II, the Orthodox churches are real churches and so are in a true sense "one, holy, catholic, and apostolic" as long as they do not have a deliberate spirit of schism. They enjoy an imperfect communion with the fullness of the Church here below because they lack a visible unity with the See of Peter, which is the guarantor of the visible unity of the Church. But still, on account of their sacramental life and their eucharistic life around their bishops, they are genuine local churches, albeit in an irregular relationship with the universal Church whose union is based upon communion with the See of Peter.